Upload speed limited on WinXP machine?

[#1]

This is not strictly a router or BB question, but I'm guessing some of you folk will have a better clue about it than I do.
Got 80/20 FTTC service a few weeks ago and it's working really well - absolutely worth the money and trouble. Nearly 70MBps downlink speed as shown by speedtest.net, with much less variation over the day than I used to have with ADSL2.
However, I'm confused about the upload speed on my WinXP desktop workhorse box.  I see only about 10.5Mbps up, whereas other machines on my LAN (one Win7, one Ubuntu 12.04) get around 16Mbps uplink.  This is pretty reliable and consistent, with minimal variation from test to test.
Things I've already eliminated:

• It's nothing to do with wireless.  I don't use WiFi for my main machines.  They're on wired gigabit Ethernet.


• It's not the machine's CPU horsepower or its Ethernet interface, because I can push data around my home LAN at nearly the full Gigabit rate.


• It's not my router, because all machines on the LAN go through the same port of the same router (I have a GbE switch on my side of the router, so only one of the router's LAN ports is in use).


• It's not the specific browser.  Chrome, Firefox and IE all behave similarly.


• There is no other significant network traffic at the time I run the test.

Any ideas?  Anyone seen this, know of weirdo registry settings that might affect it, etc?
thanks in advance
Jonathan

[#2]

Try swapping the GbE ports, just in case it's a dicky port.

[#3]

hmmm, that would have been fairly unlikely because - as I mentioned - the same machine can happily push files around my LAN at near enough full GbE rates, nearly 100X faster than the BB upload.  But I tried it anyway just now, and it made no difference.
The machine is used all day every day, so I think I would have noticed if the port or network switch were flaky or intermittent.
Thanks for the suggestion anyway.
Jonathan
dick:quote

[#4]

Try http://community.plus.net/library/settings/guide-to-rwin-mtu/ see if that applies.

[#5]

Quote from: Anotherone

Try http://community.plus.net/library/settings/guide-to-rwin-mtu/

Looked very interesting, and the checker reported uplink MTU smaller than necessary, but after setting path MTU discovery ON and rebooting, nothing has changed significantly.  The setting really did take effect - I looked in the registry (bleaurgh) and indeed, in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters I find EnablePMTUDiscovery=1.  Unfortunately I didn't check what its value was before I tried the change-and-reboot.
Ah well, never mind.  10Mbps is a lot better than nothing, and in due course I'll probably move over to a Linux box for any internet-facing stuff that needs high upload speeds.
Thanks for the suggestions.
Jonathan

[#6]

Head scratching here at the moment, but someone else may have some ideas. I might have missed something as well So keep checking.

[#7]

See what happens if you disable the firewall/anti virus

[#8]

Quote from: Oldjim

disable the firewall/anti virus

Whoa, thanks Oldjim.  That's it.
Windows Firewall seems to make a small difference - around 0.5Mbps in each direction, but that could be just random fluctuations in the speed test.
The antivirus, though (Trend Micro) is really clobbering my uplink!  No significant impact on downlink, but uplink goes from 10.5Mbps with antivirus active,
to 16.5Mbps when the AV is disabled!
Looks like a support ticket to Trend Micro (or, maybe, a faster machine)... and thanks to Oldjim and Anotherone for their input.
Jonathan

[#9]

Support Ticket to Trend Micro, and if they aren't helpful post back and bin it when your sub runs out if it's paid for, if not and they don't help, bin it now and try another 'good' freebie.

[#10]

Problem solved, but still not understood.

• Trend Micro responded reasonably promptly, but with a completely incomprehensible boiler-plate response clearly aimed at their internal staff rather than customers, including a zip archive of stuff I was supposed to use, but no password to decrypt said archive.  Oops.


• I complained, got a quick and courteous response with a suggestion to upgrade to a more recent version of the AV tool (not the virus patterns, which were already up to date).


• With the new version installed, I got the same slowdown in uplink speed even with AV disabled - I had to uninstall it to get the BB performance back to normal.


• They also asked me to use their diagnostic tool to capture information while runing a test.  It slowed my BB connection to a crawl, so I don't believe it can be collecting usefully representative information.  Worse, it generated 12MB of opaque log data which I choose not to send to Trend Micro - I just don't know what I'm sending.

So... out with that AV, install Avira's free product which seems to get good writeups, and everything is hunky-dory again with no measurable loss of BB speed due to the AV.
Thanks for the encouragement and guidance.  Now I can sign up for the ISPA trial with confidence!
Jonathan

[#11]

Well, I'm glad you got that sorted. AV, Firewall's and Anti-Malware software with Real-Time protection can cause these sort of issues. I've had AVG on 2 machines, one of which blew-up a few weeks back, and I'm considering a different AV on a rebuilt machine, currently looking at Avast which I also have on an older machine. Glad you are finding Avira OK.

[#12]

I moved from AVG to Avast a while back and found it fine (once I'd turned on gaming mode so it stopped announcing 'virus database has been updated!' in a feminine computerised voice that frequently made me jump!). I've since moved on to Microsoft Security Essentials, and can't see that changing any time soon - it's lightweight, doesn't bother me and works well
</2p>

[#13]

^That VERY annoying American voice. I HATE it. I have my own sound files, but the damn program always reinstates those god awful defaults after a program update. GRRR.

[#14]

another +1 for Avast from me but yes the voice was awful (and quite surprising if you forget to turn your speakers down after listening to some loud music!)