Re: [RRG] Ivip's fix for tunnel o-head, PMTUD & fragmentation problems

[Robin Whittle <rw@firstpr.com.au>]

Hi Stephane,

I hadn't heard of RFC 4950 before.  It involves changed router
functionality to send back a more informative ICMP message when a
packet is undeliverable (such as with Traceroute TTL hitting zero)
when the packet has an MPLS header.

My proposal has a broadly similar goal, but is rather different,
because it involves altering the Traceroute software at the sending
host so it recognises the ICMP messages generated by unmodified
routers, where those routers are in the tunneled part of the path.

Thanks for confirming my understanding that Traceroute is not used
as part of any application or other protocol.

By the way, I think that what I propose for Ivip:

  http://www.firstpr.com.au/ip/ivip/pmtud-frag/

should work equally well for LISP-CONS, LISP-NERD, eFIT-APT and TRRP
- except that the Traceroute won't work for routers in tunnelled
part of the path, since none of these proposals have the outer
header's source address being that of the sending host.

  - Robin


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