INTRODUCTION TO COMPUTER NETWORKS

1. Introduction to Computer Networks INTRODUCTION TO COMPUTER NETWORKS SANA AHMED (2)

2. Introduction to Computer Networks Computer Networks • Computer network connects two or more autonomous computers. • The computers can be geographically located anywhere.

3. Introduction to Computer Networks Network Topology • The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.

4. Introduction to Computer Networks Bus Topology • Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable. Drop Line Tap Terminator Drop line: connection between node and main cable via tap. Tap: connector between drop line and main cable. Terminator: to prevent bouncing.

5. Bus Topology cont. • Multipoint. • One long cable ,connect all nodes in network. • Access method : Broadcast. • All computer have a copy from a message but only the receiver (sent to) can open the message. • If the cable was cutoff or failure , all network is down,. • This topology uses less cabling. • Easy to add nodes.

6. Introduction to Computer Networks Star & Tree Topology • The star topology is the most commonly used architecture in Ethernet LANs. • When installed, the star topology resembles spokes in a bicycle wheel. • Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.

7. Star Topology cont. • All nodes in network connected point-to-point link with central controller . • In star topology, each node need one link and one port to connect with network. • All network depend on the controller, if the controller goes down , all network is dead.

8. Introduction to Computer Networks Ring Topology • A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. • The frame then continues around the ring until it finds the destination node, which takes the data out of the frame. • Single ring – All the devices on the network share a single cable • Dual ring – The dual ring topology allows data to be sent in both directions.

9. Ring Topology cont. • Every node connected point-to-point with two node. • The signal is passed on one direction. • Not all node have the same copy of the message. • The message sent by the sender and the message turns to give destination • To speed up the network we add another ring. • When a ring break , all network is dead.

10. Introduction to Computer Networks Mesh Topology • The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. • It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. • Implementing the mesh topology is expensive and difficult.

11. Mesh Topology cont. • Every node has dedicated point-to-point link with all node in network. • Every node must have n-1 port. N: no. of nodes in network • No. of link in any mesh network = N(N-1)/2 • Mesh topology service security and privacy. • More expensive. • Ex: design mesh topology for 6 nodes?

12. Introduction to Computer Networks Network Components • Physical Media • Interconnecting Devices • Computers • Networking Software • Applications

13. Transmission Media • A transmission media define as anything that can carry information from a source to a destination.

14. Transmission Media cont.

15. Guided Media

16. Coaxial Cable (coax)

17. Coaxial Cable (coax) • Two kinds: • Thicknet(RG-11): it connect 100 devices with range 500 m (more expensive ). • Thinnet (RG-58): it connect 30 devices within 185 m (cheaper). • To connect coaxial cable to device, we need (BNC). Carries signals of higher frequency ranges than twisted-pair cable.

18. Thinnet Ref: http://www.ussg.iu.edu/usail/external/ethernet/ethernet-guide.html

19. Twisted-Pair Cable 100 m, more flexible, cheap, installation doesn’t need experience.

20. Twisted Pair cable • Two or more pairs of single conductor wires that have been twisted around each other. • Twisted pair cable is classified by category. Twisted pair cable is currently Category 1 through Category 6. • Twisting the cables helps to eliminate electromagnetic interference between the two wires. • Shielding can further help to eliminate interference.

21. 1303330 Data Communication & Computer Network

22. Shielded Twisted Pair (STP) More difficult to install and more expensive but less susceptible to noise.

23. Unshielded Twisted-Pair (UTP) RJ45 connector To connect twisted pair cable to device we need RJ45 connector

24. Connector RJ-45 BNC

25. Fiber Optics cable

26. Fiber Optics cable • Single-mode fiber • Carries light pulses along single path. • Multimode fiber • Many pulses of light travel at different angles

27. Fiber Optics cable cont. Advantage: noise resistance, less attenuation, and higher bandwidth. Disadvantage: cost, installation/maintenance, and fragility.

28. Fiber Optics cable cont. • Two popular connectors used with fiber-optic cable: • ST connectors • SC connectors Other Connector Types: FC, MT-RJ, FDDI

29. Categories of 10-Mbps, Ethernet 1303330 Data Communication & Computer Network

30. Unguided Media Transport electromagnetic waves without using a physical conductor (wireless communication). 3 KHz 300 GHz 400 GHz 900 GHz

31. Unguided Media • Radio, satellite microwave,, Bluetooth, and infrared light are all different forms of electromagnetic waves that are used to transmit data.

32. Unguided signal can travel from the source to destination in several ways: 1.Ground Propagation: • Radio waves travel through the lowest portion of the atmosphere, hugging the earth. • The low frequency signal follow the curvature of the planet. • Distance depends on the amount of the power.

33. Cont. 2.Sky Propagation: • Higher frequency radio radiate upward into the ionosphere where they are reflected back to the earth. • Sky propagation allow for greater distance with lower power output.

34. Cont. 3.line-of-sight Propagation: Very high frequency signals are transmitted in straight lines directly from antenna to antenna.

35. Wireless Communication

36. Radio Waves • Between 3 KHz – 1 GHz. • Omnidirectional (many direction). • Radio waves use omnidirectional antenna. • Radio waves used for multicast communication, such as radio and television. • Sky Propagation.

37. Microwave • Between 1 GHz- 300 GHz. • Unidirectional. • Microwave use Unidirectional antenna. • Microwave used for unicast communication, such as cellular telephone ,wireless LAN and satellite. • Line-of-sight propagation.

38. Infrared Transmissions • Between 300 GHz-400 THz • Used for short-range communication. • Very common with remote control devices, but can also be used for device-to-device transfers, such as PDA to computer. • Line-of-sight propagation.

39. Introduction to Computer Networks Computers: Clients and Servers • In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. • The server contains the file, print, application, security, and other services in a central computer that is continuously available to respondto client requests.

40. Introduction to Computer Networks Applications • E-mail • Searchable Data (Web Sites) • E-Commerce • News Groups • Internet Telephony (VoIP) • Video Conferencing • Chat Groups • Instant Messengers • Internet Radio