SRI Send Routing Information

Last updated on Jul 6, 2023

SRI (Send Routing Information) is a signaling message or procedure used in telecommunication networks, specifically in the context of the Signaling System No. 7 (SS7) protocol suite. SRI is used to request and obtain routing information for a specific destination in the network, typically in the context of mobile networks for routing signaling messages related to mobile subscribers.

Here's a detailed explanation of SRI and its significance:

Signaling System No. 7 (SS7):

SS7 is a widely used signaling protocol suite employed in telecommunication networks for the exchange of signaling messages between network elements. It provides the infrastructure for various telephony services, including call setup, call routing, and network management.

Routing Information:

In a telecommunication network, routing information refers to the details necessary to determine the correct destination for a signaling message. This includes information such as the network point codes (NPCs) or signaling point codes (SPCs) that uniquely identify network elements, routing tables, or databases that store subscriber information.

SRI Procedure:

The SRI procedure involves the exchange of signaling messages between network elements to request and obtain routing information for a specific destination. The procedure typically includes the following steps:

SRI Request: A signaling node, such as a Mobile Switching Center (MSC) or a Service Control Point (SCP), initiates an SRI request to obtain routing information. The SRI request message includes the destination address or number for which routing information is required.
Routing Lookup: The receiving node, typically a home location register (HLR) or a database element, performs a routing lookup based on the received SRI request. It retrieves the routing information associated with the destination address and prepares a response.
SRI Response: The node that performed the routing lookup sends an SRI response message back to the requesting node. The SRI response includes the requested routing information, such as the NPC, GT (Global Title), or other relevant data.
Routing Message Forwarding: Once the requesting node receives the SRI response, it can use the obtained routing information to properly route subsequent signaling messages or take further actions based on the received information.

Routing Database Lookup:

The SRI procedure typically involves a lookup operation in a routing database, such as an HLR, Visitor Location Register (VLR), or Home Subscriber Server (HSS). The routing database stores subscriber-related information, such as the location and profile of mobile subscribers, which is used for proper call routing or service provisioning.

Mobile Network Signaling:

In mobile networks, the SRI procedure is commonly used to obtain routing information for routing Mobile Application Part (MAP) messages related to mobile subscribers. It helps identify the correct network elements involved in processing calls, SMS, or other services for a particular mobile subscriber.

Number Portability:

SRI is also used in number portability scenarios. When a subscriber switches from one service provider to another while keeping the same phone number, the SRI procedure is used to determine the new network elements associated with the ported number.

SS7 Signaling:

The SRI procedure is part of the SS7 signaling protocol suite, which is widely used in traditional telecommunication networks. SS7 provides signaling functions that enable call setup, routing, and management between network elements, and the SRI procedure is a fundamental component of this signaling system.

The SRI (Send Routing Information) procedure in SS7 allows network elements to request and obtain routing information for specific destinations in telecommunication networks. It plays a critical role in ensuring proper call routing, number portability, and service provisioning for mobile subscribers.