Getting your LAN up to speed

ITworld.com –

If you haven't yet upgraded your LAN infrastructure to switched 100 Mbps equipment, there is probably no better time to do so than now. Just to be clear here, I'm talking about getting every desktop on a full duplex 100 Mbps switched link. The actual backbone -- for connecting wiring closets to your data center, or interconnecting buildings on a campus -- would be Gigabit Ethernet, 1000Base-Sx, which runs over two multimode optical fibers.

There's no other LAN technology or topology that makes sense today. It costs you more to maintain that aging token ring or FDDI infrastructure than it will to upgrade. And residual 10 Mbps hubs are a bottleneck and may be a source of problems, like looping, so do yourself a favor and get rid of them.

The industry would have you believe that 10/100 switches have become commodity products. That's not completely true. While you can generally buy these switches today for less than $100 per 10/100-switched port, there are some other key factors to consider. Here are three to keep in mind.

  • Don't just follow the leaders. Cisco's Catalyst 5000 series and 3Com's SuperStack II series are the leading sellers, and both are fine switches, but I've found that they have some subtle limitations. Extreme Networks, Foundry Networks, and Hewlett-Packard also offer super switches, and ought to be on your short list.
  • You can overload any switch. There is no such thing as a switch that never drops packets. That's because of the way LAN switches work: whenever too many inbound users concurrently contend for the same outbound port -- the link to your data center, say, or the link connecting your main email server -- there can be an overload and lost data. This brings us to the last point.
  • You've got to effectively manage your switched LAN infrastructure. Most worthwhile 10/100 switches today have built-in SNMP agents that include some support for the RMON MIB (a remote monitoring management information base). But the remote monitoring should be easy to enable, and the vendor should offer you an affordable Windows application that can monitor this RMON data when you buy the switch. That leaves out Cisco and 3Com; figuring out RMON on a Catalyst switch is too often an exercise in futility, thanks to Cisco IOS's command-line interface, and 3Com doesn't offer an affordable mechanism for monitoring the switch's RMON data.

The bottom line: Don't listen to the hype that touts "non-blocking" and "wire speed" performance. Don't pay more than $100 per port. And ask the switch vendor to show you exactly how to monitor the switch's built-in RMON reporting.

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