Paul E. Erkkila writes:
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.
Without getting into whether this is a good idea - I suspect many service providers would disable such a capability - one of the nice aspects of traceroute is that it uses the usual packet forwarding path until the last hop. In other words, it's a little hard to break the normal packet forwarding mechanism without breaking traceroute too. This charcteristic would be hard to preserve with such a solution.
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.
You do have to make sure that tunnels always move packets closer to their destination, yes.