1. End Show Local Area Network (LAN) - LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers. Metropolitan Area Network (MAN) - MAN is basically a bigger version of a LAN and normally uses similar technology. It might cover a group of near by corporate offices or a city and might be either private or public. Wide Area Network (WAN) - Often a network is located in multiple physical places. Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services. Types of Network

2. End Show Local Area Network (LAN) Star topology Ring topology Mesh topology Bus topology Pear to Pear

3. End Show Wide Area Network (WAN)

4. End Show WAN interconnects computers (hosts), which are located geographically at long distances. The hosts are connected by communication subnet. The job of the subnet is to carry messages from host to host. The routers are specialized computers. When data arrive on incoming line, the router chooses an outgoing line to forward them on. The collection of communication lines and routers (but not hosts) forms the subnet. Many different networks, including LANs, MANs and WANs are together form an Internet. Wide Area Network (WAN)

5. End Show An example for a WAN (Wide Area Network) Telecommunication Satellite

6. End Show Transmission Media

7. End Show Twisted pair A basic twisted-pair cable consists of two strands of copper wire twisted together. This twisting reduces the sensitivity of the cable to electro magnetic interference.

8. End Show Shielded twisted pair Shielded twisted-pair cabling consists of one or more twisted pairs of cables enclosed in a foil wrap and woven copper shielding. The shield further reduces the tendency of the cable to radiate EMI and thus reduces the cable’s sensitivity to outside interference.

9. End Show Unshielded twisted pair Unshielded twisted-pair cable doesn’t incorporate a braided shield into its structure. RJ 45 Connector

10. End Show Coaxial Cable Coaxial cables were the first cable types used in LANs. Gets its name because two conductors share a common axis; the cable is most frequently referred to as coax.

11. End Show Fiber Optics The centre conductor of a fiber-optic cable is a fiber that consists of highly refined glass or plastic designed to transmit light signals with little loss. A glass core supports a longer cabling distance, but a plastic core is typically easier to work with. The fiber is coated with a cladding that reflects signals back into the fiber to reduce signal loss. A plastic sheath protects the fiber.

12. End Show As shown in figure, microwave communication can take two forms: terrestrial (ground) links and satellite links. The frequencies and technologies employed by these two forms are similar, but as you’ll see, distinct differences exist between them. Uplink Down link Microwave

13. End Show Connectivity Devices Hubs The hub's major function is to replicate data it receives from one device attached to it to all others.

14. End Show Repeaters Any electrical signal reaching the repeater from one segment, will be amplified and retransmitted to the other segment. Using repeaters slows the signal's propagation, and thus the amount of repeaters should be limited.

15. End Show Bridges Bridges are used to increase the number of addressable nodes on a network or to link two geographically distant but similar networks. Routers A major feature of a router is that it chooses the best route between networks that may have multiple paths between them. IP addressing and subnet masking are used to route packets

16. End Show Modems A modem is a device that converts digital data originating from a computer to analog signals used by voice communication networks, such as the telephone system. A modem may also convert analogue data originating from a (say, a telephone line) to digital data for use by a computer. Digital Signal Analog Signal Modulation Demodulation Modem Computer Digital Device Analog Device Digital Signals Analog Signals Telephone

17. End Show Digita Signal Analog Signal

18. End Show Internal Modem External Modem

19. End Show Server - Computer that provide shared resources to networks Printer Microcomputer Printer Client Server Microcomputer Minicomputer Client - Computer that access shared networks resources provided by server

20. End Show Gateways Gateways interface two dissimilar networks. Gateways translate one network protocol into another, thus overcoming both hardware and software incompatibilities.

21. End Show The Internet The Internet is a giant world wide network that connects the Computer systems located throughout the world that are willing to share their resources.

22. End Show The Internet  The Internet is Network of Networks

23. End Show Not centralized Can be login to another Computer Public Domain Site Web servers Mail servers The Internet is a Client /Server system

24. End Show Electronic Mail (E-Mail) Electronic Commerce (E-Commerce) Tele Medicine Teleconferencing Internet Shopping Tele Education Internet Facilities

25. End Show HTML (Hyper Text Mark Up Language) HTTP (Hyper Text Transfer Protocol)

26. End Show World Wide Web -WWW * Website * Home Page

27. End Show Internet Service Providers ( ISP ) Lanka Internet Service Ltd Sri Lanka Telecom ITMIN Internet Service Ltd Pan Lanka Networking (pvt) Ltd Ceycom Global Communications Ltd Eureka Online

28. End Show Intranet A privately maintained computer network that can be accessed only by authorized persons especially members or employees of the organization that owns it. Eg: Network among branches of a Bank Network among all schools, Zone, Province and MOE

29. End Show Intranet