1. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Chapter 19 TELNET and Rlogin

2. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CONTENTS CONCEPT NETWORK VIRTUAL TERMINAL (NVT) NVT CHARACTER SET EMBEDDING OPTIONS OPTION NEGOTIATION SUBOPTION NEGOTIATION CONTROLLING THE SERVER OUT-OF-BAND SIGNALING

3. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CONTENTS (Continued) ESCAPE CHARACTER MODE OF OPERATION EXAMPLES USER INTERFACE RLOGIN (REMOTE LOGIN) SECURITY ISSUE

4. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 TELNET and Rlogin are general-purpose client-server application programs.

5. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CONCEPT 19.1

6. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-1 Local login

7. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-2 Remote login

8. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 NETWORK VIRTUAL TERMINAL 19.2

9. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-3 NVT

10. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 NVT CHARACTER SET 19.3

11. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-4 Format of data characters

12. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-5 Format of control characters

13. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 EMBEDDING 19.4

14. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-6 Embedding

15. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 OPTIONS 19.5

16. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 OPTION NEGOTIATION 19.6

17. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-7 Offer to enable

18. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-8 Request to enable

19. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-9 Offer to disable

20. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-10 Request to disable

21. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-11 Echo option example

22. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 SUBOPTION NEGOTIATION 19.7

23. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-12 Example of suboption negotiation

24. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 CONTROLLING THE SERVER 19.8

25. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-13 Example of interrupting an application program

26. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 OUT-OF-BAND SIGNALING 19.9

27. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-14 Out-of-band signaling

28. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 ESCAPE CHARACTER 19.10

29. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-15 Two different interruptions

30. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 MODE OF OPERATION 19.11

31. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 EXAMPLES 19.12

32. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Example 1 In this example, we use the default mode to show the concept and its deficiencies even though it is almost obsolete today. The client and the server negotiate the terminal type and terminal speed and then the server checks the login and password of the user. See Figure 19.16.

33. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-16 Example1

34. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Example 2 In this example, we show how the client switches to the character mode. This requires that the client request the server to enable the SUPPRESS GO AHEAD and ECHO options. See Figure 19.17.

35. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-17 Example 2

36. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 USER INTERFACE 19.13

37. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 RLOGIN (REMOTE LOGIN) 19.14

38. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 The Rlogin process uses the TCP port 513.

39. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-18 Connection establishment

40. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 19-19 Sending ss command from the client to the server

41. McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 SECURITY ISSUE 19.15