[Ecn-sane] cautionary tcp tale

[David P. Reed]

I'm of a mind to suggest an RFC specifically reiterating that non-endpoints MUST never modify the content part of any IP datagrams, ever, with the exception of the TCP and UDP extended routing header (the ports), and that solely for the purpose of implementing NAT as defined in the NAT standard.

I think vint Cerf and I would be happy to be co-authors, maybe along with Dave Clark, Noel Chiappa, and a crew of original Internet Protocol designers.

I had thought this was a well-understood invariant, core to the design of the entire Internet.

Part of the reason, but certainly not all of it, was that we all intended that the content within the IP datagram contents would be treated as sacrosanct, as if encrypted by a key unknown to the network.

We could not require end-to-end encryption because of ITAR rules at the time. But it is absolutely clear that NOTHING in the network transport system was expected to attempt to understand or to modify those bits until they reached the destination, unchanged.

It wasn't just a "good idea", it was a design requirement.

On Tuesday, August 13, 2019 12:39pm, "Michael Richardson" <mcr at sandelman.ca> said:

> Thanks.
> Also a good story as to why middle boxes should stay away from mangling
> packets without an audit trail.
> 
> 
> 
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