Re: [DNA] Re: LinkID v.s. Landmark Prefix

[JinHyeock Choi <jinchoe@gmail.com>]

Greg
 
> Link Identifiers
> ---------------------
> 
> A Host H, exists and moves around the Internet.
> 
> On an link unvisited by the host, Link L, a prefix, P is
> retracted by one of the routers Router1. Subsequent to this,
> the actual lowest prefix on the link is Prefix Q.
> 
> 
> Another router, Router2 fails to see the prefix retraction.
> (Perhaps RAs are lost, or Router1 didn't comply with
> section 6.2.6 of RFC2461).
> 
> The prefix is then reassigned within its previous
> lifetime to another link, link M, whose lowest prefix
> was prefix T.  Link M, has also not been visited by
> host H.
> 
> Link Identifiers are in use on both Link L and
> Link M.  On Link M, all routers advertise Prefix P
> as current LinkID and Prefix T as OldLinkID.
> 
> On Link L, Router2 advertises prefix P as Current LinkID.
> 
> If the host H arrives on Link L, it may receive
> Prefix P as LinkID even though it is no longer present
> on-link.  The host would configure Prefix Q (or a higher prefix)
> which is advertised in a PIO.
> 
> If the LinkID is not contradicted, for example if there are
> no other advertising routers left on the link, when the host
> moves to Link M, it will also receive an RA with prefix P as
> the Current LinkID.  The Old LinkID will be ignored (it hasn't
> been seen before).
> 
> In this case, no change will be detected upon arrival to
> link M, and the previous prefix will remain configured.

The above example gives a problem because a linkid prefix is 
reassigned to the other link within 3 hours. 

The draft recommends that a linkid prefix should not be reassigned
to other link within 3 hours. 

If network administrator follows the recommendation, such
a problem won't happen. So I don't think we need to worry about 
this problem.  

> I understand that LinkID is quite robust against change.
> 
> The point I originally was making was that while it is robust,
> All of the schemes are flawed to some extent.

I can't deny the possibility but don't think your example
showed such a flaw. The false detection comes from 
human error. 

Best Regards

JinHyeock