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RE: Thoughts on increasing MTUs on the internet
-----Original Message----- From: owner-nanog@xxxxxxxxx [mailto:owner-nanog@xxxxxxxxx] On Behalf Of Stephen Sprunk Sent: Friday, April 13, 2007 10:32 AM To: Mikael Abrahamsson Cc: North American Noise and Off-topic Gripes Subject: Re: Thoughts on increasing MTUs on the internet >PMTU Black Hole Detection works well in my experience, but unfortunately MS doesn't turn it on by default, which is > where all of the L2VPN with <1500 MTU issues come from; turn BHD on and the problems just go away... (And, as others >have noted, there's better PMTUD algorithms that are designed to work _with_ black holes, but IME they're not really > needed) I wish I'd had your experience. PMTU _can_ work well, but on the internet as a whole, far too many ignorant paranoid admins block PMTU, mostly by accident, causing all sorts of unpleasantness. Clearing DF only takes you so far. Unless both ends are aware, and respond apppropriately to the squeeze in the middle, you're back to square one. Unless there were some other method of MTU Discovery implemented, depending on something like PMTU discovery may fail just as dramatically on larger packets as it does on 1500byte now.