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40/100 GbE Ready

By Paul Mooney On July 9, 2009
Networks
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Only 176 shopping days until Christmas. And, before you know it, you’ll be testing 40 GbE or 100 GbE solutions. These things tend to creep up on you.

You may not be the type to think about Christmas shopping in July. I know I’m not. But when it comes to investing in a test bed, it pays to plan ahead. And the next generation of high-speed Ethernet poses significant challenges for legacy test platforms.

Synchronization and timestamps are two of the challenges posed by high-speed testing.

Synchronization. A test is all about results, but results are meaningless if they aren’t synchronized. At high speeds, synchronization becomes even more important. In a 100 GbE environment that can send one frame every 6.72 nanoseconds, nanosecond resolution is required. And synchronization has to be maintained across all test ports, whether they are in one chassis or spread across multiple chassis. Without synchronization, results from different ports, blades or chassis cannot be correlated to isolate anomalies during troubleshooting, bug detection and isolation.

Timestamps. Another critical capability of network test equipment is the ability to accurately timestamp packets or frames. Timestamps are used to measure latency and jitter. Every frame must have a unique timestamp. At higher speeds, legacy test platforms may not be able to uniquely mark packets because the internal timestamp clock is too slow. If two or more packets fit into one timestamp clock tick, then those packets are marked with the same time, which renders latency and jitter measurements meaningless.

Many legacy test systems don’t have a clock with the speed and resolution to test 40 and 100 GbE.

So, when you’re putting together your shopping list, make sure you get on the right side of the naughty/nice list by select a system that will still be useful when you’re ready to test 40 GbE and 100 GbE. Look for a system with a timestamp clock with the granularity to support the speeds you’ll be testing soon. Also, it won’t hurt to make sure that it automatically syncs and adjusts to provide latency measurements with nanosecond accuracy between ports, modules and chassis, regardless of operating temperature change and cable lengths.

 

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