Description
The Short Message Control Protocol (SM-CP) is a specific application protocol defined within the 3GPP CAMEL (Customised Applications for Mobile network Enhanced Logic) standards. It operates between the CAMEL Service Environment (CSE)—which hosts the intelligent network service logic—and the network entity handling SMS, typically a Short Message Service Center (SMSC) or an IP Short Message Gateway (IP-SM-GW). SM-CP is used exclusively for Mobile Terminated (MT) SMS scenarios under CAMEL control. Its primary function is to allow the CSE to intervene in the SMS delivery process, enabling services like SMS screening, charging, routing modification, and notification.
Architecturally, SM-CP is part of the CAMEL Application Part (CAP) protocol suite. When an SMSC is about to deliver an MT-SMS to a subscriber who has a CAMEL subscription for SMS, it triggers a dialogue with the CSE. This is done by sending an initial SM-CP message, such as "ConnectSMS," to the CSE. This message contains key information about the SMS, including the called party number (recipient), calling party number (originator), and the SMSC address. The CSE, running its service logic (e.g., a gsmSCF), can then analyze this information and instruct the SMSC on how to proceed. It does this by sending back SM-CP operation responses, which can command the SMSC to continue with delivery, release the transaction (block the SMS), modify parameters like the destination address or charging information, or request to be notified of the final delivery outcome.
The protocol works in a transactional, request-response manner. Key operations include "ConnectSMS" (initiation), "FurnishChargingInformation" (to send charging data), "ReleaseSMS" (to terminate), and "EventReportSMS" (for notifications). Through these, the CSE can implement complex services. For example, a parental control service could use SM-CP to screen messages based on originator, blocking those from unknown numbers. A premium content service could use it to apply specific charging rates before delivery is attempted. The protocol ensures that the intelligent network's service logic is seamlessly integrated into the SMS delivery path without requiring modifications to the core SMSC itself, adhering to the CAMEL philosophy of separating service logic from switching functions.
Purpose & Motivation
SM-CP was created to extend the power of the Intelligent Network (IN) concept to the Short Message Service. Prior to CAMEL control, SMS was a basic transport service with limited network-based control; services like screening or special charging for SMS required proprietary SMSC features. SM-CP solved the problem of applying standardized, operator-defined logic to SMS delivery in real-time, enabling a new class of value-added services.
The motivation stemmed from the commercial success of SMS and the desire to monetize and control it further. Operators wanted to offer services like SMS firewalls, sponsored messaging, or location-based SMS routing. The CAMEL framework already provided this for voice calls (via CAP for calls), and SM-CP filled the gap for the messaging domain. It addressed the limitation of a "dumb pipe" SMS delivery by providing a standardized hook for service logic execution, allowing for service creation independent of switch vendors.
Historically, introduced in CAMEL Phase 3 (3GPP Release 5), SM-CP allowed GSM and UMTS operators to deploy consistent SMS-based services across their networks. It enabled the same service platform (CSE) to control both voice and messaging services, simplifying operations. The protocol's creation was driven by the need for flexible service control, enhanced charging models for premium SMS, and regulatory requirements like lawful interception for SMS, all within a standardized framework that ensured interoperability between network equipment from different manufacturers.
Key Features
- Enables CAMEL service control for Mobile Terminated SMS delivery
- Defines a set of CAP operations specific to SMS (e.g., ConnectSMS, ReleaseSMS)
- Allows real-time SMS screening, routing modification, and specialized charging
- Supports event reporting for SMS delivery status back to the service logic
- Operates between the CAMEL Service Environment (CSE) and the SMS handling entity (e.g., SMSC)
- Facilitates the creation of value-added SMS services without modifying core SMSC platforms
Evolution Across Releases
Introduced as part of CAMEL Phase 3, defining the initial Short Message Control Protocol for MT-SMS. The architecture established the dialogue between the gsmSCF (in the CSE) and the gsmSSF or IP-SM-GW, specifying the initial CAP operations like ConnectSMS to allow service logic invocation during SMS submission to the SMSC.
Defining Specifications
| Specification | Title |
|---|---|
| TS 23.078 | 3GPP TS 23.078 |
| TS 29.078 | 3GPP TS 29.078 |