Rohan Mahy

1
draft-ietf-sip-join andSemantics of REFER

• Rohan Mahy
• rohan_at_cisco.com

2
Join Header Status

• Join draft finished WGLC last week
• ZERO comments Does anyone care?
• No open issues
• Whos read it?
• Whos implemented it?
• Whos planning to implement it?

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Semantics of REFER

• RFC 3515 says it is OK to put almost any
  arbitrary URI in a Refer-To header
• arbitrary schemes
• specific SIP methods
• in or out of a dialog
• preloaded SIP headers
• What does that mean?
• How do I authorize this?

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What semantics make sense?

• REFER in a dialog, Refer-To methodINVITE
• REFER outside dialog, Refer-To methodINVITE
• REFER with other methods REGISTER, SUBSCRIBE,
  MESSSAGE
• Nested REFERs
• Refer-To lthttp//gt (targeted to dialog)
• Refer-To lthttp//gt (not to a dialog)
• Refer-To ltsipuser_at_foo.comresponse486gt

Transfer Click to Dial Move Sub Remote
Transfer Fetch content Send Busy
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How do you put REFER requests in a context?

• Option 1 Send REFER on existing dialog
• Option 2 Use a separate GRUU per conversation.
  (This gets cumbersome very fast. Requires lots
  of target refresh requests.)
• Option 3 Use explicit Refer-To header
  parameters
• Refer-To lthttp//foo.com/gtcall-id123
• remote-tagabclocal-tagxyz

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How do we proceed?

• Most uses of REFER other than transfer are
  unlikely to work on todays UAs
• Suggest that we define semantics of cohesive
  baskets of REFER functionality. Use option-tags
  to make sure these are supported.
• Propose that we add the explicit dialog
  parameters to Refer-To header
• Provide guidance to what extent is remote call
  control, and remote UI invocation (app
  interaction) OK.