Intelligent Network Application Part / Protocol - part of the C7 stack, this protocol deals with pure signalling transactions between an SCP (Service Control Point) and an SSP (switch) in [SS7| SS7 networks. Available in CS1, CS1+ and CS2 (CS = Capability Set flavours. CS1 is the original, CS1+ consists of all the hacks put into CS1, and CS2 is a pipedream given switch vendor proliferation.

Typically, a call will hit an SSP over ISUP, NUP or any of a thousand other C7 bearer protocols, the A number and B number are stripped from the associated signalling channel and passed by the SSP to the SCP using INAP. The SCP is usually just a honking great database with line interfaces and a suitable SCP application, such as number translation. The SCP decides what to do with the call and passes an INAP transaction containing the instructions on how to handle the call, often just a new B number

INAP is sweet, as it allows the intelligence of a voice network to be divorced from the traffic. Switches can be left to switch calls, under control of intelligent peripherals such as SCPs which take care of the clever bits and are much easier to provision.

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