Speeds And Feeds
No single test can completely characterize the behavior of today's LAN switching solutions. To provide the most thorough analysis of the products in this review, we divided testing into three stages: lab testing with Netcom Systems' Smartbits; real-world testing on the University of Wisconsin's campus fiber plant (see "Real World, Real Fibers," page 82; and live-network performance- and stress-testing at the lab of Neal Nelson & Associates (1 (312) 755-1000) (see "From the Lab of Neal Nelson & Associates").

For the first stage of our testing, we assembled a large test bed of Netcom Smartbits. Comprised of eight Smartbits chassis, our test bed was able to benchmark up to 120 ports of 10/100-Mbps Fast Ethernet and 24 ports of Gigabit Ethernet. We picked 11 of the most strenuous and revealing benchmarks from Netcom's suite of benchmarking tools, and put each gigabit switch up against the bit-blasting fury of the Smartbits testers.

Our first benchmark used Netcom's Smart Applications. We tested throughput between pairs of ports on the device under test (DUT). We measured throughput in packets per second for 64-, 512- and 1,518-byte packet sizes, thus determining the DUT's capacity to switch locally between multiple Fast Ethernet ports. This is the most forgiving of the throughput tests because it is a half-duplex, one-to-one test. Each device was tested in the highest-density configuration the vendor could provide. The same benchmark was run in a full-duplex manner, effectively doubling the amount of traffic offered to the switch.

Our results are reported as maximum theoretical number and actual number of packets per second passed. You can see the results of these tests online at www.networkcomputing.com/916/916r1.html.

We then ran tests using Netcom's Advanced Switch Tests (AST). AST's X-Stream configures each port to talk to all other ports on the DUT; as many as 80 ports can be tested with the current version of AST. The AST benchmark is the most difficult benchmark a switch can undergo, as it puts considerable load on both the switching fabric and the buffers of the switch. We tested each device at wire speed for 30 seconds at 64-, 512- and 1,518-byte packet sizes. These results also can be found online.

After testing Fast Ethernet throughput, we moved on to Gigabit Ethernet performance. The same three tests run at 100 Mbps were repeated using Gigabit Ethernet interfaces on any switch that could support more than a single Gigabit Ethernet uplink. The results of our Smart Applications full-duplex test is shown on page 76; the results of our X-Stream gigabit test is at left. The charts for the other tests can be found in the online version of this review.

Several products had advanced Layer 3 routing features. We tested IP routing features using Netcom's VLAN Advanced Switch Tests (VAST), which perform X-Stream testing at Layer 3. We ran VAST for 30 seconds with 64-, 512- and 1,518-byte packets at 100 Mbps and gigabit speeds. The results from these tests also can be found online.