Thanks for those coments, which I cut, because I think they can now be turned 
to text. You asked a question about one comment, see below:
GF:
Could the WG consider to also add the first two sentences to the security 
considerations?
Bob:
Sorry, which two sentences?
These were the two sentences, the rest of the para explained what PMTUD was, 
and probably could be left to the reader:
  "Packetization Layer Path MTU Discovery (PLPMTUD) [RFC4821] does not
  rely upon network support for ICMP messages and is therefore
  considered more robust than standard PMTUD.  It is not susceptible to
  "black holing" of ICMP message."
Gorry