A Signaling Gateway is a network component responsible for transferring signaling messages (i.e. information related to call establishment, billing, location, short messages, address conversion, and other services) between Common Channel Signaling (CCS)

Common Channel Signaling

In telephony, Common Channel Signaling , in the US also Common Channel Interoffice Signaling , is the transmission of signaling information on a separate channel from the data, and, more specifically, where that signaling channel controls multiple data channels.For example, in the public switched...

 nodes that communicate using different protocols and transports. Transport conversion is often from SS7 to IP

Internet Protocol

The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...

.

A SIGTRAN

SIGTRAN

SIGTRAN is the name, derived from signaling transport, of the former Internet Engineering Task Force working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for Signaling System 7 and ISDN communications protocols....

 Signaling Gateway is a network component that performs packet level translation of signaling from common channel signaling (based upon SS7) to SIGTRAN signaling (based upon IP). The concept of the SIGTRAN signaling gateway was introduced in the IETF

Internet Engineering Task Force

The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...

 document: RFC 2719: Architectural Framework for Signaling Transport.

A signaling gateway can be implemented as an embedded component of some other network element, or can be provided as a stand-alone network element. For example: a signaling gateway is often part of a softswitch

Softswitch

A softswitch is a central device in a telecommunications network which connects telephone calls from one phone line to another, typically via the internet, entirely by means of software running on a general-purpose computer system...

 in modern VoIP deployments. The signaling gateway function can also be included within the larger operational domain of a Signal Transfer Point (STP)

Signal Transfer Point

A Signal Transfer Point is a router that relays SS7 messages between signaling end-points and other signaling transfer points . Typical SEPs include service switching points and service control points . The STP is connected to adjacent SEPs and STPs via signaling links...

.

Protocol conversion gateways can also convert from one network operational paradigm to another – for example, SIP

Session Initiation Protocol

The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...

 to ISUP

ISDN User Part

The ISDN User Part or ISUP is part of the Signaling System #7 which is used to set up telephone calls in Public Switched Telephone Networks...

 for call control , SIP to TCAP

Transaction Capabilities Application Part

Transaction Capabilities Application Part, from ITU-T recommendations Q.771-Q.775 or ANSI T1.114 is a protocol for Signalling System 7 networks. Its primary purpose is to facilitate multiple concurrent dialogs between the same sub-systems on the same machines, using Transaction IDs to differentiate...

for address translation, or SIP to MAP for location or presence.