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Re: Non-Last Small IPv6 Fragments

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 14 January 2019 03:17 UTC

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Subject: Re: Non-Last Small IPv6 Fragments
To: Fernando Gont <fgont@si6networks.com>, Tom Herbert <tom@herbertland.com>
Cc: IPv6 List <ipv6@ietf.org>, Bob Hinden <bob.hinden@gmail.com>
References: <CAOSSMjV0Vazum5OKztWhAhJrjLjXc5w5YGxdzHgbzi7YVSk7rg@mail.gmail.com> <CAN-Dau1HwG5RndacpSA+si+zKuTdpSvA=QA1A11A==rMNe=4+w@mail.gmail.com> <CALx6S35KNhV2gFp9OdU+M1zy5WUuEAEvXkDXNDWWxi7uQ4e_cw@mail.gmail.com> <CAN-Dau0rTdiiF2SjByxcMG6nhPCEjUH2pYBCOeK_FSGJ_ucDQw@mail.gmail.com> <CALx6S34AyV9OpvnjQhQc56n5vfeVgU5Zd3kheP0g+XvsMbBV9g@mail.gmail.com> <1b2e318e-1a9f-bb5d-75a5-04444c42ef20@si6networks.com> <CALx6S37TJr++fC=pVoeS=mrO1fHc4gL_Wtu-XkVTswzs2XxXCA@mail.gmail.com> <CALx6S36V7vrVyoTP0G6+S5XeFNB3KWS5UaNnVi20xogRERdCfg@mail.gmail.com> <973A1649-55F6-4D97-A97F-CEF555A4D397@employees.org> <CALx6S34YbBe8xBod3VsWVO33TpZcdxh2uV1vaO8Z_NKnVXp66g@mail.gmail.com> <A3C3F9C0-0A07-41AF-9671-B9E486CB8246@employees.org> <AEA47E27-C0CB-4ABE-8ADE-51E9D599EF8F@gmail.com> <6aae7888-46a4-342d-1d76-10f8b50cebc4@gmail.com> <CALx6S35QKOqn_Ywh9yzm1JDA8Xnp7fLPPmXUvomvz_xOZP8bfg@mail.gmail.com> <146dbb4f-bebb-cce4-f0f8-f965a951dc47@gmail.com> <167742b9-41c7-26c4-716d-139d7780d6af@si6networks.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Date: Mon, 14 Jan 2019 16:17:34 +1300
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On 2019-01-14 15:48, Fernando Gont wrote:
> On 13/1/19 18:40, Brian E Carpenter wrote:
>> On 2019-01-14 08:48, Tom Herbert wrote:
>>> On Sun, Jan 13, 2019 at 11:25 AM Brian E Carpenter
>>> <brian.e.carpenter@gmail.com> wrote:
>>>>
>>>> On 2019-01-14 07:54, Bob Hinden wrote:
>>>>> Unleveling a bit.
>>>>>
>>>>> I think the w.g. should be very cautious about making protocol changes based on what appears to be a fragmentation resource management problem in an implementation.
>>>>
>>>> I agree. However, I wonder if we need to clarify that there is no rule that non-last fragments must be at least 1280. It seems that the Linux patch assumed that there is
>>>> such a rule.
>>> Brian,
>>>
>>> Yes, but then what are the rules? 
>>
>> Well, I'm an advocate of one step at a time.
>>
>> Step 1: As an addendum to RFC8200, state that there is no rule that non-last fragments must be at least 1280.
> 
> Isn't that implicit?

On the basis that anything that is not forbidden is allowed, yes, but apparently this wasn't apparent to the Linux devs involved. We don't really have a lightweight way of handling cases like this, since cost of producing an RFC is clearly too much.

   Brian

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