pete at altadena.net
Tue Mar 13 17:46:13 CDT 2012
On 03/13/2012 03:35 PM, Blake Pfankuch wrote:
> Thanks Pete, that does help. Now hopefully I can get someone who has experience with 500+ devices running on a single one in a fairly small area (High School Gym).
There was a thread about this a couple of months back, I'm pretty sure
it was after last November (but not absolutely sure); lots of discussion
about density and Xirrrus was mentioned. My personal experience with
Xirrus is certainly not high-density, and the "real" hospital certainly
copes with a bunch (though I'm guessing 20-30 users per AP from how many
APs they have distributed among rooms. They seem to do a bunch of their
device telemetry on 802.11 but there are also some more dedicated
frequencies/protocols for medical devices. (even the IV pumps alarm at
the nurse's station...)
I do have some experience with full-duplex RF transceiver design,
though, and the Xirrus configuration can't be easy to make work well.
Not impossible, but difficult.
> -----Original Message-----
> From: Pete Carah [mailto:pete at altadena.net]
> Sent: Tuesday, March 13, 2012 4:32 PM
> To: nanog at nanog.org
> Subject: Re: Xirrus Wireless
> On 03/13/2012 02:34 PM, Blake Pfankuch wrote:
>> I know this is a little outside of the traditional NANOG realm but...
>> I have a customer looking at a fair number of Xirrus Wireless Arrays for 802.11a/b/g/n implementations and am looking for some real world insight into them. On the cover they look cool, the white papers look cool, but I am yet to find technical commentary from a real person on these devices. Looking at the XN line, and just curious if anyone has deployed these, supports these or knows anything about them.
> I can only speak from indirect experience; the rehab place where my wife is staying for a bit uses 4 or 5 of them (older, probably not current, flying-saucer-like boxes suspended from the ceiling at hallway
> junctions) and there, at least, they appear to work pretty well. The particular ones don't appear to my laptop to do 11a. However, I don't think there is any significant user density just from watching the nifty directional light display, so this may not mean much (I'd guess 3 to 10 users over the whole building including smartphones and a couple of pieces of medical equipment that isn't used much). Also there is no IT (or any real technical maint) guy on-premises to talk to so I can't ask about any other aspect.
> The local real hospital uses a Cisco system (or at least Cisco APs; don't know about the AP manager box) which really does appear to work well; I'd guess several hundred APs with lots of full-time medical gear, and a "guest" network which is behind a rather draconian firewall (wouldn't let me ssh out to a non-standard port (65k range), for example; I had to fix myself a 443 ssh port for the time we spent there a couple of months ago... Blocked 25 outgoing; I don't blame them for that, however they also blocked 465 (but allowed 587)).
> I suspect if I wanted 2.4-only I'd go with ubiquiti, but I don't have any experience with them, and their "unifi" boxes don't (yet) come in 5gig. And they don't appear to have independent APs in each box, though I don't know how well the "directional" antennas in the Xirrus actually separate things; even a 100mw transmitter may well overwhelm all the other local receivers unless there is a bunch of shielding inside the enclosure (and maybe even then...) If 802.11 was frequency-split like the cell system it would help such systems a bunch.
> -- Pete
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