Bob,
On 2019-09-03 14:08, Bob Hinden wrote:
> Joe,
>
>> On Aug 30, 2019, at 4:36 PM, Joe Touch <[email protected]> wrote:
>>
>> Hi, all,
>>
>> I disagree with the changes indicated in this version.
>>
>> The new text is both incorrect does not IMO reflect WG consensus.
>>
>> It is simply false that "it WILL break" or "new protocols can't possibly
>> know whether fragmentation works" - you even cite studies where this works
>> the majority of the time (failing 37% for IPv6 DNS resolvers is succeeding
>> 63%). This is not the same as ICMP-based MTU discovery. Users absolutely can
>> test and know this.
>>
>> I repeat my previous suggestion with caps for emphasis- that, LIKE ALL
>> PROTOCOLS AND FEATURES IN THE INTERNET, IP fragmentation is not guaranteed
>> to work on any given path and should be confirmed before being relied upon.
>
> The relevant text in -16 is:
>
> 6.1. For Application and Protocol Developers
>
> Developers SHOULD NOT develop new protocols or applications that rely
> on IP fragmentation. When a new protocol or application is deployed
> in an environment that does not fully support IP fragmentation, it
> SHOULD operate correctly, either in its default configuration or in a
> specified alternative configuration.
>
> While there may be controlled environments where IP fragmentation
> works reliably, this is a deployment issue and can not be known to
> someone developing a new protocol or application. It is not
> recommended that new protocols or applications be developed that rely
> on IP fragmentation. Protocols and applications that rely on IP
> fragmentation will fail to work on the Internet.
>
> The text in the first paragraph is unchanged in this version of the draft and
> has been there for awhile. The recommendation is still SHOULD NOT. This
> does allow other usage if there is a good reason to do so.
>
> The new second paragraph (written to resolve the DISCUSS comment) attempts to
> discuss the the controlled environment case. It clearly states it is a
> recommendation (along the lines of the SHOULD NOT) in the first paragraph and
> explains why.
It drops the idea that this is allowed - and is factually incorrect.
First, this absolutely can be known to deployers. This is not like
silent ICMP too-big drops where the cause of the drop cannot be known.
Second, it's already widely deployed to deal with IP-IP tunnels.
> Note, personally I think, citing your case of failing 37% of the time, is
> consistent with "will fail to work on the Internet".
Failing 37% of the endpoints is not the same as failing 37% of the time.
And no, neither one is consistent with "will fail on the Internet". If
you think 37% = will fail, then I'll open a personal casino for you with
those odds for you to win...
> Also, isn't this the reason why this draft exists, that is fragmentation is
> fragile.
There are differences of opinion even within the WG as to why this draft
exists. I would believe the authors believe as you state, but others of
us believe that "implementations are buggy" is more the take-home. The
WG and IETF last calls tried to strike a balance that this change
undoes.
This is not respecting the view of the WG or IETF.
Joe
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