Voice gets priority delivery at GST. Phone traffic over the LAN is a no-brainer, thanks to GST's gigabit backbone, and GST uses quality-of-service parameters there just to prevent bursts of voice traffic from clogging buffers and then dropping packets. It's in the WAN where QoS is most crucial. GST uses Cisco's Class-Based Weighted Fair Queuing/Low-Latency Queuing feature in its internal 1760 and 3725 routers, and built-in QoS features in its Cisco Catalyst 3550 and 6509 switches for prioritizing voice at the edge and the core.
The trick was ensuring that Cisco's QoS matched that of GST's Internet provider, AT&T. GST chose an AT&T CoS (class-of-service) profile that supported its real-time voice traffic, Smith says, giving voice 50 percent of the pipe and top billing. Synchronizing the QoS parameters was straightforward, since AT&T uses Cisco equipment in its backbone.
Next in line for bandwidth and delivery is network management and upcoming video traffic. "At this point, we don't treat any other applications besides these as critical," Smith says.
But voice isn't the end of the road for GST's VPN. Next year the company will add videoconferencing to the network to save on travel expenses to customer sites. "That allows our salespeople to connect and do demonstrations of our supply-chain solutions via videoconferencing, too," Meewes says.
And video will be easier to deploy than voice, Smith says, because it's not as sensitive to packet loss or delay. Still, GST will likely need to allocate a larger percentage of its bandwidth to the "high" class for video, he says. For now, it's at 25 percent, which is about 384 Kbps of a full T1 (1.54 Mbps) pipe.
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