SS7 is a global standard for telecommunications that defines procedures and protocols for exchanging information between network elements to setup, route, and control calls. It uses a dedicated digital signaling network and 56/64 kbps signaling links. There are three main types of signaling points: SSPs that originate/terminate calls, STPs that route traffic, and SCPs that determine call routing. The protocol has multiple layers including MTP for transport, SCCP for addressing, and applications like ISUP for call control and TCAP for database queries.

1. SS7 Networks and Key Concepts

3. The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control.

5. wireless services such as personal communications services (PCS), wireless roaming, and mobile subscriber authentication

6. local number portability (LNP)

7. toll-free (800/888) and toll (900) wireline services

8. enhanced call features such as call forwarding, calling party name/number display, and three-way calling

10. more efficient use of voice circuits

11. support for Intelligent Network (IN) services which require signaling to network elements without voice trunks (e.g., database systems)

13. STP’s route network traffice between signaling points (ie acts like a network hub)

15. All nodes are interconnected via F-links

16. Reliable network configuration due to diversity

17. Signalling links are directly associated with the voice links

18. As the network expanses growth is complex to manage

19. Link growth

20. Services deployment

21. Interconnection between various operators are through Signaling Switching Points (SSPs)Existing Network Design in Europe

23. SS7 traffic is carried separately from voice traffic

24. STP acts as a gateway providing network protection

25. STPs are mated pairs using C-links

26. Pairs are interconnected via B/D-link quad

27. Architecture provides redundancy

28. Hierarchical design that simplifies changes

29. Interconnection between various operators are through STPsSimple, offers redundancy and increased reliability

31. Using layers to separate networks

32. Access is only granted a key locations

33. Backbone network allows for service to be offered across boundaries.

34. An single pair of STPs could be partitioned to support all or any layersUsing layers to separate networks

35. Signaling Interconnection RSTP D Links E Links LSTP LSTP SCP C Links A Links B-Link Quad SSP SSP LSTP LSTP Link Types: Access (A-Links): Connects STPs with SSPs, SCPs or MSC (Message Switching Center) Bridge (B-Links): Connects STPs Cross (C-Links): Connects mated STPs Diagonal (D-Links): Connects regional/local STPs to primary STPs Extended Links (E-Links): Connects SSPs , SCPs or MSC to alternate STPs Fully-Associated (F-Links): Connects SSPs

36. Linksets Combined Linksets Linkset 1 Linkset 3 Linkset 2 Linksets: Group of links between two nodes in the network Links are deployed in numbers to the power of 2 (1, 2, 4, 8) Traffic is loadshared over all link in the linksets Linkset size is limited by the protocol being used Combined linksets between STP pairs allow for loadsharing over both nodes to increase redundancy.

37. Point Codes Point Codes: Each signaling point in a SS7 network is assigned a unique point code Point code structure: ITU - 14 bit Point code ANSI - 24 bit Point code China - 24 bit Point code Japan - 16 bit Point code ITU Point Code: Basic: 14 International: 3 (Zone) - 8 (Area Network) - 3 (Signaling Point) Austria: 5 (Zone) - 4 (Region) - 5 (Signaling Point) China: 4 (Zone) - 7 (Exchange) - 3 (Signaling Point) Germany: 4 (Num Area) - 3 (HVST) - 4 (KVST) - 3 (Signaling Point) Node Identifiers: Origination Point Code (OPC) Destination Point Code (DPC) 0-1-0 1-1-0 3-3-3

38. Routesets Routesets Routes are defined between paths to a specific DPC A collection of Routes are defined as a Routeset Multiple Routes in a Routeset ensure that redundancy is build into the product. Routes are costed (Less expensive routing) 0-1-0 0-1-0 1-1-0 1-1-0 3-3-3 3-3-3

39. Subsystems Numbers/GTT Subsystem Number (SSN) Uniquely identifies an application residing on a destination point; typically an SCP database. Global Title Translation (GTT) Global Title Translation(GTT) provide specific information with regards to the Destination Point Code of the location of the application.

