1. 1 Copyright © Monash University ATM Signalling Philip Branch Centre for Telecommunications and Information Engineering (CTIE) Monash University http://www.anspag.monash.edu.au/~pbranch/masters.ppt

2. 2 Copyright © Monash University Signalling Overview Description of Signalling Signalling between the User and Network Signalling within Private ATM Networks Signalling between ATM networks

3. 3 Copyright © Monash University What is Signalling? Call and Connection Control Means by which calls are –established, maintained, terminated In Channel Signalling –in and out of band Common Channel Signalling –One shared, dedicated signalling channel –N-ISDN and ATM

4. 4 Copyright © Monash University Requirements of ATM Signalling Establish connection –Routing –Quality of Service –Point to point, multipoint Clear connection Status information

5. 5 Copyright © Monash University Establishment of a Connection Find destination node Determine path through network Establish connection between each node

6. 6 Copyright © Monash University Signalling Standards User-Network Interface –UNI 3.0, UNI 3.1, UNI 4.0 –Q.93B, Q.2931 –ILMI Network to Network Interface –IISP, P-NNI, IPNNI, AINI, BICI, B-ISUP Other important standards –LANE, MPOA

7. 7 Copyright © Monash University ATM Signalling Standards Evolution Q.931 - Q.93B - UNI 3.0 Q.931 - Q.2931 - UNI 3.1 Q.931 - Q.2931 - UNI 4.0 Q.931 - Q.2931 - IISP - PNNI

8. 8 Copyright © Monash University Signalling within Private ATM Networks Private and public network standards ATM Forum, ITU-T main standards bodies Connection of CPE to network Connection across the network Passing of reachability information between switches

9. 9 Copyright © Monash University ATM Addressing Two formats –OSI NSAP for private networks –E.164 for public networks (ISDN numbers) Format –Network part –User part Network part hierarchical structure User part similar to Ethernet MAC address

10. 10 Copyright © Monash University ILMI and Addressing Interim Local Management Interface Specification Management plane of ATM protocol stack Built around SNMP Management Information Base Monitoring and Control across the UNI Key function is address registration

11. 11 Copyright © Monash University User-Network Interface Access Signalling Connection between CPE and network UNI 3.0, 3.1, 4.0 Q.2931

12. 12 Copyright © Monash University UNI 3.1 ATM Forum Standard Similar to N-ISDN Q.931 Signalling between CPE and network Specify point to point and multipoint Signalling ATM Adaptation Layer Signalling over PVC –VPI = 0, VCI = 5

13. 13 Copyright © Monash University Signalling Protocol Stack UNI, UNI SSCF, SSCOP Q.2110, AAL5

14. 14 Copyright © Monash University UNI 3.1 Signalling Messages Fewer messages than Q.931 Call establishment –setup, proceeding, connect, connect acknowledge Call Clearing –release, relase complete Status –status, status enquiry

15. 15 Copyright © Monash University SETUP Signalling Message Similar to SETUP in N-ISDN Q.931 Additional functions in SETUP –AAL type –Bearer (CBR, VBR-nrt, Unkown) –ATM traffic descriptor –QoS parameter

16. 16 Copyright © Monash University Traffic Descriptor in SETUP Forward and backwards traffic CLP priorities Token Bucket Parameters –Peak Cell Rate –Sustainable Cell Rate –Maximum Burst Size

17. 17 Copyright © Monash University Quality of Service Parameter Predefined in 3.1 Parameterised in 4.0 Parameters –Cell Loss Ratio –Maximum Cell Delay Time –Maximum Cell Delay Variation

18. 18 Copyright © Monash University Call Progression Calling Party ATM Network/Switch SETUP (Call Ref, AAL, Address, Cell Rates, QoS) CONNECT (Call Ref, AAL, Connection ID - VPCI, VCI) CONNECT ACK (Call Ref) Various timers used during call connection phase Various timers used during call connection phase Active State VPI 0, VCI 5

