1. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Overview of Data Communications and Networking UNIT I UNIT I

2. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.1 Data Communication Components Data Representation Direction of Data Flow

3. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.3 1-1 DATA COMMUNICATIONS Where are the data communications? Why data communications? Telecommunication: communication at a distance. Data: information presented in whatever form is agreed upon by the parties creating and using the data. Data communications: the exchange of data between two devices via some form of transmission medium such as a wire cable.

4. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.4  What do we need? Hardware Software  Four fundamental characteristics: 1. Delivery: correct destination 2. Accuracy: correct data 3. Timeliness: fast enough 4. Jitter: uneven delay  Topics covered: 1. Components 2. Data representation 3. Data flow 1-1 DATA COMMUNICATIONS

5. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.1 Five components of data communication

6. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.6 DATA REPRESENTATION  Text Email, articles, etc Coding (Unicode, ASCII)  Numbers Direct conversion  Images Pixels, resolution, gray scale, RGB, YCM  Audio Continuous, signal conversion  Video Movie, continuous/discrete

7. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.7 Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) DIRECTION OF DATA FLOW

8. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.13 LAN

9. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.13 LAN (Continued)

10. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.14 MAN

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.15 WAN

12. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 TYPES OF CONNECTION  POINT TO POINT  MULTIPOINT

13. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.5 Point-to-point connection

14. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.6 Multipoint connection

15. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.7 Categories of topology The way network is connected either physically or logically. Topology

16. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.16 Mesh Figure 1.5 A fully connected mesh topology (five devices) 1 2 3 4 5 Example: telephone regional offices Advantages: no traffic problems Robust. No link failure no effect on others. Privacy security Easy to detect the abnormal situation. Disadvantages: Amount of cables, i/o ports Efficiency and effectiveness Space Cost

17. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.9 Star topology Each node is connected to a device in the center of the network called a hub. The hub simply passes the signal arriving from any node to the other nodes in the network. The hub does not route the data.

18. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.18 Star Figure 1.6 A star topology connecting four stations Less expensive. One link and I/o port connecting to the hub. No direct traffic between two devices. Advantages: Easy to install Less cables Maintain: add, move, delete Robustness Disadvantages; Hub is too important The hub represents a single source of failure

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.19 Bus Figure 1.7 A bus topology connecting three stations Multipoint Advantages: Easy to install Less cables Disadvantages: Hard to detect fault isolation. Bus cable is too important Each node is connected one after the other (like christmas lights) Nodes communicate with each other along the same path called the backbone

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.20 Ring Figure 1.8 A ring topology connecting six stations Point to point with 2 devices on both sides Advantages: Easy to install Maintain: add move delete Fault isolation Disadvantages: Unidirectional traffic The ring network is like a bus network, but the “end” of the network is connected to the first node Nodes in the network use tokens to communicate with each other

21. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Figure 1.10 Bus topology

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.22 Figure 1.8 A ring topology connecting six stations

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.23 Figure 1.9 A hybrid topology: a star backbone with three bus networks

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 1.4 Protocols and Standards Protocols Standards Standards Organizations Internet Standards

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004  Protocols (rules) 1. Why do we need protocols? 2. Key elements of protocols a) Syntax: structure or format of the data b) Semantics : meaning of each section of bits c) Timing: when sent and how fast  Standards 1. De facto vs. De jure 2. Organizations 3. Internet standards (Internet draft & RFC) Protocols and standard

26. McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 National Standards Organizations (Generally responsible for standards within a nation and usually participate in that nation’s international activity) American National Standards Institute (ANSI) International Standards Organizations (Promote standards for worldwide use) International Standards Organization (ISO) International Telecommunications Union (ITU)consists of ITU-T, which is responsible for communications, interfaces, and other standards related to telecommunications. Electronic Industries Association (EIA) Institute for Electrical and Electronics Engineers (IEEE) Internet Engineering Task Force (IETF)