Voice over Internet Protocol

The Internet VoIP technology offers telephone calls to be made over computer networks. VoIP alters analog voice signals into digital data packets and by using Internet Protocol (IP) supports real-time, two-way transmission of conversations. By using a VoIP service provider and standard computer audio systems VoIP calls can be made on the Internet. Alternatively many service providers support VoIP through telephones which use special adapters to connect to a home computer network. Many VoIP implementations are designed on the basis of H.323 technology standard.

VoIP Components
Although a very different technology and approach are used to provide voice services, some of the same components that used in the Public Switched Telephone Network (PSTN) are also found in VoIP environments. VoIP provides support to networks which must perform all of the same tasks that the PSTN does in addition to performing data and signaling gateway functions to the existing public network. There are certain VoIP components that must exist for the technology to function properly independent upon which solution, protocol or architecture selected. There are four major components found in any VoIP environment. These components are:
1) The IP network
2) Call processor/controllers
3) Media/signaling gateways
4) Subscriber terminals.

1) The IP network
A network which supports VoIP technology can be viewed as one logical voice switch in distributed form with the IP backbone providing connectivity to the distributed elements in the network. This IP infrastructure must guarantee smooth transfer of voice and signaling packets to the VoIP elements. Due to infrastructures dissimilarities IP network must treat voice and data traffic differently because latency in voice transmission is more noticeable to the user than latency in data transmission. There are differences regarding correlations can be made to VoIP and circuit-switching components. A circuit switched network can be classified as a Time Division Multiplexing (TDM) network that allocates channels and reserves bandwidth as it is needed out of the trunk links interconnecting the switches. IP networks are dissimilar than circuit switching networks because they are based on a packet and build on statistical availability. Quality of Service (QoS) defines a guaranteed output level and Class of Service (CoS) defines that packets of a certain application are given priority. This guaranteed outputs and prioritizations are necessary for real-time VoIP applications to ensure that the voice service is unaffected by other traffic flows.

2) Call Processor/Controllers
Call processor/controllers uses system software which sets up and monitors calls maintains the dial plan, authorizes users, performs phone number translations, coordinates some or all of the call signaling, delivers basic telephony features and may control the bandwidth utilization on each link. In addition call processor or controllers house the signaling and control services which coordinate the media gateway functions. A call process/controller is called as a soft switch, call agent, call manager, or gatekeeper depending on its function in the VoIP supported network. The amount of functionality provided by a call process/controller is depends upon particular VoIP product used.

3) Media/Signaling Gateways
VoIP Gateways are used for call origination, detection, analog-to-digital conversion of voice and creation of voice packets. In addition, media gateways offer features such as echo cancellation, voice compression, silence suppression and statistics gathering. In several physical forms Gateways exist including a physical board or blade found in a dedicated telecommunications frame or a common PC running VoIP software. Media and Signaling Gateway provides features and services can span a wide spectrum and their functions can be divided into three key gateway types:

i) Media Gateway (MG)
The media gateway allows the delivery of media signals between the IP Network and circuit switched or traditional telephone network. This Gateway translates information delivered on the IP network using packet formats to Pulse Code Modulation (PCM) encoded voice on the PSTN side and vice versa. MG offers trunking functions which acts as interface between the telephone networks and a VoIP network.

ii) Signaling Gateway (SG)
This gateway type provides direction to the signaling functions between IP network and the switched circuit network. It may offer correlation between the H.323 signaling on the packet network side and the signaling system seven (SS7) signaling on the PSTN side.

iii) Media Gateway Controllers (MGC)
By providing the call setup and processing functions the media gateway controller communicates with both the MG and the SG. This gateway type uses a dedicated protocol like Media Gateway Control Protocol (MGCP) protocol for inter-gateway communications functions.

4) Telephony Terminal
The user or subscriber’s telephone instrument is IP phone. This device offers real time, bi-directional communication with another compatible device. The IP phone offers voice communications and may offer other optional services such as data or video.

Advantages of Internet Voice
Because Internet Voice is digital, VOIP offer features and services that are not available with a traditional phone. You need not retain and pay the additional cost for a line just to make telephone calls if you have a broadband internet connection. By using Internet Voice you can talk as long as you want with any person in the world. You can also talk at the same time with many people without any additional cost.

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