Network Congestion and Quality of Service Analysis Using OPNET

Information Engineering
Furat Nidhal Tawfeeq
Dr. Mohammed A. Abdulla
Congestion management features operate to control congestion once it occurs. One way that network elements handle an overflow of arriving traffic is to use a queuing algorithm to sort the traffic, and then determine some methods of prioritizing it onto an output link. Each queuing algorithm was designed to solve a specific network traffic problem and has a particular effect on the network performance. The work presented in this thesis deals with important issue that is the quality of service (QoS) techniques, which can be integrated to enhance the operation of the network. The quality of service is the collective effect on service performance, which determines the degree of satisfaction of a user of the service.
In this thesis, packet schedulers (FIFO, WFQ, CQ and PQ) and traffic policing algorithms (CAR) were implemented and evaluated under different applications (file transfer, E-mail, voice and video conferencing) with different priorities (Background, Standard, Excellent Effort and Streaming multimedia).
Computer simulation was performed to study and verify the above mechanisms in the performance enhancement using the OPNET simulator; the output result which depends on some statistics that describe the behavior of the network such as end-to-end delay, delay variation, packet loss, etc were collected.
According to the results, we found that relatively the weighted fair queuing is the appropriate type of queuing by offering dynamic, fair queuing that divides bandwidth across queues of traffic based on weights, also this results will be more accepted when commit access rate is implement together with WFQ, so the later will be use the ability of the CAR to manage rate traffic by using access bandwidth management which implements by using rate limit statements.