Prepare 2 COMPUTER_NETWORKS Lecture 1 & 2.pptx

This lecture is about Computer Networking.

1. COMPUTER NETWORKS By Khalid Hamid PhD Scholar

2. A computer network consist of two or more components that are connected together to share information and resources. The resources may include printers, hard disk, scanner or programs etc. Computer Networks

3. Computer network can be used in an office. Internet is also an example of computer network. Applications/Benefits Information and Resource Sharing Money Saving Communication Internet Access Sharing Data Security and Management Entertainment Transferring Funds Examples

4. Some disadvantages are as follows: Hardware, Software & Setup Costs Hardware & Software Management Costs Undesirable sharing Illegal or Undesirable Behavior Data Security Concerns Client A client is a computer in the network that is connected with a server to access different resources. The client computer sends request to the server. Server A server is a computer that provides services to the computers and other devices connected to the network. Disadvantages

5. Three main types of computer networks are LAN (Local Area Network) It is the most common types of network. It covers a small area. It usually connect the computer and other devices within one office or a building. Examples In a computer lab, there are 40 computers connected through LAN.The students can share software, files and data in the lab. In internet club, many computers can be connected through LAN. These computer can share single connection of internet. Types of Computer Networks

6. This type of network covers a large area. It connects computers and other devices in different cities and countries. Wan usually consist of several LANs connected together. Computers in WAN are often connected through telephone lines. They can also connect through satellites. Examples The network connecting ATMs of a bank in different cities. The network connecting NADRA offices in different cities of Pakistan. Internet connects million of users all over the world to share information. WAN (wide area network)

7. This type of network covers an area of city. MAN is larger than LAN but smaller than WAN. It is usually used to connect two more LAN in a city or town. Examples The network connecting different branches of a company in a city. The network connecting different campuses of a college in a city. Cable TV network in a city MAN (metropolitan area network)

8. Data communication is a process of transferring data electronically from one place to an other place. Data can be transferred by using different media. Sending Device A device that send message is called sending device. It is also called source or transmitter. Receiving device A device that receive the message is called receiving device. It is also called sink. Communication Device Communication device are used to transmit messages between sending and receiving device through communication medium. Data Communication

9. Transmission Medium Transmission medium is used to carry messages from one place to another place.

10. Types of Data Transmission The two forms of data transmission Digital Data Transmission The transfer of data in the form of digital signals is called digital data transmission. Digital signal is a sequence of voltage represented in binary form. The digital signals are in the form of electrical pulses of ON and OFF.

11. Analog Data Transmission Analog data transmission is the transmission of data in a continuous wave form. For example sound wave are analog signals. When we talk, we emit sound waves that consist of waveforms of high and low pressure. Analog signals are measure in volts and its frequency is in Hertz.

12. The path through which data is transmitted from one place to another place is called channel. It is also known as a communication media. Types Bounded /Guided Transmission Media Communication device are directly connected with each other by using physical media like wires. Examples Twisted Pair Twisted pair is the most commonly used physical transmission medium. It is used in local area network. Communication channels

13. Types of Twisted pair cable Two types Shielded Twisted Pair Unshielded Twisted Pair

14. Characteristics of Twisted Pair Different characteristics of twisted pair are as follows: It is an inexpensive transmission medium. It is easy to install. It can transfer data to a short distance. Coaxial Cable Coaxial cable consist of copper wire covered by insulating material. The insulated copper wire is covered by copper mesh. Characteristics of Coaxial Cable Different characteristics of coaxial cable are: It is more expensive transmission medium than twisted pair. It can be installed very easily.

15. Fiber Optics Fiber optics cable consist of thin strands of glass or plastic called core. The strands are thin like human hair. The core is center of the fiber cable that uses light to transmit data.

16. Advantages of Fiber Optics It is not affected by electromagnetic waves. It is more secure and reliable form of data transmission. Fiber optic is lighter and smaller in size. Fiber optic networks work at very high speed. Disadvantages It is difficult to install. It is expensive.

