Fred,
It appears that we disagree and have taken to repeating ourselves.
So, why don't we solicit opinions from the rest of the WG and defer to their
will.
Ron
> -----Original Message-----
> From: Templin, Fred L [mailto:[email protected]]
> Sent: Tuesday, March 31, 2015 4:38 PM
> To: Ronald Bonica; [email protected]; [email protected]
> Cc: Zuniga, Juan Carlos; [email protected]; intarea-
> [email protected]
> Subject: RE: [Int-area] Start of WGLC for draft-ietf-intarea-gre-ipv6
>
> Hi Ron,
>
> I will say again that the minimum IPv6 link MTU is 1280 bytes and so the
> design must account for tunnel paths that include links with such a small
> MTU. The design must also account for nested tunnels-within-tunnels,
> where the MTU seen by the first tunnel ingress may be reduced by
> potentially many layers of additional encapsulation.
>
> But again, the point is that the tunnel ingress cannot legitimately send PTBs
> that report a size smaller than 1280 *and* perpetually drop packets smaller
> than 1280 which is exactly the behavior your text is permitting.
>
> Thanks - Fred
> [email protected]
>
> > -----Original Message-----
> > From: Ronald Bonica [mailto:[email protected]]
> > Sent: Tuesday, March 31, 2015 1:21 PM
> > To: Templin, Fred L; [email protected]; [email protected]
> > Cc: Zuniga, Juan Carlos; [email protected];
> > [email protected]
> > Subject: RE: [Int-area] Start of WGLC for draft-ietf-intarea-gre-ipv6
> >
> > Fred,
> >
> > In the last network that I operated, all interior links had MTU
> > greater than 9k. If I configured a GRE tunnel between two points in that
> network and detected a GMTU less than 1280, it would have indicated one of
> the following:
> >
> > - Phenomenal brokenness
> > - An ICMP PTB-based attack in progress
> >
> > In such cases, operators need some flexibility in how their networks
> > would behave. Why deny them this flexibility by taking away the
> configuration option?
> >
> > Isn't it an operator's prerogative to discard any packet that might degrade
> network performance?
> >
> >
> > Ron
> >
> > > -----Original Message-----
> > > From: Templin, Fred L [mailto:[email protected]]
> > > Sent: Tuesday, March 31, 2015 3:01 PM
> > > To: Ronald Bonica; [email protected]; [email protected]
> > > Cc: Zuniga, Juan Carlos; [email protected];
> > > intarea- [email protected]
> > > Subject: RE: [Int-area] Start of WGLC for
> > > draft-ietf-intarea-gre-ipv6
> > >
> > > Hi Ron,
> > >
> > > > -----Original Message-----
> > > > From: Ronald Bonica [mailto:[email protected]]
> > > > Sent: Tuesday, March 31, 2015 11:38 AM
> > > > To: Templin, Fred L; [email protected]; [email protected]
> > > > Cc: Zuniga, Juan Carlos;
> > > > [email protected];
> > > > [email protected]
> > > > Subject: RE: [Int-area] Start of WGLC for
> > > > draft-ietf-intarea-gre-ipv6
> > > >
> > > > Fred,
> > > >
> > > > Some (if not most) operators maintain networks in which all links
> > > > have MTU greater than or equal to 1500. In those networks, the
> > > > very detection of a GMTU smaller than 1280 indicates brokenness.
> > > > Those
> > > operators, the alternative behavior may be preferable to the default.
> > >
> > > The minimum IPv6 MTU is 1280 bytes; that is how much the link must
> > > deliver no matter what. A GMTU smaller than 1280 does not indicate
> > > brokennesss; it can naturally happen if 1) there is a link with a
> > > small MTU in the path, or
> > > 2) there are multiple tunnel nesting levels, or both.
> > >
> > > As such, sustained dropping of packets less than 1280 is a no-no,
> > > and cannot be specified in a document like this.
