Networks seminar report

8/9/2019 Networks seminar report

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Basics of Computer Networks

1 Introduction

A computer network or data network is a telecommunications network that allows

computers to exchange data. In computer networks, networked computing devices pass data to

each other along data connections. Data is transferred in the form of packets. The connections

(network links) between nodes are established using either cable media or wireless media. The

best known computer network is the Internet.

!etwork computer devices that originate, route and terminate the data are called network

nodes. !odes can include hosts such as personal computers, phones, servers as well as

networking hardware. Two such devices are said to be networked together when one device is

able to exchange information with the other device, whether or not the" have a direct connection

to each other.

Arguabl", the greatest advancement in technolog" and communication over the past #$

"ears has been the development and advancement of the computer network. %rom emailing a

friend to on line bill pa"ing to downloading data off the Internet to e commerce, networking has

made our world much smaller and changed the wa" we communicate forever.

Thus a network can be defined as,

net·work: &net wurk' – noun , a s"stem containing an" combination of computers,

computer terminals, printers, audio or visual displa" devices, or telephones interconnected b"

telecommunication e uipment or cables used to transmit or receive information.

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2 TYPES OF NETWORKS

*A! and +A! were the original categories of area networks, while the others have

graduall" emerged over man" "ears of technolog" evolution.

!ote that these network t"pes are a separate concept from network topologies such as

bus, ring and star.

LAN - Local Area Network

A LAN connects network devices over a relatively short distance. A networked

o ce !uilding" school" or home usually contains a single LAN" though sometimes

one !uilding will contain a few small LANs #perhaps one per room$" and occasionally

a LAN will span a group of near!y !uildings. %n &CP'%P networking" a LAN is often !ut

not always implemented as a single %P su!net.

In addition to operating in a limited space, *A!s are also t"picall" owned, controlled,

and managed b" a single person or organi ation. The" also tend to use certain connectivit"

technologies, primaril" -thernet and Token ing.

(AN - (ide Area NetworkAs the term implies, a +A! spans a large ph"sical distance. The Internet is the largest

+A!, spanning the -arth.

A +A! is a geographicall" dispersed collection of *A!s. A network device called a

router connects *A!s to a +A!. In I/ networking, the router maintains both a *A! address and

a +A! address.

A +A! differs from a *A! in several important wa"s. 0ost +A!s (like the Internet)

are not owned b" an" one organi ation but rather exist under collective or distributed ownership

and management. +A!s tend to use technolog" like AT0, %rame ela" and 1.#2 for

connectivit" over the longer distances.

etropo!itan "rea Network

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A network spanning a ph"sical area larger than a *A! but smaller than a +A!, such as a

cit". A 0A! is t"picall" owned and operated b" a single entit" such as a government bod" or

large corporation.

#irtua! pri$ate network ( #PN )

A $irtua! pri$ate network (#PN ) extends a private network across a public network,

such as the Internet. It enables a computer or +i %i enabled device to send and receive data

across shared or public networks as if it were directl" connected to the private network, while

benefiting from the functionalit", securit" and management policies of the private network. A

3/! is created b" establishing a virtual point to point connection through the use of dedicated

connections, virtual tunnelling protocols, or traffic encr"ptions.

A 3/! connection across the Internet is similar to a wide area network (+A!) link

between websites. %rom a user perspective, the extended network resources are accessed in the

same wa" as resources available within the private network.

3/!s allow emplo"ees to securel" access their compan"4s intranet while traveling

outside the office. 5imilarl", 3/!s securel" connect geographicall" separated offices of an

organi ation, creating one cohesive network. 3/! technolog" is also used b" individual Internet

users to secure their wireless transactions and to connect to prox" servers for the purpose of

protecting personal identit" and location.

