Re: [MMUSIC] RID update (draft-pthatcher-mmusic-rid-01,> )

Adam Roach <> Fri, 16 October 2015 16:42 UTC

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To: Paul Kyzivat <>,
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Date: Fri, 16 Oct 2015 11:41:57 -0500
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Subject: Re: [MMUSIC] RID update (draft-pthatcher-mmusic-rid-01,> )
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On 10/15/15 22:04, Paul Kyzivat wrote:
> * Section 7.1:
> In:
>  1. It MUST generate a 'rid-identifier' that is unique within a media
>     description
> IIUC, the rid-identifier must be unique within an RTP session, 
> including all the media descriptions pertaining to that RTP session.


     Note that 'rid's are only required to be unique within a media
     section ("m-line"); they do not necessarily need to be unique within
     an entire RTP session.  In traditional usage, each media section is
     sent on its own unique 5-tuple, which provides an unambiguous scope.
     Similarly, when using BUNDLE
     [I-D.ietf-mmusic-sdp-bundle-negotiation], MID values associate RTP
     streams uniquely to a single media description.

> * Section 7.2.2, item 2:
> Restating my earlier comment, why not simply check the PT against 
> those listed in the m-line? There could be default PTs in use that 
> have no rtpmap or fmtp. Those are only defined for audio, but there 
> *could* be rid constraints applied to audio. (I think max-br would 
> potentially be applicable. Or new ones might be defined that apply.) 
> At least it seems harmless to define it this way.

Updated to:

      ...payload types is verified against the list of valid payload types
         for the media section (that is, those listed on the "m=" line).
         If there is no match for the Payload Type listed in the "a=rid"
         line, then remove the "a=rid" line.

> * Section 7.4, item 4:
> I think there should be a check that the PTs in the answer are a 
> subset of those in the offer.


     4.  If the "a=rid" line contains a "pt=" parameter, the offerer
         verifies that the list of payload types is a subset of those sent
         in the corresponding "a=rid" line in the offer.

> (And, while it can be inferred, it might be good to state somewhere 
> that in cases where the answerer m-line PT values differ from those in 
> the offer, the PTs in the answer rid use the offerer's PT values.)


     Note: in the case that the answerer uses different PT values to
     represent a codec than the offerer did, the "a=rid" values in the
     answer use the PT values that were sent in the offer.