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List:       mpls
Subject:    Re: [mpls] Available IP version numbers.
From:       Kireeti Kompella <kireeti.ietf () gmail ! com>
Date:       2021-10-06 22:00:48
Message-ID: FA1AB086-4C72-4D9A-A320-0F2D339A588E () gmail ! com
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I'm with you, Sergey.  My answer is, we do not need to take anything (more) from the \
IP numbering space.

There is a complete non-functional hack in some MPLS implementations look at the \
first nibble after the label stack to "determine" whether the packet is IP, and if \
so, load balance on the (hopeful) IP fields found therein.  For this, they use the \
values 0x4 and 0x6 for IPv4 and IPv6 respectively.

We need to acknowledge the existence of this hack in the network, accommodate it, \
limit it, offer a new way forward, and thereby terminate this pseudo-relation between \
the IP version number space and the first nibble.  All set out in a draft a few of us \
are writing.

The piece of IP numbering that's already taken — using 0x4 and 0x6 — well, not \
much one can do at this point, unless we're willing to declare those implementations \
"non grata".

> K

> On Apr 19, 2021, at 11:53, ietf@sergey.dev wrote:
> 
> Hi Loa,
> In an adjacent thread ("mpls open dt & the first nibble discussion") I raised a \
> question about why do we even expect to take something from IP numbering. Would \
> appreciate your feedback on this one. 
> 
> -----Original Message-----
> From: mpls <mpls-bounces@ietf.org> On Behalf Of Loa Andersson
> Sent: Saturday, April 17, 2021 1:13 AM
> To: mpls <mpls@ietf.org>
> Subject: [mpls] Available IP version numbers.
> 
> DT,
> 
> We had a discussion on how many IP version numbers are available. 
> 
> It should be remembered that in IANA "Reserved" really means "Reserved, do not \
> assign".  
> 0,1,5,7,8,9 and 15 are reserved. 
> 2,3,10,11,12,13 and 14 are unassigned
> 4 and 6 are assigned 
> 
> To make the reserved requires a standard track RFC. 
> 
> So we 7 IP version numbers available, that is a sufficient low number to make me \
> nervous, if I owned the registry.  
> I would nit count on having more IP version numbers assigned to "us", especially \
> since we already have an agreement (PWE3), accepting to get two numbers and \
> committing to not use more.  
> /Loa
> 
> Sent from my iPhone
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