| TOC |
|
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This document provides a list of typical Media Control Channel Framework [I‑D.ietf‑mediactrl‑sip‑control‑framework] (Boulton, C., Melanchuk, T., and S. McGlashan, “Media Control Channel Framework,” October 2009.) call flows. It aims at being a simple guide to the use of the interface between Application Servers and MEDIACTRL-based Media Servers, as well as a base reference documentation for both implementors and protocol researchers.
1.
Introduction
2.
Conventions
3.
Terminology
4.
A Practical Approach
4.1.
State Diagrams
5.
Control Channel Establishment
5.1.
COMEDIA Negotiation
5.2.
SYNC
5.3.
K-ALIVE
5.4.
Wrong behaviour
6.
Use-case scenarios and examples
6.1.
Echo Test
6.1.1.
Direct Echo Test
6.1.2.
Echo Test based on Recording
6.2.
Phone Call
6.2.1.
Direct Connection
6.2.2.
Conference-based Approach
6.2.3.
Recording a conversation
6.3.
Conferencing
6.3.1.
Simple Bridging
6.3.2.
Rich Conference Scenario
6.3.3.
Coaching Scenario
6.3.4.
Sidebars
6.3.5.
Floor Control
6.4.
Additional Scenarios
6.4.1.
Voice Mail
6.4.2.
Current Time
6.4.3.
DTMF-driven Conference Manipulation
7.
Media Resource Brokering
7.1.
Publishing Interface
7.2.
Consumer Interface
8.
Security Considerations
9.
Change Summary
10.
Acknowledgements
11.
References
§
Authors' Addresses
| TOC |
This document provides a list of typical MEDIACTRL Media Control Channel Framework [I‑D.ietf‑mediactrl‑sip‑control‑framework] (Boulton, C., Melanchuk, T., and S. McGlashan, “Media Control Channel Framework,” October 2009.) call flows. The motivation for this comes from our implementation experience with the framework and its protocol. This drove us to writing a simple guide to the use of the several interfaces between Application Servers and MEDIACTRL-based Media Servers and a base reference documentation for other implementors and protocol researchers.
Following this spirit, this document covers several aspects of the interaction between Application Servers and Media Servers. However, in the context of this document, the call flows almost always depict the interaction between a single Application Server (which, for the sake of conciseness, is called AS from now on) and a single Media Server (MS). In Section 7 (Media Resource Brokering) some flows involving more entities by means of a Media Resource Broker compliant with [I‑D.ietf‑mediactrl‑mrb] (Boulton, C. and L. Miniero, “Media Resource Brokering,” March 2010.) are presented. To ease the understanding of all the flows (for what concerns both SIP dialogs and CFW transactions), the domains hosting the AS and the MS in all the scenarios are called, respectively, 'as.example.com' and 'ms.example.net'.
In the next paragraphs a brief overview of our implementation approach is described, with particular focus on protocol-related aspects. This involves state diagrams for what concerns both the client side (the AS) and the server side (the MS). Of course, this section is not at all to be considered a mandatory approach to the implementation of the framework. It is only meant to ease the understanding of how the framework works from a practical point of view.
Once done with these preliminary considerations, in the subsequent sections real-life scenarios are faced. In this context, first of all, the establishment of the Control Channel is dealt with: after that, some use case scenarios, involving the most typical multimedia applications, are depicted and described.
It is worth pointing out that this document is not meant in any way to be a self-sustained guide to implementing a MEDIACTRL-compliant framework. The specifications are a mandatory read for all implementors, especially considering that this document by itself follows their guidelines but does not delve into the details of every aspect of the protocol.
| TOC |
In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) and indicate requirement levels for compliant implementations.
Besides, note that due to RFC formatting conventions, this document often splits SIP/SDP and CFW across lines whose content would exceed 72 characters. A backslash character marks where this line folding has taken place. This backslash and its trailing CRLF and whitespace would not appear in the actual protocol contents.
| TOC |
This document makes use of the same terminology as the one that can be found in the referenced documents. The following terms are only a summarization of the most commonly used ones in this context, mostly derived from the terminology used in the related documents:
- Application Server:
- an entity that requests media processing and manipulation from a Media Server; typical examples are Back to Back User Agents (B2BUA) and endpoints requesting manipulation of a third-party's media stream.
- Media Server:
- an entity that performs a service, such as media processing, on behalf of an Application Server; typical provided functions are mixing, announcement, tone detection and generation, and play and record services.
- Control Channel:
- a reliable connection between an Application Server and a Media Server that is used to exchange Framework messages.
| TOC |
In this document we embrace an engineering approach to the description of a number of interesting scenarios that can be realized through the careful orchestration of the Media Control Channel Framework entities, namely the Application Server and the Media Server. We will demonstrate, through detailed call flows, how a variegated bouquet of services (ranging from very simple scenarios to much more complicated ones) can be implemented with the functionality currently offered, within the main MEDIACTRL framework, by the control packages that have been made available to date. The document aims at representing a useful guide for those interested in investigating the inter-operation among MEDIACTRL components, as well as for application developers willing to build advanced services on top of the base infrastructure made available by the framework.
| TOC |
In this section we present an "informal" view of the main MEDIACTRL protocol interactions, in the form of state diagrams. Each diagram is indeed a classical representation of a Mealy automaton, comprising a number of possible protocol states, indicated with rectangular boxes. Transitions between states are indicated through edges, with each edge labeled with a slash-separated pair representing a specific input together with the associated output (a dash in the output position means that, for that particular input, no output is generated from the automaton). Some of the inputs are associated with MEDIACTRL protocol messages arriving at a MEDIACTRL component while it is in a certain state: this is the case of 'CONTROL', 'REPORT' (in its various "flavors" -- pending, terminate, etc.), '200', '202', as well as 'Error'. Further inputs represent triggers arriving at the MEDIACTRL automaton from the upper layer, namely the Application Programming Interface used by programmers while implementing MEDIACTRL-enabled services: such inputs have been indicated with the term 'API' followed by the message that the API itself is triggering (as an example, 'API terminate' is a request to send a 'REPORT' message with a status of 'terminate' to the peering component). Four diagrams are provided, which can be divided in two main categories, associated, respectively, with normal operation of the framework (Figure 1 (Media Server CFW State Diagram) and Figure 2 (Application Server CFW State Diagram)) and with asynchronous event notifications (Figure 3 (Event Notifications)). As to the former category, in Figure 1 (Media Server CFW State Diagram) we embrace the MS perspective, whereas in Figure 2 (Application Server CFW State Diagram) we stand on the AS side. The latter category is dealt with in Figure 3 (Event Notifications), which illustrates how notifications are managed. In particular, the upper part of the figure shows how events are generated, on the MS side, by issuing a CONTROL message addressed to the AS; events are acknowledged by the AS through standard 200 responses. Hence, the behavior of the AS, which mirrors that of the MS, is depicted in the lower part of the picture. Coming back to Figure 1 (Media Server CFW State Diagram), the diagram shows that the MS activates upon reception of CONTROL messages coming from the AS, which typically instruct it about the execution of a specific command, belonging to one of the available control packages. The execution of the received command can either be quick, or require some time. In the former case, right after completing its operation, the MS sends back to the AS a 200 message, which basically acknowledges correct termination of the invoked task. In the latter case, the MS first sends back an interlocutory 202 message, which lets it enter a different state ('202' sent). While in the new state, the MS keeps on performing the invoked task: if such task does not complete in a predefined timeout, the server will update the AS on the other side of the control channel by periodically issuing 'REPORT/update' messages; each such message has to be acknowledged by the AS (through a '200' response). Eventually, when the MS is done with the required service, it sends to the AS a 'REPORT/terminate' message, whose acknowledgment receipt concludes a transaction. Again, the AS behavior, depicted in Figure 2 (Application Server CFW State Diagram), mirrors the above described actions undertaken at the MS side. Figures also show the cases in which transactions cannot be successfully completed due to abnormal conditions, which always trigger the creation and expedition of a specific 'Error' message.
+------------------+ CONTROL/- +------------------+ API 202/202
| Idle/'terminate' |------------>| CONTROL received |---------+
+------------------+ +------------------+ |
^ ^ ^ API 200/200 | | |
| | | | | |
| | +------------------+ | |
| 200/- | API Error/Error | |
| +----------------------------+ |
| |
+-------------+ |
| Waiting for | v
| last 200 |<------------------------+ +------------+
+-------------+ | | '202' sent |
^ | +------------+
| | | |
| +---------------+ |
| API terminate/ API terminate/ |
| REPORT terminate REPORT termnate |
| |
+--------------------+ |
| 'update' confirmed |------+ API update/ |
+--------------------+ | REPORT update |
^ | API update/ |
| | REPORT update |
| v |
| 200/- +---------------+ |
+--------------| 'update' sent |<----------------+
+---------------+
| Figure 1: Media Server CFW State Diagram |
+--------------+ 202/- +--------------+
+-->| CONTROL sent |---------->| 202 received |
| +--------------+ +--------------+
| | | | |
| | | | |
API CONTROL/ | | 200/- | | |
send CONTROL | | | | |
| | | Error/ | |
+------------------+ | | Error | |
| Idle/'terminate' |<-+ | | |
+------------------+<---------+ | |
^ ^ | |
| | REPORT 'terminate'/ | |
| | send 200 | |
| +--------------------------------+ | REPORT 'update'/
| | send 200
| REPORT 'terminate'/ |
| send 200 |
| +-----------+ |
+---------------------| 'update ' |<--------------+
+-----------+
^ |
| | REPORT 'update'/
+------+ send 200
| Figure 2: Application Server CFW State Diagram |
+--------------+
+-->| CONTROL sent |
| +--------------+
| |
| |
API CONTROL/ | | 200/-
send CONTROL | |
| |
+------------------+ |
| Idle/'terminate' |<----+
+------------------+
(Media Server perspective)
+------------------+ CONTROL/- +------------------+
| Idle/'terminate' |------------>| CONTROL received |
+------------------+ +------------------+
^ API 200/200 |
| |
+----------------------------+
(Application Server perspective)
| Figure 3: Event Notifications |
| TOC |
As specified in [I‑D.ietf‑mediactrl‑sip‑control‑framework] (Boulton, C., Melanchuk, T., and S. McGlashan, “Media Control Channel Framework,” October 2009.), the preliminary step to any interaction between an AS and a MS is the establishment of a control channel between the two. As explained in the next subsection, this is accomplished by means of a so-called COMEDIA [RFC4145] (Yon, D. and G. Camarillo, “TCP-Based Media Transport in the Session Description Protocol (SDP),” September 2005.) negotiation. This negotiation allows for a reliable connection to be created between the AS and the MS: it is here that the AS and the MS agree on the transport level protocol to use (TCP/SCTP) and whether any application level security is needed or not (e.g. TLS). For the sake of simplicity, we assume that an unencrypted TCP connection is negotiated between the two involved entities. Once they have connected, a SYNC message sent by the AS to the MS consolidates the control channel. An example of how a keep-alive message is triggered is also presented in the following paragraphs. For the sake of completeness, this section also includes a couple of common mistakes that can occur when dealing with the Control Channel establishment.
AS MS
| |
| INVITE (COMEDIA) |
|------------------------------>|
| 100 (Trying) |
|<------------------------------|
| 200 OK (COMEDIA) |
|<------------------------------|
| ACK |
|------------------------------>|
| |
|==============================>|
| TCP CONNECT (CTRL CHANNEL) |
|==============================>|
| |
| SYNC (Dialog-ID, etc.) |
|+++++++++++++++++++++++++++++>>|
| |--+
| | | Check SYNC
| |<-+
| 200 OK |
|<<+++++++++++++++++++++++++++++|
| |
. .
. .
| Figure 4: Control Channel Establishment |
| TOC |
As a first step, the AS and the MS establish a Control SIP dialog. This is usually originated by the AS itself. The AS generates a SIP INVITE message containing in its SDP body information about the TCP connection it wants to establish with the MS. In the provided example (see Figure 5 (COMEDIA Negotiation: Sequence Diagram) and the attached call flow), the AS wants to actively open a new TCP connection, which on his side will be bound to port 5757. If the request is fine, the MS answers with its own offer, by communicating to the AS the transport address to connect to in order to establish the TCP connection. In the provided example, the MS will listen on port 7575. Once this negotiation is over, the AS can effectively connect to the MS.
The negotiation includes additional attributes, the most important being the 'cfw-id' attribute, since it specifies the Dialog-ID which will be subsequently referred to by both the AS and the MS, as specified in the core framework draft.
Note that the provided example also includes the indication, from both the AS and the MS, of the supported control packages. This is achieved by means of a series of 'ctrl-package' attributes as specified in [I‑D.boulton‑mmusic‑sdp‑control‑package‑attribute] (Boulton, C., “A Session Description Protocol (SDP) Control Package Attribute,” March 2009.). In the example, the AS supports (or is only interested to) two packages: IVR (Interactive Voice Response) and Mixer (Conferencing and Bridging). The MS replies with the list of packages it supports, by adding a dummy example package to the list provided by the AS. It is worth noting that this exchange of information is not meant as a strict or formal negotiation of packages: in case the AS realizes that one or more packages it needs are not supported according to the indications sent by the MS, it may, or may not, choose not to open a control channel with the MS at all, if its application logic leads to such a decision. The actual negotiation of control packages is done subsequenty through the use of the framework SYNC transaction.
AS MS
| |
| 1. INVITE (COMEDIA) |
|------------------------------>|
| 2. 100 (Trying) |
|<------------------------------|
| 3. 200 OK (COMEDIA) |
|<------------------------------|
| 4. ACK |
|------------------------------>|
| |
|==============================>|
| TCP CONNECT (CTRL CHANNEL) |
|==============================>|
| |
. .
. .
| Figure 5: COMEDIA Negotiation: Sequence Diagram |
1. AS -> MS (SIP INVITE)
------------------------
INVITE sip:MediaServer@ms.example.net:5060 SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4:5060;\
branch=z9hG4bK-d8754z-9b07c8201c3aa510-1---d8754z-;rport=5060
Max-Forwards: 70
Contact: <sip:ApplicationServer@1.2.3.4:5060>
To: <sip:MediaServer@ms.example.net:5060>
From: <sip:ApplicationServer@as.example.com:5060>;tag=4354ec63
Call-ID: MDk2YTk1MDU3YmVkZjgzYTQwYmJlNjE5NTA4ZDQ1OGY.
CSeq: 1 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, UPDATE, REGISTER
Content-Type: application/sdp
Content-Length: 263
v=0
o=lminiero 2890844526 2890842807 IN IP4 as.example.com
s=MediaCtrl
c=IN IP4 as.example.com
t=0 0
m=application 5757 TCP cfw
a=connection:new
a=setup:active
a=cfw-id:5feb6486792a
a=ctrl-package:msc-ivr/1.0
a=ctrl-package:msc-mixer/1.0
2. AS <- MS (SIP 100 Trying)
----------------------------
SIP/2.0 100 Trying
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-9b07c8201c3aa510-1---d8754z-;rport=5060
To: <sip:MediaServer@ms.example.net:5060>;tag=499a5b74
From: <sip:ApplicationServer@as.example.com:5060>;tag=4354ec63
Call-ID: MDk2YTk1MDU3YmVkZjgzYTQwYmJlNjE5NTA4ZDQ1OGY.
CSeq: 1 INVITE
Content-Length: 0
3. AS <- MS (SIP 200 OK)
------------------------
SIP/2.0 200 OK
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-9b07c8201c3aa510-1---d8754z-;rport=5060
Contact: <sip:MediaServer@ms.example.net:5060>
To: <sip:MediaServer@ms.example.net:5060>;tag=499a5b74
From: <sip:ApplicationServer@as.example.com:5060>;tag=4354ec63
Call-ID: MDk2YTk1MDU3YmVkZjgzYTQwYmJlNjE5NTA4ZDQ1OGY.
CSeq: 1 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, UPDATE, REGISTER
Content-Type: application/sdp
Content-Length: 296
v=0
o=lminiero 2890844526 2890842808 IN IP4 ms.example.net
s=MediaCtrl
c=IN IP4 ms.example.net
t=0 0
m=application 7575 TCP cfw
a=connection:new
a=setup:passive
a=cfw-id:5feb6486792a
a=ctrl-package:msc-ivr/1.0
a=ctrl-package:msc-example-pkg/1.0
a=ctrl-package:msc-mixer/1.0
4. AS -> MS (SIP ACK)
---------------------
ACK sip:MediaServer@ms.example.net:5060 SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-22940f5f4589701b-1---d8754z-;rport
Max-Forwards: 70
Contact: <sip:ApplicationServer@1.2.3.4:5060>
To: <sip:MediaServer@ms.example.net:5060>;tag=499a5b74
From: <sip:ApplicationServer@as.example.com:5060>;tag=4354ec63
Call-ID: MDk2YTk1MDU3YmVkZjgzYTQwYmJlNjE5NTA4ZDQ1OGY.
