Re: DI 624 revC- severe wireless latency after consistent throughput

>Try running:
> netstat -s
> netstat -es
>after a session and see if there are any indications of TCP/UDP layer
>errors.

I'll try that when I get home.

>No. Netstumbler is an active probe AP detector. It sends a probe
>request and listens for the AP to respond. If SSID broadcast is off,
>it will not detect anything.

So much for that idea. :/

>What you need is a passive sniffer such as Kismet and Wellenreiter
>(for Linux). Try downloading a "Live CD" for Linux with Kismet. No
>need to install Linux on your hard disk. I use "Security Auditor"
>based on Knoppix which is literally filled with network tools.
> http://new.remote-exploit.org/index.php/Auditor_main

Cool. I'll try that out as well.

>I previously mumbled something about the search seems to be centered
>around a single client radio. What radio are you using for a client?
>It takes two to tango and with the large number of allegedly defective
>access points, methinks that there may be a problem on the client
>side. Are you doing all these tests with just one client wireless
>adapter?

Hmm. I'm not so sure I understand what you mean by what radio I'm using
for a client. All these tests are going through one WMP54Gv4.0 Linksys
wireless adapter. I did some searches for problems with that card and
couldn't find much.

>That should be no problem if the wall does not have any metal (foil
>backed insulation) inside.

I have no idea what's inside the walls. I can check into that. All I
know is that the wall between the router and the client is drywall.
It's pretty hard to really describe it as a single wall though. Here's
a rough attempt to draw out the layout:
_____________
\\\\\\\\ _________| |
| || o Client
|
| _________||_____________|
_______| | | |
__| \\ Kitchen |
_______ | |_________| |
_______| | |
| o Router | |
|__________|___________________|

The '\\' and '||' are thin doors. The '\\\\\\\' is the front door. So
yeah, maybe it's not really just one wall. If you draw a direct line,
it's 4 walls. The image probably isn't going to turn out. hehe.

>Don't assume that the 5.7GHz phones operate only on 5.7GHz. Many of
>these use 2.4GHz in one direction. That's because it's easier and
>cheaper to build a full duplex system with widely separated
>frequencies. Make and model?

Oops. It's a 5.8GHz phone: Panasonic KX-TG5451S.

>Sounds more like a microwave oven. The duration is the key. 3-10
>minutes around meal times usually means a microwave oven.

Microwave was never on when this happened. We're rarely using the
connection when the microwave is going as it usually means it's dinner
time. :) We've never timed duration. The duration is easily over an
hour and by that point we're already too impatient and we reset the
router. The one time I've seen the problem go away by stepping away
from the router, I'm quite certain the router rebooted itself. As I had
that pesky lil windows message saying that the connection disappeared
and came back. This is consistent with several forum posts I've seen on
the DI624 with 2.70 firmware.

>Replacing the access point is an excellent way to isolating the
>alleged cause of the problem. However, if it's interference induced,
>it could easily be interfering at the client end as well as the access
>point. If resetting the access point, but not the client, "solves"
>the traffic problem, then it's most likely the access point as you
>suspect. However, if rebooting the client does the same thing,
>without resetting the access point, then it's not so definitive.

Rebooting the client has never solved the problem. It was always the
access point with the DI624 router. There were cases with the Netgear
router (WGR614v1) however where resetting the client fixed it
temporarily. But the problem would resurface shortly thereafter until I
reset the router. At that point things would be fine for another 2
months (with Netgear router).

>The next time it slows down to a crawl, try this test. Just walk away
>and do nothing for about 10-15 minutes. If it magically fixes itself,
>it's probably not some firmware anomaly but some form of interference.
>If it's still there after 10-15 minutes, then it's either a very
>persistent form of interference (another wireless network) or you're
>correct about the firmware bugs. This is not a definitive test, but
>it might offer a clue.

Yeah as I mentioned above, with the DI624 (going to keep this focused
on that one router for clarity) the problem would persist for an hour
by which point we got fed up and would reset the router. It could be
persistent interference or firmware bugs. Not really sure. I did read a
post who said he managed to fix things by setting the router vertically
as it was quite warm to the touch. That fixed all the reboots. Perhaps
I'll try that.

>One more question. When it slows down, does it happen gradually or
>suddenly? Gradually is probably some kind of buffer or flow control
>issue in the access point induced by crappy firmware. Suddenly could
>easily be interference.

Well the problem manifests itself rather suddenly. But it takes time
for us to notice the impact. The latency creeps from 1ms-3ms up to 20ms
for about 5mins then shortly thereafter it would skyrocket to
200ms-400ms. Not sure if you'd call that gradual or sudden.

>Also, if you're ambitious enough to try the Linux sniffer route, also
>try capturing some wireless traffic with Ethereal when the latency
>climbs high. Look for multiple retransmissions at the 802.11 layer.
>If that's happening, it's probably interference of some sorts.

>Speaking of interference, I troubleshot one person's tale of woe down
>to a nearby cellular phone site. He was high enough that his house
>was directly in line with the antennas. The cellular system wasn't
>causing the problem, but the co-located WiMax experimental system was
>literally killing the thruput. I doubt this is the case with your
>system, but you might want to look around the neighborhood rooftops
>for new panel antennas.

I'll give that a shot. We are at the same level as several surrounding
rooftops. But they're mostly just convenience stores. I'm pretty sure I
haven't seen anything new on the rooftops.

Thanks for all the suggestions. I'm close to giving up though. We'll
see how things go.

.

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