ECOM 4314 Data Communications Fall September, 2010

1. ECOM 4314Data CommunicationsFall September, 2010

2. Instructor Eng. Wazen M. Shbair Department of Computer engineering , IUG Master degree in Computer engineering Research Scope: Network Security Email: wmshbair@iugaza.edu.ps Data Communication

3. Text Book • Data Communications and Networking, 4rdEdition, BehrouzA. Forouzan, McGraw-Hill, 2007. Data Communication

4. Grade Distribution Data Communication

5. Lecture #1 Outline • Overview • Data Communications • Networks • Protocols and Standards. Data Communication

6. Overview • Data communications and networking are changing the way we do business and the way we live. • Businesses and all aspects of live today rely on computer networks and internetworks. Data Communication

7. Data Communications • When we communicate, we are sharing information either locally or remotely. • The term telecommunication, which includes telephony, telegraphy, and television, means communication at a distance (tele is Greek for "far"). • The word Data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data Communication

8. Data Communications Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Data Communication

9. Data Communications • The effectiveness of a data communications characteristics: delivery, accuracy, timeliness, and jitter. • Delivery : The system must deliver data to the correct destination. • Accuracy: The system must deliver the data accurately • Timeliness: The system must deliver data in a timely manner. • Jitter: it refers to the variation in the packet arrival time. (It is the uneven delay in the delivery of audio or video packets) Data Communication

10. Data Communications Components • A data communications system has five components • Message • Sender • Receiver • Transmission media • Protocol Data Communication

11. Data Representation • Information today comes in different forms such as text, numbers, images, audio, and video. • Information is represented as a bit pattern, a sequence of bits (0s or 1s) Data Communication

12. Data Flow (Transmission mode) • Communication between two devices can be simplex, half-duplex, or full-duplex. Data Communication

13. Network • A network is a set of devices (often referred to as nodes) connected by communication links. Data Communication

14. Network Criteria • A network must be able to meet a certain number of criteria such as: • Performance • Reliability • Security. Data Communication

15. Performance • Performance can be measured in many ways, including transit time and response time. • Transit time is the amount of time required for a message to travel from one device to another. • Response time is the elapsed time between an inquiry and a response. • The performance of a network depends on the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software. Data Communication

16. Performance • Performance is often evaluated by two networking metrics: throughput and delay. • We often need more throughput and less delay. • The throughput is then calculated by dividing the file size by the time Data Communication

17. Reliability • Network reliability is measured by • The frequency of failure • The time it takes a link to recover from a failure. • The network's robustness in a catastrophe. Data Communication

18. Security • Network security issues include: • Protecting data from unauthorized access • Protecting data from damage and development • Implementing policies and procedures for recovery from breaches and data losses. Data Communication

19. Network Physical Structures • A network is two or more devices connected through links. A link is a communications pathway that transfers data from one device to another. • There are two possible types of connections: point-to-point and multipoint. Data Communication

20. Point-to-Point • A point-to-point connection provides a dedicated link between two devices. • The entire capacity of the link is reserved for transmission between those two devices. Data Communication

21. Multipoint • Multipoint connection is one in which more • than two specific devices share a single link • When a message is sent every device on the network “hears” it but only the intended recipient “listens” to it. • All nodes must “fight” for their turn to speak (connection) or wait to be granted a turn. Data Communication

22. Physical Topology • The term physical topology refers to the way in which a network is laid out physically. • The topology of a network is the geometric representation of the relationship of all the links and linking devices to one another. • 2 or more devices connected to a link • 2 or more links form a topology • Basic topologies Mesh, Star, Tree, Bus, Ring ,Hybrid Data Communication

23. Mesh Topology • Each device has a dedicated point-to-point link. • The term dedicated means that the link carries traffic only between the two devices it connects. • A fully connected mesh network with n devices has n(n-1)/2. • Each network device must have (n-1) I/O ports Data Communication

24. Mesh Topology • Advantages • High throughputeach connection can carry its own data load, thus eliminating the traffic problems that can occur when links must be shared by multiple devices. • RobustIf one link becomes unusable, it does not incapacitate the entire system • High SecurityWhen every message travels along a dedicated line, only the intended recipient sees it. • Simple fault identification and isolation Data Communication

25. Mesh Topology • Disadvantages • Number of cables –space & cost ( material, install.) • Number of I/O ports • Difficult to reconfigure • One practical example of a mesh topology is the connection of telephone regional offices in which each regional office needs to be connected to every other regional office. Data Communication

26. Star Topology • In a star topology, each device has a dedicated point-to-point link only to a central controller, usually called a hub. • a star topology does not allow direct traffic between devices. The controller acts as an exchange Data Communication

27. Star Topology • Advantages • Less expensive (cable) than Mesh • One I/ O port • Easy to install and reconfigure • Robust • Easy to cope with fault • Disadvantages • More cabling used than for other topologies(such as ring or bus) • Hub failure disables entire network • Usage • Ethernet Data Communication

28. Bus Topology • A bus topology is one long cable acts as a backbone to link all the devices in a network. Data Communication

29. Bus Topology • Advantages • Easy to install • Less cable compare to other topologies • Failure of any device does not shut network down • Disadvantages • Limited backbone length, number & distance between taps • Backbone failure causes complete network failure • Fault isolation difficult Data Communication

30. Ring Topology • In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it. Data Communication

31. Performance • A signal is passed along the ring in one direction, from device to device, until it reaches its destination. • Each device in the ring incorporates a repeater. When a device receives a signal intended for another device, its repeater regenerates the bits and passes them along Data Communication

32. Performance • Advantages • Easy to install • Easy to cope with fault • Disadvantages • Not robust Data Communication

33. Hybrid Topologies • Larger networks often combine several topologies connected via central hub or backbone. Data Communication

34. Categories of Networks • Three categories of Networks • Local Area Network (LAN) limited to a few kilometers • Metropolitan Area Network (MAN) tens of miles • Wide Area Network (WAN) worldwide. Data Communication

35. Local Area Network (LAN) • A local area network (LAN) is usually privately owned and links the devices in a single • office, building, or campus . • a LAN can be as simple as two PCs and a printer in someone's home office. Data Communication

36. Metropolitan Area Networks • A metropolitan area network (MAN) is a network with a size between a LAN and a WAN. • It normally covers the area inside a town or a city. • Mainly used for interconnecting private LANs located at different areas to each other • Normally owned and operated by someone else: an independent or government service provider Data Communication

37. Wide Area Network • A wide area network (WAN) provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world. Data Communication

38. Internetworks • Network of networks • Connection via interconnecting devices (Routers & Gateway) Data Communication

39. Protocol Definition • A set of rules for communication • Need to be agreed on both sender and receiver Data Communication

40. Protocol Elements • Syntax • Structure or format of data • Frame Format: Destination Add, Source Add, Data • Semantics • Meaning and action • Does this Address belong to me? • Timing • When & How fast Data Communication

41. References • Ayman, Maliha, “Data Communication Lectures”, IUG. • BehrouzA. Forouzan , “Data Communications and Networking”, 4rdEdition, Chapter2, 2007 Data Communication

42. Thanks Data Communication