CSeq: 1 ACK
Content-Length: 0
| TOC |
Once the AS and the MS have successfully established a TCP connection, an additional step is needed before the control channel can be used. In fact, as seen in the previous subsection, the first interaction between the AS and the MS happens by means of a SIP dialog, which in turns allows for the creation of the TCP connection. This introduces the need for a proper correlation between the above mentioned entities (SIP dialog and TCP connection), so that the MS can be sure the connection came from the AS which requested it. This is accomplished by means of a dedicated framework message called SYNC. This SYNC message makes use of a unique identifier called Dialog-ID to validate the control channel. This identifier, as introduced in the previous paragrah, is meant to be globally unique and as such is properly generated by the caller (the AS in the call flow), and added as an SDP media attribute (cfw-id) to the COMEDIA negotiation in order to make both entities aware of its value:
a=cfw-id:5feb6486792a
^^^^^^^^^^^^
Besides, it offers an additional negotiation mechanism. In fact, the AS uses the SYNC not only to properly correlate as explained before, but also to negotiate with the MS the control packages it is interested in, as well as to agree on a Keep-Alive timer needed by both the AS and the MS to understand if problems on the connection occur. In the provided example (see Figure 6 (SYNC: Sequence Diagram) and the related call flow), the AS sends a SYNC with a Dialog-ID constructed as needed (using the 'cfw-id' attribute from the SIP dialog) and requests access to two control packages, specifically the IVR and the Mixer package (the same packages the AS previously indicated in its SDP as specified in [I‑D.boulton‑mmusic‑sdp‑control‑package‑attribute] (Boulton, C., “A Session Description Protocol (SDP) Control Package Attribute,” March 2009.), with the difference that this time they are reported in the context of a binding negotiation). Besides, it instructs the MS that a 100 seconds timeout is to be used for Keep-Alive messages. The MS validates the request by matching the received Dialog-ID with the SIP dialog values and, assuming it supports the control packages the AS requested access to (and for the sake of this document we assume it does), it answers with a 200 message. Additionally, the MS provides the AS with a list of other unrequested packages it supports (in this case just a dummy package providing testing functionality).
AS MS
. .
. .
| |
| 1. SYNC (Dialog-ID, etc.) |
|+++++++++++++++++++++++++++++>>|
| |--+
| | | Check SYNC
| |<-+
| 2. 200 OK |
|<<+++++++++++++++++++++++++++++|
| |
. .
. .
| Figure 6: SYNC: Sequence Diagram |
1. AS -> MS (CFW SYNC) ---------------------- CFW 6e5e86f95609 SYNC Dialog-ID: 5feb6486792a Keep-Alive: 100 Packages: msc-ivr/1.0,msc-mixer/1.0 2. AS <- MS (CFW 200) --------------------- CFW 6e5e86f95609 200 Keep-Alive: 100 Packages: msc-ivr/1.0,msc-mixer/1.0 Supported: msc-example-pkg/1.0
The framework level transaction identifier is obviously the same in both the request and the response (6e5e86f95609), since the AS needs to be able to match the response to the original request. At this point, the control channel is finally established, and it can be used by the AS to request services from the MS.
| TOC |
The Control Framework provides a mechanism for implementing a keep-alive functionality. Such a mechanism is especially useful whenever any NAT or firewall sits in the path between an AS and a MS. In fact, NATs and firewalls may have timeout values for the TCP connections they handle, which means that, if no traffic is detected on these connections within a specific time, they could be shut down. This could be the case of a Control Channel established between an AS and a MS but not used for some time. For this reason, the Control Framework specifies a dedicated framework message (K-ALIVE) that the AS and MS can make use of in order to generate traffic on the TCP connection and keep it alive.
In the previous section it has been described how a timeout value for the keep alive mechanism is negotiated. Specifically, in the example the AS and the MS agreed on a value of 100 seconds. This is compliant with how NATs and firewalls are usually implemented, since in most cases the timeout value they use before shutting TCP connections down is around 2 minutes. Such value has a strong meaning within the context of this mechanism. In fact, it means that the active role (in this case the AS) has to send a K-ALIVE message before those 100 seconds pass, otherwise the passive role (the MS) will tear down the connection treating it like a timeout. The Control Framework document suggests a more conservative approach towards handling this timeout value, suggesting to trigger the K-ALIVE message before 80% of the negotiated time passes (in this case, 80 seconds). This is exactly the case presented in Figure 7 (K-ALIVE: Sequence Diagram).
AS MS
. .
. .
| |
~80s have +--| |
passed since | | |
last k-alive +->| |
| 1. K-ALIVE |
|+++++++++++++++++++++++++++++>>|
| |--+
| | | Reset the local
| |<-+ keep-alive timer
| 2. 200 OK |
|<<+++++++++++++++++++++++++++++|
Reset the +--| |
local | | |
keep-alive +->| |
timer | |
. .
. .
| Figure 7: K-ALIVE: Sequence Diagram |
After the Control Channel has been established (COMEDIA+SYNC) both the AS and the MS start local keep-alive timers mapped to the negotiated keep alive timeout value (100 seconds). When about 80 seconds have passed since the start of the timer (80% of 100 seconds), the AS sends the MS a framework level K-ALIVE message. As it can be seen in the protocol message dump, the message is very lightweight, since it only includes a single line with no additional header. When the MS receives the K-ALIVE message, it resets its local keep-alive timer and sends a 200 message back as confirmation. As soon as the AS receives the 200 message, it resets its local keep-alive timer as well and the mechanism starts over again.
The actual transaction steps are presented in the next figure.
1. AS -> MS (K-ALIVE) --------------------- CFW 518ba6047880 K-ALIVE 2. AS <- MS (CFW 200) --------------------- CFW 518ba6047880 200
In case the timer expired either in the AS or in the MS (i.e. the K-ALIVE or the 200 arrived after the 100 seconds) the connection and the associated SIP Control Dialog would be torn down by the entity detecting the timeout, thus ending the interaction between the AS and the MS.
| TOC |
This section will briefly address some of those which could represent the most common mistakes when dealing with the establishment of a Control Channel between an AS and a MS. These scenarios are obviously of interest, since they result in the AS and the MS being unable to interact with each other. Specifically, these simple scenarios will be described:
The first scenario is depicted in Figure 8 (SYNC with wrong Dialog-ID: Sequence Diagram).
AS MS
. .
. .
| |
| 1. SYNC (Dialog-ID, etc.) |
|+++++++++++++++++++++++++++++>>|
| |--+
| | | Check SYNC (wrong!)
| |<-+
| 2. 481 |
|<<+++++++++++++++++++++++++++++|
| |
|<-XX- CLOSE TCP CONNECTION -XX-|
| |
| SIP BYE |
|------------------------------>|
| |
. .
. .
| Figure 8: SYNC with wrong Dialog-ID: Sequence Diagram |
The scenario is similar to the one presented in Section 5.2 (SYNC) but with a difference: instead of using the correct, expected, Dialog-ID in the SYNC message (5feb6486792a, the one negotiated via COMEDIA), the AS uses a wrong value (4hrn7490012c). This causes the SYNC transaction to fail. First of all, the MS sends a framework level 481 message. This response, when given in reply to a SYNC message, means that the SIP dialog associated with the provided Dialog-ID (the wrong identifier) does not exist. Besides, the Control Channel must be torn down as a consequence, and so the MS also closes the TCP connection it received the SYNC message from. The AS at this point is supposed to tear down its SIP Control Dialog as well, and so sends a SIP BYE to the MS.
The actual transaction is presented in the next picture.
1. AS -> MS (CFW SYNC with wrong Dialog-ID) ------------------------------------------- CFW 2b4dd8724f27 SYNC Dialog-ID: 4hrn7490012c Keep-Alive: 100 Packages: msc-ivr/1.0,msc-mixer/1.0 2. AS <- MS (CFW 481) --------------------- CFW 2b4dd8724f27 481
The second scenario instead is depicted in Figure 9 (Incorrect first transaction: Sequence Diagram).
AS MS
. .
. .
| |
| 1. CONTROL |
|+++++++++++++++++++++++++++++>>|
| |--+ First transaction
| | | is not a SYNC
| |<-+
| 2. 403 |
|<<+++++++++++++++++++++++++++++|
| |
|<-XX- CLOSE TCP CONNECTION -XX-|
| |
| SIP BYE |
|------------------------------>|
| |
. .
. .
| Figure 9: Incorrect first transaction: Sequence Diagram |
This scenario is another common mistake that could occur when trying to setup a Control Channel. In fact, the Control Framework mandates that the first transaction after the COMEDIA negotiation be a SYNC to conclude the setup. In case the AS, instead of triggering a SYNC message as expected, sends a different message to the MS (in the example, it tries to send an <audit> message addressed to the IVR Control Package), the MS treats it like an error. As a consequence, the MS replies with a framework level 403 message (Forbidden) and, just as before, closes the TCP connection and waits for the related SIP Control Dialog to be torn down.
The actual transaction is presented in the next picture.
1. AS -> MS (CFW CONTROL instead of SYNC)
-----------------------------------------
CFW 101fbbd62c35 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 78
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<audit/>
</mscivr>
2. AS <- MS (CFW 403 Forbidden)
-------------------------------
CFW 101fbbd62c35 403
| TOC |
The following scenarios have been chosen for their common presence in many rich real-time multimedia applications. Each scenario is depicted as a set of call flows, involving both the SIP/SDP signaling (UACs<->AS<->MS) and the Control Channel communication (AS<->MS).
All the examples assume that a Control Channel has already been correctly established and SYNCed between the reference AS and MS. Besides, unless stated otherwise, the same UAC session is referenced in all the above mentioned examples. The UAC session is assumed to have been created as the described Figure 10 (3PCC Sequence Diagram):
UAC AS MS | | | | INVITE (X) | | |------------------>| | | 180 (Ringing) | | |<------------------| | | |--+ | | | | Handle app(X) | | |<-+ | | | INVITE (X) as 3PCC | | |-------------------------->| | | 100 (Trying) | | |<--------------------------| | | |--+ Negotiate media | | | | with UAC and map | | |<-+ tags and labels | | 200 OK | | |<--------------------------| | 200 OK | | |<------------------| | | ACK | | |------------------>| | | | ACK | | |-------------------------->| | | | |<<###########################################>>| | RTP Media Stream(s) flowing | |<<###########################################>>| | | | . . . . . .
| Figure 10: 3PCC Sequence Diagram |
Note well: this is only an example of a possible approach involving a 3PCC negotiation among the UAC, the AS and the MS, and as such is not at all to be considered as the mandatory way or as best common practice either in the presented scenario. [RFC3725] (Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo, “Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP),” April 2004.) provides several different solutions and many details about how 3PCC can be realized, with pros and cons.
The UAC first places a call to a SIP URI the AS is responsible of. The specific URI is not relevant to the examples, since the application logic behind the mapping between a URI and the service it provides is a matter that is important only to the AS: so, a generic 'sip:mediactrlDemo@as.example.com' is used in all the examples, whereas the service this URI is associated with in the AS logic is mapped scenario by scenario to the case under exam. The UAC INVITE is treated as envisaged in [RFC5567] (Melanchuk, T., “An Architectural Framework for Media Server Control,” June 2009.): the INVITE is forwarded by the AS to the MS in a 3PCC fashion, without the SDP provided by the UAC being touched, so to have the session fully negotiated by the MS for what concerns its description. The MS matches the UAC's offer with its own capabilities and provides its answer in a 200 OK. This answer is then forwarded, again without the SDP contents being touched, by the AS to the UAC it is intended for. This way, while the SIP signaling from the UAC is terminated in the AS, all the media would start flowing directly between the UAC and the MS.
As a consequence of this negotiation, one or more media connections are created between the MS and the UAC. They are then addressed, when needed, by the AS and the MS by means of the tags concatenation as specified in [I‑D.ietf‑mediactrl‑sip‑control‑framework] (Boulton, C., Melanchuk, T., and S. McGlashan, “Media Control Channel Framework,” October 2009.). How the identifiers are created and addressed is explained by making use of the sample signaling provided in Figure 11 (3PCC SIP Signaling).
1. UAC -> AS (SIP INVITE)
-------------------------
INVITE sip:mediactrlDemo@as.example.com SIP/2.0
Via: SIP/2.0/UDP 4.3.2.1:5063;rport;branch=z9hG4bK1396873708
From: <sip:lminiero@users.example.com>;tag=1153573888
To: <sip:mediactrlDemo@as.example.com>
Call-ID: 1355333098
CSeq: 20 INVITE
Contact: <sip:lminiero@4.3.2.1:5063>
Content-Type: application/sdp
Max-Forwards: 70
User-Agent: Linphone/2.1.1 (eXosip2/3.0.3)
Subject: Phone call
Expires: 120
Content-Length: 330
v=0
o=lminiero 123456 654321 IN IP4 4.3.2.1
s=A conversation
c=IN IP4 4.3.2.1
t=0 0
m=audio 7078 RTP/AVP 0 3 8 101
a=rtpmap:0 PCMU/8000/1
a=rtpmap:3 GSM/8000/1
a=rtpmap:8 PCMA/8000/1
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-11
m=video 9078 RTP/AVP 98
a=rtpmap:98 H263-1998/90000
a=fmtp:98 CIF=1;QCIF=1
2. UAC <- AS (SIP 180 Ringing)
------------------------------
SIP/2.0 180 Ringing
Via: SIP/2.0/UDP 4.3.2.1:5063;rport=5063; \
branch=z9hG4bK1396873708
Contact: <sip:mediactrlDemo@as.example.com>
To: <sip:mediactrlDemo@as.example.com>;tag=bcd47c32
From: <sip:lminiero@users.example.com>;tag=1153573888
Call-ID: 1355333098
CSeq: 20 INVITE
Content-Length: 0
3. AS -> MS (SIP INVITE)
------------------------
INVITE sip:MediaServer@ms.example.net:5060;transport=UDP SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-8723e421ebc45f6b-1---d8754z-;rport
Max-Forwards: 70
Contact: <sip:ApplicationServer@1.2.3.4:5060>
To: <sip:MediaServer@ms.example.net:5060>
From: <sip:ApplicationServer@as.example.com:5060>;tag=10514b7f
Call-ID: NzI0ZjQ0ZTBlMTEzMGU1ZjVhMjk5NTliMmJmZjE0NDQ.
CSeq: 1 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, UPDATE, REGISTER
Content-Type: application/sdp
Content-Length: 330
v=0
o=lminiero 123456 654321 IN IP4 4.3.2.1
s=A conversation
c=IN IP4 4.3.2.1
t=0 0
m=audio 7078 RTP/AVP 0 3 8 101
a=rtpmap:0 PCMU/8000/1
a=rtpmap:3 GSM/8000/1
a=rtpmap:8 PCMA/8000/1
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-11
m=video 9078 RTP/AVP 98
a=rtpmap:98 H263-1998/90000
a=fmtp:98 CIF=1;QCIF=1
4. AS <- MS (SIP 100 Trying)
----------------------------
SIP/2.0 100 Trying
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-8723e421ebc45f6b-1---d8754z-;rport=5060
To: <sip:MediaServer@ms.example.net:5060>;tag=6a900179
From: <sip:ApplicationServer@as.example.com:5060>;tag=10514b7f
Call-ID: NzI0ZjQ0ZTBlMTEzMGU1ZjVhMjk5NTliMmJmZjE0NDQ.
CSeq: 1 INVITE
Content-Length: 0
5. AS <- MS (SIP 200 OK)
------------------------
SIP/2.0 200 OK
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-8723e421ebc45f6b-1---d8754z-;rport=5060
Contact: <sip:MediaServer@ms.example.net:5060>
To: <sip:MediaServer@ms.example.net:5060>;tag=6a900179
From: <sip:ApplicationServer@as.example.com:5060>;tag=10514b7f
Call-ID: NzI0ZjQ0ZTBlMTEzMGU1ZjVhMjk5NTliMmJmZjE0NDQ.
CSeq: 1 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, UPDATE, REGISTER
Content-Type: application/sdp
Content-Length: 374
v=0
o=lminiero 123456 654322 IN IP4 ms.example.net
s=MediaCtrl
c=IN IP4 ms.example.net
t=0 0
m=audio 63442 RTP/AVP 0 3 8 101
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=label:7eda834
m=video 33468 RTP/AVP 98
a=rtpmap:98 H263-1998/90000
a=fmtp:98 CIF=2
a=label:0132ca2
6. UAC <- AS (SIP 200 OK)
-------------------------
SIP/2.0 200 OK
Via: SIP/2.0/UDP 4.3.2.1:5063;rport=5063; \
branch=z9hG4bK1396873708
Contact: <sip:mediactrlDemo@as.example.com>
To: <sip:mediactrlDemo@as.example.com>;tag=bcd47c32
From: <sip:lminiero@users.example.com>;tag=1153573888
Call-ID: 1355333098
CSeq: 20 INVITE
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, UPDATE, REGISTER
Content-Type: application/sdp
Content-Length: 374
v=0
o=lminiero 123456 654322 IN IP4 ms.example.net
s=MediaCtrl
c=IN IP4 ms.example.net
t=0 0
m=audio 63442 RTP/AVP 0 3 8 101
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=label:7eda834
m=video 33468 RTP/AVP 98
a=rtpmap:98 H263-1998/90000
a=fmtp:98 CIF=2
a=label:0132ca2
7. UAC -> AS (SIP ACK)
----------------------
ACK sip:mediactrlDemo@as.example.com SIP/2.0
Via: SIP/2.0/UDP 4.3.2.1:5063;rport;branch=z9hG4bK1113338059
From: <sip:lminiero@users.example.com>;tag=1153573888
To: <sip:mediactrlDemo@as.example.com>;tag=bcd47c32
Call-ID: 1355333098
CSeq: 20 ACK
Contact: <sip:lminiero@4.3.2.1:5063>
Max-Forwards: 70
User-Agent: Linphone/2.1.1 (eXosip2/3.0.3)
Content-Length: 0
8. AS -> MS (SIP ACK)
---------------------
ACK sip:MediaServer@ms.example.net:5060;transport=UDP SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4:5060; \
branch=z9hG4bK-d8754z-5246003419ccd662-1---d8754z-;rport
Max-Forwards: 70
Contact: <sip:ApplicationServer@1.2.3.4:5060>
To: <sip:MediaServer@ms.example.net:5060;tag=6a900179
From: <sip:ApplicationServer@as.example.com:5060>;tag=10514b7f
Call-ID: NzI0ZjQ0ZTBlMTEzMGU1ZjVhMjk5NTliMmJmZjE0NDQ.
