Subject: [mobile-ip] RE: what optimistic DAD? (was Re: Address config for FMIPv6 (was Re: [mobile-ip] FMIPv6: FBUtransmission text))

From: Soliman Hesham <[email-masked]>
Date: Mon, 23 Jun 2003 21:42:54 -0400

=> Ah, as opposed to FMIPv6?

 > 
 > from draft-moore-ipv6-optimistic-dad-02.txt
 > 
 > >    It may be desirable for a Neighbour, for example the router, to
 > >    rapidly establish communication with the newly 
 > configured ON. To do
 > >    so, it must learn of the ON's arrival as soon as 
 > possible.  To avoid
 > >    having to wait for Neighbour Discovery, the ON may wish to send
 > >    unsolicited Neighbour Advertisements (with Override set
 > >    appropriately), but for this to be effective the Neighbour must
 > >    either:
 > > 
 > >    * be expecting the ON to arrive (eg: due to predictive 
 > mechanisms),
 > >         and thus already have a NC entry for the peer, in state
 > >         INCOMPLETE.
 > 
 > notice the word "predictive" there? 

=> Already noted in an earlier mail, see my response to Rajeev.

Hesham

if the new Access Router
 > is not expecting the optimistic node on the link, it does
 > not create a neighbor cache entry for the MN. this is 
 > because the Neighbor Advertisement sent by the opimitistic
 > MN has the overide bit set to 0.
 > 
 > what is the predictive mechanism here? I can only think of 
 > HI-HACK exchange.
 > 
 > this draft doesnt even have a home. the new WG is not
 > formed yet. it is a bit weird to say "HI-HACK is optional 
 > because there might a fugure optimistic DAD mechanism 
 > defined in an yet to be formed WG".
 > 
 > the mobile needs to be able to do the following after moving 
 > to a new link
 > 
 > 1. send packets to nodes off link
 > 2. receive packets from nodes off link
 > 3. send packets to nodes on link
 > 4. receive packets from nodes on lnk.
 > 
 > draft-moore does not solve (2). the only thing new in 
 > draft-moore is how it solves (3). 
 > 
 > for (1), the mobile node sends packets to the default router.
 > the MAC address of the default router was obtained through a
 > router advertisement. but this does not work if the router
 > advertisement did not contain the source link layer address
 > option.
 > 
 > for (2), an unsolicited NA from the mobile node creates a
 > neighbor cache entry at the access router. but this works
 > only if a predictive mechanism has already warned the 
 > access router to expect a mobile node to show up.
 > 
 > for (3), the mobile node sends a packet to the defaul router.
 > but an ICMP redirect from the default router creates a neighbor
 > cache entry for the destination on link. this is new.
 > 
 > for (4), the mobile node can respond to neighbor solicitations
 > from other nodes on the link.
 > 
 > draft-moore does not work without a predictive mechanism.
 > Nick, Greg, please correct me if I am wrong.
 > 
 > Vijay
 >