Computer Network

1. Computer Network

2. Text Book: • Behrouz A. Fourzen, “Data Communication and Networking”, 4th Edition, Tata McGraw • References Book: • A.S. Tanenbaum, “Computer Networks”, 3rd Edition, Prentince Hall India,1997. • W. Stallings, "Data and Computer Communication”, Macmillan Press,1989. • Kurose Ross: Computer Networking: A top down approach, 2nd edition, Pearson Education.

3. Chapter1 Introduction to ComputerNetwork

4. Introduction to Computer Network • 1.1 Definition, Merits, Demerits • 1.2 Network Models • 1.2.1 PAN, LAN, Campus Area Network(CAN), MAN, Country Area Network(CAN*), WAN, GAN • 1.2.2 Topological Models(Star, bus, distributed bus, mesh, tree, hybrid, ring) • 1.2.3 Client/Server, Peer-to-Peer & Active Network Model

5. Introduction • A computer network is a collection of computers and other devices (nodes) that use a common network protocol to share information and resources with each other over a network medium. • The network medium may be copper wire, fiber optics, microwave, infrared or even communicationsatellites. • The network may be of different sizes, shapes andforms.

6. Uses of the computer Network • Exchange of information between different computers. (File sharing) • Interconnected small computers in place of large computers. • Communication tools (voice , video) • Some applications and technologies are examples of Distributed system. (Railway reservation system, Distributed databases etc). • Advantages of Computer Network? • Better communication • Better connectivity • Better sharing of Resources • Bring people together

7. Uses of ComputerNetworks • BusinessApplications • HomeApplications • MobileUsers • SocialIssues

8. Business NetworkApplications • Resource sharing • Informationsharing • Communicationmedium • E-commerce

9. Business NetworkApplications

10. Home NetworkApplications • Access to remoteinformation • Person-to-personcommunication • Interactiveentertainment • Electronic commerce

11. Home NetworkApplications • In peer-to-peer system there are no fixed clients andservers.

12. Types ofNetworks • Local Area Networks • Metropolitan AreaNetworks • Wide AreaNetworks • Wireless Networks • Internetworks

13. Local AreaNetworks • Local area networks, generally called LANs, are privately- owned networks within a single building or campus of up to a few kilometers insize. Two broadcast LANs – bus andring.

14. Local AreaNetworks • In a bus network, at any instant at most one machine is the master and is allowed to transmit. All other machines are required to refrain fromsending. • In a ring, each bit propagates around on its own, not waiting for the rest of the packet to which itbelongs.

15. Metropolitan AreaNetworks • A metropolitan area network based on cableTV

16. Campus Area Network • A campus area network (CAN) is a network of multiple interconnected local area networks (LAN) in a limited geographical area. A CAN is smaller than a wide area network (WAN) or metropolitan area network (MAN). • A CAN is also known as a corporate area network (CAN). • In most cases, CANs own shared network devices and data exchange media.  • CAN benefits are as follows: • Cost-effective • Wireless, versus cable • Multi departmental network access • Single shared data transfer rate (DTR)

17. Wide AreaNetworks

18. Wide AreaNetworks

19. Global Area Network • A global area network (GAN) refers to a network composed of different interconnected networks that cover an unlimited geographical area. The term is loosely synonymous with Internet, which is considered a global area network. • Unlike local area networks (LAN) and wide area networks (WAN), GANs cover a large geographical area.  • Because a GAN is used to support mobile communication across a number of wireless LANs, the key challenge for any GAN is transferring user communications from one local coverage area to the next. • The most sought-after GAN type is a broadband GAN. The broadband GAN is a global satellite Internet network that uses portable terminals for telephony. The terminals connect laptop computers located in remote areas to broadband Internet.

20. Network Topology • Network topology is an arrangement of the various elements like links, nodes etc. of biological network. • It is topological structure of network, an depicted as physicaland logically. • Physical topology refers to placement of network various component including device location and cable installation. • Logical topology shows how data flows within a network, regardless of its physical design.

