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The main goal of Quality of Service is to offer priority and committed bandwidth, less jitter and latency and finally reduce packet loss.

When creating Quality of Service rules for a business, it is vital to emphasize on which traffic requires special treatment. Network architects need to consider how Quality of Service problems affect not only the network equipment but also the applications that use the net. Employers identify service quality based on two measures: The speed with which the net responds to their needs and the ease of use of the applications they want to use.

Quality of Service helps to reduce these problems. Several Cisco network devices have built-in Quality of Service mechanisms. Particular applications are very sensitive to bandwidth requirements, packet delays, net jitter as well as packet loss. Real-time IP telephony and streaming video always need special treatment.

IP Telephony Requirements

Voice traffic needs more than a simple connection between devices. The quality of the transmissions is very essential. When delays happen, voices break up and sound becomes distorted. IP telephony requires that Quality of Service mechanisms are enabled. It is important that voice packets have low latency as well as low jitter at every single hop along a given path.

Streaming Video Requirements

Streaming video is a video feed that is typically sent from recorded files. This media stream is sent as a multicast so many employers can watch the stream at the same time. In a net without Quality of Service, all TCP/IP packets get the same treatment, and as a result, real-time applications suffer.

QoS policies do not generate more bandwidth of course. As an alternative, it prioritizes bandwidth use to support new technologies like IP telephony. QoS manages priority traffic on converged nets.

Voice and Data Traffic

In a converged net, continuous, small-packet voice traffic contests with large, asymmetrical data flows such as file transfers. Even though usually the packets carrying voice traffic on a network are not big, delays that happen while they cross the network will produce low voice quality. Files from real-time applications, should be processed at the same rate as it is sent. Consequently, VoIP uses User Datagram Protocolthat is a best-effort transport protocol. On the other hand, packets that carry file transfer data are usually large. These packets use transmission control protocol.

It is likely to retransmit part of a data file, but it is not possible to retransmit part of a voice dialogue. Therefore, voice and video traffic must have much better priority over data traffic.

Manolis Skoras is a Cisco, Microsoft and HP Certified Trainer and systems-network engineer. Recently he created a Cisco CCNA certification website to help his students and people around the world to better understand the material they will be tested on, thus having greater success rates. Check Certify4Sure today!