CSeq: 1 ACK
Content-Length: 0
| Figure 11: 3PCC SIP Signaling |
As a result of the 3PCC negotiation depicted in Figure 11 (3PCC SIP Signaling), the following relevant information is retrieved:
From: <sip:ApplicationServer@as.example.com:5060>;tag=10514b7f
^^^^^^^^
To: <sip:MediaServer@ms.example.net:5060>;tag=6a900179
^^^^^^^^
m=audio 63442 RTP/AVP 0 3 8 101
[..]
a=label:7eda834
^^^^^^^
m=video 33468 RTP/AVP 98
[..]
a=label:0132ca2
^^^^^^^
These three identifiers allow the AS and MS to univocally and unambiguously address to each other the connections associated with the related UAC, specifically:
The mapping the AS makes between the UACs<->AS and the AS<->MS SIP dialogs is instead out of scope for this document: we just assume that the AS knows how to address the right connection according to the related session it has with a UAC (e.g. to play an announcement to a specific UAC), which is obviously very important considering the AS is responsible for all the business logic of the multimedia application it provides.
| TOC |
The echo test is the simpliest example scenario that can be achieved by means of a Media Server. It basically consists of a UAC directly or indirectly "talking" to itself. A media perspective of such a scenario is depicted in Figure 12 (Echo Test: Media Perspective).
+-------+ A (RTP) +--------+
| UAC |=========================>| Media |
| A |<=========================| Server |
+-------+ A (RTP) +--------+
| Figure 12: Echo Test: Media Perspective |
From the framework point of view, when the UAC's leg is not attached to anything yet, what appears is described in Figure 13 (Echo Test: UAC Media Leg not attached): since there's no connection involving the UAC yet, the frames it might be sending are discarded, and nothing is sent to it (except for silence, if it is requested to be transmitted).
MS
+------+
UAC | |
o----->>-------x |
o.....<<.......x |
| |
+------+
| Figure 13: Echo Test: UAC Media Leg not attached |
Starting from these considerations, two different approaches to the Echo Test scenario are explored in this document in the following paragraphs:
| TOC |
In the Direct Echo Test approach, the UAC is directly connected to itself. This means that, as depicted in Figure 14 (Echo Test: Direct Echo (self connection)), each frame the MS receives from the UAC is sent back to it in real-time.
MS
+------+
UAC | |
o----->>-------@ |
o-----<<-------@ |
| |
+------+
| Figure 14: Echo Test: Direct Echo (self connection) |
In the framework this can be achieved by means of the conference control package, which is in charge of joining connections and conferences.
A sequence diagram of a potential transaction is depicted in Figure 15 (Self Connection: Framework Transaction):
UAC AS MS
| | |
| | 1. CONTROL (join UAC to itself) |
| |++++++++++++++++++++++++++++++++>>|
| | |--+ self
| | | | join
| | 2. 200 OK |<-+ UAC
| |<<++++++++++++++++++++++++++++++++|
| | |
|<<######################################################>>|
| Now the UAC is echoed back everything |
|<<######################################################>>|
| | |
. . .
. . .
| Figure 15: Self Connection: Framework Transaction |
All the transaction steps have been numbered to ease the understanding. A reference to the above numbered messages is in fact made in the following explanation lines:
The complete transaction, that is the full bodies of the exchanged messages, is provided in the following lines:
1. AS -> MS (CFW CONTROL)
-------------------------
CFW 4fed9bf147e2 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 130
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="10514b7f:6a900179"/>
</mscmixer>
2. AS <- MS (CFW 200 OK)
------------------------
CFW 4fed9bf147e2 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
| TOC |
In the Recording-based Echo Test approach, instead, the UAC is NOT directly connected to itself, but rather indirectly. This means that, as depicted in Figure 16 (Echo Test: Recording involved), each frame the MS receives from the UAC is first recorded: then, when the recording process is ended, the whole recorded frames are played back to the UAC as an announcement.
MS
+------+
UAC | |
o----->>-------+~~~~~> (recording.wav) ~~+
o-----<<-------+ | |
| ^ | v
+--|---+ |
+~~~~~~~~~~~<<~~~~~~~~~~~~+
| Figure 16: Echo Test: Recording involved |
In the framework this can be achieved by means of the IVR control package, which is in charge of both the recording and the playout phases. However, the whole scenario cannot be accomplished in a single transaction; at least two steps, in fact, need to be performed:
This means that two separate transactions need to be invoked. A sequence diagram of a potential multiple transaction is depicted in Figure 17 (Recording-based Echo: Two Framework Transactions):
UAC AS MS | | | | | A1. CONTROL (record for 10s) | | |++++++++++++++++++++++++++++++++>>| | | A2. 202 | | |<<++++++++++++++++++++++++++++++++| prepare & | | |--+ start | | | | the | | A3. REPORT (terminate) |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | A4. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | |<<########################################################| | "This is an echo test: tell something" | |<<########################################################| | | | |########################################################>>| | 10s of audio from the UAC are recorded |--+ save |########################################################>>| | in a | | |<-+ file | | B1. CONTROL (<recordinfo>) | | |<<++++++++++++++++++++++++++++++++| | Use recorded +--| B2. 200 OK | | file to play | |++++++++++++++++++++++++++++++++>>| | announcement +->| | | | C1. CONTROL (play recorded) | | |++++++++++++++++++++++++++++++++>>| | | C2. 202 | | |<<++++++++++++++++++++++++++++++++| prepare & | | |--+ start | | | | the | | C3. REPORT (terminate) |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | C4. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | |<<########################################################| | "Can you hear me? It's me, UAC, talking" | |<<########################################################| | | | | | D1. CONTROL (<promptinfo>) | | |<<++++++++++++++++++++++++++++++++| | | D2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 17: Recording-based Echo: Two Framework Transactions |
The first, obvious difference that comes out when looking at the diagram is that, unlike what happened in the Direct Echo example, the MS does not reply with a 200 message to the CONTROL request originated by the AS. Instead, a 202 provisional message is sent first, followed by a REPORT message. The 202+REPORT(s) mechanism is used whenever the MS wants to tell the AS that the requested operation might take some more time than expected. So, while the <join> operation in the Direct Echo scenario was expected to be fulfilled in a very short time, the IVR request was assumed to last longer instead. A 202 message provides a timeout value and tells the AS to wait a bit, since the preparation of the dialog might not be an immediate task. In this example, the preparation ends before the timeout, and so the transaction is concluded with a 'REPORT terminate', which acts as the 200 message in the previous example. In case the preparation took longer than the timeout, an additional 'REPORT update' would have been sent with a new timeout value, and so on until completion by means of a 'REPORT terminate'.
Notice that the REPORT mechanism depicted is only shown to clarify its behaviour. In fact, the 202+REPORT mechanism is assumed to be involved only when the requested transaction is expected to take a long time (e.g. retrieving a large media file for a prompt from an external server). In this scenario the transaction would be prepared in much less time, and as a consequence would very likely be completed within the context of a simple CONTROL+200 request/response. The following scenarios will only involve 202+REPORTs when they are strictly necessary.
About the dialog itself, notice how the AS-originated CONTROL transactions are terminated as soon as the requested dialogs start: as specified in [I‑D.ietf‑mediactrl‑ivr‑control‑package] (McGlashan, S., Melanchuk, T., and C. Boulton, “An Interactive Voice Response (IVR) Control Package for the Media Control Channel Framework,” February 2010.), the MS makes use of a framework CONTROL message to report the result of the dialog and how it has proceeded. The two transactions (the AS-generated CONTROL request and the MS-generated CONTROL event) are correlated by means of the associated dialog identifier, as it will be clearer from the following lines. As before, all the transaction steps have been numbered to ease the understanding and the following of the subsequent explanation lines. Besides, the two transactions are distinguished by the preceding letter (A,B=recording, C,D=playout).
Now that the first transaction has ended, the AS has the 10s recording of the UAC talking. It can let the UAC hear it by having the MS play it to the MS as an announcement:
As in the previous paragraph, the whole CFW interaction is provided for a more in depth evaluation of the protocol interaction.
A1. AS -> MS (CFW CONTROL, record)
----------------------------------
CFW 796d83aa1ce4 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 265
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt>
<media \
loc="http://www.example.com/demo/echorecord.mpg"/>
</prompt>
<record beep="true" maxtime="10s"/>
</dialog>
</dialogstart>
</mscivr>
A2. AS <- MS (CFW 202)
----------------------
CFW 796d83aa1ce4 202
A3. AS <- MS (CFW REPORT terminate)
-----------------------------------
CFW 796d83aa1ce4 REPORT
Seq: 1
Status: terminate
Timeout: 25
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" \
dialogid="68d6569"/>
</mscivr>
A4. AS -> MS (CFW 200, ACK to 'REPORT terminate')
-------------------------------------------------
CFW 796d83aa1ce4 200
Seq: 1
B1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 0eb1678c0bfc CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 403
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="68d6569">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="9987" termmode="completed"/>
<recordinfo duration="10017" termmode="maxtime">
<mediainfo \
loc="http://www.example.net/recordings/recording-68d6569.mpg" \
type="video/mpeg" size="591872"/>
</recordinfo>
</dialogexit>
</event>
</mscivr>
B2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 0eb1678c0bfc 200
C1. AS -> MS (CFW CONTROL, play)
--------------------------------
CFW 1632eead7e3b CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 241
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt>
<media \
loc="http://www.example.net/recordings/recording-68d6569.mpg"/>
</prompt>
</dialog>
</dialogstart>
</mscivr>
C2. AS <- MS (CFW 202)
----------------------
CFW 1632eead7e3b 202
C3. AS <- MS (CFW REPORT terminate)
-----------------------------------
CFW 1632eead7e3b REPORT
Seq: 1
Status: terminate
Timeout: 25
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" \
dialogid="5f5cb45"/>
</mscivr>
C4. AS -> MS (CFW 200, ACK to 'REPORT terminate')
-------------------------------------------------
CFW 1632eead7e3b 200
Seq: 1
D1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 502a5fd83db8 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 230
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="5f5cb45">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="10366" termmode="completed"/>
</dialogexit>
</event>
</mscivr>
D2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 502a5fd83db8 200
| TOC |
Another scenario that might involve the interaction between an AS and a MS is the classic phone call between two UACs. In fact, even though the most straightforward way to achieve this would be to let the UACs negotiate the session and the media to make use of between themselves, there are cases when the services provided by a MS might prove useful for phone calls as well.
One of these cases is when the two UACs have no common supported codecs: having the two UACs directly negotiate the session would result in a session with no available media. Involving the MS as a transcoder would instead allow the two UACs to communicate anyway. Another interesting case is when the AS (or any other entity the AS is working in behalf of) is interested in manipulating or monitoring the media session between the UACs, e.g. to record the conversation: a similar scenario will be dealt with in Section 6.2.2 (Conference-based Approach).
Before proceeding in looking at how such a scenario might be accomplished by means of the Media Control Channel Framework, it is worth spending a couple of words upon how the SIP signaling involving all the interested parties might look like. In fact in such a scenario a 3PCC approach is absolutely needed. An example is provided in Figure 18 (Phone Call: Example of 3PCC). Again, the presented example is not at all to be considered best common practice when 3PCC is needed in a MediaCtrl-based framework. It is only described in order to let the reader more easily understand what are the requirements on the MS side, and as a consequence which information might be required. [RFC3725] (Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo, “Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP),” April 2004.) provides a much more detailed overview on 3PCC patterns in several use cases. Only an explanatory sequence diagram is provided, without delving into the details of the exchanged SIP messages.
UAC(1) UAC(2) AS MS | | | | | INVITE (offer A) | | |---------------------------------->| | | | 100 Trying | | |<----------------------------------| | | | INVITE (no offer) | | | |<--------------------| | | | 180 Ringing | | | |-------------------->| | | | 180 Ringing | | |<----------------------------------| INVITE (offer A) | | | |-------------------------->| | | | 200 OK (offer A') | | | |<--------------------------| | | | ACK | | | |-------------------------->| | | 200 OK (offer B) | | | |-------------------->| INVITE (offer B) | | | |-------------------------->| | | | 200 OK (offer B') | | | |<--------------------------| | | | ACK | | | ACK (offer B') |-------------------------->| | |<--------------------| | | | 200 OK (offer A') | | |<----------------------------------| | | ACK | | | |---------------------------------->| | | | | | . . . . . . . .
| Figure 18: Phone Call: Example of 3PCC |
In the example, the UAC1 wants to place a phone call to UAC2. To do so, it sends an INVITE to the AS with its offer A. The AS sends an offerless INVITE to UAC2. When the UAC2 responds with a 180, the same message is forwarded by the AS to the UAC1 to notify it the callee is ringing. In the meanwhile, the AS also adds a leg to the MS for UAC1, as explained in the previous sections: to do so it of course makes use of the offer A the UAC1 made. Once the UAC2 accepts the call, by providing its own offer B in the 200, the AS adds a leg for it too to the MS. At this point, the negotiation can be completed by providing the two UACs with the SDP answer negotiated by the MS with them (A' and B' respectively).
This is only one way to deal with the signaling, and shall not absolutely be considered as a mandatory approach of course.
Once the negotiation is over, the two UACs are not in communication yet. In fact, it's up to the AS now to actively trigger the MS into attaching their media streams to each other someway, by referring to the connection identifiers associated with the UACs as explained previously. This document presents two different approaches that might be followed, according to what needs to be accomplished. A generic media perspective of the phone call scenario is depicted in Figure 19 (Phone Call: Media Perspective): the MS is basically in the media path between the two UACs.
+-------+ UAC1 (RTP) +--------+ UAC1 (RTP) +-------+ | UAC |===================>| Media |===================>| UAC | | 1 |<===================| Server |<===================| 2 | +-------+ UAC2 (RTP) +--------+ UAC2 (RTP) +-------+
| Figure 19: Phone Call: Media Perspective |
From the framework point of view, when the UACs' legs are not attached to anything yet, what appears is described in Figure 20 (Phone Call: UAC Media Leg not attached): since there are no connections involving the UACs yet, the frames they might be sending are discarded, and nothing is sent to them (except for silence, if it is requested to be transmitted).
MS
+--------------+
UAC 1 | | UAC 2
o----->>-------x x.......>>.....o
o.....<<.......x x-------<<-----o
| |
+--------------+
| Figure 20: Phone Call: UAC Media Leg not attached |
| TOC |
The Direct Connection is the easiest and more straightforward approach to get the phone call between the two UACs to work. The idea is basically the same as the one in the Direct Echo approach: a <join> directive is used to directly attach one UAC to the other, by exploiting the MS to only deal with the transcoding/adaption of the flowing frames, if needed.
This approach is depicted in Figure 21 (Phone Call: Direct Connection).
MS
+--------------+
UAC 1 | | UAC 2
o----->>-------+~~~>>~~~+------->>-----o
o-----<<-------+~~~<<~~~+-------<<-----o
| |
+--------------+
| Figure 21: Phone Call: Direct Connection |
UAC1 UAC2 AS MS | | | | | | | 1. CONTROL (join UAC1 to UAC2) | | | |++++++++++++++++++++++++++++++++++>>| | | | |--+ join | | | | | UAC1 | | | 2. 200 OK |<-+ UAC2 | | |<<++++++++++++++++++++++++++++++++++| | | | | |<<#######################################################>>| | UAC1 can hear UAC2 talking | |<<#######################################################>>| | | | | | |<<###########################################>>| | | UAC2 can hear UAC1 talking | | |<<###########################################>>| | | | | |<*talking*>| | | . . . . . . . .
| Figure 22: Direct Connection: Framework Transactions |
The framework transactions needed to accomplish this scenario are very trivial and easy to understand. They basically are the same as the ones presented in the Direct Echo Test scenario, with the only difference being in the provided identifiers. In fact, this time the MS is not supposed to attach the UACs' media connections to themselves, but has to join the media connections of two different UACs, i.e. UAC1 and UAC2. This means that, in this transaction, id1 and i2 will have to address the media connections of UAC1 and UAC2. In case of a successful transaction, the MS takes care of forwarding all media coming from UAC1 to UAC2 and vice versa, transparently taking care of any required transcoding steps, if necessary.
1. AS -> MS (CFW CONTROL)
-------------------------
CFW 0600855d24c8 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 130
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="e1e1427c:1c998d22"/>
</mscmixer>
2. AS <- MS (CFW 200 OK)
------------------------
CFW 0600855d24c8 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
Such a simple approach has its drawbacks. For instance, with such an approach recording a conversation between two users might be tricky to accomplish. In fact, since no mixing would be involved, only the single connections (UAC1<->MS and UAC2<->MS) could be recorded. If the AS wants a conversation recording service to be provided anyway, it needs additional business logic on its side. An example of such a use case is provided in Section 6.2.3 (Recording a conversation).
| TOC |
The approach described in Section 6.2.1 (Direct Connection) surely works for a basic phone call, but as already explained might have some drawbacks whenever more advanced features are needed. For intance, you can't record the whole conversation, only the single connections, since no mixing is involved. Besides, even the single task of playing an announcement over the conversation could be complex, especially if the MS does not support implicit mixing over media connections. For this reason, in more advanced cases a different approach might be taken, like the conference-based approach described in this section.
The idea is to make use of a mixing entity in the MS that acts as a bridge between the two UACs: the presence of this entity allows for more customization on what needs to be done on the conversation, like the recording of the conversation that has been provided as an example. The approach is depicted in Figure 23 (Phone Call: Conference-based Approach). The mixing functionality in the MS will be described in more detail in the following section (which deals with many conference-related scenarios), so only some hints will be provided here for a basic comprehension of the approach.
MS
+---------------+
UAC A | | UAC B
o----->>-------+~~>{#}::>+:::::::>>:::::o
o:::::<<:::::::+<::{#}<~~+-------<<-----o
| : |
| : |
+-------:-------+
:
+::::> (conversation.wav)
| Figure 23: Phone Call: Conference-based Approach |
To identify a single sample scenario, let's consider a phone call the AS wants to be recorded.
Figure 24 (Conference-based Approach: Framework Transactions) shows how this could be accomplished in the Media Control Channel Framework: the example, as usual, hides the previous interaction between the UACs and the AS, and instead focuses on the control channel operations and what follows.
