Re: <draft-ietf-6man-rfc4291bis-09.txt>

[Bob Hinden <[e-mail]>]

Hi David,

> On Jul 3, 2017, at 1:22 PM, David Farmer <[e-mail]> wrote:
> 
> 
> 
> On Mon, Jul 3, 2017 at 12:36 PM, Bob Hinden <[e-mail]> wrote:
> Hi,
> 
> I published a new 6man w.g. version (-09) of the RFC4291bis draft.  See links below.
> 
> The summary of the changes are:
> 
>        o   Added text to the last paragraph in Section 2.1 to clarify
>            the differences on how subnets are hangled in IPv4 and IPv6,
>            includes a reference to RFC5942 "The IPv6 Subnet Model: The
>            Relationship between Links and Subnet Prefixes".
> 
> I was thinking about suggesting a reference to RFC5942 "The IPv6 Subnet Model", but I wasn't sure where to put it, I really like were you put it.

Good, thanks.

> 
> However, I still think the following paragraph is still too easily misunderstood to imply subnets must be /64 or 64 bits for both address generation and on-link determination.
> 
>    Interface Identifiers are 64 bit long except if the first three bits
>    of the address are 000, or when the addresses are manually
>    configured, or by exceptions defined in standards track documents.
>    The rationale for using 64 bit Interface Identifiers can be found in
> 
>    [RFC7421].  An example of a standards track exception is [RFC6164]
>    that standardises 127 bit prefixes on inter-router point-to-point
>    links.
> 
> 
> How about a note clarifying the intent of the this paragraph, something like this;
> 
>       Note: While the previous paragraph does imply 64 bit subnet prefixes
>       are typically assigned to most links. It does not imply anything
>       about what portion, if any, of a subnet is considered to be on-link,
>       see Section 2.1 for more discussion. However, Router Advertisements
>       [RFC4861] specifying 64 bit on-link prefixes are typically
>       configured on most links.

Now that the text you refer to is in Section 2.4.1. "Interface Identifiers”, it is about Interface Identifiers, very little is said about prefixes (except that IIDs are required to be unique on a prefix, but even that is about IIDs).  I don’t think it is implying anything one way or about on-link properties.  I think that is covered pretty well in the new paragraph in Section 2.1 "Addressing Model” that includes the link to RFC5942.

Thanks,
Bob



> 
> Thanks
> 
> --
> ===============================================
> David Farmer               Email:[e-mail]
> Networking & Telecommunication Services
> Office of Information Technology
> University of Minnesota
> 2218 University Ave SE        Phone: [phone]
> Minneapolis, MN 55414-3029   Cell: 612-812-9952
> ===============================================