Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-channel - "a=setup" versus "a=dcsa:x setup"
Paul Kyzivat <pkyzivat@alum.mit.edu> Wed, 21 October 2015 15:43 UTC
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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Date: Wed, 21 Oct 2015 11:43:46 -0400
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Subject: Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-channel - "a=setup" versus "a=dcsa:x setup"
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On 10/9/15 10:03 AM, Juergen Stoetzer-Bradler wrote: > Hello, > > An MSRP over data channel related SDP media description will have a > media level "a=setup:<role>" attribute and may additionally > contain an "a=dcsa" encapsulated setup attribute "a=dcsa:x > setup:<role>". Current version draft-ietf-mmusic-msrp-usage-data-channel-02 > does not yet have any text related to the setup attribute except for > listing it as potential dcsa encapsulated MSRP specific attribute. > As the media level "a=setup" attribute is used to negotiation the DTLS > and SCTP establishment roles, and as the setup attribute is also used > in MSRP over TCP cases to negotiate the "active" role of MSRP session > endpoints (RFCs 6135, 6714) we propose to explicitly describe > the semantics of dcsa encapsulated setup attributes for MSRP over data > channel in draft-ietf-mmusic-msrp-usage-data-channel. IMO it makes perfect sense to separate out the negotiation of the msrp role via a=dcsa setup. That still leaves a=setup overloaded, for both SCTP setup and DTLS setup. There really ought to be separate negotiation of those two. Thanks, Paul > We propose to add a new section 5.1.1.3 "Media Description Level setup > Attribute Versus Data Channel Specific setup Attribute" > after section 5.1.1.2 ("Use of dcsa Attribute") and to extend existing > section 6 ("Gateway Configuration") with setup attribute related procedures. > > Would the following new section 5.1.1.3 and modified section 6 be agreeable? > > Thanks, > Juergen > > Proposed new Section 5.1.1.3: > > 5.1.1.3. Media Description Level setup Attribute Versus Data Channel > Specific setup Attribute > > The SDP setup attribute, as introduced in [RFC4145], can be used in > WebRTC data channel related SDP media descriptions as a media level > attribute, which is directly associated with the corresponding DTLS/ > SCTP "m" line. In this case the setup attribute is of the form > "a=setup:<role>", where <role> assumes values as defined in > [RFC4145]. Such a setup attribute is then used as specified in > [I-D.ietf-mmusic-sctp-sdp] in order to negotiate the establishment > roles of the DTLS connection and the SCTP association. > > Additionally, the setup attribute can be embedded in a dcsa attribute > and hence can explicitly be associated with an MSRP session over a > specific data channel. In such a case it is of the form "a=dcsa:x > setup:<role>", with x being the data channel's SCTP stream > identifier. Such a dcsa attribute embedded setup attribute has no > relationship with the DTLS connection and SCTP association > establishment roles. > > dcsa attribute embedded setup attributes are OPTIONAL for MSRP > sessions over data channels. > > If an MSRP over data channel description contains a dcsa embedded > setup attribute, then this embedded setup attribute is used to > negotiate, which MSRP session endpoint assumes the active role as per > Section 4.2.2 of [RFC6135] and Section 5.4 of [RFC4975]. > > If an MSRP over data channel description does not contain a dcsa > embedded setup attribute, then the media description level "a=setup" > attribute, which is associated with the data channel's DTLS > connection and SCTP association, is used to negotiate, which MSRP > session endpoint assumes the active role. > > If an MSRP over data channel endpoint wants to negotiate an active or > non-active MSRP session establishment role, which is different from > its DTLS connection and SCTP association establishment role, then it > MUST include a dcsa embedded setup attribute for this MSRP session. > In this case this dcsa embedded setup attribute's value is different > from the value of the DTLS/SCTP "m" line's "a=setup" attribute. > > > Proposed modified section 6: > > 6. Gateway Configuration > > This section describes the network configuration where one MSRP > endpoint uses data channels as MSRP transport, the other MSRP > endpoint uses TLS/TCP connections as MSRP transport, and the two MSRP > endpoints interwork via an MSRP gateway. > > Specifically, a gateway can be configured to interwork an MSRP > session over a data channel with a peer that does not support data > channel transport in one of two ways. In one