1 An Overview of ATM Signalling Carey Williamson University of Calgary

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

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

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

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 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 Example: ATM Signalling ATM Network

10 Example: ATM Signalling ATM Switch

11 Example: ATM Signalling UNI

12 Example: ATM Signalling UNI NNI

13 Example: ATM Signalling UNI NNI

14 Example 1: ATM Signalling CR CR: Connection Request

15 Example 1: ATM Signalling CR CR: Connection Request

16 Example 1: ATM Signalling CR CR: Connection Request

17 Example 1: ATM Signalling CR CR: Connection Request

18 Example 1: ATM Signalling CR CR: Connection Request

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

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

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

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

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

24 Example 2: ATM Signalling CR CR: Connection Request

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

26 Example 3: ATM Signalling CR CR: Connection Request

27 Example 3: ATM Signalling CR CR: Connection Request

28 Example 3: ATM Signalling CR CR: Connection Request

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

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

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

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 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)