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High-speed Ethernet: Who's bothering with that?

A little math will tell you that 10 gigabit Ethernet is more than most businesses need.



Greg Ferro, Dr. Network Forum

Now, call me a persnickety ornery kind of guy, but who is really going to go for 10 gigabit Ethernet? How much bandwidth is enough? It seems I am always reading articles about how there are "new developments" in Ethernet standards for higher speed applications.

That's nice. I'm sure someone is having some fun. But in my universe, 1 gigabit Ethernet is king. When I give the flesh computer a workout, I can't think of a single normal business network where 1 gigabit is not enough. Let me see if I can give you some ideas why.

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If I have a building with about 400 workstations, all the fileservers are in the core with a gigabit connection connecting this building back to the network data center. Using simple calculations, that means that each workstation has 25 kilobits per second. Okay, that's not so much. But that would assume that every single one of those computers is trying to access the fileserver. The average company office would have around 5% to 10% of staff getting a coffee, having a cigarette, staring out the window or making a toilet stop at any point in time. Plus, of course, a good bureaucracy needs meetings to make sure that everyone else knows how much work you are doing, so let's say 10% to 20% are wasting someone else's time.

OK, let's check that again -- 400 workstations, minus about 15% that don't have people in front of them. So that's a total of 340 workstations in use.

Let's also assume that 50% of those folks are using an office productivity application (word processor or spreadsheet) or checking their e-mail. They spend most of their time thinking or waiting for keystrokes. Let's say that these workstations would use a quarter share of the bandwidth. So now we have 170 times 0.25, for 212 workstations in total sharing the bandwidth.

In reality, it is highly unlikely that all of these people are going to require server resources simultaneously. Being generous, assume that 20% are going to be actively transferring (I regard this as highly unlikely) at any given interval. So 20% of 212 equals 43 workstations.

All in all, that means that each workstation has 23 megabits of bandwidth in the backbone connection. That's pretty reasonable, isn't it?

Now, think about fileservers. Most fileservers available today have a maximum transfer rate across the network adapter of around 300 (maybe 400) Mbps. Seriously. (Runs some tests some time and check what you get). This assumes your server is set up well and your operating system is well tuned.

If you actually have users using 20 Mbps, you are going to need a lot of fileservers to handle that load.

So we can see that 1gigabit is a whole lotta bandwidth. And yet our good friends who provide our switches would have us believe that every 48 ports needs a gigabit connection to the core. Bah, humbug!

But wait, there is more -- remember that the better networking vendors make equipment that allows you to bond multiple gigabit connections into a single pipe for redundancy. So why the hype about 10 gigabit?

First, marketing people do not actually understand what they are selling. Customers need to take the time to understand what they really, really need and tell the vendors to stop trying to sell them the latest thing. We often don't need it.

Second, it is just possible that certain types of carriers might use 10 gigabit in the wide area network. As a technology for Internet Protocol backbones, Ethernet (and lots of it) might be a good thing for short-run point-to-point connections. But in light of the latest telecommunications fiascos (a la Worldcom), the fact that 10 gigabit can run 70 kilometers is being ignored. And with the Ethernet telcos such as Yipes rumoured to be very dodgy, don't expect to the see the second tier groups pick it up either.

I am very confident that Cisco, Nortel, Foundry, Juniper and friends will be right there, selling 10-gigabit equipment. There seems to be no shortage of people to buy it, even if they don't know why.

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