like i said before Hahn, MTU is set by your ISP, thats why i suggest to use MTU detection only when running the TCP analyzer.'
When you know MSS (MSS=MTU-40) you can decide what RWIN you suppose to have.
Cos RWIN has to be multiple with your MSS for a optimized packetusage.
Unfortunely alot of ppl dosent follow the step in right order, also skip a few steps in my guide. Also mix TCP optimizer tweaks with Cablenut tweaks....
Alot of ppl with less MTU then 1500 use TCP optimizer, that force up your MTU to 1500. That only give fragmated packages and problems like above.
Also some routers set your MTU lower then your ISP, in some cases you can increase MTU in router,
If you cant, use the MTU your router use.
VanBuren