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RE: Usable extension headers [Re: New Version Notification for draft-voyer-6man-extension-header-insertion-08.txt]

"Manfredi (US), Albert E" <albert.e.manfredi@boeing.com> Thu, 28 November 2019 03:34 UTC

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From: "Manfredi (US), Albert E" <albert.e.manfredi@boeing.com>
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
CC: 6MAN <6man@ietf.org>
Subject: RE: Usable extension headers [Re: New Version Notification for draft-voyer-6man-extension-header-insertion-08.txt]
Thread-Topic: Usable extension headers [Re: New Version Notification for draft-voyer-6man-extension-header-insertion-08.txt]
Thread-Index: AQHVpZVteudV/M4cEUyQO3aBU7F/dKef6ScQ
Date: Thu, 28 Nov 2019 03:34:02 +0000
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-----Original Message-----
From: ipv6 <ipv6-bounces@ietf.org> On Behalf Of Brian E Carpenter

> As I experienced years ago when my Ph.D. student was making real-world experiments with SHIM6, and as RFC7872 reported too, it's an observed fact that the Internet isn't transparent to packets with extension headers, not even to currently standardised ones. The same appears to have been true for IPv4 Options for at least 25 years. So, to be honest, I have no idea how to change that for the open Internet. We seem to be stuck with a lowest common denominator network layer.

Isn't the problem that routers must mostly not mess with these extension headers? Even hop-by-hop headers can be ignored by routers (unless specifically configured not to ignore)?

So, you have a layer 3 extension option, but the boxes which do the heavy lifting at layer 3 must never mess with. On the other hand, end systems, which can play with IP extension headers, have virtually no knowledge of the network topology details.

Router manufacturers seem to prefer the simplest possible routing mechanization. Hosts don't typically have a clue how best to use the knob. My impression has always been that people are as discouraged to use layer 3 extension headers, as they are to use packet fragmentation. One of those things you want to avoid, unless you're a glutton for punishment? Not so?

Happy Thanksgiving, for those to whom this applies.

Bert

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