midterm 3introduction to computer networking

7/25/2019 Midterm 3introduction to Computer Networking

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COMPUTER NETWORKS AND CONCEPTS

MR. REGIE B. FABRO

Instructor


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Introduction to computer networking

Objective:

To be acquainted with:

The definitions of networking

Network topology

Network peripherals, hardware and software


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efinitions

!"! Network efinition

# network can be defined as two or more

computers connected together in such a way

that they can share resources"

The purpose of a network is to share

resources"


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efinitions $cont""%

# resource may be:

# file

# folder# printer

# disk drive

Or just about anything else that e&ists ona computer"


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efinitions $cont""%

# network is simply a collection of computers or otherhardware devices that are connected together, eitherphysically or logically, using special hardware andsoftware, to allow them to e&change information and

cooperate" Networking is the term that describes theprocesses involved in designing, implementing,upgrading, managing and otherwise working withnetworks and network technologies"


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#dvantages of networking

'onnectivity and 'ommunicationata (haring)ardware (haring

Internet #ccess Internet #ccess (haringata (ecurity and *anagement

+erformance nhancement and -alancingntertainment


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The Disadvantages (Costs) of Networking

Network )ardware, (oftware and (etup 'osts)ardware and (oftware *anagement and

#dministration 'osts

.ndesirable (haring Illegal or .ndesirable -ehavior

ata (ecurity 'oncerns


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Fundamental Network Classifications

Local Area Networks (LANs): # local area network (LAN)is a computer network covering a small geographic area, like a

home, office, or group of buildings

Wide Area Networks (WANs): Wide Area Network$WAN% is a computer network that covers a broad area $i"e", any network

whose communications links cross metropolitan, regional, or national boundaries%" Or, less

formally, a network that uses routers and public communications links The largest and most well/known e&ample of a 0#N is the Internet" 0#Ns are used to connect 1#Ns and other types of networks together, so that users and

computers in one location can communicate with users and computers in other locations

etro!olitan Area Network (AN):o # metropolitan area network $*#N% is a network that interconnects users with computer

resources in a geographic area or region larger than that covered by even a large local areanetwork $1#N% but smaller than the area covered by a wide area network $0#N%" The term isapplied to the interconnection of networks in a city into a single larger network $which maythen also offer efficient connection to a wide area network%" It is also used to mean theinterconnection of several local area networks by bridging them with backbone lines" Thelatter usage is also sometimes referred to as a campus network"


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Fundamental Network Classifications (cont)

The 1ocal Network $1#N%

Client

ClientClient

Client Client

Client


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0ide #rea Network


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*etropolitan #rea Network $*#N%


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Intranet and Internet (pecifications

Intranet:#n intranet is a private network that is contained withinan enterprise" It may consist of many interlinked local areanetworks and also use leased lines in the wide area network"

#n intranet uses T'+2I+, )TT+, and other Internet protocols andin general looks like a private version of the Internet" 0ith

tunneling, companies can send private messages through thepublic network, using the public network with specialencryption2decryption and other security safeguards to connect

one part of their intranet to another" Internet:is a worldwide system of computer networks / a

network of networks in which users at any one computer can, ifthey have permission, get information from any other computer$and sometimes talk directly to users at other computers%"
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'lient and (erver computer role in

networking

"ervercomputer is a core component of the network,providing a link to the resources necessary to performany task"

# server computer provides a link to the resources

necessary to perform any task" The link it provides could be to a resource e&isting on

the server itself or a resource on a client computer" Clientcomputers normally request and receive

information over the network client. Client computersalsodepends primarily on the central server forprocessing activities


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+eer/to peer network

# peer/to/peer network is a network where thecomputers act as both workstations and servers"

great for small, simple, and ine&pensive networks" In a strict peer/to/peer networking setup, every

computer is an equal, apeerin the network" ach machine can have resources that are shared

with any other machine" There is no assigned role for any particular device,

and each of the devices usually runs similar software"#ny device can and will send requests to any other"


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+eer/to peer network $cont""%


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Client#"erver Networking

In this design, a small number of

computers are designated as centrali3ed

serversand given the task of providing

services to a larger number of user

machines called clients


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Client#"erver Networking (cont$$)


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Network topology

# topology is a way of 4laying out5 the

network" Topologies can be either

physical or logical"

Physical topologies describe how the

cables are run"

Logical topologies describe how the

network messages travel


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Network topology $cont"%

-us $can be both logical and physical%

(tar $physical only%

6ing $can be both logical and physical%*esh $can be both logical and physical%


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-us# bus is the simplest physical topology" It consists of a

single cable that runs to every workstation This topology uses the least amount of cabling, but

also covers the shortest amount of distance" ach computer shares the same data and address

path" 0ith a logical bus topology, messages passthrough the trunk, and each workstation checks to see

if the message is addressed to itself" If the address ofthe message matches the workstation7s address, thenetwork adapter copies the message to the card7s on/board memory"


