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Old 08-18-2006, 05:11 AM   #1
linux_mando
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Linux change TCP kernel Parameter for TCP DELAY ACK TICKS


Can anybody help me.

I am using debian sarge.

1. Where can i find the TCP kernel parameter for TCP DELAY ACK TICKS. This is available in windows registry (TcpDelAckTicks) ? I tried grep'ing most of the kernel params from sysctl -a but could not find any.

2. How do i change its default value ?

Any info would be of great help.

Thanks a lot in advance !!
 
Old 08-18-2006, 08:35 AM   #2
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Where can i find the TCP kernel parameter for TCP DELAY ACK TICKS.
Could I ask why you would want to do that? Or is it just because MICROS~1 offers the knob (cuz of its excellent stack behaviour, prolly) and so should Linux? Have you looked into the meaning of / enabling / or switching between Westwood and Vegas?
 
Old 08-18-2006, 12:21 PM   #3
linux_mando
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Re

I have a windows server and we needed the same settings for our debian linux server with the tcp ack delay and the global irtt as set in the windows server.
After your valuable info i have gone through the westwood and vegas TCP Congestion Control Algorithms. But i think my kernel does not support it (needs rebuild).

below is the output from my linux box
-----------------------------------------------------------------------------------
# sysctl -a| grep congestion
error: "Operation not permitted" reading key "net.ipv4.route.flush"
net.ipv4.tcp_congestion_control = bic

# sysctl -w net.ipv4.tcp_congestion_control=htcp
error: "No such file or directory" setting key "net.ipv4.tcp_congestion_control"

# sysctl -w net.ipv4.tcp_congestion_control=bic
net.ipv4.tcp_congestion_control = bic

# sysctl -w net.ipv4.tcp_congestion_control=reno
net.ipv4.tcp_congestion_control = reno

# sysctl -w net.ipv4.tcp_congestion_control=vegas
error: "No such file or directory" setting key "net.ipv4.tcp_congestion_control"

# sysctl -w net.ipv4.tcp_congestion_control=westwood
error: "No such file or directory" setting key "net.ipv4.tcp_congestion_control"
-----------------------------------------------------------------------------------

How do i change the TCP ACK Delay Time with westwood or in vegas



Thanks,
 
Old 08-20-2006, 10:51 AM   #4
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I have a windows server and we needed the same settings for our debian linux server with the tcp ack delay and the global irtt as set in the windows server.
Hmm. Doesn't convince me but you probably know what's "best" in your situation.


But i think my kernel does not support it (needs rebuild).
Yes, you need a rebuild to use congestion control.


How do i change the TCP ACK Delay Time with Westwood+ or in Vegas
You don't use those to change it and it's not a sysctl knob either: grep "define.*TCP_DELACK_M[AINX].*((" /usr/src/linux/include/net/tcp.h . If changing it breaks whatever I don't want to know.
 
Old 08-21-2006, 10:59 AM   #5
linux_mando
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Thanks for the info

I have one more query :

What is the default delay ACK time in linux?

Is it 200 ms or is it dynamic ?
 
Old 08-22-2006, 09:20 AM   #6
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Is it 200 ms or is it dynamic ?
Search the asm include files for the HZ macro values.
You'll see that on x86 its 100, meaning 10 milliseconds.
 
  


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