Fibre Distributed Data Interface

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Fibre Distributed Data Interface

• 100Mbps
• 1986 ANSI - X3T9.5 committee
• Supports IEEE 802.5
• Access Methodology Modified token-passing
• Logical topology sequential
• Physical Dual counter-rotating rings

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Dual-Ring Topology
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Subnets
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Dual-Ring Topology

• Primary ring
• Traffic
• FDDI Reconfigures the network
• Redundancy
• Transmission
• Cable Failure
• Ring Failure
• The total cable length of both rings combined
  must not exceed 200 km, and it cannot hold more
  than 1000 computers.

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Topology

• FDDI operates at 100 Mbps over a dual-ring
  topology that supports 500 computers over a
  distance of up to 100 km
• More than one computer at a time can transmit
• Capacities should be divided in half.
• FDDI network should be limited to 500 computers
  and 100 km of cable.

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FDDI (continued)
A FDDI network
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FDDI

• Connects large and small minicomputers
• Back-end networks
• FDDI works with backbone networks to which other
  low-capacity LANs can connect
• LANs that require high data rates
• File transfer, Video, CAD CAM

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FDDI in Star

• FDDI computers can accommodate point-to-point
  links to a hub.

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Built-in reliability

• High degree of reliability and security
• EMI
• RFI
• Two Rings
• Primary ring data
• Secondary ring backup
• Single Hub or connector
• 500 nodes at 2km apart
• SAS single attachment station
• DAS dual attachment stations

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Built-in Reliability
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FDDI Uses Beaconing
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Beaconing

• With beaconing, the computer that detects a fault
  sends a signal, called a "beacon," onto the
  network.
• The computer continues to send the beacon until
  it notices a beacon from its upstream neighbour,
  and then it stops sending.

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Standards

• Distances in FDDI LAN
• Impractical to turn a free token to busy
• Physically removes token and transmits an entire
  Data Frame.
• Numerous messages can be sent
• Synchronous Frames

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Modified Token Passing

• Transmits as many frames as it can produce within
  a predetermined.
• There can be several frames circulating on the
  ring at once.
• Higher throughput than a Token Ring network,
  which allows only one frame at a time to
  circulate.

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Application of FDDI

• Bandwidth drivers fall into two categories
• Network Architecture Trends
• Network Application Trends
• LANs more and more users
• FDDI networks form the backbone

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Campus Backbone

• Connecting LANs located throughout a series of
  closely situated buildings.
• Ring circumference can equal 200 km
• Multiple FDDI LANs
• 100 Mbps FDDI building backbone
• Connecting numerous 10-Mbps Ethernet
• Servers connected via connectors

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Backbone
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High-Bandwidth Workgroups

• FDDI LANs connecting as few as 20 computers
• High-bandwidth communication
• CAD/CAM Workstations
• Power Users
• GUI

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High-Bandwidth Subgroups

• In some cases only 2 or 3 devices such as
  servers, require high-bandwidth.
• Increased demand
• Distributed Computing
• Data Distribution

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