Re: [MMUSIC] BUNDLE Weekly Summary: Assumptions

Paul Kyzivat <> Fri, 10 May 2013 22:21 UTC

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Date: Fri, 10 May 2013 18:21:17 -0400
From: Paul Kyzivat <>
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Subject: Re: [MMUSIC] BUNDLE Weekly Summary: Assumptions
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On 5/10/13 6:05 PM, Eric Rescorla wrote:

>      > 2.       SDP m- lines with a zero port value MUST NOT be put
>     inside a BUNDLE group (not in an offer, nor in an answer). There
>     will be a note indicating that, due to this, the number of m- lines
>     associated with a BUNDLE group may differ between the offer and the
>     associated answer. There will also be a note indicating that this is
>     due to RFC 5888, in case people later start to wonder where the
>     “MUST NOT” comes from.
>     object to this. I think EKR's idea of doing this explicitly in an
>     offer to indicate that the line is only being offered in a bundle is
>     a good one.
> I'm sorry to be slow today, but can you point me to the specific MUST
> NOT in RFC 5888.

Section 9.2:

    SIP entities refuse media streams by setting the port to zero in the
    corresponding "m" line. "a=group" lines MUST NOT contain
    identification-tags that correspond to "m" lines with the port set to

While this is stated in the context of answers, the statement itself 
seems unqualified. And it would be pretty silly if you could do it in 
the offer and not in the answer.