INWK6113

1. SSP SSP SCP INWK6113 STP STP Lesson 4Signaling System #7 Based on Autry Owen slides Many slides courtesy of

2. Signaling System #7 • History / Background / Why? • Signaling Taxonomy • Services • Network Architecture • Signaling Protocol

3. Signaling System #7 (SS7) SS7: First issued by CCITT in 1980, SS7 is designed to be an open-ended common-channel signaling standard that can be used over a variety of digital circuit-switched networks. SS7 is specifically designed to be used in IDNs. So What?: SS7 is how the commercial world does subnetwork signaling and is the definition of advanced intelligent network. Current fixed station circuit switches interface SS7. Future tactical systems must interface SS7 if they are to interface the PSTN.

4. Step 1: Obtain Traffic Data • Conceptually simple; difficult in practice • Sources of traffic information • Carrier bills • Shows only chargeable calls • Carrier design studies or traffic reports • Traffic reports from PBX • CDR (Call Detail Report) • Reports specific to manufacturer • Third party software and hardware available for analysis

5. Sample CDR Report

6. Signaling Networks Elements Control Plane SS7 I.451/Q.931 STP STP SP User SP User STP STP SP SP SP SP SP SP Signaling Point STP Signaling Transfer Point Information Plane LE User LE User LE Local exchange TC LE LE TC TC Transit center TC

7. Signaling Network Structures...

8. SS7

9. Characterization of Signaling Mechanisms

10. SS7 is Subnetwork Signaling End-User Devices End-User Devices Subnetwork Signaling End-User/Subscriber Signaling

11. SP SP SP Intelligent Network Concept End-User Devices End-User Devices STP STP SCP Sub-network Signaling SCP STP STP

12. 800 Database Service Call-setup services Alternate Billing Services Calling card verification 3d party billing Private Virtual Networks Personal communication service (PCS) Voice-activated dialing (VAD) Trunk Signaling Network 9-1-1 Network-based ACD Area-wide Centrex AIN Services

13. AIN ServicesContinued • Class Services • Customer Originating Trace • Automatic Recall • Automatic Callback • Calling Name Delivery • Calling Number Delivery • Calling Number Delivery Blocking • Distinctive Ringing / Call-waiting Tone • Selective Call Forwarding • Selective Call Rejection • Selective Call Acceptance

14. Signaling Network Elements

15. A B C D SS7 Networks P M L Q W Y X Z

16. Hierarchical Signaling Network STP STP STP Upper STP level SP STP STP STP STP STP STP STP Lower STP level SP SP SP

17. SS7 Link Types

18. SS7 Protocol Architecture

19. SS7 Data Link Layer

20. SS7 Signaling Link Layer

21. Flag Flag Flag SS7 Messages: Signal Units FISU 8 LSSU 8 MSU 8

22. Signal Unit Formats

23. SU Field Codes

24. SS7 Signaling Network Layer

25. Connection Control Part

26. SSP SSP Global Title Translation STP SCP STP

27. SSP SS7 Protocol Architecture L ET STP STP Enhanced User Services MTP3 MTP3

28. User / Application Parts

29. SSP SSP SS7 Protocol Architecture ET STP STP ET D D Signaling and Call Control

30. B SS7 Call Setup X W A

31. Protocol Architecture SS7 Model OSI Model OMAP Operation, Maintenance, and Administration ASE Application service element TCAP Transaction capabilities application part ISUP ISDN user part SCCP Signaling Connection Control Part MTP Message Transfer Part NSP Network Service Part Application OMAP ASEs Presentation TCAP ISUP Session Transport Network SCCP Signaling network NSP Signaling link Data Link MTP Physical Signaling data link

32. Message Transfer Part • SIGNALING-DATA-LINK Level • full duplex physical link at <=64 kbps • SIGNALING-LINK LEVEL • All transmitted blocks of data are delivered with no losses or duplications. • Blocks of data are delivered in the same order in which they were transmitted. • Highly related to LAPD and LAPB

33. Message Transfer Part - Level 3 Level 3 MTP Upper levels Level 2 MTP Level 4 TUP ISUP SCCP DUP Signaling Message Handling Message Distribution Message Discrimination Signaling Mes- sage Flow Message Routing Signaling Network Management Signaling Route Management Indications and Controls Signaling Route Management Signaling Link Management Testing and Maintenance

34. E&M Example

35. Signaling Architecture Components

36. SS7 Link Types • “A” Link: An access link connects a SSP or SCP to an STP. • “B” Link: A bridge link connects an STP to another STP. • “C” Link: A cross link connects two “mated pair” STP. This is done to improve reliability • “D” Link: A diagonal links similarly to a B link • “E” Link: An extended link connects an SSP to an extra STP in the event that the A link cannot reach one. • “F” Link: A fully associated link connects SSP’s

37. SS7 Relationship to OSI

38. SS7 Data-Link Layer (Layer 1) • Physical layer in OSI • Two bi-directional transmission paths for signaling • Two data channels running in opposite directions at same date rate (usually 56-64K)

39. SS7 Signal Link Layer (Layer 2) • Signal unit alignment and delimitation • Error detection • Error correction (preventive cyclic retransmission method) • Flow Control

40. SS7 Signal Units • Signaling units come in three types • 1) MSU (message signal unit) - carries • signaling information • 2) LSSU (link station signal unit) - • carries the link status information • 3) FISU (Fill-in signal unit) - fills in idle • time

41. SS7 Network Functions (Layer 3) • Message-handling functions • * message routing: used at each signaling point to determine the outgoing link • * message discrimination: determines if a received message is destined for it, or another point • * message distribution: delivers received message to correct user part

42. SS7 Network Functions (Layer 3) • Traffic Management Functions • * To control message routing. This includes modification of message routing to destination points, or to continue normal routing. • * Control signaling traffic by avoiding irregularities in message flow • * Flow control

43. SS7 Network Functions (Layer 3) • Link Management • * Can restore the availability of a link set • * Monitors status of signaling link • * Corrects out-of-service links • * Can provision new signaling links • * Automatically configures/reconfigures • signaling links

44. SS7 Connection Control Part • Services: • - connection oriented • - connection-less • - peer-to-peer communication • * Connection established • * Data transfer starts • * Connection releases

45. Introduction of IN Generic SCP • Application Software SCP ServiceManagementSystem STP • Calling card services • 800-/900-services Generic Call Processing SP • Triggers • Service independent

46. Advanced Intelligent Network (AIN) • Service-independent telecommunications • Intelligence moved out of switches Signaling Switching Center STP STP SP SP

47. Signaling Connection Control Part • the addressing capabilities of SCCP extend those found in MTP, which is limited to delivering a message to a specified node and using a 4-bit service indicator • Classic circuit-switched telephone call related signaling does not use SCCP. • Another enhancement is the ability to address messages such as dialed digits, that are not in a form usable by MTP for routing.

48. SCCP also provides enhanced message transfer services • Class 0 Basic connectionless. • Class 1 Sequenced (MTP) connectionless class • Class 2 Basic connection-oriented. • Class 3 Flow-control connection-oriented. • Numbering plan for International Signaling • a 14 bit binary code is used for id of SP • is geographically based • is administered by ITU-T • has no direct relation with telephone #

49. SCCP services • Connection-oriented control: • Controls the establishment and release of signaling connections and provides for data transfer on signaling connections. • 2. Management: • Provides capabilities beyond those of MTP to handle the congestion or failure of either the SCCP user or the signaling route to the SCCP user. With this capability, SCCP can route messages to backup systems in the event failures prevent routing to the primary system.