H.323

H.323 is a standard for communication protocols from the International Telecommunications Union Telecommunication Standardization Sector (ITU-T); Version 4 is the current version. H.323 was created to provide multimedia communication across a packet network. The protocol can handle video and data, in addition to audio. H.323 interoperates well with the public switched telephone network (PSTN) in translating between call setup and control signals used in an IP network and those used in a switched-circuit network. H.323 is widely used in video conferencing deployments.

Gateways that use H.323 do not depend on a call agent, as with Media Gateway Control Protocol (MGCP). H.323 is the default gateway protocol on Cisco routers. This chapter focuses on Cisco IOS H.323 gateways, although the concepts apply to all H.323 gateways.

In this chapter you will learn

• H.323 specifications
• H.323 network components
• Call flow with H.323 gateways
• H.323 protocol pros and cons
• Dial plan considerations
• Implementing H.323 gateways
• Securing H.323 gateways
• Troubleshooting tools