[Soekris] Soekris 6501 as a Wireless Access Point / Advice requested
ralph at lr.los-gatos.ca.us
Thu Jan 5 17:41:28 UTC 2012
I have been running a very similar setup for several years now, a net5501 with a Ralink RT2561S card, with the machine being used as a firewall (NAT box), router, DNS/DHCP/NTP server, wireless AP, Squid proxy, file and web server for the home, and a few other functions. I've been running OpenBSD, because it is so well audited and secure. It is also very cleanly organized and easy to administer, partially because things are minimalist. Unfortunately, my hardware has become obsolete (disk capacity and age issues, not enough memory for some services, and an OS upgrade is urgently needed).
There is, however, one huge problem with OpenBSD, which partially exists in the other *BSD versions too. Wireless clients can go into something called "power saving mode", in which the AP has to hold packets for the client back (because the client has turned off its receive circuits), until the next "beacon" packet that wakes the client. Unfortunately, OpenBSD does *not* support clients in power saving mode. And while clients (typically laptops and smartphones) that run Windows or Linux can be configured to not go into power saving mode, this is not possible for Apple devices (both MacOS and iOS). This causes latency and throughput to MacBooks and iPhones to be horrible, as the missing packets have be retransmitted at a higher layer of the TCP/IP stack. OpenBSD has no plans to support power saving mode when running as an AP. This means that at my next install, I will abandon OpenBSD, and switch to another OS. I want to stick with the *BSD family, as Linux has over the decades become a disorganized mess to administer, maybe even worse than Windows.
Fortunately, FreeBSD supports power saving mode, but that support seems to be restricted to only certain device drivers. Another question is support for 802.11n with multi-antenna (MIMO) and beam forming. Not clear to me how well this works coming from a miniPCIe card with a potentially mismatched set of antennas. But I'm also not sure that the bandwidth gains from MIMO and beam forming are sensible in a residential environment; it depends heavily on the usage model, which can vary widely. Which immediately raises the question you bring up: which wireless card to buy. II have not yet found one up-to-date place that shows which FreeBSD wireless drivers have what capabilities, and how that works with external antennas.
All I'm saying here is that you should research these questions before ordering the 802.11 hardware for your home-built AP. I'm no longer even sure that in the age of 802.11n MIMO, building your own AP is still sensible. The tradeoffs between complexity, power consumption, cost, performance, and setup and support labor are not obvious.
Ralph Becker-Szendy 408-395-1435 ralph at lr.los-gatos.ca.us
735 Sunset Ridge Road; Los Gatos, CA 95033
More information about the Soekris-tech