Modem tweaks changing the RWIN settings

[Tartan Giant]

Hi Guys,

Has anybody had any experience about tweaking their 56k modem by altering the RWIN settings in the registry ?

My RWIN is 2144 which is considered too low, and is the basic cause of poor download speeds.

[Ausatco]

Yep, Tartan, I've had a play, but I can't say the results are startling. Maybe a marginal improvement.

There are a number of parameters that are interdependent - MTU, MSS and RWIN.

You don't say if you're dialup or some other connection. MTU depends on whether you're using a dialup connection or something else. Assuming dialup, 'cos that's the most common (I think):

MTU should be set to 576.
MSS is MTU minus 40, = 536
RWIN should be 4 or 8 times MTU, ie 2144 or 4288. The Windows default, 8192, is not a required multiple. Sorry, I don't know how you should choose between the multiples. The prog I use to set this stuff says experiment!

There is another setting, TTL. The default is 32. My prog says set it to 64.

The prog I use is InternetBOOST from www.bonzi.com (http://www.bonzi.com)

I get pretty good results, but I also use SSH and port forwarding, which considerably accelerates the flow of text-based data. (HTML, which makes your browser paint its page, is text and is therefore accelerated.)

Hope this is of interest, and would be pleased to try to help out with SSH and port forwarding if you're interested.

AA

[Tartan Giant]

Hello there Ausatco

Thanks for the reply - that's the stuff I'm after !

I'm using a standard Dial Up through an ordinary "copper wire" phone line here in England. The line quality is probably not all that great but I’m stuck with it and refuse to pay BT £40 a month for a dual-line.

I've been using a site called PCPitstop www.pcpitstop.com (http://www.pcpitstop.com) which has been instrumental in my understanding of these MTU/MSS/RWIN things. I must say, it is an outstanding dedicated site for the likes of us.

The diagnostics says my default RWIN of 2144 (I'm W98ME) is far too low. Your mention of 8192 does not figure in my set-up but as you say, "experiment" seems to be a recognised method of finding the right settings.
The packet size of 576 seems to be the OK setting for a kick-off though.
The Time To Live (TTL) setting they say for Win98 is 128 "and need not be changed". I'll believe them !!!

I had a look at another site www.dslreports.com/tweaks/Registry (http://www.dslreports.com/tweaks/Registry) that suggests an RWIN of 65535 "which is a value that without knowing more about your connection speed and typical ping time, is going to get you pretty close to the best speed you can get".
So I'm about to take the plunge and REGEDIT to that value.

Maybe before I do you could tell me more about this SSH and port forwarding business please.

Cheers,
TG

[Ausatco]

G'day TG,

First up, I would not pursue settings mentioned on www.dslreports.com/tweaks/Registry (http://www.dslreports.com/tweaks/Registry) . I had a quick look at the site - it seems to me it is devoted to broadband via DSL. You and I (and most folks outside USA, I suspect) are using dialup, which is NOT broadband. Broadband settings are wrong for we dialup users.

Concur your remarks re the pcpitstop site - used it to check my browser and thought it was great. Perfect for technodabblers :).

You say the pcpitstop diagnostics said RWIN of 2144 is far too low and also that 8192 does not figure in your setup....

As I said in my first reply, I use InternetBOOST and am pleased with the result. Here's what the help file has to say about RWIN:-
<font face="Verdana, Arial, Helvetica" size="2">The Receive Window (RWIN) value is the maximum number of bytes of data that can be buffered, pending the receipt of an acknowledgment packet back from the sender. Typically, the RWIN value should be a multiple of 2-10 times the maximum segment size (MTU-40).

Default (8192)
This sets the RWIN value to the Windows default. Under Windows 95, this value is 8192, which should not be used (because it is not evenly divisible by the default maximum segment size, it can force the packet to be resent repeatedly when the buffer is full). You can improve performance by setting this to a lower value such as 4 times your MSS (MSS = MTU - 40).

Multiple
This allows you to set the RWIN value to a specific multiple, with the actual value calculated using the MTU value. It is recommended that you set the multiple to 4 or 8.

Custom
This allows you to specify a custom RWIN value. This is not recommended unless you fully understand the implications of using a non-standard value.</font>

InternetBOOST's RWIN picklist multiples are 4, 6, 8 and 10. Note that in the "default" paragraph, they recommend an RWIN value of less than 8192 and suggest 4 time MSS, which for dialup is 2144. This contradicts the advice you received from pcpitstop, which said a higher value should be used! I trust you are no longer confused :)

Your reference to www.pcpitstop.com (http://www.pcpitstop.com) had me exploring and I found a link to iSpeed for Windows at www.hms.com (http://www.hms.com) . I downloaded and tried it, and I think it's considerably better than InternetBOOST, and half the price. Plus you get 30 days free trial.

