Fundamental of VoIP and Security

    CHAPTER NO.5

 V.QUALITY OF SERVICE:   Sound quality of the phone from source to destination is measured that how clear it is for both sides. Quality of Service refers to the clarity of sound of phone call over a network. The "how good do I sound" approach to measuring the VoIP network. There are many factors that make it noisy or decrease the quality of sound into the end quality of a phone call. These factors are latency, Jitter, Packet Loss, and an overall combination of network equipment and bandwidth. Each of the term is discussed in detail below and how a VoIP provider deals with these issues to clear the track for the clients. 1-  Jitter  2- Latency 3-    Packet Loss.   This chapter of the thesis is very important in order to understand the clarity of voice and in this regard performance level of VoiP phone. Although Quality of service has other issue as well for example echo, out of order delivery, error etc. This thesis covers only fundamental of VoiP so only three most important and common issues are covered. 

A.     JITTER:   When packets are received with a timing variation from when they were sent, a quality issue of Jitter may be noticed. When Jitter occurs, member on the call will notice a delay in phone conversation and some time sound is double and return against the source to source. It has been mostly experienced with traditional phone service from time to time. Many VoIP providers reduce or eliminate Jitter by controlling for Jitter and time issues within their networking equipment. More equipment you have less jitter is occurred.

B.    LATENCY:   Latency generally refers to the physical distance that phone call must travel to reach to service provider. When a phone call is made with VoIP the sound make is cut into thousands of little pieces called Packets and then sent through the Internet to service provider. These packets travel so fast that the process of traveling generally takes milliseconds.    Mostly the people who are using VoiP are not affected by Latency with their VoIP providers. If the roundtrip travel time of the packet takes more then 250 milliseconds the quality of the communication may experience some issues due to Latency. Most commonly, this occurs when trying to connect to a service provider from an International location. Latency can occur in both VoIP and traditional phone systems but this traditional phone is more affected than VoiP. Many VoIP providers have established multiple hosts to reduce Latency and provide a quick connection from any location. One of the benefits of using VoIP over traditional phone systems is that Internet speed is constantly increasing, helping to keep Latency down. Additionally, many VoIP companies provide service centers located in specific areas to ensure Latency is low, not considering of the location. 

C.    PACKET LOSS:    Packet takes place when a large amount of network traffic hits the same Internet connection in VoIP. Our voice is sent in term of packets. When talking on a VoIP system, Packet Loss can be identified with an echo or tin-like sound. Packet Loss is most commonly measured in percentages. For VoIP use, packet loss should not exceed 1%. 1% packet loss will result in a skip approximately once every three minutes. VoIP customers can help to reduce Packet Loss by reducing "high traffic" tasks such as uploading files or sending emails with large attachments while on the telephone.