Intranet

An intranet is a computer network that uses Internet /rotocol technolog" to share

information, operational s"stems, or computing services within an organi ation. This term is

used in contrast to extranet , a network between organi ations, and instead refers to a network

within an organi ation. 5ometimes, the term refers onl" to the organi ation4s internal website,

but ma" be a more extensive part of the organi ation4s information technolog" infrastructure,

and ma" be composed of multiple local area networks. The ob6ective is to organi e each

individual4s desktop with minimal cost, time and effort to be more productive, cost efficient,

timel", and competitive.

An intranet ma" host multiple private websites and constitute an important component

and focal point of internal communication and collaboration. An" of the well known Internet

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protocols ma" be found in an intranet, such as 7TT/ (web services), 50T/ (e mail), and %T/

(file transfer protocol). Internet technologies are often deplo"ed to provide modern interfaces to

legac" information s"stems hosting corporate data.

An intranet can be understood as a private analog of the Internet, or as a private

extension of the Internet confined to an organi ation. The first intranet websites and home pages

were published in 8998, and began to appear in non educational organi ations in 899:.

Intranets are sometimes contrasted to extranets. +hile intranets are generall" restricted to

emplo"ees of the organi ation, extranets ma" also be accessed b" customers, suppliers, or other

approved parties. -xtranets extend a private network onto the Internet with special provisions

for authentication, authori ation and accounting (AAA protocol).

In man" organi ations, intranets are protected from unauthori ed external access b"

means of a network gatewa" and firewall. %or smaller companies, intranets ma" be created

simpl" b" using private I/ address ranges. In these cases, the intranet can onl" be directl"

accessed from a computer in the local network; however, companies ma" provide access to off

site emplo"ees b" using a virtual private network, or b" other access methods, re uiring user

authentication and encr"ption.

E%tranet

An e%tranet is a computer network that allows controlled access from outside of an

organi ation4s intranet. -xtranets are used for specific use cases including business to business

( in that it provides access to needed

services for channel partners, without granting access to an organi ation4s entire network.

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& 'ENEFITS OF " NETWORK

The benefits of networking (either wired or wireless) in homes are

Fi!e ()arin* !etwork file sharing between computers gives "ou more flexibit" than using

flopp" drives or >ip drives. !ot onl" can "ou share photos, music files, and documents, "ou can

also use a home network to save copies of all of "our important data on a different computer.

Backups are one of the most critical "et overlooked tasks in home networking.

Printer + perip)era! ()arin* ?nce a home network is in place, it4s eas" to then set up all of

the computers to share a single printer. !o longer will "ou need to bounce from one s"stem or

another 6ust to print out an email message. ?ther computer peripherals can be shared similarl"

such as network scanners, +eb cams, and =D burners.

Internet connection sharing - )sing a home network" multiple family

mem!ers can access the %nternet simultaneously without having to pay an

%*P for multiple accounts. +ou will notice the %nternet connection slows downwhen several people share it" !ut !road!and %nternet can handle the e,tra

load with little trou!le. *haring dial-up %nternet connections works" too.

Painfully slow sometimes" you will still appreciate having shared dial-up on

those occasions you really need it.

Multi-player games - any popular home computer games support LAN

mode where friends and family can play together" if they have their

computers networked.

Internet telephone service - *o-called oice over %P # o%P$ services allow

you to make and receive phone calls through your home network across the

%nternet" saving you money.

Home entertainment - Newer home entertainment products such as digital video

recorders #/ 0s$ and video game consoles now support either wired or wireless

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home networking. 1aving these products integrated into your network ena!les

online %nternet gaming" video sharing and other advanced features.

, P-YSI."/ E0I"

Twi(ted pair ca !e

Twi(ted pair cabling is a t"pe of wiring in which two conductors of a single circuit aretwisted together for the purposes of canceling out electromagnetic interference (-0I) from

external sources; for instance, electromagnetic radiation from unshielded twisted pair (@T/)

cables, and crosstalk between neighboring pairs. It was invented b" Alexander raham


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dimensions of the cable are controlled to give a precise, constant conductor spacing, which is

needed for it to function efficientl" as a radio fre uenc" transmission line.

