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

[Subba Reddy <subbareddy@samsung.com>]

Hi Greg,

<cut>

> 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.
>

I am just giving one example, where H may not take wrong decision.

If the H stays for atleast 3 hours (worst case) in the Link L, H will
delete that linkid from list and will not make wrong decision when
it is moved to Link M.

In detail,
Let us say life time of P is 10 hrs when the P is removed from L and
assigned to M.
Sice Router2 don't know the removal of P, it will be advertising P as
linkid.
After 1.5hrs, Router2 will stop advertising as linkid (since the prefix is
not updated
by any router, in this case Router1). Let us say H has received the last RA
from Router2
with P as linkid (exactly after 1.5hrs after P is removed). After 1.5 hrs
from this point of
time H also will remove P from linkid list, since it is not updated in the
last 1.5hrs.
So after 3 hrs, P will be removed from linkid list of H.

Thanks & Regards,
Subba Reddy