Service providers can cut costs with SS7oIP by offloading data traffic from SS7 networks onto IP networks. For example, Short Message Service (SMS) data is saturating GSM service providers' SS7 networks. SS7 Over IP enables wireless service providers to rapidly deploy emerging IP-based services for the mobile Internet that freely interact with the legacy mobile infrastructure.

SIGTRAN is the name given to an IETF working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for SS7 and ISDN communications protocols . The most significant protocol defined by the SIGTRAN group was the Stream Control Transmission Protocol ( SCTP ) which uses the Internet Protocol (IP) as its network protocol.

SCTP is a reliable transport protocol operating on top of a potentially unreliable connectionless packet service such as IP. It offers acknowledged error-free non-duplicated transfer of datagrams (messages). Detection of data corruption, loss of data and duplication of data is achieved by using checksums and sequence numbers. A selective retransmission mechanism is applied to correct loss or corruption of data.

Benefits:

• Ease of deployment: When using signaling gateways (such as access service group [ASG]), there is no need to disrupt the existing SS7 network, and future enhancements are transparent.

• Less costly equipment: There is no need for further expensive investments in the legacy signaling elements.

• Better efficiency: SIGTRAN over an IP network doesn't require the physical E1/T1 over synchronous digital hierarchy (SDH) rings. Using new technologies like IP over SDH and IP over fiber, for instance, can achieve much higher throughput.

• Higher bandwidth: SIGTRAN information over IP does not constrain to link capacity as it does in the SS7 network. The IP network is much more flexible than the TDM-based legacy network.

• Enhanced services: Implementing a core IP network facilitates a variety of new solutions and value-added services (VAS).

RFCs

• RFC 3286 [1] -- An Introduction to the Stream Control Transmission Protocol

• RFC 3257 [2] -- Stream Control Transmission Protocol Applicability Statement

• RFC 2960 [3] -- Stream Control Transmission Protocol

• RFC 3873 [4] --Stream Control Transmission Protocol (SCTP) Management Information Base (MIB)

• RFC 3758 [5] -- Stream Control Transmission Protocol (SCTP) Partial Reliability Extension

• RFC 3436 [6] -- Transport Layer Security over Stream Control Transmission Protocol

SS7oIP / SIGTRAN Resources:

IEC SIGTRAN Tutorial [7]

IETF SIGTRAN Charter [8]

IEC SCTP Tutorial [9]

SCTP for beginners [10]

Opensource SIGTRAN project [11]

www.sigtran.org [12]

Linux Kernel SCTP Project [13]

SS7 Over IP [14]