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

7

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.

9

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

12

13

FDDI Uses Beaconing

34

14

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.

15

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

16

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.

17

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

18

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

19

Backbone

GOLDMAN: DATACOMM FIG. 05-16

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

Ethernet hubworkstation

workstation

workstation

20

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

– High-bandwidth communication– CAD/CAM Workstations

• Power Users– GUI

GOLDMAN: DATACOMM FIG. 05-16

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

Ethernet hubworkstation

workstation

workstation

21

High-Bandwidth Subgroups• In some cases only 2 or 3 devices such as servers,

require high-bandwidth.• Increased demand

– Distributed Computing– Data Distribution

GOLDMAN: DATACOMM FIG. 05-16

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

Ethernet hubworkstation

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