17 - Networking

8/13/2019 17 - Networking

1/10

How Computer Network Works

In the world of computers, networking is the practice of linking two or more computingdevices together for the purpose of sharing data. Networks are built with a mix of computer hardwareand computer software.

Introduction to Network Types

Networks can be categorized in several different ways. One approach defines the type ofnetwork according to the geographic area it spans. ocal area networks !"Ns#, for example,typically reach across a single home, whereas wide area networks !$"Ns#, reach across cities,states, or even across the world. The Internetis the world%s largest public $"N.

One way to categorize the different types of computer network designs is by their scope orscale. &or historical reasons, the networking industry refers to nearly every type of design as somekind of area network. 'ommon examples of area network types are(

"N ) ocal "rea Network

$"N ) $ireless ocal "rea Network

$"N ) $ide "rea Network

*"N ) *etropolitan "rea Network +"N ) +torage "rea Network, +ystem "rea Network, +erver "rea Network, or

sometimes +mall "rea Network

'"N ) 'ampus "rea Network, 'ontroller "rea Network, or sometimes 'luster

"rea Network

"N ) ersonal "rea Network

-"N ) -esk "rea Network

"N and $"N were the original categories of area networks, while the others have graduallyemerged over many years of technology evolution.

Note that these network types are a separate concept from network topologies such as bus,

ring and star.

" local area network (LAN) supplies networking capability to a group of computers in closeproximity to each other such as in an office building, a school, or a home. " "N is useful for sharingresources like files, printers, games or other applications. " "N in turn often connects to other"Ns, and to the Internet or other $"N.

*ost local area networks are built with relatively inexpensive hardware such as thernetcables, network adapters, and hubs. $ireless "N and other more advanced "N hardware optionsalso exist.

Wireless Local Area Network(WAN)) " wireless "N !or $"N, for wireless local area network,

sometimes referred to as "$N, for local area wireless network# is one in which a mobile user canconnect to a local area network !"N# through a wireless!radio# connection.

1
http://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_wan.htmhttp://compnetworking.about.com/library/glossary/bldef-internet.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-ethernet.htmhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212495,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213380,00.htmlhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_wan.htmhttp://compnetworking.about.com/library/glossary/bldef-internet.htmhttp://compnetworking.about.com/library/glossary/bldef-wan.htmhttp://compnetworking.about.com/library/glossary/bldef-ethernet.htmhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212495,00.htmlhttp://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci213380,00.html


2/10

Wide Area Network !$"N# is a geographically dispersed telecommunications network.The termdistinguishes a broader telecommunication structure from a local area network !"N#. " wide areanetwork may be privately owned or rented, but the term usually connotes the inclusion of public!shared user# networks. "n intermediate form of network in terms of geography is a metropolitanarea network !*"N#.

) 'overs a broad area !i.e., any network whose communications links cross metropolitan,regional, or national boundaries /01#. Or, less formally, a network that uses routers and publiccommunicationslinks/01. 'ontrast withpersonal area networks!"Ns#, local area networks!"Ns#,campus area networks!'"Ns#, or metropolitan area networks!*"Ns# which are usually limited to aroom, building, campus or specific metropolitan area !e.g., a city# respectively. The largest and mostwell)known example of a $"N is the Internet.

Wide Area Networks !$"Ns# span broad geographical distances ) entire regions, states,continents, or the entire globe. The most universal and powerful $"N is the Internet. 'omputersconnect to a $"N through public networks such as the telephone system or private cable systems,or through leased lines or satellites. " *etropolitan "rea Network !*"N# is a large computer networkthat spans a metopolitan area or campus. Its geographic scope falls between a $"N and "N.*"ns provide Internet connectivity for "Ns in a metropolitan region, and connect them to wider

area networks like the Internet.

Network Topology

) In computer networking, topologyrefers to the layout of connected devices. This articleintroduces the standard topologies of networking.

) 2epresents its layout or structure from the point of view of data flow.

Topology in Network Design

Think of a topology as a network%s virtual shape or structure. This shape does not

necessarily correspond to the actual physical layout of the devices on the network. &or example, thecomputers on a home "Nmay be arranged in a circle in a family room, but it would be highlyunlikely to find a ring topology there.

Network topologies are categorized into the following basic types(

3us

2ing

+tar

Tree

*esh

*ore complex networks can be built as hybrids of two or more of the above basic topologies.

Bus Topology

3us networks !not to be confused with the system bus of a computer# use a common backbone toconnect all devices.

