> As regards the implementation of such a selection, one can immagine
> different possibilities, trading off simplicity and selectivity.
> E.g. putting two explicit 1 byte start/end indexes in the IPMP header
> (an IPMP router can write a path record only if the TTL of the packet is
> within the range) or using a very few bits (an IPMP can write a paket
> only if the TLL ends with the same bit pattern).
other approaches include laying out path records which are blanked out
except for the TTL field, which are set to whatever TTLs you're interested
in.
Matt, I was going to reply to this but then I realized that I was not sure
if you were giving this as an example of a practical method of performing
this function. Or if you were just giving it as an example of an approach
which you would also consider to not be "tightly constrained and easy to
implement".