Subject: [siprec] FIR vs. SIP INFO

From: "Charles Eckel (eckelcu)" <[email-masked]>
Date: Thu, 20 Mar 2014 21:04:22 +0000

To the best of my knowledge, this is the last open item in the protocol
draft. Here is the info from the slide presented at IETF 89 in London:

FIR and SIP INFO requirements in SRC and/or SRS
------------------------
Section 8.1.7.1.1 SIP INFO for FIR
¨"XML Schema for Media Control² [RFC5168
<http://tools.ietf.org/html/rfc5168>] defines an Extensible Markup
Language (XML) Schema for video fast update. Implementations are
discouraged from using the method described except for backward
compatibility purposes. Implementations SHOULD use FIR messages instead.

NENA ICE-8 event feedback, do we need to say more? Options:
1.SRC MUST support both and provide interworking to what SRS supports (and
an UA that does not support both MUST NOT use SIPREC?)
2.SRS MUST support both (and allow SRC to support both simultaneously? And
how do you negotiation that ?)
3.Provide recommendations and leave as quality of implementation decision
(and live with interoperability issues?)
-----------------------------

Discussion in room (from minutes:
http://www.ietf.org/mail-archive/web/siprec/current/msg03934.html)
- Paul K - no brainer, SRS is the powerful box - that is the place to put
requirements - 2 is preferable to 1 - 2 vs. 3, I'm not sure, kind of
inclined for 2 but not sure
- Chair: definitive is best for implementation
- Charles: option 3 is my suggestion (as the draft is), but could live
with option 2 - would appreciate some help with the text - need to think
about use cases - if a UA is capable of dealing with both, it can simplify
for the SRS, but depends on capabilities of the SRC and SRS - if we can do
better that is great
- Chair: let's have more list discussion because missing people - but in
favour of documenting one and generally in favour of having the server do
the work - tentatively think going in the direction of option 2

Thoughts?

Cheers,
Charles

---

From: "Ram Mohan R (rmohanr)" <[email-masked]>
Date: Fri, 21 Mar 2014 03:03:38 +0000

I prefer option 2 as mandatory since SRS is the one that eventually looks
at the media being recorded(RTP) and is the best one to decide on whether
to generate a FIR or SIP INFO.  However we may also allow a SRC to
generate a FIR/SIP INFO. So I prefer that we can keep MUST for option 2
and MAY for option 1.

I have a slightly different question on this -
Do we want SRS(or SRC) to always generate both FIR and SIP INFO ? There
may be cases where endpoint (UA) may support one or both of them. If a UA
supports both of them it may result in a case where UA may re-transmit IDR
frame twice (one on receipt of FIR and other on on receipt of SIP INFO).
This is ok in principle but may lead to more network congestion due to
bursty traffic. Is this some thing we should worry about ?

Perhaps if there is a way SRS/SRC can find what method the UA prefers (FIR
or SIP INFO) it can only generate that.

Ram

-----Original Message-----
From: "Charles Eckel   (eckelcu)" <[email-masked]>
Date: Friday, 21 March 2014 2:34 am
To: "[email-masked]" <[email-masked]>
Subject: [siprec] FIR vs. SIP INFO

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