Re: Subject: Confirming consensus on adopting draft-carpenter-6man-why64

[Mark ZZZ Smith <[e-mail]>]

----- Original Message -----
> From: RJ Atkinson <[e-mail]>
> To: [e-mail]
> Cc: 
> Sent: Friday, 14 March 2014 2:49 AM
> Subject: Re: Subject: Confirming consensus on adopting draft-carpenter-6man-why64
> 
> On Thursday, March 13th 2014, at 09:15:25 -0500, David Farmer wrote:
>>  While prefix lengths between /65 and /126 are currently 
>>  operationally invalid, not currently specified, 
>>  they are architecturally valid. 
> 
> I completely disagree.  
> 
> That NEVER has been true for unicast addresses, and is an
> example of confusion rather than a fact.  
> 
> As some here will recall, I've been involved with IPv6 even before 
> it was called IPv6.  I also led the team with the world's first IPv6 
> packet working on the wire (we made a good guess about the decision 
> and had it working the week before) in our open-source 4.4 BSD 
> implementation.  So I've been involved with IPv6 for a couple of 
> decades now.
> 
> ONLY the unicast *routing-prefix* is VLSM, and that does NOT 
> include the fixed-length 64-bit IID.  
> 
> The IID is just an IID and has NEVER been VLSM.   Prefix lengths 
> longer than /64 NEVER have been valid, EXCEPTING the relatively recent 
> special-case for point-to-point links.

So what about ::1/128? What is the history of loopback being /128 rather than /64?

(And I really think it would have been better to be at least a /64 -

https://tools.ietf.org/html/draft-smith-v6ops-larger-ipv6-loopback-prefix-04)


>  This was added ONLY to resolve 
> an operational-security bug in certain deployed routers' IPv6 
> point-to-point code.
> 
>>  So,it needs to be reinforce that VLSM 
> 
> 
> ONLY true for the routing-prefix, not for the whole 128-bit object.
> 
>>  and a variable a length IID are fundamental to the IPv6 architecture, 
> 
> 
> This has NEVER been true.
> 
>>  and all IPv6 stacks must be able to deal with these prefix lengths 
>>  if/when they are specified as operationally valid.  If this weren't 
>>  the case then it would have been operationally impossible to implement 
>>  RFC6164 without major stack rewrites.
> 
> I completely disagree, both with your desires and with your 
> mis-representation of what happened historically.
> 
> At least some major stack rewrites occurred.  Multiple router 
> implementations that I'm aware of had to be quickly updated,
> and their operators had to deploy new images quickly also.
> 
> Multiple currently deployed router implementations treat the /126 prefix 
> VERY MUCH as a "special case" -- and added that code after the bug in 
> one router's point-to-point implementation became an operational problem.
> 
> Instead, this document needs to be very clear that IIDs are
> fixed length (both architecturally and for engineering), 
> always have been fixed length, and that IIDs are NOT VLSM.
> 
> Yours,
> 
> Ran Atkinson
> 
> 
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