Tweaking Connection under Linux 7.0

Stooge · Post by **Stooge** » Thu Jan 17, 2002 12:09 pm

Ive posted this in the Tweaking forum. Know one replied back,

Im hoping someone here will know. I cant seem to figuer out how to change my rwin under linux, here is my analyser test

TCP options string = 020405b40402080a0003c9550000000001030300
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1448, which is less than MSS because of Timestamps, or other TCP/IP options used.
Default Receive Window (RWIN) = 32120
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 32120
RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
513920 (MSS x 44 * scale factor of 8)
256960 (MSS x 44 * scale factor of 4)
128480 (MSS x 44 * scale factor of 2)
64240 (MSS x 44)
bandwidth * delay product:
Your RcvWindow limits you to: 1284.8 kbps (160.6 KBytes/s) @ 200ms
Your RcvWindow limits you to: 513.92 kbps (64.24 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = ON
Time to live left = 51 hops
TTL value is ok.
Timestamps (RFC1323) = ON
Note: Timestamps add 12 bytes to the TCP header of each packet, reducing the space available for useful data.
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349)= 00000000

blebs · Post by **blebs** » Thu Jan 17, 2002 12:37 pm

To assure you that your not being ignored, I'll post that I haven't a clue. Someone should be around who works with Linux and if not, give Stef a PM, he may know where you need to be looking.

Stooge · Post by **Stooge** » Thu Jan 17, 2002 3:35 pm

Well i know found out how to change the rwin. One problem though, The number i add isint the number that gets put in. for example if i add the number 256960 the number that will show up will be 318000 or whatever.

What would be a good rwin for cable ?

blebs · Post by **blebs** » Thu Jan 17, 2002 6:04 pm

I'm using 256960 on Win98se and cable. It works fine for me.
From what I see in your test, you need to find out how to shut off timestamping then find out why RWIN isn't showing the correct value. I wish I knew something about Linux!

Stef is a Linux person and should be able to help you on this.

master7 · Post by **master7** » Thu Jan 17, 2002 8:38 pm

You say Linux 7.0. Are you talking about Red Hat 7.0 or what? Please include your distro information if it's not Red Hat.

Stef · Post by **Stef** » Thu Jan 17, 2002 9:02 pm

Which kernel version are you running?

I can give you a complete listing of the tune'able IPv4 parameters in Linux, just give me a version number

BTW, you can also tweak routes on your network by using the Linux route utility.

Lets say we wanted to increase the MSS and TCP window of our default gateway

First, delete the default gateway:

route del default gw $Gateway

Then re-install that gateway with specifying the MSS and TCP window:

route add default gw $Gateway dev $Interface mss $mss window $tcpwin

Where:
$Gateway = your ISP default gateway ( IP address or hostname )
$Interface = the interface connected to your ISP's network
$mss = MTU - IP headers
$tcpwin = TCP window size in kbytes

If you let me know which DHCP client you are using I can give you directions on how to edit the configuration file so this is done automatically on every DHCP release/renew/request.

In Linux, we can manipulate anything and everything

Stef

master7 · Post by **master7** » Thu Jan 17, 2002 9:22 pm

In Linux, we can manipulate anything and everything

Amen

Stef · Post by **Stef** » Thu Jan 17, 2002 11:12 pm

Originally posted by Stooge
Well i know found out how to change the rwin. One problem though, The number i add isint the number that gets put in. for example if i add the number 256960 the number that will show up will be 318000 or whatever.

What would be a good rwin for cable ?

SpeedGuide's TCP anyliser isn't accurate. Use the one at DSLReports.

Here's my tweak test, my RWIN is as listed on this URL:

http://monitor.dslreports.com/tweak/blo ... via=normal

BTW, you can get your kernel version two different ways.

One is two execute kernelversion as root. Another is to run cat /proc/version as root.

Stef

Stooge · Post by **Stooge** » Fri Jan 18, 2002 2:18 pm

Im running Mandrake 7.0,. My kernel is 2.2.14-1mdklinus (gcc version 2.95.2.

Also when i reboot my CPU the rwin goes right back to default. I cant get my rwin to stay after rebooting.

And another question. Ive been looking at my performance Monitor and it shows a large Cache. Takes up all my memory,. Anyway i can decrease the Cache size ?

thanks for the info btw

Stef · Post by **Stef** » Fri Jan 18, 2002 9:55 pm

First, I wouild recomemd that you upgrade to the latest 2.2.x series of kernels. You can get it at http://www.kernel.org

(right now 2.2.20 is the latest stable of that tree)

You need to write a script that resets your desired settings in the kernel. Consult your Mandrake mailling lists for more details, they got Mandrake pro's there.

Linux's disk cache size is calculated at boot and the results are based on total system memory.

You can find more information in the kernel docs and those are over at LinuxHQ.com

Here's one link on the parameters that affect VM and disk access:

http://www.linuxhq.com/kernel/v2.2/doc/ ... m.txt.html

Here's a few links that details the finner tunning of the kernel's IPV4 variables.

http://www.linuxhq.com/kernel/v2.2/doc/ ... l.txt.html

http://www.psc.edu/networking/perf_tune.html#Linux

http://www.linux.com/enhance/tuneup/dat ... 000815.htm

Have fun reading

Stef