Toll Bypass

VoIP gateways provide a variety of basic features, including packetization (translating analog signals into digital IP packets), voice compression and decompression, control signaling and call routing. From a buyer's perspective, the key features to look for in a VoIP gateway include integration with an existing PBX and IP infrastructure, painless deployment through vendor support, extensive compatibility with both new VoIP equipment and the existing data network infrastructure. Other important attributes worth considering are PSTN failover (the ability to get to an analog line in case the VoIP connection goes down), true H.323 and SIP survivability (the ability to maintain VoIP connections through problem conditions), efficient multiplexing and NAT traversal and analog device support--all important usability concerns.

VoIP gateways can be based on either hardware or software. Hardware-based VoIP gateways--by far the most widely used approach--are available as standalone boxes, chassis cards or modules. Hardware VoIP gateways, while generally more expensive than their software counterparts, are usually preferred because they are more reliable, provide built-in interfaces and don't consume computer processing power.

Finding the appropriate VoIP gateway requires a close examination of three core variables. First, it's important to understand that the gateway's chassis size often dictates the unit's packet processing capacity. Sluggish processing leads to poor VoIP call quality, user complaints and, potentially, lost business. Second, the number of simultaneous VoIP calls that the gateway can handle is critical, so it's important to select a device that can keep pace with the network's call load. A good rule of thumb is to purchase a gateway that can handle a call load that's at least 20 percent greater than current levels. That way, the gateway can accommodate a reasonable amount of business growth without premature upgrading or replacement. Third, the number and variety of interfaces provided by the gateway is crucial for interoperability, since a lack of suitable ports can make connecting external equipment to the gateway a difficult, and sometimes impossible, task.