Subject: RE: [Mip6] A Question on Mobile IPv6 -- Alternate Care-of Address option

From: Soliman Hesham <[email-masked]>
Date: Sun, 16 Nov 2003 00:52:55 -0500

>         "...Normally, a Binding Update specifies the desired 
 > care-of address
 > in the Source Address field of the IPv6 header.  However, this is not
 > possible in some cases, such as when the mobile node wishes 
 > to indicate a
 > care-of  address which it cannot use as a topologically 
 > correct source
 > address  (Section 6.1.7 and Section 11.7.2) or when the used security
 > mechanism does   not protect the IPv6 header (Section 11.7.1)...."
 > 
 > What I am wondering is when return routability procedure is 
 > used before the
 > BU (with the Alternate Care-of Address option) is sent, how could the
 > Care-of Test Init and Care-of Test messages be performed for 
 > the address in
 > the Alternate Care-of Address option? Correspondent node 
 > can't get the
 > alternate care-of address through the Care-of Test Init, can 
 > it? 

=> The alternate coa is also assigned to the MN. So when the 
MN runs the return routability test, it MUST use that CoA
in the COTI/COT messages. I.e. the same address used in those
messages must be used in the BU. Otherwise nothing will
work. This is done in HMIPv6 for example. 

   Thus the
 > Care-of keygen toden is not calculated based on the alternate care-of
 > address. 

=> It must be calculated based on the alternate CoA. 
You assumed that it is not for some reason. 

Hesham

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