Explained the computer networks, computer networks' classification, networks architectures, network topologies,Network Communications Standards,etc.

1. Network
 Introduction to Networks:
A network isa collectionof computersanddevicesconnectedtogether
Viacommunicationsdevicesandtransmissionmedia.
 Usedto share resources,forexample:data,information,hardware andsoftware
 Cost efficient
 Withoutnetworkslife isveryhard
 School networks,officenetworks,office networks,etc.
 A value-addednetwork(VAN) isathird-partybusinessthatprovidesnetworkingservicesfor
a fee.
 Types or Classification of Networks:
Networksare usuallyclassifiedaslocal areanetwork(LAN),metropolitanareanetwork(MAN),orwide
area network(WAN).
1. LAN:
 Standsfor Local AreaNetwork
 Coversa small geographical areasuchas a home,school, computerof laboratory,office
buildingorcloselypositionedgroupbuildings.
 Each computeron networksisknownasa node
 Sharesresourcessuchas printers,large harddisks,andprograms.
 WLAN standsforWire-lessLocal AreaNetwork
 Withoutphysical wires
 Communicatesviaanaccesspointwitha wiredLAN to accessresources
2. MAN:
 Standsfor MetropolitanAreaNetwork
 Can be createdby connectingLocal AreaNetworks(LANs) typicallyone ormore
 Coverslargerareassuch as city or town
 Handlesa bulkof communicationsactivityacrossthe region
 Managed bya consortiumof usersorby a single networkprovider

2. 3. WAN:
 Standsfor Wide AreaNetwork
 Coversa large geographicareasuch as: a city,country,or the world
 It’sa large networkorcan consistsof two or more LANs
 Internetisthe world’slargestWAN
 Network Architecture:
The designof computers,devices,andmediainanetwork,sometimescalledthe network architecture,
iscategorizedaseitherclient/serverorpeer-to-peer.
1. Client/Server:
On a client/servernetwork,one ormore computersact as a server;the othercomputersonthe
networkrequestservicesfromthe server.
 A servercontrolsaccess tothe hardware,software,andotherresourcesonthe network
 A serverprovidesacentralizedstorage areaforprograms,data,and information
 The clientsare othercomputersandmobile devicesthatrelyonthe serverforitsresources.
 A servermightstore a database of customers.Clientsonthe network(companyemployees)
access the customerdatabase onthe server.
 A client/servernetworktypicallyprovidesanefficientmeanstoconnecttenormore
computers
 Most client/servernetworksrequireapersontoserve as a networkadministratorbecause
of the large size of the network
 Some servers,called dedicatedservers,performaspecifictaskandcan be placedwithother
dedicatedserverstoperformmultiple tasks.Forexample,afile serverstoresandmanages
files.A printservermanagesprintersandprintjobs.A database serverstoresandprovides
access to a database .A networkservermanagesnetworktraffic(activity).
2. Peer-to-Peer:
 Each computer on a peer-to-peer network shares its hardware and software with other
computers on the network.
 peer-to-peer network is a simple network
 Each computer, called a peer
 inexpensive network
 typically connects fewer than ten computers

