March 1, 2007 15:02
During the last ten days we have conducted a hands-on training on community wireless. Theoretical lectures have been combined with practical exercises and a few site survey implementations. The training model has the strengths that the community get to see quick results that come out of the theoretical sessions... the main problem is the amount on information that is provided in this very sort time. It will be good to consider a longer training period where other topics are delivered in combination with the wireless training. Energy solutions and traffic control solutions should be build as part of the training. The area is bast as a full solution requires: energy, business models, wireless technology and lots of plumbing knowledge. We have been trying to integrate all these knowledge areas in the best manner.
Slowly things start to fall into place... all this community wireless -thingy- need to fit into a broader vision. It is not about the technology is about building the technology into community needs. Unfortunately, technology challenges are taking too much space during these weeks...
March 1, 2007 14:46
Dust and ICTs
I guess that there are a few things that are difficult to explain until you experience them. I have worked in Africa for a while now and I must say that I have never seen a place where dust takes so much space. Yesterday, at the top of the tower i could hardly have visual line-of-sight to one of the partners that was just 1 kilometer away.
Isolation is difficult, keeping the windows close is an impossible as temperatures reach 42 C at midday. Most (if not all) of the buildings here are not designed to host appliances that split even more warm air. Yesterday, we empty all the server room and rebuild it from the scratch, it was lots of cleaning... but it is frustrating to see how dust takes space so quickly. I still do not know what is the worse season... I still wonder what will happen when the rainy period comes.
The server room looks in better shape, but replacing all the servers to low power and host them in a close cabinet seem to be the only way to go in the long term. Learning... always learning.
February 24, 2007 15:48
Who is who?
Seriously, Ochuko (in right picture) is just about to climb a 45m tower to investigate the line-of-sight of the area. Wise as he is, he uses a climbing harness with two carabiners attached to single rope to attach to the tower. Additionally, he is equipped with a helmet and climbing gloves.
February 23, 2007 14:28
It is not the first time that i have been asked: why do we want to get people connected to the Internet when there are so other needs to solve first? Big changes do not come by working in one single direction... and connectivity is our way to change a few things. When visiting some of the schools in the area, i could not stop thinking in how little we know about these schools and how much i will love to see those teachers and students linked together. It is a lot to learn about life from the schools of Nigeria... i am afraid that if we do not get connected together we are not going to discover what these children have to say.
February 23, 2007 14:01
Hot, Dust and an insane power grid
We are working in Kafanchan (Nigeria) with Fantsuam Foundation. The server room is going to require some changes to accommodate the new wireless NOC. The dust is really an enemy here and it is difficult to find good solutions to isolate computers without a good cooling system. Unfortunately the power grid is just insane, voltage fluctuates constantly and although we have three phases coming into the premises, the generator is the only reliable source of power. And when the power from the grid comes it stays 80-90 V for hours; bulbs work... PCs do not. In the server room a fuse allows us to choose the phase (of the three available)... as sometimes power is only available in one of them.
Low power computers, voltage regulation and an electricity backup system... getting all these pieces together is part of the challenge here. The price of connectivity is not just the price of the bandwidth... getting rid of the dust, cooling the boxes and ensure a stable power supply are also part of the expensive equation. Nice to be here and nice to be connected.
February 20, 2007 17:36
Community Wireless Networks @Fantsuam
A tower of 150 feet has been erected at Fanstuam Foundation premises. Fanstuam headquarters is one kilometer from the center of Kafanchan, where many of the potential partners are situated. The visibility in a normal is more difficult that i expected as the dust makes very difficult to see the sites that are more than 1.2 Kms away. We needed to climb the tower over 20 meters to have the first look of the town. Fantsuam is at least 10 meters lower than the town center. This is very unfortunate as the simulations using SRTM telemetry did not reveal that different of hight.
We also had the chance to use some new climbing gear. I purchased some "vertical work" specialized Carabiners. The gadgets allows to hook and unhook from the tower while climbing. They really worth the 70 EUR as they are really easy to use when climbing.
We made it to the top and yes, the tower was bouncing up there... pictures will follow once back in Sweden.
February 14, 2007 16:17
Time to climb a few towers
During 2007, it is going to be a lot of tower climbing. The projects that we are involved will setup wireless infrastructure in Uganda and Nigeria. There is a couple of websites that have collected a few pictures of the places, you can check them out in the following links: Uganda, Nigeria
January 30, 2007 15:48
Fighting unsolicited mail - php injected mail
During the past year, I have been suffering spam due to websites that contain PHP code that allows mail injection into mail forms. More about mail injection here. Fighting mail injection is a very complex task if you are hosting thrid-party PHP code as it is totally impossible to review every single PHP page that is uploaded to your webserver. There are few alternatives to this problem, forcing users to use certain CMS or software that you trust (bad, bad, bad), add complex Apache mod_security rules (slow, slow, slow) or not allowing the use of the mail() function at all (out of business). The most friendly solution is to try to track spam origin and hence the - flawed code -.
Tracking spam mail that is injected via PHP forms in a website is also challenging. Mail logs needs to be checked against web access logs. In heavy loaded servers with hundred of transactions per second it is an unfeasible task as it requires to review thousand of lines of logs. An approach is to modify the mail() function of PHP to include an extra header that indicates the webpage that originates de mail. By adding an extra header, it is possible to backtrack the PHP page that originate certain mail.
The steps can be summarize as follows:
- Get the php source:apt-get source php4
- Apply the mail.c patch: patch -p0 < mail.c.patch
- Install dependencies to rebuild php4
- Rebuild the .deb package: dpkg-buildpackage
- Re-Install the php4-common and libapache-mod-php4
After applying the patch the mails should contain a new header of the type
X-PHP-Script: www.the_web_page.org/send.php for 242.45.142.236
July 23, 2006 11:43
Since early May 2006, the Royal Institute of Technology is kindly hosting the Pootle Server and the OpenOffice.org build server. The Pootle Server is running the latest release 0.9.1 in Ubuntu Dapper. The OpenOffice.org build server runs ooo-build (OOC680m7).
Special acknowledgement goes to fli@KTH for his dedicated time in KTH server room. This is the last posting before my summer break. Äntligen!
July 14, 2006 11:30
Flashing the bricks
I have run in all kind of problems trying to get new firmware to run in a series of linksys models: WRT54G, WRT54G (v1.0, V1.1, v2.0). In all cases the trouble was to get the box to accept a new firmware via tftp. I did managed to unbrick the boxes by forcing the linksys to enter safe mode... i managed to put the brick in safe mode by shortcircuit the pin 15 and 16 of the flash chip.
Using atftp run in "push" mode i managed to catch the slot to upload the image. Once uploaded the image a waited a few minutes to ensure that the image was written into the flash and the box has rebooted into the new OS.
atftp --trace --option "timeout 1" --option "mode octet" --put --local-file newimage_to_tftp.bin 192.168.1.1
A few words about the external antennas, the box comes with two antennas (diversity). External antenna should be placed to the connector that is closer to the WAN interface.