by ken.louie » Tue Mar 26, 2013 10:50 pm
With AT&T DSL (6 Mb), I used a receive window of 518,400 bytes. I'm still on Win XP so I don't have the RWin auto-tuning that Vista and Windows 7 have. What should I use with Fusion? Should I simply recalculate using Fusion's larger MTU of 1500?

How I arrived at this window size:
1480 Maximum Transmission Unit on former PacBell DSL minus 40 = 1440 Maximum Segment Size
1440 x 45 =64800, largest even multiple of MSS that's less than 64 KB or 65,536, the nominal maximum window size.
With window scaling, I had a choice of the following window sizes,
64800 x 2 ^1 = 129,600
64800 x 2 ^2 = 259,200
64800 x 2 ^3 = 518,400
64800 x 2 ^4 = 1,036,800

My other settings in the Dr. TCP tool from dslreports.com :
Window scaling = Yes
Time stamping = Yes
Selective acks = Yes
Path MTU discovery = Yes
Black hole detection = No
Max duplicate acks = 2
Time to live (TTL) = 128
MTU = 1480

My Fusion connection is 10,352 kbs down / 1,202 kps up