Fi* ,32: .oa%ia! .a !e

Fi er optic ca !e

An optica! 4i er ca !e is a cable containing one or more optical fibers that are used tocarr" light. The optical fiber elements are t"picall" individuall" coated with plastic la"ers and

contained in a protective tube suitable for the environment where the cable will be deplo"ed.

Different t"pes of cable are used for different applications, for example long distance

telecommunication, or providing a high speed data connection between different parts of a

building.

Fi* ,3&: Fi er optic ca !e

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5 WIRE/ESS E0I"

icrowa$e (6(tem


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@ses antennae resembling telephone towers to pick up radio signals within a specific

area (cell).

In4rared tec)no!o*6

Transmits data as infrared light waves from one device to another, providing

wireless links between /=s and peripherals

Fi* 531: In4rared Tran(mi((ion

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7 .ate*ori8ation o4 Network(

!etworks are usuall" classified into three properties.

H.8 .Topolog"

H.#. /rotocol

H.E. Architecture

7313 Topo!o*6

Network topo!o*6 is the arrangement of the various elements of a computer network.

-ssentiall", it is the topological structure of a network and ma" be depicted ph"sicall" or logicall". Physical topology is the placement of the various components of a network, including

device location and cable installation, while logical topology illustrates how data flows within a

network, regardless of its ph"sical design. Distances between nodes, ph"sical interconnections,

transmission rates, or signal t"pes ma" differ between two networks, "et their topologies ma" be

identical.

An example is a local area network (*A!) An" given node in the *A! has one or more

ph"sical links to other devices in the network; graphicall" mapping these links results in a

geometric shape that can be used to describe the ph"sical topolog" of the network. =onversel",

mapping the data flow between the components determines the logical topolog" of the network.

732 Protoco!

ules of !etwork /rotocol include guidelines that regulate the following characteristics of a

network access method, allowed ph"sical topologies, t"pes of cabling, and speed of datatransfer.

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&ypes of Network Protocols

The most common network protocols are

2. 3thernet

4. Local &alk

5. &oken 0ing

6. 7//%

8. A&

The followings are some commonl" used network s"mbols to draw different kinds of network protocols.

Fi* 731: /a6out o4 Network(

Et)ernet

The -thernet protocol is b" far the most widel" used one. -thernet uses an access

method called =50A =D (=arrier 5ense 0ultiple Access =ollision Detection). This is a s"stem

where each computer listens to the cable before sending an"thing through the network. If the

network is clear, the computer will transmit. If some other nodes have alread" transmitted on the

cable, the computer will wait and tr" again when the line is clear. 5ometimes, two computers

attempt to transmit at the same instant. A collision occurs when this happens. -ach computer

then backs off and waits a random amount of time before attempting to retransmit. +ith this

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access method, it is normal to have collisions. 7owever, the dela" caused b" collisions and

retransmitting is ver" small and does not normall" effect the speed of transmission on the

network.

The -thernet protocol allows for linear bus, star, or tree topologies. Data can be

transmitted over wireless access points, twisted pair, coaxial, or fiber optic cable at a speed of 8$

0bps up to 8$$$ 0bps.

Fa(t Et)ernet

To allow for an increased speed of transmission, the -thernet protocol has developed a

new standard that supports 8$$ 0bps. This is commonl" called %ast -thernet. %ast -thernet

re uires the application of different, more expensive network concentrators hubs and network

interface cards. In addition, categor" 2 twisted pair or fiber optic cable is necessar". %ast

-thernet is becoming common in schools that have been recentl" wired.

