On Jun 25, 2014, at 6:39 PM, Alexander Neilson
I guess I was expecting if blocking of needs fragmentation wasn’t too frequent then MTU sizes would start to grow through transit and then as people upgraded PMTUD would start to use larger MTU sizes end to end as links improved.
PMTU-D sometimes has issues because of inappropriate filtering of ICMP/ICMPv6. That being said, 1500 is going to be the most pervasive MTU for quite some time.
I guess I was thinking people would have done those silly things more (as per the MTU size not growing on the internet) and therefore EDNS would have size issues. Is it more that fewer people have these silly config errors? or that DNS has a robust fallback position trying smaller EDNS sizes / alternatives to get a useful reply?
The latter.
You're worrying about non-issues - if these were major problems, the Internet wouldn't function. EDNS0 has been in pervasive use for something like 15 years, so it isn't something new or exotic.
;>
Get your transit with 1500 MTU, and you'll be fine. It's good that you're already thinking of IPv6 - more people should - and you should design your applications, services, network, et. al. to support it, as well as make it an RFP item as you noted. But it's going to be a while before it becomes critical.
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Roland Dobbins