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it is difficult to add a workstation

have to completely reroute the cable and

possibly run two additional lengths of it"

if any one of the cables breaks, the

entire network is disrupted" Therefore, it

is very e&pensive to maintain"


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-us topology


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(tar Topology# physical star topology branches each network device

off a central device called a hub, making it very easy toadd a new workstation"

#lso, if any workstation goes down it does not affectthe entire network" $-ut, as you might e&pect, if thecentral device goes down, the entire network goesdown"%

(ome types of thernet and #6'Net use a physicalstar topology" 8igure 9" gives an e&ample of theorgani3ation of the star network"


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(tar topologies are easy to install" #cable is run from each workstation to thehub" The hub is placed in a central

location in the office"(tar topologies are more e&pensive to

install than bus networks, because there

are several more cables that need to beinstalled, plus the cost of the hubs thatare needed"


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(tar Topology


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%ing

ach computer connects to two other

computers, joining them in a circle creating a

unidirectional path where messages moveworkstation to workstation"

ach entity participating in the ring reads a

message, then regenerates it and hands it to

its neighbor on a different network cable"


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The ring makes it difficult to add newcomputers"

.nlike a star topology network, the ring

topology network will go down if oneentity is removed from the ring"

+hysical ring topology systems don7t

e&ist much anymore, mainly because thehardware involved was fairly e&pensiveand the fault tolerance was very low"


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6ing Topology


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esh The mesh topology is the simplest logical topology in terms of

data flow, but it is the most comple& in terms of physical design" In this physical topology, each device is connected to every other

device

This topology is rarely found in 1#Ns, mainly because of thecomple&ity of the cabling" If there arex computers, there will be $x ; $x!%% < = cables in the

network" 8or e&ample, if you have five computers in a meshnetwork, it will use > ; $> ? !% < =, which equals !@ cables" Thiscomple&ity is compounded when you add another workstation"

8or e&ample, your five/computer, !@/cable network will jump to!> cables just by adding one more computer" Imagine how theperson doing the cabling would feel if you told them you had tocable >@ computers in a mesh networkAthey7d have to come upwith >@ ; $>@ ? !% < = B !==> cablesC


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-ecause of its design, the physical mesh topology is verye&pensive to install and maintain"

'ables must be run from each device to every other device" Theadvantage you gain from it is its high fault tolerance"

0ith a logical mesh topology, however, there will always be a way

of getting the data from source to destination" It may not be able to take the direct route, but it can take an

alternate, indirect route" It is for this reason that the meshtopology is still found in 0#Ns to connect multiple sites across0#N links" It uses devices called routers to search multipleroutes through the mesh and determine the best path"

)owever, the mesh topology does become inefficient with five ormore entities"


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*esh Topology


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#dvantages and isadvantages of Network Topologies

To!olog& Advantages Disadvantages

-us 'heap" asy to install" ifficult to reconfigure"-reak in bus disables

entire network"

(tar 'heap" asy to install"asy to reconfigure"

8ault tolerant"

*ore e&pensive than bus"

6ingfficient" asy to install" 6econfiguration difficult"

Dery e&pensive"

*esh (implest" *ost fault tolerant" 6econfiguration e&tremely difficult"&tremely e&pensive"

Dery comple&"


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)ardware, (oftware and Networks

+eripherals $device%

Network Interface 'ard $NI'%

6epeater

)ub-ridge

6outers

(witch


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)ardware, (oftware and Networks +eripherals $cont"%

Network 'nterface Card (N'C) NI' provides the physical interface between computer and

cabling" It prepares data, sends data, and controls the flow of data" It can

also receive and translate data into bytes for the '+. to

understand" The following factors should be taken into consideration whenchoosing a NI':

!" / +reparing data

=" / (ending and controlling data

E" / 'onfiguration

F" / rivers>" / 'ompatibility

G" / +erformance


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)ardware, (oftware and Networks +eripherals $cont"%re!aring Data

In the computer, data moves along buses in parallel,as on a four/lane interstate highway" -ut on a networkcable, data travels in a single stream, as on a one lanehighway" This difference can cause problems

transmitting and receiving data, because the pathstraveled are not the same" It is the NI'7s job to translate the data from the

computer into signals that can flow easily along thecable"

It does this by translating digital signals into electricalsignals $and in the case of fiber/optic NI's, to opticalsignals%"


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)ardware, (oftware and Networks +eripherals $cont"%"ending and Controlling Data

8or two computers to send and receive data, the cards mustagree on several things" These include the following:

/ The ma&imum si3e of the data frames

/ The amount of data sent before givingconfirmation

/ The time needed between transmissions/ The amount of time needed to wait before sending

confirmation

/ The amount of data a card can hold

/ The speed at which data transmits In order to successfully send data on the network, you need to

make sure the network cards are of the same type and they areconnected to the same piece of cable"


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)ardware, (oftware and Networks +eripherals $cont"%Configuration

