Variant and Protocol Conversion

Overview

The Level 4 Converter is a value-added addition to the DSC. This converter enables the conversion of SS7 L4 traffic such as Integrated Service Digital Network User Part (ISUP) and Signaling Connection Control Part (SCCP) messages and their parameters between two SS7 variants. Despite standards being in place for SS7 networks, there are over 100 different SS7 variants throughout the world. Not only can the SS7 variants be distinct, but they can also be dependent on the actual switch implementation. The Level 4 Converter can be configured to address the customization in its deployed networks.

An SS7-based variant requires its own MTP3 stack with Local Point Code (LPC) residing on the DSC. Each MTP stack deployed has a Local Point Code (LPC) in its given network. The IP-based variant requires the Signaling Gateway (SG) to support a given IP protocol such as MTP3 User Adaptation Layer (M3UA) or SCCP User Adaptation Layer (SUA). Customer IP switches or applications can select the necessary SG IP protocol based on their implementation requirements.

The Level 4 Converter forms a network boundary. It is unlikely that the point codes in one network variant are compatible with the point codes in the other network. The Level 4 Converter assigns a network switch with a mirror point code that complies with the other network’s standards. For each mirror point code created that differs from the local point code (LPC) of the corresponding DSC’s MTP3 stack, a Virtual Node (VNode) of the same point code value is created in the mirrored network. Mirror point codes are also used to resolve point code conflicts where a point code in a given network is already defined in the other network.

The Level 4 Converter converts SCCP and ISUP messages. This product does not convert the payload of the SCCP messages. The Level 4 Converter can be deployed in Global System for Mobile Communications (GSM) network because ITU Transaction Capabilities Application Part (TCAP) and Mobile Application Part (MAP) messages are used in both ANSI-based and ITU-based networks.

MAP services typically use the TCAP protocol as the SCCP payload. The Level 4 Converter maps PCs at the SCCP level to facilitate communication between the two dissimilar networks but leaves the SCCP payload unaffected. No TCAP conversion is performed.

For information about configuring the Level 4 Converter, refer to Configuring the Level 4 Converter.

Supported Conversions

The Level 4 Converter handles a single conversion between two variants. The supported conversions include:

• ANSI and ANSI Conversion
  
  
• ITU and ITU Conversion
  
  
• ANSI and ITU Conversion
  
  
• Pakistan and ITU Conversion
  
  
• Pakistan and India Conversion
  
  
• New Zealand and ITU Conversion
  
  
• Japan NTT and ITU Conversion
  
  
• Japan TTC and ITU Conversion
  
  
• China and ITU Conversion

For added flexibility, the default conversion rules can be dynamically modified to pass through or discard messages and parameters.

The Level 4 Converter is deployed in the following two configurations:

• SS7 to SS7
  
  
• SS7 to IP-based SS7

Supported Link Types

The Level 4 Converter supports all link types from MTP3.

For a description of link types, refer to Supported Signaling Link Types.