Have you seen the light?

By Robert Currier, ITworld.com |  Networking

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 href="http://www.cisco.com/univercd/cc/td/doc/pcat/ca6000.htm">Cisco 6509s. Our old
core routers ( href="http://www.cisco.com/univercd/cc/td/doc/product/core/cis7505/cicg7500/cicg75po.htm
">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 href="http://www.nortelnetworks.com/promotions/virtualreality/index.html">Nortel
Optera hardware, but similar products are available from href="http://www.nortelnetworks.com/promotions/virtualreality/index.html">Lucent
Technologies and href="http://www.marconi.com/products/communications/">Marconi.

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