SIGTRAN

SIGTRAN is the name, derived from signaling transport. The SIGTRAN protocols are an extension of the SS7 protocol family. It supports the same application and call management paradigms as SS7 but uses an Internet Protocol (IP) transport called Stream Control Transmission Protocol (SCTP), which is used to carry SS7 signaling over IP.

The SIGTRAN protocols are: SCTP, IUA, M2PA, M2UA, M3UA, SUA, V5UA and DUA.

M2PA provides an SCTP adaptation layer for providing an SS7 MTP signaling link over an IP network. It is specified in 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. It is specified in RFC 3331.

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. It is specified in RFC 4666.

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. It is specified in RFC 3868.

MTP2 peer-to-peer adaptation layer (M2PA)

M2PA defines a protocol supporting the transport of SS7 MTP3 signaling messages over IP, using the services of the SCTP. M2PA allows for full MTP3 message handling and network management between two SS7 nodes communicating over an IP network.

M2PA supports:

– seamless operation of MTP3 protocol peers over an IP network connection;

– the MTP2/MTP3 interface boundary, management of SCTP transport associations and traffic instead of MTP2 links;

– asynchronous reporting to management of status changes.

The MTP specification requires that each node with an MTP3 layer is represented by an SS7 point code. In other words, each IP signaling point must have a separate SS7 point code.

M2PA receives primitives sent from MTP3 to its lower layer. These messages are processed or mapped to appropriate primitives at the M2PA/SCTP interface. In the same way, M2PA transfers primitives to MTP3 such as those used in the MTP3/MTP2 interface. Each M2PA link corresponds to an SCTP association. From a monitoring and measurement point of view, M2PA links are handled in the same way as standard SS7 TDM links.

Hence, signaling messages between SS7 nodes communicating over IP are measured and monitored in the same way as in a SS7 TDM network. All SS7 MTP features implemented within SURPASS hiS 700 are supported withM2PA as well.

M2PA can be used between:

– signaling gateways of the same or different networks,

– a signaling gateway and any SIGTRAN M2PA enabled end node.

MTP3 user adaptation layer (M3UA)

The MTP3 user adaptation layer (M3UA) has been defined in such a way that it provides the same services as MTPL3 to the upper layers (ISUP, SCCP). The procedures and message formats of the M3UA protocol are according to the requirements of the RFC3332 (recently RFC4666).

SCCP user adaptation layer (SUA)

The SCCP user adaptation layer (SUA) transports SCCP user messages over the IP network using the services of SCTP. SUA can thus be used for the transport of SCCP based signaling such as MAP (e.g. SMS), INAP, CAP, ... but not ISUP.