Re: [MMUSIC] Issue #27: Allow RTP attributes in non-media m= sections

Christer Holmberg <> Thu, 16 February 2017 19:49 UTC

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From: Christer Holmberg <>
To: Taylor Brandstetter <>
Thread-Topic: [MMUSIC] Issue #27: Allow RTP attributes in non-media m= sections
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Date: Thu, 16 Feb 2017 19:49:35 +0000
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Subject: Re: [MMUSIC] Issue #27: Allow RTP attributes in non-media m= sections
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>> Yes, I meant "not" :)
> I can't find this restriction in the current draft of BUNDLE. Also, this restriction would make BUNDLE even more complex and 
> non-future-proof (suppose some future protocol that can be bundled with RTP also has its own TRANSPORT attributes). What 
> are the reasons for this restriction? Shouldn't endpoints ignore attributes they don't expect? "If an attribute is received that is 
> not understood, it MUST be ignored by the receiver."
It's not a BUNDLE restriction. The question is whether it's a restriction in the specs defining the parameters.

If there is no restriction, then there should be no issue to begin with. 

If there is a restriction, then the question is whether we would need to update the specs defining the parameters.

>> OR, we change the mux category for the RTP-specific parameters. But, that of course means they have to be added to every RTP m= section.
> That wouldn't make sense in my opinion. If rtcp-rsize wasn't a transport-level attribute, then multiple bundled m= sections would 
> be allowed to use different values for it. It's fundamentally a transport-level attribute.

I agree. The question is whether it's allowed to place the attribute in a non-RTP m= section.



On Thu, Feb 16, 2017 at 10:07 AM, Christer Holmberg <> wrote:
Yes, I meant "not" :)

Sent from my iPhone

On 16 Feb 2017, at 18.59, Eric Rescorla <> wrote:

On Thu, Feb 16, 2017 at 9:07 AM, Christer Holmberg <> wrote:
>The basic issue is that it's possible to have a situation where you have both
>media and data m= sections but the BUNDLE tag is associated with the data
>m= section and now you need to put the TRANSPORT and IDENTICAL
>attributes somewhere. The JSEP editors discussed this and came to the
>conclusion that it should go with the BUNDLE tag (i.e., in the data m= section)
>and that BUNDLE should forbid this, but it requires a change to BUNDLE.
Did you mean to say that BUNDLE should NOT forbid this?
Based on your GitHub discussion, my understanding is that you want to allow to include RTP-specific parameters (‘rtcp-mux’, ‘rtcp’, ‘rtcp-mux-only’ attributes etc) in the data m= section.

To repeat what I said on GitHub:
This has been discussed in the past, and the outcome has been to now allow RTP-specific parameters in non-RTP m= sections.

Do you mean "not" rather than now?

A solution would be to simply change the bundle tag when the RTP m= sections are added.
…OR, we change the mux category for the RTP-specific parameters. But, that of course means they have to be added to every RTP m= section.

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