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How to approach troubleshooting wireless connections?

 
 
Philip Herlihy
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Posts: n/a
 
      05-24-2009
I look after IT issues, including networking, for a couple of small
offices. I sometimes get a situation where, despite apparently good
signal strength, a machine won't connect.

One machine won't connect (most of the time!) despite my trying three
different makes of PCI wireless cards plus one USB adapter, and two
different access points. Now there's a cable draped across the
office... Connectivity on other machines is poor while others nearby
seem fine.

I've experimented over months with adjustments to various settings,
including setting static IP addresses. One machine burst into life when
I switched from the Intel wireless client to the Windows one, but I
couldn't duplicate this on another machine.

My mobile runs Windows Mobile, and this allows me to run the excellent
"sniffi", which can graph the signals on various channels, and although
Netstumbler can find dozens of different distinct services I've set ours
to the channels least-used locally.

I've recently tried experimenting with TCP parameters like MTU and RWIN,
using DrTCP.exe. However, I'm working in the dark, and I'd like to be
able to monitor the effect of what I'm doing. I've now started using
Wireshark to monitor at the packet level, but I don't know what I'm
looking for. Does anyone have some experience of this sort of thing
they could share?

Phil, London
 
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Jack [MVP-Networking]
Guest
Posts: n/a
 
      05-24-2009
Hi
To get solid Wireless in a business you might need a network of few Access
Points, or a WDS arrangement.
Jack (MS, MVP-Networking)

"Philip Herlihy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I look after IT issues, including networking, for a couple of small
>offices. I sometimes get a situation where, despite apparently good signal
>strength, a machine won't connect.
>
> One machine won't connect (most of the time!) despite my trying three
> different makes of PCI wireless cards plus one USB adapter, and two
> different access points. Now there's a cable draped across the office...
> Connectivity on other machines is poor while others nearby seem fine.
>
> I've experimented over months with adjustments to various settings,
> including setting static IP addresses. One machine burst into life when I
> switched from the Intel wireless client to the Windows one, but I couldn't
> duplicate this on another machine.
>
> My mobile runs Windows Mobile, and this allows me to run the excellent
> "sniffi", which can graph the signals on various channels, and although
> Netstumbler can find dozens of different distinct services I've set ours
> to the channels least-used locally.
>
> I've recently tried experimenting with TCP parameters like MTU and RWIN,
> using DrTCP.exe. However, I'm working in the dark, and I'd like to be
> able to monitor the effect of what I'm doing. I've now started using
> Wireshark to monitor at the packet level, but I don't know what I'm
> looking for. Does anyone have some experience of this sort of thing they
> could share?
>
> Phil, London


 
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Philip Herlihy
Guest
Posts: n/a
 
      05-25-2009
Jack [MVP-Networking] wrote:
> Hi
> To get solid Wireless in a business you might need a network of few
> Access Points, or a WDS arrangement.
> Jack (MS, MVP-Networking)
>
> "Philip Herlihy" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> I look after IT issues, including networking, for a couple of small
>> offices. I sometimes get a situation where, despite apparently good
>> signal strength, a machine won't connect.
>>
>> One machine won't connect (most of the time!) despite my trying three
>> different makes of PCI wireless cards plus one USB adapter, and two
>> different access points. Now there's a cable draped across the
>> office... Connectivity on other machines is poor while others nearby
>> seem fine.
>>
>> I've experimented over months with adjustments to various settings,
>> including setting static IP addresses. One machine burst into life
>> when I switched from the Intel wireless client to the Windows one, but
>> I couldn't duplicate this on another machine.
>>
>> My mobile runs Windows Mobile, and this allows me to run the excellent
>> "sniffi", which can graph the signals on various channels, and
>> although Netstumbler can find dozens of different distinct services
>> I've set ours to the channels least-used locally.
>>
>> I've recently tried experimenting with TCP parameters like MTU and
>> RWIN, using DrTCP.exe. However, I'm working in the dark, and I'd like
>> to be able to monitor the effect of what I'm doing. I've now started
>> using Wireshark to monitor at the packet level, but I don't know what
>> I'm looking for. Does anyone have some experience of this sort of
>> thing they could share?
>>
>> Phil, London

>


Thanks, Jack. We do have two access points, and both are accessible
from all machines, although some can only just "see" the furthest one.
All machines have at least one of them delivering good signal strength,
usually excellent. Still we get these odd connection problems. I've
tried many things over the last few months, and would like to be able to
measure or monitor what's happening - hence the experiments with
Wireshark. Are there any particular situations I should look out for?

