| 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.
(draft-ietf-mobileip-ipv6-24.txt) 11.5.1 Movement Detection (snip) 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 . 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: