WAN-side traffic shaping

There are certain advantages to shaping traffic on the WAN side of a router.

We mentioned last time that there are several places on an enterprise's premises where traffic shaping could take place. We noted that offloading traffic-shaping functions from the router and running them in a LAN-side device has the benefit of making decisions on all outbound traffic from a site, but carries the downside of being able to see very little WAN congestion information.

Traffic shaping refers both to smoothing the bursty rate at which network traffic arrives on an access circuit, and to prioritizing traffic according to corporate policy. In an integrated packet network, such as frame relay, ATM or IP, such QoS capabilities enable various traffic types to get their fair share of any available bandwidth, based on an organization's policy. You don't want FTP and Web browsing to wreak havoc with enterprise resource planning applications or packet-voice traffic, for example.

Running traffic-shaping capabilities on the WAN side of a router, such as in intelligent DSU/CSUs, enables the device to glean extensive information concerning the state of the frame relay (or ATM, or other WAN) connection.

This includes congestion information based on frame relay FECN and BECN bits, for example - data that many routers ignore. Because WAN-side devices can sense network congestion on the WAN access circuit, which is usually slower and more expensive than the LAN side of the network, they can actively employ adaptive techniques for controlling WAN network traffic to ensure that business-critical applications receive required bandwidth.

In upcoming newsletters, you'll hear arguments from vendor proponents of traffic shaping in different spots in the network.

Steven Taylor, consultant and broadband packet evangelist, and Joanie Wexler, an independent networking technology editor and writer, team up to bring you this analysis and commentary. Taylor specializes in education and market analysis, and Wexler adds incisive reporting and research. For more detailed information on most of the topics discussed in this newsletter, connect to www.webtorials.com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP.

Feedback and additional topic ideas are welcome. Please contact taylor@webtorials.com or joanie@jwexler.com.

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