Ethernet TutorialEthernet Tutorial

IntroductionIntroduction

LANSLANS•Networks usually confined to a Networks usually confined to a small geographic areasmall geographic area–single building single building

–college campuscollege campus

•The proliferation of LANs worldwideThe proliferation of LANs worldwide–businessbusiness

–educationeducation

ProtocolsProtocols•Standards that allow computers Standards that allow computers to communicate.to communicate.

•Defines Defines – identify one another on a networkidentify one another on a network–the form that the data should take the form that the data should take in transitin transit

–how this information should be how this information should be processed once it reaches its final processed once it reaches its final destinationdestination

Protocols (continued)Protocols (continued)

•Defines Defines (continued)(continued)–procedures for handing lost or procedures for handing lost or damaged transmissions or damaged transmissions or “packets”“packets”

•ExamplesExamples–IPXIPX–TCP/IPTCP/IP–DECnetDECnet–AppleTalkAppleTalk–LATLAT

Protocols (continued)Protocols (continued)

•Protocol independenceProtocol independence–the physical network doesn’t need the physical network doesn’t need to concern itself with the protocols to concern itself with the protocols being carriedbeing carried

–allows multiple protocols to allows multiple protocols to peacefully coexistpeacefully coexist

–allows the builder of a network to allows the builder of a network to use common hardware for a use common hardware for a variety of protocolsvariety of protocols

What is Ethernet?What is

Ethernet?

EthernetEthernet•The most popular LAN technologyThe most popular LAN technology –a good balance between speed, price a good balance between speed, price and ease of installationand ease of installation

•The perfect networking technology The perfect networking technology for most computer users todayfor most computer users today–wide acceptance into the computer wide acceptance into the computer marketplacemarketplace

–the ability to support virtually all the ability to support virtually all popular network protocolspopular network protocols

Ethernet (continued)Ethernet (continued)

•Defined by Defined by the Institute for the Institute for Electrical and Electronic Electrical and Electronic EngineersEngineers (IEEE) (IEEE)

•IEEE Standard 802.3IEEE Standard 802.3–configuring an Ethernetconfiguring an Ethernet

–specifying how elements in a specifying how elements in a network interact with one anothernetwork interact with one another

Media and TopologiesMedia and Topologies

TopologiesTopologies•define how define how “nodes”“nodes” are are connected to one anotherconnected to one another–a node is an active device a node is an active device connected to the networkconnected to the network»computercomputer»repeaterrepeater»bridgebridge»routerrouter

»repeaterrepeater»bridgebridge»routerrouter

Topologies (continued)Topologies (continued)

•Ethernet media are used in two Ethernet media are used in two general configurations or general configurations or topologiestopologies–BusBus

–StarStar

–BusBus

–StarStar

Bus topologyBus topology•consists of nodes strung consists of nodes strung together in series with each together in series with each node connected to a log cable or node connected to a log cable or busbus

•a break will usually cause the a break will usually cause the entire segment to be inoperableentire segment to be inoperable

Star topologyStar topology•links exactly two nodes togetherlinks exactly two nodes together

•a break will only affect the two a break will only affect the two nodes on that linknodes on that link

MediaMedia•Major types of media in use Major types of media in use todaytoday–ThickWireThickWire–Thin coaxThin coax–Unshielded twisted pairUnshielded twisted pair–Fiber opticFiber optic

–ThickWireThickWire–Thin coaxThin coax–Unshielded twisted pairUnshielded twisted pair–Fiber opticFiber optic

ThickWireThickWire•10 BASE5 Ethernet10 BASE5 Ethernet•used for used for “backbones”“backbones”•up to 500m longup to 500m long•as many as 100 nodesas many as 100 nodes•use use “vampire tap”“vampire tap” to connect to connect new nodesnew nodes

•nodes must be spaced exactly in nodes must be spaced exactly in increments of 2.5mincrements of 2.5m

