Let's also add to this the fact that the TCP ACK's would create all
sorts of collisions, thus reducing the "real" throughput of wireless
(remember, it's a hub) even further for thin-client purposes. But it's
actually worse than that, since wireless isn't CSMA/CD, but rather
CSMA/CA, like the old LocalTalk. CSMA/CA is even slower than CSMA/CD.
So, it's even *worse* for thin-client purposes than already outlined.
And yes, that applies to the new "N" wireless, no matter how new and
"sexy" you think it is.|
Please, *PLEASE* don't screw up a fine system like LTSP by trying to run it on wireless!
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James P. Kinney III wrote:
Wireless has a place when mobility trumps cost. Wireless is not, and will not in the foreseeable future be a viable transport method for thin clients. It may become useful in the chubby client (local apps) as they require less constant bandwidth. A $70 AP is quite limited in power and connectivity. It still requires a copper connection. And each client machine requires a $30 NIC instead of a $10 NIC. A 54Mbps AP provides 37.8Mbps of usable client bandwidth. Jumbo frames are not an option in the wireless specs. Since a current thin client requires a minimum of 7Mbps with no sound or streaming video that puts the maximum client count per AP at 5. With a measured benefit ratio of 3:1 students:clients that puts the max class size at 15. In Georgia the max size is 24. So that puts the thin client using wireless into the 4.8:1 ratio which has been shown to be ineffective. So a WAP ($70) plus 5 clients ($30 *5 = 150) requires $220 and is not expandable and won't provide enough classroom exposure to make a statistically significant academic benefit. Most systems ship with an onboard NIC. An 8 port Gig switch is $70 (A 10/100 is $30). A managed 8 port is $110 - retail. So a wire is already run for the (theoretical) WAP, plug in the switch (save $210 per classroom - $30 * 7 clients) and get the 3.4:1 back. And at only 49Mbps, there is expansion room to support streaming video (limited) over a 100Mbps wire for 7 clients or add more clients using a Gbit feed from the upstream switch. Yes. Wireless is "sexy". It's mobile. But the reports are in from all over corporate and college campuses - it's EXPENSIVE to set up and maintain well. My money is on the wire. On Tue, 2008-10-07 at 08:54 -0400, HOWARD DANIEL-GVN674 wrote:IMHO, wireless has it's place in schools and will definitely get better in many respects over time, as well as cheaper. I agree with Jim that when doing an enterprise server model, where the wireless links to classrooms would be between servers and clients, wireless is a very bad idea, and likely to stay a bad idea until we get speeds in excess of 400 Mbps, since real speed over wireless is usually about half of the stated PHY layer speed, so 54 Mbps is really about half the Mbps in reality. But wireless links to a classroom server are still viable and cheaper if they were only more user friendly in Linux (a point to Jim's $$$ labor cost), since $70 for an access point and $30 for a wireless NIC is still less than half the cost to wire a classroom (usually at least $200), and subsequent rooms nearby would be only $30. But getting wireless to work in Linux is not always easy, which is I think Jim's point, due to things like chipsets changing rapidly and not being supported in Linux, although I suspect it will get easier over time as well. And for rooms with older wiring, or wiring that runs by noisy electronics, that the school won't have the budget to rewire anytime soon, wireless is useful as a backup and alternative. And wireless to classroom K12LTSP servers doesn't require batteries, of course. If we could generate a decent list of supported wireless NICs for classroom Linux servers (and keep it up to date) I think wireless would have a strong place for K12LTSP deployments using the classroom server model. Plus, if I were in a school that had a really hostile IT department that said no way to K12LTSP on their network, one of the ways to set it up w/o them and their network being affected would be a classroom server with a 3G broadband wireless access card. I've seen folks with Linux laptops with 3G access, so I know it's at least possible. Not the best long term solution, agreed, but a way to get a foot in the door perhaps. And if I ever had the time/resources to really evangelize this, a Laptop server with 3G Internet (as backup to a wireline) connected to a switch and thence to a handful of netbooks/UMPCs would be a great roadshow kit to cart around to show schools. The point about laptops is important: what makes wireless really critical is when laptops become cost effective for schools (note when, not if). Already we now have companies breaking the $100 barrier for UMPCs, vis a vis, the HiVision Mini Note: http://techvideoblog.com/ifa/98-linux-laptop-the-hivision-mininote/ At less than $100, it is a viable solution for elementary and perhaps even middle schools, and given the lack of moving parts, should be much more reliable, albeit not as fully reliable as a desktop, but approaching it. Better reliability can be had if it's not a 1:1 program, rather a 3:1 or 2:1 with them if they stay in the classrooms and thus don't get banged around between school and home. My company has wireless deployed throughout all corporate locations so that anytime I attend a meeting, whether I'm in someone's office or small conference room, or board room, I merely boot up my laptop, log on, and I'm connected. Most of my customer locations are likewise, but sometimes they lack an unsecured network for guests, although that too is changing. It is not merely a boardroom thing anymore, and I'm sure this model will spill over into schools when the cost of the laptop (acquisition and support) gets low enough to make them viable, which I'm convinced will happen eventually, and I'm guessing in only a few years now. Best, Daniel _______________________________________________ K12OSN mailing list K12OSN redhat com https://www.redhat.com/mailman/listinfo/k12osn For more info see <http://www.k12os.org>