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Introduction to computer networking chapter 2
- 1. 1 CHAPTER TWO INTRODUCTION TOCOMPUTER NETWORKS
- 2. Computer Networks • Anetwork is a set of devices (often referred to as nodes) connected by communication links to communicate data. • A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. 2
- 3. Network Applications 3 • Computersystems and peripherals are connected to form a network. • They provide numerous advantages: – Resource sharing such as printers and storage devices – Exchange of information by means of e-mails and FTP – Information sharing by using Web or Internet – Interaction with other users using dynamic web pages – Video conferences – Parallel computing
- 4. Types of Computernetworks • Computer networks are classified based on various factors. • They include: • Geographical span -LAN, MAN and WAN • Administration -Private network & public network • Architecture-Client/Server & peer-to- peer • A private network is used inside an organization. 4
- 5. Types of Network-Geographical Span 5 LAN • A local area network (LAN) is usually privately owned and links the devices in a single office, building, or campus. • LAN size is limited to a few kilometres. • In the early 1980s, LANs might have consisted of a handful of computers connected in a peer- to-peer fashion. • Today’s LANs are typically much larger and more complex client/server networks.
- 6. MAN 6 • A metropolitanarea network (MAN) is a network with a size between a LAN and a WAN. • It normally covers the area inside a town or a city. • MAN-is A network that is larger than a LAN and connects clients and servers from multiple buildings. • Because of the distance it covers, a MAN may use different transmission technology and media than a LAN.
- 7. WAN 7 • A widearea network (WAN) provides long- distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world. • The largest and most varied WAN in the world is the Internet.
- 8. Types of Network-Architecture 8 •Computers can be positioned on a network in different ways relative to each other. • They can have different levels of control over shared resources. • They can also be made to communicate and share resources according to different schemes. • The following sections describe two fundamental network models:
- 9. Peer-to-Peer • In apeer-to-peer network:- • There are no dedicated servers. • There is no hierarchy among the computers. • All the computers are equal and therefore are known as peers. • Each computer functions as both a client and a server. • There is no administrator responsible for the entire network. 9
- 10. Peer-to-Peer Networks 10 • Thesimplest form of a network is a peer- to-peer network. • In a peer-to-peer network, every computer can communicate directly with every other computer. • By default, no computer on a peer-to-peer network has more authority than another. • However, each computer can be configured to share only some of its resources and prevent access to other resources.
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- 12. Client/Server Networks 12 • Anetwork that uses a server to enable clients to share data, data storage space, and devices is known as a client/server network. • Client—A computer on the network that requests resources or services from another computer on a network. • Clients usually take the form of personal computers, also known as workstations. • Every computer on a client/server network acts as a client or a server. • Clients on a client/server network do not
- 13. Client/Server Networks 13 • Clientsand servers communicate through connectivity devices such as switches or routers. • Server—A computer on the network that manages shared resources; servers usually have more processing power, memory, and hard disk space than clients. • To function as a server, a computer must be running an NOS (network operating system). • An NOS is a special type of software
- 14. Client/Server Networks 14 – Restrictwhen and from where users can access the network. – Dictate which rules computers will use to communicate. – Supply applications to clients. • Examples of NOS: UNIX and Linux, Microsoft Windows Server 2003 or Server 2008, and Mac OS X Server. • (But, stand-alone computer, or a client computer, uses an operating system, such as Windows XP/7 or Windows Vista, which has more limited resource management capabilities.)
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- 16. Client/Server • In anenvironment with more than 10 users, a peer-to-peer will probably not be adequate. • Therefore, most networks have/required dedicated servers. • A dedicated server is one that functions only as a server and is not used as a client or workstation. • Client requests the server to serve the requests. 16
- 17. Specialized Servers • 1-FileServers • File servers offer services that allow network users to share files. • 2- Print Servers • Allow users to share printers • Allow multiple and simultaneous access to printing facilities. • 3- Database Servers • Database server can provide a network with powerful database services. • 4 -Application Servers • Servers store vast amounts of data that is organized to make it easy to retrieve. • An application server differs from a file server in that with file server the data or file is downloaded to the computer which making the request. 17
- 18. Specialized Servers • 5-MailServers • Mail servers - separate server and client applications. • Data selectively downloaded from the server to the client. • 6-Web Servers • Stores different web pages. • 7- Proxy Server • A Proxy Server implements Internet connectivity and network security for an 18
- 19. Network Topologies • Typesof Connection • There are two possible types of connections: point-to-point and multipoint. • Point-to-Point • A point-to-point connection provides a dedicated link between two devices. • The entire capacity of the link is reserved for transmission between those two devices. e.g connection b/n television and its remote control 19
- 20. Physical Topology • Thetopology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another. • The topology- is physical layout of a computer network. • Topologies vary according to the needs of the organization, available hardware and expertise. • There are five basic topologies possible: • Bus • Ring 20
- 21. Bus • A bustopology is multipoint connection. • One long cable acts as a backbone to link all the devices in a network. 21
- 22. Bus 22 Advantages • Connecting acomputer or peripheral to a linear bus is easy. • This topology requires least amount of cabling to connect the computers and therefore, less expensive. • It is easy to extend a bus since two cables can be joined into longer cable with a connector. Disadvantages • Entire network shuts down if there is a
- 23. Ring 23 • In aring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it.
- 24. Ring 24 Advantage • Ring topologyis easy to install and reconfigure. • Every computer is given equal access to the ring. • Hence, no single computer can monopolize the network. Disadvantages • Failure in any cable or node breaks the loop and can take down the entire
- 25. Star • In astar topology, each device has a dedicated point-to-point link only to a central controller, usually called a hub. • The devices are not directly linked to one another. 25
- 26. Star • Advantages ofStar • Star topology is easy to install and wire. • The network is not disrupted even if a node fails or is removed from the network. • Fault detection and removal of faulty parts is easier in star topology. • Disadvantages of Star • It requires a longer length of cable. • If the hub fails, nodes attached to it are disabled. • The cost of the hub makes the network 26
- 27. Mesh • In amesh topology, every device has a dedicated point-to-point link to every other device. 27
- 28. Mesh • Advantages ofMesh Topology • The use of large number of links eliminates network congestion. • If one link becomes unusable, it does not disable the entire system. • Disadvantages of Mesh Topology • The amount of required cabling is very large. • As every node is connected to the other, installation and reconfiguration is very 28
- 29. Hybrid 29 • A networkstructure whose design contains more than one topology is said to be hybrid topology. • Hybrid topology inherits merits and demerits of all the incorporating topologies.