ECS5365 Lecture 3 ISDN Signalling and ISDN Applications

1. ECS5365 Lecture 3ISDN Signalling and ISDN Applications Philip Branch Centre for Telecommunications and Information Engineering (CTIE) Monash University http://www.anspag.monash.edu.au/~pbranch/masters.ppt

2. Outline • User network signalling • Q.931, Q.932, Q.95x • Network node signalling • Signalling System No. 7 • ISDN Applications

3. Signalling • Purpose of signalling in ISDN • setup, teardown and control of circuits • Network level in protocol stack • Signalling between the user and the network • Signalling between switches within the network

4. Exchange functional groups and interfaces (Attachment) • Line Termination (LT) • a line card in the exchange switch • Exchange Termination (ET) • a trunk card in exchange switch • U interface • Interface between NT1 and LT • V interface • Interface between LT and the ET

5. User Network Interface Signalling • Terminal | Exchange information (TE | ET) • Uses LAPD (D channel) • Circuit switched calls • ISDN to ISDN user, ISDN to PSTN user • Packet switched calls • ISDN to ISDN, and ISDN to PSN users • Supplementary services • e.g. closed user group, reverse charging

6. UNI Signalling Standards • DSS1 (Digital Subscriber Signalling System no 1. • User network interface • Q.931 refers to Basic Call Control Protocol • Q.932 is a syntax for supplementary services • Q.95x are a series of service-by-service protocols

7. Procedure for Simple Circuit Switched Call (Attachment) • Exchange of Q.931 messages across User Network Interface • Calling and called parties • Call establishment • Call information • Call clearing • Similar messages for packet mode and bearer services control

8. Circuit-Switched Call ‘en bloc’ and ‘overlap’ • ‘en-bloc’ SETUP message contains called party address • ‘overlap’ uses a sequence of INFORMATION messages to send called party address a digit at a time

9. Call establishment • ALERTING • CALL PROCEEDING • CONNECT • CONNECT ACKNOWLEDGE • INFORMATION • PROGRESS • SETUP • SETUP ACKNOWLEDGE

10. Call information • RESUME • RESUME ACKNOWLEDGE • RESUME REJECT • SUSPEND • SUSPEND ACKNOWLEDGE • SUSPEND REJECT

11. Call Clearing • DISCONNECT • RELEASE • RELEASE COMPLETE • INFORMATION • NOTIFY • STATUS • STATUS INQUIRY

12. Signalling System No. 7 Outline • Architecture • Protocols • Message Transfer Part • Signalling Connection Control Part • ISDN User Part

13. Signalling System No. 7 • Specialised packet switching network in its own right • Designed to support ISDN networks but also support other networks • Designed for reliability • Optimised for operation over 64 kbps digital channels • Interwork between Q.931 and SS7

14. Functional Entities (Attachment) • Signalling Point (SP) • any point in the network that can handle SS7 messages • origin / destination of SS7 messages • Signal Transfer Point (STP) • any point capable of switching SS7 messages • also classed as a SP • Signalling Link • data link that connects signalling points

15. Topology • As many redundant paths as possible • Single STP level preferable for performance • Each STP connects to every other STP • Each SP connects to at least 2 STPs • Single level not always possible • geography, reliability, capacity of STPs • hierarchical

16. Planes of Operation (Attachment) • Need to distinguish between control (SS7) and information planes • Control plane • responsible for establishing and managing connections • Information plane • system for transferring information once the call is set up

17. SS7 Protocols (Attachment) • Organised into Parts • Message Transfer Part (MTP) • Signalling Connection Control Part (SCCP) • Transaction Capabilities Applications Part (TCAP) • Operations, Maintenance and Administration Part (O&MAP) • ISDN User Part (ISUP) • NB: ISDN is a user of the MTP

18. Message Transfer Part • Provides a connectionless datagram service for sending messages • A message delivery system • Consists of three levels • Signalling data link • Signalling link • Signalling network

19. Signalling Data Link • Physical layer functions • Optimised for 64 kbps usage • Can operate at lower bit rates

20. Signalling Link Level • Data link layer functions • Analogous to LAPD • Ensures messages are sent without loss and in order • Includes sliding window flow control • Data link layer frames called signal units

21. Signal Units • Message signal unit (MSU) • data • Level status signal unit (LSSU) • can send a busy signal for flow control • Fill-in signal unit (FISU) • sent when no other signal units available to send

22. Signalling Network Level • Message handling functions • discrimination • routing - select signalling link • distribution - select user part • Network management functions

23. Signalling Network Management • signalling traffic management • diverts messages onto different signalling link without loss • signalling link management • turn signalling links on/off • signalling route management • sends congestion messages

24. Signalling Connection Control Part • Provides enhancements to MTP to provide more general network layer services • not needed for basic telephony • Additional addressing

25. ISDN User Part (Attachment) • Functions, procedures and information to provide circuit switched calls over ISDN • Uses MTP or SCCP to transfer messages • Must interwork with Q.931 call-control protocol

26. ISUP Message Categories • Forward setup messages • General setup messages • Backward setup messages • Call supervision messages • Circuit supervision messages • Group supervision messages • In-call modification messages • End to end messages

27. Other SS7 Parts • Transaction Capabilities Application Part • Functions not directly related to call setup • eg. 1800 numbers • Supplementary services implementation • Operations, Maintenance and Administration Part • SS7 control and maintenance functions

28. ISDN Applications • Voice • Internet access • Data • Lan Interworking • Video

29. Voice Applications • PABX networking • multicampus organisations • Voice / data multiplexers • multiple voice over single B channel • voice at 4.8 kbps • dynamic allocation between voice / data

30. Internet Access • email, Web, telnet, ftp etc. • Personal Internet access via BRI • IETF point to point protocol • Multilink PPP • ISDN PC card or ISDN router

31. Data Applications • Bandwidth on demand • Inverse multiplexing • aggregate multiple B channels

32. LAN Interworking • Bridging and routing across ISDN • Remote LAN access • Distributed Servers • Novell Netware

33. Video Applications • Video conferencing • room and desktop • Video on demand • Video messaging

34. Summary • User Network Interface Signalling • Q.931 • Signalling System Number System • Architecture • Protocols • Applications of ISDN • voice, internet, LAN and video

35. Reading for Next Week and Review Questions • Preliminary Reading • Chapter 13 and 14 of Stallings • (Broadband ISDN Architecture, Broadband ISDN Protocols) • Questions (not for assessment) • Routing is a layer 3 function, but is not supported by Q.931. Why not? • Why is there a distinction between the control and information planes within the ISDN?