W3C home > Mailing lists > Public > public-webrtc@w3.org > August 2017

Re: BUNDLE nightmare when first media section becomes inactive

From: Taylor Brandstetter <deadbeef@google.com>
Date: Thu, 24 Aug 2017 15:58:28 -0700
Message-ID: <CAK35n0ZzJpzQsAZ0ejk12J=GQWo-jcs-Onm46uO3fHAkBAT9xA@mail.gmail.com>
To: Byron Campen <docfaraday@gmail.com>
Cc: IƱaki Baz Castillo <ibc@aliax.net>, "public-webrtc@w3.org" <public-webrtc@w3.org>
>
>  Right, the bundle spec does not tell us what to do here, which is a hole
> in that spec. When you have trickle ICE, it is currently impossible for the
> offerer to indicate which ICE transport it intends to reuse where, because
> the c-line is not necessarily stable.


Yeah, the BUNDLE spec is written with the assumption that the transport can
be identified by an address, which is not true for ICE, where it's
identified by a ufrag instead. I tried to fix this and other problems here (
https://github.com/cdh4u/draft-sdp-bundle/pull/19), but unfortunately I got
involved too late and my proposed changes didn't make it into the spec.

2. Some way for the offerer to unambiguously signal which transport it
> wants to use for each bundle/lone m-section, that does not rely on the
> c-line. Maybe some sort of tag for each transport.


I assumed the ufrag could be used as this "tag".


On Thu, Aug 24, 2017 at 1:46 PM, Byron Campen <docfaraday@gmail.com> wrote:

> On 8/24/17 3:14 PM, Taylor Brandstetter wrote:
>
> If you stopped the _transceiver_, then the offerer and answerer would need
>> to recognize that the original bundle transport was gone, and to establish
>> a new one, in the same manner as they would with an initial offer/answer,
>> or adding a new m-section that isn't bundled.
>
>
> I don't think this is correct. From the perspective of the BUNDLE spec,
> this is "Disabling A Media Description In A BUNDLE Group" (section 8.5.4).
> There's a note that specifically addresses this scenario:
>
>    NOTE: If the removed "m=" line is associated with the previously
>>    selected BUNDLE-tag, the offerer needs to suggest a new BUNDLE-tag
>>    [Section 8.2.1].
>
>
> Note that this only says you need to select a new BUNDLE-tag, not a new
> address.
>
>
>     Right, the bundle spec does not tell us what to do here, which is a
> hole in that spec. When you have trickle ICE, it is currently impossible
> for the offerer to indicate which ICE transport it intends to reuse where,
> because the c-line is not necessarily stable. Therefore, we need one of two
> things:
>
> 1. Specific rules about what transports are reused when. Absent any such
> rules, "transport follows m-section" is the simplest assumption.
>
> or
>
> 2. Some way for the offerer to unambiguously signal which transport it
> wants to use for each bundle/lone m-section, that does not rely on the
> c-line. Maybe some sort of tag for each transport.
>
> Best regards,
> Byron Campen
>
Received on Thursday, 24 August 2017 22:58:52 UTC

This archive was generated by hypermail 2.3.1 : Monday, 23 October 2017 15:19:51 UTC