Subject: Issue 13: Omission of prefix options - resolution

From: Soliman Hesham <[email-masked]>
Date: Tue, 4 Nov 2003 04:34:42 -0500

Hi, 

This is an attempt to resolve this issue:

Issue 13: Impacts of the omission of a prefix option. 
          section 2.2 in :
        http://www.ctie.monash.edu.au/ipv6/draft-jinchoi-ipv6-cRA-00.txt
          describes the impacts of omitting a prefix option from
          an RA on movement detection for mobile nodes. RFC 2461 
          does not require options to be present in every RA.

In case you haven't had time to look through the draft 
here is the background info:

This issue raises the problem with omitting some prefixes
from an RA. The problem here is that 2461 says that a router
may choose to omit some prefixes from the RA to save BW
(i.e. while the lifetime of that prefix has not expired). 
A mobile node might take this as an indication of movement
(i.e. it is no longer reachable on the CoA that was derived
from the omitted prefix). This may unnecessarily cause the 
mobile node to send a binding update to the HA/CNs to indicate
that its CoA has changed. 

The other problem is that a host has no idea whether an RA
contains all the prefix options that are valid on a link.
Therefore, even if it sends an RS it might still get an
RA with an incomplete list of prefixes.

Suggested resolution:

- Introduce a new code (1) in the router solicitation
and advertisement. When a host sends an RS with code = 1
it requests that the RA include all prefixses valid on
that link. Similarly, when a router sends an RA with code=1
it means that the RA includes all prefixes valid on that
link. This way, a MN can confirm its mobility.

Comments?

Hesham

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