Re: [Wish] 2nd WG Last Call for draft-ietf-wish-whip

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

On Tue, Jan 9, 2024 at 5:03 PM Christer Holmberg <
[e-mail]> wrote:

> Hi,
>
>
>
> The following issue has been discussed between myself and Sergio in:
>
>
>
> https://github.com/wish-wg/webrtc-http-ingest-protocol/issues/163
>
>
>
> However, I bring it to the list because I think it would be useful to get
> wider community input and guidance.
>
>
>
> WHIP uses the SDP trickle-ice-sdpfrag content type for ICE restarts.
> However, RFC 8838 only defines usage of trickle-ice-sdpfrag for trickle
> ICE. With SIP, an ICE restart triggers a new SDP renegotiation.
>
>
>
> Now, AFAIK the justification of WHIP using PATCH with trickle-ice-sdpfrag
> also for ICE restart (instead of POST with a new SDP offer),  is the
> statement in Section 3, saying that SDP renegotiations are not supported.
>
>
>
>         “It is important to note that SDP renegotiations are not
>
>           supported in WHIP, meaning that no modifications to the "m="
> sections
>
>           can be made after the initial SDP offer/answer exchange via
> HTTP POST
>
>           is completed and only ICE related information can be updated
> via HTTP
>
>           PATCH requests as defined in Section 4.1.”
>
>
>
> Q1: SDP renegotiation is more than the “m=” sections. There is also the
> session-level information, e.g., the “c=” section, the “o=” section etc.
> So, I think the text needs to talk about what INFORMATION can/cannot be
> updated.
>
>
>
Nothing can be changed except what we explicitly allowed in the 4.1. ICE
support section. I don't think we should make a list of what can and can't
be changed here, especially given that some of that info has the spec in
different RFCs which we may conflict with.


> Q2: Related to Q1, the text says that ICE related information can be
> updated. But, if the “m=” section cannot be updated, does that also mean
> that the IP port in the host candidate cannot be updated, as that it
> typically the port value also used in the “m=” section? Again, I think it
> is better to explicitly describe what information can be updated.
>
>
>

I disagree, it would be easy to contradict what is specified on another
rfcs. We could even be more precise and change the " and only ICE related
information can be updated" by " and only certain ICE related information
can be  updated"


> Q3: Related to Q1 and Q2, it needs to be clear what information the WHIP
> session can return in the PATCH response in case of an ICE restart. Can the
> WHIP session change the port number of its host candidate? Etc.
>

As we are adding ICE restart in this draft, I agree that we should be more
precise about the construction of the PATCH response. Do you have any
suggestions? I will try to create a PR for that.

Best regards
Sergio