Wednesday, July 02

Life

That Will Slow The Fish Down

Between my ISP sending my packets on a grand tour of the Solar System and having to be at work early today (early being 8:30, as opposed to my normal time of 11), I forgot to shut off Kazaa, which was busy downloading a set of large files which I will refer to by the code-name "MST3K".

Well, what's the big deal? So I left my file sharing running.

The big deal is this: Between 1 AM and 8 AM, my ISP gives me free downloads (and cuts my speed by 70%, but I'll save that for another rant). From 8 AM onwards, they charge me - once I exceed my princely monthly allowance of 2.5 gigabytes - 14.9 cents per meg. (Also note that sometime in the night they fixed the problem so that my packets were now staying in the general vicinity of Earth.)

I had about 700 MB left for the month. (My month ends on the 10th.) Left to itself, my link can transfer about 500 MB per hour. I left home at 7:45, and would probably be back around 7 PM. So, that's eleven hours times half a gig minus seven hundred meg times 14.9 cents seven hundred dollars in excess usage charges.

Oh. Dear.

The first of the month is by far our busiest time at work; there was no way I was going to get to run home and turn my computer off. The alternative - calling my ISP and telling them that I'd left my file sharing running and could they please disconnect my line - was more palatable than a $700 bill, but only just.

So... Think like a geek.

I SSH'd into my home firewall box. (Thank Linus for Linux, and thank my foresight that I'd set things up so I could do that. I hardly ever need to; mostly I work from home and connect to servers at the office.)

Now what? I'm on Linux. Kazaa is on my Windows box. If I was still runing ME I could have just crashed it remotely, but after the great Driver Plague of '03 I upgraded to XP, which is a little more robust. After a little thought, I set off a ping flood aimed at my Windows box (which is named Ukyo) from my firewall (Pixy). Hopefully that would choke the downloads enough so they wouldn't bankrupt me utterly.

Then I stopped and considered for a minute. I have a router. It's a little blue Netgear thingy that connects my home network to the internet (via my ADSL modem). I viewed it until now as a black - or rather blue - box. Plug it in, turn it on, start sucking data.

But it's a router. And routers route stuff. So if it works like a real router, I should be able to tell it not to let my PC download a squigabyte of data and burn my bank account to the ground.

It has a web interface, but that wouldn't let me do what I wanted. If it was a real router, the good stuff would be accessible by telnet. (Everyone know what telnet is? Good.) But was it? Easy way to find out:

$ telnet router
Trying 192.168.0.1...
Connected to router.
Escape character is '^]'.

Password: *******

pixymisa@>

Woot! I'm in! (Half the stuff I own is named "pixymisa" or something related to it, by the way. If I boot up an old, disused system that I'm planning to give away, there's a 90% chance it has a /pixy or a /misa filesystem. Or both.)

A couple of minutes of poking around revealed the command ip route add which would add an IP route. (Yes, the commands do actually make some sort of sense.) A route tells the router how to move packets from point A to point B. (This is why routes are called routes, and why routers are called routers. Simple, isn't it?)

In this case, point A was the Internet, and point B was my PC, and I didn't want anything getting from A to B. It's not hard to achieve this. Indeed, it happens all the time, mostly by accident.

Imagine that you were having a party, and wanted to invite everyone at the office except for this one person who you can't stand. You can't just not invite her; that would be rude. So what you do, is you give her bogus instructions. Turn left into Floogleman Street, you say. It's the house next to the Fire Station. You can't miss it. Of course, there is no Floogleman Street, no Fire Station, and you live in a condo. You take the phone of the hook, and the party is a huge success.

That's just what I did. I told the router that any packets bound for Ukyo had to go down Floogleman Street (after making damn sure there was no Floogleman Street on my network). The packets would arrive, wander about for a minute with confused expressions on their headers, and quietly expire. Since nothing ever came back, the servers at the far end eventually gave up sending anything, and my bandwidth (and my bank account) was saved.

Try that with a Windows box.

(The title comes from an incident that took place back in the dawn of time when I was at University. Uni, as we knew it. At Uni, there was an ornamental pond in the middle of the library lawn. One day, for no reason that was ever disclosed, the Powers decided that the pond was to be filled in. A group of workpersons duly arrived with a truckload of dirt and dumped it into the pond. One of the workpersons was heard to say the line, and became instantly - if anonymously - famous.)

Posted by: Pixy Misa at 07:02 AM | Comments (1) | Add Comment | Trackbacks (Suck)
Post contains 975 words, total size 5 kb.

1 LOL at the title story (which was the only part I understood).

Posted by: Susie at Wednesday, July 02 2003 08:45 AM (xA/Fr)

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