Re: WG ACTION: 1 week continued discussion [LL70] DNAv4 normative or informative?

Bernard,

The answer to your questions is that you are correct in each case.

The newest text you propose below is an improvement on my last proposal =
for the reasons you give - and the DNAv4 reference is now clearly =
non-normative.

This now looks good to me.

Philip

----- Original Message -----=20
From: "Bernard Aboba" <[email protected]>
To: "Philip Nye" <[email protected]>
Cc: <[email protected]>
Sent: Tuesday, June 01, 2004 2:03 PM
Subject: Re: WG ACTION: 1 week continued discussion [LL70] DNAv4 =
normative or informative?


> > I propose rewording your latest text as below. I hope that in =
editing your text I have made this
> > section clearer. I have removed most use of "configured" and all use =
of
> > "valid". I have added a little to make clear that these are =
transitional
> > cases only. I have introduced and defined the term "operable" and =
made
> > plain that there is no easy rule to determine operability. There is =
no
> > need to define "valid" or anything extra in the terminology section =
at
> > all.
>=20
> The change from "valid" to "operable" is helpful, I think.  Comments =
below.
>=20
> >    For these reasons, a host
> >    SHOULD NOT have both a routable address and an IPv4 Link-Local =
address
> >    configured on the same interface.
>=20
> This advice no longer applies if one of those addresses is not =
"operable",
> right?
>=20
> >    When an operable routable address is
> >    available on an interface, the host SHOULD NOT also assign an =
IPv4
> >    Link-Local address on that interface. However, during transition =
(in
> >    either direction) between using routable and IPv4 Link-Local =
addresses
> >    both MAY be in use at once subject to these rules.
>=20
> Should it say "these rules:"?  If so, perhaps the rules should be
> bulleted.
>=20
> >    The assignment of an IPv4 Link-Local address on an interface is =
based
> >    solely on the state of the interface, and is independent of any =
other
> >    protocols such as DHCP.  A host MUST NOT alter its behavior and =
use of
> >    other protocols such as DHCP because the host has assigned an =
IPv4
> >    Link-Local address to an interface.
> >
> >    The term "operable address" is used to mean an address which =
works
> >    effectively for communication in the current network context (see =
below).
> >    If a host finds that an interface that was previously configured =
with
> >    an IPv4 Link- Local address now has an operable routable address
> >    available the host MUST use the routable address when initiating =
new
> >    communications, and MUST cease advertising the availability of =
the
> >    IPv4 Link-Local address through whatever mechanisms that address =
had
> >    been made known to others.  The host SHOULD continue to use the =
IPv4
> >    Link-Local address for communications already underway, and MAY
> >    continue to accept new communications addressed to the IPv4 =
Link-Local
> >    address. Ways in which an operable routable address might become
> >    available on an interface include:
> >
> >    * Manual configuration
> >    * Address assignment through DHCP
> >    * Roaming of the host to a network on which an existing address
> >       becomes operable.
>=20
> Does this have the same meaning as "a previously assigned address =
becomes
> operable"?
>=20
> Here's a proposed version, with changes:
>=20
> 1.9.  When to configure a Link-Local IPv4 address
>=20
>    Having addresses of multiple different scopes assigned to an
>    interface, with no adequate way to determine in what circumstances
>    each address should be used, leads to complexity for applications =
and
>    confusion for users.  A host with an address on a link can =
communicate
>    with all other devices on that link, whether those devices use =
Link-
>    Local addresses, or routable addresses.  For these reasons, a host
>    SHOULD NOT have both an operable routable address and an IPv4
>    Link-Local address configured on the same interface. The term
>    "operable address" is used to mean an address which works
>    effectively for communication in the current network context
>    (see below).  When a operable routable address is available
>    on an interface, the host SHOULD NOT also assign an IPv4
>    Link-Local address on that interface.  However, during the
>    transition (in either direction) between using routable and IPv4
>    Link-Local addresses both MAY be in use at once subject to these =
rules:
>=20
>    1. The assignment of an IPv4 Link-Local address on an interface is
>       based solely on the state of the interface, and is independent =
of
>       any other protocols such as DHCP.  A host MUST NOT alter its
>       behavior and use of other protocols such as DHCP because the =
host
>       has assigned an IPv4 Link-Local address to an interface.
>=20
>    2. If a host finds that an interface that was previously configured
>       with an IPv4 Link-Local address now has an operable routable
>       address available, the host MUST use the routable address when
>       initiating new communications, and MUST cease advertising the
>       availability of the IPv4 Link-Local address through whatever
>       mechanisms that address had been made known to others.  The host
>       SHOULD continue to use the IPv4 Link-Local address for
>       communications already underway, and MAY continue to accept new
>       communications addressed to the IPv4 Link-Local address. Ways in
>       which an operable routable address might become
>       available on an interface include:
>=20
>          * Manual configuration
>          * Address assignment through DHCP
>          * Roaming of the host to a network on which a previously
>            assigned address becomes operable.
>=20
>    3. If a host finds that an interface no longer has an operable =
routable
>       address available, the host MAY identify a usable IPv4 =
Link-Local
>       address (as described in section 2) and assign that address to =
the
>       interface. Ways in which an operable routable address might =
cease to
>       be available on an interface include:
>=20
>          * Removal of the address from the interface through manual
>            configuration
>          * Expiration of the lease on the address assigned through =
DHCP
>          * Roaming of the host to a new network on which the address =
is no
>            longer operable.
>=20
>    The determination by the system of whether an address is "operable" =
is
>    not clear cut and many changes in the system context (e.g.
>    router changes) may affect the operability of an address. In
>    particular roaming of a host from one network to another is likely =
-
>    but not certain - to change the operability of a configured address =
but
>    detecting such a move is not always trivial.
>=20
>    "Detection of Network Attachment (DNA) in IPv4" [DNAv4]
>    provides further discussion of address assignment and operability
>    determination.
>