Re: new issue: [LL36] Combine and rework section 1.7 and 2.11 to be clearer

Philip - I think I surrounded the text that describes using multiple
addresses on an interface with conditionals (SHOULD, MAY) so that a stack
that only allows a single address on an interface can still be compliant
with the spec.  If you don't agree, can you point out the text that requires
multiple addresses on an interface and/or suggest new text?

- Ralph

At 09:40 AM 12/18/2003 +0000, Philip Nye wrote:
>Ralph's approach seems reasonable and I think improves the draft. However, 
>I am concerned that as written it does not allow operation with stacks 
>which only allow a single address per interface.
>
>Philip
>
>----- Original Message -----
>From: "Ralph Droms" <[email protected]>
>To: "Erik Guttman" <[email protected]>
>Cc: <[email protected]>
>Sent: Tuesday, December 16, 2003 5:00 PM
>Subject: Re: new issue: [LL36] Combine and rework section 1.7 and 2.11 to 
>be clearer
>
>
> > In response to this issue, I suggest deleting subsections 1.7 and 2.11, 
> and
> > inserting the following text as the last subsection of section 1 (in
> > particular, to come after subsection 1.9. "Communication with Routable
> > Addresses"):
> >
> >
> > 1.x When to configure a Link-Local IPv4 address on an interface
> >
> >     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 configure on the same interface.
> >
> >     A routable address is any address that is:
> >
> >     * a unicast address
> >     * not a loopback address
> >     * not in the 169..2.54/32 subnet reserved for Link-Local IPv4
> >       addresses
> >
> >     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].
> >
> >     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 or RADIUS.  A host MUST NOT
> >     alter its behavior and use of other protocols such as DHCP and
> >     RADIUS because the host has assigned a Link-Local IPv4 address to
> >     an interface.
> >
> >     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.
> >
> >     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:
> >
> >     * Manual configuration
> >     * Address assignment through RADIUS or DHCP
> >     * Roaming of the host to a network on which a routable address
> >       assigned to the interface is valid
> >
> >     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:
> >
> >     * 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.
> >
> >     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".
> >
> >