This document contains figures and descriptions related to X.25, a protocol suite for packet switched wide area network (WAN) connections. It discusses the X.25 layers in relation to the OSI model, the format of frames and packets, how virtual circuits are established, and error control mechanisms like acknowledgements and retransmissions. Control packets like RR, RNR and REJ are used to manage data flow across virtual circuits between networked devices using X.25 addressing.

1. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Chapter 17
X.25

2. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-1
X.25

3. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-2
X.25 Layers in Relation to the OSI Layers

4. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-3
Format of a Frame

5. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-4
Addressing at the Frame Layer

6. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-5
Three Phases
of the
Frame Layer

7. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-6
Frame Layer and Packet Layer Domains

8. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-7
Virtual Circuits
in X.25

9. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-8
LCNs in X.25

10. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-9
LCN Assignments

11. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-10
PLP Packet Format

12. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-11
Categories of PLP Packets

13. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-12
Data Packets in the PLP Layer

14. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-13
RR, RNR, and REJ Packets

15. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-14
Other Control Packets

16. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-15
Control Packet Formats

17. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-16
X.25 Address Format

18. McGraw-Hill ©The McGraw-Hill Companies, Inc., 2001
Figure 17-17
Triple-X Protocols