Jonathan's blog

Today, the BBC published a story about the future of broadband, and specifically, 1 gigabit internet.

This isn’t actually so futuristic. It’s not a home connection, but my PC at work has a 1 Gbit internet connection, via the JANET network. It’s had it for a couple of years. When it actually comes down to real-life usage, it isn’t much faster than 100 Mbit or even 10 Mbit. While the data transfer itself does indeed go a lot faster, a lot of time is spent setting up each connection.

Connecting to a server in America from my desk here in the UK takes about 170ms for the signal to get there and back. It will take a few back-and-forths before your file transfer begins. The BBC published a table with some typical values in it.

If, after reading that, you are expecting to use your 1 Gbit connection to download War and Peace in just 2 milliseconds, you can think again. There are several steps your computer has to do to initiate the connection. Each one is subject to the latency, and will probably take a few hundred milliseconds. That’s hundreds of times longer than it actually takes to transfer the data. Obviously the larger the file, the less significant this is. Wasting one second out of nearly 7 minutes for the Super HD video isn’t so bad.

For those who think that latency will improve with speed, think again. There may be some technological advances that shave off the odd millisecond here and there, but unfortunately there’s a pesky thing called the speed of light. The speed of electricity or light in a cable maxes out at 186,000 miles per second, and will usually be about two-thirds of that value, depending on the cable. It will take light 134 milliseconds to go round the equator once. Give or take, that’s how far it is from the UK to Australia and back, and in that time, according to the BBC, you could have downloaded War and Peace 67 times.

As of today, while my computer can send and receive data from the internet at 1 gigabit, unfortunately its hard disk is much slower. Downloading large files tops out at around 350 megabits because the hard disk just can’t handle it. Of course, better and faster hard disks will be invented in the future so this is a non-issue in the long term.

All I’m saying is – don’t believe everything you read in the news, and be aware that for most applications, 1 Gbit is not ten times faster than 100 Mbit.

That is all

While in Sicily last year, I found out where the Internet actually is. It’s halfway up a mountain in Taormina.

The Internet

My home server seems to have developed a problem where its internal-facing network card “jams up”. It still keeps its IP address and everything looks normal, but in actual fact no traffic passes through it, cutting all my LAN hosts off from the Internet.

Restarting iptables, network services or anything else doesn’t help. The only cure I’ve found is to reboot the whole box.

This is OK if I’m using the computer at the time, but a pain if it breaks overnight or while I’m out, as things like my folding@home client, Vista Media Centre TV listings and overnight BitTorrent downloads need Internet access.

So I wrote this bash script to periodically check if it’s broken, and reboot if it is. The only gotcha is that it tests if the interface is working by pinging another LAN host. This is by no means a concrete test!

#!/bin/bash
HOST=192.168.0.10
if ! ping -c 1 -w 5 "$HOST" &>/dev/null ; then
logger ZEUS REBOOT
/sbin/init 6
fi

I ran a speed test from Namesco on my PC at work. It has a gigabit Ethernet connection but more importantly, it is served by JANET – the high speed academic network.

As you see in the screenshot, it achieved 215 Mb/s download!

The best Internet connection in the world? I think so.