Yes
________________________________
From: [email protected] [mailto:[email protected]] On
Behalf Of [email protected]
Sent: Monday, February 02, 2009 11:51 AM
To: [email protected]
Subject: [Sip] Is Contact Header mandatory in REFER message?
Hi,
Is it mandatory to have a Contact Header field in REFER message?
RFC 3261 SIP: Session Initiation Protocol
June 2002
8.1.1.8 Contact
The Contact header field provides a SIP or SIPS URI that can
be used
to contact that specific instance of the UA for subsequent
requests.
The Contact header field MUST be present and contain exactly
one SIP
or SIPS URI in any request that can result in the
establishment of a
dialog. For the methods defined in this specification, that
includes
only the INVITE request. For these requests, the scope of
the
Contact is global. That is, the Contact header field value
contains
the URI at which the UA would like to receive requests, and
this URI
MUST be valid even if used in subsequent requests outside of
any
dialogs.
If the Request-URI or top Route header field value contains a
SIPS
URI, the Contact header field MUST contain a SIPS URI as
well.
RFC 3515 The SIP Refer Method
April 2003
2. The REFER Method
REFER is a SIP method as defined by RFC 3261 [1]. The REFER
method
indicates that the recipient (identified by the Request-URI)
should
contact a third party using the contact information provided
in the
request.
Unless stated otherwise, the protocol for emitting and
responding to
a REFER request are identical to those for a BYE request in
[1]. The
behavior of SIP entities not implementing the REFER (or any
other
unknown) method is explicitly defined in [1].
A REFER request implicitly establishes a subscription to the
refer
event. Event subscriptions are defined in [2].
A REFER request MAY be placed outside the scope of a dialog
created
with an INVITE. REFER creates a dialog, and MAY be
Record-Routed,
hence MUST contain a single Contact header field value.
REFERs
occurring inside an existing dialog MUST follow the
Route/Record-
Route logic of that dialog.
Regards,
Sunil
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