Shabby chic for network engineers

It’s far from simple, though, to establish whether or not the device you’re dealing with actually implements flow control, and if it does whether it reports faithfully what setting is currently in use or simply agrees with another device’s interpretation of that same setting. Intel offers a suitably terse and non-obfuscated definition, along with some useful screen pictures of how to manipulate the settings in a very typical switch command interface, here.

Shabby chic for network engineers

The cost of doing nothing

I guess that those guys who promote the “leave it all alone” philosophy would say at this point, “what the hell, the whole point of Ethernet is that it allows for dropping packets, that’s what the standard is all about. Can’t understand a particular packet? Chuck it away then!”

It’s worth fiddling, simply put, because whenever you fiddle with a bit of network kit, the results of your work will be with you for a long time

Of course, it’s precisely that sort of behaviour that underlies almost all the performance disasters I encounter in people’s networks, and all too often the cost of a piece of kit at one end or the other of the link is less than the cost of my time to figure out why it isn’t working.

So why bother fiddling? It’s worth bothering, simply put, because whenever you fiddle with a bit of network kit, the results of your work will be with you for a long time. I suspect that most companies leave at least five years between major network refresh activities, and longer than that in many cases. So it isn’t the cost of the kit, or even the cost of my time; it isn’t even the cost of everyone else’s time who had to hang around down the pub while the fiddling was taking place. No, it’s the cost of everyone in the company who uses that network’s wasted time, integrated over the whole lifecycle of the network.

To put some simple numbers to that waste, let’s say that my example here, tuning that ReadyNAS NV+ and its configurable switch, happened in a company with 25 users. The throughput of that NAS server went up from 12MB/sec to more than 30MB/sec. Assume that these 25 users all have work that lives on the NAS box, so halving their waiting time has a powerful effect on their productivity.

Okay, perhaps it doesn’t quite double their work rate. Let’s say that these 25 people each edit 50 documents a day, each of which used to load in six seconds but now loads in three, then that tuning exercise has saved your company 25 people x 50 docs x 3 secs x 5 weekdays x 52 weeks x ten-year lifespan or about 9.75 million seconds. That’s 112 days, or ten days off per year the network remains in use. That’s someone’s holiday, just from a single tickbox setting.

Age against the machine

This sort of improvement is why the savvy network man keeps an old laptop hidden somewhere in a case; a machine that isn’t used for anything but connecting to weird pieces of kit; a machine that conforms to their IP addressing scheme or serial communications default settings without interrupting anything else.

That may seem a small matter, but consider this: how many modern laptops have you encountered that come with some overly smart network location manager? One of those annoying add-ons that presumes to do a better job than XP, Vista or Windows 7’s own network facilities for leaving one LAN and visiting another. All such utilities are designed to help out with the normal working life of an end-user’s laptop, as he/she skips between work and home, via train or airport. Almost all the stuff they’re designed to sweep under the carpet is precisely the stuff that the network person needs exposed.

Take DHCP, for example. Almost every working LAN has a DHCP server, but we network people rarely get called to operate on working LANs. Any add-on that freezes for two to three minutes before timing out, while it searches for a non-existent address server, won’t be found on my wrangler’s laptop. The type of idiot-proofing that’s increasingly plonked on top of a “locked down” desktop domain member PC is just the sort of thing that stands in the way of the low-level bodging required to get in and tweak your LAN switch.

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