Re: [v6ops] I-D Action: draft-ietf-v6ops-unique-ipv6-prefix-per-host-07.txt

[David Farmer <[e-mail]>]

On Fri, Aug 4, 2017 at 12:49 PM, DY Kim <[e-mail]> wrote:

> in line...
>
> —-
> DY
>
>
> > On 4 Aug 2017, at 22:58, David Farmer <[e-mail]> wrote:
> >
> > I don't see how whole subnet or prefix assigned to just a single host is
> incompatible with with RFC4291 or RFC4291bis in any way.
>
> Subnet, to my understanding, is a shared network comprising of a
> collection of hosts managed (bordered) by one or more routers. A subnet
> prefix is one assigned to the whole subnet wherein all hosts share the same
> prefix.
>
> When each host in such a share network (subnet) is assigned a unique
> prefix (and hosts don’t share the same prefix), that prefix is not a subnet
> prefix and should be name differently, say, ‘host prefix’ or ‘node prefix’.
>
> RFC4291bis defines (comments) only the subnet prefix. The draft of this
> thread title deals with a prefix type not defined (commented) in the
> RFC4291bis (to-be-)standard. In that, the draft under discussion in this
> thread could be said ‘not in compliance with’ the RFC4291bis.
>
> This is my logic. Odd yet?
>

Well, RFC4291 is quite clear there can be more than one subnet per link,
there might be practical limits on how may subnet you can have on a link
but there is no theoretical limit that I'm aware of.  Furthermore, Wifi or
other link technology will probably reach congestion collapse before you
reach such limits on a modern router.  While it is common for a router to
have an address in the subnet this is not required, the host can just use
the router's link-local address, and if the router is learned form RAs
using the link-local address is the normal mode of operation anyway. Also,
it's common for subnets to have more than one host again nothing requires
this either.

So, this isn't what most people will think of when they read RFC4291, but
your only running afoul of people's assumptions not the specification
itself. Therefore, bring this up might be a good idea for RFC4291bis,
principle of least astonishment and all, but not absolutely necessary.

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