Re: [bfcpbis] Eric Rescorla's Discuss on draft-ietf-bfcpbis-rfc4583bis-26: (with DISCUSS and COMMENT)

[Roman Shpount <[e-mail]>]

Hi Eric,

On Wed, Oct 24, 2018 at 4:45 PM Eric Rescorla <[e-mail]> wrote:

> On Wed, Oct 24, 2018 at 1:12 PM Roman Shpount <[e-mail]> wrote:
>
>> ICE SDP draft still requires a re-INVITE after nomination process is
>> completed where c= and m= line are updated to reflect the nominated
>> candidate. If nominated candidate an ICE-TCP candidate, then proto in m=
>> line would be 'TCP/DTLS/BFCP' to reflect this. In cases when non ICE-TCP
>> candidate is used, the proto in m= line will be 'UDP/TLS/BFCP'. Also, all
>> subsequent offer/answer exchanges, which do not initiate ICE restart are
>> supposed to use the proto value of nominated candidate in the m= line. So,
>> the only reason for existence of 'TCP/DTLS/BFCP' proto is to differentiate
>> if UDP or TCP candidate is used after the nomination.
>>
>
> I don't believe any WebRTC stack does this, and to the best of my
> knowledge, JSEP does not require it.
>
> Moreover, that's not how I read the ICE-SDP draft, at least as far as
> ICE-bis goes.
> https://tools.ietf.org/html/draft-ietf-mmusic-ice-sip-sdp-21#section-3.3.4
>
> "
>
>  However, If the support for 'ice2' ice-option is in use, the
>    nominated candidate is noted and sent in the subsequent offer/answer
>    exchange as the default candidate and no updated offer is needed to
>    fix the default candidate.
> "
>
> Updated offer is still present when ice2 is not used.

When ice2 is used, nominated candidate still ends us as default candidate
in the subsequent offer/answer exchanges, which means ICE-TCP candidate
ends up in the m= line.


> How did you solve this issue in JSEP? I was pretty sure
>> that 'TCP/RTP/DTLS/SAVP' and 'TCP/DTLS/SCTP' were used there for this
>> purpose, but I could have missed one of the updates.
>>
>
> For DTLS-SRTP, JSEP requires that you generate UDP/TLS/RTP/SAVPF
> regardless of the ICE candidates. Similarly, for datachannels, you must
> generate UDP.DTLS/SCTP.
>

I think this only covers the initial offer, but not the subsequent
exchanges.

Regards,
_____________
Roman Shpount