1 fibre distributed data interface 100mbps –1986 ansi - x3t9.5 committee –supports ieee 802.5...

1

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

2

Dual-Ring Topology

3

Subnets

GOLDMAN: DATACOMM FIG. 06-07

8 pin RJ-45 jack for 10Base-T

BNC connector for 10Base-2 (thin coax ethernet)

DB-15 AUI connector for 10Base-5 (thick coax ethernet)

Jumpers to enable/disable media interfaces

Transceiverthick coax ethernet

DB-15 AUI

AUI or transceiver cable

DB-15 AUI

4

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.

5

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.

6

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

8

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

10GOLDMAN: DATACOMM

FIG. 05-13

FDDI concentrator hub

FDDI bridge

Microcomputer

Microcomputer

Microcomputer

Server

Minicomputer

Minicomputer

Server

Microcomputer MinicomputerMainframe computer

FDDI adapter cards or controllers for each device connected to an

FDDI concentrator/hub

inner loop transmission

direction

outer loop transmission

direction

FDDI Topology

SAS controller (accesses single

loop only)

Fiber

FiberFiber

STP

STP

STP

Ethernet transceiver

11

Built-in Reliability

13

FDDI Uses Beaconing

34

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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


File servers

Compute servers

Database servers

FDDI concentrator

FDDI concentrator

FDDI concentrator

router

router

Backbone

Workgroup

workstation

workstation

workstation

FDDI concentrator

server

Ethernet hubworkstation

workstation

workstation

Sub-workgroup

FDDI/Ethernet Bridge

FDDI concentrator

servers


workstation

workstation

20

High-Bandwidth Workgroups• FDDI LANs connecting as few as 20 computers

– High-bandwidth communication– CAD/CAM Workstations

• Power Users– GUI


File servers

Compute servers

Database servers

FDDI concentrator

FDDI concentrator

FDDI concentrator

router

router

Backbone

Workgroup

workstation

workstation

workstation

FDDI concentrator

server


workstation

workstation

Sub-workgroup


FDDI concentrator

servers


workstation

workstation

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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


File servers

Compute servers

Database servers

FDDI concentrator

FDDI concentrator

FDDI concentrator

router

router

Backbone

Workgroup

workstation

workstation

workstation

FDDI concentrator

server


workstation

workstation

Sub-workgroup


FDDI concentrator

servers


workstation

workstation

22

LAN Summary

Fibre OpticUTP/STPThick/ThinMedia

DUAL RINGRING/STARBUS/STARPhysical

SequentialSequentialBroadcastLog. Top

Modified TPToken PassingCSMA/CDAccess Meth.

FDDIToken RingEthernet

Phy

sica

l L

ayer

1 fibre distributed data interface 100mbps –1986 ansi - x3t9.5 committee –supports ieee 802.5...

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