The Common Network Devices

7/24/2019 The Common Network Devices

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The common

network devicesComputer networking devices are

units that mediate data in a computer

network and are also called networkequipment. Units which are the last

receiver or generate data are called

hosts or data terminal equipment.
http://commons.wikimedia.org/wiki/File:Network_switches.jpg


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Networking


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Networking

Do you knowme?


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HUBS Hubs connect computers together in a star

topology network. Due to their design, they increase thechances for collisions. Hubs operate in the physical

layer of the OS model and ha!e no intelligence. Hubs"ood incoming packets to all ports all the time. #or thisreason, if a network is connected using hubs, the chancesof a collision increases linearly with the number ofcomputers $assuming e%ual bandwidth use&. Hubs pose asecurity risk since all packets are "ooded to all ports all

the time. f a user has packet sni'ng software, they cane(tract data from the network and potentially decode itand use it. Hubs make it easy to )spy) on users on thesame *+ as you.

Networking


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-epeater + repeater is an electronic de!ice that

recei!es a signal and retransmits it at a

higher le!el andor higher power, or ontothe other side of an obstruction, so that thesignal can co!er longer distances withoutdegradation. Because repeaters work withthe actual physical signal, and do not

attempt to interpret the data beingtransmitted, they operate on the physicallayer, the /rst layer of the OS model.

Networking


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0odem 0odem $from modulator1demodulator& is a

de!ice that turns the digital 2s and 3s of a

personal computer into sounds that can betransmitted o!er the telephone lines of 4lain Old5elephone Systems $4O5S&, and once recei!edon the other side, con!erts those sounds backinto a form used by a USB, 6thernet, serial, or

network connection. 0odems are generallyclassi/ed by the amount of data they can sendin a gi!en time, normally measured in bits persecond, or )bps).

Networking


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7 $etwork nterface 7ard& + network interface card is a computer hardware

component designed to allow computers tocommunicate o!er a computer network. t is both anOS layer 2 $physical layer& and layer 8 $data link layer&de!ice, as it pro!ides physical access to a networkingmedium and pro!ides a low1le!el addressing systemthrough the use of 0+7 addresses. t allows users toconnect to each other either by using cables orwirelessly. 0ost motherboards today come e%uippedwith a network interface card in the form of a controller,with the hardware built into the board itself, eliminatingthe need for a standalone card.

Networking


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0edia 7on!erters 0edia con!erters are simple networking de!ices that make it

possible to connect two dissimilar media types such as twisted pairwith /ber optic cabling. 5hey were introduced to the industry

nearly two decades ago, and are important in interconnecting /beroptic cabling1based systems with e(isting copper1based, structuredcabling systems. 0edia con!erters support many di9erent datacommunication protocols including 6thernet, 5262, 5:6:, as wellas multiple cabling types such as coa(ial, twistedpair, multimode and single1mode /ber optics. ;hen e(panding thereach of a *ocal +rea etwork to span multiple locations, media

con!erters are useful in connecting multiple *+s to form one large)campus area network) that spans o!er a limited geographic area.+s local networks are primarily copper1based, media con!erterscan e(tend the reach of the *+ o!er single1mode /ber up to 2:3kilometers with 2


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Basic Switch Switches are often confused with bridges because they also operate

at the data link layer of the OS model. Similar to a hub, switchespro!ide a central connection between two or more computers on anetwork, but with some intelligence. 5hey pro!ide tra'c control forpackets= rather than forwarding data to all the connected ports, aswitch forwards data only to the port on which the destinationsystem is connected. 5hey use a database of 0+7 addresses todetermine where computers are located and !ery e'ciently sendpackets only where they need to go. 5he database is createddynamically as computers communicate on the network. 5he switchsimply watches the incoming packets and memori>es the 0+7

address and port a packet arri!es on. f a packet arri!es with adestination computer that the switch does not ha!e an address for inits 0+7 address table, it will "ood the packet out all connected ports.+ switch creates separate collision domains for each physicalconnection. + switch will only create separate broadcast domains ifseparate ?*+s $?irtual *ocal +rea etworks& are assigned todi9erent ports on the switch. Otherwise, a broadcast recei!ed on oneport will be "ooded out all ports e(cept the one it came in on.

