Sigtran is a technique used in service provider IP transport networks in order to carry SS7 (Signalling System number 7) messages between network nodes. This is largely due to the fact that SS7’s lower layers rely on a TDM (Time Division Multiplexed) bearer, such as an E1 or T1 link. Sigtran uses a User Adaptation layer in order to support the regular SS7 border primitives sent between layers of the SS7 protocol stack. In turn, the User Adaptation layer packets are transported across the IP network using SCTP (Stream Control Transmission Protocol) at the Transport Layer. There are various User Adaptation layers available, the choice of which is determined by how much SS7 functionality (in terms of layers) needs to be retained in the IP transport network. Options include SUA (SCCP User Adaptation), M3UA (MTP3 User Adaptation), M2UA (MTP2 User Adaptation) and M2PA (MTP2 Peer to Peer Adaptation).