/oca! Ta!k

*ocal Talk is a network protocol that was developed b" Apple =omputer, Inc. for

0acintosh computers. The method used b" *ocal Talk is called =50A =A (=arrier 5ense

0ultiple Access with =ollision Avoidance). It is similar to =50A =D except that a computer

signals its intent to transmit before it actuall" does so. *ocal Talk adapters and special twisted

pair cable can be used to connect a series of computers through the serial port. The 0acintosh

operating s"stem allows the establishment of a peer to peer network without the need for

additional software. +ith the addition of the server version of Apple5hare software, a

client server network can be established.

The *ocal Talk protocol allows for linear bus, star, or tree topologies using twisted pair

cable. A primar" disadvantage of *ocal Talk is low speed. Its speed of transmission is onl" #E$

Jbps.

Token Rin*

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The Token ing protocol was developed b" I


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The most latest development in the -thernet standard is a protocol that has a

transmission speed of 8 bps. igabit -thernet is primaril" used for backbones on a network at

this time. In the future, it will probabl" also be used for workstation and server connections. It

can be used with both fiber optic cabling and copper. The 8$$$


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Fi* 732: OSI ode!

NETWORKIN9 -"R0W"RE "N0 SOFTW"RE

31 Et)ernet )u

An Et)ernet )u , acti$e )u , network )u , repeater )u , mu!tiport repeater or )u

is a device for connecting multiple -thernet devices together and making them act as a single

network segment. It has multiple input output (I ?) ports, in which a signal introduced at the

input of an" port appears at the output of ever" port except the original incoming. A hub works

at the ph"sical la"er (la"er 8) of the ?5I model. epeater hubs also participate in collision

detection, forwarding a 6am signal to all ports if it detects a collision. In addition to standard

B/B= (K L:2K) ports, some hubs ma" also come with a

(A@I) connector to allow connection to legac" 8$


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Fi* 31: Et)ernet -u

32 Repeater(

A common problem in the networking world is that of weakening electrical signals.

-lectrical signals traveling through wires (such as copper wires used in most networks), weaken

due to the wire4s electrical resistance. This effect limits the lengths of the cable that can be

used. A repeater will overcome this limit, when there is a need to connect two computers at a

larger distance.

A repeater is connected to two cable segments. An" electrical signal reaching the

repeater from one segment, will be amplified and retransmitted to the other segment.

Fi* 32: Repeater

3& Router(

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A router is a networking device, commonl" speciali ed hardware, that forwards data

packets between computer networks. This creates an overla" internetwork, as a router is

connected to two or more data lines from different networks. +hen a data packet comes in one

of the lines, the router reads the address information in the packet to determine its ultimate

destination. Then, using information in its routing table or routing polic", it directs the packet tothe next network on its 6ourne". outers perform the Ktraffic directingK functions on the Internet.

A data packet is t"picall" forwarded from one router to another through the networks that

constitute the internetwork until it reaches its destination node.

The most familiar t"pe of routers are home and small office routers that simpl" pass data,

such as web pages, email, I0, and videos between the home computers and the Internet. An

example of a router would be the owner4s cable or D5* router, which connects to the Internet

through an I5/. 0ore sophisticated routers, such as enterprise routers, connect large business or

I5/ networks up to the powerful core routers that forward data at high speed along the optical

fiber lines of the Internet backbone. Though routers are t"picall" dedicated hardware devices,

use of software based routers has grown increasingl" common.

Fi* 3&: #i(ua!i8ation o4 Router

3, odem(

5hort for mo dulator- dem odulator. A modem is a device or program that enables a

computer to transmit data over, for example, telephone or cable lines. =omputer information is

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stored digitall", whereas information transmitted over telephone lines is transmitted in the form

of analog waves. A modem converts between these two forms.

%ortunatel", there is one standard interface for connecting external modems to computers

called RS-232. =onse uentl", an" external modem can be attached to an" computer that has an

5 #E# port, which almost all personal computers have. There are also modems that come as an

expansion board that "ou can insert into a vacant expansion slot. These are sometimes called

onboard or internal modems .

