Efficiency Issues in a Switched LAN

Ethernet—a switched local area network—is the market leader for LAN Technologies today. From businesses to government organizations, home to shopping centers, and NGOs to universities, Ethernet is the sole shareholder of the local area networks. Due to such a wide-range, Ethernet has become an intensively addressed research area, with concerns ranging from the high level network design problems to the mid-level theoretical protocols architectures to the low level physical hardware details. As a result, new standards, increased speeds and better technology for Ethernet are very often reported. Due to the fast and intensive development, the diameter of the LAN deployment has been increased to a bigger scale. Local area networks have grown from a couple of hundreds of clients to several thousands of clients advancing the concept of a Campus Area Network. The huge enhancements in network size—and constant growth—led to various concerns in the switched network design, some very crucial. First, the fault tolerance and the availability of the network should be ensured for virtually 100% of the time. Second, the aggregation of the switched traffic flow to the network core and the Internet is a major aspect, as the proper size of upstream links keeps the network from being congested. Third, the proper design of the switched network has quality, speed and efficiency aspects to consider. The above mentioned issues do not only arise when a network is being deployed. They can also arise after the establishment of a network, due to several reasons like arbitrary growth, careless planning, design mistakes, replacement of devices/links upon failures or for extending, etc. All these concerns lead to one common theme: that of the efficiency of the LAN. This thesis provides a case study of a university LAN: we set out to uncover just how efficient the Åbo Akademi University's Ethernet is. The results we present are obviously characteristic to this particular network. We found that the network design of the Åbo Akademi LAN was influenced over the years by the limited budget as well as the lack of stringent security and efficiency needs. While there is no reason to generalize our findings, we can still draw several lessons from our study. We have observed various efficiency problems and proposed solutions to them. By simulation we have also visually illustrated the differences and improvements our solutions would bring.