Phil
 
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Pavel A.
Guest
Posts: n/a
 
      05-25-2009
Philip Herlihy wrote:
> I look after IT issues, including networking, for a couple of small
> offices. I sometimes get a situation where, despite apparently good
> signal strength, a machine won't connect.
>
> One machine won't connect (most of the time!) despite my trying three
> different makes of PCI wireless cards plus one USB adapter, and two
> different access points. Now there's a cable draped across the
> office... Connectivity on other machines is poor while others nearby
> seem fine.
>
> I've experimented over months with adjustments to various settings,
> including setting static IP addresses. One machine burst into life when
> I switched from the Intel wireless client to the Windows one, but I
> couldn't duplicate this on another machine.
>
> My mobile runs Windows Mobile, and this allows me to run the excellent
> "sniffi", which can graph the signals on various channels, and although
> Netstumbler can find dozens of different distinct services I've set ours
> to the channels least-used locally.
>
> I've recently tried experimenting with TCP parameters like MTU and RWIN,
> using DrTCP.exe. However, I'm working in the dark, and I'd like to be
> able to monitor the effect of what I'm doing. I've now started using
> Wireshark to monitor at the packet level, but I don't know what I'm
> looking for. Does anyone have some experience of this sort of thing
> they could share?
>
> Phil, London



Then, perhaps you are looking for a consultant.
There is lot of free information, tools and guidance in Internet, but
Internet won't give us extra lifetime to learn all that

Regards,
-- pa
( I am not a consultant )
 
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Jack [MVP-Networking]
Guest
Posts: n/a
 
      05-25-2009
Hi
Set the Access Points to two different channels.
Try temp. to put the "Lame" computers within few feet from on of the Access
Point to figure out if it is Wireless problem, or computer setting.
When you use WZC cleanup the preferred list and leave in only the Access
Point that is best for the specific computer.
http://www.ezlan.net/wireless/wzc3.jpg
Note: I can keep going with more pointers like this (aka Trial & Error), but
as Pavel said in his post "live it too short" .
Jack (MS, MVP-Networking)

"Philip Herlihy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Jack [MVP-Networking] wrote:
>> Hi
>> To get solid Wireless in a business you might need a network of few
>> Access Points, or a WDS arrangement.
>> Jack (MS, MVP-Networking)
>>
>> "Philip Herlihy" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> I look after IT issues, including networking, for a couple of small
>>> offices. I sometimes get a situation where, despite apparently good
>>> signal strength, a machine won't connect.
>>>
>>> One machine won't connect (most of the time!) despite my trying three
>>> different makes of PCI wireless cards plus one USB adapter, and two
>>> different access points. Now there's a cable draped across the
>>> office... Connectivity on other machines is poor while others nearby
>>> seem fine.
>>>
>>> I've experimented over months with adjustments to various settings,
>>> including setting static IP addresses. One machine burst into life when
>>> I switched from the Intel wireless client to the Windows one, but I
>>> couldn't duplicate this on another machine.
>>>
>>> My mobile runs Windows Mobile, and this allows me to run the excellent
>>> "sniffi", which can graph the signals on various channels, and although
>>> Netstumbler can find dozens of different distinct services I've set ours
>>> to the channels least-used locally.
>>>
>>> I've recently tried experimenting with TCP parameters like MTU and RWIN,
>>> using DrTCP.exe. However, I'm working in the dark, and I'd like to be
>>> able to monitor the effect of what I'm doing. I've now started using
>>> Wireshark to monitor at the packet level, but I don't know what I'm
>>> looking for. Does anyone have some experience of this sort of thing
>>> they could share?
>>>
>>> Phil, London

>>

>
> Thanks, Jack. We do have two access points, and both are accessible from
> all machines, although some can only just "see" the furthest one. All
> machines have at least one of them delivering good signal strength,
> usually excellent. Still we get these odd connection problems. I've
> tried many things over the last few months, and would like to be able to
> measure or monitor what's happening - hence the experiments with
> Wireshark. Are there any particular situations I should look out for?
>
> Phil


 
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Philip Herlihy
Guest
Posts: n/a
 
