Re: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-11.txt

Many thanks, Christer and Raju for the comments so far.

On 23/07/19 04:37, Christer Holmberg wrote:
> One thing that needs to be clarified, however, is whether there should be a path attribute pointing to the peer data channel endpoint. I could not find much text on that in the draft. Section 4.4 talks about "the MSRP-URI that represents an MSRP data channel endpoint", but I can't find any text on how it is actually used.
Section 5.1.1.2 ("Use of the dcsa Attribute") specifies path as one of 
the attributes that can be used. It also clarifies that path attribute 
can not be used for transport establishment:
"As described in Section 5.1.2 the path attribute is not used for 
transport establiment."

How the path attribute is used is defined by RFC4975,  section 8.2. 
("URI Negotiations"), that states that the URI is used to determine 
transport parameters, protection level and "to identify the target when 
sending requests and responses.".
As this draft forbids the use of path parameter for transport 
establishment, then for data channel transport the URI can only be used 
"to identify the target when sending requests and responses.".
I believe an implementor can find this, I can add a short paragraph to 
clarify in next revision that would essentially replicate what it's 
already in RFC4975, what do you think?

> Regards,
>
> Christer
>
>
>
> -----Alkuperäinen viesti-----
> Lähettäjä: mmusic <mmusic-bounces@ietf.org> Puolesta Makaraju, Raju (Nokia - US/Naperville)
> Lähetetty: lauantai 13. heinäkuuta 2019 15.24
> Vastaanottaja: Jose M Recio <jose@ch3m4.com>; mmusic@ietf.org
> Aihe: Re: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-11.txt
>
>> [JM] Draft covers either direct connection to an endpoint or direct connection to a gateway. As middleboxes are out of scope in the connection using >data channel, then CEMA is out of scope. This short explanation currently appears as justification for saying that CEMA is out of scope. I can remove >the explanation and just state that CEMA is out of scope.
> [Raju] I agree with that.
>
>> For example, if the GW is implemented on an SBC, it can use CEMA
>> towars the inside network, using a non-dc transport. But not towards endpoints using data channel transport.
> [Raju] Let's please make this clear in the draft.
>
>> [JM] I agree for RCS should be like that. Would mandating this restrict applicability for other applications?
> [Raju] I agree that such design limitation should only be for RCS (self-imposed), but not for other applications.
>
> Thanks
> Raju
>
> -----Original Message-----
> From: mmusic <mmusic-bounces@ietf.org> On Behalf Of Jose M Recio
> Sent: Tuesday, July 9, 2019 8:23 AM
> To: mmusic@ietf.org
> Subject: Re: [MMUSIC] I-D Action: draft-ietf-mmusic-msrp-usage-data-channel-11.txt
>
>
> On 9/7/19 10:57 AM, Makaraju, Raju (Nokia - US/Naperville) wrote:
>> Do we need to make any further clarifications for the references to CEMA?
>> Section 5.1.1.2 has a sentence that is a little awkward, but seems to be saying the CEMA is out of scope.
> [JM] Draft covers either direct connection to an endpoint or direct connection to a gateway. As middleboxes are out of scope in the connection using data channel, then CEMA is out of scope. This short explanation currently appears as justification for saying that CEMA is out of scope. I can remove the explanation and just state that CEMA is out of scope.
>
>> But in section 6 for gateway function it mentions CEMA can be used.
> [JM] Draft supports gateways providing transport level interworking between MSRP endpoints using different transport protocols. CEMA can't be used towards the endpoints using data channel transport, but the GW could use CEMA to interwork with endpoints using other protocols.
>
> For example, if the GW is implemented on an SBC, it can use CEMA towars the inside network, using a non-dc transport. But not towards endpoints using data channel transport.
>
>> My understanding is I think section 6 suggests to use CEMA equivalent procedures without CEMA attributes!
> [JM] GW can use CEMA with endpoints using non-dc transports. This can be removed, but I think it would make the GW transport interwork option too restrictive. The B2BUA GW would not be affected.
>
>> Also, in section 6 should we add a further statement that the gateway assumes one MSRP data channel instance and one sub-protocol per SIP dialog as RCS mandates that a single SIP session/dialog has only one MSRP m= line?
>>
> [JM] I agree for RCS should be like that. Would mandating this restrict applicability for other applications?
>
>> Thanks
>> Raju
>>
>>
>> -----Original Message-----
>> From: mmusic <mmusic-bounces@ietf.org> On Behalf Of
>> internet-drafts@ietf.org
>> Sent: Saturday, June 1, 2019 11:22 PM
>> To: i-d-announce@ietf.org
>> Cc: mmusic@ietf.org
>> Subject: [MMUSIC] I-D Action:
>> draft-ietf-mmusic-msrp-usage-data-channel-11.txt
>>
>>
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the Multiparty Multimedia Session Control WG of the IETF.
>>
>>           Title           : MSRP over Data Channels
>>           Authors         : Keith Drage
>>                             Maridi R. Makaraju (Raju)
>>                             Juergen Stoetzer-Bradler
>>                             Richard Ejzak
>>                             Jerome Marcon
>>                             Jose M. Recio
>> 	Filename        : draft-ietf-mmusic-msrp-usage-data-channel-11.txt
>> 	Pages           : 19
>> 	Date            : 2019-06-01
>>
>> Abstract:
>>      This document specifies how the Message Session Relay Protocol (MSRP)
>>      can be instantiated as a data channel sub-protocol, using the SDP
>>      offer/answer exchange-based generic data channel negotiation
>>      framework.  Two network configurations are documented: a WebRTC end-
>>      to-end configuration (connecting two MSRP over data channel
>>      endpoints), and a gateway configuration (connecting an MSRP over data
>>      channel endpoint with an MSRP over TCP or TLS endpoint).
>>
>>
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-mmusic-msrp-usage-data-cha
>> nnel/
>>
>> There are also htmlized versions available at:
>> https://tools.ietf.org/html/draft-ietf-mmusic-msrp-usage-data-channel-
>> 11
>> https://datatracker.ietf.org/doc/html/draft-ietf-mmusic-msrp-usage-dat
>> a-channel-11
>>
>> A diff from the previous version is available at:
>> https://www.ietf.org/rfcdiff?url2=draft-ietf-mmusic-msrp-usage-data-ch
>> annel-11
>>
>>
>> Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org.
>>
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>>
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