Geoff Huston writes that he has “seen a number of commentaries and presentations in recent times that claim that IPv6 is identical to IPv4 in every respect except one: namely more addresses. But there is one more rather critical difference, and that is the deliberate change in the IPv6 with respect to MTU handling and packet fragmentation, and this relatively minor change in IPv6 has some really quite critical implications. In this article I’d like to illustrate some of the implications of this change with respect to the IPv6 treatment of packet fragmentation by taking an in-depth look at the IPv6 packet flows and why and how this change to packet fragmentation management can cause service-level disruption.”

To read this article by Geoff Huston in full, see:
www.potaroo.net/ispcol/2009-01/mtu6.html