Route Optimization based on ND-Proxy for Mobile Nodes in IPv6 Mobile Networks

1. VTC2004- Spring Route Optimization based on ND-Proxy for Mobile Nodes in IPv6 Mobile Networks Jaehoon Jeong, Kyeongjin Lee, Jungsoo Park, Hyoungjun KimETRI{paul,leekj,pjs,khj}@etri.re.kr http://www.adhoc.6ants.net/~paulThis paper and presentation material are posted on the above site.

2. Contents • Motivation • Network Mobility (NEMO) • Related Work • Main Idea • Multilink Subnet • ND-Proxy based Route Optimization • Procedure of Route Optimization in Mobile Node • Analysis of Route Optimization • Conclusion

3. Motivation • Network Mobility (NEMO) Basic Support protocol • Object of NEMO • NEMO allows a mobile network reachable in the Internet through Mobile IPv6 Extension. • NEMO is being developed at IETF NEMO working group • Limitation of Current NEMO Protocol • NEMO supports network mobility by bi-directional tunneling between Mobile Router (MR) and Home Agent (HA). • This does not support route optimization between Mobile Network and Correspondent Node. • Goal of This Paper • Support of Direct Communication between Mobile Node (MN) and Correspondent Node (CN) through Optimal Path

4. Network Mobility (NEMO) – 1/2 • Role of NEMO Protocol • Session Continuity of Mobile Network Node (MNN) • Connectivity of MNN • Reachability of MNN • Location Management • Key Idea of NEMO • HA forwards data packets destined for Mobile Network. • HA maintains the forwarding information related to Mobile Network Prefix(es).

5. Network Mobility (NEMO) – 2/2 • Management of Mobile Network Prefix • Binding Update of Implicit Mode • Binding Update of Explicit Mode • Dynamic Routing Protocols • Refer to NEMO draft for detailed information • draft-ietf-nemo-basic-support-02.txt

6. Related Work • Route Optimization based on Prefix Delegation • Mobile Router (MR) gets a Network Prefix of Access Network through Prefix Delegation Protocol, such as DHCPv6. • MR gets a new prefix from Access Router on a foreign link. • MR provides the prefix for its Mobile Nodes, which is used to make Care-of Address of Mobile Node within Mobile Network. • The prefix is advertised through Router Advertisement (RA) message by MR. • Route Optimization • This makes a direct communication between CN and MN possible via an optimal path, not via a bi-directional tunnel between MR and HA.

7. Main Idea • Route Optimization though Proxying • Mobile Router (MR) provides the network prefix of its Care-of Address (CoA) for its mobile nodes by playing the role of Neighbor Discovery (ND) Proxy. • Refer to draft-ietf-ipv6-multilink-subnets-00.txt • Mobile Node (MN) can make its CoA as if it is attached to access network directly like MR. • MN and CN can communicate each other via an optimal path because MR forwards their packets as proxy.

8. Multilink Subnet • Multilink Subnet • A collection of independent links, connected by routers, but sharing a common subnet prefix. • A Multilink Subnet consists of Subnet, NEMO1 and NEMO2 like in the figure.

9. ND-Proxy based Route Optimization • Advertisement of Access Network Prefix • Access Router AR1 advertises its subnet prefix, AR1_P, like in the figure. • MR1, MR2 and MR3 relay the prefix information received through Proxy-mode interface to Router-mode interface.

10. Procedure of Route Optimization in Mobile Node – 1/2 • Generation of a new CoA • MN makes its new CoA with access network prefix advertised by MR. • DAD for the new CoA • MN performs Duplicate Address Detection (DAD) of its new CoA. • The DAD message, Neighbor Solicitation, is disseminated to the entire mobile network, a multilink subnet by MRs. • MRs store the MN’s link-local address included in DAD message in their Neighbor Cache. • The link-local address in MR’s Neighbor Cache is used to forward data packets destined to the MN. • Return Routability and Binding Update • MN performs Return Routability and Binding Update for Route Optimization like in Mobile IPv6.

11. Procedure of Route Optimization in Mobile Node – 2/2 • Delivery of Data Packets • When AR receives data packets destined to an MN and there is no neighbor information for the MN, • The AR multicasts a Neighbor Solicitation (NS) message for address resolution to the solicited-node multicast address of the MN’s IPv6 address. • If an MR knows the link-layer address of the MN, • As ND-Proxy, the MR responds to the NS message by returning its own link-layer address with a unicast Neighbor Advertisement (NA) to the source of the NS message. • Like this, a path is set up between AR and MN through intermediate MRs and AR can forward data packet to MN.

12. Analysis of Route Optimization 1. Dog-legged Routing via Bi-directional Tunnel 2. Route Optimization via Optimal Path Delay Difference of 1 and 2  d where d is the distance b/w HA & MR

13. Conclusion • Route Optimization in Multiple Nested Mobile Networks • The communication based on bi-directional tunnel leads to add tunneling delay in proportion to the number of nested mobile network’s levels. • Route optimization in this paper reduces packet delay, packet size and tunneling overhead in Mobile Router. • Because packet size becomes bigger due to extra IPv6 header attached to packet per level of nesting. • Route Optimization for Mobile Nodes is necessary and important when thinking about applicable scenarios. • Network Mobility Service in Public Transportation, such as Bus, Train and Airplane.