Re: [MMUSIC] Is ice-mismatch media or session level?

[Suhas Nandakumar <[e-mail]>]

Hi Roman

Please go ahead with PR on that branch

Thanks
Suhas

On Sat, May 25, 2019 at 3:07 AM Roman Shpount <[e-mail]> wrote:

> Hi Suhas,
>
> I have looked at ice-mismatch branch and I think there is a slight
> confusion there between presence of a=ice-mismatch in the answer and ICE
> mismatch condition (ICE validation procedures failing for the answer).
>
> There are three distinct conditions when m= line in the answer is
> processed:
>
> In case a=ice-mismatch is included in only some m= lines out of several,
> ICE should not be used only for these specific m= lines and RFC 3264
> procedures should be followed instead for these m= lines only.
>
> In case if offerer did not include any ICE attributes (offerer does not
> support ICE) or if offerer included a=mismatch into all m= lines, ICE
> should be terminated for the entire sessions and RFC 3264 procedures should
> be followed instead for the whole session.
>
> In case if ICE validation procedures failed for one or more m= line in the
> answer (answerer detected ICE mismatch), the behavior is unspecified
> (answerer will likely terminate the session or emit a groan of unearthly
> pain and die) .
>
> Let me know if you want a pull request on this branch.
> _____________
>
> Roman Shpount
>
>
> On Mon, May 20, 2019 at 5:03 PM Roman Shpount <[e-mail]> wrote:
>
>> Hi All,
>>
>> Few comments about this:
>>
>> 1. Section 3.2.5 needs to be rewritten to specify that Verifying ICE
>> Support procedures is per m= line:
>>
>> First change old text:
>>
>> If this condition is not met, the agents MUST process the SDP based on
>> normal [RFC3264] procedures, without using any of the ICE mechanisms
>> described in the remainder of this specification with the few exceptions
>> noted below:
>>
>> First change new text:
>>
>> If this condition is not met, the agents MUST process the SDP *for the
>> media stream* based on normal [RFC3264] procedures, without using any of
>> the ICE mechanisms described in the remainder of this specification with
>> the few exceptions noted below:
>>
>> Second change old text:
>>
>> In some cases, controlling/initiator agent may receive the SDP answer
>> that may omit "a=candidate" attributes for the media streams, and instead
>> include a session level "a=ice-mismatch" attribute.  This signals to the
>> offerer that the answerer supports ICE, but that ICE processing was not
>> used for this session.  This specification provides no guidance on how an
>> agent should proceed in such a failure case.
>>
>> Second change new text:
>>
>> In some cases, controlling/initiator agent may receive the SDP
>> answer that may omit "a=candidate" attributes for the media *stream*,
>> and instead include a *media *level "a=ice-mismatch" attribute.
>> This signals to the offerer that the answerer supports ICE, but that
>> ICE processing was not used for this *media stream*.  In this case,  ICE
>> processing MUST be terminated for this media stream and SDP for this media
>> stream MUST be processed based on normal [RFC3264] procedures.
>>
>> 2. Section 3.3.3 says "If the answer does not indicate that the answerer
>> supports ICE, or if the offerer detects an ICE mismatch in the answer, the
>> offerer MUST terminate the usage of ICE". This needs to be clarified that
>> if "a=ice-mismatch" attribute is included in the m= line, ICE processing
>> MUST be terminated for this m= line only and this m= line MUST be processed
>> based on procedures described in RFC 3264. If "a=ice-mismatch" is included
>> in all m= lines in the answer, then ICE processing MUST be terminated for
>> the entire session.
>>
>> 3. We need to specify somewhere that a=ice-mismatch is only allowed in
>> the answer and MUST not be present in the offer.
>>
>> P.S. This would be much easier as a pull request but the repo is out of
>> date.
>> _____________
>> Roman Shpount
>>
>>
>> On Thu, May 16, 2019 at 4:28 PM Suhas Nandakumar <[e-mail]>
>> wrote:
>>
>>>
>>>
>>> On Thu, May 16, 2019 at 12:25 AM Christer Holmberg <
>>> [e-mail]> wrote:
>>>
>>>> Hi,
>>>>
>>>>
>>>>
>>>> >>>> I am inclined to leave it as media-level attribute. I am not sure
>>>> what more clarification is needed in the text today ?
>>>>
>>>> >>
>>>>
