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Re: [mpls] Available IP version numbers.

Stewart Bryant <stewart.bryant@gmail.com> Tue, 20 April 2021 14:28 UTC

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From: Stewart Bryant <stewart.bryant@gmail.com>
In-Reply-To: <001b01d73551$47ba6520$d72f2f60$@sergey.dev>
Date: Tue, 20 Apr 2021 15:28:13 +0100
Cc: Stewart Bryant <stewart.bryant@gmail.com>, Joel Halpern <jmh@joelhalpern.com>, Loa Andersson <loa.pi.nu@gmail.com>, mpls <mpls@ietf.org>
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Subject: Re: [mpls] Available IP version numbers.
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I agree.

This is about pragmatically addressing an architecture violation that goes back many years.

In many ways this is a good example an architectural breach which seems to be a quick pragmatic fix by the implementers causing years of future pain.

- Stewart



> On 19 Apr 2021, at 20:22, ietf@sergey.dev wrote:
> 
> Joel,
> I agree with that.
> 
> But my point it - it seems there's an implicit assumption that IP header follows an MPLS label stack, which may or may not be the case. First nibble is not a protocol identifier in a classical sense (except for LSR-guessing). 
> We can't rely on a nibble as a unique identifier by itself; so is there even a point in using anything besides 0x0 (to avoid LSR-guessing)? There might be, but it is not obvious in a current form of just taking a new number.
> And if we were to use a new number - it is not an IP version number (as long as we are not claiming that an IP header follows. Yes, 0x0 and 0x1 were reserved by IANA for rfc4928 usecase, but this is not, strictly speaking, a standard-defined paradigm).
> 
> --
> Sergey

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