Re: Non-Last Small IPv6 Fragments

[Nick Hilliard <[e-mail]>]

Tom Herbert wrote on 13/01/2019 19:48:
> Yes, but then what are the rules? AFAICT from RFC8200 the minimum
> fragment data is eight bytes. I think it's going to be a hard sell to
> convince OS developers that they should accept such packets just
> because the spec requires it-- the DOS attack vector in this is too
> obvious.
No intermediate node is going to fragment anything other than the last 
frame to 8 bytes, or at least if it does, the network is so severely 
crippled that fragmentation is the least of its problems.  It would be 
fair to assume that if host B receives a stream of fragments where the 
fragment size is unfeasibly small, then the fragmentation was done by 
host A.

This is not a good DOS vector, to be honest.  There's nothing to stop 
random small packets being streamed from A to B and it doesn't matter 
much whether they are fragments of a larger packet or not.

There doesn't seem to be a compelling case to change the protocol to 
accommodate this particular corner case.  It ranks as annoyance rather 
than a serious threat.

Nick