Networking


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Bridge Bridges can be identi/ed by the fact that they operate at

the data link layer of the OS model. Bridges ha!e intelligenceand can )bridge) two of their ports together at !ery high

speed. 5hey use a database of 0+7 addresses to determinewhere computers are located and !ery e'ciently send framesonly where they need to go. 5he database is createddynamically as computers communicate on the network. +

bridge simply watches the incoming frame and memori>es the

0+7 address and port a frame arri!es on. t uses thisinformation to locate a computer if a packet comes in that

must be forwarded to it. f a frame arri!es at the bridge andthe bridge does not know where to send it, the bridge will

"ood the frame @ust like a hub does. Bridging is ofteninaccurately called switching.

Networking


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;ireless +ccess 4oint+ wireless access point $;+4 or +4& is a de!ice that allows wireless communication de!ices toconnect to a wireless network using ;i1#i, Bluetooth or related standards. 5he ;+4 usually connectsto a wired network, and can relay data between the wireless de!ices $such as computers or printers&and wired de!ices on the network.+ typical corporate use in!ol!es attaching se!eral ;+4s to a wired network and then pro!iding

wireless access to the o'ce *ocal +rea etwork. ;ithin the range of the ;+4s, the wireless end userhas a full network connection with the bene/t of mobility. n this instance, the ;+4 functions as agateway for clients to access the wired network.+ Hot Spot is a common public application of ;+4s, where wireless clients can connect to thenternet without regard for the particular networks to which they ha!e attached for the moment. 5heconcept has become common in large cities, where a combination of co9eehouses, libraries, as wellas pri!ately owned open access points, allow clients to stay more or less continuously connected tothe nternet, while mo!ing around. + collection of connected Hot Spots can be referred to as a lily1pad network.Home networks generally ha!e only one ;+4 to connect all the computers in a home. 0ost are

wireless routers, meaning con!erged de!ices that include a ;+4, router, and oftenan 6thernet switch in the same de!ice. 0any also con!erge a broadband modem. n places wheremost homes ha!e their own ;+4 within range of the neighborsA ;+4, itAs possible for technicallysa!!y people to turn o9 their encryption and set up a wireless community network, creating an intra1city communication network without the need of wired networks.

Networking


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Basic -outer -outers operate at the network layer of the OS model and

e'ciently route information between *ocal +rea etworks.Since routers operate in the third layer, the network layer,

they must understand layer : addressing... such as 5744.+ router will di!ide a broadcast domain by not forwardingbroadcasts on one connected network to anotherconnected network. -outers operate in two di9erentplanes the control plane, in which the router learns theoutgoing interface that is most appropriate for forwarding

speci/c packets to speci/c destinations, and theforwarding plane, which is responsible for the actual

process of sending a packet recei!ed on a logical interfaceto an outbound logical interface.

Networking


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Basic #irewall + /rewall is a part of a computer system or network that is designed to

block unauthori>ed access while permitting outward communication. tis also a de!ice or set of de!ices con/gured to permit, deny, encrypt,decrypt, or pro(y all computer tra'c between di9erent securitydomains based upon a set of rules and other criteria.

#irewalls can be implemented in both hardware and software, or acombination of both. #irewalls are fre%uently used to pre!entunauthori>ed nternet users from accessing pri!ate networks connectedto the nternet. +ll messages entering or lea!ing the *ocal +reaetwork pass through the /rewall, which e(amines each message andblocks those that do not meet the speci/ed security criteria. ;ithout

proper con/guration, a /rewall can often become worthless. Standardsecurity practices dictate a )default1deny) /rewall ruleset, in which theonly network connections which are allowed are the ones that ha!ebeen e(plicitly allowed.

Networking


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Basic DH74 $Dynamic Host 7on/guration4rotocol& ser!er

;hen a DH741con/gured client $be it a computer or any othernetwork1aware de!ice& connects to a network, the DH74 clientsends a broadcast %uery re%uesting necessary information

from a DH74 ser!er. 5he DH74 ser!er manages a pool of 4addresses and information about client con/gurationparameters such as the default gateway, the domain name,the DS $Domain ame System& ser!ers, other ser!ers such astime ser!ers, and so forth. Upon receipt of a !alid re%uest theser!er will assign the computer an 4 address, a lease $thelength of time for which the allocation is !alid&, and other 4

con/guration parameters, such as the subnet mask and thedefault gateway. 5he %uery is typically initiated immediatelyafter booting and must be completed before the client caninitiate 41based communication with other hosts.

Networking

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The Common Network Devices