" single cable, the backbone functions as a shared communication medium that devicesattach or tap into with an interface connector. " device wanting to communicate with another device

2
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214117,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212495,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214083,00.htmlhttp://en.wikipedia.org/wiki/Wide_area_network#cite_note-Groth-0%23cite_note-Groth-0http://en.wikipedia.org/wiki/Communicationhttp://en.wikipedia.org/wiki/Link_(telecommunications)http://en.wikipedia.org/wiki/Link_(telecommunications)http://en.wikipedia.org/wiki/Wide_area_network#cite_note-Groth-0%23cite_note-Groth-0http://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Campus_area_networkhttp://en.wikipedia.org/wiki/Campus_area_networkhttp://en.wikipedia.org/wiki/Metropolitan_area_networkhttp://en.wikipedia.org/wiki/Internethttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htmhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214117,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212644,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212495,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214083,00.htmlhttp://en.wikipedia.org/wiki/Wide_area_network#cite_note-Groth-0%23cite_note-Groth-0http://en.wikipedia.org/wiki/Communicationhttp://en.wikipedia.org/wiki/Link_(telecommunications)http://en.wikipedia.org/wiki/Wide_area_network#cite_note-Groth-0%23cite_note-Groth-0http://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Campus_area_networkhttp://en.wikipedia.org/wiki/Metropolitan_area_networkhttp://en.wikipedia.org/wiki/Internethttp://compnetworking.about.com/cs/lanvlanwan/g/bldef_lan.htm


3/10

on the network sends a broadcast message onto the wire that all other devices see, but only theintended recipient actually accepts and processes the message.

thernet bus topologies are relatively easy to install and don%t re4uire much cablingcompared to the alternatives. 053ase)6 !7ThinNet7# and 053ase)8 !7ThickNet7# both were popularthernet cabling options many years ago for bus topologies. 9owever, bus networks work best witha limited number of devices. If more than a few dozen computers are added to a network bus,performance problems will likely result. In addition, if the backbone cable fails, the entire networkeffectively becomes unusable.

3us Topology -iagram

This diagram illustrates the bus network topology. " bus topology such as 053ase)6 or053ase)8 thernet uses a single communication backbone for all devices.

Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. "llmessages travel through a ring in the same direction !either 7clockwise7 or 7counterclockwise7#. "failure in any cable or device breaks the loop and can take down the entire network.

To implement a ring network, one typically uses &--I, +ONT, or Token 2ing technology.2ing topologies are found in some office buildings or school campuses.

2ing Topology -iagram

This diagram illustrates the ring network topology. " ring topology such as &--I or +ONT sendsmessages clockwise or counterclockwise through the shared link.

3
http://compnetworking.about.com/cs/sonet/g/bldef_sonet.htmhttp://compnetworking.about.com/cs/sonet/g/bldef_sonet.htm


4/10

tar Topology

*any home networks use the star topology. " star network features a central connectionpoint called a 7hub7 that may be a hub, switchor router. -evices typically connect to the hub with:nshielded Twisted air !:T# thernet.

'ompared to the bus topology, a star network generally re4uires more cable, but a failure inany star network cable will only take down one computer%s network access and not the entire "N.!If the hub fails, however, the entire network also fails.#

+tar Network Topology -iagram

This diagram illustrates the star network topology. " star topology typically uses a networkhub or switch and is common in home networks.

Tree Topology

Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hubdevices connect directly to the tree bus, and each hub functions as the 7root7 of a tree of devices. Thisbus;star hybrid approach supports future expandability of the network much better than a bus !limited in

the number of devices due to the broadcast traffic it generates# or a star !limited by the number of hubconnection points# alone.

Tree Network Topology

This diagram illustrates the tree network topology. " tree topology integrates the star andbus topologies in a hybrid approach to improve network scalability.

4
http://compnetworking.about.com/cs/internetworking/g/bldef_hub.htmhttp://compnetworking.about.com/cs/internetworking/g/bldef_hub.htmhttp://compnetworking.about.com/od/hardwarenetworkgear/g/bldef_switch.htmhttp://compnetworking.about.com/od/hardwarenetworkgear/g/bldef_switch.htmhttp://compnetworking.about.com/cs/routers/g/bldef_router.htmhttp://compnetworking.about.com/cs/internetworking/g/bldef_hub.htmhttp://compnetworking.about.com/od/hardwarenetworkgear/g/bldef_switch.htmhttp://compnetworking.about.com/cs/routers/g/bldef_router.htm


5/10

!es" Topology

*esh topologies involve the concept of routes. :nlike each of the previous topologies,messages sent on a mesh network can take any of several possible paths from source todestination. !2ecall that even in a ring, although two cable paths exist, messages can only travel inone direction.# +ome $"Ns, most notably the Internet, employ mesh routing.

" mesh network in which every device connects to every other is called a full mesh. "sshown in the illustration below, partial mesh networks also exist in which some devices connect onlyindirectly to others.

*esh Network Topology

This diagram illustrates the mesh network topology. " mesh topology provides redundantcommunication paths between some or all devices !partial or full mesh#.

+ummary

Topologies remain an important part of network design theory.


6/10

interfaces. If you use a straight)through cable, one of the two units must, in effect, perform thecross)over function.

Two wire color)code standards apply( I";TI" 8>?" and I";TI" 8>?3.The codes are commonlydepicted with 2@)A8 Backs as follows !the view is from the front of the Backs#(

If we apply the 8>?" color code and show all eight wires, our pin)out looks like this(

Note that pins A, 8, C, and ? and the blue and brown pairs are not used in either standard. Duitecontrary to what you may read elsewhere, these pins and wires are not used or re4uired toimplement 0553"+)T= duplexing))they are Bust plain wasted.

