Re: [MMUSIC] JSEP Issue #394: What appears in m= lines.

Magnus Westerlund <magnus.westerlund@ericsson.com> Tue, 10 January 2017 15:44 UTC

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To: Harald Alvestrand <harald@alvestrand.no>, <mmusic@ietf.org>
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From: Magnus Westerlund <magnus.westerlund@ericsson.com>
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Date: Tue, 10 Jan 2017 16:44:22 +0100
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Subject: Re: [MMUSIC] JSEP Issue #394: What appears in m= lines.
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Den 2017-01-02 kl. 14:42, skrev Harald Alvestrand:
> Den 22. des. 2016 18:30, skrev Eric Rescorla:
>>      __
>>
>>     Okay, I agree that having any rules for what you should offer here
>>     based on what the actual outcome is not the best idea here. I think
>>     the rules should be based on capability and intent. So if you only
>>     are going offer TCP candidates, then you clearly should use TCP/…,
>>
>>
>> I'm going to push on this. If we've already agreed that mismatches are
>> normal, why should we do that? Wouldn't it be better to just effectively
>> deprecate this field?
>>
>
> Concur with EKR.
>
> This field (the TCP/UDP part of the protocol field) was defined in a way
> that makes its original purpose (to negotiate profiles) not only
> impossible while using ICE, but actively harmful, because you end up
> telling lies in very many cases, so people will have to accept things
> that don't match reality.
>
> Make the world as simple for implementors as possible: Send a fixed
> string, and accept all strings.
>

Okay, can we please be precise with what is suggested here. Because what 
you write above, and what EKR proposed is not really the same thing. The 
issue proposed that it was fine to set either of the strings. You saying 
a fixed string. I want to ask you which UDP/... or TCP/..., or even 
ICE/DTLS/RTP/SAVPF?

 From a strict clarity issue using ICE/... would be my preferred. But, 
that is probably going to throw some implementations, especially 
gateways. It will also require us to actually go write the registration 
to explain what it is.

Using UDP is likely the most compatible and will only fail in gateway 
cases where there are no UDP candidates and the gateway fail to pick 
that up.

Using TCP when there are no TCP candidates are equally misleading to 
gateway cases.

The above is why I proposed that implementation capabilities and any 
configuration to limit what functions being used would be an appropriate 
choice.

I hope at least we can agree that an JSEP Answer MUST use the PROTO 
string of the OFFER?

Cheers

Magnus Westerlund

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