Windows 95 had a "hidden" default for MTU set in the registry at 1500. This was appropriate for LAN's and all Ethernet connections, but can be very inefficient when using a PPP dialup connection. This has now been recognized by Microsoft and was corrected in Windows 98 to some extent.
How to read, calculate and set MTU in Windows, Linux and Feb 20, 2017 1500 MTU = bad ? - Comcast XFINITY | DSLReports Forums Feb 07, 2003
Tweak Win2K Server registry to improve TCP/IP performance
Aug 14, 2012 Change MTU in Windows Server - krypted Sep 17, 2013
Sep 17, 2013
Jan 11, 2011 What is MTU Size and What Should I Set it to? - Home What Exactly Is MTU? MTU stands for Maximum Transmission Unit. This is just one of many settings that you may have to adjust to fully optimize your router. The MTU size is a setting that determines the largest packet size that can be transmitted through your system. These packets are measured in octets, or eight-bit bytes. How can I test and change the MTU size of WAN interfaces