Local Area Networks LANs

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Local Area Networks (LANs)
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Local Area Networks (LANs)

• The development of LANs was motivated by the need
  to share resources and information among hosts in
  a dept./workgroup
• Differ from a wide area or a public network
• The short distances between hosts imply that
  low-cost, high-speed, reliable communication is
  possible

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LAN structure

• Hosts are interconnected by a shared transmission
  medium
• It is arranged in a bus, ring, tree, or a star
  topology (a cabling system)
• Hosts are connected to a cabling system through a
  network interface card (NIC) or LAN adapter card

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LAN Technologies

• Available LAN technologies
• Ethernet
• FDDI
• ATM
• Wireless

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LAN Technologies Ethernet Technologies

• 10 Mbps10Base-T Ethernet
• 100 MbpsFast Ethernet
• 1000 MbpsGigabit Ethernet
• 10-Gigabit Ethernet

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LAN Technologies -Ethernet

• Ethernet was invented mid. 1970
• In 1980 early 1990 faced a lot of challenges
  from other LAN technologies (FDDI, ATM)
• Today Ethernet is the most prevalent wired LAN
  technology

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LAN Technologies -Ethernet

• It is currently used for approximately 85 percent
  of the worlds LAN-connected PCs and workstations
• Reasons for Ethernets Success
• 1st widely deployed high-Speed LAN
• Network administrator becomes familiar with
  Ethernet
• Reluctant to switch to other technologies
• Cheap
• Offer versions that operated at equal data rates
  /higher
• Provides extensive topological flexibility for
  network installations

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LAN Technologies Ethernet Topologies

• Ethernet technologies take on many topological
  configurations eg Star topology, Bus topology
• Based on a point-to-point connection structure

• The original Ethernet networks were implemented
  with a coaxial bus structure

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LAN Technologies Ethernet Topologies

• With a bus topology, segment lengths were limited
  to 500 meters, and up to 100 stations could be
  connected to a single segment.

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Ethernet Technologies

• Since the early 1990s, the network configuration
  of choice has been the star-connected topology

Host
Hub
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Ethernet Technologies

• All connections in a star network are
  point-to-point links implemented with either
  twisted-pair or optical fiber cable.

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Ethernet Switch
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LAN Technologies -Ethernet

• The center of the star topology is a hub or a
  switch
• Hub
• a physical-layer device
• has two or more interfaces
• when a bit representing a zero or a one, arrives
  from one interface, the hub re-creates the bit,
  and transmits the bit onto all other interfaces

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LAN technologies FDDI

• FDDI (Fiber Distributed Data Interface)
• It was developed in the mid. 1980s
• FDDI has most often been used as a backbone
  technology because of its high reliability and
  bandwidth.
• FDDI protocol is loosely based on the token ring
  protocol with hosts having the ability to send
  only when they hold a token.

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LAN technologies FDDI

• FDDI (Fiber Distributed Data Interface)
• FDDI runs at 100 Mbps over an optical fiber
  medium
• Performance characteristics
• Only supports one speed, 100Mbps
• Can have a maximum of 500 stations connected to
  each ring
• Guarantee full use of the available bandwidth
• Great for multimedia and real-time applications

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Asynchronous Transfer Mode ATM

• ATM was developed in the mid 1980s
• Goal design a single networking technology that
  would transport real-time audio/video, text,
  email and images files
• High-speed local-area network (LAN)
  interconnection

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Principal Characteristics of ATM

• ATMs architecture is organized into 3 layers

ATM Adaptation Layer
Transport Layer
ATM layer
Network Layer
ATM Physical Layer
Physical Layer
End system
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Principle Characteristic of ATM

• ATM switch has 2 layers

ATM layer
ATM Physical Layer
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ATM architecture
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Principle Characteristics of ATM

• ATM adaptation layer (AAL) is analogous to the
  Internets transport layer
• AAL is presented at the ATM devices
• The unit of data handled by the AAL is called AAL
  protocol data unit (PDU)
• PDU equivalent to a UDP or TCP segment

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Principle Characteristics of ATM

• ATM Layer is the heart of ATM architecture
• ATM layer defines the structure of ATM packet
  (ATM cell)
• ATM physical layer deals with voltages, bit
  timings, and framing on the physical medium