1. Open Systems and Data Link Protocols November 7, 2002

2. Announcements Short Test or Long Quiz: November 21 –Will cover Chapters 14, 15 and 16. Homework –Chapter 14: 3, 4, 6, 12, 22, 26 (hand in next week) –Chapter 15: 4, 5, 6, 7, 16, 17, 26, 27, 40 (hand in November 21) –Read Chapter 16 (pages 475-502) Internet- ATM. It will not be discussed in class but the quiz bonus test will come from it.

3. Class Objectives Open Systems –Why do we need open standards? –Seven-layer OSI model Data Link Protocols –The past: BISYNC –The present: HDLC

4. Before Open Standards Getting two systems to communicate between them was a major effort. Once you purchased a system you were “stuck” with it for years for both hardware and software: –IBM –Digital –Unisys

5. With Open Systems System interoperability becomes much easier. Allows the combination of different hardware and software “solutions”. Results: –Lower costs due to increased competition –Faster implementation (alternate sources) –Easier system maintenance and troubleshooting

6. FIGURE 14-1 Seven-layer OSI model. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

7. OSI Layers 1. Physical: Concerned with the transmission of unstructured bit stream over physical medium; deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium. 2. Data Link: Provides for the reliable transfer of information across the physical link; sends blocks of data (frames) with the necessary synchronization, error control, and flow control.

8. OSI Layers (cont.) 3. Network: Provides upper layers with independence from the data transmission and switching technologies used to connect systems; responsible for establishing, maintaining, and terminating connections. 4.Transport: Provides reliable, transparent transfer of data between points; provides end-to-end error recovery and flow control.

9. OSI Layers 5. Session: Provides the control structure for communications between applications; establishes, manages, and terminates connections (sessions) between cooperating applications. 6. Presentation: Provides independence to the application processes from differences in data representation (syntax). 7. Application: Provides access to the OSI environment for users and also provides distributed information services.

10. FIGURE 14-2 (a) Computers connected point-to-point; (b) computer connected to several terminals in a multipoint (or multidrop) configuration. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

11. BISYNC Developed by IBM in 1964 Byte or character oriented protocol Geared toward mainframe-terminal relationship Half-Duplex operation Use has been in decline due to better protocols

12. FIGURE 14-3 BISYNC message block format. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

13. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

14. FIGURE 14-4 BISYNC transparent text mode format. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

15. FIGURE 14-5 BISYNC point-to-point line control sequence. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

16. FIGURE 14-6 An error condition encountered causes the receiving station to request a retransmission. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

17. FIGURE 14-7 Acknowledgment, ACK, lost en route to the transmitting station. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

18. FIGURE 14-8 Host computer poll and selecting a device for transmitting data in a multipoint setup. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

19. FIGURE 14-10 Circuit switching network. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

20. FIGURE 14-11 Message switching network. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

21. FIGURE 14-12 Packet switching network. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

22. High-Level Data Link Control Bit-oriented protocol Used throughout the world Implemented in X.25 packet switching networks Full-duplex operation Flexible –Point-to-point and multi-point links –Primary-secondary and peer-to-peer interaction. –Works with long distance (e.g. satellite) as well as short distance links.

23. FIGURE 14-13 HDLC frame format. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

24. FIGURE 14-14 HDLC framing pattern and bit order of transmission. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

25. FIGURE 14-15 Extending the HDLC ADDRESS BYTE field. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

26. FIGURE 14-16 Format of CONTROL BYTE for information transfer, supervisory, and unnumbered HDLC frames. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

27. FIGURE 14-18 HDLC supervisory frame structure. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

28. FIGURE 14-19 HDLC unnumbered frame structure. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

29. FIGURE 14-20 Zero-bit insertion range. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

30. FIGURE 14-21 HDLC zero-bit insertion, bit-stuffing technique. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

31. FIGURE 14-22 HDLC frame sequencing. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.