      05-25-2009
Jack [MVP-Networking] wrote:
> Hi
> Set the Access Points to two different channels.
> Try temp. to put the "Lame" computers within few feet from on of the
> Access Point to figure out if it is Wireless problem, or computer setting.
> When you use WZC cleanup the preferred list and leave in only the Access
> Point that is best for the specific computer.
> http://www.ezlan.net/wireless/wzc3.jpg
> Note: I can keep going with more pointers like this (aka Trial & Error),
> but as Pavel said in his post "live it too short" .
> Jack (MS, MVP-Networking)
>
> "Philip Herlihy" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Jack [MVP-Networking] wrote:
>>> Hi
>>> To get solid Wireless in a business you might need a network of few
>>> Access Points, or a WDS arrangement.
>>> Jack (MS, MVP-Networking)
>>>
>>> "Philip Herlihy" <(E-Mail Removed)> wrote in message
>>> news:(E-Mail Removed)...
>>>> I look after IT issues, including networking, for a couple of small
>>>> offices. I sometimes get a situation where, despite apparently good
>>>> signal strength, a machine won't connect.
>>>>
>>>> One machine won't connect (most of the time!) despite my trying
>>>> three different makes of PCI wireless cards plus one USB adapter,
>>>> and two different access points. Now there's a cable draped across
>>>> the office... Connectivity on other machines is poor while others
>>>> nearby seem fine.
>>>>
>>>> I've experimented over months with adjustments to various settings,
>>>> including setting static IP addresses. One machine burst into life
>>>> when I switched from the Intel wireless client to the Windows one,
>>>> but I couldn't duplicate this on another machine.
>>>>
>>>> My mobile runs Windows Mobile, and this allows me to run the
>>>> excellent "sniffi", which can graph the signals on various channels,
>>>> and although Netstumbler can find dozens of different distinct
>>>> services I've set ours to the channels least-used locally.
>>>>
>>>> I've recently tried experimenting with TCP parameters like MTU and
>>>> RWIN, using DrTCP.exe. However, I'm working in the dark, and I'd
>>>> like to be able to monitor the effect of what I'm doing. I've now
>>>> started using Wireshark to monitor at the packet level, but I don't
>>>> know what I'm looking for. Does anyone have some experience of this
>>>> sort of thing they could share?
>>>>
>>>> Phil, London
>>>

>>
>> Thanks, Jack. We do have two access points, and both are accessible
>> from all machines, although some can only just "see" the furthest one.
>> All machines have at least one of them delivering good signal
>> strength, usually excellent. Still we get these odd connection
>> problems. I've tried many things over the last few months, and would
>> like to be able to measure or monitor what's happening - hence the
>> experiments with Wireshark. Are there any particular situations I
>> should look out for?
>>
>> Phil

>



Well, I found Pavel's comment surprising, as it boils down to a
suggestion not to bother trying to understand how things work at a deep
level but to surrender responsibility to someone else. Other groups in
which I participate have a different outlook, and the most naive and
untutored questions get patient, tailored answers (more like Jack's)
intended to help the poster up the next rung, wherever on the ladder
that might be.

I am a "consultant", of sorts. Coming from a niche near-real-time
programming background I'm now making a serious (and rather exhausting)
attempt to be able to cover all the basics, from networking to graphic
design, from database programming to hardware repair. Naturally, I
don't know everything, but I've been in the industry for 28 years so
far, so although I've no hope of keeping up with the outer envelope, I'm
doing fairly well at keeping on top of what most customers need.

In a wireless setup I've often seen a situation where the signal
strength appears to be good or excellent, and yet the "Limited or no
connectivity" message suggests DHPC is failing somehow. I've checked
the issues Jack suggests above (thanks Jack) and still sometimes see
problems.

Where I am now is that I'm trying to dig deeper into the details for
real evidence of problems. One correspondent (elsewhere) suggested that
MTU might be an issue, so I've been experimenting with that, but the key
to empiricism is analytic measurement, so I've been playing around with
the Wireshark protocol analyser hoping to see patterns in the packet
stream. I once successfully diagnosed a (wired) connectivity problem by
setting very detailed firewall logging, and picked up the fact that ICMP
3.4 packets were being blocked and so the sending station was unable to
detect that it needed to reduce its packet size - that's the sort of
thing I'm looking for in these odd wireless situations. Rather than try
and judge at a macro level (eg. download times) I'm looking for
something finer-grained, giving more certainty.

Maybe this just isn't a useful approach, or maybe it's one that has been
largely overlooked. But when you have one machine (happy with a cable)
that can't make a wireless connection with any of three access points
using any of four wireless adapters (one at a time) despite very
thorough building, repairing and rebuilding of the windows network
stacks, something's there to be found.

