I have been looking at RFC3515 and have found the following:
Section 2.2 contains the table of headers supported in the REFER method and contains the following:
Header Where REFER
…
Expires R o
Section 2.4.4 "Using SIP Events to Report the Results of the Reference" contains the following paragraph:
Notice that unlike SUBSCRIBE, the REFER transaction does not contain
a duration for the subscription in either the request or the
response. The lifetime of the state being subscribed to is
determined by the progress of the referenced request. The duration
of the subscription is chosen by the agent accepting the REFER and is
communicated to the agent sending the REFER in the subscription's
initial NOTIFY (using the Subscription-State expires header
parameter). Note that agents accepting REFER and not wishing to hold
subscription state can terminate the subscription with this initial
NOTIFY.
Which part of the RFC is correct ?
What happens if a REFER does contain an Expires header ?
Should the Expire duration included in the REFER be used in preference to the time which would be allocated by the agent receiving the REFER as described in 2.4.4 ?
If the Expire duration is "0" is this equivalent to using the Refer-sub header being set to false ?
Ian Elz
Office: + 44 24 764 35256
gsm: +44 7801723668
ian.elz at ericsson.com
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