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10 posts

Wannabe Geek

Topic # 401 9-Aug-2003 11:18
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I have a Belkin 54g router, a Cisco 350 (128bit) card and an Enterasys
(64bit) card all with the latest firmware; both run just fine at full
speed/good signal. These are being used in a couple of laptops daily, and also
work with my 5450 in a dual-pc sleeve. I have run WEP PSK-128 just fine
on the 5450 with the Cisco card, but normally use WEP PSK-64 to cater for

However, the 5450 runs like a dog, and is almost unusable! Signal
strength is around 45% right next to the AP antenna! It is extremely
slow, I suspect it is running out of buffers or doing lots of retransmits.
If I turn WEP off, it is better, but I do not want to operate in this mode for
security reasons.


The problem with the 5450 was related to the MTU size on the WLAN not
being defined in CE. I have searched other forums, and there are LOTS of
people having this kind of problem, with varying symptoms such as:

* WLAN slow/not working/dropping out

* WEP apparently not working

* DHCP problems

* browsing problems

* ActiveSync problems (over WLAN)

* iPAQ very slow, poor response to user input when WLAN on

What all of these have in common is that IP is being used, and the heavy
fragmentation/ retransmission on the WLAN loses packets, causes protocol
time-outs, overloads the processor and so kills overall performance.
According to MSDN, the CE driver is supposed to supply a suitable default
MTU size, but this one obviously does not get it right. My fix is to
explicitly put one there:

Regedit: HKLM/Comm/vnetusba1/Parms/Tcpip

New Key(dword): MTU

Value: 160 (decimal)

This seems to completely fix the problem for me; my 5450 now runs and
behaves like I expected from the start. Browsing actually works now.

A sample performance check from shows 170Kb/s download over the
WLAN, which is about what I would expect for the device. If I turn on
power management for the wireless card, throughput drops by around 20%
(but the battery probably lasts longer).

For reference, I have all the latest ROM & firmware, my versions are:

CE 3.0 ROM 1.11.19 ENG 05/24/03

WLAN firmware driver software

This is the FIRST TIME it has ever worked properly for me since I had the
5450! I am sure this is not an isolated problem, give it a try and you
will probably notice an improvement.

The MTU size of 160 seems to be optimal in my case. Some tweaking may
produce a slight improvement, but 128 works and going up to 224 kills it,
so I am happy with that for the moment. There are other IP-related
parameters which may help general performance, but MTU is the one that
stops it.


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10 posts

Wannabe Geek

Reply # 1032 12-Aug-2003 11:58
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Just for clarification, the fix I posted is intended as a work-around only, to specifically address a problem with the HP WLAN driver in the 5450 under CE 2002.

The MTU work-around makes the 5450 usable, but I do not regard this as an optimal solution -- HP needs to fix it properly.

I understand that the problem does not exist in the WM2003 driver , so maybe that is going to be the ultimate solution. Don't hold your breath :-(

1 post

Wannabe Geek

Reply # 2978 22-Jan-2004 05:31
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This fix worked for me - I have Ipaq 5550 and Belkin Adsl Gateway Router. I have not yet experimented with other MTUs and since the performance with this setting at MTU=160 is very good I do not see much value in trying. Adding this value has turned browsing from a joke into a reality.



1 post

Wannabe Geek

Reply # 6862 26-Jun-2004 07:17
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I have these same problems but I am not familiar with editing the regestry. I would be very grateful if you can go through the procedure step by step.

Many thanks

Dave UK

1 post

Wannabe Geek

Reply # 11368 29-Dec-2004 11:02
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Try this :)
Download on site
registry editor ...
And go open regedit :
HKEY_LOCAL_MACHINE -> Comm -> vnetusba1 -> Parms -> Tcpip
Now in the left corner use Edit -> New Value -> DWORD and
Value Name: MTU
Value: 160

Thats all.

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