Re: New Version Notification for draft-bonica-6man-frag-deprecate-00.txt

[Mark Andrews <[e-mail]>]

In message <[e-mail]>, Usman Latif writes
:
> I have the following suggestion:
> 
> IPv6 hosts can try to gain knowledge of the path MTU to a destination. If the
>  path blocks or filters PMTUD etc, then the host should revert to 1280 bytes 
> else the hosts can use a higher packet size. 
> This mechanism would make Fragment header redundant anyway

No, it doesn't.

> The only implication of the above mechanism would be that network providers '
> must' support 1280 byte IPv6 packets in all situations
> 
> 
> Regards,
> Usman
> 
> 
> On 25/06/2013, at 5:00 AM, [e-mail] wrote:
> 
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> > Today's Topics:
> > 
> >   1. RE: New Version Notification for
> >      draft-bonica-6man-frag-deprecate-00.txt (Ronald Bonica)
> >   2. Re: New Version Notification for
> >      draft-bonica-6man-frag-deprecate-00.txt (Fred Baker (fred))
> >   3. Re: New Version Notification for
> >      draft-bonica-6man-frag-deprecate-00.txt (Ole Troan)
> >   4. RE: New Version Notification for
> >      draft-bonica-6man-frag-deprecate-00.txt (Templin, Fred L)
> > 
> > 
> > ----------------------------------------------------------------------
> > 
> > Message: 1
> > Date: Mon, 24 Jun 2013 16:38:06 +0000
> > From: Ronald Bonica <[e-mail]>
> > To: George Michaelson <[e-mail]>, "[e-mail] 6man-wg"
> >    <[e-mail]>
> > Subject: RE: New Version Notification for
> >    draft-bonica-6man-frag-deprecate-00.txt
> > Message-ID:
> >    <[e-mail].
> outlook.com>
> >    
> > Content-Type: text/plain; charset="us-ascii"
> > 
> > 
> > I'd like to understand the basis of these assertions. I believe what I am s
> eeing, on the edge, suggests there is in fact V6 fragmentation in both TCP an
> d UDP.
> > 
> > 
> > Hi George,
> > 
> > It would be helpful if you could describe:
> > 
> > 
> > -          Where your observations are being made
> > 
> > -          What percentage of traffic is fragmented
> > 
> > -          What kinds of packets are being fragmented
> >                                                Ron
> > 
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL: <http://www.ietf.org/mail-archive/web/ipv6/attachments/20130624/2d5885
> 47/attachment.htm>
> > 
> > ------------------------------
> > 
> > Message: 2
> > Date: Mon, 24 Jun 2013 16:50:04 +0000
> > From: "Fred Baker (fred)" <[e-mail]>
> > To: Tore Anderson <[e-mail]>
> > Cc: "[e-mail] 6man-wg" <[e-mail]>
> > Subject: Re: New Version Notification for
> >    draft-bonica-6man-frag-deprecate-00.txt
> > Message-ID:
> >    <[e-mail]>
> > Content-Type: text/plain; charset="iso-8859-1"
> > 
> > 
> > On Jun 24, 2013, at 12:45 AM, Tore Anderson <[e-mail]> wrote:
> > 
> >> * Fred Baker (fred)
> >> 
> >>> On Jun 22, 2013, at 2:29 AM, Tore Anderson <[e-mail]> wrote:
> >>>> - When a SIIT translator receives an IPv4 packet with DF=0 that
> >>>> would result in an IPv6 packet that would exceed the IPv6 link MTU,
> >>>> it will split the original packet into IPv6 fragments.
> >>> 
> >>> It *could* fragment the IPv4 packet and send it in two unfragmented
> >>> IPv6 packets.
> >> 
> >> Wouldn't doing IPv4 fragmentation before translation to IPv6 be
> >> logically identical to this other case I mentioned?
> > 
> > Ah. You're correct. I was thinking about tunnels.
> > 
> >>>> - When a SIIT translator receives an IPv4 fragment, it will translate
> >>>> this into one or more IPv6 fragments.
> >> 
> >> I can't see how simply omitting the Fragmentation header in the IPv6
> >> output could work here, as the node receiving those two unfragmented
> >> IPv6 packets would see the first one containing a truncated L4 payload,
