Have you seen the light?

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I've spent the past few months overseeing the upgrade of our campus network. We migrated from a mixture of 100 Mbps FDDI and Fast Ethernet to a fully meshed Gigabit Ethernet network using Cisco 6509s. Our old core routers (Cisco 7513s) ran at an average CPU utilization of 80 percent. The new hardware loafs along at a comfortable 10 percent.

Nevertheless, I tend to operate in a mode of minor paranoia. The new core routers might be running at 10 percent now, but where will they be in three months? In six months? What happens when the next Napster comes along? Will Gigabit Ethernet be enough? What's going to be the next backbone technology du jour? Will it be 10-gigabit Ethernet?

Today I'm leaning toward optical networking for the next backbone. Optics have numerous advantages over electronics when you start pumping packets at multigigabit rates. Perhaps the most important is the ability to keep the traffic light (and I don't mean throughput, I mean photons) from end to end. Traditional routers convert each packet from light to electrons and back to light on each hop along the path. The conversion chews up a significant amount of time and puts a limit on the maximum bandwidth available.

I've started working with an optical technology called dense wave division multiplexing. DWDM transmits multiple wavelengths of light -- called lambdas -- on each fiber at speeds approaching OC-192, or 9.953 Gbps. Systems presently under development can combine more than 64 lambdas on a single fiber, giving network managers the ability to stretch the fiber plant well beyond its present capacity.

Today the hardware is expensive, but so is digging new trenches and laying new fiber. I figure we can save a significant amount of money by maximizing the bandwidth each fiber can carry.

Deploying the DWDM gear hasn't been a walk in the park. This is complicated hardware, folks, and it requires quite a bit of tuning to get everything working just right. We ran into problems with distance limitations, code incompatibility between modules, and excessive bit-error rates before we got the situation under control.

Our current configuration uses Nortel Optera hardware, but similar products are available from Lucent Technologies and Marconi.

Before you start thinking about using DWDM in your network, make sure that you have a good understanding of the technology. A good way to start learning about DWDM is by reading the DWDM/fiber optic technology tutorial by Jason Hsu.

If you've been suffering sleepless nights worrying about backbone capacity, take a look at optical networking. You might find something to brighten your day.

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