Background:
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
both.
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.
Solution:
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 toast.net 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 0.100.5.39 driver 3.2.2.84 software 4.0.1.36
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.
Enjoy!
