Alistair said:
I have 3 XP pro laptops with wireless cards and an access
point connected to a dsl router. For internet access and
email all has worked fine for months from all 3 laptops.
Recently however if I access a share on one of the
machines, I can browse all the shares no problem but if I
try to copy any files it is very hit and miss. If the
files are large it is almost impossible to copy them -
the machine doing the network copy states after a few
seconds of copying data "the network share is no longer
available". The wireless connection stays connected
throughout and internet access remains throughout. All
machines have high signal strength and the machine with
the source files on it does not report any errors during
the file copy process.
I dont understand becasue browsing XP shares is fine, the
problems only occur when i try to copy data.
I dont believe that it is a problem with my wifi config
(open system using WEP key, but an XP issue.
Does anyone have any ideas please?
Your problem sounds exactly like mine. I don't even use WEP and experience
the same symptoms (I rarely have an problems browsing directories on other
machines over my network, but try to transfer anything bigger than about 2
meg and odds are it will either fail with the "device not available" message
or simply lock up. What's most annoying is that Microsoft's single threaded
heritage is clearly showing even on XP, since network transfers that don't
work often wind up locking up the machine and locking out the keyboard/mouse
and even the power off button on machines with soft power buttons). I've
been trolling these groups and a dozen network sites and dialogging with
Linksys for solutions for a year now and still can't fix it. Some things I
can say:
1) One thing they never tell you anywhere I've seen at least is that if you
use a wireless network in infrastructure mode to communicate between two
machines, all the data has to go over the air twice (once to the access
point and once from the access point to the other machine). This will cut
your maximum throughput to less than half what it would be if one of the
machines were connected directly to the router/access point, so if you use
one machine as a file/printer server try to wire it if you can.
2) TCP/IP on PCs at least doesn't seem to recover well from packet loss all
the time. One thing I did do was download NetStat LIve (from AnalogX) to
chart data throughput during those LONG transfers, which will show you what
the normal flow rate is and that at times the throughput drops to zero, then
usually recovers. Sometimes though it never recovers and after 30 seconds
or so the MS file/printer sharing software running on top of TCP/IP
apparently gives up and gives you some silly error message (Actually a
variety of them in my experience but that may just be because one of my
mahcines runs ME).
3) One thing I thought may be a problem was that if you have a reasonably
large TCP/IP receive window (the number of bytes that can be sent over the
connection before the sender gets them acknowledged), it's possible that
because the wireless access point has to hold packets it can't send on to
the receiving machine because the radio is busy receiving from the sending
machine, the access point can run out of space, and maybe that's what's
causing the packet loss and resulting slow recovery (a big window also means
the timeouts for detecting something got lost have to be long and resulting
recovery procedures to build up the transmit rate again will also be
longer). I tried tinkering with this (Dr TCP from dslreports.com) but
shrinking the window seemed to make things worse, not better.
4) Another possibility I haven't figured out how to detect is that of
interference from 2.4Ghz phones or networks in other houses nearby. I
didn't think this likely because my house isn't all that close to any others
and the neighbors don't strike me as being technologically sophistocated. I
don't, though, know how to rule it out, and this would cause intermittent
dropouts.
5) Finally as a cure for weak signals or interference I've considered
putting a booster on my access point, but they aren't cheap and I haven't
found one locally and am reluctant to invest in something that may or may
not solve my problem. My machines all read "good or excellent" link quality
and 11Mbits/second transmit rate from the signal strength indicators on the
configuration tools.
My "solution" will probably be a 100 foot cable to use to bypass the
wireless network when things aren't working, but that's not a very
satisfactory one. What really amazes me about this is if things are this
bad for me, how does anyone ever get this stuff to work? (I'm a Ph.D. who
teaches network protocols and has worked in computers and networking for 30
years and know all kinds of arcane things about protocols, drivers, routers,
and networking, but I still can't get this stuff to work reliably, which
leads me to suspect that this may be as good as it gets. Well, it's just
not good enough when I can't reliably transfer a 200 Meg audio file or make
an over-the-network backup without babysitting it and restarting things a
dozen times. Consider what it would be like driving a car that perfomed
like this, breaking down a dozen times in any 100 mile trip. I think we
would still be riding horses
