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SS7What is SS7?

SS7 or C7 signalling is the core signalling/control protocol used within fixed and mobile networks. The SS7 network is both a high speed and high availability network providing the backbone of all telephony networks worldwide.

SS7 Network Topologies

The diagram opposite shows the general representation of an SS7 interconnect.

OP - Originating Point
DP - Destination Point
AP - Adjacent Point

This diagram is a configuration overview of the network with relationship to a point of interconnect. The table below defines the terms
used within the diagram.

The modules and terms used in the diagram and table will be understood by all SS7 interconnect providers.

In general these configurations can be broken down into two main interconnects ‘A’and ‘F’ signalling link configurations.

SS7 Networks Topologies

SS7 Network Topologies Terminology

Originating Point (OP) The Originating Point describes the equipment that is interconnecting into the SS7 network. The originating point will be provided with a unique point-code by the network provider allowing for identification of this point within the SS7 network.
Signalling Link The SS7 network uses the signalling links to transport the call information for a particular interconnect. In SS7 the signalling links are not on every TDM interface. A single SS7 signalling link can control the calls across multiple TDM interfaces allowing for a distributed architecture.
Linkset A number of links can be grouped into a linkset that connects to an adjacent point. Each signalling link is provided with a unique code called a signalling link code (SLC). Traffic is load-shared across this linkset. The signaling links within a linkset also provide a redundant transport mechanism. Therefore the more links there are to a linkset the higher the transport bandwidth is and the higher the redundancy.
Adjacent Point (AP) The Adjacent point is the SS7 equipment which the signaling links terminate on. This equipment will also have a unique point code. This equipment may be either STP equipment or SSP equipment depending on type of interconnect.
Destination Point (DP) The Destination Point of the SS7 network defines the switching equipment within the PSTN network which terminates the TDM interfaces of this interconnect. This point is also allocated a unique point-code within the SS7 network. If the adjacent point is a SSP or MSC interconnect the destination point will be the same as the adjacent point.
Route The route defines which adjacent point the destination point can receive and transmit signalling traffic to. A particular destination point may have a number of routes to different adjacent points.
Routeset A routeset is made up of a number of routes. This allows for redundancy within the SS7 network allowing for communication from the originating point to the destination point even if a particular adjacent point fails.