CLUE Working Group R. Presta Internet-Draft S P. Romano Intended status: Informational University of Napoli Expires: January 11, 2014 July 10, 2013 CLUE protocol (??) draft-presta-clue-protocol-00 Abstract This is a work-in-progress draft aimed at shedding light on the application-level protocol associated with the creation and management of a CLUE-enabled telepresence session between a Media Consumer and a Media Provider. The draft sketches the high-level interactions occurring between the above mentioned entities, as well as depicts the state transitions occurring at both ends during a telepresence session. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 11, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Presta & Romano Expires January 11, 2014 [Page 1] Internet-Draft draft-presta-clue-protocol-00 July 2013 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview of the CLUE protocol messages . . . . . . . . . . . . 3 3.1. ADVERTISEMENT . . . . . . . . . . . . . . . . . . . . . . 4 3.2. CONFIGURE . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3. RESPONSE . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.4. RE-ADV . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol state machines . . . . . . . . . . . . . . . . . . . 9 5. Media Consumer's state machine . . . . . . . . . . . . . . . . 10 6. Media Provider's state machine . . . . . . . . . . . . . . . . 12 7. Informative References . . . . . . . . . . . . . . . . . . . . 14 Presta & Romano Expires January 11, 2014 [Page 2] Internet-Draft draft-presta-clue-protocol-00 July 2013 1. Introduction The CLUE protocol is an application protocol used by a Media Provider (MP) and a Media Consumer (MC) in order to establish a multimedia telepresence session. CLUE protocol messages flow across a DTLS/SCTP channel established as depicted in [I-D.kyzivat-clue-signaling]. While [I-D.kyzivat-clue-signaling] focuses on signaling details about the protocol and its interaction with the SIP/SDP session establishment mechanisms, we herein concentrate only on the protocol in action and try to define the behavior of both the MP and the MC at the CLUE application level. In other words, we assume the DTLS/SCTP channel has already been established and discuss how the CLUE dialogue between the MP and the MC can be exploited to successfully setup the telepresence session according to the principles and concepts pointed out in in [I-D.kyzivat-clue-signaling] and in [I-D.ietf-clue-framework]. In Section 3 we provide the list of the CLUE messages, together with an overview of their features and functionality. MC's and MP's state machines are introduced in Section 4 and further described in Section 5 and Section 6 respectively. 2. Terminology This document refers to the same terminology used in [I-D.ietf-clue-framework] and in [I-D.kyzivat-clue-signaling]. 3. Overview of the CLUE protocol messages This section contains a bird's-eye view of the CLUE protocol messages. For each message it is indicated who sends it, who receives it, a brief description of the information it carries, and how/when it is used. Besides the well-known ADVERTISEMENT and CONFIGURE messages, new ones have been conceived in order to fulfill the mechanisms and operations pointed out in [I-D.kyzivat-clue-signaling]. o ADVERTISEMENT (ADV) o CONFIGURE (CONF) o RESPONSE o RE-ADV Presta & Romano Expires January 11, 2014 [Page 3] Internet-Draft draft-presta-clue-protocol-00 July 2013 3.1. ADVERTISEMENT +---------- ---+-----------------------------------------------------+ | | | | FROM | MP | | | | +--------------+-----------------------------------------------------+ | | | | TO | MC | | | | +--------------+-----------------------------------------------------+ | | | | TYPE | Notification | | | | +--------------+-----------------------------------------------------+ | | | | DESCRIPTION | This message is used by the MP to advertise the | | | available media captures and related information | | | to the MC. | | | The ADV contains elements compliant with the | | | CLUE data model and other information like the | | | CLUE protocol version and a sequence number. | | | | +--------------+-----------------------------------------------------+ | | | | USAGE | The MP sends this message as soon as the CLUE | | | channel is ready. The MP sends an ADV to the | | | MC every time there is a modification of the MP's | | | telepresence capabilities. | | | The ADV message is also sent back to the MC | | | when the MP receives a RE-ADV request. | +--------------+-----------------------------------------------------+ 3.2. CONFIGURE Presta & Romano Expires January 11, 2014 [Page 4] Internet-Draft