On Fri, 16 Oct 1998, I Am Not An Isp wrote:
differently than any other packet. Unless, of course, the user manually modifies the default behavior with filters or something - which can be done to any address just as easily.
That argument is so bogus that I am amazed you are trying to use it. Saying that using private addresses for links doesn't break PMTU-D if there is a MTU change just because it requires other things in place to actually break is quite irresponsible. People are clueless enough already, don't confuse them with half truths. The reality is, that for the Internet today where a large number of people filter such addresses, using private addresses does break PMTU-D. They _CAN_ put filters on any address just as easily; if I don't want traffic from you, I can filter it. If I don't want traffic from addresses that shouldn't be sending traffic or that I use internally, I will filter it. If you have a MTU change on a router using private link addresses, then the second filter implies that the first will implicitly be true anyway for at least some traffic. It is _NOT_ correct to say that filtering either your address or private address space has just the same effect.