Lect06 Ethernet

8/10/2019 Lect06 Ethernet

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1.# 1

Data Communication and

Networking

Ethernet and Wireless LAN

IEEE802 Standard for LANS


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1.# 2

Ethernet Evolution

IEEE802.3 Ethernet Frame


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1.# 3

Addressing

Each station on an Ethernet network (such as a PC,

workstation, or printer) has its own network interface card

(NIC).TheNICfitsinsidethestationandprovidesthestation

withalink-layeraddress.TheEthernetaddressis6bytes(48

bits), normally written inhexadecimalnotation, witha colon

betweenthebytes.

Implementation of standard Ethernet


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1.# 4

Access Method

SincethenetworkthatusesthestandardEthernetprotocolis

a broadcast network,weneed touseanaccessmethod to

controlaccesstothesharingmedium.ThestandardEthernet

choseCSMA/CDwith1-persistentmethod.

10BASE5 Implementation


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1.# 5

10BASE-T Implementation

Collision domains


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1.# 6

Switched Ethernet

Full duplex switched Ethernet


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1.# 7

IEEE802.3u Fast Ethernet

IEEE802.3z Gigabit Ethernet

Theneedforanevenhigherdatarateresultedinthedesign

of the Gigabit Ethernet Protocol (1000 Mbps). The IEEE

committee calls it the Standard 802.3z. The goals of the

GigabitEthernetweretoupgradethedatarateto1Gbps,but

keeptheaddresslength,theframeformat,andthemaximum

andminimumframelengththesame.


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1.# 8

MAC Sublayer

AmainconsiderationintheevolutionofEthernetwastokeep

the MAC sublayer untouched. However, to achieve a data

rateof1Gbps,thiswasnolongerpossible.GigabitEthernet

has two distinctive approaches for medium access: half-

duplexandfull-duplex.Almostall implementationsofGigabit

Ethernetfollowthefull-duplexapproach,sowemostlyignore

thehalf-duplexmode.

Encoding in Gigabit Ethernet

IEEE802.3ab


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1.# 9

Gigabit Ethernet implementations

IEEE802.3ae 10-Gigabit Ethernet

Inrecentyears,therehasbeenanotherlookintotheEthernet

for use in metropolitan areas. The idea is to extend the

technology,thedatarate,andthecoveragedistancesothat

theEthernetcanbeusedasLANandMAN,MetroEthernet

orMetroLAN.


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1.# 10

10-GbE implementations

IEEE802.3ba 40/100-Gigabit Ethernet

40 Gbit/s and 100 Gbit/s Ethernet. 40 Gbit/s over 1m

backplane,10 mCucableassembly(4x25Gbitor10x10Gbit

lanes) and 100 mofMMF and 100 Gbit/s up to 10 m of Cu

cableassembly,100mof MMF or40 kmof SMF respectively.


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1.# 11

Hierarchical Ethernet LAN

Three categories of connecting devices


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1.# 12

Layer 1: Hub

A hub is a device that operates only in the physical layer.

Signals that carry information within a network can travel a

fixed distance before attenuation endangers the integrity of

thedata.Arepeaterreceivesasignaland,beforeitbecomes

tooweakorcorrupted, regeneratesand retimes the original

bitpattern.

Layer2: Link-Layer Switches

A link-layerswitch (or switch) operates in both the physical

and the data-link layers. As a physical-layer device, it

regeneratesthesignalitreceives.Asalink-layerdevice,the

link-layerswitchcanchecktheMACaddresses(sourceand

destination)containedintheframe.


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1.# 13

Ethernet Switch

Learning switch


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Loop problem in a learning switch Part C)

Loop problem in a learning switch Part D)


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1.# 16

System of connected LANs and its graph Part a)

System of connected LANs and its graph Part b)


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1.# 17

Finding the shortest path and the spanning tree

Forwarding and blocking ports after using spanning

tree algorithm


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Layer 3: Routers and Layer3 Switch

Virtual LAN

AstationisconsideredpartofaLANifitphysicallybelongsto

that LAN. The criterion ofmembership is geographic.What

happensifweneedavirtualconnectionbetweentwostations

belonging to two different physical LANs?We can roughly

define a virtual local area network (VLAN) as a local area

networkconfiguredbysoftware,notbyphysicalwiring.


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1.# 19

A switch connecting three LANs

A switch using VLAN software


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Two switches in a backbone using VLAN

VLAN with Ethernet Switches


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1.# 21

VLAN Membership

Vendors use different characteristics such as interface

numbers, port numbers,MAC addresses, IP addresses, IP

multicast addresses, or a combination of two or more of

these.

