7.1 Introduction

Networks are evolving to meet the need for more uninhibited information flow. Part of this evolution is a trend towards the use of more non-circuit-related signalling. Transaction Capabilities (TC)1 is a protocol that provides a non-circuit-related capability to transfer information between nodes. TC uses the Network Service (Layers 1 3) defined by the OSI Model (explained in Chapter 3), e.g. as provided by the SCCP and MTP.

7.2 Users

TC is a general protocol that can be used to support a broad range of users, including:

1. public land mobile networks;

2. intelligent networks;

3. supplementary services requiring non-circuit-related signalling;

4. operations, maintenance and administration.

( a) In mobile communications, the Mobile Application Part (MAP) provides a range of functions to route calls to and from the mobile customer. For example, the location of the customer is regularly fed into Location Registers. These provide the network with routing information for the mobile customer's incoming calls. The process of updating the registers uses TC to carry the location information. MAP is explained in Chapter 8.

( b) In intelligent networks, specialised information is stored in separate nodes (databases). The Intelligent Network Application Part (INAP) uses TC to perform non-circuit-related information transfer between exchanges and databases, e.g. to provide additional routing information. INAP is explained in Chapter 9.

( c) Some advanced supplementary services require non-circuit-related information transfer to complete a call. For example, a procedure can be adopted in which a local exchange can gain information about a called number, before...