UAC1 UAC2 AS MS | | | | | | | A1. CONTROL (create conference) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ create | | | | | conf and | | | A2. 200 OK (conferenceid=Y) |<-+ its ID | | |<<++++++++++++++++++++++++++++++++| | | | | | | | B1. CONTROL (record for 1800s) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ start | | | | | the | | | B2. 200 OK |<-+ dialog | | |<<++++++++++++++++++++++++++++++++| | Recording +--| | | of the mix | | | | has started +->| | | | | C1. CONTROL (join UAC1<->confY) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ join | | | | | UAC1 & | | | C2. 200 OK |<-+ conf Y | | |<<++++++++++++++++++++++++++++++++| | | | | |<<####################################################>>| | Now the UAC1 is mixed in the conference | |<<####################################################>>| | | | | | | | D1. CONTROL (join UAC2<->confY) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ join | | | | | UAC2 & | | | D2. 200 OK |<-+ conf Y | | |<<++++++++++++++++++++++++++++++++| | | | | | |<<########################################>>| | | Now the UAC2 is mixed too | | |<#########################################>>| | | | | |<*talking*>| | | | | | | . . . . . . . .
| Figure 24: Conference-based Approach: Framework Transactions |
The AS makes use of two different packages to accomplish this scenario: the mixer package (to create the mixing entity and join the UACs) and the IVR package (to record what happens in the conference). The framework transaction steps can be described as follows:
A1. AS -> MS (CFW CONTROL, createconference)
--------------------------------------------
CFW 238e1f2946e8 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 395
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<createconference reserved-talkers="2" reserved-listeners="2">
<audio-mixing type="nbest" n="2"/>
<video-switch type="controller"/>
<video-layouts>
<video-layout min-participants='1'>single-view</video-layout>
<video-layout min-participants='2'>dual-view</video-layout>
</video-layouts>
</createconference>
</mscmixer>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 238e1f2946e8 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 151
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Conference created" \
conferenceid="6013f1e"/>
</mscmixer>
B1. AS -> MS (CFW CONTROL, record)
----------------------------------
CFW 515f007c5bd0 CONTROL
Control-Package: msc-ivr
Content-Type: application/msc-ivr+xml
Content-Length: 207
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart conferenceid="6013f1e">
<dialog>
<record beep="false" maxtime="1800s" type="video/mpeg"/>
</dialog>
</dialogstart>
</mscivr>
B2. AS <- MS (CFW 200 OK)
-------------------------
CFW 515f007c5bd0 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="00b29fb"/>
</mscivr>
C1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 0216231b1f16 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="6013f1e"/>
</mscmixer>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 0216231b1f16 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
D1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 140e0f763352 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 124
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="219782951:0b9d3347" id2="6013f1e"/>
</mscmixer>
D2. AS <- MS (CFW 200 OK)
-------------------------
CFW 140e0f763352 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
The recording of the conversation can subsequently be accessed by the AS by waiting for an event notification from the MS: this event, which will be associated with the previously started recording dialog, will contain the URI to the recorded file. Such an event may be triggered either by a natural completion of the dialog (e.g. the dialog has reached its programmed 3 hours) or by any interruption of the dialog itself (e.g. the AS actively requests the recording to be interrupted since the call between the UACs ended).
| TOC |
The previous section described how to take advantage of the conferencing functionality of the mixer package in order to allow the recording of phone calls in a simple way. However, making use of a dedicated mixer just for a phone call might be considered overkill. This section shows how recording a conversation and playing it out subsequently can be accomplished without a mixing entity involved in the call, that is by using the direct connection approach as described in Section 6.2.1 (Direct Connection).
As already explained previously, in case the AS wants to record a phone call between two UACs, the use of just the <join> directive without a mixer forces the AS to just rely on separate recording commands. That is, the AS can only instruct the MS to separately record the media flowing on each media leg: a recording for all the data coming from UAC1, and a different recording for all the data coming from UAC2. In case someone wants to access the whole conversation subsequently, the AS may take at least two different approaches:
It is of course option 2 that is considered in this section. The framework transaction as described in Figure 25 (Phone Call: Playout of a Recorded Conversation) assumes that a recording has already been requested for both UAC1 and UAC2, that the phone call has ended and that the AS has successfully received the URIs to both the recordings from the MS. Such steps are not described again since they would be quite similar to the ones described in Section 6.1.2 (Echo Test based on Recording). As anticipated, the idea is to make use of a properly constructed hidden conference to mix the two separate recordings on the fly and present them to the UAC. It is of course up to the AS to subsequently unjoin the user from the conference and destroy the conference itself once the playout of the recordings ends for any reason.
UAC AS MS | | | | (UAC1 and UAC2 have previously been recorded: the AS has | | the two different recordings available for playout). | | | | | | A1. CONTROL (create conference) | | |++++++++++++++++++++++++++++++++>>| | | |--+ create | | | | conf & | | A2. 200 OK (conferenceid=Y) |<-+ its ID | |<<++++++++++++++++++++++++++++++++| | | | | | B1. CONTROL (join UAC & confY) | | |++++++++++++++++++++++++++++++++>>| | | |--+ join | | | | UAC & | | B2. 200 OK |<-+ conf Y | |<+++++++++++++++++++++++++++++++++| | | | |<<######################################################>>| | UAC is now a passive participant in the conference | |<<######################################################>>| | | | | | C1. CONTROL (play UAC1 on confY) | | |++++++++++++++++++++++++++++++++>>| | | D1. CONTROL (play UAC2 on confY) | | |++++++++++++++++++++++++++++++++>>| | | |--+ Start | | | | both | | | | the | | | |dialogs | | C2. 200 OK |<-+ | |<<++++++++++++++++++++++++++++++++| | | D2. 200 OK | | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | The two recordings are mixed and played together to UAC | |<<########################################################| | | | | | E1. CONTROL (<promptinfo>) | | |<<++++++++++++++++++++++++++++++++| | | E2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | F1. CONTROL (<promptinfo>) | | |<<++++++++++++++++++++++++++++++++| | | F2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 25: Phone Call: Playout of a Recorded Conversation |
The diagram above assumes a recording of both the channels has already taken place. It may have been requested by the AS either shortly before joining UAC1 and UAC2, or shortly after that transaction. Whenever that happened, a recording is assumed to have taken place, and so the AS is supposed to have both the recordings available for playback. Once a new user, UAC, wants to access the recorded conversation, the AS takes care of the presented transactions. The framework transaction steps are only apparently more complicated than the ones presented so far. The only difference, in fact, is that transactions C and D are concurrent, since the recordings must be played together.
A1. AS -> MS (CFW CONTROL, createconference)
--------------------------------------------
CFW 506e039f65bd CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 312
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<createconference reserved-talkers="0" reserved-listeners="1">
<audio-mixing type="controller"/>
<video-switch type="controller"/>
<video-layouts>
<video-layout min-participants='1'>dual-view</video-layout>
</video-layouts>
</createconference>
</mscmixer>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 506e039f65bd 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 151
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Conference created" \
conferenceid="2625069"/>
</mscmixer>
B1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 09202baf0c81 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 214
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="aafaf62d:0eac5236" id2="2625069">
<stream media="audio" direction="recvonly"/>
<stream media="video" direction="recvonly"/>
</join>
</mscmixer>
B2. AS <- MS (CFW 200 OK)
-------------------------
CFW 09202baf0c81 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
C1. AS -> MS (CFW CONTROL, play recording from UAC1)
----------------------------------------------------
CFW 3c2a08be4562 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 229
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart conferenceid="2625069">
<dialog>
<prompt>
<media \
loc="http://www.example.net/recordings/recording-4ca9fc2.mpg"/>
</prompt>
</dialog>
</dialogstart>
</mscivr>
D1. AS -> MS (CFW CONTROL, play recording from UAC2)
----------------------------------------------------
CFW 1c268d810baa CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 229
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart conferenceid="2625069">
<dialog>
<prompt>
<media \
loc="http://www.example.net/recordings/recording-39dfef4.mpg"/>
</prompt>
</dialog>
</dialogstart>
</mscivr>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 1c268d810baa 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" \
dialogid="7a457cc"/>
</mscivr>
D2. AS <- MS (CFW 200 OK)
-------------------------
CFW 3c2a08be4562 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" \
dialogid="1a0c7cf"/>
</mscivr>
E1. AS <- MS (CFW CONTROL event, playout of recorded UAC1 ended)
----------------------------------------------------------------
CFW 77aec0735922 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 230
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="7a457cc">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="10339" termmode="completed"/>
</dialogexit>
</event>
</mscivr>
E2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 77aec0735922 200
F1. AS <- MS (CFW CONTROL event, playout of recorded UAC2 ended)
----------------------------------------------------------------
CFW 62726ace1660 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 230
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="1a0c7cf">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="10342" termmode="completed"/>
</dialogexit>
</event>
</mscivr>
F2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 62726ace1660 200
| TOC |
One of the most important services the MS must be able to provide is mixing. This involves mixing media streams from different sources, and delivering the resulting mix(es) to each interested party, often according to per-user policies, settings and encoding. A typical scenario involving mixing is of course media conferencing. In such a scenario, the media sent by each participant is mixed, and each participant typically receives the overall mix excluding its own contribtion and encoded in the format it negotiated. This example points out in a quite clear way how mixing must take care of the profile of each involved entity.
A media perspective of such a scenario is depicted in Figure 26 (Conference: Media Perspective).
+-------+
| UAC |
| C |
+-------+
" ^
C (RTP) " "
" "
" " A+B (RTP)
v "
+-------+ A (RTP) +--------+ A+C (RTP) +-------+
| UAC |===================>| Media |===================>| UAC |
| A |<===================| Server |<===================| B |
+-------+ B+C (RTP) +--------+ B (RTP) +-------+
| Figure 26: Conference: Media Perspective |
From the framework point of view, when the UACs' legs are not attached to anything yet, what appears is described in Figure 27 (Conference: UAC Legs not attached): since there are no connections involving the UACs yet, the frames they might be sending are discarded, and nothing is sent back to them either (except for silence, if it is requested to be transmitted).
MS
+----------------+
UAC A | | UAC B
o----->>-------x x.......>>.....o
o.....<<.......x x-------<<-----o
| |
| |
| xx |
| |. |
+-------|.-------+
|.
^v
^v
|.
oo
UAC C
| Figure 27: Conference: UAC Legs not attached |
The next subsections will cover several typical scenarios involving mixing and conferencing as a whole, specifically:
All of the above mentioned scenarios depend on the availability of a mixing entity. Such an entity is provided in the Media Control Channel Framework by the conferencing package. This package in fact, besides allowing for the interconnection of media sources as seen in the Direct Echo Test section, enables the creation of abstract connections that can be joined to multiple connections: these abstract connections, called conferences, mix the contribution of each attached connection and feed them accordingly (e.g. a connection with 'sendrecv' property would be able to contribute to the mix and to listen to it, while a connection with a 'recvonly' property would only be able to listen to the overall mix but not to actively contribute to it).
That said, each of the above mentioned scenarios will start more or less in the same way: by the creation of a conference connection (or more than one, as needed in some cases) to be subsequently referred to when it comes to mixing. A typical framework transaction to create a new conference instance in the Media Control Channel Framework is depicted in Figure 28 (Conference: Framework Transactions):
AS MS
| |
| 1. CONTROL (create conference) |
|++++++++++++++++++++++++++++++++>>|
| |--+ create
| | | conf and
| 2. 200 OK (conferenceid=Y) |<-+ its ID
|<<++++++++++++++++++++++++++++++++|
map URI +--| |
X with | | |
conf Y +->| |
| |
. .
. .
| Figure 28: Conference: Framework Transactions |
The call flow is quite straightforward, and can typically be summarized in the following steps:
1. AS -> MS (CFW CONTROL)
-------------------------
CFW 3032e5fb79a1 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 489
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<createconference reserved-talkers="5" reserved-listeners="10">
<audio-mixing type="nbest"/>
<video-switch type="controller"/>
<video-layouts>
<video-layout min-participants='1'>single-view</video-layout>
<video-layout min-participants='2'>quad-view</video-layout>
<video-layout min-participants='5'>multiple-5x1</video-layout>
</video-layouts>
<subscribe>
<active-talkers-sub interval="4"/>
</subscribe>
</createconference>
</mscmixer>
2. AS <- MS (CFW 200)
---------------------
CFW 3032e5fb79a1 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 151
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Conference created" \
conferenceid="6146dd5"/>
</mscmixer>
| TOC |
As already introduced before, the simplest use an AS can make of a conference instance is simple bridging. In this scenario, the conference instance just acts as a bridge for all the participants that are attached to it. The bridge takes care of transcoding, if needed (in general, different participants may make use of different codecs for their streams), echo cancellation (each participant will receive the overall mix excluding its own contribution) and per-participant mixing (each participant may receive different mixed streams, according to what it needs/is allowed to send/receive). This assumes of course that each interested participant must be joined somehow to the bridge in order to indirectly communicate with the other paricipants. From the media perspective, the scenario can be seen as depicted in Figure 29 (Conference: Simple Bridging).
MS
+-----------------+
UAC A | | UAC B
o----->>-------+~~~>{##}:::>+:::::::>>:::::o
o:::::<<:::::::+<:::{##}<~~~+-------<<-----o
| ^: |
| |v |
| ++ |
| |: |
+--------|:-------+
|:
^v
^v
|:
oo
UAC C
| Figure 29: Conference: Simple Bridging |
In the framework, the first step is obviously to create a new conference instance as seen in the introductory section (Figure 28 (Conference: Framework Transactions)). Assuming a conference instance has already been created, bridging participants to it is quite straightforward, and can be accomplished as already seen in the Direct Echo Test Scenario: the only difference here is that each participant is not directly connected to itself (Direct Echo) or another UAC (Direct Connection) but to the bridge instead. Figure 30 (Simple Bridging: Framework Transactions (1)) shows the example of two different UACs joining the same conference: the example, as usual, hides the previous interaction between each of the two UACs and the AS, and instead focuses on what the AS does in order to actually join the participants to the bridge so that they can interact in a conference.
UAC1 UAC2 AS MS | | | | | | | A1. CONTROL (join UAC1 and confY) | | | |++++++++++++++++++++++++++++++++++>>| | | | |--+ join | | | | | UAC1 & | | | A2. 200 OK |<-+ conf Y | | |<<++++++++++++++++++++++++++++++++++| | | | | |<<######################################################>>| | Now UAC1 is mixed in the conference | |<<######################################################>>| | | | | | | | B1. CONTROL (join UAC2 and confY) | | | |++++++++++++++++++++++++++++++++++>>| | | | |--+ join | | | | | UAC2 & | | | B2. 200 OK |<-+ conf Y | | |<<++++++++++++++++++++++++++++++++++| | | | | | |<<###########################################>>| | | Now UAC2 too is mixed in the conference | | |<<###########################################>>| | | | | . . . . . . . .
| Figure 30: Simple Bridging: Framework Transactions (1) |
The framework transaction steps are actually quite trivial to understand, since they're very similar to some previously described scenarios. What the AS does is just joining both UAC1 (id1 in A1) and UAC2 (id1 in B1) to the conference (id2 in both transactions). As a result of these two operations, both UACs are mixed in the conference. Since no <stream> is explicitly provided in any of the transactions, all the media from the UACs (audio/video) are attached to the conference (as long as the conference has been properly configured to support both, of course).
A1. AS -> MS (CFW CONTROL)
--------------------------
CFW 434a95786df8 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 120
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="e1e1427c:1c998d22" id2="6146dd5"/>
</mscmixer>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 434a95786df8 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
B1. AS -> MS (CFW CONTROL)
--------------------------
CFW 5c0cbd372046 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 120
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="6146dd5"/>
</mscmixer>
B2. AS <- MS (CFW 200 OK)
-------------------------
CFW 5c0cbd372046 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
Once one or more participants have been attached to the bridge, their connections and how their media are handled by the bridge can be dynamically manipulated by means of another directive, called <modifyjoin>: a typical use case for this directive is the change of direction of an existing media (e.g. a previously speaking participant is muted, which means its media direction changes from 'sendrecv' to 'recvonly'). Figure 31 (Simple Bridging: Framework Transactions (2)) shows how a framework transaction requesting such a directive might appear.
UAC1 UAC2 AS MS | | | | | | | 1. CONTROL (modifyjoin UAC1) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ modify | | | | | join | | | 2. 200 OK |<-+ settings | | |<<++++++++++++++++++++++++++++++++| | | | | |<<######################################################| | Now UAC1 can receive but not send (recvonly) | |<<######################################################| | | | | . . . . . . . .
| Figure 31: Simple Bridging: Framework Transactions (2) |
The directive used to modify an existing join configuration is <modifyjoin>, and its syntax is exactly the same as the one required in <join> instructions. In fact, the same syntax is used for identifiers (id1/id2). Whenever a modifyjoin is requested and id1 and id2 address one or more joined connections, the AS is requesting a change of the join configuration. In this case, the AS instructs the MS to mute (stream=audio, direction=recvonly) UAC1 (id1=UAC1) in the conference (id2) it has been attached to previously. Any other connection existing between them is left untouched.
It is worth noticing that the <stream> settings are enforced according to both the provided direction AND the id1 and id2 identifiers. For instance, in this example id1 refers to UAC1, while id2 to the conference in the MS. This means that the required modifications have to be applied to the stream specified in the <stream> element of the message, along the direction which goes from 'id1' to 'id2' (as specified in the <modifyjoin> element of the message). In the provided example, the AS wants to mute UAC1 with respect to the conference. To do so, the direction is set to 'recvonly', meaning that, for what concerns id1, the media stream is only to be received. If id1 referred to the conference and id2 to the UAC1, to achieve the same result the direction would have to be set to 'sendonly', meaning 'id1 (the conference) can only send to id2 (UAC1), and no media stream must be received'. Additional settings upon a <stream> (e.g. audio volume, region assignments and so on) follow the same approach, as it is presented in subsequent sections.
