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Systems | Signaling Gateway

A Signaling Gateway transports application signaling from an SS7 network to an IP network. It serves to bridge the legacy public switched telephone network (PSTN) with the packet switched next-generation network (NGN). When used in conjunction with softswitches, media gateways, application servers and media servers, a Signaling Gateway provides the call control functionality and service processing capabilities of traditional PSTN switches.

Signaling Gateways are composed of SS7 and related SS7-over-IP (SIGTRAN) subcomponents. There are four types of Signaling Gateways:

M3UA-based: used for transferring ISUP information across SS7 nodes; can also be used for transaction-based services (such as Global Title Translation) by running SCCP over the M3UA gateway.
SUA-based: used for transferring transaction information (such as a database lookup) across SS7 nodes.
M2UA/M2PA-based: used for transferring SS7 links across SS7 nodes; at this point the SS7 element in the IP network typically becomes the equivalent of an IP-STP.
IUA-based: used for transferring ISDN information (Q.931) over IP.

Applications

The Signaling Gateway supports SS7 signaling for seamless integration of PSTN and IP networks. This convergence allows operators to reliably transport SS7 messages utilizing lower IP-transport costs while maintaining all the reliability of the traditional SS7 network.

Some of the other applications include:

Mobile short messaging/location-based services
Distributed switches
SS7 long haul and offload
GPRS integration
3G Wireless integration (WCDMA and CDMA 1x)
IP telephony gateways
Intelligent networking SCP
IP-based application service
International arbitrage gateways

Interfaces

A Signaling Gateway needs to support multiple interfaces as well as different country protocol variants. At the circuit-side, ingress support for T1/E1/J1 (and similar country-specific variants) on the bearers is required. At the packet-side, egress support for multiple physical mediums and signaling interfaces concurrently and 10/100/1000 Mbps link speeds are required. A Signaling Gateway also needs to support media termination and backhaul, such as when co-located with a Media Gateway. Support for both IPv4 and IPv6 is necessary.

Critical Features

High Availability

An absolute requirement since the Signaling Gateway becomes a critical element in the network and its failure would result in the loss of thousands of calls.

Performance

A Signaling Gateway handles multiple streams of call signaling information - and hence its ability to quickly translate back-and-forth between traditional SS7 and IP networks is vital to overall system performance. For applications that include transaction processing, a higher transaction-per-second metric is extremely important.

Standards-based API

Standards-based API for controlling the various subcomponents within the Signaling Gateway, including the housing system, individual PMC line cards, and host blades.

Control Plane Software

Control Plane Software is required for the proper functioning of a Signaling Gateway including multiple different country variants of the protocols. This includes either a TCAP or ISUP stack (TCAP, SCCP, ISUP, MTP3, MTP2), a SIGTRAN stack based on the Signaling Gateway personality (M3UA, M2UA, M2PA, SUA, IUA), and application protocols (MAP-3G/2.5G/2G, MAP-IS41, INAP and CAP).