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".