NETWORK

What is Network?•Networks needs to interconnect at a distance by a form of point to point or point to multiple point connected media

•A network is a group of computers connected together in such a way as to allow

•Networks that are interconnected have proven to be low cost, reliable, and efficient means of communicating at a distance

Network Terminology

Node: anything connected to the network, usually a computer, but it could be a printer or a scanner Segment: any portion of a network that is separated by a switch, bridge or a router from another part of a network.

Backbone: the main cabling of a network that all of the segment connect to. Usually, the backbone is capable of carrying more information than the individual segments.

Topology: The way each node is physically connected to the network

Network Benefits Some benefits of computer networks are given below.

(1) Computers which are connected through a network can share resources as hard drives, printers, scanners etc with each other.

(2) They can send file from one computer to another quite easily.

(3) You can connect all the computers which are connected through a network to the internet by using a single line. So it means that you can save the connection cost for each computer but you internet connection must be fast.

(4) IF you want to access data from the other computer which is the part of network then you can access data from that computer.

(5) Users can run those programs which are not installed on their computers but are installed on any other user's computer. This is a very huge advantage, and you can get benefit from it in many circumstances. For example, suppose you have not enough space in your computer to install a program so in this case, if your desired program is available on other user's computer then you can run that. Similarly, if you have space in your computer then you can copy that program other user's computer into your PC.

NETWORK HARDWARES

•Hub

•Gateway

•Router

•Switches

•Repeater

•Bridges

HUBS

•A hub is the place where data converges from one or more directions and is forwarded out in one or more directions.

•Seen in local area networks

GatewaysA gateway is a network point that acts as an entrance

to another network. On the internet, in terms of routing, the network consists of gateway nodes and host nodes.

Host nodes are computer of network users and the computers that serve contents (such as Web pages).

Gateway nodes are computers that control traffic within your company’s network or at your local internet service provider (ISP)

RoutersA router is a device or a software in a computer that determines the next network point to which a packet should be forwarded toward its destination.

Allow different networks to communicate with each otherA router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet.

A packet will travel through a number of network points with routers before arriving at its destination.

Routers

SwitchesAllow different nodes of a network to communicate directly with each other.

Allow several users to send information over a network at the same time without slowing each other down.

What is the difference between Hub, Gateway and Router?

Bridge: device to interconnect two LANs that use the same logical link control protocol but may use different medium access control protocols.

Router: device to interconnect similar networks, e.g. similar protocols and workstations and servers

Gateway: Device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment

Repeater Bridges

NETWORK TOPOLOGIES

Network Topologies• LANs and WANs - Geographical coverage

• LANs– A single geographical location, such as office building, school, etc– Typically High speed and cheaper.

• WANs– Spans more than one geographical location often connecting separated

LANs– Slower– Costly hardware, routers, dedicated leased lines and complicated

implementation procedures.

Network Topologies• Topology - Physical and logical network layout

– Physical – actual layout of the computer cables and other network devices– Logical – the way in which the network appears to the devices that use it.

• Common topologies: – Bus, ring, star, mesh and wireless

Bus topologyUses a trunk or backbone to which all of the computers on the network connect.

• Systems connect to this backbone using T connectors or taps.• Coaxial cablings ( 10Base-2, 10Base5) were popular options years ago.

Bus TopologyAdvantageAdvantage DisadvantageDisadvantage

Cheap and easy to implement

Network disruption when computers are added or removed

Require less cable A break in the cable will prevent all systems from accessing the network.

Does not use any specialized network

equipment.

Difficult to troubleshootDifficult to troubleshoot

Ring Topology• Logical ring

– Meaning that data travels in circular fashionfrom one computer to another on the network.

– Typically FDDI, SONET or Token Ringtechnology are used to implement a ringnetwork

– Ring networks are most commonly wired in a star configuration

• Token Ring has multi-station access unit (MSAU), equivalent to hub or switch. MSAU performs the token circulation internally.

Ring Topology

AdvantageAdvantage DisadvantageDisadvantage

Cable faults are easily

located, making

troubleshooting easier

Expansion to the network

can cause network

disruption

Ring networks are

moderately easy to install

A single break in the cable

can disrupt the entire

network.

