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Re: RFC4890 question (was: RE: New Version Notification for draft-jiang-v6ops-incremental-cgn)

Mohacsi Janos <mohacsi@niif.hu> Tue, 09 June 2009 08:18 UTC

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Date: Tue, 09 Jun 2009 10:12:22 +0200
From: Mohacsi Janos <mohacsi@niif.hu>
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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
cc: Elwyn Davies <elwynd@dial.pipex.com>, JiangSheng 66104 <shengjiang@huawei.com>, Seiichi Kawamura <kawamucho@mesh.ad.jp>, Gert Doering <gert@space.net>, "Fleischman, Eric" <eric.fleischman@boeing.com>, Re'mi Despre's <remi.despres@free.fr>, v6ops@ops.ietf.org, guoseu@huawei.com, "Russert, Steven W" <steven.w.russert@boeing.com>, Brian E Carpenter <brian.e.carpenter@gmail.com>
Subject: Re: RFC4890 question (was: RE: New Version Notification for draft-jiang-v6ops-incremental-cgn)
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Dear Fred,
 	I try to figure out from my notes what was the reason of the text. 
Best Regards,

Janos Mohacsi
Network Engineer, Research Associate, Head of Network Planning and Projects
NIIF/HUNGARNET, HUNGARY
Key 70EF9882: DEC2 C685 1ED4 C95A 145F  4300 6F64 7B00 70EF 9882

On Mon, 8 Jun 2009, Templin, Fred L wrote:

> I guess I have to ask again. Can the RFC4890 authors please
> comment on the RFC4890, Section A.2 text questions asked in
> my previous message (below)?
>
> Fred
> fred.l.templin@boeing.com
>
>> -----Original Message-----
>> From: Templin, Fred L
>> Sent: Thursday, June 04, 2009 8:44 AM
>> To: Mohacsi Janos; Brian E Carpenter
>> Cc: JiangSheng 66104; Seiichi Kawamura; Gert Doering; Fleischman,
> Eric; Re'mi Despre's;
>> v6ops@ops.ietf.org; guoseu@huawei.com; Russert, Steven W
>> Subject: RE: New Version Notification for
> draft-jiang-v6ops-incremental-cgn
>>
>>>> Do you think the draft needs to do any more than recommending to
>> follow
>>>> the recommendations in 4890? It seems as if that should be
>> sufficient.
>>>
>>> This should be enough.
>>
>> Regarding the 4890, there is advice in that document that I
>> would like to understand better. In Appendix A.2, it says:
>>
>>    "If a network chooses to generate packets that are no larger than
> the
>>    Guaranteed Minimum MTU (1280 octets) and the site's links to the
>>    wider Internet have corresponding MTUs, Packet Too Big messages
>>    should not be expected at the firewall and could be dropped if they
>>    arrive."
>>
>> But, that would seem to be in conflict with the text of
>> Section 5 of RFC2460, where the reader is informed that
>> the network can return PTB messages reporting MTU values
>> smaller than 1280 if a protocol translator is in the path.
>> The host should then react to these PTBs by inserting a
>> fragment header with (MF=0; Offset=0) in subsequent packets.
>> With the (RFC4890, Appendix A.2) text however, this behavior
>> is suppressed.
>>
>> Where did the RFC4890 text come from? And, why is it there?
>>
>> Thanks - Fred
>> fred.l.templin@boeing.com
>
>
>

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