computer networks prince dudhatra 9724949948

8/7/2019 Computer Networks Prince Dudhatra 9724949948

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Computer Networks

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What do you mean by network ?

Network means interconnections of two or more systems. The minimum number of

system required to make a network is two.Computer systems connected in a networkcan exchange information betweenthemselves.




Computer networks are of three types

Local Area Network ( LAN)

Metropolitan Area Network ( MAN)

Wide Area Network ( WAN)




Local Area Network ( LAN)

Networks that connect computers lying within asmall distance from each other such are calledLAN.

Local area networks normally use coaxial cablesto connect the computers together.LAN is used in building, rooms etc.Two or more computers connected to each other

can share data and their peripherals such asprinters, modems etc.




Local Area Network (cont.)

Applications performed by a LAN are asfollows

1) File transfer and access2) Accessing the internet3) Providing Management Information Systems




M etropolitan Area Network ( M AN)

A metropolitan area network uses thedistributed queue dual bus. The MAN is largerthan a LAN.

Metropolitan Area Network is used betweencities




Wide Area Network (WAN)

A wide area network connects computerswhich are very remotely placed.

It may connect across the countries orcontinents or the entire globe.

Wide Area Networks are also referred to asLong Haul Networks (LHNs).




R outing

When data is to be transmitted between tworemote machines using intermediatemachines is called Routing.Intermediate machines are as follows :-

1) Gateways or routers

2) Repeaters3) Bridges




G ateways or R outers

Gateway is one of several types of communication servers. The function of agateway is to allow two or more dissimilarnetworks to communicate as a single logicalentity. The two machines that have to transferdata between themselves may have different

operating systems (OS) or their transportprotocols may be different. It is then the job of the gateway to connect such machines.




R epeaters

A repeater receives the incoming signal,repeats it or amplifies it and retransmits thetransformed signal. After certain distances thesignal experiences a loss of power hence arepeater is required to boost the power of thesignal. By using repeaters the network can be

extended but on only finite extension ispossible due to physical constraints such asnoise.




B ridges

A bridge is a device that is used to connect twonetworks so that they are able to perform as one.A bridge can also be used to connect two

networks that use the same technology, such asthe Ethernet network and then Token Ringnetwork.One of the main functions of the bridge is topartition one large network into two networkswhich subsequently increases the performance of the network.




R outing Techniques

C omputer network may use following routingtechniques :-

1)C

ircuit Switching

2) Packet Switching

3) Message Switching




Cir cu it Sw itch ing

Circuit switching is defined as a mechanism applied intelecommunications whereby the user is allocated the fulluse of the communication channel for the duration of the call.That is if two parties wish to communicate, the calling party

has to first dial the numbers of the called party. Once thosenumbers are dialed, the originating exchange will find a pathto the terminating exchange, which will in turn find the calledparty.

After the circuit or channel has been set up, thencommunication will take place, then once they are throughthe channel will be cleared. This mechanism is referred to asbeing connection-oriented.




Adva nt a ges of Cir cu it Sw itch ing

1. Once the circuit has been set up, communication isfast and without error.

2. It is highly reliable.




D is adva nt a ges of Cir cu it Sw itch ing

1. Involves a lot of overhead, during channel set up.

2. Waists a lot of bandwidth, especial in speechwhereby a user is sometimes listening, and nottalking.

3. C hannel set up may take longer.




P a cket Sw itch ing

P acket switching entails packaging data in speciallyformatted units (called packets ) that are typically routedfrom source to destination using network switches androuters.

Each packet contains address information that identifies thesending computer and intended recipient.

Using these addresses, network switches and routersdetermine how best to transfer the packet between hubs onthe path to its destination.




Adva nt a ges of P a cket Sw itch ing

1. At the time of connection no need to worry aboutrouting.

2 Ability of route data units over any route. so morereliable.




D is adva nt a ges of P a cket Sw itch ing

1. Less hard drive space needed but more actualmemory needed.

2. More processing power required due to complex

routing protocols. (Like recognizing when a packethas been lost).