3.  Each computer has equal responsibilities and capabilities, sharing hardware (such as a
printer), data, or information with other computers on the peer-to-peer network
 Each computer stores files on its own storage devices each computer on the network
contains both the network operating
 system and application software
 All computers on the network share any peripheral
 device(s) attached to any computer
 Peer-to-peer networks are ideal for very small businesses and home users
 Network Topologies:
A networktopologyreferstothe layoutof the computersanddevicesina communicationsnetwork.
Three commonlyusednetworktopologiesare bus,ring,andstar. Networksusuallyuse combinationsof
these topologies.
1. BUS NETWORK:
 A bus network consists of a single central cable, to which all computers and other devices
connect.
 The bus is the physical cable that connects the computers and other devices
 The bus in a bus network transmits data, instructions, and information in both directions.
 Whena sendingdevice transmitsdata,the address of the receiving device is included with
the transmission so the data is routed to the appropriate receiving device.
 Bus networks are popular on LANs because they are inexpensive and easy to install.
 Computersandotherdevicescanbe attachedand detachedatany pointon the buswithout
disturbing the rest of the network
 Failure of one device usually does not affect the rest of the bus network.
 The bus itself might become inoperable.
2. RING NETWORK
 On a ring network,acable formsa closedloop(ring) withall computersanddevices
arrangedalongthe ring
 Data transmittedona ring networktravelsfromdevicetodevice aroundthe entire ring,in
one direction
 Whena computeror device sendsdata,the data travelstoeach computeronthe ring until
it reachesitsdestination.
 If a computeror device ona ringnetworkfails,all devicesbefore the faileddevice are
unaffected,butthose afterthe faileddevice cannotfunction.
 If a computeror device ona ringnetworkfails,all devicesbefore the faileddevice are
unaffected,butthose afterthe faileddevice cannotfunction.
3. STAR NETWORK
 On a star network,all of the computersanddevices(nodes) onthe networkconnecttoa
central device,thusformingastar.

4.  Two typesof devicesthatprovide acommoncentral connectionpointfornodesonthe
networkare a hub and a switch.
 All data thattransfersfromone node to anotherpassesthroughthe hub/switch.
 Star networksare fairlyeasytoinstall andmaintain.Nodescanbe addedtoand removed
fromthe networkwithlittleornodisruptiontothe network.
 On a star network,if one node fails,onlythatnode isaffected.
 The other nodescontinue tooperate normally.If the hub/switchfails,however,the entire
networkisinoperableuntil the device isrepaired.
4. MeshTopology:
 Everydevice inthe networkisphysicallyconnectedtoevery otherdevice inthe network.
 A message canbe senton differentpossible pathsfromsource todestination.
 It ismostlyusedinwide areanetwork.
 If one linkbecomesunusable,itdoesnotharmthe entire system.
 It iseasyto troubleshoot.
 A full meshnetworkcanbe veryexpensive.
 It isdifficulttoinstall andreconfigure.
5. Tree topology:
 A tree topologycombinesthe characteristicsof busandstar topology
 It connecteddifferentgroupsof computerattachedinstartopology.
 The groups are connectedbusbackbone cable.
 Tree topologyisusedforthe expansionof anexistingnetwork.
 It providespoint-to-pointwiringforindividual segments.
 Network Communications Standards:
A networkstandard definesguidelinesthatspecifythe waycomputersaccessthe mediumtowhich
theyare attached,the type(s) of mediumused,the speedsusedondifferenttypesof networks,
and the type(s) of physical cable and/orthe wirelesstechnologyused.
i. Ethernet:
 Ethernet is the traditional technology for connecting wired local area networks (LANs),
enabling devices to communicate with each other via a protocol.
 The Ethernet standard defines guidelines for the physical configuration of the network, e.g.
cabling, network cards, and nodes
 It’s a networking technology commonly used in local area networks,metropolitan area networks
and wide area networks

5.  Commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3
 Ethernet is based on a bus topology, but its networks can be wired in a star pattern
 Ethernet standard defines guidelines for the physical configuration of the network, e.g., cabling,
network cards,and nodes
 Ethernet is the most popular LAN standard
 Ethernet networks often use cables to transmit data.
 It is relatively inexpensive and easy to install and maintain.
 An Ethernet cable is the physical, encased wiring over which the data travels.
 If two computers on an Ethernet network attempt to send data at the same time, a collision
occurs, and the computers must attempt to send their messages again
ii. TokenRing:
 The token ring standard defines guidelines for the physical configuration of a network
 Tokenringstandard specifiesthatcomputersanddevicesonthe networkshare orpassa special
signal,calledatoken,ina unidirectional mannerandina presetorder
 tokenisa special seriesof bitsthatfunctionslike atick-et
 The device withthe tokencantransmitdata overthe network
 Onlyone tokenexistspernetwork
 itsensuresthatonlyone computertransmitsdataat a time
 Token ring is based on a ring topology (although it can use a star topology).
 The token ring standard defines guidelines for the physical configuration of a network
 Others use a special type of wiring that allows up to 260 connections.
iii. TCP/IP:
 TCP/IP is a network standard
 Stands for Transmission Control Protocol/Internet Protocol, specifically a protocol, that defines
how messages (data) are routed from one end of a network to the other
 TCP/IP describes rules for dividing messages into small pieces, called packets
 Provides addresses for each packet; checking for and detecting errors; sequencing packets; and
regulating the flow of messages along the network
 . TCP/IP has been adopted as a network standard for Internet communications
 all hosts on the Internet follow the rules defined in this standard
 Internet communications also use other standards, such as the Ethernet standard, as data is routed
to its destination.
 When a computer sends data over the Internet, the data is divided into packets. Each packet
contains the data, as well as the recipient (destination), the origin (sender), and the sequence
information used to reassemble the data at the destination. Each packet travels along the fastest
individual available path to the recipient’s computer via communications devices called routers.