>>>> >>> Are the clarifications Roman suggested below already included ?
>>>>
>>>> >
>>>>
>>>> >> I am finding it hard to parse suggested clarification. I am sure I
>>>> am missing something.
>>>>
>>>> >
>>>>
>>>> > Roman suggested ice-mismatch should be defined for both media- and
>>>> session-level.
>>>>
>>>> >
>>>>
>>>> > Looking further at the current text, I'm not sure I agree since there
>>>> really isn't any normative behavior associated with receiving ice-mismatch.
>>>>
>>>> > Thus, I'd suggest simply keeping it as-is and media-level only.
>>>>
>>>>
>>>>
>>>> No matter whether it's session and/or media level, I still think there
>>>> needs to be normative behavior associated with receiving ice-mismatch.
>>>>
>>>>
>>>>
>>>> Section 5.4 of RFC 8445 says:
>>>>
>>>>
>>>>
>>>>    "Each using protocol needs to define whether the using protocol is
>>>>
>>>>    vulnerable to ICE mismatch, how ICE mismatch is detected, and
>>>> *whether*
>>>>
>>>> *   specific actions need to be taken when ICE mismatch is detected*."
>>>>
>>>
>>> [Suhas] RFC5245 never defined a normative behavior on how a ice-mismtach
>>> needs to be
>>> handled and I do agree with the intent there.
>>>
>>> ice-sip-sdp says this today
>>>
>>> Also to note, this specification provides no guidance on how an
>>>    controlling/initiator agent should proceed in scenarios where the the
>>>    SDP answer includes "a=ice-mismatch" from the peer.
>>>
>>>
>>> I am inclined to leave it as it is. RFC8445 doesn't mandate it either
>>> (referring to  *whether*
>>>
>>> *   specific actions need to be taken"*
>>>
>>>
>>>
>>>>
>>>> Regards,
>>>>
>>>>
>>>>
>>>> Christer
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Sun, May 12, 2019 at 8:41 PM Flemming Andreasen <mailto:
>>>> [e-mail]> wrote:
>>>>
>>>> Based on the errata, it seems like the intent was for to be
>>>> media-level. I'd suggest we keep it that way and add the clarifications you
>>>> outline below.
>>>>
>>>>
>>>>
>>>> If people feel otherwise, please speak up no later than May 19.
>>>>
>>>>
>>>>
>>>> Thanks
>>>>
>>>>
>>>>
>>>> -- Flemming (with chair hat on)
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 4/29/19 4:44 PM, Roman Shpount wrote:
>>>>
>>>> Hi Christer,
>>>>
>>>>
>>>>
>>>> Thank you for reviewing and responding.
>>>>
>>>>
>>>>
>>>> On Sat, Apr 27, 2019 at 1:48 PM Christer Holmberg <mailto:
>>>> [e-mail]> wrote:
>>>>
>>>> Before we just change something back we need to think what the reason
>>>> for the change to media-level was. Could it be related to RTCWEB?
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> This is definitely not RTCWEB related, since RTCWEB should never
>>>> generate ice-mismatch or use it for any reason.
>>>>
>>>>
>>>>
>>>> The ice-mismatch attribute was session only according to RFC 5245
>>>> Section 21..1.4 (https://tools.ietf.org/html/rfc5245#section-21.1.4).
>>>> At the same time, according to RFC 5245 Section 15..3 (
>>>> https://tools.ietf.org/html/rfc5245#section-15.3), ice-mismatch is
>>>> media level attribute only. This being said, according to RFC 5245 Section
>>>> 6.1 (https://tools.ietf.org/html/rfc5245#section-6.1), ice-mismatch
>>>> applies to the whole session, but it is specified per m= line. According to
>>>> errata 3149 (https://www.rfc-editor.org/errata/eid3149), ice-mismatch
>>>> should be media level. So, it is a bit of a mess.
>>>>
>>>>
>>>>
>>>> I can change ice-mismatch back to media level, but what we need to
>>>> clarify then is the following: If ice-mismatch is present in the m= line,
>>>> does it stop ICE processing for the whole session or for this m= line only?
>>>>
>>>>
>>>>
>>>> If it stops ICE processing for the whole session then it makes little
>>>> or no sense being specified per m= line. If it only stops processing for
>>>> specific m= line, then ice-mismatch probably also makes sense at the
>>>> session level to stop ICE processing for the whole session.
>>>>
>>>>
>>>>
>>>> I am definitely open to input here.
>>>>
>>>> _____________
>>>>
>>>> Roman Shpount
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>>
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>>>>
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>>>>
>>>>
>>>>
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>>>>
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