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Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile

Ole Troan <otroan@employees.org> Thu, 02 August 2018 15:38 UTC

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From: Ole Troan <otroan@employees.org>
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Date: Thu, 02 Aug 2018 17:38:45 +0200
In-Reply-To: <1B04E207-08FA-400F-BBED-67379FEFD64E@strayalpha.com>
Cc: Tom Herbert <tom@herbertland.com>, int-area <int-area@ietf.org>, intarea-chairs@ietf.org
To: Joe Touch <touch@strayalpha.com>
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Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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Joe,

> I am not ignoring them; I’m claiming that they all have the same inherent deployment and implementation limitations.
> 
> Just because operators/vendors “want” to do otherwise does not make it possible.

There was IETF consensus behind those documents (A+P). 
In the _new_ IPv4 Internet architecture the IPv4 header looks like this:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2  3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |.    0x45      |Type of Service|          Total Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Identification        |Flags|      Fragment Offset    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Time to Live |      6|17     |         Header Checksum       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Source Address                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Destination Address                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Source Port           |     Destination Port          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

If the the ascii art comes through.

In contrast to NAT the address and port fields are not rewritten. Only used for forwarding.
The source port and destination port fields are shared between L3 and L4. With an out-of-band provisioning protocol informing the end system which ports are available for applications.

Ole

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