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mscom_network_start [2014/05/15 16:09] beckmanf tcp configuration |
mscom_network_start [2016/03/16 09:01] (current) beckmanf [Setup of the Linux test platform / USB Stick] - removed student laptop |
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| Details regarding tcp testing are here: [[http://www.linuxfoundation.org/collaborate/workgroups/networking/tcp_testing]]. | Details regarding tcp testing are here: [[http://www.linuxfoundation.org/collaborate/workgroups/networking/tcp_testing]]. | ||
| - | ==== Setup of the Linux test platform / USB Stick ==== | + | ==== Setup of the Linux test platform ==== |
| - | + | ||
| - | Network tests are done with a network of Ubuntu Linux computers which are connected via an ethernet switch. Students laptops will be part of the setup. If you have a native linux installation, you can use that directly. Follow the steps in [[mscom_linux_setup|Master COM Linux test setup / USB Stick]]. If have a laptop which does not have a native linux installation, then you can use a bootable USB Stick which we provide. | + | |
| + | Network tests are done with a network of Ubuntu Linux computers which are connected via an ethernet switch. | ||
| ==== Laboratory expirements ==== | ==== Laboratory expirements ==== | ||
| Line 179: | Line 178: | ||
| ==== TCP configuration ==== | ==== TCP configuration ==== | ||
| - | Set the maximum write window size for tcp connections | + | === Local memory restrictions === |
| + | Set the maximum window sizes for tcp connections to 512000 Bytes. | ||
| <code> | <code> | ||
| sudo sh -c "echo 512000 > /proc/sys/net/core/wmem_max" | sudo sh -c "echo 512000 > /proc/sys/net/core/wmem_max" | ||
| sudo sh -c "echo 512000 > /proc/sys/net/core/wmem_default" | sudo sh -c "echo 512000 > /proc/sys/net/core/wmem_default" | ||
| + | sudo sh -c "echo 512000 > /proc/sys/net/core/rmem_max" | ||
| + | sudo sh -c "echo 512000 > /proc/sys/net/core/rmem_default" | ||
| sudo sh -c "echo 512000 512000 512000 > /proc/sys/net/ipv4/tcp_wmem" | sudo sh -c "echo 512000 512000 512000 > /proc/sys/net/ipv4/tcp_wmem" | ||
| sudo sh -c "echo 512000 512000 512000 > /proc/sys/net/ipv4/tcp_rmem" | sudo sh -c "echo 512000 512000 512000 > /proc/sys/net/ipv4/tcp_rmem" | ||
| </code> | </code> | ||
| + | === Initial TCP contention window size === | ||
| + | |||
| + | The following section shows how to change the initial contention window size to to 1 MSS. | ||
| + | |||
| + | <code> | ||
| + | fritz@ubuntu:~$ ip route show | ||
| + | default via 192.168.178.1 dev eth0 proto static | ||
| + | 169.254.0.0/16 dev eth0 scope link metric 1000 | ||
| + | 192.168.178.0/24 dev eth0 proto kernel scope link src 192.168.178.33 metric 1 | ||
| + | fritz@ubuntu:~$ sudo ip route change default via 192.168.178.1 dev eth0 proto static initcwnd 1 | ||
| + | fritz@ubuntu:~$ ip route show | ||
| + | default via 192.168.178.1 dev eth0 proto static initcwnd 1 | ||
| + | 169.254.0.0/16 dev eth0 scope link metric 1000 | ||
| + | 192.168.178.0/24 dev eth0 proto kernel scope link src 192.168.178.33 metric 1 | ||
| + | fritz@ubuntu:~$ | ||
| + | </code> | ||
| + | |||
| + | === TCP Congestion avoidance algorithm selection === | ||
| + | |||
| + | The linux kernel provides several algorithms for tcp congestion avoidance. The following code shows how to figure out the available algorithms (here cubic and reno) and set and control the setting. In this example the congestion avoidance algorithm is switched from "cubic" to "reno". | ||
| + | |||
| + | <code> | ||
| + | fritz$ cd /proc/sys/net/ipv4/ | ||
| + | fritz$ cat tcp_available_congestion_control | ||
| + | cubic reno | ||
| + | fritz$ cat tcp_congestion_control | ||
| + | cubic | ||
| + | fritz$ sudo sh -c "echo reno > tcp_congestion_control" | ||
| + | fritz$ cat tcp_congestion_control | ||
| + | reno | ||
| + | </code> | ||