[Wish] Proposal: Triggering ICE Restart

[Adam Roach <[e-mail]>]

During today's meeting, Jonathan raised a question about whether the 
currently proposed PATCH mechanism is sufficient for triggering ICE 
restarts. The issue is that ICE restarts result in a new generation of 
ICE candidates, which necessitates new ufrags and passwords on both sides.

Looking at RFC 5789, it's pretty clear that PATCH is intended as an 
optimization of PUT rather than its own independent operation (e.g. look 
closely at the final paragraph of section 2). So one semantically 
consistent approach to ice restart would be for WHIP clients to send a 
PUT with a new offer rather than simply PATCHing in new candidates.

This approach has a lot of appeal for me because it lines up well with 
the model that Jonathan was describing (where we're basically mapping 
WISH operations pretty directly to JSEP operations): in JSEP, ICE 
restarts result in the generation of a whole new offer rather than 
simply a set of candidates.

So how would we feel about using PUT with a full SDP offer on the WHIP 
resource URL for ICE restarts? (Alternatively, we could use POST on that 
URL for an offer/answer exchange, to keep it consistent with session 
initiation -- I see minor pros/cons each way, but nothing decisive)

/a