Network Working Group Q. Sun
Internet-Draft L. Tian
Expires: January 2, 2008 D. Ren
Huawei Technologies
July 2007
Multiple Reply in the Session Initiation Protocol (SIP)
draft-sun-sipping-multiple-reply-00
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Abstract
This document defines extensions to the Reply-To header field for
MESSAGE so that it can be used to specify multiple addresses as the
target of reply MESSAGE. These extensions include the use of
pointers to Uniform Resource Identifier (URI)-lists in the Reply-To
header field and the "multiple-reply" SIP option-tag.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. URI-List Document Format . . . . . . . . . . . . . . . . . . . 5
4. Option-tag . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Procedures at the Reply-Issuer . . . . . . . . . . . . . . . . 8
6. Procedures at the Reply-Recipient . . . . . . . . . . . . . . 9
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Reply-Recipient use MESSAGE URI-List service to send
reply MESSAGE requests . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . 15
11. MIME Information . . . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. History of change . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 20
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1. Introduction
RFC 3261 [2] defines a Reply-To header field containing a logical
return URI that may be different from the From header field. For
example, the URI MAY be used to return missed calls or unestablished
sessions.
RFC 3428 [3] further defines the Reply-To as an optional header field
that can be used and present in MESSAGE requests and responses. This
allows the Reply-Issuer to provide Reply-Recipient with one User
Agent (UA) as the target of reply MESSAGE.
However in some scenarios, the Reply-Issuer may want the Reply-
Recipient to send reply MESSAGE to a list of UAs. For example, a
manager sends a message to notify the secretary to prepare a meeting.
At the same time the manager provides the list of attendees in the
message. Whenever the meeting is arranged the secretary can send
meeting information in reply message to the list of attendees.
Another use case may be that a scheduled reminder application sends a
message to a user, the message informs the user should send some
information, such as weekly project report, to a list of users while
the notification itself is not meaningful for the intended
recipients.
This specification extends the above Reply-To mechanim to fullfil
this requirement. The Reply-Issuer sends a MESSAGE request which
contains the Reply-To header field pointing to a URI-List (Uniform
Resource Identifier list) as the targets of reply MESSAGE to a Reply-
Recipient.
The Reply-Recipient may modify the provided list to add or remove
recipients.
The Reply-Recipient can create a reply MESSAGE request for each entry
in the URI-List and send them respectively or send a reply MESSAGE to
MESSAGE URI-list service [9] to distribute the reply MESSAGE
requests.
The requirements to support multiple reply may be summarized as
follows:
REQ-1: It MUST be possible for a Reply-Issuer to specify multiple
reply targets in a MESSAGE request, where the identities of the
reply targets are carried in the request itself.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]
This document defines the following new terms:
Reply-Issuer: the user agent issuing the SIP request with Reply-To
header field.
Reply-Recipient: the user agent receiving the SIP request with
Reply-To header field.
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3. URI-List Document Format
As described in the Framework and Security Considerations for SIP
URI-List Services [4] , specifications of individual URI-list
services, need to specify a default format for 'recipient-list'
bodies used within the particular service.
The default format for 'recipient-list' bodies for multiple reply is
XML Resource Lists [7] extended with Copy Control Attribute [8] .
Reply-Issuer and Reply-Recipient MUST support both of these formats
and MAY support other formats.
As described in Copy Control Attribute [8] , each URI can be tagged
with a 'copyControl' attribute set to either "to", "cc", or "bcc",
indicating the role in which the recipient will get the MESSAGE
request. Additionally, URIs can be tagged with the 'anonymize'
attribute to prevent that the Reply-Recipient (UAS) discloses the
target URI in a URI-list.
In addition, the XML Resource Lists [7] defines a 'recipient-list-
history' body that contains the list of recipients. The default
format for 'recipient-list-history' bodies for UAs is also the XML
Resource Lists [7] extended with the Copy Control Attribute [8] . If
the Reply-Recipient sends the reply MESSAGE requests for each entry
in the URI-List, it may provide 'recipient-list-history' body in the
reply MESSAGE requests. In this case the Reply-Recipient MAY support
these formats and MAY support others. If the Reply-Recipient sends
the reply MESSAGE request to MESSAGE URI-list service [9] , it does
not need to support these formats. UAs able to understand
'recipient-list-history' MUST support these formats and MAY support
others.