Here's what iSpeed's help file says:-
<font face="Verdana, Arial, Helvetica" size="2">RWIN determines how much data the receiving computer is prepared to receive. An RWIN value that is set too high will result in greater data loss if the packet is lost or damaged in transit. An RWIN value that is set too low will produce very poor throughput. Typically, an RWIN value should be set that is 3 or 4 times the size of the Maximum Segment Size (MSS).</font>

Note iSpeed's recommendation of 3 to 4 times MSS, versus InternetBOOST's 4 or 8 times. I'm afraid I don't have the knowledge to resolve that difference of opinion http://www.pprune.org/ubb/NonCGI/frown.gif However, 4 times MSS (2144) works well on my dialup system.

You must surely be going about this the hard way, tweaking your system through regedit :) I reckon you can do it easier through a connection tweaking utility, such as InternetBOOST or iSpeed for Windows. Either of these will give you easy, simultaneous access to all the parameters, instead of the one-at-a-time you must be doing through regedit. Of the two I've looked at, iSpeed from HMS would seem to be the better one. FWIW, I use another prog from HMS (an anti-spam utility) and I'm very happy with his service and update policy.

For SSH and Port Forwarding, have a look at

http://www.zipworld.com.au/~frankp/ttssh/TTERM%20SSH%20Setup.htm .

It's more a "how to set it up" than "how it works". There has been some interest in it locally and the author is updating it, but the principles will be unchanged. Main thing is to download any TeraTerm Pro and ttssh documentation you can find from the links on the site and read and digest!

I use his method and am pleased with it, though set up could be considered daunting for technophobes.

Cheers

AA

[Tartan Giant]

G'Day Ausatco,

Thanks again for going to some considerable trouble trying to help me - and keep me on the right track (DUN instead of DSL etc !).
I see that 8192 is the Win 95 default - that's probably why I've missed it (I'm 98 ME and not impressed with it sorry to say).

I wonder why the two RWIN tweak sites can't agree on the multiple ? Confused....hmmm ....yep !

I have downloaded the ispeed software, but confess……where do I start ? What figures did you put in the various boxes (MTU / MSS / MUTIPLIER / NDI CACHE SIZE / TTL etc etc ) to get a decent speed ?

I’m tying myself in knots trying to get a handle on it all.

Cheers,
TG

[Ausatco]

Afternoon TG, (well, that's what it is down here)

My experience with 98ME is on a friend's computer - he need a fair bit of help. I don't particularly like it either, but put it down to my unfamiliarity with the user interface - a number of things are not where they are in 98SE and it has less DOS (if any), so I get command line withdrawals. Sick, eh? :)

In iSpeed, try for starters:-

MTU 576
MSS 536
RWIN 4x multiplier, then experiment with 8 in another session
TTL 64

I got all these from InternetBOOST and they work for me. Upload and download speed in the pcpitstop tests are good and pcpitstop does not recommend any changes to my system.

I use a 56k modem, but due to telephone technicalities in my location connect at max 44k. I average a sustained download rate on 44k connections of 3.7kB/sec, sometimes 4.0 or 4.1 (measured with Win98's System Monitor), so I'm pretty happy with those settings. It may be worth fiddling with different multiples of RWIN and different TTLs. Let's know how you go.

NDI CACHE - read the iSpeed help file. It's a new one for me, I've never fiddled with it as InternetBOOST doesn't mention it. I will have a play with it in iSpeed now that I have that prog.

Cheers

AA

[Flypuppy]

This site is worth having a nose around in:
http://www.speedguide.net/index.shtml

[Flybywyre]

I had a look at that "pcpitstop" site and have regretted it. I ran one of their scans and since then my computer has developed a mind of its own. I'm slowly getting it back but I have had to re-install IE and tonight I am going to try to re-install windows. For details of my problems see my post on the "click and w a i t" thread above.
Anyone else experienced any problems with the "pcpitstop" site?
Regards
FBW

[This message has been edited by Flybywyre (edited 13 March 2001).]

[Tartan Giant]

FBW/b]
VERY Sorry to hear that !
I've used pitstop to run numerous tests on my PC and it has never "taken over" as it were. I can understand how pis..ed off you must be.

[b]Flypuppy Thanks for that one - like wise on this site - no troubles.

