Whirlpool

Hi Guys,
I've been with Adam ADSL2 for a couple of months now, and while my modem syncs as good as I can expect (~7500Kbs, about 4.5 Km from Modbury exchange), my DL speed sucks and doesn't seem to reflect the sync speed. Generally, I feel I'm having a good day if I can DL from an OS site at about ~16KB/s.

Until I started playing with Linux last week. While DLing some additional packages, they seemed to come down pretty quick and the KB/sec seemed high, so I did a speed test by DL the 30MB file from www.adam.com.au/speed. In Linux I maxed out at about 810KB/sec but in XP the same file maxed out at about 230KB/sec.

Screenshots here: picasaweb.google.com/rla...oadbandSpeedTest

This is on the same PC (I boot Linux from an external 4G Flash drive)

Why the HUGE discrepancy? Is there a setting in XP I can change to fix it?

XP sometimes needs tweaking for broadband.
Try www.speedguide.net/analyzer.php and see what it suggest - the red text.
Also look at www.unblocka.com
If linux is ok, a couple of tweaks in XP could fix XP.

edit: also, since this probably isn't Adam specific, you may get more answers in the general or Windows forum.

Actually, as a quick test go to that page www.speedguide.net/analyzer.php
first with Linux, then XP and see what the differences in RWIN, MTU, etc are.
If there's no differences, it could be something else.

Just another reason why Linux is superior!

i will post my experience

on Ubuntu 8.04 I can d/l upto a speed of 1.5MB/sec
but on vista Sp1, the max D/l speed is 1.2MB/sec.

i noticed this different speed differences on both OS several times.

Then I satisfied myself by saying Open source rocks all the way

RobL63 writes...

Why the HUGE discrepancy? Is there a setting in XP I can change to fix it?

/forum-replies.cfm?t=116165

Thanks for the links - I'll check them out when I get home...

It'll be interesting to see if they show a difference between the Linux & XP installs...

Rob.

« Mark R Smith » writes...

/forum-replies.cfm?t=116165

Hi Mark,
Fairly technical post, but there was an interesting post near the end about adding a registry key that looked interesting. I'll check that out as well...

Rob.

thanks mark,
learn something today

RobL63 writes...

a registry key that looked interesting

I'm guessing that's the same as the RWIN that the www.speedguide.net test mentions?
eg. 126960 (MSS x 46 * scale factor of 2)

This RWIN affects the bandwidth * delay product.
eg. Your TCP Window limits you to: 662 kbps (83 KBytes/s) @ 200ms

Fnomnal writes...

XP sometimes needs tweaking for broadband.
Try www.speedguide.net/analyzer.php and see what it suggest - the red text.
Also look at www.unblocka.com
If linux is ok, a couple of tweaks in XP could fix XP.

First of all a big thank you! I went to speedguide as suggested and my numbers were all really low: MTU=576, MSS=536 and TCP receive window=4288 (according to speedguide "Optimised for DialUp"). I downloaded TCPOptimiser and selected "optimal" settings which boosted the numbers to 1492/1452/514008 respectively. I redid the Adam speed test on the 30Mb file and got around 8ooKB/sec download speed - a huge improvement. I can now actually watch YouTube videos in real-time (makes my daughter happy!).

I also did the speedguide analyse while using Linux and the numbers came out to 1492/1452/5888. Even though the TCP receive window is lower than in XP now, it doesn't seem to affect DL speed (still ~800KB/sec).

Screenshots posted at picasaweb.google.com/rla...oadbandSpeedTest as before...

Once again - many thanks for helping me turn my broadband into broadband instead of enhanced dialup!

Great RobL63. I think the XP defaults aren't that great.
Plus, for some people it's possible they have used some tweaking program for dial-up long ago and then forget about it. Then when switching to ADSL, this problem comes up. I think this happened to me when I was on XP.

RobL63 writes...

Even though the TCP receive window is lower than in XP now, it doesn't seem to affect DL speed (still ~800KB/sec).

Because you do not need a large receive window.. the bigger the window, the more data that has to be resent if there is an error, the smaller, the less..

Usually a smaller number is quicker to recover.

I set receive windows to double that of what your linux one is, 11776, not too small, not to large.... quick to recover, and still great download speeds :)

this is intresting my router is set to a MTU of 1500 but www.speedguide.net/analyzer.php says mine is really 1460 MTU. it was my understanding that telstra's backhaul is native ppp over atm which is 1500.

maybe it's just that crappy rim im on :(

Fnomnal writes...

Plus, for some people it's possible they have used some tweaking program for dial-up long ago and then forget about it. Then when switching to ADSL, this problem comes up. I think this happened to me when I was on XP.

Bingo... Now that you mention it, last year some time I found a program that would (supposedly) improve dialup but I found that it made no difference at all... except maybe stuff up future broadband speeds!

btw... currently downloading a file from OS @ 140KB/sec, which is over 10x faster than I was getting before...

NO-U writes...

Because you do not need a large receive window.. the bigger the window, the more data that has to be resent if there is an error, the smaller, the less..

I'll try to remember this if I start noticing any issues as something to try. I just accepted the values generated by TCP optimiser, but it has the option to override it's settings.

Thanks,
Rob...

Fnomnal writes...

Try www.speedguide.net/analyzer.php and see what it suggest - the red text.

I'm not having any real speed issues but out of interest, I'd thought I'd try that site too...

« SpeedGuide.net TCP Analyzer Results »
Tested on: 05.12.2008 10:33
IP address: 219.90.xxx.xxx

TCP options string: 020405840103030201010402
MSS: 1412
MTU: 1452
TCP Window: 66740 (NOT multiple of MSS)
RWIN Scaling: 2
Unscaled RWIN : 16685
Reccomended RWINs: 64952, 129904, 259808, 519616
BDP limit (200ms): 2670kbps (334KBytes/s)
BDP limit (500ms): 1068kbps (133KBytes/s)
MTU Discovery: ON
TTL: 54
Timestamps: OFF
SACKs: ON
IP ToS: 00000000 (0)

Interesting because both the Billion SNMP viewer and my router report LAN MTU as 1500 and WAN MTU as 1492, which is correct.

That site's suggestions were...

- MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput. If you are using a router, it could be limiting your MTU regardless of Registry settings.

- In Windows Vista, unless you have disabled "TCP/IP Auto-Tuning", readings in the Analyzer will only show the Current TCP Window, and the TCP Optimizer will have no effect.
RWIN is not fully optimized (even though it is a comparatively large number). The unscaled RWIN value is lower than it should be. Also, RWIN being close to and above 65535 does not justify the header overhead of enabling TCP 1323 Options. You might want to use one of the recommended RWIN values below.

For optimum performance, consider changing RWIN to a multiple of MSS.
Other RWIN values that might work well with your current MTU/MSS:
519616 (MSS x 46 * scale factor of 8)
259808 (MSS x 46 * scale factor of 4)
129904 (MSS x 46 * scale factor of 2)
64952 (MSS x 46)

All of which I find a bit confusing! Plus I already use their own TCP Optimizer program anyway which is supposed to give me the optimal settings! Running ADSL2+ on a Billion 7402VGP using WinVista 32bit.

Yes, with Vista it seems you don't have to worry as much because Vista dynamically adjusts the window size.
Looking at RobL63's Linux result, it seems that some flavours of Linux also do this - probably regardless of what you set the window size to.

Tests for both of these OS will only show the current TCP window size. For the test results page, I suspect the dynamic window is small, compared to if you do a large file speed test.

I thought the MTU shown in the results page will be the MTU that their server sees. So is it the smallest MTU in the whole end-end route? That is, if your router's MTU is 1492 and your XP MTU is 1500, the result will say 1492?