Re: [MMUSIC] WGLC for draft-ietf-mmusic-data-channel-sdpneg

Christian Groves <> Thu, 26 November 2015 00:39 UTC

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From: Christian Groves <>
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Subject: Re: [MMUSIC] WGLC for draft-ietf-mmusic-data-channel-sdpneg
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Hello Juergen, all,

I have reviewed the document and I don't think there are any major 
issues preventing it from going forward. My comments below:

General: Double check acronyms are spelled out on first use, e.g. SCTP, SDP
General: Sometimes "subprotocol" is used, sometimes "sub-protocol" I 
guess we should be consistent.

Sect.1: The 2nd sentence seems confusing. I propose to reword "RTCWeb 
allows applications to use data channels. It RTCWeb defines an in-band 
DCEP however other in-band or out-of-band protocols may be used for 
establishing datachannels.

Sect.5.1.1: (defined in Section 4 ), this should probably be section 3?

Sect.5.1.1 1st para last sentence: Reliability is now two parameters: 
max-retr & max-time

Sect.5.1.1 1st para last sentence: Priority is not defined by the syntax 
however its part of DCEP. Do we need to add this?

Sect. "maxretr-value" should we actually add an ABNF value for 
this? The referred to draft doesn't have ABNF. Its a 2 byte integer

Sect. "maxtime-value" should we actually add an ABNF value for 
this? The referred to draft doesn't have ABNF. Its a 2 byte integer

Sect. The example for a=dcmap:4, wouldn't this be invalid as it 
contains both the max-time and max-retr parameters?

Sect.5.2.3, pg.14, 7th bullet: "Closes any created data channels for 
which the expected "a=dcmap:" and "a=dcsa:" attributes  are not present 
in the SDP answer." Should this also refer to section 5.2.4 on closure?

Sect.5.2.5: The miscellaneous section doesn't explicitly cover the case 
when a=dcmap is missing but a=dsca is included. I take it that its an 
error. Should we add this?

Sect.6 1st para under fig.2: "So, the offerer should  close the ..." is 
this really a "MUST close"? There is text about reusing a data channel 
but does it apply in this case when no previous data channel has been 

Sect.6 bottom pg.18: "Continuing on the earlier example in Figure 1" Is 
this a continuation of figure 2? The text below figure 3 indicates that 
MSRP SCTP stream ID 2 is removed. This is example 2.

Sect.8.2.2: DCSA appropriate values. Now defined in sect.

Sect.11.2: There are no usages of RFCs 4975, 4976, 5547, 6135 and 6714 
in the document. These can be deleted.

Sect.11.2: There are no usages of RFC6455 and I-D.ietf-rtcweb-jsep the 
document other than in the changes section. These can be deleted.

Minor editorials: Sent offline to author.

Regards, Christian

On 25/11/2015 8:52 PM, Bo Burman wrote:
> This is to announce a 4 week Working Group Last Call for
> draft-ietf-mmusic-data-channel-sdpneg-06
> as proposed standard.
> Please review and provide any comments you may have on the document by 
> Wednesday, December 23, 2015. Comments should be sent to the document 
> authors and the MMUSIC WG list. If you review the document but do not 
> have any comments, please send a note to that effect as well.
> Please also forward this WGLC call to any other interested parties who 
> may be able to review the draft, asking them to also direct their 
> comments to the authors and the list as above.
> Thank you!
>         Bo Burman (MMUSIC co-chair)
> Draft information:
> This draft is a work item of the Multiparty Multimedia Session Control 
> Working Group of the IETF.
>         Title           : SDP-based Data Channel Negotiation
> Authors : Keith Drage
> Maridi R. Makaraju (Raju)
> Juergen Stoetzer-Bradler
> Richard Ejzak
>                           Jerome Marcon
>                 Filename        : 
> draft-ietf-mmusic-data-channel-sdpneg-06.txt
>                 Pages           : 37
>                 Date            : 2015-10-19
> Abstract:
>    The Real-Time Communication in WEB-browsers (RTCWeb) working group is
>    charged to provide protocols to support direct interactive rich
>    communications using audio, video, and data between two peers' web-
>    browsers.  For the support of data communication, the RTCWeb working
>    group has in particular defined the concept of bi-directional data
>    channels over SCTP, where each data channel might be used to
>    transport other protocols, called sub-protocols.  Data channel setup
>    can be done using either the in-band Data Channel Establishment
>    Protocol (DCEP) or using some out-of-band non-DCEP protocol.  This
>    document specifies how the SDP offer/answer exchange can be used to
>    achieve such an out-of-band non-DCEP negotiation.  Even though data
>    channels are designed for RTCWeb use initially they may be used by
>    other protocols like, but not limited to, the CLUE protocol.  This
>    document is intended to be used wherever data channels are used.
> The IETF datatracker status page for this draft is:
> There's also a htmlized version available at:
> A diff from the previous version is available at:
> Internet-Drafts are also available by anonymous FTP at:
> _______________________________________________
> mmusic mailing list