2. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 1 CNS 479R Voice Over IP Signaling System 7 Gary D. Brown, Guest Lecturer Lecture 2

3. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 2 Signaling System 7 (SS7) Introduction SS7 Network Architecture SS7 Protocols SS7 Call Signaling VoIP Issues

4. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 3 SS7 Protocols Architecture –Definitions Functional Divisions –TDM-based Transport Protocols –IP-based Transport Protocols –Application-layer Protocols Call Control –Messages –Message Flows

5. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 4 SS7 Protocols—Architecture OSI ModelSignaling Point FunctionsSS7 Model Layer 7 TCAP ISUP Level 4 Layer 6 Layer 5 Layer 4 SCCP Layer 3 MTP3M3UA Level 3 Layer 2 MTP2SCTP Level 2 Layer 1 MTP1Ethernet Level 1

6. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 5 MTP1Message Transfer Part Layer 1 MTP2Message Transfer Part Layer 2 MTP3Message Transfer Part Layer 3 SCTPStream Control Transmission Protocol (IP) M3UAMTP3 User Adaptation Layer (IP) SCCPSignaling Connection Control Part TCAPTransaction Capabilities Application Part ISUPISDN User Part TUPTelephone User Part (not shown—obsolete) SS7 Protocols—Definitions

7. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 6 TDM-based Transport (traditional) –MTP1 –MTP2 –MTP3 IP-based Transport –Ethernet (IP network) –SCTP –M3UA Application Protocols –SCCP/TCAP –ISUP SS7 Protocols—Functional Divisions

8. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 7 MTP1Message Transfer Part Layer 1 –Physical layer DS0 in T1 or E1 (A-link, F-link) V.35 modem Satellite link –64 Kbps bandwidth 56 Kbps in “robbed-bit” T1 infrastructure –ITU-T Q.702 SS7 Protocols—TDM-based Transport

9. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 8 MTP2Message Transfer Part Layer 2 –Data Link Control layer Error Detection and Correction (CRC-16) Packet Sequencing Link Status Indicators –Signal Units FISU (Fill-in Signal Unit)—permits immediate detection of link error LSSU (Link Status Signal Unit)—provides link status between two SS7 nodes MSU (Message Signal Unit)—carries higher level protocol messages –ITU-T Q.703 SS7 Protocols—TDM-based Transport

10. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 9 MTP3Message Transfer Part Layer 3 –Network layer Routes SS7 messages to their destination nodes Reroutes SS7 messages during network failures –Network Status Signaling Link availability Point Code (Node) availability Congestion Control –Levels 0 (None), 1 (Some) and 2 (Severe) –Initiates local congestion control on SS7 message reception (“surge”) –Responds to remote congestion control indication by throttling transmission Link Set Changeover and Changeback –ITU-T Q.704 SS7 Protocols—TDM-based Transport

11. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 10 TDM-based Transport (traditional) –MTP1 –MTP2 –MTP3 IP-based Transport –Ethernet (IP network) –SCTP –M3UA Application Protocols –SCCP/TCAP –ISUP SS7 Protocols—Functional Divisions

12. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 11 SCTPStream Control Transmission Protocol –Reliable Transport –Datagram and/or Stream –Redundancy Multiple Data Streams Multi-homing (multiple IP addresses) Active/Standby –Efficiency No “Head of Queue” Blocking Short timeouts Heartbeats –IETF RFCs 2960, 3286, 3309 SS7 Protocols—IP-based Transport

13. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 12 M3UA MTP3 User Adaptation Protocol –Adaptation of SS7 Layer 4 protocols/MTP3 interface to IP network transport Appears as MTP3 interface to Layer 4 protocols Appears as IP-based application to SCTP –Maps between SS7 Point Codes (OPC/DPC) and IP addresses SS7 Point Codes with Circuit Identification Codes (OPC/DPC/CIC) and IP addresses (optional) –IETF RFC 4666 SS7 Protocols—IP-based Transport

14. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 13 TDM-based Transport (traditional) –MTP1 –MTP2 –MTP3 IP-based Transport –Ethernet (IP network) –SCTP –M3UA Application Protocols –SCCP/TCAP –ISUP SS7 Protocols—Functional Divisions

15. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 14 SCCPSignaling Connection Control Part –Transport interface between TCAP and MTP3 –Supports connectionless, “non-circuit” based messages –Traffic Management Maintains Signaling Point Status –Availability of Point Codes (SS7 Nodes) Maintains Subsystem Status –SCCP “user” availability (specific applications) Reroutes messages around failed subsystems (redundancy) –ITU-T Q.711-Q.716 SS7 Protocols—Application Protocols

16. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 15 TCAPTransaction Capabilities Application Part –Non-circuit related transactions –Common interface for transaction-type applications Global Title Translation (800, 900 Numbers) Line Information Database (LIDB) Query Wire-line/wireless Local Number Portability Query Directory Assistance Query –Protocol interface for application-oriented protocols INAP (Intelligent Network Application Protocol) IS-41 (North American wireless call control protocol) MAP (Mobile Application Protocol—ITU) –ITU-T Q.771-Q.775 SS7 Protocols—Application Protocols

17. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 16 ISUPISDN User Part –Call Control Signaling (call setup and teardown) –National Variants ITU 88 (14-bit PC/12-bit CIC) ANSI 88 (24-bit PC/14-bit CIC) ITU 92 (14-bit PC/12-bit CIC) ANSI 92 (24-bit PC/14-bit CIC) ITU 96 (14-bit PC/12-bit CIC) ANSI 96 (24-bit PC/14-bit CIC) ETSI (14-bit PC/12-bit CIC) ANSI 2000 (24-bit PC/14-bit CIC) BT ISUP (14-bit PC/12-bit CIC) (United Kingdom and former colonies) China (24-bit PC/14-bit CIC)(ANSI MTP3/ITU ISUP) Telefónica (14-bit PC/12-bit CIC) (Spain, Portugal, South America) –ITU-T Q.761-Q.769 SS7 Protocols—Application Protocols

18. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 17 ISUP Messages ISUP Call Control Message Flows –Call Setup –Call Teardown SS7 Protocols—Call Control

19. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 18 Call Control Messages (most commonly used) –ACMAddress Complete Message –ANMAnswer Message –CCRContinuity Check Request –CFNConfusion –CONConnect –COTContinuity Message –CPGCall Progress Message –CRGCharge Information Message –IAMInitial Address Message –INFInformation Message –INRInformation Request Message –RELRelease Message –RESResume Message –RLCRelease Complete Message –SAMSubsequent Address Message –SUSSuspend Message –USRUser-to-User Information SS7 Protocols—ISUP Messages

20. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 19 Circuit Management (most commonly used) –BLABlocking Acknowledgement –BLOBlocking –CGBCircuit Group Blocking –CGBACircuit Group Blocking Acknowledgement –CGUCircuit Group Unblocking –CGUACircuit Group Unblocking Acknowledgement –CQMCircuit Group Query –CQRCircuit Group Query Response –GRSCircuit Group Reset –GRACircuit Group Reset Acknowledgement –FAAFacility Accepted –FACFacility –FARFacility Request –FOTForward Transfer –FRJFacility Reject –IDRIdentification Request –IRSIdentification Response –RSCReset Circuit –UBLUnblocking –UBAUnblocking Acknowledgement –UCICUnequipped Circuit Identification Code SS7 Protocols—ISUP Messages

21. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 20 SS7 Protocols—ISUP Messages Message “Direction” Concept –Forward Direction Messages passed in the direction from the calling party to the called party Sometimes referred to as “downstream” –Backward Direction Messages passed in the direction from the called party to the calling party Sometimes referred to as “upstream”

22. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 21 SS7 Protocols—ISUP Messages Common ISUP Header –All ISUP message have common message header Originating Point Code (OPC) –Point code of switch transmitting original message Destination Point Code (DPC) –Point code of switch intended to receive message Circuit Identification Code (CIC) –Identifies circuit between transmitting switch and receiving switch; not necessarily the original and intended switches!

23. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 22 IAMInitial Address Message –Forward message indicating seizure of an outbound circuit and to transmit number and other information SAMSubsequent Address Message –Forward message indicating additional called party number information (ITU only) COTContinuity Message –Forward message indicating circuit continuity test is successful ACMAddress Complete Message –Backward message indicating all address signals required for routing call to called party have been received SS7 Protocols—ISUP Messages

24. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 23 CPGCall Progress Message –Backward message indicating significant event has occurred ANMAnswer Message –Backward message indicating the called party has answered RELRelease Message –Forward or backward message indicating the circuit is being released due to some reason RLCRelease Complete Message –Forward or backward message, sent in response to a Release message, indicating the circuit has been put into an “idle” condition SS7 Protocols—ISUP Messages

25. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 24 SUSSuspend Message –Message indicating subscriber has disconnected and the call has been suspended RESResume Message –Message indicating subscriber has reconnected and the call has been resumed RSCReset Circuit Message –Message forces circuit into “idle” state; causes any call or circuit seizure to be terminated CFNConfusion Message –Message indicates confusion about message just received; usually happens during congestion or because of software bug SS7 Protocols—ISUP Messages

26. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 25 ISUP Messages ISUP Call Control Message Flows –Call Setup –Call Teardown SS7 Protocols—Call Control

27. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 26 SS7 Protocols—Call Setup Message Flow

28. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 27 SS7 Protocols—IAM Message Flow CO Switch Tandem Switch CO Switch STP Calling CO switch sends Initial Address Message (IAM) in forward direction to called CO switch via tandem switches, and each switch seizes an outbound circuit and connects the backward talk path. Tandem Switch STP IAM

29. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 28 SS7 Protocols—ACM Message Flow CO Switch Tandem Switch CO Switch STP Called CO switch alerts called party (ring), sends Address Complete Message (ACM) in backward direction to calling CO switch via tandem switches, and calling CO switch plays ringing. Tandem Switch STP ACM

30. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 29 SS7 Protocols—ANM Message Flow CO Switch Tandem Switch CO Switch STP Called party answers, called CO switch sends Answer Message (ACM) in backward direction to calling CO switch via tandem switches, and all switches connect forward talk paths. Tandem Switch STP ANM

31. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 30 SS7 Protocols—Call Teardown Message Flow

32. © 2007-2008 Gary D. Brown UVSC CS 479R – Telecommunications and Voice Over IP Signaling System 7 Protocols 31 SS7 Protocols—REL Message Flow CO Switch Tandem Switch CO Switch STP Caller hangs up, calling CO switch sends Release Message (REL) in forward direction to called CO switch via tandem switches, and each switch sends Release Complete Message (RLC) in backward direction, disconnects the talk path and idles the circuit. Tandem Switch STP REL RLC