This document discusses guidelines for supporting RTCP end-to-end in Back-to-Back User Agents (B2BUAs). It has been updated since a previous presentation in London, with changes to references and terminology, additional discussion of RTCP packet types, guidelines on handling the SDP 'rtcp' attribute, and clarification of the impact of media security. There is also an attempt to map the STRAW taxonomy of B2BUA types to the RTP topologies framework, though this mapping could be further discussed. Feedback is sought on these updates and any other aspects requiring additional work.

1. Guidelines to support RTCP end-to-end in
Back-to-Back User Agents (B2BUAs)
draft-ietf-straw-b2bua-rtcp-01
Lorenzo Miniero (lorenzo@meetecho.com)
Victor Pascual (victor.pascual@quobis.com)
Sergio Garcia Murillo (sergio.garcia.murillo@gmail.com)
July 25th, 2014
STRAW Meeting Session, IETF 90, Toronto

2. A reminder
Deliverable
A document defining the requirements for B2BUAs to support RTCP
end-to-end submitted to the IESG as PS
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 2 / 9

3. What has changed?
Several changes after London
Updated references and terminology
Added more RTCP packet types
Added guideline on SDP ’rtcp’ attribute
Added discussion on impact of media security
Only partly changed
Attempted mapping to RTP topologies
More on that in separate discussion later...
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 3 / 9

4. References and Terminology
Updated both
Aligned with Taxonomies RFC [RFC7092]
Added RTP Topologies [RFC5117]
[I-D.ietf-avtcore-rtp-topologies-update]
Terminology improved
Probably still needs some work, though
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 4 / 9

5. RTCP Packet Types
More packet types (from IANA) added to Media-Aware section
Extended Reports (XR) [RFC3611]
SSRCs, as usual
begin seq and end seq in Report Blocks, if needed
Receiver Summary Information (RSI) [RFC5760]
SSRCs, as usual
Same attention for Collision Sub-Report Block
Port Mapping (TOKEN) [RFC6284]
SSRCs, as usual
More?
Other types needed?
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 5 / 9

6. SDP ’rtcp’ Attribute
Added discussion on SDP ’rtcp’ Attribute
Mentioned in London as common cause of B2BUA malfunctions
If present, it MUST be replaced
If not present, it SHOULD be provided to avoid ambiguity
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 6 / 9

7. Media Security
Clarified that Media Security can have an impact
SRTP/SRTCP prevents modification of RTP headers and RTCP
packets
Not an issue for Media-unaware Relays
... as long as the SDP is not messed up with, of course
Can be an issue for Media-aware Relays and Terminators
Manipulating RTP headers not an option
Hashing of RTP packets would be violated
RTCP packets could not be updated accordingly
Only way is to act as MITM
Unprotect SRTP/SRTCP, modify what necessary, protect again
Keying stuff to be updated in SDP with own info, of course
End-to-end security lost as part of the process
More on that in the DTLS-SRTP draft
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 7 / 9

8. Preparing the ground...
STRAW Taxonomies vs. RTP Topologies still an open issue
Not a problem strictly related to this draft?
Separate discussion in next presentation
Nevertheless, attempted a simple mapping
Media Relay ←→ RTP Transport Translator
Media-aware Relay ←→ RTP Translator
Media Terminator ←→ RTP Media Translator
Is this enough?
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 8 / 9

9. Questions? Comments?
Lorenzo Miniero IETF 90 - STRAW-RTCP July 25th
2014 9 / 9