* Check scaling setup:
* Turned off scaling to 0 as root:
sysctl -w "net.ipv4.tcp_window_scaling=0"
* To maintain the changes after a restart, include the file S99sysctl.sh:
#!/bin/sh sysctl -w "net.ipv4.tcp_window_scaling=0"
chmod +x /usr/syno/etc/rc.d/S99sysctl.sh
Slow connection and email attachments download to 0 kb
Configuration of operating systems
TCP Window Scaling is implemented in Windows since Windows 2000. It is enabled by default in Windows Vista / Server 2008 and newer, but can be turned off manually if required.
Linux kernels (from 2.6.8, August 2004) have enabled TCP Window Scaling by default. It chooses the good value of the option by default. The configuration parameters are found in the /proc filesystem, see pseudo-file /proc/sys/net/ipv4/tcp_window_scaling and its companions /proc/sys/net/ipv4/tcp_rmem and /proc/sys/net/ipv4/tcp_wmem
Scaling can be turned off by issuing the command sysctl -w “net.ipv4.tcp_window_scaling=0” as root. To maintain the changes after a restart, include the line “net.ipv4.tcp_window_scaling=0” in /etc/sysctl.conf.
FreeBSD, NetBSD and Mac OS X
The default setting for FreeBSD, NetBSD and Mac OS X is to have window scaling (and other features related to RFC 1323) enabled.
To verify their status, a user can check the value of the “net.inet.tcp.rfc1323” variable via the sysctl command:
A value of 1 (output “net.inet.tcp.rfc1323=1”) means scaling is enabled, 0 means “disabled”. If enabled it can be turned off by issuing the command:
sudo sysctl -w net.inet.tcp.rfc1323=0
This setting is lost across a system restart, to make it permanent it must be written in the /etc/sysctl.conf configuration file, that can be accomplished via the command:
echo 'net.inet.tcp.rfc1323=0' | sudo tee -a /etc/sysctl.conf