Hi Ron, > -----Original Message----- > From: Int-area [mailto:[email protected]] On Behalf Of Ronald Bonica > Sent: Thursday, April 16, 2015 3:43 PM > To: [email protected] > Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-07.txt > > Fred, > > In Section 3.2, we put implementation details of the probing mechanism out of > scope.
But, Section 3.2 is all about probing for a specific size - 1280 bytes. > Regardless of MTU and fragmentation issues, a robust GRE implementation > requires a probing mechanism. Without such a probing > mechanism, a GRE ingress node might activate a GRE tunnel when the egress was > not reachable at all. This would result in black- > holing. Probing for liveness, I can understand. Like maybe send a little 100 byte packet and see if it boomerangs back to you. But, probing with 1280 might not tell the whole story if there are ECMP or LAG branches on the path. Also, while probing, why not also check to see if it supports GRE fragmentation? > Since RFC 2784 doesn't specify a probing mechanism (or even require one) most > vendors have developed proprietary probing > mechanisms. These proprietary mechanism must deal with the problems of LAG > and ECMP. However, because the probing > mechanisms aren't IPv6 specific, and because they are proprietary, we put > them out of scope. Your document Section 3.2 is asking for probing the IPv6 minMTU of 1280 plus the encapsulation overhead. That might work on one path of a multipath but actual data packets might take a different path. This does not make me happy because I also want to do some probing of my own. But, it seems like something we may need to worry about. Thanks - Fred [email protected] > > Ron > > > ------------------------------ > > > > Message: 2 > > Date: Tue, 14 Apr 2015 17:12:53 +0000 > > From: "Templin, Fred L" <[email protected]> > > To: "[email protected]" <[email protected]> > > Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-07.txt > > Message-ID: > > <2134F8430051B64F815C691A62D9831832E495AD@XCH-BLV- > > 504.nw.nos.boeing.com> > > > > Content-Type: text/plain; charset="us-ascii" > > > > I will say also that the act of probing in general is a bit troublesome. In > > particular, when there is Equal Cost MultiPath (ECMP) how can you tell that > > the probe packets will follow the same path as the data packets? > > > > Thanks - Fred > > [email protected] > > > > [RPB] > *** > > _______________________________________________ > Int-area mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