40. SS7 Protocol Layers

41. SS7 Protocol Stack The hardware and software functions of the SS7 protocol are divided into functional abstractions called "levels". These levels map loosely to the Open Systems Interconnect (OSI) 7-layer model defined by the International Standards Organization (ISO).

42. SS7 Protocol SS7 Protocol Layer Message Transfer Part (MTP) Level 1 Message Transfer Part (MTP) Level 2 Message Transfer Part (MTP) Level 3 Signal Connection Control Part (SCCP) Transaction Capabilities Part (TCAP) Key Protocol Specifications ITU Specifications: White Book (1992) Q701-Q709 (MTP), Q710-Q716 (SCCP), Q75x (Measurements) ETSI Specifications: 300 008 (MTP), 300 009 (SCCP) ANSI Specifications: GR-82, GR-246

44. Ensure message are transmitted accurately end to end, in sequence

46. Message Transfer Point (MTP):Level 3 MTP Level 3 Network level Message routing and network management Most effective message route between two signaling points Rerouting traffic away from failure Notification to all network to ensure minimal impact during failure modes (congestion control).

47. MTP Message Header Cont’d

48. SCCP Layer Provides connectionless and connection-oriented network services. Where MTP route messages to a signaling point, SCCP will determine an application at that point. Determines network address and relay the information to MTP layer SCCP also provides the means by which an STP can perform global title translation (GTT), a procedure by which the destination signaling point and subsystem number (SSN) is determined from digits (i.e., the global title) present in the signaling message.

50. ISUP (ETSI, ANSI), xTUP

51. Call control part of the protocol

52. The ISDN User Part (ISUP) defines the protocol and procedures used to set-up, manage, and release trunk circuits that carry voice and data calls over the public switched telephone network (PSTN). ISUP is used for both ISDN and non-ISDN calls.

53. TCAP

54. Transfer non-circuit related information

55. Supports database queries and responses between SSPs and SCPs

57. Network Management and GTT Examples

59. Providing the links between the STPs are a combined linkset the messages are loadshared across the links.

61. STP A notifies it associated links (Directly connected links) to not send message to the SSP if another path is available - Restricted

62. All messages are now sent from SSP (0-1-0) through STP C to STP B.

64. All messages are now sent from SSP (0-1-0) through STP C to STP A to STP B - C link routing

66. STP A and B notifies all nodes (associated and quasi-associated) to not send message to the SSP - Prohibited

68. Country A NI=2 Country A NI=2 Country C NI=3 Country B NI=2 Network Indicator International Network Indicators (“0” and “1”are not regulated and for use at the International boundaries) National Network Indicators (“2=National”, and “3=National spare”) are left up to National networks to define. Nationally standardized Network Indicator values has started to cause interworking issues. Global Operators that operate in more than one country are facing NI conflicts when trying to connect to different National and International networks each defining their own NI usage requirements. NI 0 International NW 1 Spare (international use) 2National Network 3 Reserved for National use ? Needs are proprietary; Conflicts and needs can be resolved at a gateway STP

71. Option 2:

72. Partitioning in the STP Multiple PCs per NI

73. Links are required between 2 nodes for each Network Indicator (NI).

74. Example: A C-Link is required for each STP identity.SSP SSP STP1 STP2 NATL ITU PC=320 NATL ITU PC=220 NATL ANSI PC=330 NATL ANSI PC=230 SSP SSP

76. Cost effective, Low Power/Real estate requirements

77. SCP/Boundary Gateway solutions - LNP, Mediation, etc.

78. Universal NP Master: Third generation number portability solution based on the Signaling Server Platform Technology

79. Scalable, flexible implementation, proven LSMS

81. Universal Mediation Platform - Adds ability to control requests from another operator’s networks. Guards against inappropriate and/or illegal use of host network and services. Screens ISUP and TCAP messages and their content.