1. AS -> MS (CFW CONTROL)
-------------------------
CFW 57f2195875c9 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 182
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="e1e1427c:1c998d22" id2="6146dd5">
<stream media="audio" direction="recvonly"/>
</modifyjoin>
</mscmixer>
2. AS <- MS (CFW 200 OK)
------------------------
CFW 57f2195875c9 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
| TOC |
The previous scenario can be enriched with additional features often found in existing conferencing systems. Typical examples include IVR-based menus (e.g. the DTMF collection for PIN-based conference access), partial and complete recordings in the conference (e.g. for the "state your name" functionality and recording of the whole conference), private and global announcements and so on. All of this can be achieved by means of the functionality provided by the MS. In fact, even if the conferencing and IVR features come from different packages, the AS can interact with both of them and achieve complex results by correlating the effects of different transactions in its application logic.
From the media and framework perspective, a typical rich conferencing scenario can be seen as it is depicted in Figure 32 (Conference: Rich Conference Scenario).
MS
+-------- (announcement.wav)
(conference_recording.wav) <:::::+|
:|
+--------:|--------+
UAC A | :v | UAC B
o----->>-------+~~~>{##}:::>+:::::::>>:::::o
o:::::<<:::::::+<:::{##}<~~~+-------<<-----o
| ^: | |
| |v v |
| ++ * (collect DTMF, get name)
| |: |
+--------|:--------+
|:
^v
^v
|:
oo
UAC C
| Figure 32: Conference: Rich Conference Scenario |
To identify a single sample scenario, let's consider this sequence for a participant joining a conference (which again we assume has already been created):
Figure 33 (Rich Conference Scenario: Framework Transactions) shows a single UAC joining a conference: the example, as usual, hides the previous interaction between the UAC and the AS, and instead focuses on what the AS does to actually interact with the participant and join it to the conference bridge.
UAC AS MS | | | | | A1. CONTROL (request DTMF PIN) | | |++++++++++++++++++++++++++++++++>>| | | |--+ start | | | | the | | A2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | "Please digit the PIN number to join the conference" | |<<########################################################| | | | |########################################################>>| | DTMF digits are collected |--+ get |########################################################>>| | DTMF | | |<-+ digits | | B1. CONTROL (<collectinfo>) | | |<<++++++++++++++++++++++++++++++++| | Compare DTMF +--| B2. 200 OK | | digits with | |++++++++++++++++++++++++++++++++>>| | the PIN number +->| | | | C1. CONTROL (record name) | | |++++++++++++++++++++++++++++++++>>| | | |--+ start | | | | the | | C2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | "Please state your name after the beep" | |<<########################################################| | | | |########################################################>>| | Audio from the UAC is recorded (until timeout or DTMF) |--+ save |########################################################>>| | in a | | |<-+ file | | D1. CONTROL (<recordinfo>) | | |<<++++++++++++++++++++++++++++++++| | Store recorded +--| D2. 200 OK | | file to play | |++++++++++++++++++++++++++++++++>>| | announcement in +->| | | conference later | | | | E1. CONTROL (join UAC & confY) | | |++++++++++++++++++++++++++++++++>>| | | |--+ join | | | | UAC & | | E2. 200 OK |<-+ conf Y | |<+++++++++++++++++++++++++++++++++| | | | |<<######################################################>>| | UAC is now included in the mix of the conference | |<<######################################################>>| | | | | | F1. CONTROL (play name on confY) | | |++++++++++++++++++++++++++++++++>>| | | |--+ start | | | | the | | F2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | Global announcement: "Simon has joined the conference" | |<<########################################################| | | | | | G1. CONTROL (<promptinfo>) | | |<<++++++++++++++++++++++++++++++++| | | G2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 33: Rich Conference Scenario: Framework Transactions |
As it can be deduced from the sequence diagram above, the AS, in its business logic, correlates the results of different transactions, addressed to different packages, to implement a more complex conferencing scenario than the Simple Bridging previously described. The framework transaction steps are the following:
A1. AS -> MS (CFW CONTROL, collect)
-----------------------------------
CFW 50e56b8d65f9 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 311
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt>
<media \
loc="http://www.example.net/prompts/conf-getpin.wav" \
type="audio/x-wav"/>
</prompt>
<collect maxdigits="4" escapekey="*" cleardigitbuffer="true"/>
</dialog>
</dialogstart>
</mscivr>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 50e56b8d65f9 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="06d1bac"/>
</mscivr>
B1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 166d68a76659 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 272
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="06d1bac">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="2312" termmode="completed"/>
<collectinfo dtmf="1234" termmode="match"/>
</dialogexit>
</event>
</mscivr>
B2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 166d68a76659 200
C1. AS -> MS (CFW CONTROL, record)
----------------------------------
CFW 61fd484f196e CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 373
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt>
<media \
loc="http://www.example.net/prompts/conf-rec-name.wav" \
type="audio/x-wav"/>
</prompt>
<record beep="true" maxtime="3s"/>
</dialog>
<stream media="audio" direction="sendonly"/>
<stream media="video" direction="inactive"/>
</dialogstart>
</mscivr>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 61fd484f196e 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="1cf0549"/>
</mscivr>
D1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 3ec13ab96224 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 402
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="1cf0549">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="4988" termmode="completed"/>
<recordinfo duration="3000" termmode="maxtime">
<mediainfo
loc="http://www.example.net/recordings/recording-1cf0549.wav" \
type="audio/x-wav" size="48044"/>
</recordinfo>
</dialogexit>
</event>
</mscivr>
D2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 3ec13ab96224 200
E1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 261d188b63b7 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 120
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="6146dd5"/>
</mscmixer>
E2. AS <- MS (CFW 200 OK)
-------------------------
CFW 261d188b63b7 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
F1. AS -> MS (CFW CONTROL, play)
--------------------------------
CFW 718c30836f38 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 334
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart conferenceid="6c6288c">
<dialog>
<prompt>
<media
loc="http://www.example.net/recordings/recording-1cf0549.wav" \
type="audio/x-wav"/>
<media \
loc="http://www.example.net/prompts/conf-hasjoin.wav" \
type="audio/x-wav"/>
</prompt>
</dialog>
</dialogstart>
</mscivr>
F2. AS <- MS (CFW 200 OK)
-------------------------
CFW 718c30836f38 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="5f4bc7e"/>
</mscivr>
G1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 6485194f622f CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 229
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="5f4bc7e">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="1838" termmode="completed"/>
</dialogexit>
</event>
</mscivr>
G2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 6485194f622f 200
| TOC |
Another typical conference-based use case is the so called Coaching Scenario. In such a scenario, a customer (called A in the following example) places a call to a business call center. An agent (B) is assigned to the customer. Besides, a coach (C), unheard from the customer, provides the agent with whispered suggestions about what to say. This scenario is also described in RFC4597 [RFC4597] (Even, R. and N. Ismail, “Conferencing Scenarios,” August 2006.).
As it can be deduced from the scenario description, per-user policies for media mixing and delivery, i.e who can hear what, are very important. The MS must make sure that only the agent can hear the coach's suggestions. Since this is basically a multiparty call (despite what the customer might be thinking), a mixing entity is needed in order to accomplish the scenario requirements. To summarize:
From the media and framework perspective, such a scenario can be seen as it is depicted in Figure 34 (Coaching Scenario: Media Perspective).
************** +-------+
* A=Customer * | UAC |
* B=Agent * | C |
* C=Coach * +-------+
************** " ^
C (RTP) " "
" "
" " A+B (RTP)
v "
+-------+ A (RTP) +--------+ A+C (RTP) +-------+
| UAC |===================>| Media |===================>| UAC |
| A |<===================| Server |<===================| B |
+-------+ B (RTP) +--------+ B (RTP) +-------+
| Figure 34: Coaching Scenario: Media Perspective |
From the framework point of view, when the mentioned legs are not attached to anything yet, what appears is described in Figure 35 (Coaching Scenario: UAC Legs not attached).
MS
+---------------------------+
| |
UAC A | | UAC B
o.....<<.......x x-------<<-----o
o----->>-------x x.......>>.....o
| |
| |
| |
| |
| xx |
| .| +
+------------v^-------------+
v^
.|
.|
oo
UAC C
| Figure 35: Coaching Scenario: UAC Legs not attached |
What the scenario should look like is instead depicted in Figure 36 (Coaching Scenario: UAC Legs mixed and attached). The customer receives media directly from the agent (recvonly), while all the three involved participants contribute to a hidden conference: of course the customer is not allowed to receive the mixed flows from the conference (sendonly), unlike the agent and the coach which must both be aware of the whole conversation (sendrecv).
MS
+---------------------------+
| |
UAC A | | UAC B
o-----<<-------+----<<----+----<<----+-------<<-----o
o----->>-------+ | +------->>-----o
| | v ^ |
| +~~~~~~~>[##]::::>::::+ |
| v^ |
| || |
| ++ |
| :| +
+------------v^-------------+
v^
:|
:|
oo
UAC C
| Figure 36: Coaching Scenario: UAC Legs mixed and attached |
In the framework this can be achieved by means of the mixer control package, which, as already explained in previous sections, can be exploited whenever mixing and joining entities are needed. The needed steps can be summarized in the following list:
A sequence diagram of such a sequence of transactions is depicted in Figure 37 (Coaching Scenario: Framework Transactions):
A B C AS MS | | | | | | | | | A1. CONTROL (create conference) | | | | |++++++++++++++++++++++++++++++++>>| | | | | |--+ create | | | | | | conf and | | | | A2. 200 OK (conferenceid=Y) |<-+ its ID | | | |<<++++++++++++++++++++++++++++++++| | | | | | | | | | B1. CONTROL (join A-->confY) | | | | |++++++++++++++++++++++++++++++++>>| | | | | |--+ join A | | | | | | & confY | | | | B2. 200 OK |<-+ sendonly | | | |<<++++++++++++++++++++++++++++++++| | | | | | |######################################################>>| | Customer A is mixed (sendonly) in the conference | |######################################################>>| | | | | | | | | | C1. CONTROL (join B<->confY) | | | | |++++++++++++++++++++++++++++++++>>| | | | | |--+ join B | | | | | | & confY | | | | C2. 200 OK |<-+ sendrecv | | | |<<++++++++++++++++++++++++++++++++| | | | | | | |<<#############################################>>| | | Agent B is mixed (sendrecv) in the conference | | |<##############################################>>| | | | | | | | | | D1. CONTROL (join C<->confY) | | | | |++++++++++++++++++++++++++++++++>>| | | | | |--+ join C | | | | | | & confY | | | | D2. 200 OK |<-+ sendrecv | | | |<<++++++++++++++++++++++++++++++++| | | | | | | | |<<######################################>>| | | | Coach C is mixed (sendrecv) as well | | | |<<######################################>>| | | | | | | | | | E1. CONTROL (join A<--B) | | | | |++++++++++++++++++++++++++++++++>>| | | | | |--+ join | | | | | | A & B | | | | E2. 200 OK |<-+ recvonly | | | |<<++++++++++++++++++++++++++++++++| | | | | | |<<######################################################| | Finally, Customer A is joined (recvonly) to Agent B | |<<######################################################| | | | | | . . . . . . . . . .
| Figure 37: Coaching Scenario: Framework Transactions |
A1. AS -> MS (CFW CONTROL, createconference)
--------------------------------------------
CFW 238e1f2946e8 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 329
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<createconference reserved-talkers="3" reserved-listeners="2">
<audio-mixing type="nbest"/>
<video-switch type="controller"/>
<video-layouts>
<video-layout min-participants='1'>dual-view</video-layout>
</video-layouts>
</createconference>
</mscmixer>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 238e1f2946e8 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 151
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Conference created" \
conferenceid="1df080e"/>
</mscmixer>
B1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 2eb141f241b7 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 226
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="1df080e">
<stream media="audio" direction="sendonly"/>
<stream media="video" direction="sendonly"/>
</join>
</mscmixer>
B2. AS <- MS (CFW 200 OK)
-------------------------
CFW 2eb141f241b7 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
C1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 515f007c5bd0 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 122
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="756471213:c52ebf1b" id2="1df080e"/>
</mscmixer>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 515f007c5bd0 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
D1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 0216231b1f16 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 221
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="z9hG4bK19461552:1353807a" id2="1df080e">
<stream media="audio">
<volume controltype="setgain" value="-3"/>
</stream>
</join>
</mscmixer>
D2. AS <- MS (CFW 200 OK)
-------------------------
CFW 0216231b1f16 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
E1. AS -> MS (CFW CONTROL, join)
--------------------------------
CFW 140e0f763352 CONTROL
Control-Package: msc-mixer
Content-Type: application/msc-mixer+xml
Content-Length: 236
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="10514b7f:6a900179" id2="756471213:c52ebf1b">
<stream media="audio" direction="recvonly"/>
<stream media="video" direction="recvonly"/>
</join>
</mscmixer>
E2. AS <- MS (CFW 200 OK)
-------------------------
CFW 140e0f763352 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
| TOC |
Within the context of conferencing, there could be the need for the so-called sidebars, or side conferences. It is the case, for instance, of two or more participants of a conference willing to create a side conference among each others, while still receiving part of the original conference mix in the background. Motivations for such an use case can be found in both [RFC4597] (Even, R. and N. Ismail, “Conferencing Scenarios,” August 2006.) and [RFC5239] (Barnes, M., Boulton, C., and O. Levin, “A Framework for Centralized Conferencing,” June 2008.). It is clear that, in such a case, the side conference is actually a separate conference, which however must be related somehow to the original conference. While the application level relationship is out of scope to this document (this belongs to XCON), the media stream relationship is, and it is consequently interesting to analyse how the mixes could be constructed in order to allow for such a feature making use of the MEDIACTRL specification.
The scenario presented in this section is a conference hosting four different participants: A, B, C and D. All these participants are attached to the conference as active senders and receivers of the existing media streams. At a certain point in time, two participants (B and D) decide to create a sidebar just for them. The sidebar they want to create is constructed so that only audio is involved. Besides, the audio mix of the sidebar must not be made available to the main conference. The mix of the conference, instead, must be attached to the sidebar, but with a lower volume (50%), being just a background to the actual conversation. This would allow both B and D to talk to each other without A and C listening to them, while B and D could still have an overview of what's happening in the main conference.
From the media and framework perspective, such a scenario can be seen as it is depicted in Figure 38 (Sidebars: Media Perspective).
+-------+
| UAC |
| C |
+-------+
" ^
C (RTP) " "
" "
" " A (RTP)
v "
+-------+ A (RTP) +--------+ D+[a+c] (RTP) +-------+
| UAC |===================>| Media |===================>| UAC |
| A |<===================| Server |<===================| B |
+-------+ C (RTP) +--------+ B (RTP) +-------+
^ "
" " B+[a+c] (RTP)
" "
D (RTP) " "
" v
+-------+
| UAC |
| D |
+-------+
| Figure 38: Sidebars: Media Perspective |
From the framework point of view, when all the participants are attached to the main conference, what appears is described in Figure 39 (Sidebars: UAC Legs in main conference).
UAC C
oo
:|
^v
^v
:|
+--------:|-------+
| :| |
| ++ |
UAC A | ^| | UAC B
o----->>-------+~~~>{##}:::>+:::::::>>:::::o
o:::::<<:::::::+<:::{##}<~~~+-------<<-----o
| ^: |
| |v |
| ++ |
| |: |
+--------|:-------+
|:
^v
^v
|:
oo
UAC D
| Figure 39: Sidebars: UAC Legs in main conference |
What the scenario should look like is instead depicted in Figure 40 (Sidebars: UAC Legs mixed and attached). A new mixer is created to host the sidebar. The main mix is then attached as 'sendonly' to the sidebar mix at a lower volume (in order to provide the sidebar users with a background of the main conference). The two interested participants (B and D) have their audio leg detached from the main conference and attached to the sidebar. This detach can be achieved either by actually detaching the leg or by just modifying the status of the leg to inactive. Notice that this only affects the audio stream: the video of the two users is still attached to the main conference, and what happens at the application level may or may not have been changed accordingly (e.g. XCON protocol interactions).
Please notice that the main conference is assumed to be already in place, and the involved participants (A, B, C and D) to be already attached (sendrecv) to it.
UAC C
oo
:|
^v
^v
:|
+--------:|----------------+
| :| |
| ++ |
UAC A | ^| | UAC B
o----->>-------+~~~>{##}:::>{##}:::>+:::::::>>:::::o
o:::::<<:::::::+<:::{##} {##}<~~~+-------<<-----o
| ^: |
| ++ |
| |v |
+----------------|:--------+
|:
^v
^v
|:
oo
UAC D
| Figure 40: Sidebars: UAC Legs mixed and attached |
The situation may subsequently be reverted (e.g. destroying the sidebar conference and reattaching B and D to the main conference mix) in the same way. The AS would just need to unjoin B and D from the hidden conference and change their connection with the main conference back to 'sendrecv'. After unjoining the main mix and the sidebar mix, the sidebar conference could then be destroyed. Anyway, these steps are not described for brevity, considering similar transactions have already been presented.
In the framework the presented scenario can be achieved by means of the mixer control package, which, as already explained in previous sections, can be exploited whenever mixing and joining entities are needed. The needed steps can be summarized in the following list:
Note that for detaching B and D from the main mix, a <modifyjoin> with an 'inactive' status is used, instead of an <unjoin>. The motivation for this is related to how a subsequent rejoining of B and D to the main mix could take place. In fact, by using <modifyjoin> the resources created when first joining B and D to the main mix remain in place, even if marked as unused at the moment. An <unjoin>, instead, would actually free those resources, which could be granted to other participants joining the conference in the meanwhile. This means that, when needing to reattach B and D to the main mix, the MS could not have the resources to do so, resulting in an undesired failure.
