Individual Submission Internet Draft Jae-Hoon Jeong Kyeong-Jin Lee Jung-Soo Park Hyoung-Jun Kim ETRI Expires: December 2003 7 June 2003 ND-Proxy based Route Optimization for Mobile Nodes in Mobile Network Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 except that the right to produce derivative works is not granted [1]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document specifies a mechanism for enabling mobile nodes in IPv6 mobile network to perform route optimization. The route optimization is possible because mobile router provides the prefix of its care-of- address for its mobile nodes by playing the role of ND-proxy. Through binding updates associated with the network prefix of an access network, the mobile nodes can perform route optimization. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [2]. Jeong, Lee, Park, Kim Expires - December 2003 [Page 1] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 Table of Contents 1. Terminology...................................................2 2. Introduction..................................................2 3. Overview......................................................2 4. Mobile Router extension : Process of Prefix Information option for Route Optimization (RO)...................................3 5. Neighbor Discovery extension..................................4 5.1 RO Prefix Information option format.......................4 5.2 Neighbor Solicitation (NS) message format.................5 6. Procedure of Route Optimization...............................6 6.1 Generation of a new CoA...................................6 6.2 DAD for the new CoA.......................................6 6.3 Return Routability and Binding Update.....................6 6.4 Delivery of Data Packets..................................6 7. Security Considerations.......................................7 8. References....................................................7 9. Acknowledgements..............................................7 10. Authors' Addresses...........................................8 1. Terminology This document uses the terminology described in [3]-[6]. Especially three important terms are as follows [5]: Multilink Subnet (MS) A collection of independent links, connected by routers, but sharing a common subnet prefix. ND-Proxy A router proxying and relaying for all nodes on its router-mode interfaces except proxy-mode interfaces among its network interfaces. Multilink-Subnet Router (MSR) A router which has interfaces attached to different links in a MS, and which plays the role of ND-Proxy. 2. Introduction The basic support of mobile network (NEMO) enables mobile network nodes and correspondent nodes to communicate through bi-directional tunnels. Deeper multi-level network this NEMO gets, longer the delay becomes by dog-legged routing. This document specifies how to optimize the routes between mobile nodes and correspondent nodes. 3. Overview Jeong, Lee, Park, Kim Expires - December 2003 [Page 2] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 This route optimization is possible by a mobile router performing ND- Proxy, which makes a care-of-address (CoA) with the prefix advertised by access router and delivers the prefix of access network into the NEMO. Each mobile node can make its new CoA with router advertisement message including access network prefix and perform the return routability and binding update procedure. As ND-Proxy, the mobile router performs neighbor discovery instead of the mobile nodes within its NEMO. Like this, access network and NEMO are configured into a multilink subnet through mobile router that performs ND-Proxy. Figure 1 shows an example of a multilink subnet comprised of four links from Link1 to Link4. Three mobile routers from MR1 to MR3 relay the prefix information of access network (AR1_P) that was sent by an access router, AR1. The mobile nodes, MN1 and MN2, within the NEMO controlled by MR1 can perform route optimization with the prefix information relayed by its mobile router, MR1. Also, MN3 can optimize the route through MR2. MN4 and MN5 can perform route optimization through MR2 and MR3, too. +---+ |AR1| RA(AR1_P)| +-+-+ V | ----------+---------------+---------------+----------- Link1 |Proxy-mode |Proxy-mode +-+-+ +-+-+ |MR1| |MR2| RA(AR1_P)| +-+-+ RA(AR1_P)| +-+-+ V |Router-mode V |Router-mode ---+-----+-----+--- Link2 ---+------+-----+--- Link3 | | | Proxy-mode| +-+-+ +-+-+ +-+-+ +-+-+ |MN1| |MN2| |MN3| |MR3| +---+ +---+ +---+ +---+ | RA(AR1_P) Router-mode| V ---+-----+-----+--- Link4 | | +-+-+ +-+-+ |MN4| |MN5| +-+-+ +-+-+ Figure 1. Multilink Subnet for Route Optimization 4. Mobile Router extension : Process of Prefix Information option for Route Optimization (RO) Jeong, Lee, Park, Kim Expires - December 2003 [Page 3] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 Mobile router MUST perform the role of ND-Proxy and relay the prefix information that is received from an access router. Before mobile router advertises the prefix information through Router Advertisement (RA) message, it MUST set route-optimization flag indicating that this prefix can be used for route optimization of mobile nodes, which are either local mobile nodes or visiting mobile nodes within the mobile network. If a mobile node within a mobile network receives the new prefix information option through RA message and can recognize this option, it MAY prefer this new prefix information option to the normal prefix information option that contains the mobile network prefix assigned by the mobile router's home network. By performing binding update with the prefix of the access network, the mobile node can optimize the routes between its correspondent nodes and itself. 5. Neighbor Discovery extension 5.1 RO Prefix Information option format The mechanism of this document needs the addition of a new flag within prefix information option for route optimization [3]. When this flag is set, it indicates that the prefix included in the option can be used by mobile nodes within a NEMO for the route optimization. Figure 2 shows the format of the modified prefix information option, RO Prefix Information option. