04 LAN Basics

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1999, Cisco Systems, Inc.www.cisco.com

Module 4:LAN Basics

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4-2CSE: Networking FundamentalsLAN Basics 1999, Cisco Systems, Inc.www.cisco.com

Agenda

Ethernet Token Ring

FDDI

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Common LAN Technologies

Ethernet

Token Ring

FDDIFDDI

Dual Ring

TokenRing

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Ethernet

1999, Cisco Systems, Inc. www.cisco.com

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Ethernet and IEEE 802.3

Benefits and background

Ethernet is the most popular physical layer LANtechnology because it strikes a good balance

between speed, cost, and ease of installation Supports virtually all network protocols

Xerox initiated, then joined by DEC & Intel in 1980

Revisions of Ethernet specification

Fast Ethernet (IEEE 802.3u) raises speed from 10Mbps to 100 Mbps

Gigabit Ethernet is an extension of IEEE 802.3which increases speeds to 1000 Mbps, or 1 Gbps

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Ethernet and IEEE 802.3

Several framing variations exist for thiscommon LAN technology

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7/334-7CSE: Networking FundamentalsLAN Basics 1999, Cisco Systems, Inc.www.cisco.com

LANspeed (bps)

100BaseFX

Base = basebandBroad = broadband

Indicates type of cableand maximum length.

If a number,

max. length = # x 100 m

Ethernet Protocol Names

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Ethernet and Fast Ethernet

ProtocolMax. Segment

Length (m)Transmission

Medium Application

10Base2 185 50-ohm coaxial A: Link user stations

10Base5 500 50-ohm coaxial A: Link user stations

10BaseF Refers to 10BaseFB, 10BaseFL, and 10Base FP

10BaseFB 2000 Fiber-optic A: Add segments

10BaseFL 10002000 Fiber-optic A: Operate w/ FOIRL

10BaseFP 500 Fiber-optic Star topo w/out repeaters

10BaseT 100 2-pairs TP Sends link signals

10Broad36 3600 Broadbandcoax A: Broadband100BaseFX 400 2 strands of multimode fiber-optic cable

100BaseT 100 UTP 10BaseT function + more

100BaseT4 100 4 prs Cat 3-5 UTP -

100BaseTX 100 2 prs UTP or STP -

100BaseX Refers to 2 strand/pair 100BaseFX and 100BaseTX

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Ethernet Operation

AA BB CC DD

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Ethernet Operation

AA BB CC DD

D

Data Link

Network

TransportSession

Presentation

Application

Physical

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Ethernet Operation

AA BB CC DD

D

Data Link

Network

TransportSession

Presentation

Application

Physical

B and C

Data Link

Network

TransportSession

Presentation

Application

Physical

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Ethernet Broadcast

D

Data Link

Network

TransportSession

Presentation

Application

Physical

C

Data Link

Network

TransportSession

Presentation

Application

Physical

B

Data Link

Network

TransportSession

Presentation

Application

Physical

A

Data Link

Network

TransportSession

Presentation

Application

Physical

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Ethernet Reliability

B C DA

B C DAFigure 1

Figure 2

Collision

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Collision

C

B C DA

BA D

JAMJAMJAMJAMJAM JAM

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B C DA

Collision

B C DA

JAMJAMJAMJAMJAM JAM

Carrier sense multiple access with

collision detection (CSMA/CD)

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High-Speed Ethernet Options

Fast Ethernet

Fast EtherChannel

Gigabit Ethernet

Gigabit EtherChannel

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What Is Fast EtherChannel?

Grouping of multiple Fast Ethernet interfacesinto one logical transmission path

Scalable bandwidth up to800+ Mbps

Using industry-standardFast Ethernet

Load balancing acrossparallel links

Extendable to GigabitEthernet400 Mb

600 Mb

800 Mb

800 Mb

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1000-Mbps data rate

802.3/Ethernet frames

Full duplex or half duplex

Fiber or copper media

100% compatible with existing:

Network protocols

Network operating systems

Network applications

Network management

20%

80%Workgroup

20%

80%Backbone

What Is Gigabit Ethernet?

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Token Ring


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Token Ring (IEEE 802.5)

History

Developed by IBM in the 1970s; IEEE 802.5spec is totally compatible with Token Ring

Second to Ethernet in popularity Features

Token determines transmission so no collisions

Ideal for applications (such as factory automation)where delay must be predictable and robustnetwork operation is important

More difficult and costly than Ethernet, but littleimpact as more users are added to system

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Token Ring Bandwidth

IBM Token Token RingRing Network IEEE 802.5

Data Rates 4 or 16 Mbps 4 or 16 Mbps

Stations/Seg 260 STP, 72 UTP 250

Topology Star Not specified

Media Twisted-pair Not specified

Signaling Baseband Baseband

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Token Ring Topology

Logically a ring, but physically astar configuration to MAU relays

Shielded orUnshieldedTwisted-Pair

MAU

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Token Ring Operation

AT = 0

T

Token Ring LANs continuously pass atoken or a Token Ring frame

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AT = 0

T Data

AT = 1

T


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AT = 0

T Data

AT = 1

AT = 0

T

T


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Token Ring Summary

Reliable transport, minimized collisions

Token passing/token seizing

4- or 16-Mbps transport

Little performance impact with increased

number of users

Popular at IBM-oriented sites such asbanks and automated factories

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FDDI


Fib Di t ib t d

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Fiber DistributedData Interface (FDDI)

Fiber Distributed Data Interface (FDDI)

Defined by ANSI X3T9.5 spec in mid 1980s

100-Mbps token-

passing network Fiber-optic cable with

max. distance of 2 km

Dual-ring architecturefor redundancy

Used for corporate andcarrier backbones

CDDI

Implements FDDI over STP and UTP cable

Transmits at 100 Mbps over about 100 m

FDDIDual Ring

100 Mbps

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FDDI Network Architecture

Dual-ring architecture

Primary ring for data transmissions

Secondary ring for reliability and robustness

Components Single attachment station (SAS)PCs

Dual attachment station (DAS)Servers

Concentrator

FDDI concentrator Also called a dual-attached concentrator (DAC)

Building block of an FDDI network

Attaches directly to both rings and ensures that any SASfailure or power-down does not bring down the ring

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FDDI Network Example

WANFDDIConcentrator

SAS SAS

DAS

DAS

Primary Ring

Secondary Ring

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FDDI Summary

Features

100-Mbps token-passing network

Single-mode (100 km), double-mode (2 km)

CDDI transmits at 100 Mbps over about 100 m

Dual-ring architecture for reliability

Optical fiber advantages versus copper

Security, reliability, and performance are enhancedbecause it does not emit electrical signals

Much higher bandwidth than copper

Used for corporate and carrier backbones

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Summary

LAN technologies include Ethernet,Token Ring, and FDDI

Ethernet Most widely used

Good balance between speed, cost, and ease of installation

10 Mbps to 1000 Mbps

Token Ring Primarily used with IBM networks

4 Mbps to 16 Mbps

FDDI Primarily used for corporate backbones

Supports longer distances

100 Mbps

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04 LAN Basics

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