21. Network Topological Models

22. Bus Topology: • A networking topology that connects networking components along a single cable or that uses a series of cable segments that are connected linearly. A network that uses a bus topology is referred to as a “bus network.” Bus networks were the original form of Ethernet networks, using the 10Base5 cabling standard. Bus topology is used for: • Small work-group local area networks (LANs) whose computers are connected using a thin net cable • Trunk cables connecting hubs or switches of departmental LANs to form a larger LAN • Back boning, by joining switches and routers to form campus-wide networks

23. Advantages: • Easy to install • Costs are usually low • Easy to add systems to network • Great for small networks • Disadvantages: • out of date technology. • include difficult reconnection and fault isolation • Can be difficult to troubleshoot. • Unmanageable in a large network • If cable breaks, whole network is down

24. Ring Topology: • In a ring network, every device has exactly two neighbors for communication purposes. All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). • Advantages: • Short cables are required compared to other topologies • It works where there is no central site computer system • It is not dependent in a single cable or node • Disadvantages: • A failure in any cable or device breaks the loop and can take down the entire network. • It is rarely used in modern LAN • It is difficult to find out the error • Adding and removing any node or cable is difficult

25. Star Topology: • A star network features a central connection point called a "hub node" that may be a network hub, switch or router. All devices are connected to this central hub. Nodes communicate across the network by passing data through the hub. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet. Many home networks use the star topology these days. • Advantages: • A failure in any node or cable will only take down one computer's network access and not the entire LAN. • Easy to diagnose the fault • Easy to add and remove a node or cable • Disadvantages: • Compared to the bus topology, a star network generally requires more cable • If the hub fails, the entire network also fails

26. Tree Topology: • Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus and each hub functions as the root of a tree of devices. In this topology, several computers are linked in a hierarchical fashion in the network. A node acting as a server in the higher level can act as a client in the lower level. • Advantages: • It supports future expandability of the network much better than a bus or a star. • Failure in any single node does not affect the entire network. • Disadvantages: • If the main cable fails, entire network may go down • Failure in the hub brings down all the nodes below it

27. Mesh Topology: Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. It has point-to-point connection between every node in the network. Some WANs, such as the Internet, employ mesh routing. A mesh network in which every device connects to every other is called a full mesh. However, partial mesh networks also exist in which some devices connect only indirectly to others.

28. Advantages: • Failure in any one wire or node does fail the entire network • It is the most secure topology • Faster communication because of point-to-point connection • Disadvantages: • Most complicated network topology • Expensive in comparison to other topologies. • Difficult to find the error and trouble shoot.

29. Advantages and Disadvantages of Network Topologies

30. WirelessNetworks • Catagories of wirelessnetworks: • System interconnection - interconnecting the components of a computer using short-range radio. System interconnection use the master-slave paradigm. The system unit is normally the master, talking to the mouse, keyboard, etc., asslaves. • Wireless LANs - These are systems in which every computer has a radio modem and antenna with which it can communicate with othersystems. • Wireless WANs - operate below 1 Mbps, but the distance between the base station and the computer or telephone is measured in kilometers rather than in meters (Wireless LANs).

31. WirelessNetworks BluetoothConfiguration WirelessLAN

32. Internetwork • Aninternetworkis interconnected. formedwhendistinctnetworksare • ConnectingaLANandaWANorconnectingtwoLANsforms • an internetwork. • A common form of internet is a collection of LANs connected by a WAN where the label ''subnet'‘ is replaced by''WAN'‘.

33. Types ofNetwork • According to transmissiontechnology: • ▫ Broadcast networks: • A single communication channel is shared by all the machines on the network. Messages sent by any machines are received by all theothers. • ▫ Point-to-point networks: • Many connections between individual pairs of machines. Routing algorithms play an important role in point-to-point networks. A packet on this type of network may have to first visit one or more intermediatemachines.

34. NetworkingModel • Client/Server • P2P

35. Client ServerModel

36. Client ServerModel • This whole arrangement is called the client-servermodel. • It is widely used and forms the basis of much networkusage. • It is applicable when the client and server are both in the same building (e.g., belong to the same company), but also when they are farapart. • For example, when a person at home accesses a page on the World Wide Web, the same model is employed, with the remote Web server being the server and the user's personal computer being theclient. • Under most conditions, one server can handle a large number ofclients. • If we look at the client-server model in detail, we see that two processes are involved, one on the client machine and one on the servermachine. • Communicationtakestheformoftheclientprocesssendingamessage • over the network to the serverprocess. • The client process then waits for a replymessage. • When the server process gets the request, it performs the requested work or looks up the requested data and sends back areply.

37. Common NetworkServices • File services • Print services • Message services( e.g.email) • Application services • Database services

38. P2P Model(Peer-to-Peer) • In peer to peer networking architecture each computer (workstation) has equivalent capabilities andresponsibilities. • There is no server, and computers simply connect with each other in a workgroup to share files, printers, and internet access. • It is practical for workgroups of dozen or less computers, making it common in many SOHO (Small office/home office) environments, where each PC acts as an independent workstation that stores data on its own hard drive but which can share it with all other PCs on thenetwork.

39. P2P Model(Peer-to-Peer)

40. What do you understand by Computer Network? Explain with its advantages and disadvantages. Explain different types of Network models. Explain types of topology. Differentiate between client server network and peer-to-peer network.