Nevertheless, the XML Resource Lists [7] provides features, such as
hierarchical lists and the ability to include entries by reference
relative to the XCAP root URI, that are not needed by the multiple
reply mechanism defined in this document, which only needs to
transfer a flat list of URIs between the Reply-Issuer and the Reply-
Recipient. Therefore, when using the default resource list document,
UAs SHOULD use flat lists (i.e., no hierarchical lists) and SHOULD
NOT use elements. A Reply-Recipient receiving a URI-list with more
information than what has just been described MAY discard all the
extra information.
Figure 1 shows an example of a flat list that follows XML Resource
Lists [7] extended with Copy Control Attribute [8] ).
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<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cp="urn:ietf:params:xml:ns:copycontrol">
<list>
<entry uri="sip:bill@example.com" cp:copyControl="to" />
<entry uri="sip:joe@example.org" cp:copyControl="cc" />
<entry uri="sip:ted@example.net" cp:copyControl="bcc" />
</list>
</resource-lists>
Figure 1: Example for XML Resource List Document
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4. Option-tag
This document defines a new SIP option-tag for the Require and
Supported header fields: "multiple-reply". A UA including the
"multiple-reply" option-tag in a Supported header field indicates
compliance with this specification.
A UA generating a MESSAGE request with a pointer to a URI-list in its
Reply-To header field MUST include the "multiple-reply" option-tag in
the Require header field of the MESSAGE request.
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5. Procedures at the Reply-Issuer
A Reply-Issuer that wants to specify multiple reply addresses MUST be
formatted according to Section 4 of RFC 3428 [3] . The Reply-Issuer
populates the Request-URI with the SIP or SIPS URI of the Reply-
Recipient. In addition to the regular MESSAGE body, the Reply-Issuer
adds a recipient-list body whose Content-Disposition type is
'recipient-list' as defined in Framework and Security Considerations
for SIP URI-List Services [4] . This body contains a URI-list with
the recipients of the reply MESSAGE from the Reply-Recipient. Target
URIs in this body MAY also be tagged with the 'copyControl' and
'anonymize' attributes specified in the Copy Control Attribute [8] .
The Reply-Issuer MUST provide an appropriate Content-ID for the
recipient-list body and populates the Reply-To with the value of
Content-ID which identifies the list of intended recipient of reply
message. The Reply-Issuer MUST also include the 'multiple-reply'
option-tag, defined in Section 4, in a Require header field.
the Reply-Issuer MAY use the "?" mechanism described in Section
19.1.1 of RFC 3261 [2] to encode extra information in any URI in the
list. The following is an example of a URI that uses the "?"
mechanism:
sip:bob@example.com?Accept-Contact=*%3bmobility%3d%22mobile%22
The previous URI requests the Reply-Recipient to add the following
header field to a reply MESSAGE request to be sent to
bob@example.com: Accept-Contact: *;mobility="mobile"
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6. Procedures at the Reply-Recipient
A Reply-Recipient that is able to receive and process MESSAGE
requests with a Reply-To header field and 'recipient-list' body MUST
include a 'multiple-reply' option-tag in a Supported header field
when responding to OPTIONS requests.
A Reply-Recipient that receives a MESSAGE request with a Reply-To
header field and 'recipient-list' body processes it and responds
following the precedure in section 7 of RFC 3428 [3]
There are two possibilities for Reply-Recipient to send reply MESSAGE
requests to intended recipients:
o The Reply-Recipient creates a reply MESSAGE request for each entry
in the URI-List and send them respectively. If it supports
'recipient-list-history' Content-Disposition type it MAY provide a
'recipient-list-history' body in the reply MESSAGE requests for
each intended recipient following the procedure defined in Copy
Control Attribute [8] .
o The Reply-Recipient sends a reply MESSAGE request that includes
the payload along with the URI-list to the MESSAGE URI-list
service [9] to distribute the simliar reply MESSAGE requests to
each of the URIs included in the list. The Reply-Recipient MAY
modify the URI-list from Reply-Issuer to add or remove recipients.