M ess a ge Sw itch ing

In telecommunications, mess a ge sw itch ing wasthe precursor of packet switching, where messages

were routed in their entity, one hub at a time.

It was first introduced by Leonard Kleinrock in 1961.

Message switching systems are now a days mostlyimplemented over packet-switched or circuit-switched data networks.




Adva nt a ges of M ess a ge Sw itch ing

1. The message are stored and relayed from secondarystorage (disk).

2. Mechanism a node receives a message stores ituntil the appropriate route is free, then sends italong.

3. Message switching sends data units that can be of any length.




D is adva nt a ges of M ess a ge Sw itch ing

1. It's not suitable for real time applications such asdata communication, video or audio.




NETWORK TOPO LOGY

Network topologies can be physical or logical.

P hysical topology means the physical design of a network including the devices, location andcable installation.

Logical topology refers to the fact that how dataactually transfers in a network as opposed to itsdesign.




TYPES OF TOPO LOGI ES

1. Star Topology2. Ring Topology3. Bus Topology4. Mesh Topology5. Tree Topology6. Hybrid Topology




STAR TOPO LOGY

Part of LAN (Local AreaNetwork)

Used in home, office andbuilding

All devices connect to a centraldevice, called Hub.

C onnected with hub with theUTP(Unshielded Twisted Pair)




ADVANTAG ES OF STAR TOPO LOGY

Easy to install & wire.

Security can be implemented in the hub/ switch.

Easy to detect the fault and to remove parts.

No disruptions to the network then connecting orremoving devices.




DISADVANTAG ES OF STAR TOPO LOGY

Requires more cable length than a linear or bustopology.

If the hub or connecter fails, nodes attached aredisabled.

More expensive than linear bus topologies becauseof the cost concentrators.

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RI NG TOPO LOGY

C able forms closed ring orloop, with all computers &devices arranged along ring.

Data travels from device todevice around entire ring, in onedirection.

Primarily is used for LANs, butalso is used in WANs (Wide AreaNetworks).




ADVANTAG ES OF RI NG TOPO LOGY

Growth of system has minimal impact onperformance.All stations have equal access.The network doesn t fail even when a link betweentwo nodes is broken.Data is quickly transferred without a bottle neck .

The transmission of data is relatively simple aspackets travel in one direction only.




DISADVANTAG ES OF RI NG TOPO LOGY

Most expensive topology.

Failure of one computer may impact others.

It is difficult to troubleshoot the ring.

Data packets must pass through every computerbetween the sender & recipient therefore, thismakes it slower.




BU S TOPO LOGY

It is also known as multipointtopology.

All computers & devicesconnected to central cable orhub.

C onsists of a main run of cable with a terminator eachend.

Popular on LANs becausethey are inexpensive & easy toinstall.




ADVANTAG ES OF BU S TOPO LOGY

Easy to connect a computer or peripheral to a linearbus.

Requires less cable length than a star topology.




DISADVANTAG ES OF BU S TOPO LOGY

Entire network shuts down if there is a break in themain cable.Terminators are required at both ends of thebackbone cables.Difficult to identify the problem if the entirenetwork shuts down.

Not meant to be used as a stand-alone solution in alarge building.




M ESH TOPOLOGY

It requires that every terminal shouldbe attached to each other.

All the computers must haveadequate number of interfaces for theconnection to be made.

Because of this requirement theinstallation is somewhat difficult.

The length of cable required is alsoquiet high as compared with othertopologies.




ADVANTAG ES OF M ESH TOPOLOGY

System provides increased reliability as well as easeof troubleshooting.

Data transfer is faster.

Addition and deletion of nodes easy.

Easy fault identification and isolation.




DISADVANTAG ES OF M ESH TOPOLOGY

System is expensive to install because it uses a lot of cabling.

Difficult to installation & configuration.

More input & output nodes.




TR EE TOPOLOGY

Server




TR EE TOPOLOGY

A tree topology combines characteristics of linearbus and star topologies.Only the devices can connect directly with the treebus.Each hub functions as a root of a tree of the networkdevices.