19. 19 Copyright © Monash University Switch to Switch Signalling Routing –How to find destination Resource allocation –Quality of Service guarantees –Connection Admission Control Signalling Protocol

20. 20 Copyright © Monash University Interim Inter-Switch Protocol (IISP) Precursor to PNNI –PNNI phase 0 Based on UNI 3.1 Static Routing

21. 21 Copyright © Monash University P-NNI Standard Private Network to Network Interface ATM Forum Standard Communications between switches in a private network Scalability

22. 22 Copyright © Monash University P-NNI Protocol Stack PNNI UNI SSCF (Q.2130) and SSCOP (Q.2110) –Signalling Specific Coordinating Functions –Service Specific Connection-oriented Control –Data Link protocol AAL5 SSCF, SSCOP, AAL5 = SAAL

23. 23 Copyright © Monash University Functions of P-NNI Signalling protocol –Based on UNI 3.1 Routing –Most important function of P-NNI –Designated Transit List(DTL)

24. 24 Copyright © Monash University Routing in P-NNI Source based routing protocol Source specifies route to destination –Designated Transit List Transfer of topology information between switches Uses hierarchy and summarisation

25. 25 Copyright © Monash University Source Routing Source needs complete topology information Broadcast id on all paths Copy and transfer other nodes Scales poorly

26. 26 Copyright © Monash University P-NNI Topology Construction Hierarchy of Peer Groups –overcomes scalability problems of Source Routing Every member of Peer Group knows route to every other member –DTL in Setup message New DTL constructed whenever message leaves peer group

27. 27 Copyright © Monash University Exchange of information at first level within a PG PNNI topology state packets (PTSP) –reachable destinations within PG –current capabilities of nodes and links All members of Peer group flooded with PTSPs New PTSPs exchanged when –major events –information aged

28. 28 Copyright © Monash University Topology State Information Information transferred in PTSPs Attributes of Switch –total capacity Metrics –number of connections –used capacity

29. 29 Copyright © Monash University Reachability Information Based on Address prefixes Designated Transit List –Source route at each level

30. 30 Copyright © Monash University Exchange of information at higher level PGs Designated Peer Group Leader –Elected by other nodes –Election ongoing –Represents PG at next layer PGL summarises topology state and reachability information

31. 31 Copyright © Monash University GCAC and Crankback Generic Connection Admission Control (GCAC) –Indication only as to whether connection can be admitted Crankback enables alternate path to be found without abandoning complete call

32. 32 Copyright © Monash University Example of P-NNI connection establishment

33. 33 Copyright © Monash University Summary of Functions of PNNI Routing Discovery of neighbours and link status Synchronisation of topology databases Flooding of PTSPs Election of PGLs Summarisation of topology information Construction of routing hierarchy

34. 34 Copyright © Monash University Broadband ISDN User Part ITU-T standard Public carrier standard Connectionless, Hop-by-hop routing –similar to IP

35. 35 Copyright © Monash University Signalling between ATM Networks Interconnection between both public and private networks Private to private eg. Monash University / Melbourne University Private to public eg. Monash / Telstra Public to Public eg. Telstra / Optus

36. 36 Copyright © Monash University Issues with signalling between ATM networks Different network signalling standards Large amounts of topology information Confidential information –topology, metrics

37. 37 Copyright © Monash University Standards for Signalling between ATM Networks Broadband Inter-Carrier Interface –ATM Forum –Based on SS7, B-ISUP –Interworking between B-ISUP networks ATM Internetwork Interface (AINI) –Interworking between PNNI, B-ISUP –PNNI signalling with static routing –Connecting non-PNNI / PNNI networks

38. 38 Copyright © Monash University Conclusion Signalling functions User network interface signalling –UNI 3.0, 3.1 Switch to switch signalling –IISP, P-NNI

39. 39 Copyright © Monash University Questions Why is there no contention algorithm for access to the signalling channel in ATM? In the worked example of PNNI routing, what is the next DTL to be pushed onto the stack?