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7. Examples
7.1. Reply-Recipient use MESSAGE URI-List service to send reply MESSAGE
requests
Figure 1 shows an example flow where a Reply-Issuer sends a MESSAGE
request with Reply-To header field pointing to a URI list to a Reply-
Recipient. The Reply-Recipient sends a reply MESSAGE with the URI
list to MESSAGE URI-list service.
+--------+ +--------+ +---------+ +--------+ +--------+
| Reply- | | Reply- | | MESSAGE | | reply | | reply |
| Issuer | | Recip. | | URI-List| | target | | target |
| | | | | server | | 1 | | 2 |
+--------+ +--------+ +---------+ +--------+ +--------+
| | | | |
| F1:MESSAGE with Reply-To pointing to a URI-List |
|------------>| | | |
| F2:200 OK | | | |
|<------------| | | |
| | F3:MESSAGE | | |
| |-------------->| | |
| | F4:202 Accepted | |
| |<--------------| | |
| | | F5:MESSAGE | |
| | | --------------->| |
| | | F6:MESSAGE | |
| | | -------------------------->|
| | | F8:200 OK | |
| | |<--------------- | |
| | | F9:200 OK | |
| | |<-------------------------- |
| | | | |
Figure 1: Example flow for Reply-To pointing to multiple addresses
Figure 2 shows an example of the MESSAGE request F1, which carries a
'multipart/mixed' body composed of two other bodies:
o 'text/plain' body: contains the instant message payload;
o 'application/resource-lists+xml' body: contains the intended
recipients receving the reply MESSAGE request from Reply-
Recipient.
The Reply-To header field has the same value of Content-ID pointing
to the URI-List which contains the intended recipients.
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MESSAGE sip:tom@example.com SIP/2.0
Via: SIP/2.0/TCP uac1.example.com
;branch=z9hG4bKhjhs8as34sc
Max-Forwards: 70
To: <sip:tom@example.com>
From: Alice <sip:alice@example.com>;tag=210342
Call-ID: 39s02sdsl20d9sj2l
CSeq: 1 MESSAGE
Reply-To: <cid:cn35t8jf02@example.com>
Require: multiple-reply
Content-Type: multipart/mixed;boundary="boundary1"
Content-Length: xxx
--boundary1
Content-Type: text/plain
Please reply the deadline to the team!
--boundary1
Content-Type: application/resource-lists+xml
Content-Disposition: recipient-list
Content-ID: <cn35t8jf02@example.com>
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cp="urn:ietf:params:xml:ns:copycontrol">
<list>
<entry uri="sip:bill@example.com" cp:copyControl="to" />
<entry uri="sip:randy@example.net" cp:copyControl="to"
cp:anonymize="true"/>
<entry uri="sip:eddy@example.com" cp:copyControl="to"
cp:anonymize="true"/>
<entry uri="sip:joe@example.org" cp:copyControl="cc" />
<entry uri="sip:carol@example.net" cp:copyControl="cc"
cp:anonymize="true"/>
<entry uri="sip:ted@example.net" cp:copyControl="bcc" />
<entry uri="sip:andy@example.com" cp:copyControl="bcc" />
</list>
</resource-lists>
--boundary1--
Figure 2: MESSAGE with Reply-To header field pointing to a URI list
Figure 3 shows an example of the MESSAGE request F3, which carries a
'multipart/mixed' body composed of three other bodies:
o 'text/plain' body: contains the instant message payload;
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o 'application/resource-lists+xml' body: contains the list of
recipients. This list is the same with F1.
MESSAGE sip:list-service.example.com SIP/2.0
Via: SIP/2.0/TCP uac1.example.com
;branch=z9hG4bKhjhs8as34sc
Max-Forwards: 70
To: MESSAGE URI-list Service <sip:list-service.example.com>
From: Alice <sip:alice@example.com>;tag=32331
Call-ID: d432fa84b4c76e66710
CSeq: 1 MESSAGE
Require: multiple-reply, recipient-list-message
Content-Type: multipart/mixed;boundary="boundary1"
Content-Length: xxx
--boundary1
Content-Type: text/plain
The deadline is 14:00 GMT Octobor 10, 2007.
