Subject: [SIP] why is contact header mandatory invites and positive responses?

From: Juha Heinanen <[email-masked]>
Date: Fri, 12 Jan 2001 09:47:39 +0200 (EET)

to me it doesn't make sense that contact header is mandatory in invites
and positive responses.  

in cases where the company policy is that sip messages must go via a
given proxy (that then relays them to/from uas within the company
network), the contact header gives wrong information to the other party.
the semantics of contact header "it provides a URL where the user can be
reached for further communications" simply are not true in such a
situation.

i would not care otherwise, but i have already met three commercial sip
user agents that inspite of the record route in the messages, still send
their acks to the address in the contact header instead of that in the
record-route.

unless the contact header can't be made optional also in invites and
positive oks, i would very strongly urge that the sip bakeoffs and call
flow documents would include test cases to check the correct ua behavior
in the presense of both record-route and contact header.

-- juha

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