[ppml] Technical reason why /52,/56,/60,/64 are bad

[Kevin Loch]

Christopher Morrow wrote:

> Actually the normal DFZ sorts of devices as listed below will have to
> do lookups to a full 32 bits on many occasions... I suspect the
> trie-based lookups (and tcam lookups) are able today to do at least 32
> bit lookups.

Yes, for example nullrouting DOS attacks or rerouting small subnets 
during migration (or sometimes permanently ugh).  There are many
other examples depending on how close you are to the edges.

If there are 128 bits in the address field we need to be able to route
all 128 bits (quickly).

- Kevin