SS7 & Sigtran technologies, Architecture & signaling flows

Understand how signaling messages coordinate call setup, location, registration, and authentication across core network nodes (MSC, HLR), and how signaling protocols differ from traffic.

Explore how signalling enables end-to-end call setup, management, and resource release, with features like call forwarding, caller name, conference calls, handover, and location update, registration, authentication.

Compare channel associated signaling and common channel signaling to reveal their time-slot usage in a tdm network, including synchronization slot 0, signaling slot 16, and traffic slots.

Explore SS7 architecture through signaling points, including SP and STP, where the serving switching point switches calls, manages signaling messages, and initiates call setup via the MSC.

STP acts as a router in signaling networks, interworking between TDM and IP and routing messages between MSCs, without initiating signaling, while distributing traffic across echelons to improve utilization.

Discover the service control point (scp) in ss7 architecture, a network database like hlr or sms, that accepts data queries and subscriber location requests and returns information to the msc.

Identify the originating point MSC that sends signaling messages to the destination point, and explain paired signaling links, link sets, signaling routes, and route sets from 0.1 to 0.3.

Understand the SS7 protocol stack, including MTP layer one, two, and three, and how they ensure signaling delivery, error detection, and routing between network nodes.

Describe MTP layer one as the physical layer, providing the link between network nodes via E1, with 32 timeslots per E1, and timeslot 16 for signal and 0 for synchronization.

Explore the MTP level two role in error detection, correction, and protection for signaling units, using the signaling unit error rate monitor to trigger backup links at threshold 100.

Explore MTP2 signaling units: FISU, LSSU, and MSU, and learn the role of each type, with MSU highlighted as the most important.

Configure MTP2 FISU signaling to monitor signaling links by periodically sending fill-in signaling units, awaiting acknowledgments, to detect link problems using a predefined 150 milliseconds interval.

Learn how the MTP2 link status signaling unit (LSSU) shares the status of network nodes, indicating busy, high traffic, or normal conditions between MSCs before sending signaling messages like IAM.

Discover how the message signaling unit (MSU) carries call control and signaling messages. Routing labels with origin and destination point codes steer MSU traffic through the core network.

Explain the signal unit field LI and its parameters for fill in signaling unit, link state signaling unit, and message signaling unit, focusing on the six-bit length indicator.

Describe how the MTP signal unit uses an 8-bit flag to mark signalling messages, such as 0610, and how a false flag inserts a zero after five ones for recovery.

Explain how the backward sequence number (BSN) and forward sequence number (FSN) track signaling messages, and how the backward indicator bit signals positive acknowledgement when delivered correctly.

Explain the forward indicator bits, FIB, in SS7 signaling, showing how zero indicates the first send and one triggers retransmission after a failed delivery, with acknowledgments verifying delivery.

Explore MTP error control and signaling flows by walking through an example of forward and backward sequence numbers, forward indicator bits, and acknowledgments, including retransmission cases and mistakes.

Learn how MTP-2 ensures error-free, in-sequence signaling delivery. Explore ICU, FISU, LSU, and MSU/MCU interactions, the signaling unit error rate monitor, and CRC checks in CIF.

MTP three handles addressing and routing of signaling messages in the third layer, using destination and originating point codes and routing labels to direct and reroute traffic.

Explore MTP3 point codes, including originating and destination point codes, the routing label in CIF field, and how network identifier, cluster, and member define signaling routing within the MSC.

Explore MTP3 signaling link selection in SS7 and Sigtran architectures. Understand load sharing across signaling links, the routing table, and link-set decisions using point codes.

Explain how MTP one, two, and three provide a stable core for signaling, with MTP users such as MAP and AIS interacting through SCC and TCP protocols.

Understand the ISDN user part as the control and signaling protocol for call setup, resource reservation, and release, with B-number analysis guiding routing within the MSC.

The IAM initiates a call setup between subscribers, carrying the circuit identification code, b-number, routing information, and forward indicators, then supports redirection and release signaling.

Describe ISUP ACM, the address complete message that notifies the originating side that the called party is ready, triggering ringing while timers like TX7 govern setup and release.

Explore ISUP messages in other signaling messages, including segmentation for payloads over 279 octets, and how answering, connect, call progress, and release messages coordinate a voice call.

Explore ISUP call establishment and end-to-end signaling in SS7, detailing subsequent address message, address complete, call progress, answer, release, and release complete flows between A and B numbers.

Explore the signaling connection control part (SCCP) and its services, addressing MTP3 limitations with point codes, global titles, and routing for circuit and non circuit signaling.

Insert the destination point code into the MTP routing label to route signaling messages between networks, and identify the subsystem number to determine the next node.

Discover how global title translation uses address information, nature of the destination, and numbering plan translation type to choose the translation table and routing path via MTP and point codes.

Explore the TCAP protocol stack and usage scenarios, showing how TCAP, CAP, and PT CAP enable dialogue-based subscriber updates via MTP routing, CCP, and MAP signaling.

Explore TCAP component and transaction sublayers, including uni directional messages, begin, continue, and end messages, abort and cancel sequences that manage HLR and MSC communications.

Explain how a subscriber authenticates to the network during a location update, detailing the MSC and NSC exchange of authentication info, triplets, and subscriber data for authorization and location services.

Explains the BSSAP protocol between the MSC and the BSS, detailing the BSC application part and DTAP, and outlining cipher mode command and cc signaling messages.

Explore how intelligent networks enable value-added services in mobile operators using INAP, including service switching function, service control function, service data point, and balance-based charging for prepaid calls.