voip

VOIP networks must perform all of the same tasks that the PSTN does, in addition to performing a gateway function to the existing public network. There are three major pieces to a VOIP network.

• multimedia gateways/signalling controllers
• VoIP network
• mulimedia gateways

Media gateways are responsible for call origination, call detection, analog-to-digital conversion of voice, and creation of voice packets (CODEC functions).

The media gateway forms the interface that the voice content uses so that it can be transported over the IP network.Their features and services can include some or all of the following.

• Network access servers that can attach a modem to a telephone circuit and provide data access to the Internet.
• Discreet IP telephones units.
• Residential gateways that provide a traditional analog interface to a voice over IP network.
• Business media gateways that provide a traditional digital PBX interface or an integrated soft PBX interface to a voice over IP network.
• Trunking gateways that interface between the telephone network and a voice over IP network.
• Access media gateways that provide a traditional analog or digital PBX interface to a voice over IP network.

Media Gateway Controllers
The media gateway controller has the responsibility for some or all of the call signaling coordination, phone number translations, host lookup, resource management, and signaling gateway services to the PSTN (SS7 gateway). Media gateway controllers could be considered similar to that of H.323 gatekeepers. Media gateway controllers house the signaling and control services that coordinate the media gateway functions.The amount of functionality is based on the particular enabling products used.

For calls that originate and terminate within the domain of the voice over IP network, only a media gateway controller might be needed to complete calls. However, a VOIP network is frequently connected to the public network. In a scalable voice over IP network, you can breakup the role of a controller into signaling gateway controller and media gateway controller. You could use a signaling gateway controller to directly connect to the SS7 network, while also interfacing to a VOIP network elements. This signaling controller would be dedicated to the message translation and signaling needed to bridge the PSTN to the voice over IP network.

There are several protocols and implementations that any number of vendors could deploy. Knowing the details of how the devices use their suite of protocols is important to designing the IP backbone that is to service the voice over IP elements. The services of these devices are defined by the protocols and software they are running.

You can view a VOIP network as one logical switch. However, this logical switch is a distributed system, rather than that of a single switch entity; the IP backbone provides the connectivity among the distributed elements.

Jim Francisto
voip

This entry was posted on Monday, November 17th, 2008 at 10:36 am and is filed under Voip hardware. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.