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The bottom line: Either you need more bandwidth or you don't. If you can saturate a gigabit link, you have a problem. There are ways to balance network traffic across multiple gigabit trunks, and sometimes a redesign will mitigate your need by localizing traffic. So you may be able to get by while you wait for the inevitable price drop. On the other hand, you may be in a situation where the fiber to support multiple trunks is more expensive than even the high price of 802.3ae, which can range from $25,000 to $59,000 for Extreme and Foundry. It's also a truism of network design that simpler is better, and 802.3ae does indeed provide a simple, scalable solution for companies that have exhausted their gigabit connections.

QoS Test click to enlarge

We used an Ixia 1600T chassis-based device to generate various types of Layer 2 and Layer 3 traffic. Ixia's testing equipment is capable of blasting precise patterns of traffic at levels limited only by the theoretical bandwidth of the interface. The 1600T came equipped with two 10 Gigabit Ethernet LAN modules as well as gigabit interfaces. Ixia's IxExplorer GUI and ScriptMate applications made it easy for us to hammer the Extreme and Foundry boxes with a barrage of full-duplex tests. The 10-gigabit modules supported the 1310nm LAN interface, which we requested the vendors provide because it's the most common type of physical interface used with 802.3ae (see "10 Gig Can't Wait to Interoperate" for an explanation of the different interfaces). We set up our tests to have zero tolerance for packet drops: If even one packet were lost, the test would fail.

We began with standard throughput tests at various packet sizes. The smaller the packet, the harder the device under test had to work because it needed to inspect each header for an Ethernet address in the case of Layer 2 and for an IP address in the case of Layer 3. Then the device had to look up the addresses in their respective tables. Because there's a header on every packet, and more packets can be sent in the same amount of time if they're small, this method resulted in a corresponding increase in headers requiring inspection. Both boxes handled these tests at both layers without a hiccup. As expected, they performed at roughly 8 Gbps because of the bottleneck between each card and the backplane.