Where should traffic shaping occur?
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Vendors are adding traffic management and shaping capabilities to various network components to help network managers meet service-level agreements with their internal users. These capabilities are attracting closer scrutiny, as co-existing, networked applications with different behaviors become numerous and some start to take greater priority in user organizations than others.
There are three logical places on an enterprise's premises for such traffic management to take place: in the router, in a separate device on the LAN side of the router, and in a separate device on the WAN side of the router (such as an intelligent DSU/CSU).
At first blush, the router might seem the best place to do the job, because it uniquely has a view of both LAN and WAN traffic. Then again, router real estate is expensive, and it would seem that the router has plenty of important tasks to handle without consuming valuable CPU cycles for traffic shaping. Consequently, we are seeing adjunct tools becoming available on both the LAN and WAN sides of the router.
LAN-based traffic-management tools preprocess the traffic before it reaches the router, leaving the router to do what it does best: determine best paths through a network from source to destination, and forward packets. On the plus side, LAN-based traffic shapers see all, outbound traffic and thus make decisions based on the " whole picture. " The downside is that in this scenario, there is little explicit data about congestion available from the WAN. The best information that gets through is TCP window size information.
We'll take a look at WAN-side traffic-shaping pros and cons next time.
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.
Frame Relay archive
Network World on Frame Relay newsletter, 12/20/99