A sequence diagram of such a sequence of transactions (where confX is the identifier of the pre-existing main conference mix) is depicted in Figure 41 (Sidebars: Framework Transactions):
B D AS MS | | | | | | | A1. CONTROL (create conference) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ create | | | | | conf and | | | A2. 200 OK (conferenceid=Y) |<-+ its ID | | |<<++++++++++++++++++++++++++++++++| | | | | | | | B1. CONTROL (join confX-->confY) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ join confX | | | | | & confY | | | B2. 200 OK |<-+ sendonly | | |<<++++++++++++++++++++++++++++++++| (50% vol) | | | | | | | C1. CONTROL (modjoin B---confX) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ modjoin B | | | | | & confX | | | C2. 200 OK |<-+ (inactive) | | |<<++++++++++++++++++++++++++++++++| | | | | | | | D1. CONTROL (join B<-->confY) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ join B | | | | | & confY | | | D2. 200 OK |<-+ sendrecv | | |<<++++++++++++++++++++++++++++++++| (audio) | | | | |<<##################################################>>| | Participant B is mixed (sendrecv) in the sidebar | | (A, C and D can't listen to her/him anymore) | |<<##################################################>>| | | | | | | | E1. CONTROL (modjoin D---confX) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ modjoin D | | | | | & confX | | | E2. 200 OK |<-+ (inactive) | | |<<++++++++++++++++++++++++++++++++| | | | | | | | F1. CONTROL (join D<-->confY) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ join D | | | | | & confY | | | F2. 200 OK |<-+ sendrecv | | |<<++++++++++++++++++++++++++++++++| (audio) | | | | | |<<########################################>>| | | D is mixed (sendrecv) in the sidebar too | | | (A and C can't listen to her/him anymore) | | |<<########################################>>| | | | . . . . . .
| Figure 41: Sidebars: Framework Transactions |
A1. AS -> MS (CFW CONTROL, createconference)
--------------------------------------------
CFW 7fdcc2331bef CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 202
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<createconference reserved-talkers="3" reserved-listeners="2">
<audio-mixing mix-type="controller"/>
</createconference>
</mscmixer>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 7fdcc2331bef 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 151
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Conference created" \
conferenceid="519c1b9"/>
</mscmixer>
B1. AS -> MS (CFW CONTROL, join with setgain)
---------------------------------------------
CFW 4e6afb6625e4 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 226
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="2f5ad43" id2="519c1b9">
<stream media="audio" direction="sendonly">
<volume controltype="setgain" value="-5"/>
</stream>
</join>
</mscmixer>
B2. AS <- MS (CFW 200 OK)
-------------------------
CFW 4e6afb6625e4 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
C1. AS -> MS (CFW CONTROL, modifyjoin with inactive status)
-----------------------------------------------------------
CFW 3f2dba317c83 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 193
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="2133178233:18294826" id2="2f5ad43">
<stream media="audio" direction="inactive"/>
</modifyjoin>
</mscmixer>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 3f2dba317c83 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
D1. AS -> MS (CFW CONTROL, join to sidebar)
-------------------------------------------
CFW 2443a8582d1d CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 181
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="2133178233:18294826" id2="519c1b9">
<stream media="audio" direction="sendrecv"/>
</join>
</mscmixer>
D2. AS <- MS (CFW 200 OK)
-------------------------
CFW 2443a8582d1d 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
E1. AS -> MS (CFW CONTROL, modifyjoin with inactive status)
-----------------------------------------------------------
CFW 436c6125628c CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 193
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="1264755310:2beeae5b" id2="2f5ad43">
<stream media="audio" direction="inactive"/>
</modifyjoin>
</mscmixer>
E2. AS <- MS (CFW 200 OK)
-------------------------
CFW 436c6125628c 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
F1. AS -> MS (CFW CONTROL, join to sidebar)
-------------------------------------------
CFW 7b7ed00665dd CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 181
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="1264755310:2beeae5b" id2="519c1b9">
<stream media="audio" direction="sendrecv"/>
</join>
</mscmixer>
F2. AS <- MS (CFW 200 OK)
-------------------------
CFW 7b7ed00665dd 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 125
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join successful"/>
</mscmixer>
| TOC |
As described in [RFC4597] (Even, R. and N. Ismail, “Conferencing Scenarios,” August 2006.), floor control is a feature typically needed and employed in most conference scenarios. In fact, while not a mandatory feature to implement when realizing a conferencing application, it provides additional control on the media streams contributed by participants, thus allowing for moderation of the available resources. The Centralized Conferencing (XCON) framework [RFC5239] (Barnes, M., Boulton, C., and O. Levin, “A Framework for Centralized Conferencing,” June 2008.) suggests the use of the Binary Floor Control Protocol (BFCP) [RFC4582] (Camarillo, G., Ott, J., and K. Drage, “The Binary Floor Control Protocol (BFCP),” November 2006.) to achieve the aforementioned functionality. That said, a combined use of floor control functionality and the tools made available by the MEDIACTRL specification for conferencing would definitely be interesting to investigate. [RFC5567] (Melanchuk, T., “An Architectural Framework for Media Server Control,” June 2009.) introduces two different approaches to integrating floor control with the MEDIACTRL architecture: (i) a topology where the floor control server is co-located with the AS; (ii) a topology where the floor control server is instead co-located with the MS. The two approaches are obviously different with respect to the amount of information the AS and the MS have to deal with, especially when thinking about the logic behind the floor queues and automated decisions. Nevertheless, considering how the Media Control Channel Framework is conceived, the topology (ii) would need a dedicated package (be it an extension or a totally new package) in order to make the MS aware of floor control, and allow it to interact with the interested UAC accordingly. At the time of writing such a package doesn't exist yet, and as a consequence only the topology (i) will be dealt with in the presented scenario.
The scenario will then assume the Floor Control Server (FCS) to be co-located with the AS. This means that all the BFCP requests will be sent by Floor Control Participants (FCP) to the FCS, which will make the AS directly aware of the floor statuses. The scenario for simplicity assumes the involved participants are already aware of all the identifiers needed in order to make BFCP requests for a specific conference. Such information may have been carried according to the COMEDIA negotiation as specified in [RFC4583] (Camarillo, G., “Session Description Protocol (SDP) Format for Binary Floor Control Protocol (BFCP) Streams,” November 2006.). It is important to notice that such information must not reach the MS: this means that, within the context of the 3PCC mechanism that may have been used in order to attach a UAC to the MS, all the BFCP-related information negotiated by the AS and the UAC must be removed before making the negotiation available to the MS, which may be unable to understand the specification. A simplified example of how this could be achieved is presented in Figure 42 (Floor Control: Example of Negotiation).
UAC AS MS | | | | INVITE (SDP: RTP+BFCP) | | |-------------------------------->| | | | INVITE (SDP: RTP) | | |-------------------------------->| | | 200 (SDP: RTP'+labels) | | |<--------------------------------| | match +--| | | floors | | | | & labels +->| | | | | | 200 (SDP: RTP'+BFCP'+labels) | | |<--------------------------------| | | ACK | | |-------------------------------->| | | | ACK | | |-------------------------------->| | | | |<<###################### RTP MEDIA STREAMS ######################>>| | | | |<<******** BFCP CHANNEL *******>>| | | | | . . . . . .
| Figure 42: Floor Control: Example of Negotiation |
From the media and framework perspective, such a scenario doesn't differ much from the already presented conferencing scenarios. It is more interesting to focus on the chosen topology for the scenario, which can seen as it is depicted in Figure 43 (Floor Control: Overall Perspective).
+-------+ +--------+ +-------+
| UAC | | AS | | UAC |
| (FCP) |<****** BFCP ******>| (FCS) |<****** BFCP *******>| (FCC) |
+-------+ +--------+ +-------+
^ ^
| |
| CFW |
| |
| v
| +--------+
+----------RTP---------->| MS |
+--------+
| Figure 43: Floor Control: Overall Perspective |
The AS, besides mantaining the already known SIP signaling among the involved parties, also acts as FCS for the participants in the conferences it is responsible of. In the scenario, two Floor Control Participants are involved: a basic Participant (FCP) and a Chair (FCC).
In the framework this can be achieved by means of the mixer control package, which, as already explained in previous sections, can be exploited whenever mixing and joining entities are needed. Assuming the conference has already been created, the participant has already been attached (recvonly) to it, and that the participant is aware of the involved BFCP identifiers, the needed steps can be summarized in the following list:
A sequence diagram of such a sequence of transactions (also involving the BFCP message flow at a higher level) is depicted in Figure 44 (Floor Control: Framework Transactions):
UAC1 UAC2 AS (FCP) (FCC) (FCS) MS | | | | |<<####################################################| | UAC1 is muted (recvonly stream) in the conference | |<<####################################################| | | | | | | FloorQuery | | |*******>>| | | | |--+ handle | | | | | subscription | | | |<-+ | | | FloorStatus | | |<<*******| | | | | | | FloorRequest | | |*****************>>| | | | |--+ handle | | | | | request | | Pending |<-+ (queue) | |<<*****************| | | | | | | | FloorStatus | | |<<*******| | | | | | | | ChairAction (ACCEPT) | | |*******>>| | | | ChairActionAck | | |<<*******| | | | |--+ handle | | | | | decision | | | |<-+ (queue) | | Accepted | | |<<*****************| | | | FloorStatus | | |<<*******| | | | | | | | |--+ queue | | | | | grants | | | |<-+ floor | | | | | | | | 1. CONTROL (modjoin UAC<->conf) | | | |++++++++++++++++++++++++++++++++>>| | | | |--+ modjoin | | | | | UAC & conf | | | 2. 200 OK |<-+ (sendrecv) | | |<<++++++++++++++++++++++++++++++++| | | | | |<<##################################################>>| | UAC1 is now unmuted (sendrecv) in the conference | | and can speak contributing to the mix | |<<##################################################>>| | | | | | Granted | | |<<*****************| | | | FloorStatus | | |<<*******| | | | | | . . . . . .
| Figure 44: Floor Control: Framework Transactions |
As it can easily be evinced from the above diagram, the complex interaction at the BFCP level only results in a single transaction at the MEDIACTRL level. In fact, the purpose of the BFCP transactions is to moderate access to the audio resource, which means providing the event trigger to MEDIACTRL-based conference manipulation transactions. Before being granted the floor, the FCP UAC is excluded from the conference mix at the MEDIACTRL level (recvonly). As soon as the floor has been granted, the FCP UAC is included in the mix. In MEDIACTRL words:
1. AS -> MS (CFW CONTROL)
-------------------------
CFW gh67ffg56w21 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 182
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="e1e1427c:1c998d22" id2="cf45ee2">
<stream media="audio" direction="sendrecv"/>
</modifyjoin>
</mscmixer>
2. AS <- MS (CFW 200 OK)
------------------------
CFW gh67ffg56w21 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
| TOC |
This section includes additional scenarios that can be of interest when dealing with AS<->MS flows. The aim of the following subsections is to present the use of peculiar features provided by the IVR package, specifically variable announcements, VCR prompts, parallel playback, recurring dialogs and custom grammars. To describe how call flows involving such features might happen, three sample scenarios have been chosen:
| TOC |
An application that typically makes use of the services an MS can provide is Voice Mail. In fact, while it is clear that many of its features are part of the application logic (e.g. the mapping of a URI with a specific user's voice mailbox, the list of messages and their properties, and so on), the actual media work is accomplished through the MS. Features needed by a VoiceMail application include the ability to record a stream and play it back anytime later, give verbose announcements regarding the status of the application, control the playout of recorded messages by means of VCR controls and so on, all features which are supported by the MS through the IVR package.
Without delving into the details of a full VoiceMail application and all its possible use cases, this section will cover a specific scenario, trying to deal with as many interactions as possible that may happen between the AS and the MS in such a context. The covered scenario, depicted as a sequence diagram in Figure 45 (Voice Mail: Framework Transactions), will be the following:
This is a quite oversimplified scenario, considering it doesn't even allow the UAC to delete old messages or organize them, but just to choose which received message to play. Nevertheless, it gives us the chance to deal with variable announcements and VCR controls, two typical features a Voice Mail application would almost always take advantage of. Besides, other features a Voice Mail application would rely upon (e.g. recording streams, event driven IVR menus and so on) have aready been introduced in previous sections, and so representing them would be redundant. This means the presented call flows assume that some messages have already been recorded, and that they are available at reachable locations. The example also assumes that the AS has placed the recordings in its own storage facilities, considering it is not safe to rely upon the internal MS storage which is likely to be temporary.
UAC AS MS | | | | | A1. CONTROL (play variables and | | | collect the user's choice) | | |++++++++++++++++++++++++++++++++>>| | | | prepare & | | |--+ start | | | | the | | A2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | "You have five messages ..." | |<<########################################################| | | | | | B1. CONTROL (<collectinfo>) | | |<<++++++++++++++++++++++++++++++++| | | B2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | | | C1. CONTROL (VCR for chosen msg) | | |++++++++++++++++++++++++++++++++>>| | | | prepare & | | |--+ start | | | | the | | C2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | "Hi there, I tried to call you but..." |--+ |<<########################################################| | handle | | | | VCR- |########################################################>>| | driven | The UAC controls the playout using DTMF | | (DTMF) |########################################################>>| |playout | | |<-+ | | D1. CONTROL (<dtmfnotify>) | | |<<++++++++++++++++++++++++++++++++| | | D2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . (other events are received in the meanwhile) | . . . | | E1. CONTROL (<controlinfo>) | | |<<++++++++++++++++++++++++++++++++| | | E2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 45: Voice Mail: Framework Transactions |
The framework transaction steps are described in the following:
A1. AS -> MS (CFW CONTROL, play and collect)
--------------------------------------------
CFW 2f931de22820 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 429
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt>
<media \
loc="http://www.example.net/prompts/vm-youhave.wav" \
type="audio/x-wav"/>
<variable value="5" type="digits"/>
<media \
loc="http://www.example.net/prompts/vm-messages.wav" \
type="audio/x-wav"/>
</prompt>
<collect maxdigits="1" escapekey="*" \
cleardigitbuffer="true"/>
</dialog>
</dialogstart>
</mscivr>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 2f931de22820 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="5db01f4"/>
</mscivr>
B1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 7c97adc41b3e CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 270
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="5db01f4">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="11713" termmode="completed"/>
<collectinfo dtmf="1" termmode="match"/>
</dialogexit>
</event>
</mscivr>
B2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 7c97adc41b3e 200
C1. AS -> MS (CFW CONTROL, VCR)
-------------------------------
CFW 3140c24614bb CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 423
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="10514b7f:6a900179">
<dialog>
<prompt bargein="false">
<media \
loc="http://www.example.com/messages/recording-4ca9fc2.mpg"/>
</prompt>
<control gotostartkey="1" gotoendkey="3" \
ffkey="6" rwkey="4" pausekey="7" resumekey="9" \
volupkey="#" voldnkey="*"/>
</dialog>
<subscribe>
<dtmfsub matchmode="control"/>
</subscribe>
</dialogstart>
</mscivr>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 3140c24614bb 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="3e936e0"/>
</mscivr>
D1. AS <- MS (CFW CONTROL event, dtmfnotify)
--------------------------------------------
CFW 361840da0581 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 179
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="3e936e0">
<dtmfnotify matchmode="control" dtmf="6" \
timestamp="2008-12-16T12.58:36Z"/>
</event>
</mscivr>
D2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 361840da0581 200
[..] The other VCR DTMF notifications are skipped for brevity [..]
E1. AS <- MS (CFW CONTROL event, dialogexit)
--------------------------------------------
CFW 3ffab81c21e9 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 485
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="3e936e0">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="10270" termmode="completed"/>
<controlinfo>
<controlmatch dtmf="6" timestamp="2008-12-16T12.58:36Z"/>
<controlmatch dtmf="4" timestamp="2008-12-16T12.58:37Z"/>
<controlmatch dtmf="7" timestamp="2008-12-16T12.58:38Z"/>
<controlmatch dtmf="9" timestamp="2008-12-16T12.58:40Z"/>
</controlinfo>
</dialogexit>
</event>
</mscivr>
E2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 3ffab81c21e9 200
| TOC |
An interesting scenario to realize with the help of the MS provided features is what is typically called 'Current Time'. A UAC calls a URI, which presents the caller with the current date and time. As it can easily be deduced by the very nature of the application, variable announcements play an important role in this scenario. In fact, rather than having the AS build different framework messages according to the current time to build an announcement, it is much easier to rely upon the variable announcements mechanism provided by the IVR package, which includes ways to deal with dates and times in several fashions.
To make the scenario more interesting and have it cover more functionality, the application is also assumed to have a background music played during the announcement. Considering that most of the announcements will be variable, a means is needed to have more streams played in parallel on the same connection. This can be achieved in two different ways:
The first approach assumes the available MS implements implicit mixing, which may or may not be supported, since it's a recommended feature but not a mandatory one. The second approach instead assumes the MS implements support for more streams of the same media type (in this case audio) in the same dialog, which, exactly as implicit mixing, is not to be given for granted. Considering the first approach is quite straightforward to understand, the presented scenario makes use of the second one, and assumes the available MS supports parallel playback of more audio tracks within the context of the same dialog.
