1. Computer Science 502 Objectives and Main Areas of Coverage

2. Basic Concepts OSI Analysis of Networks Client-servers

3. Basic Concepts

4. I told you before! I didn’t understand. Communication is fundamentally complicated. transmitter receiver MEDIUM

5. Consider the Problems of Human Communication Computers Have Many of the Same Problems! Receiver is unable to understand the message Transmitter speaks when receiver not ready Receiver doesn’t understand the message –not the type of message expected –not the right language –speaks too fast/slow etc.

6. Principles Apply At Many Levels CPU Memory Video Card Sound Card (Main Bus) On a computer motherboard Main Memory Disk Drive

7. Between Devices on a computer

8. Between computers on a network

9. Between Computers on Different Networks

10. Distinguishing Problems 1. Direct Communication Person to Person Computer to Computer (serial cable) 2. Network Communication Two Machines Interconnected with others 3. InterNetwork Communication Networks Connected

11. What are the problems to address? 1. Is the other computer ready? 2. How does it know I’m sending data? 3. How does it know the begin/end of my message? 4. What if an error occurs? 5. How does the other computer know? 6. What if I send too fast? 7. How do I know when the other computer recovers? NONE ARE NETWORKING PROBLEMS

12. How Does it Know Which One? A Network Concern! ACB

13. A C B D FE How Do We Know If It Is On THIS Network? An INTERNetworking Problem!

14. Basic Principles Synchronization (beginning and ending) Timing (rates of transmission / flow control) Encoding Error detection and correction Identification Routing Efficiency

15. Complexity of Material Those without experience are NOT at a serious disadvantage No single element is overwhelming Proper integration of components is extremely difficult A framework for building an understanding is critical like a foundation for building a house

16. Principles Repeat Many issues occur in a number of places Understanding it once can be leveraged into the understanding of numerous features Keep these issues at the forefront of learning Many of your experiences will be similar but the wrong one. Be careful. Ask questions. OSI model is not only a tool for design but a tool for organizing understanding

17. OSI Model

18. What is the OSI model? A framework for design presented by International Standards Organization (ISO) A classical study of layered design A framework for LEARNING how the process of computer communication works Ultimate objective is to let any two PROGRAMS on any two COMPUTERS in the world talk to one another.

19. Evaluating Network Performance

20. Performance Evaluation of network performance has two foci –Using mathematical tools/analysis to solve general problems Limited use of statistics and calculus –Using simulation tools to understand more complex problems Use of a network simulation software package Free to students Opnet Simulation will be a major project

21. Client Server Software

22. Developing Network Systems Significant % of current development is client–server based. How to develop clients and servers –Development with java/c++ –Major project Intro to other techniques –CGIs with php or javascript –J2EE and.NET