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What is the Automatic setting in Windows packet sizes?

TweakMASTER Knowledge Base article KB0039

"Automatic" is the Windows Default setting for MTU. This supposedly permits Windows to automatically adjust its MTU to the optimal settings for a given routing. Nice idea in theory but rather poorly implemented by Microsoft (sound familiar?).

In reality it takes much longer for Windows to "negotiate" these optimal MTU settings, and it is not handled particularly well. Most users will have better luck hard coding some specific MTU settings. The only time it may work ok is if a person uses both dialup and broadband connections at different times, as on a laptop, for example... broadband in the office and dialup on the road. There either a 1500 MTU or "automatic" may work best on average, unless you find it worthwhile to reoptimize your system each time for each type of connection.

Same is true for TCP Receive Window. Windows Default is no visible setting at all (but in reality it defaults to 8192.) This is woefully inadequate for broadband which requires a much higher TCP Receive Window... and for dialup an TCP Receive Window specifically keyed to MTU is generally much more effective.

TweakMASTER handles all MTU and TCP Receive Window settings with ease and complete accuracy. It will automatically detect your operating system and all your Network Interfaces in almost all cases and allow you to adjust the settings effortlessly to help you determine which settings provide the most optimal connection for your system.