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[Vaskez]

Originally posted by Memnoch: Actually, Vask, if you could explain some of this stuff to me, it's not exactly userfriendly. I've downloaded DR TCPIP and also gone to that site you mentioned, here are the results of my tweak test. It looks like my MTU is 1480, and I've put my TCP receive at 64240. Have I done the right thing?[/QB]

The receive window RWIN is the number of bytes that you can receive before your comp sends an acknowledgement to the computer you are communicating with. Therefore if this is very high (i.e. the receive window is big) then you receive loads of bytes in one go withouth acknowledging. This means there is less overhead i.e. traffic sent because you are sending less ACKs. However if there is an error in transmission then the computers won't notice until the receiver window is sent and the lack of an acknowledge (ACK) is noticed. So you don't wanna set it too high either because then the whole window of bytes has to be resent if an error occurs. Am I being clear? Therefore I think that 64000 or whatever is too high for your RWIN- did the tweak test suggest this? I'd be surprised if it did - it usually suggests values between 10000 and 20000 and that's where mine is.

About MTU - this is the maxiumum transmission unit - the maximum number of bytes you can send in one packet. If this is small then each packet has few bytes and there is lots of TCP overhead - i.e. loads of extra bytes sent - you know all the ones marking the end and start of packets etc. So you want the MTU as high as possible to minimise overhead. However, if it is too high then your ISP can't handle it and it fragments the packet (breaks it up into 2 smaller pieces) and this wastes time. So you see you want the MTU as high as possible without letting fragmentation occur. 1480 sounds ok - I mean the ideal for my area is known to be 1458 even though the windows 2000 default is 1500 so a tweak improved it.

A good way to get the best MTU for your ISP is like this:
Open a command window. Type : ping -f -l [packet size] [ISP address]
for example my ISP is pipex so I would try : ping -f -l 1400 www.pipex.com
1400 is the MTU in bytes. Now you need to keep using that command, increasing the value 1400 until you get a message that the packet needs to be fragmented. So if at 1430 the ping comes back ok but at 1431 you get the fragmentation message then 1430 is the value you take. Now add 28 (because of TCP/IP overheads) to this value and this is your best MTU for your ISP. Using this method I confirmed what I was told on a tweaking forum: 1458 (1430+28) is best for my ISP. There is also a way to calculate your RWIN yourself but the value the tweak test gives you, should be ok.

Phew - this should help you get an extra bit of performance if your lack of performance is due to these settings not being optimal. The above is my explanation - there are also instructions here if anyone needs more help: http://www.zensupport.co.uk/ADSL/USB....asp?URL=tweak

[ 02-03-2003, 10:29 AM: Message edited by: Vaskez ]

[Vaskez]

Oh and if you are worried about Dr. TCP - don't be - it's just a shortcut to save you editing the registry directly. Remember to reboot for settings to take effect.
For MTU - enter it in the Dial-up(RAS) MTU box.

[Memnoch]

Thanks for that Vask...I'm doing some diagnostic tests to work out my optimum RWIN. It was originally set at 17800 but I changed it to 64000 and I think I'll change it back, as soon as I do these ping tests. Learning on the fly here.

[Memnoch]

Originally posted by Vaskez: Oh and if you are worried about Dr. TCP - don't be - it's just a shortcut to save you editing the registry directly. Remember to reboot for settings to take effect. For MTU - enter it in the Dial-up(RAS) MTU box.

So what do I do with the other MTU box (the one on the bottom right)? Leave it blank?

[Yorick]

Results

2.7 megabits per second

1MB file download 3.1 seconds

RatingCompared to all connection types worldwide, yours is fantastic

[Vaskez]

Yeah I mean thinking logically 64000 for RWIN is great as you only have to send an acknowledgment every 64K bytes. But what if there's an error? It won't notice until 64K is sent (quite a long time in computer terms!) and then 64K will have to be resent. If you know you have a very low packet loss/ error rate on your connection (the tweak test can show you this too) maybe you can try RWIN this high - there's really no straight answer, it also depends on which site you are connected to and this varies all the time depending on where you're browsing. You have to experiment with RWIN.

Yeah in Dr, TCP I leave the other MTU window on the bottom right blank cos it won't let me type anything but if you can type then just put the same value as in the other one or leave it blank.
There was a time when my connection was really bad - around 130kbps (now it's more like 430kbps see ) and that's when I learned all this about tweaking. Some people on the pipex forums reported huge increases in speed after changing the MTU - for some it doesn't do anything - but it's worth a try - your connection seems ok already but you might be able to get an extra 5% or so out of it - let me know

Somewhere else I read that it's good to have your RWIN as an integer multiple of your MTU - this makes sense right? Otherwise you'd be sending ACKs halfway through packets or something - if that's even possible?

[ 02-03-2003, 10:57 AM: Message edited by: Vaskez ]

[Vaskez]

Originally posted by Yorick: Results 2.7 megabits per second 1MB file download 3.1 seconds RatingCompared to all connection types worldwide, yours is fantastic

Bah! Rich bastard for having T1 or something! Bah!
However, it's still crap compared to the connection at my university. I downloaded windows 2000 service pack 2 full install a while back (105MB) in 2.5 seconds!!

[ 02-03-2003, 11:05 AM: Message edited by: Vaskez ]

[esquire]

"2003-02-03 11:41:20 EST: 3196 / 478
Your download speed : 3196110 bps, or 3196 kbps.
A 390.1 KB/sec transfer rate.
Your upload speed : 478411 bps, or 478 kbps."

*Kisses cable modem*

We should also be posting what our connections cost [img]smile.gif[/img]
My 800Kb-1.4Mb is a whopping $40 US per month.

[Arledrian]

Mine doesn't cost me anything at all really, it's a service of the university campus. I mean I probably pay fees for things like this at the beginning of the school year, but it's peanuts.