■ ITU-T Recommendation H.323 describes an infrastructure of terminals, common control components, services, and protocols that are used for multimedia communications.
■ Functional components of H.323 include terminals, gateways, gatekeepers, Cisco UBEs, and MCUs.
■ Calls can be established between endpoints, endpoints to gatekeepers, or gatekeepers to gatekeepers.
■ H.323 calls can occur with or without the use of a gatekeeper.
■ H.323 defines three types of multipoint conferences.
■ When configuring codecs, you can specify one codec or set up codec negotiation.
■ You might want to adjust some of the H.323 timers to meet network requirements.
■ You can use several commands to configure fax features on H.323 gateways.
■ DTMF relay solves the problemof DTMF distortion.
■ Use the show gateway command to verify H.323 gteway status.
■ MGCP defines an environment for controlling telephony gateways from a centrralized call agent.
■ MGCP components include endpoints, gateways, and call agents.
■ Calls and connections are basic concepts in MGCP.
■ MGCP call flow consists of an exchange of messages between a call agent and a gateway.
■ The mgcp command can be used to configure residential and trunk gateways on a Cisco router.
■ Several show and debug commands help to verify an MGCP configuration.
■ SIP is defined by IETF RFCs 2543 and 3261 and allows integration with third-party VoIP networks.
■ SIP is modeled on the interworking of UAs and network servers.
■ A SIP call flow consists of signaling and transmission of bearer and media packets.
■ Communication between SIP components uses a request and response message model.
■ A SIP address consists of an optional user ID, a host description, and optional parameters to qualify the address more precisely.
■ SIP call setup models include direct, proxy server, and redirection.
■ You can use several commands on Cisco IOS to configure SIP on Cisco IOS routers.
■ You can use several commands on Cisco IOS to verify and troubleshoot a SIP integration.