VoIP islands connect with WAN gateways

VoIP islands can be connected by technologies such as gateways and WAN optimisation.

VoIP islands are pretty much the de facto standard these days. Deploying VoIP in various locations usually requires a separate PBX at each and connecting those over the PSTN, ultimately negating some of the benefits VoIP brings to the table.

But at Interop Las Vegas last week, VoIP experts discussed how to use WAN optimisation and gateway techniques to keep VoIP islands connected, essentially bridging VoIP from headquarters to other locations using the WAN and Internet without the need for additional PBXs.

"What we have, by and large, are islands of VoIP," said Jay Brandstadter of JRB Consulting, adding that VoIP deployments are set up in different locations with IP PBXs connected via legacy trunks.

Gateways, Brandstadter said, offer connectivity to the branch from headquarters, meaning that the branch can remote the PBX and voicemail modules and get those services directly from headquarters.

Essentially, the gateway sends voice traffic between symmetric gateways on either side of the WAN. As a backup, the traditional PSTN can also be used, in case WAN links are out or degraded.

Along with voice gateways, WAN optimisation tools can connect VoIP islands while also boosting VoIP performance across long-distance WANs.

Michael Peachey, a product manager with Juniper Networks, said, however, that users must first prepare the WAN for VoIP. Things to note are that voice traffic does not behave like data, end users have no tolerance for low-quality voice, and voice traffic requires priority to keep its real-time nature.

Using WAN optimisation techniques such as QoS, traffic from other applications can be reduced with compression and caching and a specific amount of bandwidth can be devoted to VoIP.

"The goal of WAN optimisation is to fill the pipe," Peachey said.

Also, VoIP headers can be compressed to ensure high performance.

Overall, Peachey advised the use of QoS or policy-based multi-paths to prioritise voice. Policy-based multi-paths are best at sites with multiple WAN links; they allow users to select paths based on specific applications and to divert traffic to an alternate path if the link fails or degrades.

The benefits of using such techniques for VoIP are many, Peachey said. They help companies realise cost benefits by using acceleration and optimisation, and they improve voice quality and increase service availability to thwart dropped or delayed calls.

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