Thin CoaxThin Coax•10BASE2 Ethernet10BASE2 Ethernet•lower cost and easier installationlower cost and easier installation•up to 185m longup to 185m long•as many as 30 nodesas many as 30 nodes•each at least 0.5m aparteach at least 0.5m apart•connected or disconnected at the connected or disconnected at the “T” connectors“T” connectors

Twisted PairTwisted Pair–Level 5: 100MbpsLevel 5: 100Mbps–Level 4: 20MbpsLevel 4: 20Mbps–Level 3: 16MbpsLevel 3: 16Mbps–Level 2 and 1: less than 5MbpsLevel 2 and 1: less than 5Mbps

•10BASE-T Ethernet10BASE-T Ethernet

•uses a star topologyuses a star topology

•up to 100m longup to 100m long

Fiber OpticFiber Optic•10BASE-FL Ethernet10BASE-FL Ethernet•useful against situations of useful against situations of electro-magnetic interference, electro-magnetic interference, lightning strike and so onlightning strike and so on

•up to 2km longup to 2km long•can use for FDDI and other can use for FDDI and other technologies faster than technologies faster than EthernetEthernet

TransceiversTransceivers

TransceiversTransceivers•used to connect nodes to the used to connect nodes to the various Ethernet mediavarious Ethernet media

•known as known as Media Attachment Media Attachment UnitsUnits (MAU) (MAU)

Transceivers (continued)

Transceivers (continued)

•provide an provide an Application User Application User InterfaceInterface (AUI), connector for the (AUI), connector for the computercomputer

•many interface network cards many interface network cards also contain a buit-in 10BASE-T also contain a buit-in 10BASE-T or 10BASE2 transceiveror 10BASE2 transceiver

Examples of TransceiverExamples of Transceiver

–LTX-TLTX-T ((Twisted Pair Transceiver)Twisted Pair Transceiver)

–LTX-TALTX-TA((Twisted Pair Mini Transceiver)Twisted Pair Mini Transceiver)

–LTX-2LTX-2 ((Thin Coax Transceiver)Thin Coax Transceiver)

–LTX-2ALTX-2A((Thin Coax Mini Transceiver)Thin Coax Mini Transceiver)

–LTX-5LTX-5 ((ThickWire Transceiver)ThickWire Transceiver)

–LTX-FL LTX-FL ((Fiber Optic Transceiver)Fiber Optic Transceiver)

–LTX-TLTX-T ((Twisted Pair Transceiver)Twisted Pair Transceiver)

–LTX-TALTX-TA((Twisted Pair Mini Transceiver)Twisted Pair Mini Transceiver)

–LTX-2LTX-2 ((Thin Coax Transceiver)Thin Coax Transceiver)

–LTX-2ALTX-2A((Thin Coax Mini Transceiver)Thin Coax Mini Transceiver)

–LTX-5LTX-5 ((ThickWire Transceiver)ThickWire Transceiver)

–LTX-FL LTX-FL ((Fiber Optic Transceiver)Fiber Optic Transceiver)

RepeatersRepeaters

RepeatersRepeaters•connect two or more Ethernet connect two or more Ethernet segments of any media typesegments of any media type

•provide the signal amplificationprovide the signal amplification

•Splitting a segment into two or Splitting a segment into two or more with a repeater allows a more with a repeater allows a network to grownetwork to grow

Repeaters (continued)Repeaters (continued)

•count in the total node limitcount in the total node limit–e.g. . a Thin Coax segmente.g. . a Thin Coax segment

»185m long185m long

»29 nodes and a repeater29 nodes and a repeater

–e.g. . a ThickWire segmente.g. . a ThickWire segment»500m long500m long

»98 nodes and 2 repeaters 98 nodes and 2 repeaters

Repeaters (continued)Repeaters (continued)

•necessary in star topologiesnecessary in star topologies–one endone end the repeater the repeater –the otherthe other the computer w/ a the computer w/ a transceivertransceiver

