Subject: [mobile-ip] issue 94: unclear references to "addresses allowable in RH"

From: Jari Arkko <[email-masked]>
Date: Wed, 07 Aug 2002 13:18:00 +0300

Background: Text in Section 6.1.7 says:

    The care-of address MUST NOT be any IPv6 address which is prohibited
    for use within a Routing Header; thus multicast addresses, the
    unspecified address, loop-back address, and link-local addresses
    are excluded.  Binding Updates indicating any such excluded care-of
    address MUST be silently discarded.

and Section 9.4.4 says:

     -  Otherwise, if the Source IP Address of the packet containing
        the Binding Update, is legal for inclusion in a Routing Header,
        the routing header will be constructed using that IP address.
        Note that multicast addresses, link-local addresses, loopback
        addresses, IPv4 mapped addresses, and the unspecified address,
        MUST NOT be used within a Routing Header for the Binding
        Acknowledgement.

as well as

    Otherwise, if the Binding Update has a zero lifetime but the Source
    IP address is not allowable for use within the Routing Header,
    the Binding Acknowledgment MUST be sent to the mobile node's home
    address.

All these texts refer to addresses allowable for use within the
Routing Header. The given list does not appear to match RFC 2460's
definition of allowable addresses, as it only disallows multicast
addresses. Furthermore, some of the text talks about the IPv6
destination address and still refers to the allowable RH
addresses.

Proposal: It is unnecessary to refer to other documents for the
allowable addresses. We can simply list them in our document.
Two alternative ways to do this:

1) List the illegal address types, i.e., a multicast address,
    link-local address, loopback address, IPv4 mapped address,
    or the unspecified address.
2) List the legal address types, i.e., global unicast
    address.

I'm concerned that we might miss something by picking the first
scheme. And what if there are new address types in the future?