Reducing Network Broadcast Traffic with Fastswitches

By Howie Fenton

DDB Needham Dallas/Tracy-Locke, a production orientated advertising agency in Dallas, Texas found out that in a busy network, collisions can shut you down. The 600 employees work on Macs connected with Ethernet 10Base-T and AppleTalk to access files on Apple Workgroup and other fileservers, output files to a variety of black-and-white and color printers, access administrative information on VAX minicomputers, and send e-mail. Their clients include Pepsi, American Airlines, GTE, and Budget Rent-a-Car.

Originally, all workstations and devices were attached to Farallon 10Base-T hubs, which were interconnected through an eight-port repeater. As its business expanded, they added new employees and workstations which increased network traffic and the latency at the repeater. Packets began to time out before they reached their destination, and print jobs aborted before completion.

Worse, the busiest segments became so congested that the repeater would automatically shut them down for several minutes, numerous times a day. "We could tell when excessive collisions were occurring because a red light would begin flashing on the repeater port where the overloaded hub was attached," says Jan Bordeleau, Macintosh network manager. "That meant the repeater was autopartitioning the segments, which locked users out of the network intermittently. I estimate that our busiest network slowed to a crawl about twice a day."

Consulting with a reseller, the DDB Needham Dallas office determined that network traffic had exceeded acceptable thresholds for the repeater, which broadcasts every packet through all its ports. As Bordeleau envisioned the problem: "Every hub was yelling across the network, creating a huge echo chamber."

The agency decided to segment network traffic by replacing the 10Base-T hubs in its three most troubled workgroups with Grand Junction FastSwitch 10/100 and 10/100 AG switches. This strategy reduces overall network traffic because the Grand Junction switches forward only those packets destined for another segment.

DDB Needham Dallas installed FastSwitch 10/100 switches in the Studio creative group, the Teleworks broadcast video recording group, and the creative groups for two major clients. "Installation was fast and easy," says Bordeleau. "We simply disconnected the cables from the 10Base-T hubs and reconnected them to the 10 Mbps private Ethernet ports on the FastSwitch 10/100. We'll connect our file servers to the remaining 100 Mbps Fast Ethernet ports when Fast Ethernet cards for our Apple servers become available. Because the FastSwitch 10/100 workgroup switch has twice as many ports as the 10Base-T hub, we were able to halve the number of boxes."

By replacing the 10Base-T hubs in the busiest workgroups with FastSwitch 10/100 switches, DDB Needham gave workstations their own private 10 Mbps Ethernet segments. Overall network performance has improved because of the reduction in broadcast packets.

The cessation in printing problems was instantaneous. "The automatic repartitioning by the repeater stopped as soon as we installed the FastSwitch 10/100 switches," reports Bordeleau. "Our network jams on those segments completely disappeared."

A side benefit of the installation: Users on other segments--those that continue to use 10Base-T hubs instead of switches--also report faster network access. "The FastSwitch 10/100 improved performance throughout the network by reducing the number of broadcast packets," says Bordeleau.

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