H.323 and VoIP Components

While VoIP relies upon H.323 for call control and management functions across a voice-enabled network, a number of hardware and software components must be in place in order to enable VoIP on a Cisco network. The bullet points below outline some of the specific hardware and software typically found on a Cisco VoIP network.

The four main components of a VoIP network include:

  • Network infrastructure. A network that supports VoIP requires a number of different architectural elements in order to function correctly. Outside of the media (typically Ethernet and WAN links) used on the network, a combination of Layer 2 and 3 switches, as well as voice-enabled routers are used to transport IP packets that contain voice data. IP telephones are typically plugged into a Layer 2 or Layer 3 switch on the Ethernet network, with the switch providing inline power to the phone (a technique known as power over Ethernet). When a user of an IP telephone needs to communicate with a user on the PSTN, a voice-enabled router acts as a gateway between the devices, interconnecting the IP and PSTN networks. When an IP phone user needs to connect to another IP phone user, a voice-enabled router is not required.
  • Call processing software. On a Cisco VoIP network, Cisco CallManager software handles call control functions including route selection, last-number redial, billing, quality monitoring, and more. CallManager carries out many of the same functions as a PBX would on a traditional voice network.
  • Applications. In the same way that users on a traditional voice network require additional features like voice mail, so do users of IP telephones. A variety of different applications can be added to a VoIP network including voice mail, automatic call distribution software, and so forth.
  • Terminal devices. Users ultimately interface with a VoIP network via terminal devices like IP phones. While IP phones may be the most popular choice for business users, other possibilities such as headsets that connect to a PC can also be used.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of 2000Trainers.com. He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.