guys im Capped at 1.5mbps down and 128kbps up how can i ge the most out of it I have attbi right now my rwin is 64240 why?
because of this thread i found check-->Ok this one is a refinement on something I already posted but deals with a specific area. The specific area is the NIC card and what it sees as the actual TCP Window size.
yes, yes, I know "But I already did the TCPWindowSize thing in the registry and its screaming along" (or not). But did you ever stop to think what the actual window size your using really is? I know all about speedguide and their tcp window size tester thing and how they say your all good and stuff, and about the almost exact opposite advice from dslreports. Guess what, they are both right. Yep, thats correct, both right.
Ever notice how when you first install XP the connection seems to just be "smoother" with browsing, may not be getting 10MB's on the speed but it is nice and smooth, you'll at least get 2 MB/s on the cable modem. This is because the window size its using when forst installed is 65536 which is the optimum size for MS/s TCP/IP. So what you have less flow controll from the NIC and less interaction for flow control from XP because it really happy with this size window.
Ok, your connected to the cable modem with a NIC card. So whats the true window size your using? "Huh, my registry says 256960 (or something), so thats what i'm using". Nope, wrong, thats what your trying to use, what your actually using is what the NIC card sees. TCP is doing the rest, but what your physically using is what the NIC can see and this is what it sees. To demonstrate click on this link:
hcp://system/netdiag/dglogs.htm
or if clicking on it doesn't work create a shortcut with this as the path, just as it says, dont change it. this will open up the winXP built in network diagnostics. When it opens click on the "scan your system" link and let it do its thing. When it gets done, scroll down to where it says network adapters and expand the branch. then sroll down under this branch and look for the TcpWindowSize entry. see the number? it may be in the 40xxx area somewhere. If the number you see begins with 60 then skip this whole post as you don't need it. This is what the NIC is actually using for a window size. Dissapointed? yep...sure you are.
the real trick to setting a correct TcpWindowSize in the registry is to get the unscalled window size as close to 65536 as possible. But after you subtract all the overhead you wind up with less than that sometimes. Well guess what. the max window size the NIC is going to possibly see is 65536 less the TCP/IP overhead and the NIC card overhead and the NIC drivers overhead. You can't control these things (well the TCP/IP overhead a little).
write down that number you saw in the diagnostics and keep tabs on it, were going to change it. keep in mind that i'm using 3Com 905B-TX cards and have only tested with those cards.
Open up our old friend regedit again.
browse to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters
add these reg keys - as DWORD
"DefaultReceiveWindow"
"DefaultSendWindow"
now modify each one with the value of the large window size you have at the reg location:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
make "DefaultReceiveWindow" and "DefaultSendWindow" the same size as TcpWindowSize for starters.
now reboot
run the diagnostics again. Remember the first number that you wrote down? compare it to the new number. If you didn't see a change then change the value (double it) of the "DefaultReceiveWindow" and "DefaultSendWindow" entries - reboot and try again.
Eventually your going to get to the number 60352 or there abouts. This will be the largest possible unscaled window that your NIC will see that is less than 65536 (ref the MS knowledge base).
adjust the "DefaultReceiveWindow" and "DefaultSendWindow" entries till you get the number as large as possible. When you get the number as large as possible then its time to fine tune a bit. Decrease the number by 10% and check again, repeat this till a change is noticed that the number is dropping. When the number begins to drop it means that this is the optimum value for your "DefaultReceiveWindow" and "DefaultSendWindow" entries and no more can be gained by changing these entries.
LOBO EXPLAIN PLEASE IM GOING CRAZY TRYING TO FIGURED THIS OUT!!!!!!!!!!!!!!!!!!!!!!1
