MTP is responsible for reliable, unduplicated and in-sequence transport of SS7 messages between communication partners.
Primarily, this involves the conversion of messaging into electrical signal and the maintenance of the physical links through which these pass.
The signalling link functional level may also be provided using the SIGTRAN protocol M2PA described in RFC 4165.
MTP Level 2 ensures accurate end-to-end transmission of a message across a signaling link.
MTP2 provides flow control, error detection and sequence checking, and retransmits unacknowledged messages.
Access to the signalling link functional level's service interface can be provided over SCTP by the SIGTRAN protocol M2UA, described in RFC 3331.
The functions of MTP Level 3 may also be replaced with the Generic Signalling Transport Service described in ITU-T Recommendation Q.2150.0 as provided by MTP3b (Q.2150.1), SSCOP or SSCOPMCE (Q.2150.2) or SCTP (Q.2150.3).
MTP Level 3 functions can also be provided by using the IETF SIGTRAN M3UA protocol, described in RFC 4666, in IPSP mode.
MTP3 provides routing functionality to transport signaling messages through the SS7 network to the requested endpoint.
A distinction is made between a Signaling Transfer Point (STP) which only performs MTP message routing functionalities and a Signaling End Point (SEP) which uses MTP to communicate with other SEPs (that is, telecom switches).