Re: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-11.txt

["Templin, Fred L" <[e-mail]>]

Hi Tom,

> -----Original Message-----
> From: Tom Herbert [mailto:[e-mail]]
> Sent: Friday, August 07, 2015 10:04 AM
> To: Templin, Fred L
> Cc: [e-mail]
> Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-11.txt
> 
> On Mon, Aug 3, 2015 at 9:07 AM, Templin, Fred L
> <[e-mail]> wrote:
> > I have a comment on this draft. In Section 3.2, it says:
> >
> >   "However, a GRE ingress node can verify tunnel capabilities by sending
> >    a 1280-byte IPv6 packet addressed to itself through the tunnel under test."
> >
> > This text is missing the point that the GRE ingress is only the source of
> > the delivery packet and is *not* the source of the payload packet.
> > This means that, if the 1280-byte probe packets take a different path
> > than the data packets, then the probes can fail to detect paths where
> > the MTU is insufficient.
> >
> > In order to fix this, the GRE ingress would need to make all delivery
> > packets look the same to the network whether they carry probes
> > or data packets. This means that the procedures specified in  RFC2983
> > (diffserv and tunnels) and RFC6438 (flow label and tunnels) MUST be
> > disabled if the 1280 byte probing recommendation of this draft is
> > followed. By disabled, I mean set the DSCP and flow label in the
> > delivery header to 0. The draft can either say this and cite the RFCs,
> > or remove the recommendation for probing with 1280 byte probes.
> >
> Fred,
> 
> I don't think your fix is sufficient. There are already deployed
> devices that will parse the inner GRE headers to perform ECMP.
> Generally, we can never guarantee that any two packets will follow the
> same path through a multi-path network, and simultaneously testing all
> possible paths is a known hard problem.

That being the case, is sending isolated probe packets to
presumably detect a path MTU characteristic meaningless?

Thanks - Fred
[e-mail]

> Tom
> 
> > Thanks - Fred
> > [e-mail]
> >
> >> -----Original Message-----
> >> From: I-D-Announce [mailto:[e-mail]] On Behalf Of [e-mail]
> >> Sent: Sunday, July 19, 2015 10:10 PM
> >> To: [e-mail]
> >> Cc: [e-mail]
> >> Subject: I-D Action: draft-ietf-intarea-gre-ipv6-11.txt
> >>
> >>
> >> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> >>  This draft is a work item of the Internet Area Working Group Working Group of the IETF.
> >>
> >>         Title           : IPv6 Support for Generic Routing Encapsulation (GRE)
> >>         Authors         : Carlos Pignataro
> >>                           Ron Bonica
> >>                           Suresh Krishnan
> >>       Filename        : draft-ietf-intarea-gre-ipv6-11.txt
> >>       Pages           : 10
> >>       Date            : 2015-07-19
> >>
> >> Abstract:
> >>    Generic Routing Encapsulation (GRE) can be used to carry any network-
> >>    layer payload protocol over any network-layer delivery protocol.  GRE
> >>    procedures are specified for IPv4, used as either the payload or
> >>    delivery protocol.  However, GRE procedures are not specified for
> >>    IPv6.
> >>
> >>    This document specifies GRE procedures for IPv6, used as either the
> >>    payload or delivery protocol.  It updates the GRE specification, RFC
> >>    2784.
> >>
> >>
> >>
> >> The IETF datatracker status page for this draft is:
> >> https://datatracker.ietf.org/doc/draft-ietf-intarea-gre-ipv6/
> >>
> >> There's also a htmlized version available at:
> >> https://tools.ietf.org/html/draft-ietf-intarea-gre-ipv6-11
> >>
> >> A diff from the previous version is available at:
> >> https://www.ietf.org/rfcdiff?url2=draft-ietf-intarea-gre-ipv6-11
> >>
> >>
> >> Please note that it may take a couple of minutes from the time of submission
> >> until the htmlized version and diff are available at tools.ietf.org.
> >>
> >> Internet-Drafts are also available by anonymous FTP at:
> >> ftp://ftp.ietf.org/internet-drafts/
> >>
> >> _______________________________________________
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> >> Internet-Draft directories: http://www.ietf.org/shadow.html
> >> or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
> >
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