17. In unguided media, communication devices communicate with each other through air or space using broadcast radio signals, microwave signals and infrared signals. Data can be transferred all over the world using this media . It is called unbounded media. Examples Microwave System Microwave are radio wave that are used to provide high speed transmission. Both voice and data can be transmitted through microwave. Data is transmitted through the air from one microwave station to another similar to radio signals. Wireless /Unguided Transmission Media

18. Communication Satellite Satellite communication is a space station that receive microwave signal from earth based station . It amplifies the signals and transmit them back to different earth based stations.

19. Broadcast Radio Broadcast radio is wireless transmission medium. It distributes radio signals through the air over long and short distance. Example of short range broadcast radio is bluetooth. Cellular Communication Cellular communication is a wireless communication system. It is widely used all over the world for mobile communication. A cellular communication system is used to transmit text, images, voice and video. Infrared Infrared is a wireless transmission medium. It sends signals using infrared light waves.

20. Communication and Network Devices The hardware used to transmit data, instruction between sending and receiving device is called communication device. A communication device at sending end sends data to a communication channel. A communication device at receiving end receives data to a communication channel. Modem Modem stands for modulator/demodulator. It is commonly used communication device. Modem send and receive data from one computer to another computer on the internet through telephone lines. The sending and receiving computers both have modems.

21. Types of Modem Different types of modem are as follows: External Modem External modem is attached to the system unit as an external device through telephone line. It is connected to telephone wall jack by another cable. It require external power supply. It is easy to setup. Internal Modem Internal modem is circuit board that is inserted into an expansion slot on the motherboard. Internal modem cannot be moved from one computer to another easily. It is difficult to setup than other types of modem.

22. Wireless Modem Wireless modem transmits the data signals through the air instead of cable. It is also known as radio-frequency modem. It is designed to work with cellular technology and wireless local area networks.

23. ISDN Modems ISDN modem allows digital transmission of data over telephone lines. It is also known as ISDN adapter. It supports data transfer rates up to 1.54 Mbps. DSL Modem DSL modem allows faster transmission over the standard telephone lines. It is faster than ISDN.There are two types of DSL. ADSL It stand for Asymmetric Digital Subscriber Line. It uses faster transmission downstream than upstream. It provides the upload speed of up to 640 Kbps and download speed of up to 8.1 Mbps.

24. SDSL It stands for Symmetric Subscriber Line. It uses the same transmission rate for both directions. It transfers data at 3 Mbps approximately in both directions. Cable Modem Cable modem is also known as broadband modem. Cable modem is a stand-alone device connected with a cable to USB port. It sends and receives data over the cable television network. It provides faster internet speed than dial-up modem,DSL modem and ISDN.

25. Satellite Modem Satellite modem is used to send and receive data using satellite technology . It is commonly used for high speed internet service.

26. Wireless Access Point Wireless access point is central communication device. It allows computer and other devices to transfer data wirelessly among themselves or to a wired network. Wireless access point have a high quality antennas for optimal signals. HUB A hub also called concentrator or multistation access unit (MAU) . It provide the central point for cables in a network. Hubs also transmit signals and have multiple ports to which devices are connected.

27. Hub is physical layer device. It connects the computers to a network. It broadcasts all messages to every computer on the network but only the intended recipient computer takes the message.

28. Network Switch Network switch is a more intelligent device than Hub. The switch improves the efficiency of data transfer in the network. It receives a message from any device connected to it and than transmits the message only to that device for which the message was meant . It can also handle multiple communication channels at the same time.

29. Network Bridge A network bridge can be used in computer networks to interconnects two LANS and to separate network segments. A segments is a section of network separated by bridges , switches & routers. The bridge uses MAC address information for making decision to forward data packets. Routers A router is a communication device that connects multiple computers or others routers together. It connects multiple networks using similar or different protocols.

