Re: [MMUSIC] Faster ICE by role reversal?

[Jonathan Lennox <[e-mail]>]

On Jul 30, 2014, at 6:16 PM, Martin Thomson <[e-mail]> wrote:

> RFC 5245 states that the controlling peer is the offerer, period.
> This delays the start of nomination until the answer arrives.
> 
> What do folks think about an ICE option like the following?
> 
> The option is added to the offer to say: I'm OK if the answerer
> nominates.  The answerer echoes the option to indicate that it will
> nominate.
> 
> The answerer nominating would allow it to send a DTLS ClientHello and
> the USE-CANDIDATE check in immediate succession.  That removes the
> signaling return path from the session setup time when doing
> aggressive nomination.  And it would let us use Jonathan's "aggressive
> nomination without USE-CANDIDATE" technique all the time.  We could
> then effectively deprecate aggressive nomination, since there are no
> real latency gains to be had.
> 
> I've probably missed something critical here, so take this opportunity
> to tell me that I'm stupid.

The offerer can’t send its own connectivity checks until it receives an answer, because it needs the remote ufrag and password.  Without this, it doesn’t have any valid pairs, and so can’t send any media.

This suggestion might still save half an RTT, though? I’d need to work through a full ladder diagram to figure it out.