Application Example: Voice over IP

Application Example: Voice over IP

Overview

A number of companies manufacture equipment to enable voice traffic to be carried over packet-switched networks running IP. As standards have evolved on the IP networks in support of these VoIP applications, the functionality has been divided into discrete logical blocks including:

Media Gateways: which interconnect with PSTN switches and handle the compression and packetization of the voice traffic that is exchanged between IP and PSTN networks.
Media Gateway Controllers: which provide call control to media gateways to ensure they are connected via the appropriate circuits and switches in the PSTN.
Signaling Gateways: which interwork SS7 signaling information from the PSTN and comparable telephony signaling information required in the IP network.

Together, these three blocks form a distributed telephone switch on the IP network that is fully capable of interacting with the switches in the Public Switched Telephone Network (PSTN) to support two way Voice over IP applications. The distributed IP switch can forward SS7 (TCAP) queries to 800 or Local Number Portability (LNP) databases in the PSTN, and can send and receive ISUP or other SS7 messages that support call control.

Signaling Gateway in a Voice over IP Application

VoIP configuration diagram

Distributed Softswitch (Media Gateway Controller) architecture
Single point code (SEPs) or multiple point code (STPs) applications
2-way (VoIP) call flow

What products do we provide in this application?

SEGway™ Signaling Gateways: The SEGway Signaling Gateway is an ideal product for this distributed configuration. The SS7 stack, with its unique clustering capability, allows the IP network provider to conserve valuable point codes by distributing the stack processing across multiple CompactPCI® gateways.

To the PSTN, the distributed IP switch solution can appear as a single SS7 node or point code, despite the number of IP components in the network. In the event of a link or node failure, traffic is immediately rerouted, and the link and node management is handled by the remaining gateways without a disruption of service. For VoIP providers, the ability to provide seamless, reliable interworking between IP networks and the PSTN gives them unprecedented service quality dependability and a competitive edge over companies without the distributed software architecture.

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