> >> while the second one would be just garbage as it doesn't include a L4
> >> header.
> >> 
> >> Tore
> > 
> > -----------------------------------
> > "We are learning to do a great many clever things...The next great task
> > will be to learn not to do them."
> > 
> > - G. K. Chesterton (1874-1936)
> > 
> > 
> > 
> > 
> > 
> > 
> > ------------------------------
> > 
> > Message: 3
> > Date: Mon, 24 Jun 2013 13:37:41 -0400
> > From: Ole Troan <[e-mail]>
> > To: Sheng Jiang <[e-mail]>
> > Cc: "[e-mail] 6man-wg" <[e-mail]>,    "Fred Baker \(fred\)"
> >    <[e-mail]>
> > Subject: Re: New Version Notification for
> >    draft-bonica-6man-frag-deprecate-00.txt
> > Message-ID: <[e-mail]>
> > Content-Type: text/plain; charset=us-ascii
> > 
> >>> I suppose I'm the contrarian
> >> 
> >> +1. For me, this draft looks dangerous by proposing to deprecate fragmenta
> tion with only one-side observation. This draft does not give enough analysis
>  on these existing fragmentation use cases, particularly these use cases the 
> fragments within a single domain.
> >> 
> >> On other side , only disallowing fragmentation to be used among domains ma
> y helpful to reduce the operational complex.
> > 
> > this draft should help us tease out answers to the question:
> > "if we wanted to deprecate IPv6 fragmentation, could we?"
> > 
> > then when we know the collateral damage, it will be easier to answer the ot
> her question:
> > "should we deprecate IP layer fragmentation or not".
> > 
> > cheers,
> > Ole
> > 
> > ------------------------------
> > 
> > Message: 4
> > Date: Mon, 24 Jun 2013 17:50:36 +0000
> > From: "Templin, Fred L" <[e-mail]>
> > To: "Fred Baker (fred)" <[e-mail]>, Tore Anderson <[e-mail]>
> > Cc: "[e-mail] 6man-wg" <[e-mail]>
> > Subject: RE: New Version Notification for
> >    draft-bonica-6man-frag-deprecate-00.txt
> > Message-ID:
> >    <[e-mail]>
> > Content-Type: text/plain; charset="us-ascii"
> > 
> > Hi Fred,
> > 
> >> -----Original Message-----
> >> From: [e-mail] [mailto:[e-mail]] On Behalf Of
> >> Fred Baker (fred)
> >> Sent: Sunday, June 23, 2013 4:12 PM
> >> To: Tore Anderson
> >> Cc: [e-mail] 6man-wg
> >> Subject: Re: New Version Notification for draft-bonica-6man-frag-
> >> deprecate-00.txt
> >> 
> >> 
> >> On Jun 22, 2013, at 2:29 AM, Tore Anderson <[e-mail]> wrote:
> >>> - When a SIIT translator receives an IPv4 packet with DF=0 that would
> >>> result in an IPv6 packet that would exceed the IPv6 link MTU, it will
> >>> split the original packet into IPv6 fragments.
> >> 
> >> It *could* fragment the IPv4 packet and send it in two unfragmented
> >> IPv6 packets.
> >> 
> >>> I cannot support your draft until it discusses or provides solutions
> >> for
> >>> the above considerations.
> >> 
> >> I'm in a similar case with respect to protocols above IPv6 (OSPF and
> >> NFS/UDP come quickly to mind) that depend on fragmentation to deal with
> >> the issue. I think the Robustness Principle tells us that such
> >> applications SHOULD figure out how to live with PMTU, but it also tells
> >> us that we can't deprecate fragmentation unless all known instances
> >> that depend on it have defined practical work-arounds. I suspect that
> >> this would imply the re-creation of the fragmentation feature in an
> >> intermediate protocol,
> > 
> > That is essentially what SEAL does - it provides an intermediate-level
> > segmentation and reassembly capability that avoids the pitfalls of IP
> > fragmentation.
> > 
> >> which seems like a lot of work with little real gain.
> > 
> > It's not that bad, and IMHO worth it.
> > 
> > Thanks - Fred
> > [e-mail]
> > 
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Mark Andrews, ISC
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