Re: [Perc] Request for decision review

[Emil Ivov <[e-mail]>]

On 16.05.16 г. 16:01, Adam Roach wrote:
> On 5/16/16 14:42, Emil Ivov wrote:
>> I would officially like to ask the PERC WG to review the decision for
>> immutable SSRCs.
>>
>> At this point, after the many conversations on the topic, it sounds
>> like no one would really have a problem with SSRCs being mutable.
>
> Cullen's message on May 10th called out some specific, hard problems in
> the PERC system -- problems that don't arise in non-PERC systems, like
> ensuring the focus doesn't engage in intentional misattribution. Keeping
> the SSRCs immutable prevents these problems.
>
> If you would like to engage in a discussion of allowing SSRCs to change,
> it seems that it is first necessary for someone to figure out alternate
> means of solving those problems.
>
> The people who don't agree with the need to allow the focus to change
> SSRCs aren't going to be very motivated to come up with those solutions,
> so it would seem that those people insisting that they be mutable --
> i.e., you -- are on the hook for coming up with something viable. What
> do you propose?

That makes sense.

Cullen's mail asks about how we handle RTCP. I already answered this: 
it's always terminated. I am not sure I see where the problem lies here.

The second problem mentioned by Cullen on May 10 is the one about 
splicing that's also described here:
https://tools.ietf.org/html/draft-mattsson-perc-srtp-cloud-01#section-7.2.4

This can be resolved by simply having an rtp-hdrext attached and signed 
by the sender that carries the original SSRC. That part will not be 
allowed to change and needs to be copied over by the MDD/SFU together 
with the rests of the immutable parts.

If we need the same thing in RTCP, we add a similar extension there.

How does that work for everyone?

Emil



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