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Small victories over my wireless network

Started: 2011-12-17 15:17:18

Submitted: 2011-12-17 17:05:16

Visibility: World-readable

When we moved into our current house, seven years ago this weekend, our only real option for broadband was a cable modem from our local cable monopoly, Comcast. This worked reasonably well, except during peak hours, when our download speeds slowed to a crawl, apparently because Comcast oversold our neighborhood. We could call and complain, and it appeared that our speed would improve temporarily, but this was not a good long-term solution. After a couple of months our local baby Bell, which was then known as Qwest, installed a proper DSL service box in our neighborhood and started offering DSL service. (Our neighborhood was built out in the late 1990s, which was just new enough to have a neighborhood box at which our twisted pairs terminated, rather than a dedicated twisted pair running from my house straight to the central office, but that neighborhood box didn't start out with the capability to serve DSL connections.) We canceled our voice service and got naked DSL service and never looked back.

The one problem with our home network was our use of the cheap ActionTec modem/wireless router. It sort of worked, but its network services were not really up to my specifications, so I set up my DHCP and DNS services on a spare Linux machine in my basement. This worked pretty well until that Linux machine decided to die earlier this year, when my vague future plans to migrate off the spare Linux machine onto a lower-power Linux-based router suddenly gained urgency. I picked up an Asus RT-N16 in the summer and spent the Fourth of July configuring it as my new router. My first mission was to install the newest version of DD-WRT, then figure out how to use PPPoE to log into the DSL account, demoting the ActionTec modem/wireless router to a simple DSL-to-Ethernet bridge. This worked perfectly, and I set up the router and didn't look back. (I continued to amuse myself by setting up buildroot to create my own uclibc toolchain and try to compile and install the newest version of dnsmasq to configure my DHCP server to allow assigning multiple hardware addresses to the same IP address so I could hot-swap between my wired and wireless networks without changing IP addresses, but I haven't quite gotten that working yet.)

We did have one lingering problem after the Great Router Migration: Our network connection would occasionally slow to a crawl from our wireless-connected notebooks on the main level. (I put the base station itself in the basement, where the wiring is easier to maintain, at the center of the wired network.) I suspected wireless interference, especially because the reported connection strength often dropped, but didn't take the time to figure out what was going on.

This afternoon, it got worse, and I finally decided to do something about it. I parsed the output of iwlist with a tiny Perl script and discovered the identities of the networks in the neighborhood:

Cell ESSID Frequency Channel Quality Signal
01 ADRIAN 2.437 6 49/70 -61 dBm
02 MyRouter 2.437 6 33/70 -77 dBm
03 JesusLives 2.422 3 56/70 -54 dBm
04 myqwest0652 2.462 11 40/70 -70 dBm
05 ocean 2.412 1 30/70 -80 dBm
06 GranWireless 2.417 2 25/70 -85 dBm
07 starpenn 2.437 6 28/70 -82 dBm
08 WFESTNET 2.412 1 52/70 -58 dBm
09 oasis 2.412 1 29/70 -81 dBm
10 RidgeviewTel 2.412 1 30/70 -80 dBm
11 sbasnet 2.437 6 26/70 -84 dBm
12 Monge 2.437 6 29/70 -81 dBm

I found a useful Q-and-A on Slashdot and learned that there are only three non-overlapping channels: 1, 6, and 11. My wireless network, WFESTNET, shared its channel 1 with only two other networks, of the twelve visible from my dining room, but two other networks occupied the overlapping channels 2 and 3. Short of knocking on my neighbors' doors and asking them to change the channels of their wireless networks (after war-driving to figure out exactly which neighbors own which network, though I can reasonably surmise that "JesusLives" belongs to the pastor next door), I changed my channel to 11, which is not only sparsely populated but also doesn't overlap with other channels. In my non-exhaustive survey so far, the new channel seems to be working famously.

C will not only let you shoot yourself in the foot, it will hand you a new magazine when you run out of bullets.
- Charles Stross, Where we went wrong