RE: I-D ACTION:draft-hoon-mobileip-undad-00.txt

Jae-Hoon and Youn-Hee,

I think there is another problem with this draft... the router doesn't
know when a host leaves the link (i.e. due to link movement), therefore
if the MN leaves link A to move to a new link B and then in some short
time (i.e. 20 seconds or so) returns back to link A, the router will
think that the MN never left link A, when the MN queries the router if
its care-of address is already in use the router will respond that it
is. This would cause the MN to fail to configure the care-of address it
used before on link A.

Thanks.
- Ed

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of Greg Daley
> Sent: Monday, October 20, 2003 4:45 PM
> Cc: [email protected]; 'Youn-Hee Han'
> Subject: Re: [mobile-ip] I-D ACTION:draft-hoon-mobileip-undad-00.txt
> 
> 
> Hi Jae-Hoon and Youn-Hee,
> 
> The draft has Youn-Hee's email addres under
> Jae-Hoon's name, so I thought I'd respond
> to Youn-Hee anyway, and hope the message
> is passed on.
> 
> The idea of using Neighbor Discovery for DAD
> is a good one, if it can be made to work.
> Alper Yegin tried very hard to do this a while
> ago (I talked to him about it before IETF55),
> and there's one fatal flaw which cannot be
> recovered using ND.
> 
> While the router knows about all of the hosts on the
> link, it can indicate whether an address is unused.
> This is the same principle used for MLD-DAD
> (which has since expired... if you need the reference
> contact me).
> 
> The issue is when a router fails or comes up on a link
> for the first time, it cannot build a list of which hosts
> are already on the link.
> There is no ND message where all hosts (or even large
> groups of hosts) must respond, which can be used to rebuild
> ND state.
> 
> This means that the router may incorrectly allocate existing 
> addresses if there is a host that doesn't receive off-link 
> unicast packets at an address.
> 
> In MLD-DAD, state can be rebuilt using query messages, which 
> have no equivalent in ND.
> 
> If you wish to discuss this further, please
> feel free to discuss this either here or on the DNA
> list.
> 
> Greg Daley
> 
> [email protected] wrote:
> > A New Internet-Draft is available from the on-line Internet-Drafts 
> > directories.
> > 
> > 
> > 	Title		: Using Neighbor Caceh Entry for 
> Duplicate Address 
> > 			  Detection
> > 	Author(s)	: J. Kim, et. al.
> > 	Filename	: draft-hoon-mobileip-undad-00.txt
> > 	Pages		: 14
> > 	Date		: 2003-10-20
> > 	
> > The Duplicate Address Detection (DAD) procedure detailed by 
> Neighbor 
> > Discovery Protocol (NDP) requires nodes to wait for a 
> quantified time 
> > interval during which the configured address is checked for 
> > duplication in the connected link. This delay affects normal 
> > communication in a Mobile Node (MN) during the DAD time interval 
> > thereby hampering Fast Handoff. The expected use of Mobile IP on a 
> > wide scale and the need for a minimal time delay during the handoff 
> > process require alternate mechanisms for overcoming the DAD time 
> > interval. This draft presents a mechanism wherein the 
> Access Router's
> > (AR) Neighbor Cache Entry (NCE) is used to minimize the delay 
> > associated with the DAD procedure.
> > 
> > A URL for this Internet-Draft is: 
> > http://www.ietf.org/internet-drafts/draft-hoon-mobileip-undad-00.txt
> > 
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> > 
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