Hi Ron, > -----Original Message----- > From: Ronald Bonica [mailto:[email protected]] > Sent: Thursday, April 23, 2015 8:18 AM > To: Templin, Fred L; [email protected] > Subject: RE: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-07.txt > > Fred, > > If we can't probe a tunnel, we can't do GRE at all. Ever. Not with IPv4, not > with IPv6, not with anything. > > MTU issues aside, before activating a tunnel, we must be certain that the > tunnel can carry a 1-byte packet from GRE ingress to egress. > If we don't do that, we risk black-holing traffic. This is why nearly all GRE > implementations have some type of proprietary probing > mechanism.
I said earlier that I am fine with going ahead and probe with a small packet (I said 100 bytes, but 1 byte would be fine too) to see if the GRE ingress is alive. But, that probe does nothing to test for a particular MTU. > Beyond suggesting that the probing mechanism use a 1280-byte payload, we have > put the details of that probing mechanism out of > scope for this document. If a 1280 byte probe (which becomes 1280+ENCAPS bytes following encapsulation) succeeds along one path of a multipath, but would have failed along another path, then there is possibility for black holing. And, there is no way for the ingress to know that there may be ECMP or LAG on the path to the egress. Hence, having the ingress probe for the purpose of minimum MTU detection is problematic if there may be some kind of multipath. Thanks - Fred [email protected] > > > Ron > > > -----Original Message----- > > From: Templin, Fred L [mailto:[email protected]] > > Sent: Wednesday, April 22, 2015 6:32 PM > > To: Ronald Bonica; [email protected] > > Subject: RE: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-07.txt > > > > Hi Ron, > > > > So, this gives way to the following, which may be the best we can do if we > > can't probe: > > _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
