Introduction to ss7
- 1. Introduction to SS7 Konrad Hammel Sangoma Technologies
- 2. • What is SS7? • SS7 Network Elements – SCP, STP, and SSP • SS7 Link Types – A,B,C,D,E, and F links • Basic Call Messages – IAM, ACM, ANM, REL, and RLC • SS7 Signaling Stack – MTP1, MTP2, MTP3, ISUP, and others • SS7 Signaling Messages – FISU, LSSU, and MSUs • SS7 Addressing – SPC, DPC, and APC Outline 2
- 3. • Signaling System 7 – CCSS7, C7, number 7, CCIS7 • Official Standard by ITU in 1980 • Common Channel Signaling (CCS) – Signaling channel, CICs • 2 versions…ITU and ANSI • Universal signaling via a suite of sub-protocols – ISUP, TUP, DUP, etc What is SS7? 3
- 4. • 3 types of Switches • Signal Switching Points (SSP) – Terminate signaling links – Start, end, and switch calls • Signal Transfer Points (STP) – Main routing switches • Signal Control Points (SCP) – Switches attached to Databases SS7 Network Elements 4
- 6. • A Links – Link between to end-points – “A” stands for Access – Purpose is to deliver signaling messages – Connects an SSP to an STP – Connects an SCP to an STP • C Link – Link between 2 STPs (making them a “mated” pair) – “C” stands for Cross Link SS7 Link Types 6
- 8. • B Links – Link between 2 mated STP pairs – “B” stands for Bridge Link • D Links – Link between 2 mated STP pairs (different hierarchical levels) – “D” stands for Diagonal Link SS7 Link Types 8
- 10. • E Links – Link between an SSP and a secondary mated STP – “E” stands for Extended Link • F Links – Link between 2 SSPs – “F” stands for Fully Associated SS7 Link Types 10
- 12. • 5 Basic messages to establish a connected between 2 end points • IAM – Initial Address Message – Requests the call/connection • ACM – Address Complete Message – Confirms reception of IAM • ANM – Answer Message – Confirms the route of the voice (which CICs to use) • REL – Release Message – Requests an end to the call • RLC – Release Complete Message – Confirms the end of the call Basic Call Messages 12
- 13. • MTP1 – Physical layer – DS-0 channel (56k or 64bit) • MTP2 – Data Link Layer – Ensures reliable transmission – Error checking, flow control, and sequence checking • MTP3 – Network Link Layer – Ensures message delivery in the network – Addressing, routing, and congestion control • ISUP – Application Layer – Protocol that establishes calls between 2 end points – Call setup, call information, and call tear down SS7 Signaling Stack 13
- 14. • 3 type of messages • FISU – Fill In Signal Units – MTP2 – Sequence checking, error checking, and line filler • LSSU – Link Status Signal Units – MTP2 – Signaling status messages – Used to “align” or “sync” two points • MSU – Message Signal Units – MTP3 – Carry all messages between points SS7 Signaling Messages 14
- 15. • 3 types of addresses • 2 different styles of addresses – ITU -> Decimal Number…1234 – ANSI -> Network-Cluster-Member…. 1-2-3 • SPC – Self Point Code – The address of the local system • APC – Adjacent Point Code – Address of system on the other end of the signaling link • DPC – Destination Point Code – Address of system that controls the voice CICs SS7 Addressing 15
- 16. THANK YOU. 16