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Other LAN Technologies. LAN Standards. 802 Working Groups 802.3Ethernet LANs 802.5Token-Ring Networks 802.11Radio LANs 802.12100VG-AnyLAN. 802.5 Token-Ring Network Standard. Championed by IBM Official IEEE and OSI standard, but most vendors follow IBM extensions to the standard

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Other LAN Technologies

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Other lan technologies l.jpg

Other LAN Technologies


Lan standards l.jpg

LAN Standards

  • 802 Working Groups

    • 802.3Ethernet LANs

    • 802.5Token-Ring Networks

    • 802.11Radio LANs

    • 802.12100VG-AnyLAN


802 5 token ring network standard l.jpg

802.5 Token-Ring Network Standard

  • Championed by IBM

    • Official IEEE and OSI standard, but most vendors follow IBM extensions to the standard

  • More reliable than 802.3 Ethernet LANs

  • More complex and therefore more expensive

  • Lower market share than Ethernet LANs

    • Mostly in firms with large IBM mainframe networks

    • Tightly integrated into SNA

  • Read a tutorial in token-ring networks


Ring topology in token ring networks l.jpg

Ring Topology in Token-Ring Networks

Station

C

Station

B

Station B only receives frames from Station A and only transmits frames to Station C

Frame

Ring

Ring

Frame

Station

A

Station

D

Station

E


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Problem with Rings

  • If the ring breaks, LAN stops

    • Signals must go all the way around the ring, back to the sender

    • This becomes impossible


Use a double ring l.jpg

Use a Double Ring

  • One is unused in normal operation

  • If there is a break, the ring is wrapped

    • Still a ring

Normal

Wrapped


Utp and stp wiring l.jpg

UTP and STP Wiring

Plastic Cover (Non-Shielding)

Twisted

Pair

Unshielded

Twisted Pair

(UTP)

Twisted

Pair

Outer Shield

Around Bundle

Twisted

Pair

Shielded

Twisted Pair

(STP)

Twisted

Pair

Shielding Around Pair


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STP vs. UTP

  • STP

    • Little interference

    • Thick: difficult to install

    • Expensive

  • UTP

    • Thin: easy to install

    • Inexpensive

    • Interference is rarely a practical problem

    • Does the job at a reasonable price, so dominates


Access units in a ring l.jpg

Access Units in a Ring

STP link between

Access Units

Access Unit

Access Unit

Access Unit

Access Unit

STP link

from Station

to Access

Unit

UTP Link

from Station

to Access

Unit

Stations

Station


Within the access unit l.jpg

Within the Access Unit

  • The ring is retained

  • Powered-up NICs added automatically

  • Powered-off NICs bypassed automatically

Bypassed Node

Ring

NIC

NIC

NIC

Missing

NIC


Token passing in 802 5 token ring networks l.jpg

Token Passing in 802.5 Token-Ring Networks

Station B may only transmit when it receives a special frame called a token.

Station

B

Token


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Ethernet (802.3) vs Token-Ring (802.5)

  • Physical Layer

    • Ethernet primarily uses UTP wiring

    • Token-Ring Networks primarily use shielded twisted pair (STP) wiring

  • Topology (Layout) of the Wiring

    • Ethernet always uses bus (broadcast) topology

    • Token-Ring always uses a ring topology (connectivity)

  • Access Control

    • (Control of When Stations May Transmit)

    • Ethernet always uses CSMA/CD

    • Token-Ring always uses token passing


Ethernet 802 3 vs token ring 802 513 l.jpg

Ethernet (802.3) vs Token-Ring (802.5)

  • Speed

    • Ethernet primarily 10 Mbps (moving to 100 Mbps and gigabit speeds)

    • Token-Ring Networks usually at 16 Mbps

    • TRNs can get closer to full capacity because token passing is more efficient than CSMA/CD at high traffic loads

    • Priority levels for real-time traffic (video teleconferencing, etc.)

  • Cost

    • TRN is more complex, so NICs cost much more

    • TRN has low market share; low vendor competition adds to high NIC costs

    • Most firms do not find the benefits of TRNs to outweigh the costs


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Shared Media LANs

  • Ethernet (802.3) and Token-Ring Networks (802.5) are Shared Media LANs

    • Only one station may transmit at any moment.

