Lecture_10-HighSpeedLANs_Notes

Lecture_10-HighSpeedLANs_Notes - 1 Lecture slides prepared...

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Unformatted text preview: 1 Lecture slides prepared by Dr Lawrie Brown ([email protected]) for “Data and Computer Communications”, 8/e, by William Stallings, Chapter 16 “High Speed LANs”. Modified by Dr. Mohan Das, July 2008. 2 The most important of these are • Fast Ethernet and Gigabit Ethernet: The extension of 10-Mbps CSMA/CD (carrier sense multiple access with collision detection) to higher speeds is a logical strategy, because it tends to preserve the investment in existing systems. • Fibre Channel: This standard provides a low-cost, easily scalable approach to achieving very high data rates in local areas. • High-speed wireless LANs: Wireless LAN technology and standards have at last come of age, and high-speed standards and products are being introduced (see next chapter) 3 In recent years, two signifcant trends have altered the role oF the personal computer, increased the volume oF data to be handled over LANs, and thereFore the requirements on the LAN: • The speed and computing power oF personal computers has continued to enjoy explosive growth • MIS organizations have recognized the LAN as a viable and indeed essential computing platForm, resulting in the Focus on network computing. The Following are examples oF requirements that call For higher-speed LANs: • Centralized server farms: In many applications, there is a need For user, or client, systems to be able to draw huge amounts oF data From multiple centralized servers, called server Farms.. As the perFormance oF the servers themselves has increased, the bottleneck has shiFted to the network. • Power workgroups: These groups typically consist oF a small number oF cooperating users who need to draw massive data fles across the network. In such cases, large amounts oF data are distributed to several workstations, processed, and updated at very high speed For multiple iterations. • High-speed local backbone: As processing demand grows, LANs proliFerate at a site, and high-speed interconnection is necessary. 4 The most widely used high-speed LANs today are based on Ethernet and were developed by the IEEE 802.3 standards committee. As with other LAN standards, there is both a medium access control layer and a physical layer. The media access uses CSMA/CD. This and its precursors can be termed random access, or contention, techniques. They are random access in the sense that there is no predictable or scheduled time for any station to transmit; station transmissions are ordered randomly. They exhibit contention in the sense that stations contend for time on the shared medium. 5 The earliest of these techniques, known as ALOHA, was developed for packet radio networks. However, it is applicable to any shared transmission medium....
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This note was uploaded on 08/15/2010 for the course FIT 1003 taught by Professor Yeap during the Three '10 term at Monash.

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Lecture_10-HighSpeedLANs_Notes - 1 Lecture slides prepared...

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