1. Data Communication and Networks Chapter 5

2. What’s a Network? a network consists of two or more computers that are connected together to share information The “Information Society” needs computers to exchange information The very high speed of exchanging information made the “Information Superhighway”

3. Why do we need a Network? Share resources Share software Share information Users communication Customer service

4. Network Types Networks can be classified according to: Geographical Distance Topology

5. Types of Networks according to their Geographical Distance LAN vs. WAN Peer-to-Peer LAN Client-Server LAN WAN

6. Switch (24 Ports) Hub Router Repeater Bridge WAN’s Hardware

7. Hub: has lots of ports to connect all WAN computers Switch: special Hub, transmits to destination directly Router: intelligent device, finds best path for transmission Bridge: connect two similar LANs Gateway: connect different LANs Repeater: strengthens signal by repeating it before re- transmitting it Multiplier: combine messages from different devices and sends them to destination via a very fast cable

8. Network Topologies Star Network Ring Network Bus Network

9. Star Networks A network in which all microcomputers and other communication devices are connected to a central hub Advantage is, the hub prevents collisions between messages Disadvantage is, if a connection is broken, the entire network stops working

10. Ring Networks A network in which all microcomputers and other communication devices are connect in a continuous loop Signals are passed around the ring until they reach the right destination Advantage is, signals flow only in one direction so there is no danger of collision Disadvantage is, if a connection is broken between any station, the rest of the devices on the network will not continue operating

11. Bus Networks More like a bus system at rush hours Various buses pausing in different bus zones to pick up passengers All communication devices are connected to a common channel (the bus) Advantage is, it maybe organized as a client/server or peer-to-peer network Disadvantage is, the extra circuitry and software are needed to avoid collisions between stations, and if the connection is broken then the entire network may stop working

12. Communication Hardware Modem  Used to transmit data in a digital format using a computer over an analog medium (the telephone network) Network Card  It’s a circuit that is plugged in a slot so that the computer can be connected to other computers Transmission media  Used to send data over the network

13. Wired Media Coaxial Cable Twisted Pairs Fiber Optics

14. Radio waves Microwaves Satellite Network Protocols It is a set of instructions and procedures that maintain and control transmission in networks i.e. the number of computers that can share the link, error correction, transmission speed Wireless Media

15. The Internet Biggest WAN Provides many services, most important: Search Engines and e-mail

16. More on Networks Intranet: a private network for a certain establishment Extranet: a private networks, that uses intranet technology, to provide access to information by customers. Firewall: set of related programs at a network, help to protect and organize access to information and resources over the network