AMONG THE most popular attractions of this year's CAFECONF Linux conference down in Argentina, the "Buenos Aires Libre" group, is promoting its hobbyist, city-wide "community network".

While other groups here were handing out leaflets or showing software on a PC screen - or in the case of La Intella, a dual-core notebook - the folks from Buenos Aires Libre caught everyone's attention because they had hacked open hardware on display, including open boxes, cables, and a Linksys WRT54G housed in a waterproof case with a large omni antenna. I used the opportunity to have a chat with Martin Seeber who was there promoting the effort and who runs one of the main nodes. I also had a little chat with some of his peers and needless to say I learned a lot.

Network map showing nodes. Plotted over Google's satellite images

Unlike other Wi-Fi "projects" and "communities" like the (in)famous FON which mixes business objectives with grassroots participation, this one isn't about providing hotspots for public internet use, and it isn't commercial at all. B.A. Libre - BAL hereinafter - aims to run a network with its own backbone, capable of routing traffic between nodes even if the Internet goes down, it doesn't rely on the public internet for transportation. The project was kick-started by a handful users a long six years ago and after several iterations and change of structure and leadership, now seems to show steady progress.

The BAL network spine uses point-to-point links and directional antennas along with inexpensive consumer Wi-Fi APs or in some instances full PCs in waterproof enclosures- loaded with their own customized Linux software, dubbed Obelisco - Spanish for 'obelisk' the city's landmark.

Three years ago, at the time the local local loop monopoly covering the northern half of this country decided to charge for DSL traffic above a certain quota - a decision it later dropped -
the company suddenly found itself uncomfortably in the public spotlight, and facing the heat of the angry users and ISPs who demanded local loop unbundling. One exec at the behemoth telco lost his composure and reportedly exclaimed at a congress hearing on the subject: "If you want traffic to be free on the network, then build your own". Well, ironically, that's precisely what these folks have been doing: building their own backbone.

Buenos Aires Libre at CAFECONF 2007

Interesting facts
For their backbone, they choose to use an "extended star" or tree topology, avoiding the use of Mesh technology because of performance problems, as the number of hops increases. This BAL network backbone currently uses 802.11b/g equipment on the 2.4GHz band. It also doesn't use WEP, WPA, or any other encryption, just MAC address filtering, so if you want to connect to a given node you must first register on the BAL system as a project member, and then ask the target node for permission so he can add your equipments' MAC address to the nodes' white list. Users concerned about the safety of their data are encouraged to run OpenVPN to create tunnels in such instance. Some nodes, not all, also sport an omni-directional secondary antenna so that nearby clients all around can connect as well.

I asked them if they had any run-ins with the airwaves watchdog and their response was an emphatic no. There's a regulation making selling VOIP or telephony services using Wi-Fi equipment strictly and specifically forbidden by the airwaves watchdog, but it's aimed at ISPs. First BAL is a non-profit endeavour, a community network, and it doesn't aim to provide any specific services, just inter-connect computers. Thus the local regulating authority gives them no hassle at all because such non-profit usage falls within the 'private use' considerations of the local regulations.

One of the grilled antennas that comprise the network

On the software/organisation aspect, they have done a quite impressive job. The Wiki shows a lot of work, and there's even an on-line map built using Google Maps satellite images and showcasing all nodes and clients, and which are currently active. The registration/membership system is also well done. Dubbed the "BA Libre Location System" or BALLS for short, the project's web map lists 259 "points of interest", that is, either nodes or users who have decided to take part in this project in the whole capital city and its metro area of influence, with 13 on-line nodes and APs in BA city at the time of this writing. There is also a Wiki, an IRC channel and mailing lists.

Annoying landlord? Hack a satellite dish!
When I saw the pictures and the kind of relatively huge equipment some had installed - think a mid tower to mini-tower waterproof metal box hooked to a building's TV antenna tower- or huge directional parabolic grid antennas, one question kept circling my mind: "What if the landlord of building's superintendent doesn't allow me to install such a large antenna?". I asked the guy next to me in the BAL booth. He thought for a second and replied with a smile: "Well, as far as testing goes... you can always mod a satellite dish, and replace the LNB with a biquad. very few people, if any, will notice".

Project's Wiki page showing one of the nodes testing a modded DSS antenna.

He told me one of the nodes even installed one. And yes indeed, there's even a picture of such a mod on their Wiki, and although I wouldn't call it unnoticeable, it proves that nothing can stop this pack of motivated geeks from reaching their common goal. µ

L'INQs
BuenosAiresLibre.org
10 Euro dish with biquad feeder
DirecPC Wi-Fi Dish w/BiQuad Feed