Relay Extensions for the Message Sessions Relay Protocol (MSRP)
RFC 4976
Network Working Group C. Jennings
Request for Comments: 4976 Cisco Systems, Inc.
Category: Standards Track R. Mahy
Plantronics
A. B. Roach
Estacado Systems
September 2007
Relay Extensions for the Message Session Relay Protocol (MSRP)
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
Two separate models for conveying instant messages have been defined.
Page-mode messages stand alone and are not part of a Session
Initiation Protocol (SIP) session, whereas session-mode messages are
set up as part of a session using SIP. The Message Session Relay
Protocol (MSRP) is a protocol for near real-time, peer-to-peer
exchanges of binary content without intermediaries, which is designed
to be signaled using a separate rendezvous protocol such as SIP.
This document introduces the notion of message relay intermediaries
to MSRP and describes the extensions necessary to use them.
Jennings, et al. Standards Track [Page 1]
RFC 4976 MSRP Relays September 2007
Table of Contents
1. Introduction and Requirements ...................................3
2. Conventions and Definitions .....................................4
3. Protocol Overview ...............................................4
3.1. Authorization Overview ....................................11
4. New Protocol Elements ..........................................11
4.1. The AUTH Method ...........................................11
4.2. The Use-Path Header .......................................12
4.3. The HTTP Authentication "WWW-Authenticate" Header .........12
4.4. The HTTP Authentication "Authorization" Header ............12
4.5. The HTTP Authentication "Authentication-Info" Header ......12
4.6. Time-Related Headers ......................................12
5. Client Behavior ................................................13
5.1. Connecting to Relays Acting on Your Behalf ................13
5.2. Sending Requests ..........................................18
5.3. Receiving Requests ........................................18
5.4. Managing Connections ......................................18
6. Relay Behavior .................................................18
6.1. Handling Incoming Connections .............................18
6.2. Generic Request Behavior ..................................19
6.3. Receiving AUTH Requests ...................................19
6.4. Forwarding ................................................20
6.4.1. Forwarding SEND Requests ...........................21
6.4.2. Forwarding Non-SEND Requests .......................22
6.4.3. Handling Responses .................................22
6.5. Managing Connections ......................................23
7. Formal Syntax ..................................................23
8. Finding MSRP Relays ............................................24
9. Security Considerations ........................................25
9.1. Using HTTP Authentication .................................25
9.2. Using TLS .................................................26
9.3. Threat Model ..............................................27
9.4. Security Mechanism ........................................29
10. IANA Considerations ...........................................31
10.1. New MSRP Method ..........................................31
10.2. New MSRP Headers .........................................31
10.3. New MSRP Response Codes ..................................31
11. Example SDP with Multiple Hops ................................31
12. Acknowledgments ...............................................32
13. References ....................................................32
13.1. Normative References .....................................32
13.2. Informative References ...................................33
Appendix A. Implementation Considerations ........................34
Jennings, et al. Standards Track [Page 2]
RFC 4976 MSRP Relays September 2007
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