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Signaling system 7 (ss7)

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A look at SS7

A look at SS7

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  • 1. 03/16/12 Tinniam V Ganesh tvganesh.85@gmail.com SIGNALING SYSTEM 7 (SS7)1 Tinniam.V. Ganesh tvganesh.85@gmail.com http://gigadom.wordpress.com/
  • 2. WHAT IS COMMUNICATION ? 03/16/12 Communication is used between 2 network elements to exchange information. Tinniam V Ganesh tvganesh.85@gmail.com There are 2 types of domains in the communication world  Data communication  Telecommunication 2
  • 3. DIFFERENCES BETWEEN TELECOM &DATACOM 03/16/12 Telecommunication Data Communication Tinniam V Ganesh tvganesh.85@gmail.com Network used for making voice Network used for transferring calls between telephones data from one computer to another Telephones were the end points Computers were the end point Uses protocols like ISUP, ISDN Predominantly uses TCP/IP Network elements are MSC, Network elements are Routers, HLR, SCP etc hubs, ATMs, bridges etc Uses circuit switching Uses packet switching 3
  • 4. NETWORKS OF TODAY … 03/16/12 In the networks of today telecommunication networks are used to download data e.g.GPRS Tinniam V Ganesh tvganesh.85@gmail.com Data networks are used for making Voice Calls e.g. VOIP 4
  • 5. WHAT IS SIGNALING ? 03/16/12 Signaling refers to the exchange of information between network elements Tinniam V Ganesh tvganesh.85@gmail.com Signaling between network elements follows a specific protocol A Protocol refers to the set of rules for communicating between the elements 5
  • 6. WHAT IS SS7 SIGNALING ? 03/16/12 Signaling System 7 was devised by ITU-T (formerly known as CCITT) Tinniam V Ganesh tvganesh.85@gmail.com Initially the signaling in trunks used to happen on the same channel in which the voice call used to occur. Hence call setup, digits etc would use the same line as the actual voice circuit In SS7 a separate channel is allocated just for signaling. This is known as Out-Of- Band signaling 6
  • 7. SS7 SIGNALING 03/16/12 Signaling happens in a separate channel outside of the voice channels Tinniam V Ganesh tvganesh.85@gmail.com A separate timeslot is used to transfer signaling messages like call setup, teardown etc This is also known as Common Channel Signaling (CCS) 7
  • 8. ADVANTAGES OF OUT OF BANDSIGNALING 03/16/12 Allows signaling at any phase of the call Allows upto 56 Kbps of signaling information Tinniam V Ganesh tvganesh.85@gmail.com Switch A Switch B Voice Trunk 8 Signaling Link
  • 9. SS7 STACK 03/16/12CAP,MAP Tinniam V Ganesh tvganesh.85@gmail.com … Application ISUP,TUP.. layer TCAP SCCP Network layer MTP 3 Network layer MTP 2 Data link layer MTP 1 Physical layer 9
  • 10. SS7 LAYERS 03/16/12 MTP – Message Transfer Part SCCP – Signaling and Connection Control Part Tinniam V Ganesh tvganesh.85@gmail.com TCAP – Transaction Capabilities Application Part CAP – CAMEL Application Part ISUP – ISDN User Part MAP – Mobile Application Part 10
  • 11. 03/16/12 Tinniam V Ganesh tvganesh.85@gmail.com 11SS7 VS OSI STACK
  • 12. SS7 PROTOCOLS 03/16/12SS7 protocols can be classified as call related and non-call related Tinniam V Ganesh tvganesh.85@gmail.com Call related protocols – ISUP (ISDN User Part), B-ISUP (Broadband – ISUP) Non-call related protocols –  INAP (Intelligent Network Application Part)  CAP (CAMEL Application Part)  MAP (Mobile Application Part)  … 12
  • 13. SS7 STANDARD BODIES 03/16/12 The SS7 standard body for North American market is ANSI (American National Standards Institute). The ANSI versions are ANSI ISUP, Tinniam V Ganesh tvganesh.85@gmail.com ANSI TCAP etc. The SS7 standard body for European market is ETSI (formerly CCITT). The ETSI versions of the protocols are ETSI ISUP, ETSI TCAP etc. There are minor variations in the protocols by the two standard bodies. 13
  • 14. SS7 Link speedsThere are 2 main standards in the world for 03/16/12transmission of PCM signalsT-Carrier – This is used in the North American market Tinniam V Ganesh tvganesh.85@gmail.comE-Carrier – This is used for European marketT1 – 24 channels * 64 Kbps = 1.544 MbpsE1 – 32 channels * 64 Kbps = 2.048 Mbps Level North American European 0 64 Kbps 64 kbps 1 1.544 Mbps (T1) 2.048 Mbps (E1) 2 6.312 Mbps (T2) 8.448 (E2) 3 44.736 Mbps (T3) 34.368 (E3) 14
  • 15. MTP LAYER 1 – PHYSICAL LAYER 03/16/12 This is the Physical Layer and defines the electrical and physical characteristics of SS7 links. Tinniam V Ganesh tvganesh.85@gmail.com Signaling links use DS-0 channels and carry data at 56 Kbps or 64Kbps. 15
  • 16. MTP LAYER 2 – DATA LINK LAYER 03/16/12 The data link level provides the network with sequenced delivery of all SS7 message packets between adjacent nodes Tinniam V Ganesh tvganesh.85@gmail.com It also provides for flow control and error checking 16
  • 17. MTP LAYER 3 – NETWORK LAYER 03/16/12 This provides network layer functionality. It delivers messages between signaling end points Tinniam V Ganesh tvganesh.85@gmail.com The network level depends on the services of Level 2 to provide alternate routing, and message distribution functions. 17
  • 18. SCCP (SIGNALING CONNECTION CONTROLPART) 03/16/12 Signaling Connection Control Part (SCCP) is a higher level protocol than MTP that provides end-to-end routing. Tinniam V Ganesh tvganesh.85@gmail.com SCCP is required for routing TCAP messages to their proper database. SCCP also does Global Title Translation to determine the end signaling point. 18
  • 19. TCAP (TRANSACTION CAPABILITIES APPLICATIONPART) 03/16/12 Transactional Capabilities Application Part (TCAP) facilitates connection to an external database. Tinniam V Ganesh tvganesh.85@gmail.com Information/data received is sent back in the form of a TCAP message 19
  • 20. APPLICATION LAYER 03/16/12 At the application layer there are the following protocols Tinniam V Ganesh tvganesh.85@gmail.com Call related  ISDN User Part (ISUP) supports basic telephone call connect/disconnect between end offices. Non-call related  CAP – Camel Application Part is used to access a database ,the SCP and influence the call 20
  • 21. SS7 SIGNALING ARCHITECTURE 03/16/12There are 3 main elements in SS7 signaling architecture Tinniam V Ganesh tvganesh.85@gmail.comSSP – These are SS7 capable digital switchesSTP – These are SS7 capable network elements that route incoming SS7 messages to the correct destinationSCP – These are databases which take part in non- call related SS7 signaling 21
  • 22. ISUP CALL FLOW 03/16/12 Switch A Switch B A dials digits Initial Address Message (IAM) B’s phone rings.. Tinniam V Ganesh tvganesh.85@gmail.com Address Complete Message (ACM) B Answers Answer Message (ANM)A disconnects Release Message (REL) B disconnects Release Complete (RLC) 22
  • 23. 03/16/12 Tinniam V Ganesh tvganesh.85@gmail.com 23 Thank You !!!