North American Network Operators Group

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Re: IP over SONET considered harmful?

  • From: Joseph Malcolm
  • Date: Fri Mar 20 14:44:27 1998

Yakov Rekhter writes:
>To be more precise, the issue is that an ingress LSR is required to
>copy IP TTL into Tag-TTL, *and* the egress LSR is *required* to copy
>Tag-TTL into IP TTL. The problem you mentioned in your message would be
>solved if the egress LSR would just decrement IP TTL by 1, rather than
>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".

And somehow it is different that ATM and frame relay also "break"
traceroute just as much, if by "break" it is meant that one cannot see
the "physical" (not they they are really seeing that) topology?

>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

It would be nice were that an option at least.

>(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).