MN-3-3-1-1-003 - Use Neighbor Unreachability Detection (Target Address=global)




                                  R       CN0
                                  |        |
                     -----+-------+--------+---------------- LinkZ
                          R2                      NUTY
                          |                         |
                     -----+-------+-----------------+------- LinkY
                                  R1              NUTX
                                  |                 |
                     -----+-------+-----------------+------- LinkX
                         HA0             Node0    NUT0
                          |               |         |
    ----------------------+---------------+---------+------- Link0
Link0 3ffe:501:ffff:100::/64 home link
LinkX 3ffe:501:ffff:102::/64  
LinkY 3ffe:501:ffff:103::/64  
LinkZ 3ffe:501:ffff:104::/64  
HA0(Link0) 3ffe:501:ffff:100:200:ff:fe00:a0a0  
Node0(Link0) 3ffe:501:ffff:100:200:ff:fe00:a3a3  
R1(LinkX) 3ffe:501:ffff:102:200:ff:fe00:a4a4  
R2(LinkY) 3ffe:501:ffff:103:200:ff:fe00:a6a6  
CN0(LinkZ) 3ffe:501:ffff:104:200:ff:fe00:a8a8  


 1. Selection Option
    - none.
 2. Position of Mobile Node
    - none.


       HA0     NUT0     R1      R2      CN0
        |       |       |       |        |
        | ----> |       |       |        | 1.Router Advertisement
        |       |       |       |        |
        |      NUTX     |       |        |
        |       |       |       |        |
        |       | <---- |       |        | 2.Router Advertisement
        |       |       |       |        |
        | <---- |       |       |        | 3.Neighbor Solicitations(NUD) (*1)
        |       |       |       |        | 4.(no reply)
        |       |       |       |        |
        1. Send Router Advertisement. (HA0 -> HA0_allnode_multi)
            # The Router Address (R) bit is ON.
        2. Send Router Advertisement. (R1 -> R1_allnode_multi)
        3. Receive Neighbor Solicitations(NUD). (NUT0 -> HA0)
        4. (no reply)
            # Wait during a maximum of 3 seconds(RFC2461).


 (*1) PASS: HA0 receives Neighbor Solicitation(NUD).
            Then, check whether this packet fills all of the following.
             - The target address is set to HA0 global address of Router Advertisement[1].


11.5.1 Movement Detection
   Mobile nodes can use the information in received Router
   Advertisements to detect L3 handovers.  In doing so the mobile node
   needs to consider the following issues:
   o  There might be multiple routers on the same link, thus hearing a
      new router does not necessarily constitute an L3 handover.
   o  When there are multiple routers on the same link they might
      advertise different prefixes.  Thus even hearing a new router with
      a new prefix might not be a reliable indication of an L3 handover.
   o  The link-local addresses of routers are not globally unique, hence
      after completing an L3 handover the mobile node might continue to
      receive Router Advertisements with the same link-local source
      address.  This might be common if routers use the same link-local
      address on multiple interfaces.  This issue can be avoided when
      routers use the Router Address (R) bit, since that provides a
      global address of the router.
   In addition, the mobile node should consider the following events as
   indications that an L3 handover may have occurred.  Upon receiving
   such indications, the mobile node needs to perform Router Discovery
   to discover routers and prefixes on the new link, as described in
   Section 6.3.7 of RFC 2461 [12].
   o  If Router Advertisements that the mobile node receives include an
      Advertisement Interval option, the mobile node may use its
      Advertisement Interval field as an indication of the frequency
      with which it should expect to continue to receive future
      Advertisements from that router.  This field specifies the minimum
      rate (the maximum amount of time between successive
      Advertisements) that the mobile node should expect.  If this
      amount of time elapses without the mobile node receiving any
      Advertisement from this router, the mobile node can be sure that
      at least one Advertisement sent by the router has been lost.  The
      mobile node can then implement its own policy to determine how
      many lost Advertisements from its current default router
      constitute an L3 handover indication.
   o  Neighbor Unreachability Detection determines that the default
      router is no longer reachable.
   o  With some types of networks, notification that an L2 handover has
      occurred might be obtained from lower layer protocols or device
      driver software within the mobile node.  While further details
      around handling L2 indications as movement hints is an item for
      further study, at the time of writing this specification the
      following is considered reasonable: