The SIGTRAN group was significantly influenced by telecommunications engineers intent on using the new protocols for adapting IP networks to the PSTN with special regard to signaling applications.
IUA provides an SCTP adaptation layer for the seamless backhaul of Q.921 user messages and service interface across an IP network.
The difference between M2PA and M2UA is described in section 1.9 of RFC 4165 M2UA provides an SCTP adaptation layer for the seamless backhaul of MTP Level 2 user messages and service interface across an IP network.
M3UA provides an SCTP adaptation layer for the seamless backhaul or peering of MTP Level 3 user messages and service interface across an IP network.
SUA provides an SCTP adaptation layer for the seamless backhaul or peering of Signalling Connection Control Part user messages and service interface across an IP network.