What if the signalling is not ISUP?
The short answer is that you have to bring the signalling to the call agent, which has indeed to be programmed with adequate software. If the call agent understands, for example, Q.931, it can use SGCP to program the handling of trunks according to Q.931 signalling. The gateway does not even have to know that whether the signalling was Q.931 or ISUP. • A single call agent for an entire network? You must be kidding! Well, even in the most bell-shaped dreams, nobody really thinks that a single server can control the whole telephone network. The call agent can indeed be implemented as a distributed system, using proprietary solutions. There is no standard yet for CA-CA communication. One can however use H.323 or SIP. • Could we support multimedia terminals? Yes. SGCP uses the Session Description Protocol standard to document the characteristics of a connection. The current gateways are strictly for telephony and only use the audio components of SDP. But SDP was designed to support multime
