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

[james woodyatt <jhw@xxxxxxxxxx>]

On Feb 16, 2017, at 13:25, otroan@xxxxxxxxxxxxx wrote:

On Feb 13, 2017, at 14:32, David Farmer <farmer@xxxxxxx> wrote:

I have concerns with the following text;

   IPv6 unicast routing is based on prefixes of any valid length up to
   128 [BCP198].  For example, [RFC6164] standardises 127 bit prefixes
   on inter-router point-to-point links. However, the Interface ID of
   all unicast addresses, except those that start with the binary value
   000, is required to be 64 bits long.  The rationale for the 64 bit
   boundary in IPv6 addresses can be found in [RFC7421]

The third sentence seems to limit exceptions to 64 bit IIDs to exclusively addresses that start with binary vale of 000.  There are at least two other exceptions from standards track RFCs, that should be more clear accounted for in this text. […]

[…]

The challenge is to find text that enforces the 64-bit boundary policy (ignoring the technical arguments for a moment), and at the same time ensures implementors do the right thing and make their code handle any prefix length. Of course these are interdependent and doing the latter makes it harder to enforce the first.

I propose the following:

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 recognized in IETF standards track documents.

Trying to help out here.

--james woodyatt <jhw@xxxxxxxxxx>