Local Area Networks (LANs)

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Computing systems have always had a need to share information (data) and resources among remotely located users. Thus the development of LANs. In fact, the need to share computer files, programs, printers, and disk storage devices among computers accelerated the growth of LANs. An early example of a LAN is the telephone network which has been in existence for a good number of years.

LANs provide high-speed communication within a limited geographic area. They are designed to provide communication and information exchange for all aspects of information processing. The physical media used by the LAN may be twisted-pair, coaxial cable, or fiber optics to name a few.

LAN Design Goals:

• High Speed and Bandwidth -- Data should move quickly over the LAN, and many users should be served simultaneously.
• Reliable and Maintainable -- Users should be able to access the network reliably, and the LAN hardware and software should be reliable and easy to maintain.
• Low Cost -- As more people rely on LANs, the cost per person should decrease to keep LANs affordable.
• Compatibility -- Equipment from different vendors should be able to use and be integrated into the LAN.
• Extendable -- Additional users and equipment should be accommodated/integrated into the LAN without requiring major changes on the part of current users and equipment already part of the LAN.
• Standards -- The LAN should follow networking, ISO, or ANSII standards. The University of Illinois provides a good reference for LANs and networking .

Telephone (Analog) vs Data (Digital) Networks

Voice signals used by most telephones are analog while data signals are digital. Analog signals are continuous sinusoidal transmissions, whereas digital signals have two states: on and off. A modem is required to convert between the two.

If you are on the Virginia Tech campus, you can connect directly to the Va Tech computing network through a high speed ethernet interface. However, if you live off campus and have to connect to the VT LAN network, you do so through the modem pool. You will need a modem on your computer to perform the analog to digital conversion. This transfer through analog telephone lines and modems result in very slow data throughput, (currently at 56.6 kbps - 28.8 kbps), many times slower than through the digital ethernet.

Virginia Tech Networks

Virginia Tech provides network access through a LAN Ethernet. (Previously Va Tech also provided CBX networking, which stands for Computerized Branch Exchange, and its terminal servers). The campus has ethernet wiring in all of its academic buildings and dorms. For an overview of the networks on the VT campus see VT campus Network Configuration Management.

Communications Network Services is in-charge of networking on the Virginia Tech campus. Virginia Tech is using an ATM 622Mbps connection for IP over ATM. Check out the following ATM tutorial and other information on ATM networking.

Further Reading

More general information on ethernet is also available from the University of Texas. They also have an interesting tutorial.