!FIX! for Connection Issues (Lag, 90K, etc)

[KisaiTenshi]

mileage can vary with this depending on vendor and their implementation of the feature.

The reason it probably makes a difference probably has more to do with poor driver implementation combined with even poorer network infrastructure. To give an example, even if I disable nagle on my connection, it has no effect with this ISP, however the previous ADSL hardware it totally made a difference. I had to disable ECN (on a realtek chip) to play Mass Effect 2, but no other game.

What people should do before they dink around with this setting, because turning it off wholesale may break something.
Go to an administrative command prompt and type:
netsh interface tcp show global

You'll see something like this
Querying active state...

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State : enabled
Chimney Offload State : enabled
NetDMA State : enabled
Direct Cache Acess (DCA) : enabled
Receive Window Auto-Tuning Level : normal
Add-On Congestion Control Provider : ctcp
ECN Capability : enabled
RFC 1323 Timestamps : disabled

then type
netsh interface tcp show chimneystats

Idx Supp Atmpt TMax PMax Olc Failure Reason
--- ---- ----- ---- ---- --- --------------
22 No -n/a- 0 0 0 -n/a-
33 No -n/a- 0 0 0 -n/a-
25 No -n/a- 0 0 0 -n/a-
26 No -n/a- 0 0 0 -n/a-

If you see something like above, the TOE isn't even being used. So disabling it at the driver level is unlikely to change anything.

You can then force these settings off to troubleshoot things one at a time with:
netsh int tcp set global chimney=disabled
netsh int tcp set global ecncapability=disabled
netsh int tcp set global congestionprovider=none
netsh int tcp set global rss=none

Note do not set all of these at once, only set them to see if it fixes it, if it doesn't fix it, restore it to what it was before. In particular that last feature, receive side scaling (rss) can change the CPU load quite significantly.

[KisaiTenshi]

Just to bump this a little...

netsh interface tcp add chimneyapplication state=disable application="C:\Program Files (x86)\SquareEnix\FINAL FANTASY XIV - A Realm Reborn\game\ffxiv.exe"

Should disable TOE features as per the "seems like it fixed it" in the OP just for FFXIV, but I can't test it since my connection works fine.