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Re: MTU of the Internet?
-----Original Message----- From: Robert E. Seastrom <firstname.lastname@example.org> To: email@example.com <firstname.lastname@example.org> Cc: email@example.com <firstname.lastname@example.org> Date: Wednesday, February 04, 1998 1:40 PM Subject: Re: MTU of the Internet? <SNIP> </SNIP> >I have no idea where they came up with this "576 internally" nonsense. >Generally whenever one runs into that number it is as a result of >creaky old software that expects to be running over milnet or arpanet. > IPX used 576 forever whenever you had to cross IPX "subnets". The reason was simple. They were lazy. 576 was the least common denominator between Ethernet, TR, and _Arcnet_ Large IPX (LIPX) allowed them to do basically what IP calls Path MTU discovery. Only took them a day short of forever to figure out how to do it. >Are Microsoft stacks known to be broken in the packet >fragmentation/reassembly department? Or are just acknowledging >deficiencies in their path mtu discovery code by setting the MSS in >the basement? I knew they had problems with window length (this from >my friends with long fat pipes)... > With all the paranoids trying to block all ICMP, not just ICMP_ECHO, doesn't that essentially break PMTUD. 576 may not be efficient, but its probably the safest to assume.