Local Area Network

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Local Area Network
Daniel Shin CS 147, Section 3 November 18, 2008
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What Is a LAN?

• A LAN is a high-speed data network that covers a
  small geographic area.
• It typically connects workstations, personal
  computers, printers, servers, and other devices.

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Characteristics

• High data-transfer rates.
• Small geographic range.
• Lack of a need for leased telecommunication lines.

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Advantages

• LANs offer computer users many advantages.
• Shared access to devices and applications.
• File exchange between connected users.
• Communication between users via electronic mail
  and other applications.

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First Commercial LAN

• The first commercial installation of a LAN was in
  December 1977 at Chase Manhattan Bank in New
  York.
• It was not an Ethernet network, but a network
  called ARC (Attached Resource Computer or ARCnet).

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ARCnet

• It was developed by Datapoint Corporation in 1976
  and announced in 1977.
• ARCnet was the first widely available networking
  system for microcomputers.
• It became popular in the 1980s for office
  automation tasks.
• It is said to have since gained interest in the
  embedded systems market, where certain features
  of the protocol are especially useful.

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Ethernet

• Ethernet was developed at Xerox Corp.'s Palo Alto
  Research Center (PARC) in the early 1970s.
• The original network speed was just under
  3Mbit/sec.

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Token Ring

• Token Ring uses a special three-byte frame called
  a token that travels around the ring.
• Resides at the data link layer (DLL) of the OSI
  model.

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Fiber Distributed Data Interface (FDDI)

• FDDI provides a standard for data transmission in
  a LAN that can extend in range up to 124 miles.
• FDDI uses a dual-attached, counter-rotating token
  ring topology.

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LAN Protocols and the OSI Reference Model
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LAN Media-Access Methods

• Ethernet uses carrier sense multiple access
  collision detect (CSMA/CD).
• Each network station listens before and after
  transmitting data.
• If a collision is detected, both stations wait a
  random time before trying to resend.

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LAN Media-Access Methods (cont.)

• Token Ring passes a special type of packet called
  a token around the network.
• If a network device has data to send, it must
  wait until it has the token to send it.
• After the data has been sent, the token is
  released back on the network.

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LAN Transmission Methods

• LAN data transmissions fall into three
  classifications unicast, multicast, and
  broadcast.
• In each type of transmission, a single packet is
  sent to one or more nodes.

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LAN Transmission Methods (cont.)

• In a unicast transmission, a single packet is
  sent from the source to a destination on a
  network.
• A multicast transmission consists of a single
  data packet that is copied and sent to a specific
  subset of nodes on the network.
• A broadcast transmission consists of a single
  data packet that is copied and sent to all nodes
  on the network.

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LAN Topologies

• LAN topologies define how network devices are
  organized.
• Four common LAN topologies are bus, ring, star,
  and tree.

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LAN Topologies (cont.)

• A bus topology is a linear LAN architecture.
• Transmissions from network stations create the
  length of the medium and are received by all
  other stations.

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LAN Topologies (cont.)

• A ring topology is a LAN architecture that
  consists of a series of devices connected to one
  another by unidirectional transmission links to
  form a single closed loop.

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LAN Topologies (cont.)

• A tree topology is a LAN architecture that is
  identical to the bus topology.
• Except, branches with multiple nodes are possible.

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LAN Devices

• A repeater connects two network segments.
• It is a physical layer device used to
  interconnect the media segments of an extended
  network.

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LAN Devices (cont.)

• Multiple LAN extenders can connect to the host
  router through a WAN.
• It is a remote-access multilayer switch that
  connects to a host router.

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LAN Devices (cont.)

• A hub is a physical layer device that connects
  multiple user stations, each via a dedicated
  cable.
• Hubs are used to create a physical star network
  while maintaining the logical bus or ring
  configuration of the LAN.