Subject: RE: [mobile-ip] MIPv6 v20 question re L bit

From: "Greg O'Shea" <[email-masked]>
Date: Wed, 5 Feb 2003 08:25:55 -0000

>> Aside: another (hopefully moot) point is that my reading of the spec 
>> allows an HA to derive and test the LLA even when L=0 is 
>received - it

The spec just needs to be tightened to say what the HA must NOT do when
L=0. Strictly speaking this cannot safely be inferred from what it MUST
do when L=1.

>-----Original Message-----
>From: Ed Remmell [mailto:[email-masked]] 
>Sent: 04 February 2003 22:14
>To: Greg O'Shea; Mobile IPv6 mailling list
>Subject: RE: [mobile-ip] MIPv6 v20 question re L bit
>
>
>Greg -
>
>> Aside: another (hopefully moot) point is that my reading of the spec 
>> allows an HA to derive and test the LLA even when L=0 is 
>received - it 
>> says HA should protect the HoA which doesn't prevent it from 
>> protecting the LLA as well. Not that one would, presumably, but one 
>> could, so setting L=0 might not get what you expect from the HA.
>
>I expect that if I register with L=0, the HA will not be 
>defending any link-local address associated with the HoA for 
>that registration. If this is not the case, I'd like to know why.
>
>When the MN registers with L=0, it is telling the HA that it 
>does *NOT* have configured a link-local scope home address 
>which matches on the interface ID with the HoA that it is 
>registering. The HA should only be testing and defending home 
>addresses that belong to the MN. In this case, the MN has 
>explicitly told the HA that this link-local scope home address 
>is not one of its addresses, therefore the HA should not 
>defend that address. If it does, I'd consider that a broken HA 
>implementation.
>
>Granted, if there are other nodes on the home network that 
>optimize DAD, not defending the link-local scope address 
>formed from the same interface ID will be an incomplete 
>defense of the HoA, but then DAD isn't perfect, the range of 
>random interface IDs to use for RFC-3041 addresses is huge so 
>you wouldn't expect conflicts on random interface IDs that 
>frequently, the other style of interface ID is globally unique 
>so you wouldn't expect any conflicts on it, etc.
>
>Thanks.
>- Ed Remmell
>Elmic Systems, USA
>http://www.elmic.com
>
>
>