[Beowulf] Wireless clusters (Bridging 802.11a)
alvin at iplink.net
Wed Jan 14 23:07:37 EST 2004
Jim Lux wrote:
> I'm building a cluster using wireless interconnects, and it is getting
> to be a royal pain to figure out what sort of adapters/interfaces to
> use. I'm casting some bread upon the waters here to see if anyone has
> fooled with this sort of thing.
> I want to go 802.11a because of spectrum usage, not because of data
> rate. If I go to 5GHz, I don't have to worry about accidentally
> connecting to JPL's 802.11b (2.4GHz) network infrstructure, for
> instance, which will keep netops off my back.
> The processors in the cluster are Mini-ITX widgets with Compact Flash
> (CF) drives, and, while booting off the net might be nice, I'm going to
> boot off CF for now.
> Here are some issues that have come up:
> 1) there's two ways to get the node to talk to the net:
> via the ethernet connector and an external bridge
> via a PCI card with a 802.11a adapter (most likely a 802.11a/b/g, since
> that's what's available) (D=Link, Netgear, and Linksys all have them)
take a look at the Actiontec cards. They have a line of prism based cards that are supported by linux and when I was
talking with them they made sounds like they were going to stay with the prism chipset for a while.
> In all cases, I'd have an "access point" of some sort to talk to my head
> node/NFS, etc.
> Ideally, I'd like to set up the network in "ad-hoc" mode, where any node
> can talk to any other directly, without having to be routed through an
> access point. In "infrastructure" mode, many clients can talk to the
> access point, but clients cannot talk to clients, except by going
> through the access point, creating a single failure point (probably not
> important for my initial work, but philosophically "bad").
> 2) It's unclear whether there are Linux drivers for any of the PCI
> based 802.11a cards. The mfrs don't seem to want to fool with that
> market, and, chipset mfrs are quite reticent about releasing the
> intellectual property needed to do a good job writing the drivers.
> 3) I could go with external bridging adapters (perhaps with integrated
> routers, in case I add another ethernet device to the node, or, to hook
> up a sniffer). Here the problem is that not all mfrs appear to support
> bridging, at least with more than 2 (i.e. they can set up a point to
> point bridge, but not a many to many bridge)
> From some reading of the various manuals, it appears that some "access
> points" can be set up to appear to be a "client" in infrastructure mode,
> however that's a problem philosophically (and in terms of latency).
> So, does anyone know which "access points" (i.e. a 802.11x to ethernet
> box) can look like a client in an ad-hoc network.
> (possible candidates: Netgear FWAG114, D-link DWL-774, DWL-7000AP,
> Linksys WAP54A*, WAP51AB, WRT51AB. *Linksys says that the WAP54A
> doesn't do bridging)
> Part 2 of the quest.................
> I'm also looking for suggestions on performance and timing tests to run
> on this cluster once it's assembled. Aside from the usual network
> throughput (benchmark program recommendations requested), I'm interested
> in techniques to look at latency, latency distribution, and dropped
> packets/retries, since I suspect that wireless networks will have very
> "unusual" statistics compared to the usual cluster interconnects.
I think you will want to play with the payload size. It seems to make a big difference for what we are doing(net boot
> And, bearing in mind our recent lengthy thread on timing and clocks, you
> can be sure that I will do those sorts of tests too.
> James Lux, P.E.
> Spacecraft Telecommunications Section
> Jet Propulsion Laboratory, Mail Stop 161-213
> 4800 Oak Grove Drive
> Pasadena CA 91109
> tel: (818)354-2075
> fax: (818)393-6875
> Beowulf mailing list, Beowulf at beowulf.org
> To change your subscription (digest mode or unsubscribe) visit
Alvin Starr || voice: (416)585-9971
Interlink Connectivity || fax: (416)585-9974
alvin at iplink.net ||
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