Fi* 3,: #i(ua!i8ation o4 odem

+hile the modem interfaces are standardi ed, a number of different protocols for

formatting data to be transmitted over telephone lines exist. 5ome, like ==ITT 3.E:, are official

standards, while others have been developed b" private companies. 0ost modems have built in

support for the more common protocols at slow data transmission speeds at least, most

modems can communicate with each other. At high transmission speeds, however, the protocols

are less standardi ed.

35 Firewa!!

7aving a good understanding of the capabilities offered b" the different t"pes of

firewalls will help "ou in placing the appropriate t"pe of firewall to best meet "our securit"

needs.

@nderstanding /acket %iltering %irewalls

/acket filtering firewalls validate packets based on protocol, source and or destination I/

addresses, source and or destination port numbers, time range, Differentiate 5ervices =ode /oint

(D5=/), t"pe of service (To5), and various other parameters within the I/ header. /acket

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filtering is generall" accomplished using Access =ontrol *ists (A=*) on routers or switches and

are normall" ver" fast, especiall" when performed in an Application 5pecific Integrated =ircuit

(A5I=). As traffic enters or exits an interface, A=*s are used to match selected criteria and

either permit or den" individual packets.

Fi* 35: #i(ua!i8ation o4 Firewa!!

Advantages

The primar" advantage of packet filtering firewalls is that the" are located in 6ust about ever"

device on the network. outers, switches, wireless access points, 3irtual /rivate !etwork (3/!)

concentrators, and so on ma" all have the capabilit" of being a packet filtering firewall.

outers from the ver" smallest home office to the largest service provider devices inherentl"

have the capabilit" to control the flow of packets through the use of A=*s.

5witches ma" use outed Access =ontrol *ists ( A=*s), which provide the capabilit" to

control traffic flow on a KroutedK (*a"er E) interface; /ort Access =ontrol *ists (/A=*), which

are assigned to a KswitchedK (*a"er #) interface; and 3*A! Access =ontrol *ists (3A=*s),

which have the capabilit" to control KswitchedK and or KroutedK packets on a 3*A!.

?ther networking devices ma" also have the power to enforce traffic flow through the use of

A=*s. =onsult the appropriate device documentation for details.

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/acket filtering firewalls are most likel" a part of "our existing network. These devices ma" not

be the most feature rich, but when "ou need to uickl" implement a securit" polic" to mitigate

an attack, protect against infected devices, and so on, this ma" be the uickest solution to

deplo".

Caveats

The challenge with packet filtering firewalls is that A=*s are static, and packet filtering has no

visibilit" into the data portion of the I/ packet.


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In computing, the Po(t O44ice Protoco! (POP ) is an application la"er Internet standard

protocol used b" local e mail clients to retrieve e mail from a remote server over a T=/ I/

connection. /?/ has been developed through several versions, with version E ( POP& ) being the

current standard.

3irtuall" all modern e mail clients and servers support /?/E, and it along with I0A/

(Internet 0essage Access /rotocol) are the two most prevalent Internet standard protocols for e

mail retrieval, with man" webmail service providers such as mail, ?utlook.com and MahooN

0ail also providing support for either I0A/ or /?/E to allow mail to be downloaded.

;?2311 @ protoco!:

IEEE ;?2311 is a set of media access control (0A=) and ph"sical la"er (/7M)specifications for implementing wireless local area network (+*A!) computer communication

in the #.:, E.H, 2 and H$ 7 fre uenc" bands. The" are created and maintained b" the I---

*A! 0A! 5tandards =ommittee (I--- B$#). The base version of the standard was released in

899 and has had subse uent amendments. The standard and amendments provide the basis for

wireless network products using the +i %i brand. +hile each amendment is officiall" revoked

when it is incorporated in the latest version of the standard, the corporate world tends to market

to the revisions because the" concisel" denote capabilities of their products.

Re4erence(

en.wikipedia.org

www.webopedia.com

www.networkworld.com

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Networks seminar report

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