What is SS7 or C7?

SS7 or C7 signalling is the core signaling/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.

A-Link Interconnect or Non Associated or Quasi Associated Signalling

An A-link interconnect provides connections directly into the SS7 network generally via redundant STP pairs. STPs or Signalling Transfer Points provide a secure and fully redundant signalling only network, in diagram opposite showing a typical softswitch deployment.

The SS7 gateways connect directly to the two STPS (or adjacent points) and terminates directly the signalling links

In general no voice circuits are present on the TDM interfaces that are carrying the signalling links. The STPs direct the signalling information generated at the originating point [1] through the redundant network to the appropriate SSP. The SSP terminates the voice circuits associated with the call and presents them to the media gateways via the voice only TDM interface [2]. The SSP interconnects can be many miles from the STP SS7 interconnect allowing for centralised routing of traffic over many different territories.

a-link interconnect