Alternate Offers / Capabilities in Alternate Offers / Capabilities - PowerPoint PPT Presentation

Alternate Offers / Capabilities in Alternate Offers / Capabilities in SIP/SDP SIP/SDP draft-bhatia-mmusic-sdp-altcap-01.txt draft-bhatia-mmusic-sdp-altcap-01.txt Authors: Authors: Medhavi Bhatia Medhavi Bhatia John Oliver John Oliver {mbhatia, joliver}@nextone.com {mbhatia, joliver}@nextone.com

Problem: Three Categories Problem: Three Categories Caller allocates separate DSPs for separate codecs Caller allocates separate DSPs for separate codecs Caller cannot switch codecs at runtime Caller cannot switch codecs at runtime One of the offerred codecs needs to be transcoded on a separate IP One of the offerred codecs needs to be transcoded on a separate IP host and must be sent directly to it. host and must be sent directly to it. Media clipping is undesirable Media clipping is undesirable “FID” Semantics from RFC 3388 can be used with some extra SIP “FID” Semantics from RFC 3388 can be used with some extra SIP signaling. signaling. Newer versions of the same offer using encryption or SDPng Newer versions of the same offer using encryption or SDPng Carrier architectures: SIP at Core. H.323/SIP/Megaco at access. Carrier architectures: SIP at Core. H.323/SIP/Megaco at access. H.323 messaging needs to be transparently passed through the core, H.323 messaging needs to be transparently passed through the core, especially when called party is H.323. especially when called party is H.323.

Proposed Solution: Use of MIME multipart entities Proposed Solution: Use of MIME multipart entities Mandatory inclusion of Content-ID in each multipart entity Mandatory inclusion of Content-ID in each multipart entity Definition of a new MIME header: Content-Reference Definition of a new MIME header: Content-Reference Allows answerer to indicate which MIME body in the offer is Allows answerer to indicate which MIME body in the offer is being responded to being responded to Answerer must include one MIME body with Content- Answerer must include one MIME body with Content- Reference header when offerer uses MIME Reference header when offerer uses MIME multipart/alternative body multipart/alternative body

How does it look like ? How does it look like ? Content-Type: multipart/alternative; boundary= ’xxx’ Content-Type: multipart/alternative; boundary= ’xxx’ Offer --xxx --xxx Content-Type: application/sdp Content-Type: application/sdp Content-ID: <o100@spock.nextone.com> Content-ID: <o100@spock.nextone.com> Answer v=0 v=0 o=- 25678 753849 IN IP4 128.96.41.1 o=- 25678 753849 IN IP4 128.96.41.1 s= s= c=IN IP4 128.96.41.1 c=IN IP4 128.96.41.1 t=0 0 t=0 0 m=audio 3456 RTP/AVP 0 m=audio 3456 RTP/AVP 0 m=video 3458 RTP/AVP 31 m=video 3458 RTP/AVP 31 --xxx --xxx Content-Type: application/sdp Content-Type: application/sdp Content-Type: application/sdp Content-Type: application/sdp Content-Reference: <o100@spock.nextone.com>;answer Content-Reference: <o100@spock.nextone.com>;answer Content-ID: <o101@spock.nextone.com> Content-ID: <o101@spock.nextone.com> v=0 v=0 v=0 v=0 o=- 25678 753849 IN IP4 128.96.41.1 o=- 25678 753849 IN IP4 128.96.41.1 o=- 25678 753849 IN IP4 128.96.41.1 o=- 25678 753849 IN IP4 128.96.41.1 s= s= s= s= c=IN IP4 128.96.41.1 c=IN IP4 128.96.41.1 c=IN IP4 128.96.41.1 c=IN IP4 128.96.41.1 t=0 0 t=0 0 t=0 0 t=0 0 m=audio 49000 RTP/AVP 0 m=audio 49000 RTP/AVP 0 m=audio 3456 RTP/AVP 18 m=audio 3456 RTP/AVP 18 m=video 59000 RTP/AVP 31 m=video 59000 RTP/AVP 31 m=video 3458 RTP/AVP 34 m=video 3458 RTP/AVP 34 --xxx-- --xxx--

Proposed Solution: Use of MIME multipart entities Proposed Solution: Use of MIME multipart entities Other MIME multipart bodies allowed Other MIME multipart bodies allowed Answer can include multiple bodies too (Negotiated bodies) Answer can include multiple bodies too (Negotiated bodies) Subsequent exchanges must follow modification protocols Subsequent exchanges must follow modification protocols for individual bodies (like RFC 3264) and must have the for individual bodies (like RFC 3264) and must have the same number of negotiated bodies. same number of negotiated bodies.

Previous Version of draft -00.txt Previous Version of draft -00.txt Discussed multiple approaches: Discussed multiple approaches: “ALTS” semantics based on RFC 3388 “ALTS” semantics based on RFC 3388 “ATLC” semantics based on RFC 3388 “ATLC” semantics based on RFC 3388 - Very complex and does not extend easily - Very complex and does not extend easily - SDP based. Works for non MIME based protocols too - SDP based. Works for non MIME based protocols too MIME multipart/alternative w/o Content-Reference header MIME multipart/alternative w/o Content-Reference header - Answerer includes empty bodies to maintain positions of bodies. - Answerer includes empty bodies to maintain positions of bodies. - Not elegant - Not elegant Current approach (-01) address a much wider domain of Current approach (-01) address a much wider domain of problems and is simpler as well as elegant. problems and is simpler as well as elegant.

Issues Issues Changes to title / organization of draft ? Changes to title / organization of draft ? Work Group ? Work Group ? SIP Require header SIP Require header Extension parameters in Content-Reference header Extension parameters in Content-Reference header reference := "Content-Reference" ":" msg-id 1*(";" reference-parm) reference := "Content-Reference" ":" msg-id 1*(";" reference-parm) reference-parm := “answer” | extension-token reference-parm := “answer” | extension-token