The main components of a VoIP network are describe below
- Media Gateway
- Media Gateway/Signalling Controllers
- IP network
- IP Phone
Media Gateway
They are responsible for setting up call, detect call, analog to digital conversion and creation of voice packets. It also perform compression,echo cancellation and statistics gathering.
It also forms the interface that the voice content users so that it can be transported over the IP network. Each call is a single IP session transported using RTP. Trunking gateways that interface between the telephone network and a VoIP network. Such gateways typically manage a large number of digital circuits.
Types of media gateway
Residential Gateway provide a traditional analog interface to a VoIP network. Examples of include cable modem/cable set-top boxes, xDSL devices, and broadband wireless devices.
Business Media Gateway provide a traditional digital PBX interface or an integrated soft PBX interface to a VoIP network.Network access servers that can attach a modem to a telephone circuit and provide data access to the Internet.
Media gateway/Signalling Controllers
It houses the signalling controls services that control the media gateway controllers. It can be consider to that of H.323 gateway. It has the responsibility for some or all of the call signalling coordination, phone number translations, host lookup, resource management and signalling the gateway services to PSTN.The amount of functionality is based on the particular VoIP enabling products used.
The services of these devices are defined by the protocols and software they are running. There are several protocols and implementations that any number of vendors could deploy. Knowing the details of how the devices their protocols stack is important to designing the IP backbone that is to service the VoIP parts.
The IP infrastructure ensure smooth delivery of the voice and signaling packets to the VoIP elements. Due to their dissimilarities, the IP network must treat voice and data traffic differently. If an IP network is to carry both voice and data traffic, it must be able to prioritize the different traffic types.
There are several correlations to the VoIP and circuit-switching components, however there are many differences. One is in the transport of the resulting voice traffic. Circuit-switching telecommunications can be best classified as a TDM network that dedicates channels, reserving bandwidth as it is needed out of the trunk links interconnecting the switches.
IP phone
IP phone is a device that is used to receive voice packets and convert it to analog signal to the handset. A typical IP Phone perform the digitization, comperssion and packetization of analog signal . It uses the RJ 45 connector instead of the normal telephone connector. It is connected to the gateway via a port and signal passes through gateway to the network. At the same time, user can configure the IP address and that will enable communication to the distant end.
The following shows an example of the VoIP network:
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