Re: Last Call: <draft-ietf-6man-rfc4291bis-07.txt> (IP Version 6 Addressing Architecture) to Internet Standard

[Xing Li <[e-mail]>]

Pierre Pfister ??:
> Hello all,
>
>   
>> Proposal:
>>  IPv6 unicast routing is based on prefixes of any valid length up to
>> 128 bits [BCP198]. However, as explained in [RFC7421], the Interface ID
>>  of unicast addresses is generally required to be 64 bits in length, with
>>  exceptions only provided in special cases where expressly recognised
>>  in IETF standards track documents.
>>
>>     
>
> The only place in IPv6 standards where the 64 boundary is mandated is on the 2000::/3 rule.
> There is not a single implementation or deployment of that rule. There is no instance where 
> trying to configure a prefix of length different than 64 will work when the prefix is within 2000::/3, and fail when it is not.
> That is a sufficient reason to not include this rule as part of the standard track.
>
> Nevertheless, SLAAC over Ethernet links indeed requires prefix length of 64.
> As documented in the RFC7421, there are a few examples of protocols which require 64 bits long interface identifiers.
>
> SLAAC is not the only way to configure IPv6 hosts though.
> Manual configuration, automated configuration, and DHCP are all IETF approved ways of configuring IPv6 hosts. 
> They all work with prefixes of various lengths. 
> Does 'special cases' in the proposed text covers manual/automated configuration or DHCP ? If so, it is far from being clear.
>
> You obviously should use /64s if you want SLAAC to work, as well as other protocols which are documented in RFC7421,
> but /64 is not the rule, it is an architectural consideration that you have to take into account when you design your network depending on the protocols that you want to run there.
>
> Therefore, as far as this discussion is concerned, there is no reason to mandate 64 bits boundaries as part of the IPv6 specification.
>   

+1, xing

> - Pierre
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [e-mail]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
>
>