copying Tag-TTL into IP TTL. However, doing this introduces another problem - it breaks traceroute. And there are enough folks in the MPLS WG who think that the ability to traceroute through all the LSRs is an "unalienated right".
Without going to far into the traceroute source , would a solution to this problem be a modified traceroute that "understood" and could report Tag/MPLS "hops" as well as the normal method? There would need to be some way of identifying which devices were forwarding using Tag/Mpls and which were not, as well as getting and reporting the information. I think it falls into the same category of tracing cell forwarding in ATM without having access to the equipment doing the work.
In view of the above here are some of the possible avenues:
(a) try to get "rough consensus" with the MPLS WG to allow decrement IP TTL by 1 on egress (rather than copy Tag TTL into IP TTL), or
(b) talk to your favorite vendor(s), and ask the vendor(s) to put a "knob" that would decrement IP TTL by 1 on egress (rather than copying Tag TTL into IP TTL).
Alan and I discussed the "knob" solution before, it seems to solve the problem, but under certain circumstances a packet could end up being forwarded forever because of (mis)configuration. -pee