draft-presta-clue-protocol-00 July 2013 +--------------+-----------------------------------------------------+ | | | | FROM | MC | | | | +--------------+-----------------------------------------------------+ | | | | TO | MP | | | | +--------------+-----------------------------------------------------+ | | | | TYPE | Request | | | | +--------------+-----------------------------------------------------+ | | | | DESCRIPTION | This message allows a MC to request the | | | desired advertised capture. It contains capture | | | encodings and other information like the CLUE | | | protocol version and a sequence number. | | | | +--------------+-----------------------------------------------------+ | | | | USAGE | The MC can send a CONF after the reception of | | | an ADV or every time it wants to request other | | | advertised captures to the MP. | +--------------+-----------------------------------------------------+ 3.3. RESPONSE Presta & Romano Expires January 11, 2014 [Page 5] Internet-Draft draft-presta-clue-protocol-00 July 2013 +--------------+-----------------------------------------------------+ | | | | FROM | MP | | | | +--------------+-----------------------------------------------------+ | | | | TO | MC | | | | +--------------+-----------------------------------------------------+ | | | | TYPE | Response | | | | +--------------+-----------------------------------------------------+ | | | | DESCRIPTION | This message allows a MP to answer to a CONF | | | message. Besides the protocol version and a | | | sequence number, it contains a response code with | | | a response string indicating either the success | | | or the failure (along with failure details) of | | | the CONF request elaboration. | | | Examples of response codes and strings are | | | provided in a following table. | | | | +--------------+-----------------------------------------------------+ | | | | USAGE | The MP sends this message in response to CONF | | | messages. | +--------------+-----------------------------------------------------+ Response codes can be defined by following the HTTP semantics as below. Presta & Romano Expires January 11, 2014 [Page 6] Internet-Draft draft-presta-clue-protocol-00 July 2013 +-----------------+----------------------+--------------------------+ | | | | | Response code | Response string | Description | | | | | +-----------------+----------------------+--------------------------+ | | | | | 410 | Bad syntax | The XML syntax of the | | | | CONF message is not | | | | correct. | +-----------------+----------------------+--------------------------+ | | | | | 411 | Invalid value | The CONF message | | | | contains an invalid | | | | parameter value. | +-----------------+----------------------+--------------------------+ | | | | | 412 | Invalid identifier | The identifier used to | | | | request a capture is | | | | either invalid or | | | | unknown. | +-----------------+----------------------+--------------------------+ | | | | | 413 | Conflicting values | The CONF message | | | | contains values that | | | | cannot be used together.| +-----------------+----------------------+--------------------------+ | | | | | 420 | Invalid sequencing | The sequence number of | | | | the CONF message is out | | | | of date or corresponds | | | | to an obsoleted ADV. | +-----------------+----------------------+--------------------------+ | | | | | 510 | Version not supported| The CLUE protocol | | | | version of the CONF | | | | message is not supported| | | | by the MP. | +-----------------+----------------------+--------------------------+ | | | | | 511 | Option not supported | The option requested in | | | | the CONF message is not | | | | supported by the MP. | +-----------------+----------------------+--------------------------+ To Be Continued... Presta & Romano Expires January 11, 2014 [Page 7] Internet-Draft draft-presta-clue-protocol-00 July 2013 +---------------+------------------------+ | | | | Response code | Rescription | | family | | +---------------+------------------------+ | | | | 1XX | Temporary info | | | | +---------------+------------------------+ | | | | 2XX | Success | | | | +---------------+------------------------+ | | | | 3XX | Redirection | | | | +---------------+------------------------+ | | | | 4XX | Client error | | | | +---------------+------------------------+ | | | | 5XX | Server error | | | | +---------------+------------------------+ 3.4. RE-ADV Presta & Romano Expires January 11, 2014 [Page 8] Internet-Draft draft-presta-clue-protocol-00 July 2013 +---------- ---+-----------------------------------------------------+ | | | | FROM | MC | | | | +--------------+-----------------------------------------------------+ | | | | TO | MP | | | | +--------------+-----------------------------------------------------+ | | | | TYPE | Request | | | | +--------------+-----------------------------------------------------+ | | | | DESCRIPTION | This message allows a MC to request that the MP | | | issues a new copy of the ADV. This message can | | | contain a reason string indicating the motivation | | | for the request (e.g., refresh, missing elements | | | in the received ADV, wrong syntax in the received | | | ADV, invalid capture area, invalid line of | | | capture point, etc). | | | | +--------------+-----------------------------------------------------+ | | | | USAGE | The MC sends this message to the MP when the | | | timeout for the ADV is fired, or when the ADV is | | | not compliant with the CLUE specifications (this | | | can be useful for interoperability testing | | | purposes) | | | | +--------------+-----------------------------------------------------+ 4. Protocol state machines The CLUE protocol is an application-layer protocol used between a Media Provider (MP) and a Media Consumer (MC), used to establish a multimedia telepresence session. CLUE protocol messages flow across a DTLS/SCTP channel established as depicted in [I-D.kyzivat-clue-signaling]. Over such a channel there are typically two CLUE streams between the channel terminations flowing in opposite directions. In other words, typically, both channel terminations act simultaneously as a MP and as a MC. We herein discuss the state machines associated with both the MP process and the MC process. Presta & Romano Expires January 11, 2014 [Page 9] Internet-Draft draft-presta-clue-protocol-00 July 2013 5. Media Consumer's state machine An MC in the IDLE state is waiting for an ADV coming from the MP. If the timeout expires ("timeout"), the MC switches to the TIMEOUT state. In the TIMEOUT state, if the number of trials is under the retry threshold, the MC issues a RE-ADV/refresh message to the MP ("send RE-ADV"), switching back to the IDLE state. Otherwise, the MC moves to the TERMINATED state. When the ADV has been received ("receive ADV"), the MC goes into the ADV RECEIVED state. The ADV is then parsed. If something goes wrong with the ADV (bad syntax, missing XML elements, etc.), the MC sends a RE-ADV message to the MP specifying the encountered problem via a proper reason phrase. This forces the MC to go back to the IDLE state, waiting for a new copy of the ADV. If the ADV is successfully processed, the MC issues a CONF message to the MP ("send CONF") and switches to the TRYING state. While in the TRYING state, the MC is waiting for a RESPONSE message to the issued CONF from the MP. If the timeout expires ("timeout"), the MC moves to the TIMEOUT state and sends a RE-ADV in order to solicit a new ADV from the MP. If a RESPONSE with an error code is received ("receive 4xx, 5xx not supported"), then the MC goes back to the ADV-RCVD state and builds a new CONF message to be sent to the MP. If a successful RESPONSE arrives ("receive 200 OK"), the MC enters the IN CALL state. If a new ADV arrives in the meanwhile, it is ignored. Indeed, after the timeout is exceeded, the MC goes to the TIMEOUT state and then sends a RE-ADV to the MP. When the MC is in the IN CALL state, the telepresence session has been set up according to the MC's preferences. Both MP and MC have agreed on (and are aware of) the media streams to be exchanged within the call. If the MC decides to change something in the call settings, it issues a new CONF ("send CONF") and goes back to the TRYING state. If a new ADV arrives from the MP ("receive ADV"), it means that something has changed on the MP's side. The MC then moves to the ADV-RCV state and prepares a new CONF taking into account the received updates. When the underlying channel is closed, the MC moves to the TERMINATED state. The TERMINATED state is reachable from each of the aforementioned states whenever the underlying channel is closed. The corresponding transitions have not been reported for the sake of simplicity. This termination condition is a temporary solution. The TERMINATED state is reachable from each of the aforementioned Presta & Romano Expires January 11, 2014 [Page 10] Internet-Draft draft-presta-clue-protocol-00 July 2013 states whenever the underlying channel is closed. The corresponding transitions have not been reported for the sake of simplicity. This termination condition is a temporary solution. +-----+ +--------+-------------timeout------>+----+--+ | | IDLE +<----+ |TIMEOUT| | +---+----+<----+--------send---------+-------+ | | | RE-ADV(refresh) ^ | | | | | | | | | receive send | | ADV RE-ADV | | | (missing elements, | | | invalid area,...) | | v | | | +---------+ | | | | ADV +----+ timeout | +----->| RECEIVED|<-----+ | | | +---+-----+ | | | | | | | | | | | | | | | | | | receive send receive | | ADV CONF 4xx, | | | | 5xx not supported | | | v | | | | +--------+-------+------------------------+ | | | TRYING +-------+ | | +---+----+<----+ | | | | | | | | | | receive send retry | 200 OK CONF expires | | | | | | | | | | | | | v | | | +------+ | | +-------+ IN | | | | CALL +------+ | +--+---+ | | | | | | | Presta & Romano Expires January 11, 2014 [Page 11] Internet-Draft draft-presta-clue-protocol-00 July 2013 | | connection | closed | | | | | | | | | | | v | +----------+<---------------------------------+ |TERMINATED| +----------+ 6. Media Provider's state machine In the IDLE state, the MP is preparing the ADV message reflecting the actual telepresence capabilities. After the ADV has been sent, the MP moves to the WAIT FOR CONF state. While in the WAIT FOR CONF state, the MP is listening to the channel for a CONF coming from the MC. If a RE-ADV is received, the MP goes back to the IDLE state and issues an ADV again. If telepresence settings change in the meanwhile, it goes back to the IDLE state too, and prepares a new ADV to be sent to the MC. If a CONF arrives, the MP switches to the CONF RECEIVED state. If nothing happens and the timeout expires, than the MC moves to the TIMEOUT state. In the TIMEOUT state, if the number of trials does not exceed the retry threshold, the MC comes back to the IDLE state to send a new ADV. Otherwise, it goes to the TERMINATED state. The MP in the CONF RECEIVED state is processing the received CONF in order to produce a RESPONSE message. If the MP is satisfied with the MC's configuration, then it sends a 200 OK successful RESPONSE and switches to the IN CALL state. If there are errors while processing the CONF, then the MC returns a RESPONSE carrying an error response code. Finally, if there are changes in the telepresence settings, it goes back to the IDLE state to issue an updated ADV. While in the IN CALL state, the MP has successfully set up the telepresence session according to the MC's specifications. If a new CONF arrives, it switches to the CONF RECEIVED state to analyze the new request. If a RE-ADV arrives, or some modifications are applied to the telepresence options, then it moves to the IDLE state to issue the ADV. When the channel is terminated, the MP switches to the TERMINATED state. Presta & Romano Expires January 11, 2014 [Page 12] Internet-Draft draft-presta-clue-protocol-00 July 2013 The TERMINATED state is reachable from each of the aforementioned states whenever the underlying channel is closed. The corresponding transitions have not been reported for the sake of simplicity. This termination condition is a temporary solution. +------------------->+-----+-+<----------------------------+ | +--------------->| IDLE |<-------------retry----------+-----+---+ | | +------->+---+---+<----+ not | | | | | | | expired | | | | | | | | | | | change send receive | ++------+ | | telepresence ADV RE-ADV | |TIMEOUT| | | settings | | | ++--+---+ | | | | | | ^ | | | | v | | | | | | | +-------------+---+ | | | | | +----+ WAIT FOR +------------timeout--------+-----+---+ | | | | CONF | | | change +-------+-----+<--+ | | telepresence | | | | settings | | | | | | receive send | | | | CONF error | | | | | response | | | | | | | | | | | | | | | | v | | | | | +-----------+---+ | | +---+-------------+| CONF | | | | +----->| RECEIVED | | | | | +-----+-----+ | | | | | | | | | | | | | | | | | receive receive send | | RE-ADV CONF 200 OK | retry| | | | | expired | | | | | | | | | | | | v | | | | +----------+ change | | | +-------+ IN CALL +--------telepresence-------+ | +---------------+----+-----+ settings | Presta & Romano Expires January 11, 2014 [Page 13] Internet-Draft draft-presta-clue-protocol-00 July 2013 | | | | | | | | connection | closed | | | | | v | +------------+<-----------------------------------+ | TERMINATED | +------------+ 7. Informative References [I-D.ietf-clue-framework] Duckworth, M., Pepperell, A., and S. Wenger, "Framework for Telepresence Multi-Streams", draft-ietf-clue-framework-10 (work in progress), May 2013. [I-D.kyzivat-clue-signaling] Kyzivat, P., Xiao, L., and C. Groves, "CLUE Signaling", draft-kyzivat-clue-signaling-03 (work in progress), June 2013. Authors' Addresses Roberta Presta University of Napoli Via Claudio 21 Napoli 80125 Italy EMail: roberta.presta@unina.it Simon Pietro Romano University of Napoli Via Claudio 21 Napoli 80125 Italy EMail: spromano@unina.it Presta & Romano Expires January 11, 2014 [Page 14]