Single Point of Failure and 802.1D


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1.# 22

Switch Purchasing Considerations

NumberandSpeedsofPorts

Buyersmust decide on thenumber of ports needed and

thespeedofeach

Buyers often can buy a prebuilt switch with this

configuration

Store-and-Forward Versus Cut-Through Switching

Store-and-forward switches receive the entire frame before

sendingbitsbackout

Cut-through switches send the frame out after only a few

octets

Cut-through switches reduce latency, but this is rarely

importantattodaysswitchspeeds


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1.# 23

Manageability

SNMPManagercontrolsmanymanagedswitches

Manageability

Polling enables managers to collect data and diagnose

problems

Switches can be fixed remotely by changing their

configurations


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Manageability

Managerprovidesthenetworkadministratorwithsummary

performancedata

Managedswitchesaresubstantiallymore expensive than

unmanagedswitches

However,inlargenetworks,thesavingsinlaborcostsand

rapid responseareworth it, reducing the TCO compared

withunmanagedswitches

Switches fit into standard

19-inchwide(48-cmwide)

equipmentracks

Switchheightsusuallyare

multiplesof1U(1.75inor

4.4cm)

Physical and Electrical Features

19 inches

(48 cm)


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1.# 25

Fixed-port switches

Noflexibility:Thenumberofportsisfixed

1or2Utall

Mostworkgroupswitchesarefixed-portswitches

Stackable switches

Fixednumberofports

1Uor2Utall

High-speedinterconnectbusconnectsstackedswitches

Portscanbeaddedinincrementsofasfewas12


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Modular switches

1Uor2Utall

Containoneorafewslots

Eachslotmodulecontains1to4ports

Module

SeveralUtall

Containseveralexpansion

slots

Each expansion board

containsseveralslots

Most core switches are

chassisswitches

Chassis switches


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IEEE802.3at Power Over Ethernet

Switchesrequireelectricalpower

Inaddition,switchescanprovideelectricalpowertodevices

connectedbyUTPcables

WithPoE,switchescansupply25.5WDCpowertodevices

connectedbyUTPcables

IEEE802.3az Energy-Efficient Ethernet


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1.# 28

Wireless LANs

Isolated LANs: wired versus wireless


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1.# 29

Connection of a wired LAN and a wireless LAN to

other

Access Control

Maybe the most important issue we need to discuss in a

wirelessLANisaccesscontrolhowawirelesshostcanget

accesstothesharedmedium(air).TheCSMA/CDalgorithm

doesnotworkinwirelessLANsforthreereasons:

Wireless hosts do not have enough power to send and

receiveatthesametime.

ThehiddenstationproblempreventscollisiondetectionThedistancebetweenstationscanbegreat.


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Hidden station problem

Hidden station problem


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IEEE 802.11 PROJECT

IEEEhasdefinedthespecificationsforawirelessLAN,called

IEEE802.11,whichcoversthephysicalanddata-linklayers.

It issometimes calledwirelessEthernet. Insomecountries,

including the United States, the public uses the term WiFi

(short for wireless fidelity) as a synonym for wireless LAN.

WiFi,however,isawirelessLANthatiscertifiedbytheWiFi

Alliance.

Architecture

Thestandarddefinestwokindsofservices:thebasicservice

set(BSS)andtheextendedserviceset(ESS).


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1.# 32

Basic service sets BSSs)

Extended service set ESS)


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MAC Sublayer

IEEE 802.11 defines two MAC sublayers: the distributed

coordination function (DCF) and point coordination function

(PCF). Next figure shows the relationship between the two

MACsublayers,theLLCsublayer,andthephysicallayer.We

discuss the physical layer implementations later in the

chapterandwillnowconcentrateontheMACsublayer.

MAC layers in IEEE 802.11 standard


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NAV

CSMA/CA and NAV

Example of repetition interval


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Frame format

Specifications


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802.11 Wireless Access Points and NICs

Bluetooth

BluetoothisawirelessLANtechnologydesignedtoconnect

devices of different functions when they are at a short

distance from each other. Bluetooth was standardized as

IEEE802.15.1, but the standard isno longermaintained.A

BluetoothLANisanadhocnetwork.Thedevices,sometimes

calledgadgets,findeachotherandmakeanetworkcalleda

piconet.


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Piconet

Scatternet


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Single-secondary communication

Multiple-secondary communication


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1.# 39

Other Local Wireless Technologies

UWB

ZigBee

RFIDs

NFC

Software-definedradio

RFID Radio Frequency ID) Tags

LikeUPCtagsbutreadableremotely

Inmost cases, the radio signal from the reader provides

powerfortheRFIDtag

TheRFID tag uses this power to send informationabout

itself

Battery-operated RFID tags can send farther and send

moreinformation


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1.# 40

Near Field Communication

Software-Defined Radio

Canimplementmultiplewirelessprotocols

Noneedtohaveseparateradiocircuitsforeachprotocol

Reducesthecostofmulti-protocoldevices


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Mobile WiMAX

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Lect06 Ethernet

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