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SS7 protocol suite
SS7 protocols by OSI layer

INAP, MAP, IS-41...

Network MTP Level 3 + SCCP
Data link MTP Level 2
Physical MTP Level 1

M3UA stands for MTP Level 3 (MTP3) User Adaptation Layer as defined by the IETF SIGTRAN working group in RFC 4666 (which replaces and supersedes RFC 3332). M3UA enables the SS7 protocol's User Parts (e.g. ISUP, SCCP and TUP) to run over IP instead of telephony equipment like ISDN and PSTN. It is recommended to use the services of SCTP to transmit M3UA.

An open implementation of the M3UA standard can be found at OpenSS7's web site.[1]

Wireshark is shipped with a dissector for M3UA, sample packets can be found in Wireshark's wiki page, which shows ISUP Packet samples (including M3UA[2]


M3UA uses a complex state machine to manage and indicate states it's running. Several M3UA messages are mandatory to make a M3UA association or peering fully functional (ASP UP, ASP UP Acknowledge, ASP Active, ASP Active Acknowledge), some others are recommended (Notify, Destination Audits (DAUD)).


External links[edit]