Upload problem with gigabit/jumbo frames...

n0xlf · 03-18-2005, 08:49 PM

* FlashFXP v[3.1].[12 ], build [1075 ], [X]registered
* OS [X] WinXP, [ ] Win2K, [ ] Win98, [ ] WinME, [ ] Other
* Running behind NAT/router [X] No
* Running firewall [X] No
* Running Antivirus [X] No
* Network [X] LAN

Took me a while to figure this one out, but here are some strange issues when using FlashFXP with gigabit ethernet on a LAN:

-Uploads using jumbo frames (9k (an MTU of 9000, slightly less than 9K) is pretty standard for the MTU for jumbo frames) go at about 50-60k/sec unless the MTU is lowered to 8232 (which corresponds to 8192k). In my test case, this occurred with my Linux box having an MTU of 9000 and my local machine having one of 9014. I think these both correspond to a 9k MTU, but they are calulated differently (9014 is on an Intel card which I think includes some overhead, and 9000 is on a Broadcom in Linux). Setting the MTU to 8232 on the Linux end worked, with 8233 breaking things again...FTP in DOS with both at 9k works fine...

-Downloading works fine with both set to 9k, although FlashFXP hangs during the transfer and the progress meter either doesn't show anything (with the entire window freezing), or does strange things...Sometimes it hangs entirely, thinking that the file isn't finished, even though it is...I understand that this may just be the limit of pushing over 40,000k/sec to it...

If it matters, both upload and download buffers in FFXP were set to 256k...

MxxCon · 03-18-2005, 10:18 PM

um, on ethernet networks MTU is limited to 1500 bytes

9000, 8192k, 9014, 8283, 8233, etc
where are you getting these numbers from?!

n0xlf · 03-18-2005, 10:22 PM

It's called jumbo frames, and it is a gigabit ethernet specification for LANs because 1500 causes too much overhead and doesn't allow for the full potential of gigabit ethernet...You have to have ethernet cards and switches that specifically support jumbo frames...

http://sd.wareonearth.com/~phil/jumbo.html

MxxCon · 03-18-2005, 10:33 PM

ok, didn't know about that.

have you tried different buffer sizes?
largest value isn't always the best

n0xlf · 03-18-2005, 10:51 PM

I did, but it didn't make a difference, as expected, since we are talking about the difference between 50k/sec with the proper MTU, and 50,000k/sec with the lowered one...

n0xlf · 04-25-2005, 12:43 PM

Build 1078 still does this same thing, FYI...

bigstar · 04-25-2005, 01:52 PM

Try setting the tcp/ip buffer size in flashfxp to default, this will use windows default and perhaps this will give you better performance.

Apart from that I'm not really sure why the speed is much slower, maybe you could use something like Ethereal and monitor the packets to see exactly what's going on.

Linkster · 04-25-2005, 02:05 PM

Also, all your devices on the network must support jumbo frames, as well as your switch (if you are using one). Many gigabit switches, especially consumer level, do not support jumbo frames.

n0xlf · 04-25-2005, 02:47 PM

Everything supports jumbo frames on my network...Using FTP in a DOS window, I see 40,000+k/sec...Using FlashFXP, I see 52k/sec...

Let me know if there is anything specific I can help test for ya...

Hetfield · 04-25-2005, 02:53 PM

Well did you try what bigstar suggested (Try setting the tcp/ip buffer size in flashfxp to default). That should make FlashFXP use the default windows frame size just like your ftp.exe in the dos window.

n0xlf · 04-25-2005, 02:57 PM

Yes, it is at default right now and I have experimented with a lot of different sizes....

Linkster · 04-25-2005, 04:25 PM

sounds like something is really fubar'd...have you tried installing a fresh copy of FlashFXP into a new directory?

n0xlf · 04-25-2005, 11:05 PM

I have, but I don't think that is the issue...It must have something to do with the way FFXP is handling the packet size, as I don't think it is a coincidence that setting the MTU to 8232 (which is EXACTLY 8k or 8192 bytes after subtracting overhead) works fine...

Where 8k comes in to play though, I have no idea...

bigstar · 04-26-2005, 12:46 AM

Have you had a chance to try a packet monitor?

At the moment I don't have the proper hardware to simulate your network environment.

You might also try this test and post your results
http://www.dslreports.com/tweaks

n0xlf · 04-26-2005, 11:16 AM

I haven't tried a packet monitor, but I will do that next...I've always used the tweaks on speedguide.net under the generic patches, but I'll post the dsl reports tests too...