Phil
 
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Jack [MVP-Networking]
Guest
Posts: n/a
 
      05-25-2009
Hi
I have my doubts about the MTU, unless it is totally Off it might affect the
Bandwidth but not the logon.
You can try this free util. it very good in helping adjusting MTU and RCwin.
http://www.speedguide.net/downloads.php
Next step with the computer is to try a spare wireless card.
Jack (MS, MVP-Networking)

"Philip Herlihy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Jack [MVP-Networking] wrote:
>> Hi
>> Set the Access Points to two different channels.
>> Try temp. to put the "Lame" computers within few feet from on of the
>> Access Point to figure out if it is Wireless problem, or computer
>> setting.
>> When you use WZC cleanup the preferred list and leave in only the Access
>> Point that is best for the specific computer.
>> http://www.ezlan.net/wireless/wzc3.jpg
>> Note: I can keep going with more pointers like this (aka Trial & Error),
>> but as Pavel said in his post "live it too short" .
>> Jack (MS, MVP-Networking)
>>
>> "Philip Herlihy" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> Jack [MVP-Networking] wrote:
>>>> Hi
>>>> To get solid Wireless in a business you might need a network of few
>>>> Access Points, or a WDS arrangement.
>>>> Jack (MS, MVP-Networking)
>>>>
>>>> "Philip Herlihy" <(E-Mail Removed)> wrote in message
>>>> news:(E-Mail Removed)...
>>>>> I look after IT issues, including networking, for a couple of small
>>>>> offices. I sometimes get a situation where, despite apparently good
>>>>> signal strength, a machine won't connect.
>>>>>
>>>>> One machine won't connect (most of the time!) despite my trying three
>>>>> different makes of PCI wireless cards plus one USB adapter, and two
>>>>> different access points. Now there's a cable draped across the
>>>>> office... Connectivity on other machines is poor while others nearby
>>>>> seem fine.
>>>>>
>>>>> I've experimented over months with adjustments to various settings,
>>>>> including setting static IP addresses. One machine burst into life
>>>>> when I switched from the Intel wireless client to the Windows one, but
>>>>> I couldn't duplicate this on another machine.
>>>>>
>>>>> My mobile runs Windows Mobile, and this allows me to run the excellent
>>>>> "sniffi", which can graph the signals on various channels, and
>>>>> although Netstumbler can find dozens of different distinct services
>>>>> I've set ours to the channels least-used locally.
>>>>>
>>>>> I've recently tried experimenting with TCP parameters like MTU and
>>>>> RWIN, using DrTCP.exe. However, I'm working in the dark, and I'd like
>>>>> to be able to monitor the effect of what I'm doing. I've now started
>>>>> using Wireshark to monitor at the packet level, but I don't know what
>>>>> I'm looking for. Does anyone have some experience of this sort of
>>>>> thing they could share?
>>>>>
>>>>> Phil, London
>>>>
>>>
>>> Thanks, Jack. We do have two access points, and both are accessible
>>> from all machines, although some can only just "see" the furthest one.
>>> All machines have at least one of them delivering good signal strength,
>>> usually excellent. Still we get these odd connection problems. I've
>>> tried many things over the last few months, and would like to be able to
>>> measure or monitor what's happening - hence the experiments with
>>> Wireshark. Are there any particular situations I should look out for?
>>>
>>> Phil

>>

>
>
> Well, I found Pavel's comment surprising, as it boils down to a suggestion
> not to bother trying to understand how things work at a deep level but to
> surrender responsibility to someone else. Other groups in which I
> participate have a different outlook, and the most naive and untutored
> questions get patient, tailored answers (more like Jack's) intended to
> help the poster up the next rung, wherever on the ladder that might be.
>
> I am a "consultant", of sorts. Coming from a niche near-real-time
> programming background I'm now making a serious (and rather exhausting)
> attempt to be able to cover all the basics, from networking to graphic
> design, from database programming to hardware repair. Naturally, I don't
> know everything, but I've been in the industry for 28 years so far, so
> although I've no hope of keeping up with the outer envelope, I'm doing
> fairly well at keeping on top of what most customers need.
>
> In a wireless setup I've often seen a situation where the signal strength
> appears to be good or excellent, and yet the "Limited or no connectivity"
> message suggests DHPC is failing somehow. I've checked the issues Jack
> suggests above (thanks Jack) and still sometimes see problems.
>
> Where I am now is that I'm trying to dig deeper into the details for real
> evidence of problems. One correspondent (elsewhere) suggested that MTU
> might be an issue, so I've been experimenting with that, but the key to
> empiricism is analytic measurement, so I've been playing around with the
> Wireshark protocol analyser hoping to see patterns in the packet stream.
> I once successfully diagnosed a (wired) connectivity problem by setting
> very detailed firewall logging, and picked up the fact that ICMP 3.4
> packets were being blocked and so the sending station was unable to detect
> that it needed to reduce its packet size - that's the sort of thing I'm
> looking for in these odd wireless situations. Rather than try and judge
> at a macro level (eg. download times) I'm looking for something
> finer-grained, giving more certainty.
>
> Maybe this just isn't a useful approach, or maybe it's one that has been
> largely overlooked. But when you have one machine (happy with a cable)
> that can't make a wireless connection with any of three access points
> using any of four wireless adapters (one at a time) despite very thorough
> building, repairing and rebuilding of the windows network stacks,
> something's there to be found.
>
> Phil


 
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Pavel A.
Guest
Posts: n/a
 
      05-25-2009
@ Philip Herlihy:

Then apologies, you seem to have much more time on your hands than
typical busy issue-oriented IT workers.

