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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