Lecture_10-HighSpeedLANs_Notes

Lecture_10-HighSpeedLANs_Notes - Lecture slides prepared by...

Info icon This preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
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.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
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)
Image of page 2
3 In recent years, two significant 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 files 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.
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
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.
Image of page 4
5 The earliest of these techniques, known as ALOHA, was developed for packet radio networks. However, it is applicable to any shared transmission medium. ALOHA, or pure ALOHA as it is sometimes called, specifies that a station may transmit a frame at any time. The station then listens for an amount of time equal to the maximum possible round-trip propagation delay on the network (twice the time it takes to send a frame between the two most widely separated stations) plus a small fixed time increment. If the station hears an
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern