Thanks Sanjay.
So, is the Contact Header mandatory for all SIP messages (Response and Requests)? Regards, Sunil ________________________________ From: Sanjay Sinha (sanjsinh) [mailto:[email protected]] Sent: Monday, February 02, 2009 2:18 PM To: Sunil Bhagat (WT01 - Telecom Equipment); [email protected] Subject: RE: [Sip] Is Contact Header mandatory in REFER message? 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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