1. 1 An Overview of ATM Signalling Carey Williamson University of Calgary

2. 2 Introduction n ATM is a connection-oriented protocol, which means that virtual channels must be set up before any data cells can be sent on the channel n Connection setup is done using a signalling protocol

3. 3 ATM Signalling Protocol n Protocol consists of two parts n User-Network Interface (UNI) defines how hosts talk to switchesdefines how hosts talk to switches n Network-Network Interface (NNI) defines how switches talk to other switchesdefines how switches talk to other switches n Cell formats slightly different

4. 4 ATM UNI Cell Format GFCVPI Payload (48 bytes) VPIVCI HEC PTCLPVCIRES

5. 5 ATM NNI Cell Format VPI Payload (48 bytes) VPIVCI HEC PTCLPVCIRES

6. 6 ATM NNI Cell Format VPI Payload (48 bytes) VPIVCI HEC PTCLPVCIRES

7. 7 Basic Signalling Operation n Connection requests proceed hop- by-hop through the switches of the network en route to destination n Switches perform Call Admission Control (CAC) based on traffic descriptor, QOS requirements, and available resources at that switch

8. 8 Basic Operation (Cont’d) n If connection is acceptable, then request is forwarded on, otherwise “reject” is returned n If destination accepts connection, then “accept” is returned n VPI and VCI assigned

9. 9 Example: ATM Signalling ATM Network

10. 10 Example: ATM Signalling ATM Switch

11. 11 Example: ATM Signalling UNI

12. 12 Example: ATM Signalling UNI NNI

13. 13 Example: ATM Signalling UNI NNI

14. 14 Example 1: ATM Signalling CR CR: Connection Request

15. 15 Example 1: ATM Signalling CR CR: Connection Request

16. 16 Example 1: ATM Signalling CR CR: Connection Request

17. 17 Example 1: ATM Signalling CR CR: Connection Request

18. 18 Example 1: ATM Signalling CR CR: Connection Request

19. 19 Example 1: ATM Signalling CR CR: Connection Request OK : Connection Accept OK (VCI = 12)

20. 20 Example 1: ATM Signalling CR CR: Connection Request OK : Connection Accept OK (VCI = 12) (VCI = 4)

21. 21 Example 1: ATM Signalling CR CR: Connection Request OK : Connection Accept OK (VCI = 12) (VCI = 4) (VCI = 104)

22. 22 Example 1: ATM Signalling CR CR: Connection Request OK : Connection Accept OK (VCI = 12) (VCI = 4) (VCI = 104) (VCI = 4)

23. 23 Example 1: ATM Signalling CR CR: Connection Request OK : Connection Accept OK (VCI = 12) (VCI = 4) (VCI = 104) (VCI = 4) (VCI = 77)

24. 24 Example 2: ATM Signalling CR CR: Connection Request

25. 25 Example 2: ATM Signalling CR NO: Connection Reject NO CR: Connection Request

26. 26 Example 3: ATM Signalling CR CR: Connection Request

27. 27 Example 3: ATM Signalling CR CR: Connection Request

28. 28 Example 3: ATM Signalling CR CR: Connection Request

29. 29 Example 3: ATM Signalling CR CR: Connection Request NO NO: Connection Reject

30. 30 Example 3: ATM Signalling CR CR: Connection Request NO NO: Connection Reject

31. 31 Example 3: ATM Signalling CR CR: Connection Request NO NO: Connection Reject NO

32. 32 Summary n ATM UNI and NNI signalling specifications define the protocols for connection setup and teardown between ATM equipment (Version 4.0 soon) n Can support point to point and multipoint connections

33. 33 Where to get more information n ATM UNI 3.0 Specification (now obsolete!) n ATM Forum n Fore Systems SPANS protocol specification (Simple Protocol for ATM Network Signalling)