The NI'7s configuration includes things like a

manufacturer7s hardware address, I6H

address, -ase I2O port address, and base

memory address" (ome may also use *#channels to offer better performance"

ach card must have a unique hardware

address" If two cards have the same hardware

addresses, neither one of them will be able tocommunicate"


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)ardware, (oftware and Networks +eripherals $cont"%Drivers

8or the computer to use the network

interface card, it is very important to

install the proper device drivers"

These drivers communicate directly with

the network redirector and adapter" They

operate in the *edia #ccess 'ontrol

sublayer of the ata 1ink layer of theO(I model"


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)ardware, (oftware and Networks +eripherals $cont"%Com!atiilit&

0hen choosing a NI', use one that fitsthe bus type of your +'" If you havemore than one type of bus in your +'

$for e&ample, a combination I(#2+'I%,use an NI' that fits into the fastest type$the +'I, in this case%"

This is especially important in servers,as the NI' can very quickly become abottleneck if this guideline isn7t followed"


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)ardware, (oftware and Networks +eripherals $cont"%erformance

The most important goal of the networkadapter card is to optimi3e networkperformance and minimi3e the amount

of time needed to transfer data packetsacross the network"

There are several ways of doing this,including assigning a *# channel, useof a shared memory adapter, anddeciding to allow bus mastering"


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%e!eaters

6epeaters are very simple devices" They allow a cabling systemto e&tend beyond its ma&imum allowed length by amplifying thenetwork voltages so they travel farther"

6epeaters are nothing more than amplifiers and, as such, arevery ine&pensive"

6epeaters can only be used to regenerate signals betweensimilar network segments" 8or e&ample, we can e&tend an thernet !@-ase= network to F@@

meters with a repeater" -ut can7t connect an thernet and Token6ing network together with one"

The main disadvantage to repeaters is that they just amplify

signals" These signals not only include the network signals, butany noise on the wire as well" ventually, if you use enough repeaters, you could possibly

drown out the signal with the amplified noise" 8or this reason,repeaters are used only as a temporary fi&"


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%e!eaters


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*us

)ubs are devices used to link several computerstogether"

They repeat any signal that comes in on one port andcopy it to the other ports $a process that is also calledbroadcasting%"

There are two types of hubs: active and passive" Passive hubs simply connect all ports together

electrically and are usually not powered"Active hubs use electronics to amplify and clean up

the signal before it is broadcast to the other ports" In the category of active hubs, there is also a class

called 4intelligent5 hubs, which are hubs that can beremotely managed on the network"


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*us


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+ridges They join similar topologies and are used to divide network

segments" 8or e&ample, with =@@ people on one thernet segment, the

performance will be mediocre, because of the design of thernetand the number of workstations that are fighting to transmit" If youdivide the segment into two segments of !@@ workstations each,the traffic will be much lower on either side and performance willincrease"

If it is aware of the destination address, it is able to forwardpackets otherwise a bridge will forward the packets to allsegments" They are more intelligent than repeaters but areunable to move data across multiple networks simultaneously"

.nlike repeaters, bridges can filter out noise" The main disadvantage to bridges is that they can7t connect

dissimilar network types or perform intelligent path selection" 8orthat function, you would need a router"


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+ridges


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%outers 6outers are highly intelligent devices that connect multiple

network types and determine the best path for sending data" The advantage of using a router over a bridge is that routers can

determine the best path that data can take to get to itsdestination"

1ike bridges, they can segment large networks and can filter outnoise" )owever, they are slower than bridges because they are more

intelligent devices as such, they analy3e every packet, causingpacket/forwarding delays" -ecause of this intelligence, they arealso more e&pensive"

6outers are normally used to connect one 1#N to another" Typically, when a 0#N is set up, there will be at least two routersused"


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%outers


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"witch # network switchis a computer networking device that connects network

segments" 1ow/end network switches appear nearly identical to network hubs, but a switch

contains more JintelligenceJ $and a slightly higher price tag% than a network hub" Network switches are capable of inspecting data packets as they are received,

determining the source and destination device of that packet, and forwarding it

appropriately" -y delivering each message only to the connected device it was intended for, a

network switch conserves network bandwidth and offers generally betterperformance than a hub"

# vital differencebetween a huand a switchis that all the nodes connected toa hub share the bandwidth among themselves, while a device connected to aswitch port has the full andwidthall to itself"

8or e&ample, if !@ nodes are communicating using a hub on a !@/*bps network,then each node may only get a portion of the !@ *bps if other nodes on the hubwant to communicate as well" "

-ut with a switch, each node could possibly communicate at the full !@ *bps"

) d ( ft d N t k + i h l $ t %


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"witch


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1#-!

'onnect = buildings E storey high with a distance of>@@m between each building"

ach floor is occupied by the 8inance epartment,#dministration epartment and 'omputingepartment"

Kour report should have the following items" #nythinge&tra is encouraged"

a" Introduction

b" Network iagrams

c" evices that will be used" Kou are required to use *( Disio to draw the Network

iagrams"

midterm 3introduction to computer networking

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