model, the gateway > performs as a MSRP B2BUA to interwork all the procedures as necessary > between the endpoints. No further specification is needed for this > model. > > Alternately, the gateway can use CEMA procedures to provide transport > level interworking between MSRP endpoints using different transport > protocols as follows. > > When the gateway performs transport level interworking between MSRP > endpoints, all of the procedures in Section 5 apply to each peer, > with the following additions: > > o The endpoint establishing an MSRP session using data channel > transport SHALL NOT request inclusion of any relays, although it > MAY interoperate with a peer that signals the use of relays. > > o The gateway receiving an SDP offer that includes a request to > negotiate an MSRP session on a data channel can provide transport > level interworking in the same manner as a CEMA SBC by forwarding > TCP or TLS transport parameters in a new "m" line with the > appropriate attributes within the forwarded SDP offer. > > * If the received data channel side SDP offer contains a dcsa > embedded setup attribute for the to be negotiated MSRP session, > then the gateway interworks this dcsa embedded setup attribute > with the media description level "a=setup" attribute of this > MSRP session's "m" line in its forwarded SDP offer. > > * If the received data channel side SDP offer does not contain a > dcsa embedded setup attribute for the to be negotiated MSRP > session, then the gateway interworks the media description > level "a=setup" attribute, which is directly associated with > the data channel's DTLS/SCTP "m" line, with the media > description level "a=setup" attribute of this MSRP session's > "m" line in its forwarded SDP offer. > > o Similarly, a gateway receiving an SDP offer to negotiate an MSRP > session using TCP or TLS transport with an endpoint that only > supports data channel transport for MSRP can provide transport > level interworking in the same manner as a CEMA SBC by > establishing a new data channel for the MSRP session with the > target endpoint. > > * In this case the gateway interworks the TCP or TLS associated > media description level "a=setup" attribute of the to be > negotiated MSRP session's received "m" line either with the > media description level "a=setup" attribute of the data > channel's DTLS/SCTP "m" line, or with the dcsa embedded setup > attribute of this MSRP session's new data channel. > > * If the gateway's DTLS connection and SCTP association > establishment role on its data channel side is equal to the > "a=setup" attribute's value of the received MSRP over TCP or > TLS "m" line, then the gateway MAY add a dcsa embedded setup > attribute to the description of the MSRP session's new data > channel in its generated data channel side offer. > Alternatively, in this case the gateway MAY omit adding such a > dcsa embedded setup attribute to the description of the MSRP > session's new data channel in its generated data channel side > offer. Otherwise, if the gateway's DTLS connection and SCTP > association establishment role is different from the MSRP over > TCP or TLS associated received "a=setup" attribute's value, > then the gateway MUST add a dcsa embedded setup attribute to > the description of the MSRP session's new data channel in its > generated data channel side offer. > > * If the gateway adds a dcsa embedded setup attribute associated > with this MSRP session to its data channel side SDP offer, then > the value of this embedded setup attribute MUST be equal to the > value of the "a=setup" attribute, which is associated with this > MSRP session's "m" line in the received TCP or TLS side SDP > offer. > > > _______________________________________________ > mmusic mailing list > mmusic@ietf.org > https://www.ietf.org/mailman/listinfo/mmusic >
- [MMUSIC] draft-ietf-mmusic-msrp-usage-data-channe… Juergen Stoetzer-Bradler
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christer Holmberg
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Juergen Stoetzer-Bradler
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christer Holmberg
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Schwarz, Albrecht (Albrecht)
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christer Holmberg
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christian Groves
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Paul Kyzivat
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christer Holmberg
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christer Holmberg
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Christian Groves
- Re: [MMUSIC] draft-ietf-mmusic-msrp-usage-data-ch… Juergen Stoetzer-Bradler