Local Area Networks

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Local Area Networks
A data communication system that allows a number
of independent devices to communicate directly
with each other in a limited geographic area.
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Four Architectures

• Ethernet
• Token Bus
• Token Ring
• Fiber Distributed Data Interface (FDDI)
• The first 3 are IEEE standard while FDDI is an
  ANSI standard

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OSI Model and Project 802
MAC medium access control - resolves the
contention for the shared media - contains the
synchronization, flag, flow and error control -
contains the physical address of the next station
LLC logical link control - non architecture
specific, common to all LANs - contains the
logical addresses, control information and data
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Project 802
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PDU Control Field
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ETHERNET
Access Mechanism CSMA/CD ?Carrier Sense Multiple
Access/Collision Detection
LLC
MAC Frame
PDU length 46 to 1500 bytes
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Thick Ethernet / Thicknet
Transceiver
Connection
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Ethernet Segments
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Thin Ethernet/Thinnet/Cheapnet/Cheapernet
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Max length (hub to station) 100m
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StarLAN
Up to 10 stations in a chain
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Fast EthernetIEEE 802.3u
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Why do we need to increase the speed of Ethernet
LAN
Introduction of more sophisticated operating
system and applications, faster processors and
greater disk and memory capacities.
Many companies now use Internet technologies to
build private corporate intranets, for accessing
critical data.
Multimedia client/server applications.
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Fast Ethernet

• Data rate 100 Mbps
• Increases the speed limit of the highway by
  orders of magnitude from 10 Mbps to 100 Mbps to
  1000 Mbps (Gigabit Ethernet)
• Reduces the amount of time it takes to transmit 1
  bit by a factor of 10.
• Employs a star topology at the physical layer and
  supports twisted pair and fiber-optic cable.

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Fast Ethernet

• 3 different media specifications
• 100BASE-TX
• 100BASE-T4
• 100BASE-FX
• The first 2 use twisted pair cable and the third
  uses fiber optic cable.
• All 3 are designed to interoperate with one
  another

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100BASE-TX

• Transmits and receives data over two pairs of Cat
  5 UTP cable
• Uses full duplex signaling system
• Distance between station and hub is 100m
• Networks based on this standard must be Cat-5
  compliant, including wire, connectors, patch
  panels
• 1 pair for transmission
• 1 pair for reception
• 2 pairs are extra wires that can be used for
  voice communication or reserved for further
  network enhancements

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100BASE-T4

• Uses half-duplex signaling system to transmit and
  receive data over 4 pairs of Cat 3, 4, 5 UTP
  cable.
• 1 pair for transmitting data
• 1 pair for receiving data and collision detection
• 2 pairs are used for either transmitting or
  receiving
• 100BASE-TX vs. 100BASE-T4 ?

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100BASE-FX

• Uses 2 strands of 62.5/125 micron multimode fiber
  optic cable
• 1 strand for transmission
• 1 strand for reception
• Distance between station and hub is less than
  2000m
• Signaling system is the same as100BASE TX

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Gigabit Ethernet
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Why do we need 1000Mbps technology?
Deployment of multimedia applications
Integration of faster computer systems
Migration of Fast Ethernet from backbone to the
desktop
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Gigabit Ethernet
1000 Mbps - 1 billion bits per second IEEE
802.3z - Gigabit Ethernet over fiber IEEE 802.3ab
- Gigabit Ethernet over copper
Used as the backbone in many enterprise networks.
Alleviates congestion at server level or at
interswitch connections.
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Gigabit Ethernet over fiber

• 1000BASE-SX (short wavelength fiber)
• 62.5 micron multimode fiber Max distance 220-275
  m
• 50 micron multimode fiber Max distance 500-550 m
• 1000BASE-LX (long wavelength fiber)
• 62.5 micron multimode fiber, Max distance 550 m
• 50 micron multimode fiber, Max distance 550 m
• 9 micron single-mode fiber, Max distance 5,000m
  (5km)
• 1000BASE-CX (short haul copper)
• initial standard for Gigabit Ethernet connections
  over Shielded single twisted-pair cable
• Max distance 25m

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Gigabit Ethernet- over copper

• IEEE 802.3ab - Gigabit Ethernet over copper
• 1000BASE-T, running over Cat 5 cable at a
  distance up to 100 m.
• More info about thet types
• ?http//en.wikipedia.org/wiki/Gigabit_Ethernet