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Feature Tags with SIP REFER draft-ietf-sip-refer-feature-param-00

Feature Tags with SIP REFER draft-ietf-sip-refer-feature-param-00 . Orit Levin oritl@microsoft.com Alan Johnston ajohnston@tello.com. Status from IETF-63. Concerns were expressed about which feature tags should be included in REFERs Positions ranged from:

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Feature Tags with SIP REFER draft-ietf-sip-refer-feature-param-00

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  1. Feature Tags with SIP REFER draft-ietf-sip-refer-feature-param-00 Orit Levin oritl@microsoft.com Alan Johnston ajohnston@tello.com SIP WG IETF64

  2. Status from IETF-63 • Concerns were expressed about which feature tags should be included in REFERs • Positions ranged from: • Only isfocus and a small set of other feature tags MAY be included • Every known feature tag SHOULD be included • The whole idea is useless • The draft hasn’t been updated since IETF-63 SIP WG IETF64

  3. Background Information • RFC 3840 “Indicating User Agent Capabilities in SIP” states that the feature tags are used in three distinct cases: • REGISTER requests and responses (means interactions with own server) • OPTIONS responses (means interactions with other UAs) • requests and responses that create dialogs (such as INVITE) (means interactions with other UAs) SIP WG IETF64

  4. Background Information – cont. • draft-ietf-sipping-callerprefs-usecases-05 provides guidance and examples for the feature tags usage: • In a REGISTER all feature tags (a long list including the SIP-related option tags and methods) are included • In a INVITE or 200 OK to OPTIONS only selective feature tags describing application capabilitiesare included SIP WG IETF64

  5. From Section 3.7.2 REGISTER sip:example.com SIP/2.0 To: sip:X@example.com Contact: <sip:X1@pc.example.com> ‘q=1.0 ;methods="INVITE,BYE,OPTIONS,ACK,CANCEL" ;uri-user="<X1>“ ;uri-domain="example.com“ ;audio ;schemes="sip,tel" ;mobility="fixed“ ;class="business" From Section 4.2 SIP/2.0 200 OK Contact: <sip:server33.example.com> ;msgserver ;automata ;attendant Examples from draft-ietf-sipping-callerprefs-usecases-05 SIP WG IETF64

  6. Proposal Part I • Clarify the feature tags usage in the core documents: • RFC 3840 which has the relevant IANA Section • Potentially update the draft-ietf-sipping-callerprefs-usecases-05 to include examples in accordance to the clarified usage SIP WG IETF64

  7. Proposal Part I - cont. • Considerations why it is NOT desirable to include all feature tags in the Contact • Message size for every creating dialog transaction • The non-application feature tags conveyed in the Contact header field are a duplication of the information conveyed in the following header fields: Supported, Allow, Allow-Events… SIP WG IETF64

  8. Proposal Part I - cont. • The suggested guideline • In a REGISTER all feature tags (a long list including the SIP-related option tags and methods) are included • In a INVITE or 200 OK to OPTIONS only selective feature tags describing application capabilitiesare included • More thinking and list discussions will be needed SIP WG IETF64

  9. Proposal Part II • The suggested text to draft-ietf-sip-refer-feature-param: “It is RECOMMENDED that the REFER-Issuer includes in the Refer-To header field all feature tags that were listed in the most recent Contact header field of the REFER-Target” SIP WG IETF64

  10. Backup Slides SIP WG IETF64

  11. Executive Summary • Motivation Make REFER requests more descriptive by explicitly allowing feature parameters to be included in the Refer-to • No IANA actions • Extension to RFC-3515 Refer-To = ("Refer-To" / "r") HCOLON ( name-addr / addr-spec ) * (SEMI refer-param) refer-param = generic-param / feature-param where feature-param is defined in Section 9 of RFC-3840 "Indicating UA Capabilities in SIP" SIP WG IETF64

  12. Example REFER sip:carol@chicago.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com;branch=z9hG4bKg45 Max-Forwards: 70 To: Carol <sip:carol@chicago.example.com> From: Alice <sip:alice@atlanta.example.com>;tag=5534562 Call-ID: 849392fklgl43 CSeq: 476 REFER Contact: <sip:uf313a413@example.com> Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY Accept: application/sdp, message/sipfrag Refer-To: <sip:3402934234@example.com>;isfocus Supported: gruu, … Content-Length: 0 SIP WG IETF64

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