Category Archives: Networking

Ain’t It Cool Dept.

A friend just pointed me towards this new pen device (thanks Mike).

Ostensibly for kids, it sounds like a little piece of magic. How actually useful it might be is another question, but read the article and judge for yourself.

For more fun, check out their homepage at where you can try out the technology using a virtual pen controlled by your mouse.

Very cool.

DSL splitters & Presscom’s structured cabling guide

I was looking up some info on Eircom’s wall-mounted DSL splitter boxes. Opening up the box, I found “UK Reg Des No 2097942”. This led me to the UK Patents website office, which turned up this design from Pressac Communications.

Browsing around Pressac’s website, I came across their Structured Cabling System Installation Manual which is a really useful reference. It covers everything from cable trays, testing, fibre splicing, intra-floor wiring, termination methods, and even fire-proofing.

I didn’t find the info I was looking for about the DSL splitters unfortunately, so I kept on looking. A friend is having problems with DSL line which I think are related to his Eircom Phonewatch alarm system. I wanted to understand how to connect the alarm system to his DSL splitter so that the analogue POTS signal loops through the alarm cabling while the DSL signal goes directly to the DSL socket.

After some more research, I’m fairly confident that it’s just a matter of disconnecting two resistors on the PCB and looping the alarm wiring through the IDC punchdown block labelled ‘alarm’. However, my searching did uncover another interesting page: DSL Nation’s Inside ADSL MicroFilters page, which has pictures of the internals of a large number of DSL splitters, along with commentary. Useful reading if you’re wondering why one DSL splitter is better than another.

Google goes wi-fi

I see Google is planning to offer free Wifi access to the residents of Mountain View (home of Google Headquarters) by entering an agreement with the city council to mount wireless access points on street lighting poles. They estimate 300-400 such devices will be enough to allow Internet access from anywhere outside a building. Access from inside a building will likely require a small external antenna.

This is an interesting idea, and it sounds as if Google plan to deploy the technology elsewhere if this initial project goes well. As they say themselves, Google can justify providing free access since it helps generate additional traffic for both Google and its advertising partners.

The city council proposal makes interesting reading, especially if you’re curious about the logistical details of such an arrangement (who pays for the power, what if the city changes its mind in two years, etc.)

One thing I haven’t seen mentioned yet is the impact of this proposed network on exising wireless networks in the area (e.g. within buildings). They all use the same 2.4 GHz unlicensed band. No doubt there are already newsgroups getting ready to meltdown with discussion of this…

eBay Dismay

So it happened yet again: I tried to be too clever with some manual sniping in an eBay auction, and ended up losing … the item in question (a DVD-based Satnav system for my car) sold for a good €60 less than I was willing to pay.

My mistake? I waited until about 50 seconds before the end before placing my winning bid. Unfortunately, eBay had timed out my account, so wanted me to login again. Very unfortunately, eBay’s login server (though not its main server, apparently) was running very slowly. It took 12 seconds to display the login page, another 12 seconds to process my login, another 12 seconds to accept my bid, 12 more seconds to accept my confirmation … just in time to tell me that the auction had ended and my bid was invalid 🙁

Why didn’t I just bid earlier? From experience, there are always a few people waiting in the shadows to place a last minute bid and pip the highest bidder, and I didn’t want to drive the price up unnecessarily. In this case, the last minute bidding went from €210 to €250, and I was willing to go to €312.

So, new strategy to avoid this extremely irritating log-in process: two minutes before the auction ends, place a minimum bid for the item in question. Also line up my maximum bid, ready to press submit. 30 seconds before the auction ends, hit Submit. I’ll still get caught by eBay’s annoying habit of letting users bid against themselves (what’s going on there?), but for an eagerly contested item, it’s worth paying an extra pound or two safety.

Cracking WEP in 10 minutes

Tdoday’s edition of Jon’s Radio pointed me towards an entertaining screencast which shows just how easy it is to attack a wireless network protected using WEP.

The screencast is at

and it’s well worth a look (no audio required). WEP may be better than no security at all, but only if no one can be bothered to take the trouble to defeat it.

Name that tune!

For a while, I’ve thought that someone should set up an Internet site to let you find the name of a piece of music you’ve heard. Apparently I just wasn’t looking hard enough – today, I stumbled across, a kind of Wikipedia for music.

My plan was that the site would allow you to enter the tune on some sort of virtual keyboard, ignoring tempo and paying attention only to the relative up and down frequency differences. It turns out that Denys Parsons proposed a similar but more robust system for encoding tunes in his 1975 book, The Directory of Tunes and Musical Themes. This is now known as the Parsons Code.

Using it is pretty straightforward – just type an asterisk for the first note, then for each following note, type U if it goes up, D for Down, or R if it repeats the previous note. With three possibilities for each letter, a short sequence of just 20 notes can record more tha three billion distinct tunes. It is also not affected by errors in pitch or timing.

Once you have the Parsons Code for your tune (or at least a brief snippet), you just need a big database to search against – which is where Musipedia comes in. They only have about 30,000 tunes so far, but over time I expect this to grow. Certainly, it had no problems identifying Rossini’s William Tell Overture and Puccini’s Gianni Schicchi – Oh, mio babbino caro.

Eircom’s new DSL packages

After several weeks of rumours, Eircom officially announced their new DSL packages today.

It’s not a bad deal. All existing customers will see improvements of between 2x and 4x in total downstream bandwidth, depending on the monthly subscription. The best improvement is for Home+ users, who jump from 512 Kb/s to 2 MB/s. Smart Telecom’s equivalent deal is still significantly cheaper, but offers only 128 Kb/s instead of 256 Kb/s upstream.

There was an opportunity for Eircom to also increase upstream bandwidth, but they appear not to have done so. Several people are speculating that this is to discourage business users from switching to VoIP, thus undermining Eircom’s voice revenue; this could well be the case.

No discussion at all of bandwidth caps – in light of Smart Telecom’s cap-free policy, Eircom may have decided to leave it be for now, privately targetting only those users that are blatantly abusing it.

Interesting times…

Host fingerprinting

The technique of OS fingerprinting has been well documented. It lets you identify the operating system used by a remote host with a fair degree of certainty. Indeed, OpenBSD even supports this in its filter engine; for example, you can write a rule that assigns mail traffic from Windows machines to a lower-priority bandwidth queue than that from other machines (since such traffic is usually the result of a virus).

However, researcher Tadayoshi Kohno has come up with a much more sophisticated approach, based on measuring clock skew across TCP packets. The idea is that every machine has a slightly different skew to their internal clock, and almost all TCP stacks timestamp packets using their internal clock as a reference point. By identifying the clock skew used for a particular PC, e.g. a laptop, you can track that machine’s movement as it moves around the Internet, perhaps connecting from several different countries or via different dial-up nodes.

All very ingenious, and with no end of big brother implications. Read more in this article at ZDNet Australia, or for the full technical details, check out his original research paper.