•monitor Ethernet to run correctlymonitor Ethernet to run correctly–e.g. . when a break occurse.g. . when a break occurs

»limit the effect of inoperable problems limit the effect of inoperable problems by by “segmenting”“segmenting”, disconnecting the , disconnecting the problem segmentproblem segment

Repeaters (continued)Repeaters (continued)

•The IEEE 802.3 specifications The IEEE 802.3 specifications –describe rules for the maximum describe rules for the maximum number of repeaters in a number of repeaters in a configurationconfiguration

–e.g. . e.g. . the transmission path the transmission path between two nodes between two nodes

the maximum number the maximum number of network segments of network segments between two nodesbetween two nodes

4 4

55

BridgesBridges

BridgesBridges•Function:Function: To connect separate To connect separate

Ethernet togetherEthernet together

• Goal:Goal: To achieve what To achieve what appears toappears to the network the network users to be a users to be a seamless networkseamless network

Bridges (continued)Bridges (continued)

•map the Ethernet addresses of map the Ethernet addresses of the nodes residing on each the nodes residing on each network segmentnetwork segment

•then, allow only the necessary then, allow only the necessary traffic to pass through the bridgetraffic to pass through the bridge

Bridges (continued)Bridges (continued)

•When a packet is received by the When a packet is received by the bridge:bridge:–the bridge determines the the bridge determines the destination and source segmentsdestination and source segments

– If the segments are the sameIf the segments are the same»the packet is dropped (the packet is dropped (“filtered”“filtered”))

– If the segments are differentIf the segments are different»the packet is the packet is “forwarded”“forwarded” on on

Bridges (continued)Bridges (continued)

•prevent all bad or misaligned prevent all bad or misaligned packets form spreading from one packets form spreading from one segment to the otherssegment to the others

•called called “store-and-forward”“store-and-forward” devicesdevices– look at the whole Ethernet packet look at the whole Ethernet packet before making their filtering or before making their filtering or forwarding decisionsforwarding decisions

Ethernet SwitchesEthernet Switches

Ethernet SwitchesEthernet Switches•““Cut-through”Cut-through” switches switches–examining the address information examining the address information contained at the start of the contained at the start of the Ethernet packetEthernet packet

–decrease the amount of time decrease the amount of time required to determine if a packet required to determine if a packet should be filtered or forwarded, should be filtered or forwarded, “latency”“latency”

Ethernet Switches (continued)

Ethernet Switches (continued)

•The term The term “Ethernet Switch”“Ethernet Switch”–any device of multiple ports which any device of multiple ports which is able to filter and forward packets is able to filter and forward packets at nearly the speed of Ethernet at nearly the speed of Ethernet ((“wirespeed”“wirespeed”) regardless of the ) regardless of the techniquetechnique»because store-and-forward bridges because store-and-forward bridges have now increased their speedhave now increased their speed

Ethernet Switches (continued)

Ethernet Switches (continued)

•The term The term “Bridge”“Bridge”–two-port devices which use the two-port devices which use the store and forward techniquestore and forward technique

RoutersRouters

RoutersRouters•filter out network trafficfilter out network traffic

•filter by specific protocolfilter by specific protocol

•born out of the necessity for born out of the necessity for dividing networks logically dividing networks logically instead of physicallyinstead of physically

Routers (continued)Routers (continued)

•An IP router An IP router –divide a network into various subnets divide a network into various subnets

–only traffic destined for particular IP only traffic destined for particular IP addresses can pass between segmentsaddresses can pass between segments

–takes more time than a switch or takes more time than a switch or bridge which only looks at the MAC bridge which only looks at the MAC layerlayer

Routers (continued)Routers (continued)

•The term The term “brouters”“brouters”–devices which have both bridging devices which have both bridging and routing capabilityand routing capability»however switches and bridges however switches and bridges frequently have some router-like frequently have some router-like features such as selective protocol features such as selective protocol filteringfiltering

