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

Roman Shpount <roman@telurix.com> Tue, 10 January 2017 20:35 UTC

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From: Roman Shpount <roman@telurix.com>
Date: Tue, 10 Jan 2017 15:35:12 -0500
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To: Paul Kyzivat <paul.kyzivat@comcast.net>
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Subject: Re: [MMUSIC] JSEP Issue #394: What appears in m= lines.
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On Tue, Jan 10, 2017 at 2:27 PM, Paul Kyzivat <paul.kyzivat@comcast.net>
wrote:

> On 1/10/17 1:08 PM, Roman Shpount wrote:
>
>> 1. When c= line is set to "IN IP4 0.0.0.0" and m= line is set to port 9,
>> so that these lines carry no valid address information as it is
>> specified in JSEP, protocol should be UDP/DTLS/SAVPF for RTP
>> or UDP/DTLS/SCTP for data
>>
>
> To do this cleanly, IMO there should be no singling out of IP4. The fact
> is that in this case the c= line is not needed. (And this isn't the only
> case where it isn't. It also isn't needed for MSRP and for websockets -
> things that use URLs in attributes instead of c=.) So perhaps we should
> revise 4566bis to make c= optional for m= lines where it isn't needed. Or
> define a new addrtype for use in c= (e.g. simply "IP" or "IP4/6") and
> define a placeholder address value for this case. For example:
>
>   c=IN IP -


It is cleaner, but this needs to be defined somewhere. Current JSEP uses
"IN IP4 0.0.0.0" and port 9.

2. When c= line and m= line carry valid address information, protocol
>> should match the candidate specified in c= and m= lines.
>>
>> 3. In cases when c= line and m= line carry valid address
>> information, when initial offer and answer are generated, they must
>> include UDP candidates and UDP candidates must be used as defaults. Once
>> ICE nomination process is complete, only the active candidate pair MUST
>> be included in SDP, and the transport for the active pair must be used.
>>
>
> I think this could be handled by having different <proto> values:
>
> ICE/DTLS      DTLS over either UDP or TCP
> ICE/UDP/DTLS  DTLS over only UDP
> ICE/TCP/DTLS  DTLS over only TCP
>
> ICE/DTLS/RTP/SAVPF      Like above, but for RTP/SAVPF
> ICE/UDP/DTLS/RTP/SAVPF  "
> ICE/TCP/DTLS/RTP/SAVPF  "
>
> So this allows restricting the type of candidates that are allowed, or
> not. And it avoids "lying" about the type that is to be used.
>

We can define it this way, but I am not sure defining anything beyond
ICE/DTLS/RTP/SAVPF and ICE/DTLS/SCTP is actually needed. Once we specify
that ICE is used, actual candidates can be examined to see which candidate
types are supported.

Regards,
_____________
Roman Shpount