This is addressed in the UAS side of REGISTER handling. See Section 10.3 Processing REGISTER Requests
6. The registrar checks whether the request contains the Contact header field. If not, it skips to the last step. If the Contact header field is present, the registrar checks if there ....... 8. The registrar returns a 200 (OK) response. The response MUST contain Contact header field values enumerating all current bindings. Each Contact value MUST feature an "expires" parameter indicating its expiration interval chosen by the registrar. The response SHOULD include a Date header field. Thanks Neel -----Original Message----- From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of Karthik.v Sent: Thursday, December 31, 2015 1:22 AM To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] Registration doubt in SIP. Hi , if contact header is optional in REGISTER request then, multiple TO header can be sent to register multiple contact ? As per my knowledge, To header should not be multiple then why it has been said in RFC 3261 that contact header is optional in Register. Thanks, Karthik V _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors