Shaqra University College of Computing and Information Technology

1. Shaqra University College of Computing and Information Technology NETWORK 1: IT 202 TURKEA ALJUAID Email:taljuaid@su.edu.sa • Office :third floor room 351

2. Chapter 1: • Introduction to Networking

3. 1.1 DATA COMMUNICATIONS The term telecommunication means communication at a distance . The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Topics discussed in this section: • Components of a data communications system • Data Flow

4. Figure 1.1 Components of a data communication system Protocol: is a set of rules that governs data communications. It represents an agreement between the communicating devices. Without a protocol two devices may be connected but not communicating. 4

5. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

6. Directionofdataflow 1. Simplex: communication is unidirectional. (one-way-street). Only one of the two devices on a link can transmit; the other can only receive Ex: AsKeyboard(onlyinput) andmonitorsonly (output) 10

7. Directionof data flow 2. Half duplex: Each station can both transmit and receive , but not at the same time. When one device is sending the other can receive and vice versa. one- lane road with two direction).

8. Directionof data flow 3.Full-Duplex: Bothstationscantransmitand receivesimultaneously.(telephonenetwork) Like twoway streetwithtrafficflowingin both directionsatthesametime. • Signals going in either direction share the capacity of the link in two • ways: • Either the link must contain two physically separate transmission paths one for sending and other for receiving. • Capacity of the channel is divided between signals traveling in both direction

9. 1-2 NETWORKS A network is a set of devices (often referred to as. nodes) connected by communication links. 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. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information Topics discussed in this section: • Network Criteria • Physical Structures • Categories of Networks

10. Network Criteria • Performance : • Depends on Network Elements • Measured in terms of Delay and Throughput • Reliability • Failure rate of network components • Measured in terms of availability/robustness • Security • Data protection against corruption/loss of data due to: • Errors • Malicious users

11. Physical Structures • Type of Connection • Point to Point - single transmitter and receiver • Multipoint - multiple recipients of single transmission • Physical Topology • Connection of devices • Type of transmission • - unicast, mulitcast, broadcast

12. 1. Point –to-point Dedicated link between two devices. Most of them uses an actual length of wire or cable to connect the two ends but other options ,such as microwave satellite are possible. changeT.Vchannelby infraredremote control is point-to-pointconnection

13. 2. Multipoint (multidrop) connection: more than two devices share a single line. The capacity is shared either spatially or temporally. Spatially: Several devices can use link simultaneously Temporally: Users take turns , it is a time shared

14. Figure 1.3 Types of connections: point-to-point and multipoint

15. 1.6 NETWORKS Topology : • Physical topologies describe how the cables are run. • Logical topologies describe how the network messages travel. • Each topology is suited to specific tasks and has its own advantages and disadvantages.

16. Figure 1.4 Categories of topology

17. Network topology (cont.) Mesh • The mesh topology is the simplest logical topology in terms of data flow, but it is the most complex in terms of physical design. • In this physical topology, each device is connected to every other device • This topology is rarely found in LANs, mainly because of the complexity of the cabling. • If there are x computers, there will be (x * (x–1)) ÷ 2 cables in the network. For example, if you have five computers in a mesh network, it will use( 5 × (5 – 1) )÷ 2, which equals 10 cables. This complexity is increased when you add another workstation.

18. Figure 1.5 A fully connected mesh topology (five devices)

19. Meshtopology • Advantages: • With a logical mesh topology, however, there will always be a way of getting the data from source to destination. • It may not be able to take the direct route, but it can take an alternate, indirect route. • It is for this reason that the mesh topology is still found in WANs to connect multiple sites across WAN links. • It uses devices called routers to search multiple routes through the mesh and determine the best path. 20

20. Mesh topology • Disadvantages : • Related to the amount of cabling devices and the amount of I/O ports • required: • Every device must be connected to every other device, installation • and reconnection are difficult. • The sheer bulk of the wiring can be greater than the available space can accommodate.

21. Startopology Each device has a dedicated point-to-point link only to a central controller (hub) Unlike a mesh , a star topology does not allow direct traffic between devices, if one device want to send data to another , it send it to the hub, which send it to other device Figure 1.6 A star topology connecting four stations

22. Startopology • Advantages: • Easyto installand reconfigureand lessexpensive • eachdeviceneedonlyonelinkandI/Oporttoconnectit • toanyotherdevices.) • Robustness: • ifonelink fails,onlythatlink affectedandotherlinks • remainactive. • 3. Easy to connect new node or device. • Disadvantages: • Thedependencyofthe wholetopologyon onesinglepoint,thehub. • Ifthe hubgoesdown, the whole system isdead.

23. Bus Topology : • A bus is the simplest physical topology. • It consists of a single cable that runs to every workstation • This topology uses the least amount of cabling, but also covers the shortest amount of distance. ) • Each computer shares the same data and address path. With a logical bus topology, messages pass through the trunk, and each workstation checks to see if the message is addressed to itself. • If the address of the message matches the workstation’s address, the network adapter copies the message to the card’s on-board memory.

24. Figure 1.7 A bus topology connecting three stations As a signal travels along the backbone, some of its energy is transformed into heat, therefore, it becomes weaker and weaker as it has travel farther and farther

25. Advantage and Disadvantage of bus Topology :Advantage:Easy of insulation, use less cabling than mesh or starDisadvantage • it is difficult to add a workstation • if any one of the cables breaks, the entire network is disrupted. Therefore, it is very expensive to maintain. • Potential for congestion with network traffic

26. Ring topology • Each device has a dedicated point-to-point connection only with the two devices on either side of it • A signal is passed along the ring in one direction from device until it reaches its destination. • Each device in the ring incorporate as repeater • Repeater :regenerates the signal • it receives a weakened signal, creates a copy, bit for bit, at the original strength Figure 1.8 A ring topology connecting six stations

27. Ring topology • Advantages: • Easy to install and reconfigure. • Each device is linked only to its immediate neighbors. To add or delete a device requires hanging only 2 connections •  Additional components do not affect the performance of network. • Even when the load on the network increases, its performance is better than that of Bus topology.Disadvantages: • Unidirectional traffic. • A break in the ring (such as disabled station) can disable • the entire network. This can be solved by use dual ring

28. Figure 1.9 A hybrid topology: a star backbone with three bus networks

29. Categories of Networks • Local Area Networks (LANs) • Short distances • Designed to provide local interconnectivity • Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus • Wide Area Networks (WANs) • Long distances • Provide connectivity over large areas

30. Privately owned and links the devices in a single office, building or campus Local aria network (LAN) : • LANs designed to allow resources to be shared between PCs or workstations. The resources may be H.W (e.g. printer) or S.W( applications program) or data. • In LANs one of the computers has a large capacity drive and becomes a • server to other clients. • S/W stored on server and used as needed by the whole group. • LAN size determined by licensing restrictions( No of users per copy of S/W) • LAN use only one type of transmission medium. • The most common LAN topologies are bus, ring and star. • Traditionally LAN have data rates in the 4 to 16 Mbps. Today Speed can reach to 100Mbps or 1000MBps(1G).

31. MAN (metropolitan) : • Owned by private company or it may be a service provided by public company ( such as local tel.-company) • Extended over an entire city. • May be single network such as a cable television network, or it may be connected number of LANs into a large network so that resources may be shared LAN-TO- LAN. • Examples: • Company can use MAN to connect the LANs in all its offices throughout the city. • •A part of the telephone line network that can provide • DSL line to the customer

32. Wide Area Networks (WANs) : Provides long distance transmission of data, voice , image and video information over large areas ( country or whole world) In contrast to LAN, WAN may utilize public or private communication equipment or combination

33. Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet

34. Figure 1.11 WANs: a switched WAN and a point-to-point WAN

35. Figure 1.12 A heterogeneous network made of four WANs and two LANs

36. 1-3 THE INTERNET The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. Topics discussed in this section: Organization of the Internet Internet Service Providers (ISPs)

37. Figure 1.13 Hierarchical organization of the Internet

38. Standers organization : • InternationalOrganizationforStandardization(ISO) • InternationalTelecommunication UnionTelecommunication • standardsector( ITU-T) • Instituteof Electricaland ElectronicsEngineers (IEEE)

39. 1-4 PROTOCOLS A protocol is synonymous with rule. It consists of a set of rules that govern data communications. It determines what is communicated, how it is communicated and when it is communicated. The key elements of a protocol are syntax, semantics and timing Topics discussed in this section: • Syntax • Semantics • Timing

40. Elements of a Protocol: • Syntax • Structure or format of the data • Indicates how to read the bits - field delineation • Semantics • Interprets the meaning of the bits • Knows which fields define what action • Timing • When data should be sent and what • Speed at which data should be sent or speed at which it is being received.

41. Questions