9owever, the actual cables are not physically that simple. In the diagrams, the orange pair of wiresare not adBacent. The blue pair is upside)down. The right ends match 2@)A8 Backs and the left endsdo not. If, for example, we invert the left side of the 8>?" 7straight7)thru cable to match a 8>?" Back))put one 0?5E twist in the entire cable from end)to)end))and twist together and rearrange theappropriate pairs, we get the following can)of)worms(

This further emphasizes, I hope, the importance of the word 7twist7 in making network cables whichwill work.


7/10

Feeping the above principles in mind, we can simplify the diagram for a 8>?" straight)thru cable byuntwisting the wires, except the 0?5E twist in the entire cable, and bending the ends upward.ikewise, if we exchange the green and orange pairs in the 8>?" diagram we will get a simplifieddiagram for a 8>?3 straight)thru cable. If we cross the green and orange pairs in the 8>?" diagramwe will arrive at a simplified diagram for a crossover cable. "ll three are shown below.

L%T& !A'% T !L%

There are only two uni4ue cable ends in the preceding diagrams. They correspond to the 8>?" and8>?3 2@)A8 Backs and are shown to the right.

"gain, the wires with colored backgrounds may have white stripes and may be denoted that way indiagrams found elsewhere. &or example, the green wire may be labeled Green)$hite))I don%tbother. The background color is always specified first.

Now, all you need to remember, to properly configure the cables, are the diagrams for the two cableends and the following rules(

7


8/10

8


9/10

A straig"t$t"ru ca*le "as identical ends+

A crosso,er ca*le "as di--erent ends+

It makes no functional difference which standard you use for a straight)thru cable. ?"patch cable will work in a network with 8>?3 wiring and 8>?3 patch cable will work in a 8>?"network. The electrons couldn%t care less.

!y pre-erence is to use t"e ./0A standard -or straig"t$t"ru ca*les and to start crosso,erca*les wit" a ./0A end+ T"at way all "a,e to remem*er is t"e diagram -or t"e ./0A end1 t"ata straig"t$t"ru ca*le "as two o- t"em1 and t"at t"e green and orange pairs are swapped at t"eot"er end o- a crosso,er ca*le.

T%+ *"F +O* '"3+

0. ull the cable off the reel to the desired length and cut. I have a box of cable at one end of myshop and a mark on the floor 05% away. &or cable lengths which are a fraction of ten feet, I eye)ballthe length as I pull the cable out of the box !also, my feet are about one foot long#. &or longercables, I pull it out to the ten foot mark and go back to the box and pull the remaining fraction oranother ten feet. If you are pulling cables through walls, a hole in the floor, etc., it easier to attachthe 2@)A8 plugs after the cable is pulled. The total length of wire segments between a ' and a hubor between two '%s cannot exceed 055 *eters !H6? feet or about the length of a football field# for0553"+)T= !and 053"+)T#.

6. +trip one end of the cable with the stripper or a knife and diags. If you are using the stripper,place the cable in the groove on the blade !left# side of the stripper and align the end of the cablewith the right side of the stripper. This is about right to strip a little over 0;67 of the Backet off thecable. Turn the stripper about one turn or so. If you turn it much more, you will probably nick thewires. The idea is to score the outer Backet, but not go all the way through. Once scored, youshould be able to twist the end of the Backet loose and pull it off with one hand while holding the restof the cable with the other. If you are using a knife and diags, carefully slit the cable for about aninch or so and neatly trim around the circumference of the cable with the diags to remove the Backet.

H. Inspect the wires for nicks. 'ut off the end and start over if you see any.


10/10

8. :ntwist the pairs and arrange the wires in the order of the desired cable end.&latten the end between your thumb and forefinger. Trim the ends of the wires sothey are even with one another. t is ,ery important t"at t"e unstripped(untwisted) end *e slig"tly less t"an 2345 long+ If it is longer than 0;67 it will beout)of)spec and susceptible to crosstalk. If it less than slightly less than 0;67 it willnot be properly clinched when 2@)A8 plug is crimped on.. &latten again. Thereshould be little or no space between the wires.

>. 9old the 2@)A8 plug with the clip facing down or away from you. ush the wirefirmly into the plug. Now, inspect t"e darn t"ing+++ *e-ore crimping and wastingt"e plug6 ooking through the bottom of the plug, the wire on the far left side willhave a white background. The wires should alternate light and dark from left toright. The furthest right wire is brown. The wires should all end evenly at the frontof the plug. The Backet should end Bust about where you see it in thediagram))right on the line. "ren%t you glad you didn%t crimp the plug

Color Coding

In the cabling industry color coding is used to identify a pair of conductors by its uni4ue number,corresponding to the combination of tip and ring colors. 'opper and fiber color coding are somewhatdifferent, so the tables are split onto copper and fiber sections. lease follow the links below to seethe color code tables, depending on the pair !fiber# count of the cable.

A pair cable%s color code table. very pair uses white as a tip color and one of four !blue, orange,green, brown# ring colors.

pair -igure tip ring2 w"ite *lue4 w"ite orange7 w"ite green8 w"ite *rown

pair -igure tip ring

10

Documents

17 - Networking