Re: [MEXT] Review of draft-ietf-monami6-multiplecoa-13 + Proposals

[Julien Laganier <julien.laganier.ietf at googlemail.com>]

Hello Ryuji, 

Cutting thru quite a bit:

On Monday 11 May 2009, Ryuji Wakikawa wrote:
> 
> [...]
> >>   Binding ID (BID)
> >>
> >>      The BID which is assigned to the binding indicated by the
> >> care- of
> >>      address in the Binding Update or the Binding Identifier
> >> mobility option.  The BID is a 16-bit unsigned integer.  The value
> >> of zero
> >>      is reserved and MUST NOT be used.
> >
> > The value MUST NOT be used. 2 questions:
> >  - maybe the rationale for that decision could be provided
> >  - what if a peer receives a BID with that value. What behavior is
> >    specified in that case and what will it allow if at some point
> > that reserved value needs to be used?
>
> This is actually SHOULD NOT.
> This is error when I updated the document.
>
> In section 5.1, we've had the update texts.
>     "A mobile node assigns a BID to each care-of address when it
> wants to
>     register them simultaneously with its home address.  The BID MUST
> be unique for a given home address.  The value is an integer between
> 1 and 65535.  Zero value SHOULD NOT be used as BIDs.  If a mobile
> node has only one care-of address, the assignment of a BID is not
> needed until it has multiple care-of addresses to register with, at
> which time all of the care-of addresses MUST be mapped to BIDs."
>
> Any future document can overwrite this spec.
> As for MCoA, we don't use zero value.
>
> There is background story here. The flow binding document needs
> default binding.
> We had used zero value to specify the default binding in MCoA.
>
> After the long discussion in WG, we agreed not to have this value in
> MCoA.
> The default binding should be defined in the flow binding.

Sorry to jump in the discussion, but IMHO what you want to achieve would 
actually be better reflected with the following than by a "value zero 
SHOULD not be used":

In 4.3.
-------

   Binding ID (BID)

      The BID which is assigned to the binding indicated by the care-of
      address in the Binding Update or the Binding Identifier mobility
      option.  The BID is a 16-bit unsigned integer.  The value of zero
      is reserved and MUST NOT be set by the sender and MUST be treated
      as an error by the receiver (MCOA MALFORMED).


In 5.1.
-------

   A mobile node assigns a BID to each care-of address when it
   wants to register them simultaneously with its home address. For a
   given home address, the assigned BID MUST be a unique integer between
   1 and 65535. The BID value zero MUST NOT be assigned, MUST NOT be
   sent in a Binding Identifier Mobility Option, and MUST be treated as
   an error (MCOA MALFORMED) by the receiver of a Binding Identifier
   Mobility Option. If a mobile node has only one care-of address, the
   assignment of a BID is not needed until it has multiple care-of
   addresses to register with, at which time all of the care-of
   addresses MUST be mapped to BIDstoo.

What do you think?

--julien