Leatrix applies what is known as a TCP ACK fix by modifying the TCPAckFrequency value.
What's TCPAckFrequency?
From
"As specified in RFC 1122, TCP uses delayed acknowledgments to reduce the number of packets that are sent on the media. Instead of sending an acknowledgment for each TCP segment received, TCP in Windows 2000 and later takes a common approach to implementing delayed acknowledgments. As data is received by TCP on a particular connection, it sends an acknowledgment back only if one of the following conditions is true:
- No acknowledgment was sent for the previous segment received.
- A segment is received, but no other segment arrives within 200 milliseconds for that connection.
Typically, an acknowledgment is sent for every other TCP segment that is received on a connection unless the delayed ACK timer (200 milliseconds) expires. You can adjust the delayed ACK timer by editing the following registry entry."
---SNIP---
Entry:
TcpAckFrequency
Value Type: REG_DWORD, number
Valid Range: 0-255
Default: 2
Description: Specifies the number of ACKs that will be outstanding before the delayed ACK timer is ignored.
Why does this help?
By modifying the TCPAckFrequency option you can make it so your computer responds to packets more immediately. Read "What's TCPAckFrequency?" to understand why there is a delay in the first place. By default, your computer will delay 200ms or 2 outstanding ACKs before sending acknowledgements. This delay is what Leatrix targets.
Windows XP and 2003 users must have
installed for TCPAckFrequency to work.
You could manually make the required registry modifications for the same effect with relative ease, but if you aren't computer-savvy then you're better off not doing it.
Why does it affect some people and not others?
This could happen for many reasons. Some users might have already applied the fix manually or via some other software unknowingly. It could also be a result of the difference in frequency in packets between users (because of area, activity, server, day/time), operating systems, packet loss, etc... it is difficult to specify all of the possible influences.
