How to disable TCP slow start in Linux?

linux networking tcp congestion-control
Junho Suh picture Junho Suh · Jun 10, 2013 · Viewed 15.8k times · Source

I am looking for disable TCP slow start mechanism for high-speed network. Currently clients send 100MB flows to random servers with non-blocking 1Gbps link. In my math, the completion time of the flows is less than 1 second.

But the problem is that they cannot reach to a full link bandwidth. In other words, they are finished at slow start phase before getting a full link bandwidth.
Therefore, I want to increase TCP congestion window size to maximum.

Is there anyone who know how to change that value easily without modification the kernel?

Answer

a.m. picture a.m. · Jun 10, 2013

On Linux platforms the SSR setting can be checked and disabled via the following commands:

$> sysctl net.ipv4.tcp_slow_start_after_idle
$> sysctl -w net.ipv4.tcp_slow_start_after_idle=0

Slow start is also used after a connection has been idle, unless this behavior is disabled in 

/proc/sys/net/ipv4/tcp_slow_start_after_idle.

Related questions

Freeing up a TCP/IP port?

netstat -tulnap shows me what ports are in use. How to free up a port in Linux?

Read More
tcp_tw_reuse vs tcp_tw_recycle : Which to use (or both)?

I have a website and application which use a significant number of connections. It normally has about 3,000 connections statically open, and can receive anywhere from 5,000 to 50,000 connection attempts in a few seconds time frame. I have had the problem of …

Read More
How to close a socket left open by a killed program?

I have a Python application which opens a simple TCP socket to communicate with another Python application on a separate host. Sometimes the program will either error or I will directly kill it, and in either case the socket may …

Read More