Table of Contents:

Definition and Overview

1. The Role of the Media Gateway in the Converging Network

2. Testing a Device Control Interface

3. Verifying Voice Paths across Dissimilar Network Types, a.k.a. Trunk Testing

4. Measuring Voice Quality across a Media Gateway

Self-Test

Glossary

PDF of this tutorial

Key Features and Benefits
The media gateway will be the most prolific component in the next-generation network. It is responsible for converting today's time division multiplexing (TDM) voice circuits into tomorrow's voice packets. Circuit-switched and packet-switched voice networks must interconnect, creating the need for media gateways as a fundamental component of multi-technology, converging networks. Media gateways are the "glue" at the bearer channel level between these two disparate network types.

Carrier Requirements
Carriers have requirements at several levels that must be addressed when deploying packet-based voice technology. Some of these are as follows:

• Can the media gateway be easily connected to the voice trunks that are already deployed in the network?
• Can the gateway be interconnected to existing packet infrastructure (ATM, IP/ATM, IP)?
• Will deployment of this gateway save space (and hence power and cooling) because the packaging is denser than existing Class-5 or Class-4 technology?
• Will I experience manpower savings because call and service control can be concentrated in fewer locations in the network rather than disbursed?

Media gateway density, measured as either digital signal (DS)–0s per rack, per square foot, or per dollar are all important metrics that a carrier uses when making decisions about deploying packet technology. With the revenue associated with voice calls declining, the carrier must maximize the utilization of existing facilities while minimizing the costs associated with deploying and maintaining new technology.

Customer Expectations
What do customers of the carrier expect? It's pretty simple. They expect that their call will go through and that they will receive the same level of voice quality that they currently have with today's PSTN, i.e., toll quality. Give a customer anything less than what they have today, and a carrier will quickly experience a rapid decline in revenue as customers move to its competitors.

Do customers really care if their calls are carried over today's PSTN or tomorrow's packet networks? Probably not, as long as the above criteria are met. Therefore, the carrier has to ensure that its network meets a minimum voice quality of service (QoS) and that its chosen media gateway vendors can also meet this criteria.