水妖的专栏

Figure 2.1 shows the SIP message exchange between two SIP-enabled devices. The two devices could be SIP phones, hand-helds, palmtops, or cell phones. It is assumed that both devices are connected to a

SIP allows two end points to establish media sessions with each other. The main signaling functions of the protocol are as follows:Location of an end point;Contacting an end point to determine willing