Re: [Sip] Is Contact Header mandatory in REFER message?

Thanks Sanjay.

So, is the Contact Header mandatory for all SIP messages (Response and Requests)?

Regards,

Sunil

From: Sanjay Sinha (sanjsinh) [mailto:sanjsinh at cisco.com]
Sent: Monday, February 02, 2009 2:18 PM
To: Sunil Bhagat (WT01 - Telecom Equipment); sip at ietf.org
Subject: RE: [Sip] Is Contact Header mandatory in REFER message?

Yes

From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On Behalf Of sunil.bhagat at wipro.com
Sent: Monday, February 02, 2009 11:51 AM
To: sip at ietf.org
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