TABLE OF CONTENTS This section identifies nomenclature used in describing the SIP protocol.
Address-of-Record: An Address-Of-Record (AOR) is a SIP or SIPS URI that points to a domain with a location service that can map the URI to another URI where the user might be available. Typically, the location service is populated through registrations. An AOR is frequently thought of as the "public address" of the user.
Back-to-Back User Agent: A Back-to-Back User Agent (B2BUA) is a logical entity that receives a request and processes it as a User Agent Server (UAS). In order to determine how the request should be answered, it acts as a User Agent Client (UAC) and generates requests. Unlike a proxy server, it maintains dialog state and must participate in all requests sent on the dialogs it has established. Since it is a concatenation of a UAC and UAS, no explicit definitions are needed for its behavior.
Call: A call is an informal term that refers to some communication between peers, generally set up for the purposes of a multimedia conversation.
Call Leg: Another name for a dialog; no longer used in this specification.
Call Stateful: A proxy is call stateful if it retains state for a dialog from the initiating INVITE to the terminating BYE request. A call stateful proxy is always transaction stateful, but the converse is not necessarily true.
Client: A client is any network element that sends SIP requests and receives SIP responses. Clients may or...
