North American Network Operators Group

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Re: MTU of the Internet?

  • From: Dave Siegel
  • Date: Wed Feb 04 15:30:37 1998

> Peter Ford writes:
> > Several people have noted to the Microsoft Support and Product groups that
> > they want the Windows 95 PPP MTU to be set to 576 (down from 1500).  this
> > change is in Windows 98.
> > 
> > The reason for this change cited by many customers is that many ISPs have
> > 576 MTUs set "inside" their networks and packets get fragmented.
> 
> I know of no modern networking media in common use at ISPs that has an
> MTU below 1000, and have not heard of ISPs with MTUs that low. 

I know of none either, but perhaps someone from AOL/Compuserv could comment
on their architecture.

Some of those older or original custom networks may have different
configurations.  If memory serves, John Goltz told me that he wrote his
own network protocol for the Compuserv servers to interact with each other.
No idea if this was ever a part of compuserv's Internet service...

It's worth remembering that it only takes one extremely large nationally visible
provider like AOL to say to Microsoft "ISPs like us use 576 size MTU's, so fix
win95".

Dave

-- 
Dave Siegel				[email protected]
Network Engineer			[email protected] (alpha pager)
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