In this section:
Point Code EmulationTM (PCE) is an optional Level 4 (L4) software application on the DSC, used to significantly simplify and reduce the risk of switch migration activities.
PCE is a Level 4 (L4) software application that Ribbon offers as an option with the DSC. This application is used to divide a network into two different addressing spaces for the reuse of point codes (PCs). These two addressing spaces are typically referred to as the public network and the private network. PCE can be used for Integrated Services Digital Network (ISDN) User Part (ISUP) and for Transaction Capabilities Application Part (TCAP) messaging.
This application ensures that service providers have the ability to transparently configure and manipulate SS7 nodes without disruption or reconfiguration of the public SS7 network. PCE is similar to network address translation (NAT) on an IP network. Similarly to NAT, PCE allows computers to use one IP address when accessing the Internet and many network elements to appear to the network as one or more shared point codes (PCs).
PCE is a cost effective solution for expanding networks where new PCs are rare and expensive by minimizing the number of direct SS7 links to an STP pair. Nodes within the private network are accessed using trunk-based routing for ISUP traffic and Transaction Identifiers with GTT routing for TCAP traffic.
The benefits of PCE include the following:
The enhanced version of PCE supports a second private Network Appearance (NA) that can be used as a swing-box in a cut-over environment for migration to next-generation solutions and to address the cap-and-grow issue. PCE allows two switches on the private domain to share the same PC, thereby, giving operators the ability to manipulate nodes without disrupting the network.
The DSC supports 1,024 Public Gateways. The Public Gateways are the private network entry point codes that the Public Nodes use as their Destination Point Codes.
Typically, all nodes in the public network that interact with PCE require an associated Public Node UI object. The Non-Member Routeset Support feature allows nodes in the private network (or networks for Enhanced PCE) with cluster, network, or default routeset definitions to respond to TCAP queries from nodes in the public network that are not defined in the PCE as Public Nodes.
For more information about the Non-Member Routeset Support feature, refer to Public Node and General Configuration.
For information about configuring PCE, refer to Configuring the Point Code Emulator.
The following figures show an example of the ISUP call flow and the ISUP message sequence for the corresponding network configuration.
The ISUP message flow for the preceding figure (Figure Example of ISUP Message Sequence) is as follows:
TCAP message handling in PCE is different than the ISUP message handling because there is no CIC value to determine which internal switch to use. TCAP transaction management includes the following two transaction types:
At the heart of the TCAP handling technology is a temporary database used to hold the TCAP transaction IDs, information known about each transaction and how the transaction is distributed across the various CPUs (VMs) on both mates of an STP pair.
The operator is given a flexible set of routing possibilities to handle a new TCAP query or transaction as it crosses PCE. TCAP queries, starting from the private side of PCE (internal-initiated), are added to the database and sent to the public destination. Any subsequent messages on the same TCAP transaction use the same end points as stored in the database.
When PCE receives a public-initiated TCAP query message, PCE processes this message in the order indicated in the following list:
If the other methods have not routed the message, PCE may be configured to broadcast the message to all internal nodes and await a positive response.
If the broadcast is not enabled, the MSU cannot be routed and an SCCP relay error handling is performed.