30. A network can be arranged in different ways. The physical layout or arrangement of connected devices in a network is called topology. It is the shape of a network. Different network topologies are as follows: Bus Topology Bus topology is the simplest type of network. It supports a small number of computers. In bus topology, all computer or network nodes are connected to a common communication medium. This medium is often a central wire known as bus. The terminators are used at the end of a bus to absorb signals. A collision can occur in a bus topology if two computer transmit data at same time. Network Topologies

31. Working of Bus Network The sending computer send data and destination address through the bus. The data and address move from one computer to another in a network. Each computer checks the address. If it matches with the address of a computer, the computer keeps the data. Otherwise the data moves to the next computer. Advantages Simple and easy to use. It requires small length of cable to connect computes. Less expensive If one node fails, it does not affect the rest of the network.

32. Disadvantages It only supports small number of computers. If computer increases ,speed will slow down. It is difficult to troubleshoot.

33. Star Topology All computers in star topology are connected with a central device called hub. Star topology is the best LAN topology. It is easy to remove or add a device in this topology. It is easy to troubleshoot than other topologies. Working Sending computer sends data to hub. Hub send data to receiving computer. Each computer in star network communicates with a central hub.

34. Advantages Easy to maintain and modify network. Adding or removing computers can be done without disturbing the network. Finding faults become very simple. Single computer failure does not bring down the whole network. Disadvantages IF central network break, the entire network break down. More expensive. Requires a large length cable to connect.

35. Ring Topology In this topology, each computer is connected to next computer with the last one connected to the first . Thus a ring of computer is formed. Working of Ring Network Every computer is connected to next in a ring. Each computer receive message from the previous computer and transmit it to next computer. The message is passed around the ring until it reaches the correct destination computer.

36. Advantages It is less expensive than star topology. Every computer has equal access to the network. Disadvantages Failure of one computer affect whole network. It is difficult to troubleshoot. Adding or removing computers affect the whole network.

37. Tree Topology A tree topology combines the characteristics of bus and star topologies. It consist of different groups of computers attached in star topology. The groups are than connected to a bus backbone cable. Advantages If one of them gets damaged other networks are not affected . Easier maintenance and fault finding. Disadvantages If backbone line breaks, the entire segment goes down. Huge cabling is needed. A lot of maintenance is needed.

38. Mesh Topology In mesh topology, every device in a network is physically connected to every other device in a network. A message can be sent on different possible paths from source to destination. Mesh network are not used much in LAN. Mostly used in WAN. Advantages It is easy to troubleshoot. If one link becomes unusable, it does not harm the entire system. Disadvantages Very expensive. It is difficult to install .

39. Network Protocols A standard used by networks for communication between different devices connected to a network is called protocol. It represent an agreement between the communication devices. The device cannot communicate without a protocol. Types of protocol Some important protocols are as follows: Ethernet Ethernet is most widely used protocol. It uses an access method called CSMA/CD (Carrier Sense Access/Collision Detection). It is a system

40. Where each computer listens to the cable before sending anything through network. The computer transmit only if the network is clear. If some other node is already transmitting data on the cable , the computer waits and attempts again when line is clear. ATM Asynchronous Transfer Mode (ATM) protocol transmit data at a speed off 155 Mbps and higher.ATM works by transmitting all in small packets of a fixed size. It supports a variety of media such as video, CD quality audio and imaging.

41. FDDI Fiber Distributed Data Interface protocol is used primarily to interconnect two or more local area networks. It uses token passing access method. It operates over fiber optic cable at 100 Mbps. Token Ring Token ring protocol was developed by IBM. It uses token passing access method. An electronic token moves from one computer to the next .A computer can transmit data ,only if it has empty token. It can operate transmission speed of 4 Mbps to 16 Mbps.

42. TCP Transmission Control protocol is the protocol suite used for communications between hosts in most local networks and on the internet. It can be used to enable network communication in a local area networks and wide area networks as long as host support the protocol.TCP is widely supported and included in operating system such as Windows 7, XP, Vista etc.

43. THANK YOU