Re: [v6ops] M/O flags and PD

[Tore Anderson <[e-mail]>]

* Brian E Carpenter

> On 31/10/2015 04:24, Sander Steffann wrote:
> 
> > I always understood this bit from RFC 3633 to mean that any host
> > configuration flags (such as M/O) are not relevant to DHCPv6-PD:
> > "Note that this use of DHCP is not bound to the assignment of IP
> > addresses or other configuration information to hosts".	
> 
> The phrase "is not bound to" is rather unclear, don't you think? It
> neither says nor implies that routers are thereby exempt from issuing
> correct RAs.

Agreed.

Also, note that RFC 3633 did *not* update RFCs 2461/2462, which at the
time defined the meaning of the O/M flags to be essentially the same as
what RFC 4861 defines them to be today.

> Even if you accept that, in the case that you *don't* know that such
> information is available, you physically cannot set the M or O flag.
> So in the real world, a node that is interested in IA_PD had better
> go fishing for it, whatever the MO bits say. So I retract all the if
> statements in the pseudocode that I sent. The only robust
> implementation is one that always looks for DHCPv6 information.

That might indeed be the case - but it's not what the standards are
currently telling the implementers to do. Furthermore, accepting this
would mean that the M/O flags are essentially pointless. In that case,
deprecating the flags would be the logical thing to do.

(You explicitly called out IA_PD, but as your argument applies equally
well to any other DHCPv6 option I'm going to assume you meant IA_PD
just as an example.)

Tore