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Prefix Length |L|A|O|Reserved1| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Valid Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preferred Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. Prefix Information Option Format for Route Optimization Jeong, Lee, Park, Kim Expires - December 2003 [Page 4] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 Field: O 1-bit route-optimization flag. When set indicates that this prefix can be used for the route optimization of mobile nodes within NEMO. The RO Prefix Information option provides a mobile node with the network prefix of access network and allows it to autoconfigure its new CoA through stateless address autoconfiguration and to perform binding update. The Prefix Information option appears in RA message and MUST be silently ignored for other messages. L (On-link) flag MAY be either 0 or 1. Namely, this route optimization can be either on-link or off-link model [5]. A (Autonomous address-configuration) flag MUST be 1, indicating IPv6 stateless address autoconfiguration. 5.2 Neighbor Solicitation (NS) message format NS message MUST be extended for Duplicate Address Detection (DAD) for the address based on RO prefix of access network. Therefore, there is a need to discriminate between the normal NS message and extended NS message for route optimization [3]. Figure 3 shows the format of the modified NS message. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |M| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Target IPv6 Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- Figure 3. Extended Neighbor Solicitation Message Format Fields: M 1-bit multi-hop flag. When set indicates that this NS message SHOULD be relayed to the other Jeong, Lee, Park, Kim Expires - December 2003 [Page 5] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 links of multilink subnet. Target IPv6 Address The IPv6 address of the target of the solicitation that will be used as CoA. It MUST NOT be a multicast address. 6. Procedure of Route Optimization 6.1 Generation of a new CoA Whenever a mobile node first receives RA message containing RO prefix information option that includes a new network prefix of access network, it makes a new CoA. 6.2 DAD for the new CoA The mobile node performs DAD for the new CoA through the extended NS message. The NS message of DAD for the new address is relayed by a mobile router, acting as ND-Proxy, on the link where the mobile node is placed [5]. The mobile router memorizes the DAD for returning NA message to the sender of the extended NS message. If there is no NA returned and the DAD is successful, the mobile node configures the address as its new CoA in its network interface. Notice that the DAD for the link-local addresses and global addresses based on mobile network prefix assigned by home network is performed through normal NS message only within a link and the DAD for the global addresses based on access network prefix is performed through extended NS message within a multilink subnet, which is relayed by ND-Proxies. 6.3 Return Routability and Binding Update After configuring the new CoA, the mobile node performs the return routability and binding update procedure of Mobile IPv6 [7]. 6.4 Delivery of Data Packets After binding update, the data packets of correspondent nodes toward the mobile node are delivered to the access network to which the NEMO containing the mobile node is attached via optimal paths. When the access router of the access network receives the data packets, it multicasts normal Neighbor Solicitation (NS) message to the solicited-node multicast address of the destination IPv6 address Jeong, Lee, Park, Kim Expires - December 2003 [Page 6] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 in order to find out the link-layer address of the destination node. The mobile router, knowing the link-layer address of the target, responds to the NS message by returning its own link-layer address in a unicast Neighbor Advertisement (NA) message as ND-Proxy, which knows the IPv6 addresses and link-layer addresses of mobile nodes within its mobile network during the DAD of each CoA of each mobile node. When the access router knows the link-layer address to the destination, it forwards the IPv6 data packets to the mobile router corresponding to the link-layer address. The mobile router relays the packets to the destination mobile node. In case that the NEMO where the destination node is placed is multi-level, the packets may be relayed to the destination node by more than one mobile router. 7. Security Considerations The route optimization in this document does not add any other security problems to the NEMO or Mobile IPv6. 8. References [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] T. Narten, E. Nordmark and W. Simpson, "Neighbour Discovery for IP version 6", RFC 2461. [4] S. Thomson and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462. [5] Dave Thaler and Chistian Huitema, "Multi-link Subnet Support in IPv6", draft-ietf-ipv6-multilink-subnets-00.txt, June 2002. [6] Thierry Ernst, "Network Mobility Support Terminology", draft- ietf-nemo-terminology-00.txt, May 2003. [7] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-22.txt, May 2003. 9. Acknowledgements The authors would like to acknowledge the previous contribution of Dave Thaler and Christian Huitema. Jeong, Lee, Park, Kim Expires - December 2003 [Page 7] Internet-Draft ND-Proxy based Route Optimization for MN June 2003 10. Authors' Addresses Jae-Hoon Jeong ETRI / PEC 161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea Phone: +82 42 860 1664 EMail: paul@etri.re.kr Kyeong-Jin Lee ETRI / PEC 161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea Phone: +82 42 860 6484 EMail: leekj@etri.re.kr Jung-Soo Park ETRI / PEC 161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea Phone: +82 42 860 6514 EMail: pjs@etri.re.kr Hyoung-Jun Kim ETRI / PEC 161 Gajong-Dong, Yusong-Gu Daejon 305-350 Korea Phone: +82 42 860 6576 EMail: khj@etri.re.kr Jeong, Lee, Park, Kim Expires - December 2003 [Page 8]