Ausatco
I set the following:
MSS 536
factor 9
RWIN 4824
TTL 128
Which gave me 3.7 KB/sec - nearly as good as your set-up, but my connect speed at the time was only 38,667.
Maybe I'll leave it now ?

Thanks again mate.
TG

[Engineer]

FBW
Pitstop uses activeX so you should disable any software that is used to monitor these ie norton cleansweep etc

[Ausatco]

TG,

Assuming you've set MTU = 576, your MSS of 536 is standard. The other settings are ... interesting. They seem to work well. Out of interest, how did you arrive at them? Trial and error, or an informed source. (There are differences of opinions between informed sources :))

Glad to be of a little help.

AA

[Tartan Giant]

AA

Lots of trial, and lots or errors.

I tried tons of settings and then looking at the history and analysis file in the programme, selected the best combination.

Cheers AA

TG

[Engineer]

Next question is-:

If you have AOL as your ISP will adjusting the registry RWIN MTU MSS and TTL settings increase the down/upload bandwidth or does the software generated AOL dial up adaptor default to the normal 1500 MTU setting when activated

Cheers

Alwalys willing to learn and listen

[Tartan Giant]

Hello Engineer,

I'm not an AOL fan and don't use it; however the ispeedprogramme does have an "ISP Specific" folder for a number of ISP's and when I selected AOL the following settings appeared as default,
MTU 576
MSS 536
RWIN 3216 (produced by a multiplier of 6)

I can only assume this has been a tried and tested set of numbers the makers of ispeed have found to work best.

Hope that helps.

[Ausatco]

TG,

<font face="Verdana, Arial, Helvetica" size="2">For SSH and Port Forwarding, have a look at

http://www.zipworld.com.au/~frankp/ttssh/TTERM%20SSH%20Setup.htm </font>

The page has been updated.

Regards

AA

edited to fix quote.




[This message has been edited by Ausatco (edited 15 March 2001).]

[Tartan Giant]

AA,
Cheers mate......I'll have a look - maybe that's all...ha ha.

Cheers,
TG

[Engineer]

TG thanks for info have downloaded ispeed but cannot locate the info on ISP specific any pointers

Next question is that all these tweaks must amend the registry any ideas which hotkey values are adjusted

Ta

PS Laugh at this one rang AOL Tech support and asked about MTU RWIN etc Reply was we dont know about that :rolleyes: :rolleyes:

[This message has been edited by Engineer (edited 17 March 2001).]

[PPRuNe Dispatcher]

See http://support.microsoft.com/support/kb/articles/q158/4/74.asp

[Tartan Giant]

Hi Engineer,

Run ispeed again, and on the opening page, TOP TOOLBAR, go into Settings and the drop down window will show ISP Specific Settings such as,
AOL
AT&T
Compuserve
Mindspring
MSN
Prodigy
Tritium

The registry Settings it plays with are all listed under the Help files.
Hit these keys whilst running ispeed,
HELP
CONTENTS
REGISTRY
DISPLAY

All you need will be there !

Had to laugh about the AOL clowns...
Cheers,
TG

[Engineer]

PD thanks for the web page

TG got it will have a play tonite "never grown up"

Had a play improved the upload connection but still can't squeeze the extra on the download portion

Another source of info if you want to do it yourself is:-
http://support.microsoft.com/support/kb/articles/Q183/4/37.ASP?LN=EN-GB&SD=gn&FR=0


[This message has been edited by Engineer (edited 18 March 2001).]

[Ausatco]

TG,

Just tried your settings - wow!

MSS 536
RWIN 4829 (9 X MSS)
NDI (which you didn't list) 16
TTL 128

FTP from my ISP consistently 3.66kB/s, which is an improvement on my til-now variable speed at or below that.

From the second Microsoft ftp choice on iSpeed's drop-down list ... wait for it ... 10.3kB/s!!

Microsoft must be doing something funny at their site, 'cos no other site goes that fast. The same speed is reported by System Monitor and Cute FTP. Amazing.

My turn to thank you!

AA

[Tartan Giant]

Ausatco

That's great news mate !

In the best traditions, the thanks are due to others - I just played their tune.

I read all the stuff about SSH and Port Forwarding and I'm still not sure I can fiddle that much; looks a bit too deep for me. I'll think about it more.

Happy surfing.

Cheers,
TG

[Ausatco]

Just found out why that MS test file in iSpeed downloads at 10k - it's an uncompressed graphics file which the modems are compressing on the fly. Should have realised that!

AA