This bus/star/hybrid combination supports futureexpandability of the computer networks, muchbetter than a bus or star.




ADVANTAG ES OF TR EE TOPOLOGY

Point-to-point writing for individual segments.

The network dosen t fail even when a link betweentwo nodes is broken.

Supported by several hardware & software venders.




DISADVANTAG ES OF TR EE TOPOLOGY

Overall length of each segment is limited by thetype of cabling used.

If the backbone line breaks, the entire segmentgoes down.

More difficult to configure and wire than othertopologies.




HYBRI D TOPO LOGY

A combination of any two or more networktopologies.Two star network are connected together exhibithybrid network topologies.For example :- If a department uses a bus network,second department uses the ring network, thirddepartment uses the mesh network and fourthdepartment uses the star network. All the networksof different types can be connected together througha central hub.




Transmission Technology

There are two types of transmissiontechnology :-

1) Broadcast Networks

2) P oint to P oint Networks




B roadcast Networks

Single communication channel

P acket of data contains address of destination machine

Similar to railway announcementsystem




P o int to P o int Netwo r ks

Machines are connected pointto point

Data is routed from sourcemachine to target machine




INTER NETWORK S AND THE INTER NET

A collection of different networkconnected together

It is very large and available

world wide




Node 3 Node 1 Node 2

Router

WANRouter Router

Node 6 Node 5 Node 4

LAN

LAN

Fig : Internet work




INTERNETWORKS A ND THEINTERNET (cont.)

Accessing the Internet- You must have an account- You require a communicationsoftware




A set of rules according to which thecommunicating computers communicate.

The most common protocol used in networking isthe T C P

Protocols




File Transfer Protocol

The fundamental requirement is a commonprotocol.

The file transfer protocol gives the user anaccess to a remote machine file system.

The FTP is also an Internet tool.




ELECTRONIC MAIL




Need for Electronic M ail

For fast and efficient method to exchangemessages and other data.

It allows a very easy merging of a particularmessage.




Type of E-mail services

There are mainly 3 types of e-mail services.

1) POP Mail

2) Web-based E-mail

3) Mail Forwarding Services




POP M ail




Advantages of POP M ail

Work offline, compose or read messages.

Mail program used by our browser canbe configured to receive and send all oure-mail automatically.

Message can be easily accessible.




Advantages of POP M ail (cont.)

Message can be automatically deletedfrom the server.

We can use powerful and intelligent e-mailsoftware.




Web-based E-mail




Advantages of Web-based E-mail

Easy log in.

No need to configure any program.

No set up is required.




Disadvantages of Web-based E-mail

It is time consuming.

Installation of latest web browsers are needed.

Most web-based services cannot match thefunctionality of a good e-mail package.

Advertising banners rotate, when we read ouremail.




M ail Forwarding Services




Advantages of M ail Forwarding Services

It will help to continue the use of our existinge-mail account given by our ISP.

Forwarding services let us choose amemorable or fun name.




Disadvantages of M ail Forwarding Services

It puts another layer between the sender andthe mail account.

Generally it is use to make money.




List of free POP M ail service providers

0 1. Amex Mail

0 2. C rosswinds

0 3. Newmail

04 . Peach World Network

05 . POPaccountprince dudhatra-9724949948



List of free POP M ail service providers (cont.)

06 . SoftHome

07 . ForFree

08 . Freemail

09 . Friendly E-mail

10 . HotPop




Web based E-mail

MrPost

MyOwn E-mail

Muslim E-mail

GhanaMail




Web based E-mail (cont.)

gurlmail

HotMail

Eudora Web-Mail

Fastermail.com

123india.com




M ail forwarding services

Easy To

FlashMail

Grabmail

IName




M ail forwarding services (cont.)

NetForward

Nederlands.com

USA.NET

Bigfoot

Bitmail




THANK YOU THANK YOU

computer networks prince dudhatra 9724949948

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