6. iv. 802.11(WI-FI):
 Developed by IEEE, 802.11 also known as Wi-Fi (wireless fidelity)
 wireless Ethernet, is a series of network standards that specifies how two wireless devices
communicate over the air with each other
 Using Wi-Fi, computers or devices that have the appropriate wireless capability communicate via
radio waves with other computers or devices
 . The Wi-Fi standard uses techniques similar to the Ethernet standard to specify how physically to
configure a wireless network
 One popular use of the Wi-Fi standard is in hot spots that offer mobile users the ability to connect
to the Internet with their wireless computers and devices
 Many homes and small businesses also use Wi-Fi to network computers and devices together
wirelessly
v. BLUETOOTH:
 Bluetooth is a standard, specifically a protocol that defines how two Bluetooth devices use short-
range radio waves to transmit data
 To communicate with each other, Bluetooth devices often must be within about 10 meters (about
33 feet)
 it can be extended to 100 meters with additional equipment
 Examples of Bluetooth devices can include desktop computers, notebook computers, handheld
computers, PDAs,smart phones, headsets,microphones, digital cameras,fax machines, and
printers.
vi. UWB:
 UWB, which stands for ultra-wideband
 It is a network standard that specifies how two UWB devices use short-range radio waves to
communicate at high speeds with each other
 For optimal communications, the devices should be within 2 to 10 meters (about 6.5 to 33 feet) of
each other
 Examples of UWB uses include wirelessly transferring video from a digital video camera
 downloading media to a portable media player
 Or displaying a slide show on a projector.
vii. IrDA:
 Standsfor InfraredData Association

7.  computersanddevicesuse the IrDA specificationtotransmitdatawirelesslytoeachothervia
infrared(IR) lightwaves
 Infraredrequiresaline-of-sighttransmission
 The sendingdevice andthe receivingdevice mustbe inline witheachothersothatnothing
obstructsthe path of the infraredlight wave.
 The sendingdevice andthe receivingdevice mustbe inline witheachothersothatnothing
obstructsthe path of the infraredlightwave.
viii. RFID:
 RFID stands for Radio Frequency Identification
 it’s a standard, specifically a protocol that defines how a network uses radio signals to
communicate with a tag placed in or attached to an object, an animal, or a person
 The tag consists of an antenna and a memory chip that contains the information to be transmitted
via radio waves
 Through an antenna, an RFID reader reads the radio signals and transfers the information to a
computer or computing device
 Readers can be handheld or embedded in an object such as a doorway or tollbooth.
ix. WIMAX:
 WiMAX stands for Worldwide Interoperability for Microwave Access
 It’s also known as 802.16
 It’s a newer network standard developed by IEEE that specifies how wireless devices
communicate over the air in a wide area
 Using the WiMAX standard, computers or devices with the appropriate WiMAX wireless
capability communicate via radio waves with other computers or devices via a WiMAX tower.
 The WiMAX tower, which can cover up to a 30-mile radius, connects to the Internet or to another
WiMAX tower
 The WiMAX standard provides wireless broadband Internet access at a reasonable cost over long
distances to business and home users
 The WiMAX standard, similar to the Wi-Fi standard
 It connects mobile users to the Internet via hot spots
 The next generation of game consoles also plans to support the WiMAX standard.
x. WAP:
 Stands for Wireless Application Protocol

