4.1 Introduction

The Message Transfer Part1 (MTP) is responsible for the transfer of signalling messages between signalling points. The MTP does not understand the meaning of the messages being transferred: its job is to deliver the messages in a flexible and secure manner. The aim is to deliver the information within messages without loss, without duplication, free of errors and in a pre-arranged sequence. Procedures are included that react to network and system failures, thus providing a high level of security.

The specification of the MTP is structured to allow flexible implementations that can be optimised in practical networks. It is an intelligent transfer mechanism that can reconfigure and control signalling traffic to overcome failures in the network. The users of the MTP define the meaning of the messages and high-level procedures.

The MTP is responsible for a very high level of reliability for successful conveyance of messages. To achieve the high targets set by the ITU-T2, error detection and error correction techniques are employed, as well as actions to control the signalling network. Some significant performance targets are:

• undetected errors; less than one in 10 ¹⁰;

• loss of messages; less than one in 10 ⁷;

• out-of-sequence delivery to higher levels; less than one in 10 ¹⁰.

4.2 Architecture