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

I support the principle that DNAv4 should become informative rather than =
normative - espescially as recent discussions here have shown that the =
reachability test of DNAv4 is a guide rather than a final and decisive =
test of the useability of an address.

I do not support the resolution text as it stands for several reasons:

1. (editorial) an extra meaningless paragraph has appeared which is a =
combination of two others:

>    When an interface has a routable address configured 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.

2. (editorial) "When an interface has a routable address configured on =
an interface" needs to be changed. The paragraph should read:

   When a routable address is configured on an interface,
   the host SHOULD NOT also assign an IPv4 Link-Local address to that
   interface.

3. (substantive) as I have said in previous discussion, the term "valid" =
carries meaning that is lost when it is simply dropped as here. I would =
rather keep the term "valid" (or "working" or "useable") and leave its =
definition fuzzy if necessary. I don't believe the proposed text =
adequately resolves this issue.

    If a host finds that an interface that was previous[ly] configured
    with an IPv4 Link-Local address is now configured with a routable=20
    address, the host MUST use the routable address when initiating new=20
    communications...

I would interpret this text as a firm injunction preventing me from =
using IPv4LL on any interface which has a routable address however wrong =
and unuseable that address is. The only get out is weasle words about =
the meaning of "configured".

Philip


----- Original Message -----=20
From: "Erik Guttman" <[email protected]>
To: <[email protected]>
Sent: Tuesday, May 25, 2004 4:56 PM
Subject: WG ACTION: 1 week continued discussion [LL70] DNAv4 normative =
or informative?


> LL70
>=20
> This issue will remain open for comment until June 2, 2004.
> After that point, if no comments are received, the issue will be
> resolved by making DNAv4 normative and leaving the text as it =
currently
> stands.
>=20
> Bernard suggests the following resolution, which should allow DNAv4 to
> remain an informative reference.
>=20
> Was:
> 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 a valid routable address and a
>    Link-Local IPv4 address configured on the same interface.
>=20
>=20
>    A routable address is any address that is:
>=20
>    * a unicast address (see Section 1.2)
>    * not a loopback address
>    * not contained within the 169.254/16 prefix reserved for =
Link-Local
>       IPv4 addresses
>=20
>    A "valid routable address" is a routable address that passes the
>    reachability test described in section 2 of "Detection of Network
>    Attachment (DNA) in IPv4" [DNAv4].
>=20
>    The assignment and use of a Link-Local IPv4 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
>    a Link-Local IPv4 address to an interface.
>=20
>    When an interface has a valid routable address configured on an
>    interface, the host SHOULD NOT also assign a Link-Local IPv4 =
address
>    to that interface.
>=20
>    If a host finds that an interface that was previous configured with =
a
>    Link-Local IPv4 address is now configured with a valid routable
>    address, the host MUST always use the routable address when
>    initiating new communications, and MUST cease advertising the
>    availability of the Link-Local IPv4 address through whatever
>    mechanisms that address had been made known to others.  The host
>    SHOULD continue to use the Link-Local IPv4 address for =
communications
>    underway when the routable address was configured, and MAY continue
>    to accept new communications addressed to the Link-Local IPv4
>    address.  Ways in which a valid routable address might be =
configured
>    for the interface include:
>=20
>    * Manual configuration
>    * Address assignment through DHCP
>    * Roaming of the host to a network on which a routable address
>       assigned to the interface is valid
>=20
>    If a host finds that an interface that was previously configured =
with
>    a valid routable address no longer has a valid routable address, =
the
>    host MAY identify a usable Link-Local IPv4 address (as described in
>    section 2) and assign that address to the interface.  Ways in which =
a
>    valid routable address might no longer be assigned to 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 valid.
>=20
>    Further discussion of the issues in detection of transient failures
>    and the use of DHCP in response to network attachment failure is
>    provided in "Detection of Network Attachment (DNA) in IPv4". =
[DNAv4]
>=20
>=20
>=20
> Becomes:
>=20
> 1.9.  When to configure an IPv4 Link-Local 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 a routable address and an IPv4
>    Link-Local address configured on the same interface.
>=20
>    The assignment and use 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
>    When an interface has a routable address configured 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
>    When an interface has a routable address configured on an =
interface,
>    the host SHOULD NOT also assign an IPv4 Link-Local address to that
>    interface.
>=20
>    If a host finds that an interface that was previous configured with
>    an IPv4 Link-Local address is now configured with a routable =
address,
>    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 underway when the routable
>    address was configured, and MAY continue to accept new =
communications
>    addressed to the IPv4 Link-Local address.  Ways in which a routable
>    address might be configured for the interface include:
>=20
>    * Manual configuration
>    * Address assignment through DHCP
>   * Roaming of the host to a network on which the host has a
>         valid routable address
>=20
>    If a host finds that a routable address is no longer assigned to an
>    interface, 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 a routable address might no longer be assigned to 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 valid.
>=20
>    Further discussion of address assignment and the detection of =
network
>    attachment is provided in [DNAv4].
>=20
> Erik Guttman
> ZEROCONF WG Chair
>=20
>