Re: [rtcweb] Open data channel issues

Christer Holmberg <> Wed, 26 February 2014 22:21 UTC

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From: Christer Holmberg <>
To: Paul Kyzivat <>, "" <>
Thread-Topic: [rtcweb] Open data channel issues
Date: Wed, 26 Feb 2014 22:21:38 +0000
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Subject: Re: [rtcweb] Open data channel issues
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>>> * Section 6.5
>>> This section contains:
>>     Data channels can be opened by using internal or external
>>     negotiation.  The details are out of scope of this document.
>>     A simple protocol for internal negotiation is specified in
>>     [I-D.ietf-rtcweb-data-protocol] and MUST be supported.
>>> But internal and external negotiation are not defined in this document.
>>  > I *thought* that internal negotiation was by definition negotiation 
>> by use of  > rtcweb-data-protocol. 
>> (draft-ejzak-mmusic-data-channel-sdpneg-00
>> thinks so too,
>>  > but calls it "in-band negotiation".) There should be a good 
>> definition of these  > terms, or reference to one. And more discussion 
>> if there can be other kinds of  > internal negotiation. (If so, how 
>> would one be chosen?)
>> Well, the text above says that ietf-rtcweb-data-protocol specifies an 
>> internal negotiation protocol, so it's not that far off.  The split 
>> does allow someone to use an alternative negotiation protocol 
>> (internal or external).
>> How about:
>>     Data channels can be opened by using negotiation within the SCTP 
>> association or external
>>     negotiation.  External negotiation is defined as any method which 
>> results in an agreement
>>     as to the parameters of a channel and the creation thereof.
>>     The details are out of scope of this document.
>>     A simple protocol for negotiation within the SCTP association is 
>> specified in
>>     [I-D.ietf-rtcweb-data-protocol] and MUST be supported.
>> Perhaps someone can wordsmith "external negotiation" better.
>ISTM the issue is that Internal vs. External isn't the key distinction. 
>What is key is that there is one method that MUST be *supported* but need not be the only one >used. Other mechanisms may be used. It doesn't really matter whether they are conducted >internally (over the SCTP association) or externally (anything else).

I think the MUST-be-supported-method is a separate question.

>E.g., I could use DCEP to establish one channel, and then use my own private protocol over that to >negotiate other channels. Would that be internal or external negotiation? Does it matter?

I guess they would both be in-band methods. Maybe using in-band and out-of-band terminology would be more clear - and more aligned with existing terminology.