0120 Adding Bindings

   The REGISTER request sent to a registrar includes the contact

   address(es) to which SIP requests for the address-of-record should be

   forwarded.  The address-of-record is included in the To header field

   of the REGISTER request.

The Contact header field values of the request typically consist of

   SIP or SIPS URIs that identify particular SIP endpoints (for example,

   "sip:carol@cube2214a.chicago.com"), but they MAY use any URI scheme.

   A SIP UA can choose to register telephone numbers (with the tel URL,

   RFC 2806 [9]) or email addresses (with a mailto URL, RFC 2368 [32])

   as Contacts for an address-of-record, for example.

 

   For example, Carol, with address-of-record "sip:carol@chicago.com",

   would register with the SIP registrar of the domain chicago.com.  Her

   registrations would then be used by a proxy server in the chicago.com

   domain to route requests for Carol's address-of-record to her SIP

   endpoint.

 

   Once a client has established bindings at a registrar, it MAY send

   subsequent registrations containing new bindings or modifications to

   existing bindings as necessary.  The 2xx response to the REGISTER

   request will contain, in a Contact header field, a complete list of

   bindings that have been registered for this address-of-record at this

   registrar.

 

   If the address-of-record in the To header field of a REGISTER request

   is a SIPS URI, then any Contact header field values in the request

   SHOULD also be SIPS URIs.  Clients should only register non-SIPS URIs

   under a SIPS address-of-record when the security of the resource

   represented by the contact address is guaranteed by other means.

   This may be applicable to URIs that invoke protocols other than SIP,

   or SIP devices secured by protocols other than TLS.

 

   Registrations do not need to update all bindings.  Typically, a UA

   only updates its own contact addresses.