    • Every station hears every transmission

    • Stations must wait their turn to transmit


Congestion and latency in shared media lans l.jpg

Congestion and Latency in Shared Media LANs

Station B

is Transmitting

But Must

Stop Soon

Station A

Must Wait

to Transmit

Station C

Must Wait

to Transmit

Shared Media LAN

Transmission


Congestion and latency l.jpg

Congestion and Latency

  • As the number of stations on a shared media LAN increases...

    • Traffic increases, so

    • Stations must wait longer to transmit

    • Latency (delay) increases

    • This is called congestion

  • At 200-300 stations, a 10 Mbps (4-16 Mbps) shared media LAN becomes saturated


100 mbps lans l.jpg

100 Mbps LANs

  • Reducing Congestion

    • One way to decrease congestion is to increase LAN speed from 10 Mbps to 100 Mbps or higher

    • Each transmission will be briefer, because it can be transmitted faster

    • Therefore more stations can share the LAN before saturation occurs

    • Only postpones the problem


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FDDI Network

FDDI Ring


Slide19 l.jpg

FDDI

  • FDDI

    • Fiber distributed data interface

    • Token-ring technology (but incompatible with 802.5)

    • 100 Mbps

    • Mature (1987)

    • 200 km maximum diameter: popular for connecting LANs to local internets, not to connect desktops.

    • Priority levels for real-time traffic (voice, video)

    • Expensive NICs and other equipment

    • Read a tutorial in FDDI


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100Base-TX

  • Many install 100Base-TX instead of 10Base-T Today

  • Requires 100 Mbps hubs instead of 10 Mbps

  • Requires 100 Mbps NICs instead of 10 Mbps

    • Some hubs can also serve 10Base-T NICs, so not all stations have to be upgraded at once

  • Uses Category 5 wiring, making upgrading easy


Upgrading from 10base t to 100base t l.jpg

Upgrading from 10Base-T to 100Base-T

  • Need New Hub

    • All 100Base-TX is expensive

    • Often many 10Base-T hubs for client PCs

    • A few 100Base-TX hubs for servers

  • Need New NICs

    • Only in stations with 100Base-T NICs

  • Retain Old Wiring

    • If Cat 5

    • Avoids a major expense


Ethernet 100base tx network l.jpg

Ethernet 100Base-TX Network

100Base-TX Hub

100Base-TX Hub

~50

maximum

100 m

Segment

Maximum

100 m

Segment

Maximum

- 5 UTP wiring

- NICs are replaced

Station A

Station B

Station C


Ethernet 100base tx network23 l.jpg

Ethernet 100Base-TX Network

  • The most popular 100Base-X standard, runs over existing 5 UTP wire of 10Base-T

  • Only two segments, length ~200m

  • Can mix 10 Base-T and 100Base-T stations/NICs with hubs that take both types

  • Use the same 802.3 MAC standard of 10 Base-T

  • Market has chosen Ethernet 100Base-TX for desktop connection over FDDI

  • Read classic tutorial on Fast Ethernet


1000base x gigabit ethernet l.jpg

1000Base-X (Gigabit Ethernet)

  • 1000 Mbps

  • Usually used to link 100Base-X hubs

1000Base-X Hub

100Base-T Hubs


1000base x l.jpg

1000Base-X

  • Family of Standards (802.3z)

  • 1000Base-LX

    • Long-wave (lower frequency) laser

    • 550 meters on multimode optical fiber

    • 3 km on single mode fiber

  • 1000Base-SX

    • Short-wave ( higher frequency) laser

    • 300 meters on 62.5 micron multimode fiber


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Full Duplex Ethernet

  • CSMA/CD is half duplex

    • Only one station may transmit at a time

    • Others must wait

    • Because transmission system is shared

  • If station or hub connects directly to a hub,

    • The access line is not shared

    • Some 100Base-X and 1000Base-X hubs and NICs support full duplex operation

    • Disable CSMA/CD

    • 802.3x standard


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