SS7 - Signaling System No. 7 (2G/3G) ====================================== .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is SS7?** * SS7 (Signaling System No. 7) is a set of telephony signaling protocols used to set up and tear down telephone calls, manage mobile services, and support features like SMS, number translation, and prepaid billing. It is used in traditional circuit-switched telephone networks (PSTN) and mobile networks (2G/3G). * SS7 enables communication between network elements like switches, databases (e.g., HLR, VLR), and service control points (SCPs). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Why is SS7 useful?** * SS7 is critical in legacy and mobile telecom infrastructure because: * Call setup and teardown – Establishes and ends voice calls across networks. * Mobile roaming – Supports location updates and handovers between networks. * SMS delivery – Transports text messages between mobile devices. * Number translation – Enables services like toll-free numbers and call forwarding. * Billing and prepaid services – Supports real-time charging and account management. * Network management – Provides signaling for congestion control, fault detection, and routing. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How it works?** * Call Initiation – A user dials a number; the local exchange sends a signaling message via SS7. * Routing and Translation – SS7 queries databases (like HLR or SCP) to resolve the destination or service logic. * Call Setup – The call is routed through the network using ISUP (ISDN User Part) messages. * Call Management – SS7 handles call progress, status updates, and supplementary services. * Call Termination – When the call ends, SS7 tears down the connection and updates billing systems. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Where is SS7 used?** * Public Switched Telephone Network (PSTN) – For call control and routing. * Mobile networks (2G/3G) – For roaming, SMS, and subscriber management. * SMS Centers (SMSC) – For delivering and routing text messages. * Intelligent Network (IN) services – Like toll-free numbers, call forwarding, and prepaid billing. * Mobile Number Portability (MNP) – For querying number databases. * Lawful Interception – Used by governments for surveillance and monitoring. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Which OSI layer does SS7 belong to?** * SS7 spans multiple layers of the OSI model, but its core signaling functions are implemented at the Network Layer (Layer 3). Here's why: * Message Routing: SS7 uses the Message Transfer Part (MTP) and Signaling Connection Control Part (SCCP) for reliable message delivery and routing, which are Layer 3 functions. * Addressing and Switching: It handles global title translation and point code addressing, similar to IP routing. * Reliable Transport: While MTP Level 2 ensures reliable delivery (like Layer 2), the core logic of SS7 signaling resides in Layer 3. * Protocol Stack: SS7 has its own layered architecture (MTP1–3, SCCP, TCAP, ISUP, MAP), which maps roughly to OSI Layers 1–4, with Layer 3 being the most central for signaling logic. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow Topics in this section, * :ref:`Learnings in this section ` * :ref:`Terminology ` * :ref:`Version Info ` * :ref:`SS7 Version&RFC Details ` * :ref:`SS7 Basic Setup on Ubuntu using IPv4 ` * :ref:`SS7 Basic Setup on Ubuntu using IPv6 ` * :ref:`SS7 Protocol Packet Details ` * :ref:`SS7 Usecases ` * :ref:`SS7 Basic Features ` * :ref:`SS7 Feature : Out-of-Band Signaling ` * :ref:`SS7 Feature : Reliable Message Transfer ` * :ref:`SS7 Feature : Global Title Translation ` * :ref:`SS7 Feature : Fast Call Setup ` * :ref:`SS7 Feature : Network Management ` * :ref:`SS7 Feature : Support for Mobile Services ` * :ref:`SS7 Feature : Scalability ` * :ref:`SS7 Feature : Interoperability ` * :ref:`SS7 Feature : Security (Basic) ` * :ref: `SS7 Feature : Service Flexibility ` * :ref:`Reference links ` .. _SS7_step1: .. tab-set:: .. tab-item:: Learnings in this section * In this section, you are going to learn .. _SS7_step2: .. tab-set:: .. tab-item:: Terminology * Terminology .. _SS7_step3: .. tab-set:: .. tab-item:: Version Info * Version Info .. _SS7_step5: .. tab-set:: .. tab-item:: SS7 Version&RFC Details .. csv-table:: :file: ./SS7/ss7_rfc_details.csv :widths: 10,10,10,30 :header-rows: 1 .. _SS7_step20: .. tab-set:: .. tab-item:: SS7 Basic Setup on Ubuntu using IPv4 * Setup .. _SS7_step21: .. tab-set:: .. tab-item:: SS7 Basic Setup on Ubuntu using IPv6 * Setup .. _SS7_step6: .. tab-set:: .. tab-item:: SS7 Protocol Packet Details **MTP Level 2 Packet** **MTP Level 3 Packet** **SCCP Packet** **TCAP Packet** **ISUP Packet** **MAP Packet** .. _SS7_step7: .. tab-set:: .. tab-item:: SS7 Usecases .. csv-table:: :file: ./SS7/ss7_usecases.csv :widths: 10,20,30 :header-rows: 1 .. _SS7_step8: .. tab-set:: .. tab-item:: SS7 Basic Features .. csv-table:: :file: ./SS7/ss7_features.csv :widths: 10,10,30 :header-rows: 1 .. _SS7_step9: .. tab-set:: .. tab-item:: SS7 Feature : Out-of-Band Signaling **Out-of-Band Signaling - Testcases** .. csv-table:: :file: ./SS7/ss7_feature1_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step10: .. tab-set:: .. tab-item:: SS7 Feature : Reliable Message Transfer **Reliable Message Transfer - Testcases** .. csv-table:: :file: ./SS7/ss7_feature2_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step11: .. tab-set:: .. tab-item:: SS7 Feature : Global Title Translation **Global Title Translation - Testcases** .. csv-table:: :file: ./SS7/ss7_feature3_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step12: .. tab-set:: .. tab-item:: SS7 Feature : Fast Call Setup **Fast Call Setup - Testcases** .. csv-table:: :file: ./SS7/ss7_feature4_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step13: .. tab-set:: .. tab-item:: SS7 Feature : Network Management **Network Management - Testcases** .. csv-table:: :file: ./SS7/ss7_feature5_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step14: .. tab-set:: .. tab-item:: SS7 Feature : Support for Mobile Services **Support for Mobile Services - Testcases** .. csv-table:: :file: ./SS7/ss7_feature6_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step15: .. tab-set:: .. tab-item:: SS7 Feature : Scalability **Scalability - Testcases** .. csv-table:: :file: ./SS7/ss7_feature7_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step16: .. tab-set:: .. tab-item:: SS7 Feature : Interoperability **Interoperability - Testcases** .. csv-table:: :file: ./SS7/ss7_feature8_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step17: .. tab-set:: .. tab-item:: SS7 Feature : Security (Basic) **Security (Basic) - Testcases** .. csv-table:: :file: ./SS7/ss7_feature9_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step18: .. tab-set:: .. tab-item:: SS7 Feature : Service Flexibility **Service Flexibility - Testcases** .. csv-table:: :file: ./SS7/ss7_feature10_test_cases.csv :widths: 10,10,30,20 :header-rows: 1 .. _SS7_step19: .. tab-set:: .. tab-item:: Reference links * Reference links