>OPNET IT Guru: Quality of Service

>For Lab 5 of TCP/IP we are studying Quality of Service (QoS) and the Impact of Queuing Policy using OPNET IT Guru Academic Edition 9.1.

OPNET is a network simulation tool with many capabilities. It can simulate several different types of networks in its entirety and predict the outcome its events. Events such as QoS, network performance other measures.

Quality of Service (QoS) gives routers the ability to classify packets into different queues based on their priority level.

For this lab two FTP applications are to be created each running on its own client workstation with different priorities, one higher one lower. The Type of Service (ToS) set for the first application will be Best Effort, which has the lowest priority level. The second application will have its ToS set to Excellent Effort. Although Excellent Effort is not the highest priority it is certainty higher than Best Effort. In addition to the two clients, two routers will be setup. On of the routers is just a regular router and the outer denoted as a QoS router. The two routers are connected to each other via PPP_DS1 links, while the QoS router is connected to a FTP Server via a PPP_DS3 link. The speed of the DS1 link is 1.5 Mbps (made of 24 DS0s, 64Kbps)and the speed of the DS3 link is 44.7 Mbps (the number of DS0s is a lot!). DS3 is short for Digital Signal Level. Both routers are configured to have the same QoS scheme of Priority Queuing. Different packets originating from two different applications will have their ToS field in its IP header checked to determine which will get the higher priority.

With the FIFO QoS Scheme the higher priority application always took precedence. It waited in the queue buffer much less than the lower priority packets. Jitter was experienced hardly ever experienced. And, the length of time to wait in the queue was pretty much never, because for as long as their are packets waiting in the this high priority queue packets in the low priority are never sent out.

Due to time I have to finish this lab before it is due within the next few days. Coincidently, while working on this Lab my professor steped in the advanced lab and found me working on it. To his surprise I was the only one who did not have trouble with this lab. He himself had problems actually getting this lab to function as the tutorial stated.

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