That said, the covered scenario, depicted as a sequence diagram in Figure 46 (Current Time: Framework Transactions), will be the following:
UAC AS MS | | | | | A1. CONTROL (play variables) | | |++++++++++++++++++++++++++++++++>>| | | | prepare & | | |--+ start | | | | the | | A2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++| | | | |<<########################################################| | "16th of december 2008, 5:31 PM..." | |<<########################################################| | | | | | B1. CONTROL (<promptinfo>) | | |<<++++++++++++++++++++++++++++++++| | | B2. 200 OK | | |++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 46: Current Time: Framework Transactions |
The framework transaction steps are described in the following:
A1. AS -> MS (CFW CONTROL, play)
--------------------------------
CFW 0c7680191bd2 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 506
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="21c8e07b:055a893f">
<dialog>
<prompt bargein="true">
<par endsync="last">
<seq>
<media loc="http://www.example.com/day-2.wav"/>
<variable value="2008-12-16" type="date" format="ymd"/>
<variable value="17:31" type="time" format="t12"/>
</seq>
<media loc="http://www.example.com/music.wav" \
soundLevel="50%"/>
<media loc="http://www.example.com/clock.mpg"/>
</par>
</prompt>
</dialog>
</dialogstart>
</mscivr>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 0c7680191bd2 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="415719e"/>
</mscivr>
B1. AS <- MS (CFW CONTROL event)
--------------------------------
CFW 4481ca0c4fca CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 229
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="5db01f4">
<dialogexit status="1" reason="Dialog successfully completed">
<promptinfo duration="8046" termmode="completed"/>
</dialogexit>
</event>
</mscivr>
B2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 4481ca0c4fca 200
| TOC |
To complete the scenarios presented in Section 6.3 (Conferencing), this section deals with how the AS can make use of the MS in order to detect DTMF tones from conference participants, and take actions on the conference accordingly. A typical example is when participants in a conference are provided with specific codes to:
and so on. To achieve all this, the simpliest thing an AS can do is to prepare a recurring DTMF collection for each participant with specific grammars to match. In case the collected tones match the grammar, the MS would notify them to the AS, and start the collection again. Upon receival of <collectinfo> events, the AS would in turn originate the proper related request, e.g. a <modifyjoin> on the participant's stream with the conference. This is made possible by three features provided by the IVR package:
The first allows for recurring instances of the same dialog without the need of additional requests upon completion of the dialog itself. In fact, the 'repeatCount' attribute indicates how many times the dialog has to be repeated: when the attribute has the value 0, it means that the dialog has to be repeated indefinitely, meaning that it's up to the AS to destroy it by means of a <dialogterminate> request when the dialog isn't needed anymore. The second, instead, allows the AS to subscribe to events related to the IVR package without waiting for the dialog to end, e.g. matching DTMF collections in this case. The last, finally, allows for custom matching grammars to be specified: this way, only a subset of the possible DTMF strings can be specified, so that only the matches the AS is interested in are reported. Different grammars other than SRGS may be supported by the MS, which achieve the same result: anyway, this document will only describe the use of an SRGS grammar, since support for SRGS is mandated in the IVR package specification.
To identify a single sample scenario, we assume a participant has already successfully joined a conference, e.g. as detailed in Figure 33 (Rich Conference Scenario: Framework Transactions). Besides, we assume the following codes are to be provided within the conference to participants in order to let them take advantage of advanced features:
This means that six different codes are supported, and are to be matched in the requested DTMF collection. All other codes are collected by the MS, but discarded, and no event is triggered to the AS. Considering all the codes have the '*' (star) DTMF code in common, the following is an example of an SRGS grammar that may be used in the request by the AS:
<grammar mode="dtmf" version="1.0" \
xmlns="http://www.w3.org/2001/06/grammar">
<rule id="digit">
<one-of>
<item>0</item>
<item>1</item>
<item>3</item>
<item>6</item>
<item>7</item>
<item>9</item>
</one-of>
</rule>
<rule id="action" scope="public">
<item>
*
<item><ruleref uri="#digit"/></item>
</item>
</rule>
</grammar>
As it can be deduced by looking at the grammar, the presented SRGS XML code specifies exactly the requirements for the collections to match: the rule is to match any string which has a star ('*') followed by just one of any supported digit (0, 1, 3, 6, 7, 9). Such grammar, as stated in the IVR package specification, may be provided either inline in the request itself or referenced externally by means of the 'src' attribute. In the scenario example, we'll put it inline, but an external reference to the same document would achieve exactly the same result.
Figure 47 (DTMF-driven Conference Manipulation: Framework Transactions) shows how the AS might request the recurring collection for a UAC: as already anticipated before, the example assumes the UAC is already a participant in the conference.
UAC AS MS | | | | | A1. CONTROL (recurring collection) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ start | | | | the | | A2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++++++| | | | |########################################################>>| | Recurring DTMF digit collection starts |--+ get |########################################################>>| | DTMF | | |<-+ digits | | B1. CONTROL (dtmfinfo=*1) | | |<<++++++++++++++++++++++++++++++++++++| | | B2. 200 OK |--+ get | |++++++++++++++++++++++++++++++++++++>>| | DTMF | | |<-+ ditigs | | C1. CONTROL (modifyjoin UAC1-->conf) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ modify | | | | UAC | | C2. 200 OK |<-+ volume | |<<++++++++++++++++++++++++++++++++++++| | | | |########################################################>>| | Volume of UAC in conference is lowered | |########################################################>>| | | | | | D1. CONTROL (dtmfinfo=*9) | | |<<++++++++++++++++++++++++++++++++++++| | | D2. 200 OK |--+ get | |++++++++++++++++++++++++++++++++++++>>| | DTMF | | |<-+ ditigs | | E1. CONTROL (modifyjoin UAC1<--conf) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ modify | | | | conf | | E2. 200 OK |<-+ volume | |<<++++++++++++++++++++++++++++++++++++| | | | |<<########################################################| | Now UAC can hear the conference mix at a higher volume | |<<########################################################| | | | | | F1. CONTROL (dtmfinfo=*6) | | |<<++++++++++++++++++++++++++++++++++++| | | F2. 200 OK |--+ get | |++++++++++++++++++++++++++++++++++++>>| | DTMF | | |<-+ ditigs | | G1. CONTROL (modifyjoin UAC1-->conf) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ mute | | | | UAC in | | G2. 200 OK |<-+ conf | |<<++++++++++++++++++++++++++++++++++++| | | | |########################################################>>| | UAC is now muted in the conference | |########################################################>>| | | | | | H1. CONTROL (dtmfinfo=*0) | | |<<++++++++++++++++++++++++++++++++++++| | | H2. 200 OK |--+ get | |++++++++++++++++++++++++++++++++++++>>| | DTMF | | |<-+ ditigs | | I1. CONTROL (destroy DTMF dialog) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ delete | | | | the | | I2. 200 OK |<-+ dialog | |<<++++++++++++++++++++++++++++++++++++| (DTMF | | |collection | | | stops) | | J1. CONTROL (dialogexit) | | |<<++++++++++++++++++++++++++++++++++++| | | J2. 200 OK | | |++++++++++++++++++++++++++++++++++++>>| | | | |########################################################>>| | No more tones from UAC are collected | |########################################################>>| | | | | | K1. CONTROL (unjoin UAC1<-X->conf) | | |++++++++++++++++++++++++++++++++++++>>| | | |--+ unjoin | | | | UAC & | | K2. 200 OK |<-+ conf | |<<++++++++++++++++++++++++++++++++++++| | | | | | L1. CONTROL (notify-unjoin) | | |<<++++++++++++++++++++++++++++++++++++| | | L2. 200 OK | | |++++++++++++++++++++++++++++++++++++>>| | | | . . . . . .
| Figure 47: DTMF-driven Conference Manipulation: Framework Transactions |
As it can be deduced from the sequence diagram above, the AS, in its business logic, correlates the results of different transactions, addressed to different packages, to implement a more complex conferencing scenario: in fact, 'dtmfnotify' events are used to take actions according to the purpose the DTMF codes are meant for. The framework transaction steps are the following:
A1. AS -> MS (CFW CONTROL, recurring collect with grammar)
----------------------------------------------------------
CFW 238e1f2946e8 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 809
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogstart connectionid="14849028:37fc2523">
<dialog repeatCount="0">
<collect maxdigits="2" termchar="A" escapekey="#">
<grammar>
<grammar version="1.0" mode="dtmf" \
xmlns="http://www.w3.org/2001/06/grammar">
<rule id="digit">
<one-of>
<item>0</item>
<item>1</item>
<item>3</item>
<item>6</item>
<item>7</item>
<item>9</item>
</one-of>
</rule>
<rule id="action" scope="public">
<example>*3</example>
<one-of>
<item>
*
<ruleref uri="#digit"/>
</item>
</one-of>
</rule>
</grammar>
</grammar>
</collect>
</dialog>
<subscribe>
<dtmfsub matchmode="collect"/>
</subscribe>
</dialogstart>
</mscivr>
A2. AS <- MS (CFW 200 OK)
-------------------------
CFW 238e1f2946e8 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 137
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog started" dialogid="01d1b38"/>
</mscivr>
B1. AS <- MS (CFW CONTROL dtmfnotify event)
-------------------------------------------
CFW 1dd62e043c00 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 180
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="01d1b38">
<dtmfnotify matchmode="collect" dtmf="*1" \
timestamp="2008-12-17T17:20:53Z"/>
</event>
</mscivr>
B2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 1dd62e043c00 200
C1. AS -> MS (CFW CONTROL, modifyjoin with setgain)
---------------------------------------------------
CFW 0216231b1f16 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 290
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="873975758:a5105056" id2="54b4ab3">
<stream media="audio" direction="sendonly">
<volume controltype="setgain" value="-3"/>
</stream>
<stream media="audio" direction="recvonly"/>
</modifyjoin>
</mscmixer>
C2. AS <- MS (CFW 200 OK)
-------------------------
CFW 0216231b1f16 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
D1. AS <- MS (CFW CONTROL dtmfnotify event)
-------------------------------------------
CFW 4d674b3e0862 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 180
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="01d1b38">
<dtmfnotify matchmode="collect" dtmf="*9" \
timestamp="2008-12-17T17:20:57Z"/>
</event>
</mscivr>
D2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 4d674b3e0862 200
E1. AS -> MS (CFW CONTROL, modifyjoin with setgain)
---------------------------------------------------
CFW 140e0f763352 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 292
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="873975758:a5105056" id2="54b4ab3">
<stream media="audio" direction="recvonly">
<volume controltype="setgain" value="+3"/>
</stream>
<stream media="audio" direction="sendonly"/>
</modifyjoin>
</mscmixer>
E2. AS <- MS (CFW 200 OK)
-------------------------
CFW 140e0f763352 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
F1. AS <- MS (CFW CONTROL dtmfnotify event)
-------------------------------------------
CFW 478ed6f1775b CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 180
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="01d1b38">
<dtmfnotify matchmode="collect" dtmf="*6" \
timestamp="2008-12-17T17:21:02Z"/>
</event>
</mscivr>
F2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 478ed6f1775b 200
G1. AS -> MS (CFW CONTROL, modifyjoin with setstate)
----------------------------------------------------
CFW 7fdcc2331bef CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 295
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<modifyjoin id1="873975758:a5105056" id2="54b4ab3">
<stream media="audio" direction="sendonly">
<volume controltype="setstate" value="mute"/>
</stream>
<stream media="audio" direction="recvonly"/>
</modifyjoin>
</mscmixer>
G2. AS <- MS (CFW 200 OK)
-------------------------
CFW 7fdcc2331bef 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 123
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join modified"/>
</mscmixer>
H1. AS <- MS (CFW CONTROL dtmfnotify event)
-------------------------------------------
CFW 750b917a5d4a CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 180
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="01d1b38">
<dtmfnotify matchmode="collect" dtmf="*0" \
timestamp="2008-12-17T17:21:05Z"/>
</event>
</mscivr>
H2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 750b917a5d4a 200
I1. AS -> MS (CFW CONTROL, dialogterminate)
-------------------------------------------
CFW 515f007c5bd0 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 128
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogterminate dialogid="01d1b38" immediate="true"/>
</mscivr>
I2. AS <- MS (CFW 200 OK)
-------------------------
CFW 515f007c5bd0 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 140
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<response status="200" reason="Dialog terminated" \
dialogid="01d1b38"/>
</mscivr>
J1. AS <- MS (CFW CONTROL dialogexit event)
-------------------------------------------
CFW 76adc41122c1 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 155
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<event dialogid="01d1b38">
<dialogexit status="0" reason="Dialog terminated"/>
</event>
</mscivr>
J2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 76adc41122c1 200
K1. AS -> MS (CFW CONTROL, unjoin)
----------------------------------
CFW 4e6afb6625e4 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 127
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<unjoin id1="873975758:a5105056" id2="54b4ab3"/>
</mscmixer>
K2. AS <- MS (CFW 200 OK)
-------------------------
CFW 4e6afb6625e4 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 122
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<response status="200" reason="Join removed"/>
</mscmixer>
L1. AS <- MS (CFW CONTROL unjoin-notify event)
----------------------------------------------
CFW 577696293504 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 157
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<event>
<unjoin-notify status="0" \
id1="873975758:a5105056" id2="54b4ab3"/>
</event>
</mscmixer>
L2. AS -> MS (CFW 200, ACK to 'CONTROL event')
----------------------------------------------
CFW 577696293504 200
| TOC |
All the flows presented so far describe the interaction between a single AS and a single MS. This is the most simple topology that can be envisaged in a MEDIACTRL-compliant architecture, but it's not the only allowed one. [RFC5567] (Melanchuk, T., “An Architectural Framework for Media Server Control,” June 2009.) presents several possible topologies, potentially involving several AS and several MS as well. To properly allow for such topologies, an additional element has been introduced in the MEDIACTRL architecture, called Media Resource Broker (MRB). Such an entity, and the protocols needed to interact with it, has been standardized in [I‑D.ietf‑mediactrl‑mrb] (Boulton, C. and L. Miniero, “Media Resource Brokering,” March 2010.).
TBD.
| TOC |
Each MS makes use of the publishing interface to provide an MRB with relevant information. This publishing interface, as specified in [I‑D.ietf‑mediactrl‑mrb] (Boulton, C. and L. Miniero, “Media Resource Brokering,” March 2010.), is made available as a control package for the Media Control Channel Framework. This means that, in order to receive information from a MS, an MRB must negotiate a control channel as explained in Section 5 (Control Channel Establishment). This package allows a MRB to request information from a MS, be it as a direct request/answer or by subscribing for events.
Of course, considering the MRB is interested in the publishing interface, the already mentioned negotiation must be changed in order to take into account the need for the MRB control package. The name of this package is 'mrb-publish/1.0', which means the SYNC might look like the following:
1. MRB -> MS (CFW SYNC) ----------------------- CFW 6b8b4567327b SYNC Dialog-ID: z9hG4bK-4542-1-0 Keep-Alive: 100 Packages: msc-ivr/1.0,msc-mixer/1.0,mrb-publish/1.0 2. MRB <- MS (CFW 200) ---------------------- CFW 6b8b4567327b 200 Keep-Alive: 100 Packages: msc-ivr/1.0,msc-mixer/1.0,mrb-publish/1.0 Supported: msc-example-pkg/1.0
The meaning of this negotiation has already been presented. It is enough to point out that, in this case, the MRB adds a new voice to the 'Packages' it needs support for (mrb-publish/1.0). In this case, the MS supports it, and in fact it is added to the negotiated packages in the reply:
Packages: msc-ivr/1.0,msc-mixer/1.0,mrb-publish/1.0
^^^^^^^^^^^^^^^
The MS of Section 5 (Control Channel Establishment), instead, did not have support for that package, since only 'msc-example-pkg/1.0' was part of the 'Supported' list.
Figure 48 (Media Resource Brokering: Subscription and Notification) presents a ladder diagram of a typical interaction based on the MRB control package.
MRB MS
| |
| A1. CONTROL (MRB subscription) |
|--------------------------------------------->|
| A2. 200 OK |
|<---------------------------------------------|
| |--+ collect
| | | requested
| |<-+ info
| B1. CONTROL (MRB notification) |
|<---------------------------------------------|
| B2. 200 OK |
|--------------------------------------------->|
| |
. .
. .
| |
| |--+ collect
| | | up-to-date
| |<-+ info
| C1. CONTROL (MRB notification) |
|<---------------------------------------------|
| C2. 200 OK |
|--------------------------------------------->|
| |
. .