8.  is a standard, specifically a protocol that specifies how some wireless mobile devices such as
smart phones and PDAs can display the content of Internet services such as the Web, e-mail, chat
rooms, and newsgroups
 users can check weather,sports scores,and headline news from their WAP-enabled smart phone
or PDA
 To display a Web page on a smart phone, the phone should contain a micro browser
 WAP uses a client/server network.
 The wireless device contains the client software,which connects to the Internet service provider’s
server
 HOME NETWORKS
 Many home usersare connectingmultiple computersanddevicestogetherinahome
network.Eachnetworkedcomputerinthe house hasthe followingcapabilities:
 Connectto the Internetat the same time.
 Share a single high-speedInternetconnection.
 Accessfilesandprogramsonthe othercomputersinthe house.
 Share peripheralssuchasa printer,scanner,external harddisk,orDVDdrive.
 Playmultiplayergameswithplayersonothercomputersinthe house.
 Connectgame consolestothe Internet.
 Subscribe toand use Internettelephony.
 Many vendorsofferhome networkingpackagesthatincludeall the necessaryhardware and
software tonetworkyourhome usingwiredorwirelesstechniques.
 An intelligenthome networkextendsthe basichome networktoinclude featuressuchas
lightingcontrol,thermostatadjustment,andasecuritysystem.
 Wired Home Networks:
As withothernetworks,ahome networkcanuse wires,be wireless,oruse acombinationof
wiredandwireless.
a. ETHERNET:
 Traditional Ethernetnetworksrequire thateachcomputerhave built-innetworking
capabilitiesorcontaina networkcard,whichconnectsto a central networkhubor similar
device withaphysical cable.
 Thismay involve runningcable throughwalls,ceilings,andfloorsinthe house.
 For the average home user,the hardware andsoftware of an Ethernetnetworkcanbe
difficulttoconfigure.
b. POWERLINECABLENETWORK:
 A home powerline cable networkisanetworkthatusesthe same linesthatbringelectricity
intothe house.

9.  Thisnetworkrequiresnoadditionalwiring. One endof acable plugsinthe computer’s
parallel orUSB port and the otherendof the cable plugsina wall outlet
 The data transmitsthroughthe existingpower linesinthe house.
c. PHONELINENETWORK:
 A phone line networkisaneasy-to-installandinexpensive networkthatusesexisting
telephonelinesinthe home.
 One endof a cable connectsto an adaptercard or PC Card in the computerandthe other
endplugsin a wall telephonejack.
 The phone line networkdoesnotinterfere withvoice anddatatransmissionsonthe
telephonelines.
 Wireless Home Networks:
 To networkcomputersanddevicesthatspanmultipleroomsorfloorsina home,itmay be
more convenientto use awirelessstrategy.
 You can take a mobile computeroutside,forexampleinthe backyard,andconnectto the
Internetthroughthe home networkaslongas youare inthe network’srange.
a. Home RF (radio frequency):
 Networkusesradiowaves,insteadof cables,totransmitdata.A HomeRFnetworksends
signalsthroughthe airoverdistancesupto 150 feet.
 A HomeRFnetworkusuallycanconnectupto 10 computers.
b. Wi-Fi:
 Anotherhome networkthatusesradiowavesisa Wi-Fi network,whichsendssignalsovera
widerdistance thanthe HomeRFnetwork — upto 1,500 feetinsome configurations.
 A Wi-Fi home networkismore expensive thanaHomeRFnetwork.
 Each computerthat accessesthe networkneedsbuilt-inwirelessnetworkingcapabilitiesor
a wirelessnetworkcard,whichcommunicateswithawirelessaccesspointora combination
router/wirelessaccesspoint.