Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)

Fernando Gont <fgont@si6networks.com> Tue, 03 September 2019 15:57 UTC

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To: Tom Herbert <tom@herbertland.com>
Cc: "Templin, Fred L" <Fred.L.Templin@boeing.com>, Joe Touch <touch@strayalpha.com>, Alissa Cooper <alissa@cooperw.in>, Joel Halpern <joel.halpern@ericsson.com>, "draft-ietf-intarea-frag-fragile@ietf.org" <draft-ietf-intarea-frag-fragile@ietf.org>, "int-area@ietf.org" <int-area@ietf.org>, The IESG <iesg@ietf.org>, "intarea-chairs@ietf.org" <intarea-chairs@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Subject: Re: [Int-area] Alissa Cooper's No Objection on draft-ietf-intarea-frag-fragile-16: (with COMMENT)
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On 3/9/19 18:39, Tom Herbert wrote:
> 
> 
> On Tue, Sep 3, 2019, 8:31 AM Fernando Gont <fgont@si6networks.com
> <mailto:fgont@si6networks.com>> wrote:
> 
>     On 3/9/19 17:33, Templin (US), Fred L wrote:
>     > Why was this section taken out:
>     > 
>     >> 1.1.  IP-in-IP Tunnels
>     >>     
>     >>    This document acknowledges that in some cases, packets must
>     be     
>     >>    fragmented within IP-in-IP tunnels
>     [I-D.ietf-intarea-tunnels].     
>     >>    Therefore, this document makes no additional recommendations     
>     >>    regarding IP-in-IP tunnels.
>     >
>     > Tunnels always inflate the size of packets to the point that they
>     may exceed
>     > the path MTU even if the original packet is no larger than the
>     path MTU. And,
>     > for IPv6 the only guarantee is 1280. Therefore, in order to
>     robustly support
>     > the minimum IPv6 MTU tunnels MUST employ fragmentation.
> 
>     Isn't that an oxymoron? If fragmentation is fragile, if you need
>     something robust, you need to rely on something else....
> 
> 
> Not really, to say fragmentation is fragile is a subjective statement,
> not a quantifiable fact.

RFC7872. IIRC, Geoff did his own independent measurements.



> As discussed on the list, fragmentation is
> productively in use in many networks that employ tunneling. In those
> cases fragmentation is not fragile and so there's nothing to fix.

The measurements I've seen about fragmentation on the big-I internet
seem to indicate that it is fragile. Yes, you can always build your own
private network where it is not.


-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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