ActiveSync 4.1, WM2005, MTU-Size

[df2jh]

Hello all,

spending hours of searching i found a MTU-Size issue concerning ActiveSync 4.1 in combination with Tiny Personal Firewall!

The Problem: WM5-device connects to PC; IP-addresses are set up via dhcp correctly (169.254.2.1/2). But ActiveSync freezes, no synchronisation can be done.

Ethereal traces show WM2005-device connecting to pc using a max. MTU-size of 8050 Byte. The PC acknowledges the value but frames exceeding about 5000 bytes will be lost in PC.

The solution: Decrease MTU-Size. In my case a value of 4096 (0x1000) fixed the issue. You may use attached Registry setting (the magic number defines my PC´s RNDIS interface - yours will be different):
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters\Interfaces\{633FC8EC-A187-4DF7-8554-E5BF23AD9B0C}]
"MTU"=dword:00001000

The long packets did not cause any problems without Tiny installed....

good luck - df2jh

[kj]

Interesting find! I am chasing a problem with AS 4.1 that is different than yours (see http://forum.xda-developers.com/viewtopic.php?t=37039). However, I decided to investigate along your findings. I was not able to find the registry key for the device with MTU settings (I found the appropriate folder, though), I assume this would have to be added? There is a nifty and free little utility called TCPOptimizer from speedguide.net that I use to optimize internet activity. It allows you to change settings such as MTU and receive window sizes for all adapters. I tried to set a small MTU for the windows mobile adapter, but it did not work. Please look at my link above. I would appreciate any ideas you may have regarding this problem.

Thanks!

KJ

[df2jh]

oh - thanks for the hint to TCPOptimizer, didn´t know that nice tool yet.

You are right, the MTU dword value has to be added, it won´t be there by default.

In your thread you mentioned: "... even though I made sure that the Remot-NDIS Host network adapter uses "Server assigned IP" addresses (and it shows 169.254.2.1) and pings fine...."

According to my experience Remote-NDIS Host network adapter at PDA must not set to "Server assigned IP". Instead PDA will act as a DHCP-server by itself. To fix the problem delete every entry in PDAs registry key "HKLM\Comm\RNDISFN1\Parms\TcpIp" except "EnableDHCP" and "Subnetmask".

Set them to:
EnableDHCP: 00000000
Subnetmask: 255.255.255.0

You must do it this way because disabling DHCP in network card settings requires entry of a dedicated ip address.

regards

df2jh

[kj]

Good advice. You are correct, the _device_ should be the DHCP server, not the other way around. I tried your registry changes. Something funny first happend: first, the PC would not create a network connection (keeps trying), telling me that device was not giving the PC an IP address. I disconnected the USB cable and connected again, and an network connection was established. (this happens several times every time I connect). Pings both ways fine, but same problem with AS. However, at least the intermittent popups regarding the server IP are now gone (of course, I was able to get rid of that popup when entering IP addresses manually). I ran vxIPConfig for RndisFn1 and have the following information:

IP Address: 0.0.0.0
Subnet Mask 0.0.0.0
Default Gateway:
Primary Wins:
Secondary Wins:
Lease Obtained: DHCP Disabled
Lease Expires: DHCP Disabled

DNS Servers:
Node Type: Hybrid
IP Routing: No
Wins Proxy: No
NetBIOS Scope ID:
NetBIOS Resolution Uses DNS: No

Does this look correct to you?

Another thing I noticed was that I have two USB ports on my PC (laptop). With device connected, I get a network connection called "Local Area Connection xx", where xx is some integer. If I look at its properties, I see that, in the General tab, it says "Connect Using Windows Mobile-based Device #n", where n is also an integer. In my case xx is either 19 or 20, depending on which USB plug on the PC I use and n is either 3 or 5, also depending which USB plug on the PC I use. Hence, there are two LAN connections established, one for each USB plug. Would this also be an issue?

KJ

[df2jh]

Yes, if you plug your device into a different USB-Port iw will create a new "Windows Mobile-based device" and a new local area connection.

I don´t know vxIPConfig but MyIpConfig shows IP address 169.254.2.1 as long as i am connected.

regards

Jochen

[kj]

Do you know if the fact there are two connections set up that it may cause such issues? Also, if you have MyIPConfig, I can install it and see if it registers the same values.

Thanks!

KJ

[df2jh]

No, setup of two ore more connections will not be a problem using ActiveSync. Of cource you must use only a single connection (i.e. USB port) at a time to synchronize a single PDA ;-)

MyIpConfig can be found at http://sourceforge.net/projects/myipconfig

regards

df2jh

[kj]

Thanks for the link. Does MyIPConfig work with WM5?

KJ

[df2jh]

Yes it does!

[kj]

Just tried MyIPConfig. Yes, it registers same IP as you do (169.254.2.1). Hmmmm.... Not sure where to go from here....

KJ

[df2jh]

Did you read already the topic http://forum.xda-developers.com/viewtopic.php?t=37983 ? It exactly describes the effect I suffered from.