> On Mar 7, 2018, at 7:39 AM, Ron Bonica <rbon...@juniper.net> wrote:
> 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.

Understood, but without #2 being included and explicitly co-reinforced there is 
an implication to router designers that I would hope can be avoided.  


>     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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