Lab tests prove that most first-generation 10G Ethernet switches don't deliver anywhere close to 10 gigabits of throughput. But the latest backbone switches  do deliver more bandwidth than earlier gear that used link aggregation, and they do a better job of quality-of-service enforcement.

In Network World's first hands-on assessment of the new 10G Ethernet switches, we put boxes from five major vendors through a comprehensive set of performance tests - both 1 and 10 Gigabit flavors of Ethernet. Avaya, Force10 Networks, Foundry Networks, HP and Nortel accepted our challenge. Other major players went missing, citing various reasons (see "No shows" ).

Hardware gremlins plagued Nortel's devices, and we couldn't obtain valid results. For the remaining players, the results offer limited encouragement:

•  Force10's E1200 delivers true 10G bit/sec throughput with any frame size, a performance that earned it the Network World Blue Ribbon award.

•  Foundry's FastIron 400 and HP's ProCurve Routing Switch 9300m series (which HP buys from Foundry) achieved fast failover times.

•  Avaya's Cajun P882 MultiService Switch kept jitter to a minimum and dropped no high-priority packets in our QoS tests.

But, when all is said and done, none of these first-generation devices represent the perfect switch. Force10's E1200 aced the throughput tests, but its delay and jitter numbers are far higher than they should be. As for the others, they won't really be true 10 Gigabit devices until they get capacity upgrades.

While the 10 Gigabit performance results are disappointing, it's important to put those numbers in context. Few, if any, users are planning pure 10G Ethernet networks, so these devices support a variety of interfaces and other features useful for enterprise core networking, such as support for highly redundant components and multiple device management methods (see full feature listing - Excel file ). It's important to note that these switches did a pretty good job of handling tasks not directly related to 10G Ethernet, such as failover and QoS  enforcement.

To the tests

We evaluated switch performance with four sets of tests: 10 Gigabit alone; Gigabit Ethernet across a 10G Ethernet backbone; failover times; and QoS enforcement.

The main goal of our pure 10G Ethernet tests was to describe the basic forwarding and delay characteristics of the new technology. Would it really go at 10 gigabits? And how much delay and jitter would the new interfaces incur at that speed?

To answer these questions, we set up a test bed comprising a single switch equipped with 10G Ethernet interfaces and SmartBits traffic generator/analyzers from Spirent Communications (see How we did it ). All vendors supplied four 10G Ethernet interfaces for this event except Avaya, which supplied two.

We configured the SmartBits to offer traffic from more than 2,000 virtual hosts (more than 1,000 hosts in Avaya's case), representing the large number of devices attached to a typical 10 Gigabit switch.

We used three frame sizes: 64-byte frames, because they're the shortest allowed in Ethernet, and as such offer the most stressful test case; 256-byte frames, because they're close to the median frame length of around 300 bytes as observed on various Internet links; and 1,518 bytes, the maximum allowed in Ethernet and the size used in bulk data transfers.

Only one switch -- Force10's E1200 -- actually delivered true line-rate throughput (see Figure 1 ). Impressively, the E1200 moved traffic at line rate with short, medium and long frames. In all our baseline tests, the E1200 did not drop a single frame.

Avaya, Foundry and HP boxes moved traffic at roughly 80% of line rate. Avaya and Foundry representatives on-site for testing said switch fabrics that topped out at 8G bit/sec limited their devices, and that's generally consistent with the frame rates these switches achieved.

In the best case, Foundry moved traffic at 86% of line rate when handling 64-byte frames, a result Foundry explained by saying its switch fabric actually has a bit more than 8G bit/sec of capacity.

Maybe so, but in tests with four interfaces Foundry's throughput with 256- and 1,518-byte frames was only about 5.5G and 5G bit/sec, respectively. Curiously, the HP switch achieved throughput close to 8G bit/sec per interface for all frame lengths, even though Foundry manufactures both vendors' switches. One possible explanation is that Foundry and HP supplied different software versions for testing. Given HP's higher throughput (and Foundry's, when tested with just two interfaces) some performance issue with the software image could explain the difference.