Re: reviews of draft-ietf-6man-addr-select-opt-01

Matthew,
thank you for looking at it.

On 2012/02/16, at 3:38, Matthew Ryan wrote:

>
> I note that the descriptions for the 'suboption-zone-index'
> and 'z-bit' in Section 2 say that if the z bit is present,
> the zone-index field is inserted between prefix-len and prefix.
> This does not appear to be borne out by the diagram.  I assume
> the text was not updated when the format was changed.

Ops. Thank you for pointing out.

>
> Also, the 'suboption-len' field  "specifies the length of
> the suboption fields in bytes".  If there is the desire to
> potentially include multiple suboptions, this will not be
> sufficient, because you have no way of telling them apart.
> If this option is to have sub-options, then they should be
> formatted as in other options that have sub-options: each
> sub-option prefixed by a code and a length.

This was intended to be skipped when a new option was defined
other than the suboption-zone-index and an old implementation
does not know how to deal with it.

I agree that normal suboption style should be better.
I'll change it that way, if we agree on it.

> As for the prefix, I think it should follow the same form as
> in the IA_PD Prefix option [RFC-3633 section 10].  That is, a
> single octet indicating prefix length in bits, followed by a
> fixed-length 16 octet address.  Having a variable-length address
> complicates implementation, especially when the length field
> unit is bits, not octets.  It would require server implementers
> to write custom code simply to handle the option usefully,
> where there already exists code to handle the form used in
> the IA_PD Prefix option.

hmmmm, it is clearly trade-off.

We do not expect a lot of prefixes for IA_PD option, but
we can expect more than ten options are included to deliver
the policy table.

> Finally, I'm not sure I see the need for the "z-bit", since
> the zone-index is at the end.  You don't need it to indicate
> the presence of zone-index, since you easily see if zone-index
> is present while parsing the packet, regardless of whether
> it is a sub-option, or just an optional 32-bit value at the
> end (and there are no other sub-options).

I understand.
As far as the z-bit is the only bit, we do not need it.

Kindest regards,


--
Arifumi Matsumoto
  NGN System Architecture Project
  NTT Service Integration Laboratories
  E-mail: arifumi@...
  TEL +81-422-59-3334 FAX +81-422-59-6364

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