Star Topology

• All computers/devices connect to a central device called hub or switch.• Each device requires a single cable• point-to-point connection between the

device and hub. • Most widely implemented • Hub is the single point of failure

Star Topology

AdvantageAdvantage DisadvantageDisadvantage

Easily expanded without

disruption to the network

Requires more cable

Cable failure affects only a

Single User

A central connecting

device allows for a single

point of failure

Easy to troubleshoot and

Isolate Problems

More difficult toMore difficult to

implementimplement

Mess Topology

• Each computer connects to every other.• High level of redundancy.• Rarely used.

– Wiring is very complicated– Cabling cost is high– Troubleshooting a failed cable is tricky– A variation hybrid mesh – create point to point connection between specific network devices,

often seen in WAN implementation.

AdvantageAdvantage DisadvantageDisadvantage

Provides redundant paths between Devices

Requires more cable than

the other LAN topologies

The Network can be expandThe Network can be expand

Without Without disruption to current uses

Complicated ImplementationComplicated Implementation

Wireless networking

• Do not require physical cabling

• Particularly useful for remote access for laptop users

• Eliminate cable faults and cable breaks.

• Signal interference and security issue.

AdvantageAdvantage DisadvantageDisadvantage

Allows for wireless remote access

Potential security issues

associated with wireless

transmissions

Network can be expanded

Without disruption to

current users

Limited speed in

comparison to other

network topologies

NETWORK STRUCTURES

LANLOCAL AREA

NETWOK

A local area network (LAN) is a group of computers

and associated devices that share a common communications

line or wireless link. Typically, connected devices share the

resources of a single processor or server within a small

geographic area (for example, within an office building).

Usually, the server has applications and data storage that are

shared in common by multiple computer users. A local area

network may serve as few as two or three users (for example,

in a home network) or as many as thousands of users

MAN

A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network. Examples of metropolitan area networks of various sizes can be found in the metropolitan areas of London, England; Lodz, Poland; and Geneva, Switzerland. Large universities also sometimes use the term to describe their networks. A recent trend is the installation of wireless MANs.

WAN

A computer network that spans a relatively large

geographical area. Typically, a WAN consists of two or

more local-area networks (LANs). Computers connected to a

wide-area network are often connected through public

networks, such as the telephone system. They can also be

connected through leased lines or satellites. The largest

WAN in existence is the Internet.

NETWORK PROTOCOLS

What is Network Protocol

A network protocol defines a "language" of rules and

conventions for communication between network devices. A

protocol includes formatting rules that specify how data is packaged

into messages. It also may include conventions like message

acknowledgement or data compression to support reliable and/or

high-performance network communication.

Types of Network Protocols

1.IP (Internet Protocol)

2.TCP (Transmission Control Protocol)

3.UDP (User Datagram Protocol)

4.FTP (File Transfer Protocol)

5.HTTP (Hyper Text Transmission Protocol)

6.SMTP (Simple Mail Transfer Protocol)

Internet Protocol

The Internet Protocol (IP) is the method or protocol by

which data is sent from one computer to another on the

Internet. Each computer (known as a host) on the Internet has

at least one IP address that uniquely identifies it from all other

computers on the Internet. When you send or receive data (for

example, an e-mail note or a Web page), the message gets

divided into little chunks called packets. Each of these packets

contains both the sender's Internet address and the receiver's

address.

Transmission Control Protocol (TCP)

TCP (Transmission Control Protocol) is a set of

rules (protocol) used along with the Internet Protocol (IP)

to send data in the form of message units between

computers over the Internet. While IP takes care of

handling the actual delivery of the data, TCP takes care of

keeping track of the individual units of data (called

packets) that a message is divided into for efficient

routing through the Internet.

File Transfer Protocol (FTP)

File Transfer Protocol (FTP), a standard Internet protocol, is the

simplest way to exchange files between computers on the Internet. Like

the Hypertext Transfer Protocol (HTTP), which transfers displayable

Web pages and related files, and the Simple Mail Transfer Protocol (

SMTP), which transfers e-mail, FTP is an application protocol that uses

the Internet's TCP/IP protocols. FTP is commonly used to transfer Web

page files from their creator to the computer that acts as their server for

everyone on the Internet. It's also commonly used to download programs

and other files to your computer from other servers.

User Datagram Protocol (UDP)UDP (User Datagram Protocol) is a communications protocol

that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP) and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP. The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.

Hyper Text Transfer Protocol (HTTP)

HTTP - the Hypertext Transfer Protocol -

provides a standard for Web browsers and servers to

communicate. The definition of HTTP is a technical

specification of a network protocol that software must

implement.