Why 256960 Rwin in the Patches?

andrewe77 · Post by **andrewe77** » Fri Feb 16, 2001 12:41 am

Ok, I know that speedguide states that the rwin should be based on (MTU-40) times an integer while still being less than 65535. But, I just read the Q224823 - Description of Windows 2000 TCP features which states that:

"If there is a scaling factor, the initial window size of 65,535 bytes is always used."

Is this the case for Windows 98 as well?

haze · Post by **haze** » Fri Feb 16, 2001 7:55 am

My opinion~~~~~~~~~~ no one using a residential broadband connection needs to have a Rwin that's that high. It's impossible to use a "one size fits all" patch when every user has a different latency and Rwin must take into account the latency of your connection.

[ 02-16-2001: Message edited by: haze ]

andrewe77 · Post by **andrewe77** » Fri Feb 16, 2001 9:49 am

Ok, so using my ping times, what equation would I use to calculate the rwin that I need??

rmrucker · Post by **rmrucker** » Fri Feb 16, 2001 10:26 am

The MSKB article you quote is not in agreement with the RFC's (specifically, RFC1323). The MSKB shows a table and explains that ALL window sizes over 65535 are multiples of 65535.

For example, if the "scale factor" is 2, the scaled window is 262,140 -- regardless of what you have entered into your RWIN value. I have never seen this anywhere else and this is in complete DISagreement with RFC1323. I must beleive this is simply WRONG.

dannjr · Post by **dannjr** » Fri Feb 16, 2001 10:40 am

Originally posted by rmrucker and discused in full and quite well I might add 5 long pages with links and more http://forums.speedguide.net/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=2&t=007975

haze · Post by **haze** » Fri Feb 16, 2001 2:46 pm

"Ok, so using my ping times, what equation would I use to calculate the rwin that I need??"

You need to find your average ping, easier said than done. Try pinging about 100-200 different sites and then get the average OR you can try this program ~~ http://www.dslreports.com/front/doctorping.zip

Take the SCORE*1.5
Now multiple that by the bandwidth you are paying for or capped at. Divide that by 8 and add 25%.

example;
score 50*1.5=75
capped at 2000kbps*75=150000
150000/8=18750
18750+25%=23437

Now for those of you who think Rwin must be a multiple of MSS, with a MSS of 1460 this Rwin of 23437/1460=16.05
If you really must have a Rwin that is a multiple of your MSS then take (in this case)
MSS of 1460*16=23360 and use that as your Rwin.

Garrett67 · Post by **Garrett67** » Fri Feb 16, 2001 3:17 pm

Haze,

Where are you getting that calculation from?

dannjr · Post by **dannjr** » Fri Feb 16, 2001 3:58 pm

No where did you get that from...

Garrett67 · Post by **Garrett67** » Fri Feb 16, 2001 4:03 pm

although its very confusing to me this says alot
http://forums.speedguide.net/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=2&t=007975

Garrett67 · Post by **Garrett67** » Fri Feb 16, 2001 4:06 pm

ok, I have to ask this.

What is the difference between defaultRcvWindow and GlobalMaxTcpWindosize?

andrewe77 · Post by **andrewe77** » Fri Feb 16, 2001 5:53 pm

I read the RFC1323 specification and could see nothing in it that says that the rwin must be a multiple of the MSS and be less than 65535. Could someone tell me where this idea was originated?

haze · Post by **haze** » Fri Feb 16, 2001 7:41 pm

My info is based on latency and Rwin size

(test from dslreports)
DefaultRcvWindow (RWIN) is 32120
Your RWIN limits you @28.2ms to 9112kbps
Your RWIN limits you @200ms to 1284kbps

Rwin limits you to speed depending on your ping (ms). You do need a buffer zone over your capped speed so if you do hit a server thats got high latency you will not turn into a turtle. As you can see, I'm well over my line cap (2000kb) @ 28.2ms but at 200ms I'm under that cap but still will get good speed.

Why have a huge Rwin when it is not needed?
Has anyone considered the possibility of packet loss with a Rwin that is to big? Some say it happens, some say it does not!

One thing I do know is that with a 2000kbps line I do not need a Rwin that gives me the potential to recieve 234,625kbps

By the way, with this Rwin I average a little over 1900kbps (that's 95% of my line cap)

Lobo · Post by **Lobo** » Fri Feb 16, 2001 7:46 pm

Now if that ain't a speech from dsl reports I never heard one, Hey Cablenut, respond

haze · Post by **haze** » Fri Feb 16, 2001 8:04 pm

I have used Cablenuts program and I have nothing bad to say about it. My speeds were the same either way.

At the moment I run Linux so Cablenut tweak is out for me.

My point is "Are these monster Rwins needed?"

Lobo · Post by **Lobo** » Fri Feb 16, 2001 8:12 pm

I don't know, but the smaller the RWIN on mine the slower I go

rmrucker · Post by **rmrucker** » Sat Feb 17, 2001 11:34 am

andrewe77- you won't find that in the RFC. That's because both Microsoft and SpeedGuide do't clearly follow the RFC.

*Check your Private Message box and I'll fill you in.*

dannjr · Post by **dannjr** » Sat Feb 17, 2001 4:24 pm

Originally posted by rmrucker:
andrewe77- you won't find that in the RFC. That's because both Microsoft and SpeedGuide do't clearly follow the RFC.

*Check your Private Message box and I'll fill you in.*

Ohhh common share with the world...hehehehe