Packet degregation b/w two seperate wireless net's

[JHaislet]

I have two seperate wireless access points with two seperate freqencies of operation (one on 5.7ghz & one on 2.4ghz). I have this setup so each AP will only be sending data streams in one direction (instead of having both the IBM T43 & Media Center on the 2.4ghz specturm, and the AP having to effectively transmit the data twice).

Sending & receiving data across either wireless link to a centrally located file server results in 2.5MB's per second transfers. However, when I try to send/recieve data between the T43 & Media Center, the fastest transfers I can get are about 1.6MB's per second.

I've tried adjusting the Beacon Interval on all the wireless equipment, making sure they're all set the same (tried 50, 75, 100, 125). The Fragment Length & RTS Threshold (length) are both set to 2346 on ALL wireless equipment. DTIM Interval is 1 on all equipment as well.

It seems as if the packets are not being repeated correctly by both sides when they reach the final Access Point (regardless of which direction they're going). So I'm guessing both AP's are having to break up each packet because it is too big and then transfer it in pieces, which might explain the drop in transfer rates.

Most importantly, if that is indeed what is happening, how would I go about fixing this? Would tweaking the Fragmentation Length or RTS Threshold help any?

[sugo]

The diagram is pretty well drawn. Which software did you use?

By 1.6MBps, does it go up and down or stay flat?

I wonder if the degradation is caused by RF interference? My 27MHz wireless mouse can make a 2.4GHz bluetooth connection very unstable at times.

[JHaislet]

Microsoft Visio 2003 for the diagram, works pretty well

It stays a solid 1.6MBps. All transfers, regardless of where they're going stay very solid with respect to speed.

One of the reasons I split the two wireless segments up was to significantly reduce RF interference and I've always had blue tooth disabled.

[AIX]

I think it is a delay/transfer problem (higher delay, lower transfer); try set on T43 and Media Center:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultReceiveWindow"=dword:00018000
"DefaultSendWindow"=dword:00018000

[JHaislet]

My current registry settings under Parameters is blank. Nothing is there except the (Default) string and it has no value set. Is that normal?

Also, what does the 18000 mean/signify/do? I'm assuming that's in decimal form?

Thanks for the help! I can't wait to try this out.

[AIX]

-----------------
From http://www.microsoft.com/ntserver/docs/TCPIP.DOC :

DefaultReceiveWindow

Value Type: REG_DWORD

Default: 8192

Description: The number of receive bytes AFD will buffer on a connection before imposing flow control. For some applications, a larger value here will give slightly better performance at the expense of increased resource utilization. Note that applications can modify this value on a per-socket basis with the SO_RCVBUF socket option.

DefaultSendWindow

Value Type: REG_DWORD

Default: 8192

Description: Similar to DefaultReceiveWindow, but for the send side of connections.
------------

18000 - _hexadecimal_ value

Copy and paste the following and make it a .reg file and merge it into your registry:


Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultReceiveWindow"=dword:00018000
"DefaultSendWindow"=dword:00018000


To undo this tweak, simply delete the Parameters key (or DefaultReceiveWindow and DefaultSendWindow keys).


Hope this will help.

[JHaislet]

Hey that's great, thanks for the info. I'll read thru that today & give it a try.

[JHaislet]

Flipping thru the document, it seems like those commands are only applicable to NT Server 3.5 thru 4.0. I didn't see anything about Windows 2000 or XP. Regardless, I tried the registry settings on both machines and the rates stayed the same, and maybe even slowed down a fraction.

I was really hoping this would help too!

Thanks for digging that stuff up, Windows XP must handle this stuff automatically now & using other parameters.

[AIX]

I'm sorry to hear that. I tried these settings a couple of months ago on a few W2k workstations and the transfer rate jumped with + 2-4 Mbps in my case.