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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.krhttp://www.adhoc.6ants.net/~paul

This paper and presentation material are posted on the above site.

VTC2004- Spring

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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

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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 NEMO supports network mobility by bi-directional tunneling between

Mobile Router (MR) and Home Agent (HA).Mobile Router (MR) and Home Agent (HA). This does not support route optimization between Mobile Network This does not support route optimization between Mobile Network

and Correspondent Node.and Correspondent Node.

Goal of This Paper Support of Direct Communication between Mobile Node Support of Direct Communication between Mobile Node

(MN) and Correspondent Node (CN) through Optimal (MN) and Correspondent Node (CN) through Optimal PathPath

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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 Ne

twork Prefix(es).

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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

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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 vi

a an optimal path, not via a bi-directional tunnel between MR and HA.

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Main Idea

Route Optimization though Proxying Mobile Router (MR) provides the network prefix of its Care-of Ad

dress (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.

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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.

Internet

CISCOSYSTEMS

Wireless Link

Fixed Node1(FN1)

Mobile Node1(MN1)

NEMO1

Mobile Router1(MR1)

Fixed Node2(FN2)

Mobile Node2(MN2)

NEMO2

Mobile Router2(MR2)

Wireless Link

Multilink Subnet

SubnetAccess Router

(AR)

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ND-Proxy based Route Optimization

AR1

Link 1

Link 2 Link 3

Link 4

RA(AR1_P)

Proxy-mode

Router-mode

Proxy-mode

Proxy-mode

Router-mode

Router-mode

MN1 MN2 MN3

MN4 MN5

MR1 MR2

MR3

RA(AR1_P)

RA(AR1_P)

RA(AR1_P)

Internet

Multilink Subnet

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.

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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 packet

s destined to the MN.

Return Routability and Binding Update MN performs Return Routability and Binding Update for Route O

ptimization like in Mobile IPv6.

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Procedure of Route Optimization in Mobile Node – 2/2

Delivery of Data Packets When AR receives data packets destined to an MN and ther

e is no neighbor information for the MN, The AR multicasts a Neighbor Solicitation (NS) message for address re

solution 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.

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Analysis of Route Optimization

Internet

Home Agent(HA)

Mobile Router(MR)

Correspondent Node(CN)

Mobile NetworkHome Network

Distance (d)

Mobile Node(MN)

Bi-directional Tunnel

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

Internet

Home Agent(HA)

Mobile Router(MR)

Correspondent Node(CN)

Mobile NetworkHome Network

Distance (d)

Mobile Node(MN)

Bi-directional Tunnel

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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.