Hopping the Networks

Some companies might consider sending voice over their frame-relay network, then over an internal IP network, and perhaps even over the Internet. To-day's FRADs and gateways theoretically make this possible, but the practical benefits are unclear.

An IP gateway could encapsulate voice into IP packets: Workers within a company could converse from PC to PC. The IP packets could then go to a FRAD. The FRAD would enclose the IP voice packets like a nested box within a frame-relay packet, then across the company's WAN to a remote site. There, another FRAD would strip off the frame-relay envelope and send the IP packet across the LAN. At the destination PC, the IP packet would disappear, and the message would turn into voice.

The capability exists to take this one step further. Most service providers can connect their frame-relay networks to the Internet so that, along the way, the voice data could jump off onto the Internet.

That's the potential; the practical aspects of network hopping are plagued by the high overhead of all that packing and unpacking. Today's codecs might compress the voice data to 8 Kbps; however, an extra 7 Kbps in overhead might be needed to send the data, according to TeleChoice's Tom Jenkins. The result is more degradation in voice quality than what users already experience with voice over frame relay or IP.

Jenkins adds that he doesn't expect network hopping to be significant in the evolution of voice over data. "Companies are more likely to choose frame relay or IP," he says.

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Internetwork Voice Latency

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Network-hopping your voice traffic is possible, but the latencies it introduces make it impractical.