--boundary1
Content-Type: application/resource-lists+xml
Content-Disposition: recipient-list
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cp="urn:ietf:params:xml:ns:copycontrol">
<list>
<entry uri="sip:bill@example.com" cp:copyControl="to" />
<entry uri="sip:randy@example.net" cp:copyControl="to"
cp:anonymize="true"/>
<entry uri="sip:eddy@example.com" cp:copyControl="to"
cp:anonymize="true"/>
<entry uri="sip:joe@example.org" cp:copyControl="cc" />
<entry uri="sip:carol@example.net" cp:copyControl="cc"
cp:anonymize="true"/>
<entry uri="sip:ted@example.net" cp:copyControl="bcc" />
<entry uri="sip:andy@example.com" cp:copyControl="bcc" />
</list>
</resource-lists>
--boundary1--
MESSAGE request received at the MESSAGE URI-list server
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8. Security Considerations
URI-lists may contain private information, such as SIP URIs. It is
therefore not desirable that these URI-lists are known by third
parties. Eavesdroppers are able to watch URI-lists contained in SIP
requests unless the SIP message is sent over a secured channel, by
using any of the available SIP mechanisms, such as Transport Layer
Security (TLS) [5] , or unless the URI-list body itself is encrypted
with, e.g., S/MIME [6] . Therefore, it is RECOMMENDED that URI-list
bodies are encrypted with S/MIME [6] or that the SIP request is
encrypted with TLS [5] or any other suitable encryption mechanism.
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9. IANA Considerations
This document defines the 'multiple-reply' SIP option-tag. It should
be registered in the Option Tags subregistry under the SIP parameter
registry. The following is the description to be used in the
registration.
+------------------------+------------------------------+-----------+
| Name | Description | Reference |
+------------------------+------------------------------+-----------+
| multiple-reply | The body contains the | [RFC XXXX]|
| | inten contains the intended | |
| | recipients receving the | |
| | reply MESSAGE request from | |
| | Reply-Recipient. | |
+------------------------+------------------------------+-----------+
Figure 4: Registration of the 'multiple-reply' Option-Tag in SIP.
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10. Acknowledges
TBD
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11. MIME Information
TBD
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12. References
12.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[2] 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.
[3] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and
D. Gurle, "Session Initiation Protocol (SIP) Extension for
Instant Messaging", RFC 3428, December 2002.
[4] Camarillo, G. and A. Roach, "Framework and Security
Considerations for Session Initiation Protocol (SIP) Uniform
Resource Identifier (URI)-List Services",
draft-ietf-sipping-uri-services-06 (work in progress),
September 2006.
[5] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
Protocol Version 1.1", RFC 4346, April 2006.
[6] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions
(S/MIME) Version 3.1 Message Specification", RFC 4346, January
1999.
[7] Rosenberg, J., "Extensible Markup Language (XML) Formats for
Representing Resource Lists", RFC 4826, May 2007.
[8] Garcia-Martin, M. and G. Camarillo, "Extensible Markup Language
(XML) Format Extension for Representing Copy Control Attributes
in Resource Lists",
draft-ietf-sipping-capacity-attribute-04.txt (work in
progress), December 2006.
12.2. Informative References
[9] Garcia-Martin, M. and G. Camarillo, "Multiple-Recipient MESSAGE
Requests in the Session Initiation Protocol (SIP)",
draft-ietf-sip-uri-list-message-01.txt (work in progress),
January 2007.
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Appendix A. History of change
This is the first version of this draft.
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Authors' Addresses
Qian Sun
Huawei Technologies
Bantian Longgang
Shenzhen, Guandong 518129
P.R China
Phone: +86 755 28780808
Email: sunqian@huawei.com
Linyi Tian
Huawei Technologies
Bantian Longgang
Shenzhen, Guandong 518129
P.R China
Phone: +86 755 28780808
Email: tianlinyi@huawei.com
Daqi Ren
Huawei Technologies
Bantian Longgang
Shenzhen, Guandong 518129
P.R China
Phone: +86 755 28780808
Email: rendaqi@huawei.com
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