Subject: Re: [MOBILE-IP] Binding Cache entries per IPv6 address at Corresp ondent Node

From: "Powell, Ken" <[email-masked]>
Date: Thu, 9 Nov 2000 14:20:19 -0500

I'm not sure how the clause "for each of its IPv6 addresses"
applies when the prefix length is non-zero. In this case, a
single binding covers multiple addresses.

>
>  Binding Cache
>
>          A cache, maintained by each IPv6 node, of bindings for other
>          nodes.  A separate Binding Cache SHOULD be maintained by each
>          IPv6 node for each of its IPv6 addresses.
>
>                       ...........
>
>                  The contents of all of a node's Binding
> Cache entries,
>          for each of its IPv6 addresses, must be cleared when the node
>          reboots.
>
>
>
> In addition, I have changed several places where it seems to
> read better to allow multiple Binding Caches (one per IPv6 address).
>
> Does this fix the problem, without introducing any new problems?
>
> Regards,
> Charlie P.
>

---

From: Mattias Pettersson <[email-masked]>
Date: Fri, 10 Nov 2000 10:31:54 +0100

> single binding covers multiple addresses.

It's the CN/HA that keeps a BC for each of its _own_ addresses. Not one
for every address the MN has. Or do I misunderstand you?

This led me to another question of the draft:

     Prefix Length

         The Prefix Length field is valid only for a "home registration"
         Binding Update; this field MUST be zero if the Home
         Registration (H) bit is not set in the Binding Update.  The
         Prefix Length field is set by the sending mobile node to the
         (nonzero) length of its subnet prefix in its home address
         (given in the Home Address option in the packet) to request
         its home agent to use the interface identifier in the mobile
         node's home address (the remaining low-order bits after the
         indicated subnet prefix) to form all other home addresses for
         the mobile node on the home link.  The home agent becomes the
         home agent not only for the individual home address given in
         this binding, but also for all other home addresses for this
         mobile node formed from this interface identifier.  That is,
         for each on-link prefix on the home link, the home agent uses
         the interface identifier to form other valid addresses for
         the mobile node on the home link, and acts as a home agent
         also for those addresses.  In addition, the home agent forms
         the link-local address and site-local address corresponding
         to this interface identifier, and defends each for purposes
         of Duplicate Address Detection.  The home agent also performs
         Duplicate Address Detection on each such address as part of
         the home registration processing (before returning the Binding
         Acknowledgement), if the Duplicate Address Detection (D) bit
         is set in the Binding Update.  Details of this operation are
         described in Section 9.3.

One BU is, according to the draft, enough to register all home addresses
formed by prefixes on the home link, plus site- and link-local. However,
I feel there is a slight gap in the protocol on what home addresses
that's actually been registered. Is it pointed out somewhere else in the
spec where the HA explicitly tells the MN about the addresses
registered, so that the MN can prepare to receive packets to these
addresses? Or, as I guess is assumed, the HA should already have
informed the MN in an RA about what prefixes are valid.

Though, if the MN wants total control of the addresses being registered,
I guess the MN can set prefixlen to zero and register each address in a
separate BU.

/Mattias