| 单词 | H.323 |
| 释义 | H.323 The ITU-T Recommendation for multimedia communications over packet networks.The rec- ommendation addresses service over local area networks (LANs), but extends to the Internet and other IP-based networks. H.323 is not linked to any specific hardware device or operating system (OS) and, therefore, can be deployed in a wide variety of devices, including PCs, telephone sets, cable modems, and set-top boxes. H.323 supports multicast communications, thereby avoiding the requirement for specialized multipoint control units (MCUs) in a network where routers assume the responsibility for packet replicating.Version 2 1998) provides a means for encryption, includes mechanisms for call transfer and call forward, supports URL-style addresses, and provides the ability for endpoints to set quality of service (QoS) levels through Resource Reservation Protocol (RSVP). The four major components specified for H.323 include terminals, gateways, gatekeepers, and MCUs. • Terminals are the client endpoint devices on the LAN. All terminals must support voice, but data and video are optional. H.245 must be supported for negotiation of channel usage and capability. Q.931 is required for signaling and control. The Registration/Admission/Status (RAS) protocol 74570c08.qxd 9/11/07 12:21 PM Page 219 |