About the IP Short Message Gateway

The IP Short Message Gateway (IP-SM-GW) implements transport layer interworking for SMS over IP. It is based on 3GPP TS 24.341, and implements suitable SMS interworking as part of GSMA IR.92 version 9.0


This document includes the following topics:

Topic Explains…​

Sentinel IP-SM-GW in an LTE network

How the IP-SM-GW fits into a network

Key Flows

Illustrative flows for key behaviour

Major Components

Major functional components

Support for GSM MAP

Versions of GSM/3GPP MAP in the IP-SM-GW

Overview of the TCAP Leg Manager

The TCAP Leg Manager subsystem of the Sentinel IP-SM-GW service

Sentinel IP-SM-GW in an LTE network

The IP-SM-GW interfaces to several network elements.

ipsmgw in network

Once a UE is IMS registered, and indicates support for receipt of SMS over IP, it may send and receive SMS through the IP-SM-GW. That is, the UE may use SMS over IP when registered via PS access networks, not only when registered via LTE. The IP-SM-GW also supports mobile-initiated USSD reports over IMS.

The IP-SM-GW performs a similar role to the VMSC, but for IMS registered UEs, rather than CS registered.

In order to aid understanding of the role of the IP-SM-GW, refer to Key Flows.

Major Components

The diagram below shows the major components for the Sentinel IP-SM-GW.

slee service view

The Sentinel Registrar and Sentinel IP-SM-GW are services running on the Rhino TAS platform, written using the Sentinel Framework. Third Party Registration support is provided by the Sentinel Registrar service. The core SMS flows of the IP-SM-GW are provided by the Sentinel IP-SM-GW service. The Cassandra DB appears in the diagram for each role it fulfills in the architecture (routing correlation and registrar data storage).

  1. to correlate the IMSI and Circuit Switched Routing Information

  2. to store Third Party Registration information. For more information refer to Sentinel Registrar Overview and Concepts

IMSI and Circuit Switched Routing Information correlation

The Sentinel IP-SM-GW uses a Cassandra Database to store and retrieve CS Routing Information. This means that any IP-SM-GW cluster member can process the MT Forward Short Message request regardless of the cluster member that processed the Routing Information for SM query.

This ensures that a deployment is simple from an SS7 addressing perspective, as only a single GT address is required.

Support for GSM MAP

The Sentinel IP-SM-GW supports GSM/3GPP MAP Phases 1, 2 and 2+ for MT SMS. It uses MAP Phase 2 for Mobile Originated SMS submission into the SMSC.

Protocol support is provided through the use of OpenCloud CGIN and OCSS7 stacks. For protocol compliance statements refer to CGIN Protocol Compliance and OCSS7 Compliance Matrix.

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