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.