Re: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-10.txt - Comment on msrp-cema attribute

Christer Holmberg <> Sat, 27 April 2019 18:08 UTC

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From: Christer Holmberg <>
To: Jose M Recio <>, "" <>
Thread-Topic: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-10.txt - Comment on msrp-cema attribute
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Date: Sat, 27 Apr 2019 18:07:57 +0000
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Subject: Re: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-10.txt - Comment on msrp-cema attribute
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>> Keep in mind (and that should probably better described in the document) that the normal MSRP routing procedures don't apply. 
>> The MSRP messages will be routed in the data channel, which is established between the SIP peers (or whatever signaling protocol 
>> is used). I guess proxies and application servers can look at the top-most path attribute, but that is not going to be the primary routing 
>> input. I don't think the draft says anything about that - it just seems to assume that the data channel will end up in the intended MSRP peer.  
> It indeed assumes that the data channel endpoint will be a MSRP peer, either another endpoint or a MSRP GW. If that's not clear enough it should be made more explicit.

I was not talking about the fact that the endpoint will be a MSRP peer/GW, but that legacy MSRP routing will not be used.

> If the endpoint is a GW, messages can be relayed, similar to the scenario where the connection to the GW is done using TLS, or WebSockets, instead of dc.      

Regarding the GW, I think that also needs more text. For example, *IF* the data channel MSRP client inserts multiple path attributes, will the GW then copy paste those in the outgoing legacy MSRP message? I assume it will, but there is very little detail on the GW procedures.