Re: [Perc] Drop support for E2E RTP header extensions

[Sergio Garcia Murillo <[e-mail]>]

On 24/04/2017 22:57, Nils Ohlmeier wrote:
>
>> On Apr 24, 2017, at 08:57, Sergio Garcia Murillo 
>> <[e-mail] 
>> <mailto:[e-mail]>> wrote:
>>
>> RTP header extensions are negotiated on the SDP O/A, so not all 
>> endpoints may support same header extension, and even if they support 
>> same set of extensions, they may be negotiated with different ids. So 
>> it is impossible to support RTP header extensions E2E except in the 
>> scenario in which all endpoints support same subset of extensions and 
>> happens to be negotiated with same id.
>
> The topic of header extensions has been discussed in the past at the 
> first perc interim meeting on 2016-01-11. I suggest reading the 
> meeting minutes and materials from that meeting: 
> https://datatracker.ietf.org/group/perc/meetings/
> It appears at the time discussion on RTCP had not concluded yet. But I 
> don’t think that the conclusion of doing RTCP hop-by-hop only changes 
> substantially the arguments to allow end-to-end header extensions.
>
> I assume nobody disagrees that negotiating end-to-end header extension 
> is not easy. But it is purely a signaling problem. I don’t see a 
> technical reason why the media plane should dis-allowed it.
> As it is a signaling issue it also means that every PERC conferencing 
> solution is free to remove end-to-end header extension from the 
> signaling if it wants to make it’s life easier.
>

Let me recap:

  * We don't have an use case for E2E rtp header extensions
  * We don't provide a solution for signaling E2E rtp header extensions
    vs HBH ones
  * We don't provide a solution on how to successfully signal/handling
    different subsets of rtp header extensions and unify the negotiated ids
  * We introduce a new concept of rtp header ordering that is not
    defined anywhere and is not supported by anyone currently making
    implementation much more difficult
  * We don't expect anyone implementing it

Really, I don't see any reason why we have to keep support for E2E rtp 
header extensions.

Regards
Sergio