Dear colleague
    
We would kindly like to inform you about some interesting results in our experiments with "unassigned" icmp-types

http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml

When flooding cisco asa's (a handfull older as well newer models) with "unassigned" icmp type=1, type=2, etc it seems that the asa is computing the "number of connections / sec" differently:
    
X "normal" ICMP's / sec => X connections / sec
    
BUT
    
X "unassigned" ICMP's / sec => one single connection !
    
in other words: DOS-flooding with "unassigned" types is INVISIBLE in the asa connection statistics ;-)
    
Sincerely
Gupta Deva