The MTP acts as the carrier for all Signaling System 7 (SS7) messages in networks based on time-division multiplexing (TDM), providing the reliable transfer of messages from one signaling point to another. This function includes levels 1, 2, and 3. In addition to providing signaling-point-to-signaling-point communications, the MTP also provides error detection and correction.

The methodologies of MTP are very similar to those used in other bit-oriented protocols (BOPs), such as X.25. Sequence-numbering and error-checking mechanisms are very similar.

The signal-unit structure used in all SS7 messages provides all the information required by MTP levels 2 and 3. Flow control is provided through the use of a special signal unit called the link status signal unit (LSSU), which is described in this chapter. MTP is defined in International Telecommunications Union Telecommunications Standardization Sector (ITU-TS) Publications Q.701 through Q.704, Q.706, and Q.707. They can be found in Telcordia Publication GR-246-CORE, Volume 1, Chapter 1, Sections 111.1 through 111.8. American National Standards Institute (ANSI) publications referring to the MTP protocol are numbered T1.111-1992, Functional Description of the Signaling Message Transfer Part (MTP).

The Telcordia recommendations add reliability and versatility to the network. The Telcordia publications are almost identical to the ANSI and ITU-TS publications, other than the additions made by Telcordia for network reliability and availability.