The tosfix helper command sets the Type of Service (TOS) field in packet headers based on the suggestions given by Erik Hensema in iptables and tc shaping tricks (http://www.docum.org/docum.org/faq/cache/49.html).
The following TOS values are set:
- All TCP ACK packets with length less than 128 bytes are assigned Minimize-Delay, while bigger ones are assigned Maximize-Throughput
- All packets with TOS Minimize-Delay, that are bigger than 512 bytes are set to Maximize-Throughput, except for short bursts of 2 packets per second
The tosfix command must be used before the first router or interface.