[15767] in North American Network Operators' Group
Re: IP over SONET considered harmful?
daemon@ATHENA.MIT.EDU (Paul E. Erkkila)
Fri Mar 20 16:51:12 1998
From: "Paul E. Erkkila" <pee@frontiernet.net>
In-Reply-To: <199803201733.JAA13486@puli.cisco.com> from Yakov Rekhter at "Mar 20, 98 09:33:17 am"
To: yakov@cisco.com (Yakov Rekhter)
Date: Fri, 20 Mar 1998 15:23:17 -0500 (EST)
Cc: alan@globalcenter.net, nanog@merit.edu
> 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
