Re: [dhcwg] dhc WG review of draft-ietf-geopriv-lis-discovery-05

On Wed, Jan 28, 2009 at 10:58:23PM -0600, Thomson, Martin wrote:
> Excuse me, I must been having another one of my "thick" moments.

No, DHCPv4 is just that hard.  The sensation you are perceiving is
perfectly normal, and is often accompanied by nausea and in extreme
cases vomiting.  Do not operate any heavy machinery.

I have found it helps sometimes to put it away and come back to it
after the caffeine has reached full potency.

And don't go swimming for at least an hour.

> As I understand, RFC 3396 concatenation occurs at a lower layer - a client
> that supports RFC 3396 can present arbitrarily large values to its users.
> If there is indeed no established convention for concatenation of suboptions,
> then it might be reasonable to assume concatenation.

I think older ISC DHCP software (3.0-) concatenates duplicates in sub
option spaces.  The newer software (3.1+?) that was updated for v6 and
VSIO only does the concat thing on DHCPv4 root options.  All other
'option spaces' (we call them) default to not having the flag enabled
and so do not perform concats (on the basis that the behaviour was not
described in the relevant RFC for those options).

So from my point of view, you can specify which behaviour you want in
the draft.

But I don't actually know what other software does for these spaces.

> If you assume concatenation is the method for dealing with repeated
> sub-options, then your suggestion works for me.  Without that assumption,
> I missed what you were getting at.  (For my benefit, I'm not aware of a
> use of sub-options post 3396, is there no use of concatenation with any of
> these?)

If there is, I need to be educated too!  The only space we currently
support where multiple options concatenate is the root DHCPv4 options.

All other v4 encapsulated and all v6 "spaces" are non-concat.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins