• United States
Senior Editor

VoIP issues

Oct 15, 20032 mins

* Session controllers

With he growth of voice over IP in public and private networks, the need for technology to smooth the transition and translation between those nets is growing.

Our Technology Update author this week takes a look at one device, known as a session controller that can handle different Session Initiation Protocol-to-SIP networks or support network address translation for Media Gateway Control Protocol and H.323 protocols used for packet voice.

You’ll recall that the International Telecommunication Union developed H.323 to ensure interoperability between gear that delivers real-time communications over packet-based networks. The H.323 suite of protocols details call-control and codec functions. Many in the industry view H.323 as a heavy protocol that is limited in its applications, according to our author.

SIP, the Internet Engineering Task Force’s protocol for VoIP, is centered around making voice more Internet-like. SIP is modeled after other Internet protocols, such as HTTP and Simple Mail Transfer Protocol, where flexibility and simplicity are key attributes.

Session controllers are usually stand-alone devices that can help customers overcome some knotty problems facing voice traffic, in particular as it moves between IP networks like corporate LANs and service providers’ networks. These processor-intensive devices peer deep into packets to analyze and alter them, if necessary, so payloads make their way across network boundaries intact. The primary benefit of such devices is that they do all the work needed without upgrading or reconfiguring firewalls.

Acme Packet, Netrake and Nextone are focused on service providers, while the others offer gear for providers and businesses. Netrake touts its custom processors, while Nextone promotes its use of generally available processors that keep costs down, experts say.

If you want to know more about how session controllers work see: