----- Original Message -----
Sent: Wednesday, July 16, 2003 1:45
AM
Subject: RE: [smartBridges] Bandwidth
Throughput
Tom,
Thanks for the feedback.
Default gateway ok, primary ports ok, all units on same subnet, APt's
both at least 12' above ground, all units mounted on
poles...
To
be honest, I don't think it's a ping thing since the pings I get are very good
between the units (generally 1 to 2mS per hop).
Also, no sign of errors etc in the SB monitor
stats.
The
info I posted was the closest we have got yet to a structured test, though we
have seen similar things in another area where we have units (small urban
town) where the distances tend to be a few hundred metres using roof top
aerials. The effect seems constant across a variety of installations
which is what has me puzzled. Prior to taking up with SB we used DLink
900AP+ units at both ends and had noticed similar effects.
I
find it all quite worrying since I had expected our bottleneck to be our 2Mbps
backhaul pipe and not the 11Mbps 802.11b network!
Since we are in blighty, we tend to mount our aerials a few feet above
roof height and not on towers (would be next to impossible to get permission
and even if we did the money we would need to pay landowners etc would destroy
the business model).
Putting science to one side, it "feels" like there is something
happening when the packets hit the 802.11b interfaces such that throughput
decreases significantly at each hop. I had wondered if it might be
hidden node effects, but switching on RTS/CTS (default is off) has not seemed
to make any difference.
Peter
Loop Scorpio Ltd
providers of Ledbury Broadband and Highnam
Broadband
www.ledburybroadband.co.uk
www.highnambroadband.co.uk
Make sure that the default gateway correctly in both units (closest
router to AP). Primary port on AP should be ethernet, on APcb should be
wireless. Make sure you are using IP numbers to test with (eliminates DNS
and NB delays). Make sure your souer is configured properly. make sure all
units are on the same subnet. Use trace route or VisualPingPlot to identify
where the lag is taking place. Make sure you "open field" has no
interference or large metal objects. Keep your APt's at least 6' above
ground to reduce ground interference. Make sure the units are mounted on a
pole instead of sitting on a table. It's all in the settings, read up on
what each one does and you should be able to get it to work. Good
luck!
{this is my first try on this email-forum, so I
hope it works!}
What sort of throughput do you all get with the
Smartbridges kit? We have been noticing some strange results and have
been trying to pin down what is happening.
Closest we have got to a real test is as
follows:
Internet connection: 2Mbps
::
::=== computer (1) (connected via an Ethernet
switch)
::
AirpointProTotal (set as access
point)
::
600m across basically a level open field (good RSSI
and Link Quality)
::
AirpointProTotal (set as client
bridge)
::
computer (2)
We
first ran a throughput test just over the link using QCheck. This gave
us around 1.2Mbps to 1.4Mbps from computer (1) to computer (2), but
strangely over 4Mbps the other way.
Next test was using toast (www.toast.net/performance) to
measure throughput onto the Internet proper. Computer (1) would get
around 1.2Mbps, but computer (2) could only manage
0.6Mbps.
In
both tests, we would run first one computer then the other etc to ensure
that the same general conditions were applying.
This seeems strange to us for two
reasons:
(1) why should the radio link throughput be so
different in the different directions?
(2) why should the Internet throughput half when a
single Smartbridges link is added (which according to the first test is able
to deliver throughputs of well over 1Mbps).
When we add in double/triple hops, the Internet
throughput drops even further. For example, adding an AirpointPro
Outdoor - Airbridge Indoor link as a second hop reduced the toast test to
only 350Kbps. To me, this suggests that it is 802.11b that is doing
something.
Anyone noticed anything similar, or have any
ideas?
Peter
Loop Scorpio Ltd
providers of Ledbury Broadband and
Highnam
Broadband
www.ledburybroadband.co.uk
www.highnambroadband.co.uk
