Level 4 Converter System Overview

Overview

Often, the point codes in one SS7 network are incompatible with the point codes in the other SS7 (or IP network). The Level 4 Converter forms a network boundary. 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 Ribbon DSC - SP2000 MTP3 NA, a Virtual Node (VNode) of the same point code value must be 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 mapping between the network point codes and their associated mirror point codes are defined by creating Route Mappings in the home network’s SS7 Variant (refer to Creating and Configuring Route Mappings).

The DSC - SP2000 Platform support a maximum of 4000 Route Mappings (default value is 2,000) per each SS7 Variant with the exception of the ANSI (ISUP or SCCP) to ITU (ISUP or SCCP) and visa versa. For these two SS7 Variants, a maximum of 200 Route Mappings (default value is 200) are supported and the configured Route Mapping Limit cannot be modified.

Conversion Configuration

The Level 4 Converter is deployed in the SS7 to/from SS7 conversion configuration. Past deployments performed a less common SS7 to/from IP-based SS7 conversion, which is no longer supported. For more information on IP-based SS7 conversion configuration, see section IP-based SS7 Conversion

An SS7-based variant requires its own MTP3 Network Appearance (NA) residing on the Ribbon DSC - SP2000. Each MTP3 NA deployed has a Local Point Code (LPC) in its given network.  The conversion supports all DSC - SP2000 link type including standard SIGTRAN M3UA and SUA.

The Level 4 Converter converts SCCP and ISUP messages. This product does not convert the payload of the SCCP level 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.

Further SCCP/TCAP-level conversions are performed by other Ribbon products. For information about these products, contact Customer Support.

Network Architecture

The Level 4 Converter is deployed in a distributed configuration on n (typically, n=2) VMs over a mated-pair of Signaling Transfer Points (STPs). Each STP stack is independent of the others.

Level 4 Converter System Architecture (Logical View - Example SS7 to SS7)

Messages between networks are routed directly by the STPs. Only traffic that is destined for the other network is processed by the Level 4 Converter (see the following figure and Figure Traffic Routing (SS7 to/from IP-based ).

Traffic Routing (SS7 to/from SS7)

IP-based SS7 Conversion

The IP-based variant requires the Signaling Gateway 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 Signaling Gateway IP protocol based on their implementation requirements.

Traffic Routing (SS7 to/from IP-based)