But what if the problem is in RF interference?
This can require serious tools that ordinary IT or even electric
engineers don't own, or software that one can't download from internet
freely, and specific skills with these tools and software.

OTOH I enjoyed working with pros (when they tolerate me looking over
their shoulder), have learned something new from them every time.

Best regards,
-- Pavel
 
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Philip Herlihy
Guest
Posts: n/a
 
      05-26-2009
Pavel A. wrote:
> @ Philip Herlihy:
>
> Then apologies, you seem to have much more time on your hands than
> typical busy issue-oriented IT workers.
>
> But what if the problem is in RF interference?
> This can require serious tools that ordinary IT or even electric
> engineers don't own, or software that one can't download from internet
> freely, and specific skills with these tools and software.
>
> OTOH I enjoyed working with pros (when they tolerate me looking over
> their shoulder), have learned something new from them every time.
>
> Best regards,
> -- Pavel


Pavel, your experience of these matters is not sufficient to allow you
to gauge whether I have time on my hands.

PH
 
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Philip Herlihy
Guest
Posts: n/a
 
      05-26-2009
Jack [MVP-Networking] wrote:
> Hi
> I have my doubts about the MTU, unless it is totally Off it might affect
> the Bandwidth but not the logon.
> You can try this free util. it very good in helping adjusting MTU and
> RCwin.
> http://www.speedguide.net/downloads.php
> Next step with the computer is to try a spare wireless card.
> Jack (MS, MVP-Networking)
>


....

>>>>> "Philip Herlihy" <(E-Mail Removed)> wrote in message
>>>>> news:(E-Mail Removed)...
>>>>>> I look after IT issues, including networking, for a couple of
>>>>>> small offices. I sometimes get a situation where, despite
>>>>>> apparently good signal strength, a machine won't connect.
>>>>>>
>>>>>> One machine won't connect (most of the time!) despite my trying
>>>>>> three different makes of PCI wireless cards plus one USB adapter,
>>>>>> and two different access points. Now there's a cable draped
>>>>>> across the office... Connectivity on other machines is poor while
>>>>>> others nearby seem fine.
>>>>>>
>>>>>> I've experimented over months with adjustments to various
>>>>>> settings, including setting static IP addresses. One machine
>>>>>> burst into life when I switched from the Intel wireless client to
>>>>>> the Windows one, but I couldn't duplicate this on another machine.
>>>>>>
>>>>>> My mobile runs Windows Mobile, and this allows me to run the
>>>>>> excellent "sniffi", which can graph the signals on various
>>>>>> channels, and although Netstumbler can find dozens of different
>>>>>> distinct services I've set ours to the channels least-used locally.
>>>>>>
>>>>>> I've recently tried experimenting with TCP parameters like MTU and
>>>>>> RWIN, using DrTCP.exe. However, I'm working in the dark, and I'd
>>>>>> like to be able to monitor the effect of what I'm doing. I've now
>>>>>> started using Wireshark to monitor at the packet level, but I
>>>>>> don't know what I'm looking for. Does anyone have some experience
>>>>>> of this sort of thing they could share?
>>>>>>
>>>>>> Phil, London
>>>>>
>>>>
>>>> Thanks, Jack. We do have two access points, and both are accessible
>>>> from all machines, although some can only just "see" the furthest
>>>> one. All machines have at least one of them delivering good signal
>>>> strength, usually excellent. Still we get these odd connection
>>>> problems. I've tried many things over the last few months, and
>>>> would like to be able to measure or monitor what's happening - hence
>>>> the experiments with Wireshark. Are there any particular situations
>>>> I should look out for?
>>>>
>>>> Phil
>>>

>>

....

Thanks, Jack - I'll certainly try out the utility you've suggested.
Someone else recently pointed out that MTU is unlikely to affect DHCP as
the packets involved are small - obvious once stated!

We have tried (several) other cards, and also access points. Oddly, the
(intermittent) fault seems to stay with the PC, which is perfectly happy
with a cable connection.

I have occasionally seen similar things elsewhere, and was looking for a
diagnostic "toolkit".

Phil
 
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