Computer Networking Dinesh Kumar Ram PGT Comp.Sc. KV NAD Aluva

Welcome to the world of Networking

Computer Networks Computer network connects two or more autonomous computers. The computers can be geographically located anywhere.

Advantages of Networks Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (WWW) Communication Message broadcast Remote computing Distributed processing (GRID Computing)

Disadvantages of NETWORK The system are more sophisticated and complex to run. This can add to costs and you may need specialist staff to run the network. If s/w and files are held centrally, it may be impossible to carry out any work if the central server fails. If networks are badly managed services can becomes unusable and productivity falls. File security is more important especially if connected to WAN.

Transmission Media A medium of data transmission over a computer network is called a channel or a transmission medium

A number of various types of cables are used to transfer data over computer networks. 1.Twisted Pair Cable 2.Coaxial Cable 3.Optical Fibe rs Guided Media

Twisted Pair Cable

This is probably the most widely used cable for creating small computer networks. It contains four twisted pairs covered in an outer shield. These pairs are colour coded. An RJ-45 connecter is used to connect this cable to a computer. It is of two types: 1. UTP (Unshielded Twisted Pair): As the name suggests in UTP cables individual pairs are not shielded. 2. STP (Shielded Twisted pair): It is the same cable as the UTP, but with each pair shielded individually. An outer shield then covers all the pairs like in UTP. STP data connectors are used to connect STP cable to the computer. RJ-45 connectors can also be used to connect this cable to a computer.

Advantages It is simple Easy to install and maintain Physically Flexible Low weight Easily connected Inexpensive Disadvantages High attenuation, it cannot carry signal over long distances without the use of repeaters. Low bandwidth capabilities, unsuitable for broadband app. Support maximum data rates 1Mbps without conditioning and 10 Mbps with conditioning.

Coaxial Cable A coaxial cable consists of two conductors that share a common axis. The inner conductor is a straight wire and the outer conductor is a shield that might be braided or a foil.

Advantages Better than twisted pair cable. Used as shared cable network Used for broadband transmission. Higher bandwidth upto 400 MBPS Disadvantages Expensive Not compatible with twisted pair.

Optical Fiber Cable Optical Fibers are long, thin strands of glass about the thickness of a human hair. They are arranged in bundles called optical fiber cables and used to transmit data through light signals over long distances.

Advantages Immune to electrical and magnetic interference. Highly suitable for harsh industrial environments. Secure transmission and very high transmission capacity. Used for broadband transmission. Disadvantages Installation problem. Connecting two fibers together is a difficult process. Because of noise immunity, they are virtually impossible to tap. Light can reach the receiver out of phase. Connection losses are common problem Difficult to solder Most expensive.

An optical fiber has following parts: Core - It is the thin glass rod at the center through which the light travels Cladding - It is the outer optical material surrounding the core that reflects the light back into the core Buffer coating - It is the plastic coating that protects the cable from damage and moisture Buffer Coating(Jacket)

Networking Devices

1.Modem Allow computers to communicate over a telephone line Enable communication between networks or connecting to the world beyond the LAN Cannot send digital signal directly to telephone line Sending end: MODulate the computer’s digital signal into analog signal and transmits Receiving end: DEModulate the analog signal back into digital form Modems typically have the following I/O interface: A serial RS-232 communication interface An RJ-11 telephone-line interface (a telephone plug)

2. NIC: An NIC (Network Interface Card) is a device that enables a computer to connect to a network and communicate.

3. HUB A Hub is an electronic device that connects several nodes to form a network and redirects the received information to all the connected nodes in broadcast mode.

Distribution of Network through Hub

4. SWITCH A Switch is an intelligent device that connects several nodes to form a network and redirects the received information only to the intended node(s).

Extending Network through Switch

5. GATEWAY A Gateway is a device, which is used to connect different types of networks and perform the necessary translation so that the connected networks can communicate properly.

6. BRIDGE A bridge is a device, which is used to connect two local- area networks or two segments of the same LAN

7. REPEATER A repeater is a network device that amplifies and restores signals for long distance transmission.

8. ROUTER A 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. A router creates and maintains a table of the available routes for long distance transmission.

Questions Q1. Differentiate between Hub and Switch? Q2. Why is a switch called an intelligent hub? Q3. Suggest the placement of the following devices with justification: (i) Repeater (ii) Hub (iii) Switch Q4. What is the roll of NIC in computer Network? Q5. What is Ethernet ? What is Ethernet card ? Q6. An organization have two building and each building contains more then 50 computers. Now they are facing problem of low data transmission between these two building. Can you suggest the device name which will use for rectify the problem

5-30 Question? A good question deserve a good grade…