> > >
> > > Thanks - Fred
> > > [email protected]
> > >
> > > >
> > > > Ron
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Templin, Fred L [mailto:[email protected]]
> > > > > Sent: Tuesday, March 31, 2015 1:30 PM
> > > > > To: Ronald Bonica; [email protected]; [email protected]
> > > > > Cc: Zuniga, Juan Carlos;
> > > > > [email protected];
> > > > > intarea- [email protected]
> > > > > Subject: RE: [Int-area] Start of WGLC for
> > > > > draft-ietf-intarea-gre-ipv6
> > > > >
> > > > > Hi Ron,
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Ronald Bonica [mailto:[email protected]]
> > > > > > Sent: Tuesday, March 31, 2015 10:18 AM
> > > > > > To: [email protected]; [email protected]
> > > > > > Cc: Zuniga, Juan Carlos; Templin, Fred L;
> > > > > > [email protected];
> > > > > > [email protected]
> > > > > > Subject: Re: [Int-area] Start of WGLC for
> > > > > > draft-ietf-intarea-gre-ipv6
> > > > > >
> > > > > > Hi Fred,
> > > > > >
> > > > > > Inline.....
> > > > > >
> > > > > > Ron
> > > > > >
> > > > > >
> > > > > > > Hi Juan Carlos,
> > > > > > >
> > > > > > > Final passage of Section 3.1 says:
> > > > > > >
> > > > > > > ?However, in an alternative configuration, the GRE ingress MAY:
> > > > > > >
> > > > > > > o discard the IPv6 packet
> > > > > > >
> > > > > > > o send an ICMPv6 Packet Too Big (PTB) [RFC4443] message
> > > > > > > to the
> > > IPv6
> > > > > > > packet source. The MTU field in the ICMPv6 PTB message is
> > > > > > > set
> to
> > > > > > > the GMTU.?
> > > > > > >
> > > > > > > This means that there may be circumstances when the GRE
> > > > > > > ingress sends a PTB reporting a size less than 1280.
> > > > > > > According to RFC2460, Section 5, the standard behavior for a
> > > > > > > host that receives
> > > such a PTB is:
> > > > > > >
> > > > > > > ?In that case, the IPv6 node
> > > > > > > is not required to reduce the size of subsequent packets to less
> than
> > > > > > > 1280, but must include a Fragment header in those packets?
> > > > > > >
> > > > > > > So, hosts that obey RFC2460 Section 5 will see a perpetual
> > > > > > > black hole if the GMTU is smaller than 1280 which is
> > > > > > > probably not what we
> > > > > want.
> > > > > >
> > > > > >
> > > > > > [RPB]
> > > > > > All true. This is why the WG decided to make this the
> > > > > > alternative behavior
> > > > > and not the default behavior.
> > > > >
> > > > > Behavior that is broken is still broken regardless of whether it
> > > > > is alternative or default.
> > > > >
> > > > > > > ?draft-templin-6man-linkadapt? attempts to provide guidance
> > > > > > > to hosts on how to react to PTB messages that report a small size.
> > > > > > > But, as of right now,
> > > > > > > RFC2460 Section 5 is the normative behavior.
> > > > > > [RPB]
> > > > > >
> > > > > > Absolutely correct. The procedures described in Section 5 or
> > > > > > RFC
> > > > > > 246 are
> > > > > normative.
> > > > > >
> > > > > > I don't how this impacts the WG's LC decision regarding the
> > > > > > current
> > > draft.
> > > > >
> > > > > Broken behavior should not be specified, whether alternative or
> default.
> > > > >
> > > > > Thanks - Fred
> > > > > [email protected]
> > > > >
> > > > > >
> > > > > > Ron
> > > > > >
> > > > > > >
> > > > > > > Thanks ? Fred
> > > > > > > [email protected]
> > > > > > >
> > > > > >
_______________________________________________
Int-area mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/int-area
