updated 12/2001 1

Emerged TechnologiesFDDI

Nirmala Shenoy

Information Technology Department

Rochester Institute of Technology

updated 12/2001 2

FDDI

• Purpose– Fiber Distributed Data Interface I & II– High Capacity LAN – fiber based, twisted pair– High speed backbone to interconnect LANs

• Cost effective

– Dual ring concept – one ring – backup– Can be extended to 200km

updated 12/2001 3

FDDI

• Topology– Station can be connected on 2 rings or 1 ring– Dual Attachment Station – Class A– Single Attachment Station – Class B– Wiring Concentrator

updated 12/2001 4

FDDI

• Topology

Wiring concentrator

Class B

Class B

Class A

Class A

updated 12/2001 5

FDDI

• Layers

– Data Link layer• Logic Link control

• MAC layer

– Token handling

– Error checking

– Data link Addressing

updated 12/2001 6

FDDI

• Layers

– Physical Layer• Physical sub Layer – PHY

– Coding clocking, data framing – independent of physical medium

• Physical Medium Dependent – PMD– Power level control, cables, connections etc

updated 12/2001 7

FDDI

• Layers

– Station Management – SMT• Spans MAC and PHY (full)• Node configuration• Ring initialization• Connection management• Error Detection & recovery

updated 12/2001 8

FDDI

• PDUs– FDDI frame – a number of fields

• SD- Start Delimiter

• FC – Frame control – type of frame

• DA, SA – Destination and Source Addresses

• I – User Information

• FCS – Frame Check Sequence

• FS – Frame Status

• ED – End delimiter

updated 12/2001 9

FDDI

• Other Aspects

– FDDI backbone interconnect

– As a MAN – extended distance• Bridges, routers

– FNS

updated 12/2001 10

FDDI

• Other Aspects

– FDDI vs ATM

– FDDI II – very slow progress

– Issues on twisted pair use

updated 12/2001 11

FDDI

• Conclusions

– Dual Ring protocol

– Self healing capability

– Can not Scale well – Broadband ? Gigabits?

– Limited capacity