Network Switch Example

Network Switch Example

Sun (G) Sun (H)Microvax

(F)Workstation (E)

Netware File Server (C)

Macintosh (D)

PC (A) Microvax(B)

LSB4 Switch

LTX-2

LTX-2 LTX-

2LTX-

2

LTX-2

LTX-2

LTX-5

LTX-5

LTX-5

LTX-5

LTX-5

LTX-5

The Spanning Tree

The Spanning Tree

The Spanning TreeThe Spanning Tree•The Spanning Tree Algorithm The Spanning Tree Algorithm –a software device for describing how a software device for describing how switches & bridges can communicate switches & bridges can communicate to avoid network loopsto avoid network loops

–By exchanging packets called BPDUs, By exchanging packets called BPDUs, the switches & bridges establish a the switches & bridges establish a singular path for reaching each singular path for reaching each network segment.network segment.

The Spanning Tree (continued)

The Spanning Tree (continued)

•A switches or bridge port is A switches or bridge port is turned off turned off

– if another pathway to that segment if another pathway to that segment already existsalready exists

The Spanning Tree (continued)

The Spanning Tree (continued)

•The process of passing the BPDU The process of passing the BPDU packets is continuouspackets is continuous–so if a switch or bridge suddenly so if a switch or bridge suddenly fails, fails,

–then the remaining devices will then the remaining devices will reconfigure pathways to allow each reconfigure pathways to allow each segment to be reachedsegment to be reached

The Spanning Tree (continued)

The Spanning Tree (continued)

•network managers design loops network managers design loops into a bridged network into a bridged network –so if a switch or bridge does fail, so if a switch or bridge does fail,

–the Spanning Tree will calculate the Spanning Tree will calculate the alternate route into the the alternate route into the network configuration.network configuration.

Spanning Tree Example

Spanning Tree Example

LTX-5 LTX-5

LTX-5 LTX-5

LB2 #1

LB2 #2

LB2 #3LB2 #4

LTX-2

LTX-2

LTX-2

LTX-2 10BASE2

10BASE210BASE5

10BASE5

AUI CABLEAUI CABLE

AUI CABLE

AUI CABLE

Terminal & Printer Servers

Terminal & Printer Servers

Terminal & Printer Servers

Terminal & Printer Servers

•support the use of following on support the use of following on networksnetworks–terminalsterminals–printersprinters–modems, andmodems, and–other serial devicesother serial devices

•have own network addresseshave own network addresses

•perform more than just a physical perform more than just a physical connection or signalforwarding functionconnection or signalforwarding function

Terminal serverTerminal server•a server which provides network a server which provides network access to serial devicesaccess to serial devices

•support serial printers as well as support serial printers as well as serial terminals serial terminals

•bidirectional devicesbidirectional devices

Printer serverPrinter server•is expected to have at least one is expected to have at least one parallel portparallel port

•may also have one or more serial may also have one or more serial portsports

•unidirectional devicesunidirectional devices

AdvantagesAdvantages•Saving on long-distance cablingSaving on long-distance cabling–because of its multiple portsbecause of its multiple ports

•Enhanced remote monitoring and Enhanced remote monitoring and controlcontrol–because of its inherent intelligencebecause of its inherent intelligence

•Easier to manageEasier to manage–because of its support for protocols because of its support for protocols like SNMPlike SNMP

Advantages (continued)

Advantages (continued)

•Local communicationsLocal communications–able to broadcast messages to all able to broadcast messages to all devices connected to the serversdevices connected to the servers

•Sharing resources and balancing Sharing resources and balancing workloadsworkloads

Advantages (continued)

Advantages (continued)

•Supporting multiple protocolsSupporting multiple protocols

•Supporting workstationsSupporting workstations

•Protocol conversionProtocol conversion

•Staying flexibleStaying flexible