Hi, Gorry (et al.),
On 2/14/2017 9:23 AM, Gorry Fairhurst wrote:
There is no mention that paths including tunnels can eat ICMPv6 PTB
messages on the tunnel segment, blackholing them, which prevents
reaching the destination.
Nor should there be, IMO.
A tunnel is a link layer to the network whose packets it transits.
ICMPs generated inside a tunnel aren't "eaten", so much as they operate
at a different layer for a different reason (e.g., to tune
ingress-egress source fragmentation of encapsulated packets).
PTB messages inside a tunnel are (IMO) most correctly interpreted by the
ingress (which is an *interface* on a router or host, most correctly
IMO) as changing the MTU of the tunnel as a link. If that MTU change
affects packets that arrive later, then it would be the router where the
ingress is attached that would generate the ICMP, never the (ingress)
interface whose MTU is insufficient.
Again, I'm in the process of updating draft-ietf-intarea-tunnels to be
much more clear on this point (the update should be issued in a day or two).
Joe