1. DATA COMMUNICATION AND NETWORKS Computers can be used in two modes: stand-alone mode and communication mode Communication of messages electronically over a long distance is known as telecommunication

2. DATA COMMUNICATION AND NETWORKS contd.. When a computer is used to transmit electronically textual, numeric, audio or video data, to a distant location, the process is called data communication The technology that combines computer technology and telecommunication technology has come to be known as information technology

3. DATA COMMUNICATION USING MODEMS Computer to computer communication can be made using modems and using networks The devices that perform these special tasks of encoding and decoding data are known as modems, a term derived from the words modulation and demodulation

4. COMPUTER NETWORKS Based on geographical area Local area networks (LANS) Wide area networks (WANS) Metropolitan area networks (MANS) International network (Internet) Intranet

5. COMPUTERNETWORKS contd.. Based on how computer nodes are used Client-server networks (CSNS) Peer-to-peer networks (PPNS) Value-added networks (VANS)

6. Local Area Networks A network of computers and other devices located relatively close to each other in an office (or in a building) and connected by a wire (or a wireless link) is called a local area network (LAN) A storage device that is shared by all the computers is called the file server A computer (or any other device) connected to the networking cable is called a node

7. Wide Area Networks A network that connects two or more LANs spread across a large geographical area is called a wide area network (WAN)

8. Metropolitan Area Networks Metropolitan area networks (MANs) are the networks that are in between LANs and WANS. These networks are created to provide city-wide services in large cities and thus the name metropolitan. MANs fill the need of extending LAN capabilities to larger geographic areas. They are used to connect LANs across different offices in a city or to link LANs to WANS

9. Internet This requires connecting together different types of networks all over the world by using systems known as gateways. The gateway computers make connections and provide necessary interface. A collection of networks connected to each other (network of networks) is called the Internet

10. Intranet It refers to a network that belongs to a particular organization or company. It uses the same tools and protocols that are used in internet and therefore it can be used like the internet

11. Client-Server Networks Another way of organising networks is to make one node (computer) to serve the storage needs of all other nodes (computers) in the network. This kind of arrangement is called a client-Server network (CSN). The computer that stores data and programmes is called the server and the computer that uses the data and software of the server is called the client

12. Peer-to-Peer Networks In this arrangement each node has access to the resources of other nodes. That is users can have access to the hard disks and printers attached to other computers

13. Value-Added Networks These services may include access to different types of databases, e- mail, games, etc. WANs that add such services to the existing capabilities are known as value- added networks (VANs)

14. NETWORK TOPOLOGIES An arrangement of connections that link computers and other devices in a network is known as network topology Hierarchical (or tree) topology Linear bus (or horizontal) topology Star topology Ring (or hub) topology Hybrid (or mesh) topology

15. Hierarchical Topology microcomputers are connected to minicomputers which intrun are connected to a large mainframe computer

16. Linear Bus topology connects several nodes (computers and other devices) with a single network cable. All data travel along a single communication cable to which the nodes are connected

17. Star Topology Uses a central controlling computer that controls and routes all communication requests. Each node is directly linked to the central computer known as the hub. The arrangement is similar to the hierarchical one, except that the star topology uses only a single level of hierarchy

18. Ring Topology All computers and devices are connected in a circular form. Each node is connected to the next one. In most cases, data flows in one direction only

19. Hybrid Topology Two or more of the above topologies may be combined to form the hybrid topology. Due to the multiplicity of paths available, data can be routed around failed links or busy nodes.

20. NETWORK PROTOCOLS AND SOFTWARE When computers use a common channel for data communication, they follow some rules and procedures to prevent any data collisions. These procedures (a set of standards for communication) are called the network protocols

21. NETWORK PROTOCOLS AND SOFTWARE A protocol is simply an agreement between the communicating parties on how communication is to proceed. Violating the protocol will make the communication more difficult, if not impossible

22. NETWORK PROTOCOLS AND SOFTWARE The Internet uses a protocol known as transmission control protocol / internet protocol (TCP/IP) for routing information over the network. Internet protocol incorporates basic rules such as the composition of internet address, the size of the data to be delivered, and so forth

23. NETWORK APPLICATIONS Bulletin board service (BBS) Information services Telecomputing Teleconferencing Workgroup computing Electronic funds transfer (EFT) Electronic data interchange (EDI) Electronic commerce