Joe,

Your "Two Truths" are in line with the recommendations in Section 7 of 
draft-bonica-intarea-frag-fragile-01. The draft recommends that upper-layer 
protocols avoid doing things that cause fragmentation. It does not recommend 
the deprecation of fragmentation.

                                                                                
   Ron

.
> -----Original Message-----
> From: Joe Touch [mailto:to...@strayalpha.com]
> Sent: Tuesday, March 6, 2018 9:57 PM
> To: Ole Troan <otr...@employees.org>
> Cc: Tom Herbert <t...@herbertland.com>; Ron Bonica
> <rbon...@juniper.net>; int-area@ietf.org
> Subject: Re: [Int-area] draft-bonica-intarea-frag-fragile-01
> 
> 
> 
> > On Mar 6, 2018, at 11:16 AM, Ole Troan <otr...@employees.org> wrote:
> >
> > Joe,
> >
> >> Agreed but note that draft tunnels will update that RFC in some important
> ways.
> >
> > With other concerns than those raised in e.g. 4459 and 7597?
> 
> draft-tunnels corrects an error in 4459 that deals with the details, not the
> overall recommendation (AFAIR, at least).
> 
> > Unfortunately there are cases where there are no other choice than to do
> fragmentation/reassembly on tunnel endpoints, but still the
> recommendation holds.
> > It is so problematic, that it is strongly recommended to engineer the
> network to avoid that happening.
> 
> IMO, there are two truths:
> 
> 1) use of IP fragmentation SHOULD be avoided where possible, largely
> because it has reliability issues (ICMP blocking, NATs won’t tunnel frags and
> fail to [as required if they act on transport info] reassemble, etc.)
> 
> 2) support for IP fragmentation MUST remain required, as MUST (IMO) NAT
> reassembly before transport rewriting
> 
> Yeah, I know a lot of devices fail the MUSTs in #2, but the requirements
> ought to set the goal, not describe the (sorry) current state.
> 
> #2 has to persist until we deprecate IP-in-IP tunneling (including tunnel-
> mode IPsec), as well as any IP-in-X*-in-IP for zero or more intermediate
> layers X where no layer supports fragmentation and reassembly
> 
> I’ve been working to fix the need for IP frag by developing support for that 
> in
> UDP, but it doesn’t mean we should be ready to outlaw it.
> 
> I’m not sure what this doc does to add to this scene, though - it might be
> useful if the authors could explain how it affects 1 and 2 above and what else
> it adds in a *brief* post.
> 
> Joe
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