. .
| Figure 48: Media Resource Brokering: Subscription and Notification |
In this example, the MRB subscribes for information at the specified MS, and events are triggered at a regular, negotiated, basis. All this messages flow through the control channel as all the messages in this document. The framework transaction steps are the following:
A1. MRB -> MS (CFW CONTROL, MRB subscription)
---------------------------------------------
CFW 238e1f2946e8 CONTROL
Control-Package: mrb-publish/1.0
Content-Type: application/mrb-publish+xml
Content-Length: 206
<mrbpublish version="1.0" xmlns="urn:ietf:params:xml:ns:mrb-publish">
<mrbrequest>
<subscription id="5gxccs" seqnumber="0">
<frequency>5</frequency>
</subscription>
</mrbrequest>
</mrbpublish>
A2. MRB <- MS (CFW 200 OK)
--------------------------
CFW 238e1f2946e8 200
Timeout: 10
Content-Type: application/mrb-publish+xml
Content-Length: 139
<mrbpublish version="1.0" xmlns="urn:ietf:params:xml:ns:mrb-publish">
<mrbresponse status="200" reason="OK: Request accepted"/>
</mrbpublish>
B1. MRB <- MS (CFW CONTROL dtmfnotify event)
--------------------------------------------
CFW 0b2ad6fa6c6c CONTROL
Control-Package: mrb-publish/1.0
Content-Type: application/mrb-publish+xml
Content-Length: 2538
<mrbpublish version="1.0" xmlns="urn:ietf:params:xml:ns:mrb-publish">
<mrbnotification id="5gxccs" seqnumber="1">
<media-server-id>
a1b2c3d4
</media-server-id>
<active-rtp-sessions>
<rtp-codec name="G.711">
<decoding>10</decoding>
<encoding>20</decoding>
</rtp-codec>
</active-rtp-sessions>
<active-mixer-sessions>
<active-mix conferenceid="7cfgs43">
<rtp-codec name="G.711">
<decoding>3</decoding>
<encoding>3</decoding>
</rtp-codec>
</active-mix>
</active-mixer-sessions>
<non-active-rtp-sessions>
<rtp-codec name="G.711">
<decoding>50</decoding>
<encoding>40</encoding>
</rtp-codec>
</non-active-rtp-sessions>
<non-active-mixer-sessions>
<non-active-mix available="15">
<rtp-codec name="G.711">
<decoding/>
<encoding/>
</rtp-codec>
</non-active-mix>
</non-active-mixer-sessions>
<media-server-status>
active
</media-server-status>
<supported-codecs>
<supported-codec name="G.711">
<supported-codec-package name="msc-ivr">
<supported-actions>
encoding
</supported-actions>
<supported-actions>
decoding
</supported-actions>
</supported-codec-package>
<supported-codec-package name="msc-mixer">
<supported-actions>
encoding
</supported-actions>
<supported-actions>
decoding
</supported-actions>
</supported-codec-package>
</supported-codec>
</supported-codecs>
<application-data>
Testbed Prototype
</application-data>
<file-formats>
<supported-format name="audio/x-wav">
<supported-file-package>
msc-ivr
</supported-file-package>
</supported-format>
</file-formats>
<max-prepared-duration>
<max-time max-time-seconds="3600">
<max-time-package>
msc-ivr
</max-time-package>
</max-time>
</max-prepared-duration>
<announce-var>
<param name="date" package="msc-ivr"/>
<param name="time" package="msc-ivr"/>
<param name="digits" package="msc-ivr"/>
</announce-var>
<dtmf-support>
<detect>
<dtmf-type name="RFC4733" package="msc-ivr"/>
<dtmf-type name="RFC4733" package="msc-mixer"/>
</detect>
<generate>
<dtmf-type name="RFC4733" package="msc-ivr"/>
<dtmf-type name="RFC4733" package="msc-mixer"/>
</generate>
<passthrough>
<dtmf-type name="RFC4733" package="msc-ivr"/>
<dtmf-type name="RFC4733" package="msc-mixer"/>
</passthrough>
</dtmf-support>
<mixing-modes>
</mixing-modes>
<supported-tones>
</supported-tones>
<streaming-modes>
<stream-mode name="HTTP" package="msc-ivr"/>
</streaming-modes>
<asr-tts-support>
</asr-tts-support>
<vxml-support support="true">
<vxml-mode package="msc-ivr" support="msc-ivr/1.0"/>
</vxml-support>
<media-server-location>
</media-server-location>
<label>
TestbedPrototype-01
</label>
<media-server-address>
sip:MediaServer@ms.example.net
</media-server-address>
<encryption>
</encryption>
</mrbnotification>
</mrbpublish>
B2. MRB -> MS (CFW 200, ACK to 'CONTROL event')
-----------------------------------------------
CFW 0b2ad6fa6c6c 200
| TOC |
TBD.
| TOC |
All the MEDIACTRL documents have strong statements regarding security considerations within the context of the interactions occurring at all the levels among the involved parties. Considering the sensitive nature of the interaction between AS and MS, particular efforts have been devoted in providing guidance upon securing what flows through a Control Channel. In fact, transactions concerning dialogs, connections and mixes are quite strongly related to resources actually being deployed and made use of in the MS. This means that it is in the interest of both AS and MS that resources created and handled by an entity are not unwillingly manipulated by a potentially malicious third party.
Considering that strong statements are already provided in the aforementioned documents, and that these documents already give good guidance to implementors with respect to these issues, this section will only provide the reader with some MEDIACTRL call flows, showing how a single secured MS is assumed to reply to different AS when receiving requests that may cross the bounds each AS is constrained into. It is the case, for instance, of generic auditing requests, or explicit conference manipulation requests where the involved identifiers are not part of the context of the originating AS.
To address a very specific scenario, let's assume that two different AS, AS1 and AS2, have established a Control Channel with the same MS. Let's also assume that AS1 has created a conference mix (confid=74b6d62) to which it has attached some participants within the context of its business logic, while AS2 has created a currently active IVR dialog (dialogid=dfg3252) with a user agent it is handling (237430727:a338e95f); besides, AS2 has also joined two connections to each other (1:75d4dd0d and 1:b9e6a659). As it is clear, it is highly desirable that AS1 is not aware of what AS2 is doing with the MS and viceversa, and that they are not allowed to manipulate the other's resources. The following transactions will occur, and it will be shown how the MS is assumed to reply in all the cases in order to avoid security issues:
A sequence diagram of the mentioned transactions is depicted in Figure 49 (Security Considerations: Framework Transaction):
AS1 AS2 MS
| | |
| A1. CONTROL (IVR audit) |
|++++++++++++++++++++++++++++++++++++++++++++++++++++++++>>|
| | A2. 200 OK |
|<<++++++++++++++++++++++++++++++++++++++++++++++++++++++++|
| | |
| B1. CONTROL (Mixer audit) |
|++++++++++++++++++++++++++++++++++++++++++++++++++++++++>>|
| | B2. 200 OK |
|<<++++++++++++++++++++++++++++++++++++++++++++++++++++++++|
| | |
| | C1. CONTROL (IVR audit) |
| |++++++++++++++++++++++++++++++++>>|
| | C2. 200 OK |
| |<<++++++++++++++++++++++++++++++++|
| | |
| | D1. CONTROL (Mixer audit) |
| |++++++++++++++++++++++++++++++++>>|
| | D2. 200 OK |
| |<<++++++++++++++++++++++++++++++++|
| | |
| E1. CONTROL (dialogterminate) |
|++++++++++++++++++++++++++++++++++++++++++++++++++++++++>>|
| | E2. 403 Forbidden |
|<<++++++++++++++++++++++++++++++++++++++++++++++++++++++++|
| | |
| | F1. CONTROL (join UAC&conf[AS1]) |
| |++++++++++++++++++++++++++++++++>>|
| | F2. 403 Forbidden |
| |<<++++++++++++++++++++++++++++++++|
| | |
. . .
. . .
| Figure 49: Security Considerations: Framework Transaction |
The expected outcome of the transaction is the MS partially "lying" to both AS1 and AS2 when replying to the audit requests (not all the identifiers are reported, but only the ones each AS is directly involved in), and the MS denying the requests for the unauthorized operations (403). Looking at each transaction separately:
A1. AS1 -> MS (CFW CONTROL, audit IVR)
--------------------------------------
CFW 140e0f763352 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 81
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<audit/>
</mscivr>
A2. AS1 <- MS (CFW 200, auditresponse)
--------------------------------------
CFW 140e0f763352 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 1419
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<auditresponse status="200">
<capabilities>
<codecs>
<codec><subtype>telephony-event</subtype></codec>
<codec><subtype>PCMA</subtype></codec>
<codec><subtype>PCMU</subtype></codec>
<codec><subtype>GSM</subtype></codec>
<codec><subtype>H.261</subtype></codec>
<codec><subtype>H.263</subtype></codec>
<codec><subtype>H.263+</subtype></codec>
<codec><subtype>H.264</subtype></codec>
</codecs>
<dialoglanguages/>
<grammartypes/>
<prompttypes>
<mimetype>audio/wav</mimetype>
<mimetype>video/mpeg</mimetype>
</prompttypes>
<recordtypes>
<mimetype>audio/wav</mimetype>
<mimetype>video/mpeg</mimetype>
</recordtypes>
<variables>
<variabletype type="date" \
desc="value formatted as YYYY-MM-DD">
<format desc="month year day">mdy</format>
<format desc="year month day">ymd</format>
<format desc="day month year">dmy</format>
<format desc="day month">dm</format>
</variabletype>
<variabletype type="time" desc="value formatted as HH:MM">
<format desc="24 hour format">t24</format>
<format desc="12 hour format with am/pm">t12</format>
</variabletype>
<variabletype type="digits" desc="value formatted as D+">
<format desc="general digit string">gen</format>
<format desc="cardinal">crn</format>
<format desc="ordinal">ord</format>
</variabletype>
</variables>
<maxpreparedduration>60s</maxpreparedduration>
<maxrecordduration>1800s</maxrecordduration>
</capabilities>
<dialogs>
</dialogs>
</auditresponse>
</mscivr>
B1. AS1 -> MS (CFW CONTROL, audit mixer)
----------------------------------------
CFW 0216231b1f16 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 87
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<audit/>
</mscmixer>
B2. AS1 <- MS (CFW 200, auditresponse)
--------------------------------------
CFW 0216231b1f16 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 903
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<auditresponse status="200">
<capabilities>
<codecs>
<codec><subtype>telephony-event</subtype></codec>
<codec><subtype>PCMA</subtype></codec>
<codec><subtype>PCMU</subtype></codec>
<codec><subtype>GSM</subtype></codec>
<codec><subtype>H.261</subtype></codec>
<codec><subtype>H.263</subtype></codec>
<codec><subtype>H.263+</subtype></codec>
<codec><subtype>H.264</subtype></codec>
</codecs>
</capabilities>
<mixers>
<conferenceaudit conferenceid="74b6d62">
<participants>
<participant id="1864574426:e2192766"/>
<participant id="1:5a97fd79"/>
</participants>
<video-layouts>
<video-layout min-participants="1">quad-view<video-layout>
<video-layout min-participants="5">multiple-5x1<video-layout>
</video-layouts>
</conferenceaudit>
<joinaudit id1="1864574426:e2192766" id2="74b6d62"/>
<joinaudit id1="1:5a97fd79" id2="74b6d62"/>
</mixers>
</auditresponse>
</mscmixer>
C1. AS2 -> MS (CFW CONTROL, audit IVR)
--------------------------------------
CFW 0216231b1f16 CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 81
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<audit/>
</mscivr>
C2. AS2 <- MS (CFW 200, auditresponse)
--------------------------------------
CFW 0216231b1f16 200
Timeout: 10
Content-Type: application/msc-ivr+xml
Content-Length: 1502
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<auditresponse status="200">
<capabilities>
<codecs>
<codec><subtype>telephony-event</subtype></codec>
<codec><subtype>PCMA</subtype></codec>
<codec><subtype>PCMU</subtype></codec>
<codec><subtype>GSM</subtype></codec>
<codec><subtype>H.261</subtype></codec>
<codec><subtype>H.263</subtype></codec>
<codec><subtype>H.263+</subtype></codec>
<codec><subtype>H.264</subtype></codec>
</codecs>
<dialoglanguages/>
<grammartypes/>
<prompttypes>
<mimetype>audio/wav</mimetype>
<mimetype>video/mpeg</mimetype>
</prompttypes>
<recordtypes>
<mimetype>audio/wav</mimetype>
<mimetype>video/mpeg</mimetype>
</recordtypes>
<variables>
<variabletype type="date" \
desc="value formatted as YYYY-MM-DD">
<format desc="month year day">mdy</format>
<format desc="year month day">ymd</format>
<format desc="day month year">dmy</format>
<format desc="day month">dm</format>
</variabletype>
<variabletype type="time" desc="value formatted as HH:MM">
<format desc="24 hour format">t24</format>
<format desc="12 hour format with am/pm">t12</format>
</variabletype>
<variabletype type="digits" desc="value formatted as D+">
<format desc="general digit string">gen</format>
<format desc="cardinal">crn</format>
<format desc="ordinal">ord</format>
</variabletype>
</variables>
<maxpreparedduration>60s</maxpreparedduration>
<maxrecordduration>1800s</maxrecordduration>
</capabilities>
<dialogs>
<dialogaudit dialogid="6791fee" state="started" \
connectionid="237430727:a338e95f"/>
</dialogs>
</auditresponse>
</mscivr>
D1. AS2 -> MS (CFW CONTROL, audit mixer)
----------------------------------------
CFW 515f007c5bd0 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 87
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<audit/>
</mscmixer>
D2. AS2 <- MS (CFW 200, auditresponse)
--------------------------------------
CFW 515f007c5bd0 200
Timeout: 10
Content-Type: application/msc-mixer+xml
Content-Length: 548
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<auditresponse status="200">
<capabilities>
<codecs>
<codec><subtype>telephony-event</subtype></codec>
<codec><subtype>PCMA</subtype></codec>
<codec><subtype>PCMU</subtype></codec>
<codec><subtype>GSM</subtype></codec>
<codec><subtype>H.261</subtype></codec>
<codec><subtype>H.263</subtype></codec>
<codec><subtype>H.263+</subtype></codec>
<codec><subtype>H.264</subtype></codec>
</codecs>
</capabilities>
<mixers>
<joinaudit id1="1:75d4dd0d" id2="1:b9e6a659"/>
</mixers>
</auditresponse>
</mscmixer>
E1. AS1 -> MS (CFW CONTROL, dialogterminate)
--------------------------------------------
CFW 7fdcc2331bef CONTROL
Control-Package: msc-ivr/1.0
Content-Type: application/msc-ivr+xml
Content-Length: 127
<mscivr version="1.0" xmlns="urn:ietf:params:xml:ns:msc-ivr">
<dialogterminate dialogid="6791fee" immediate="true"/>
</mscivr>
E2. AS1 <- MS (CFW 403 Forbidden)
---------------------------------
CFW 7fdcc2331bef 403
F1. AS2 -> MS (CFW CONTROL, join to conference)
-----------------------------------------------
CFW 140e0f763352 CONTROL
Control-Package: msc-mixer/1.0
Content-Type: application/msc-mixer+xml
Content-Length: 117
<mscmixer version="1.0" xmlns="urn:ietf:params:xml:ns:msc-mixer">
<join id1="1:272e9c05" id2="74b6d62"/>
</mscmixer>
F2. AS2 <- MS (CFW 403 Forbidden)
---------------------------------
CFW 140e0f763352 403
| TOC |
The following are the major changes between the 01 and the 02 versions of the draft:
The following are the major changes between the 00 and the 01 versions of the draft:
| TOC |
The authors would like to thank...
| TOC |
| [RFC2234] | Crocker, D., Ed. and P. Overell, “Augmented BNF for Syntax Specifications: ABNF,” RFC 2234, November 1997 (TXT, HTML, XML). |
| [RFC2119] | Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). |
| [RFC2434] | Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” BCP 26, RFC 2434, October 1998 (TXT, HTML, XML). |
| [RFC2606] | Eastlake, D. and A. Panitz, “Reserved Top Level DNS Names,” BCP 32, RFC 2606, June 1999 (TXT). |
| [RFC3261] | Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” RFC 3261, June 2002 (TXT). |
| [RFC3264] | Rosenberg, J. and H. Schulzrinne, “An Offer/Answer Model with Session Description Protocol (SDP),” RFC 3264, June 2002 (TXT). |
| [RFC3725] | Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo, “Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP),” BCP 85, RFC 3725, April 2004 (TXT). |
| [RFC3550] | Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications,” STD 64, RFC 3550, July 2003 (TXT, PS, PDF). |
| [RFC4574] | Levin, O. and G. Camarillo, “The Session Description Protocol (SDP) Label Attribute,” RFC 4574, August 2006 (TXT). |
| [RFC4145] | Yon, D. and G. Camarillo, “TCP-Based Media Transport in the Session Description Protocol (SDP),” RFC 4145, September 2005 (TXT). |
| [RFC4597] | Even, R. and N. Ismail, “Conferencing Scenarios,” RFC 4597, August 2006 (TXT). |
| [RFC5167] | Dolly, M. and R. Even, “Media Server Control Protocol Requirements,” RFC 5167, March 2008 (TXT). |
| [RFC5567] | Melanchuk, T., “An Architectural Framework for Media Server Control,” RFC 5567, June 2009 (TXT). |
| [I-D.ietf-mediactrl-sip-control-framework] | Boulton, C., Melanchuk, T., and S. McGlashan, “Media Control Channel Framework,” draft-ietf-mediactrl-sip-control-framework-11 (work in progress), October 2009 (TXT). |
| [I-D.boulton-mmusic-sdp-control-package-attribute] | Boulton, C., “A Session Description Protocol (SDP) Control Package Attribute,” draft-boulton-mmusic-sdp-control-package-attribute-04 (work in progress), March 2009 (TXT). |
| [I-D.ietf-mediactrl-ivr-control-package] | McGlashan, S., Melanchuk, T., and C. Boulton, “An Interactive Voice Response (IVR) Control Package for the Media Control Channel Framework,” draft-ietf-mediactrl-ivr-control-package-08 (work in progress), February 2010 (TXT). |
| [I-D.ietf-mediactrl-mixer-control-package] | McGlashan, S., Melanchuk, T., and C. Boulton, “A Mixer Control Package for the Media Control Channel Framework,” draft-ietf-mediactrl-mixer-control-package-11 (work in progress), February 2010 (TXT). |
| [I-D.ietf-mediactrl-mrb] | Boulton, C. and L. Miniero, “Media Resource Brokering,” draft-ietf-mediactrl-mrb-04 (work in progress), March 2010 (TXT). |
| [RFC5239] | Barnes, M., Boulton, C., and O. Levin, “A Framework for Centralized Conferencing,” RFC 5239, June 2008 (TXT). |
| [RFC4582] | Camarillo, G., Ott, J., and K. Drage, “The Binary Floor Control Protocol (BFCP),” RFC 4582, November 2006 (TXT). |
| [RFC4583] | Camarillo, G., “Session Description Protocol (SDP) Format for Binary Floor Control Protocol (BFCP) Streams,” RFC 4583, November 2006 (TXT). |
| TOC |
| Alessandro Amirante | |
| University of Napoli | |
| Via Claudio 21 | |
| Napoli 80125 | |
| Italy | |
| Email: | alessandro.amirante@unina.it |
| Tobia Castaldi | |
| University of Napoli | |
| Via Claudio 21 | |
| Napoli 80125 | |
| Italy | |
| Email: | tobia.castaldi@unina.it |
| Lorenzo Miniero | |
| University of Napoli | |
| Via Claudio 21 | |
| Napoli 80125 | |
| Italy | |
| Email: | lorenzo.miniero@unina.it |
| Simon Pietro Romano | |
| University of Napoli | |
| Via Claudio 21 | |
| Napoli 80125 | |
| Italy | |
| Email: | spromano@unina.it |