Subject: [Monami6] De-Registration BU in MCoA draft

From: Keigo Aso <[email-masked]>
Date: Fri, 28 Apr 2006 13:42:51 +0900

Hello,

I have question about de-registration BU.

In section 5.5 "Using Alternate Care-of Address",
   "In these cases, the mobile node sends a Binding Update with both
   Alternate Care-of Address sub-option and Binding Unique Identifier
   sub-option. "

Does the De-Registration Binding Update have to contain 
Care-of Address to indicate the address which will be deleted 
by using Alternate Care-of Address sub-option or Source Address ? 
Containing both BID sub-option and "specified Care-of Address"
in De-Registartion BU seems to be redundant. 

Regards,
Keigo

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From: Gábor Fekete <[email-masked]>
Date: Fri, 28 Apr 2006 10:00:07 +0300

Hi Keigo and list,

> in De-Registartion BU seems to be redundant.

I agree. Actually section 5.3 "Sending De-Registration Binding Update" says
  "other hand, if the mobile node wants to remove multiple Care-of
   Addresses at once, it stores multiple Unique Binding Identifier sub-
   options and Alternate Care-of Address sub-options in a Binding
   Update.  The Care-of Addresses stored in the Alternate Care-of
   Address sub-options will be all removed."

It is not clear why the AltCoAs are needed. And it misses to mention wether
the B-flag must be set or not in this case (I guess yes).
And since two different BIDs may correspond to the same CoA, the last sentence
in section 5.3 is a bit misleading. For me it tells that
if the AltCoA contains CoA-A then every binding having CoA-A will be removed
no matter what their BIDs are.
So it is not clear whether a de-reg BU says "de-register this BID" or
"de-register this CoA".

Plus RFC3775 says that for de-reg the HoA must be equal to the CoA or the
lifetime be zero. And in this regard the de-reg in the multiplecoa draft is
a bit inconsistent with RFC3775.

Regards,
Gabor