Re: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile

"Templin (US), Fred L" <Fred.L.Templin@boeing.com> Fri, 06 September 2019 15:47 UTC

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From: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>
To: Joe Touch <touch@strayalpha.com>, Ole Troan <otroan@employees.org>
CC: Ron Bonica <rbonica=40juniper.net@dmarc.ietf.org>, "int-area@ietf.org" <int-area@ietf.org>, IESG <iesg@ietf.org>, Joel Halpern <joel.halpern@ericsson.com>, "draft-ietf-intarea-frag-fragile@ietf.org" <draft-ietf-intarea-frag-fragile@ietf.org>, Suresh Krishnan <suresh@kaloom.com>, "intarea-chairs@ietf.org" <intarea-chairs@ietf.org>
Thread-Topic: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile
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Date: Fri, 6 Sep 2019 15:47:16 +0000
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Subject: Re: [Int-area] Discussion about Section 6.1 in draft-ietf-intarea-frag-fragile
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Joe/Ole,

> >>> And of course encapsulation can also exacerbate the problem
> >>> by increasing packet size.

All this means is that the fragmentation layer needs to take into account the
size of the outer encapsulation layers that will be added and make sure its
fragments do not exceed 1280 bytes *after* encapsulation. So, e.g., if the
encapsulation layer adds an IPv6 header and a UDP header the fragmentation
layer should not produce fragments larger than 1280 - 40 - 8 = 1232. If the
fragmentation layer does not know the size of the outer encapsulations to
be added, it can overestimate and set a safe smaller value (e.g., 1024).

Fred