MANET Autoconfiguration (AUTOCONF) S. Singh Internet-Draft J. Kim Expires: September 7, 2006 Samsung AIT, Comm Lab C. Perkins Nokia Research Center, Communications Systems Laboratory T. Clausen LIX, Ecole Polytechnique P. Ruiz University of Murcia March 6, 2006 Address autoconfiguration for MANETs: definition and problem statement draft-singh-autoconf-adp-03 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on September 7, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract A Mobile Ad Hoc NETwork (MANET) is formed by the association of Singh, et al. Expires September 7, 2006 [Page 1] Internet-Draft ADP March 2006 mobile devices, usually wireless and capable of multi-hop communication among themselves even if there is no networking infrastructure available. MANET properties such as multi-hop, autonomous, etc requires separate address autoconfiguration mechanism. This document provides definition, problem statement and goals for ad hoc networks address autoconfiguration. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Problem statement . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Stand-alone ad hoc network . . . . . . . . . . . . . . . . 7 4.2. Ad hoc network at the edge of infra-structure network . . 8 4.3. Temporarily hybrid ad hoc network . . . . . . . . . . . . 9 4.4. Network merger and partitioning . . . . . . . . . . . . . 9 5. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 Appendix A. Normative References . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . . . 15 Singh, et al. Expires September 7, 2006 [Page 2] Internet-Draft ADP March 2006 1. Introduction A Mobile Ad Hoc NETwork (MANET) is formed by the association of mobile devices, usually wireless and capable of multi-hop communication among themselves even if there is no networking infrastructure available. However, it is generally expected that, if some MANET nodes are connected to external IP networks (e.g. Internet), they might act as gateways towards those networks. Several independent solutions have been proposed on interconnecting MANETs and the Internet[4][5][7]. Most of the solutions are related to the issues of discovering Internet gateways and auto- configuring global IP addresses that are routable within the Internet. Usually, autoconfiguration of IP addresses in MANET is also required even when the MANET is isolated from external networks. Currently there is no standard definition for commonly used MANET autoconfiguration related terminologies such as MANET local address, standalone MANET, etc. This document provides definition of such terminologies and states problems and goals for ad hoc network IP address autoconfiguration. At places, address configuration as used in this document may be read as prefix configuration. Singh, et al. Expires September 7, 2006 [Page 3] Internet-Draft ADP March 2006 2. Terminology The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [5]. Mobile Ad hoc Network (MANET) - An ad hoc network formed autonomously in an arbitrary manner by the association of mobile devices, usually wireless and capable of multi-hop communication among themselves. MANETs are characterized by highly dynamic topologies; that is, network links come and go quickly in comparison to existing wired networks. The dynamic topology may be a consequence of wireless link environment effects and/or node mobility. MANET Node - A device with one or more wireless interfaces and associated IP address(es) which is used by the MANET routing protocol in use. MANET local address - An IP address configured on a MANET node and valid for communication among MANET nodes that are part of the same ad hoc network. Nodes MUST NOT communicate with other nodes outside the MANET using this address. Global address - An IP address configured on a MANET node and valid for communication with nodes in the Internet, as well as internally within the MANET. Internet gateway - An edge node connected to MANET as well as to the Internet and capable of providing bidirectional connectivity between the Internet and MANET . These gateways are expected to provide topologically correct IPv6 prefixes. Internet gateways mostly run ad hoc routing protocols as well as infrastructure network protocols such as OSPF. Duplicate Address Detection (DAD) - The process by which a node confirms the uniqueness of an address it wishes to configure or has already configured. A node already equipped with an IP address participates in DAD in order to protect its IP address from being used by another node. Standalone ad hoc network - An independent ad hoc network which has no connectivity, either direct of via Internet gateways, to any other IP networks such as the Internet. Singh, et al. Expires September 7, 2006 [Page 4] Internet-Draft ADP March 2006 Hybrid ad hoc network - An ad hoc network which has connectivity, either direct of via Internet gateways, to other IP networks such as the Internet. They can be envisioned as a standalone MANET with one or more Internet Gateways taking part in both MANET and the Internet. Network merger - The process by which two or more ad hoc networks (either standalone or hybrid), previously disjoint, get connected. In general, network merger happens as a consequence of node mobility and/or wireless link environment. Network partitioning - The process by which an ad hoc network (either standalone or hybrid) splits into two or more disconnected ad hoc networks. In general, this proccess happens as a consequence of node mobility and/or wireless link environment. Network merger detection - The process by which MANET nodes detect network merger. Network partition detection - The process by which MANET nodes detect network partition. Singh, et al. Expires September 7, 2006 [Page 5] Internet-Draft ADP March 2006 3. Requirements o Network routes (those valid for an entire network prefix instead of just a single node) require reachability to every node which exists within the prefix, just as within the Internet. o An Internet gateway can be treated as a default router for the Internet. o An Internet gateway SHOULD maintain active routes for all nodes within the MANET which are actively engaged in communications with their partners in the Internet. o Control signals meant for nodes in the ad hoc network MUST NOT leak into the Internet. o Nodes within the Internet cannot distinguish whether or not a gateway offers connectivity to an ad hoc network or some other sort of stub network. o If two gateways advertise connectivity to the same prefix, then those two gateways MUST coordinate their routing tables so that they exhibit equal reachability for all nodes within that routing prefix. o Gateways may offer several different prefixes. A node may choose which gateway and routing prefix to use for autoconfiguration according to any convenient criterion; the methods for making the determination are not constrained to be only those specified within a MANET autoconfiguration protocol specification. o Autoconfigured addresses are likely to have lifetimes associated with them, and after the lifetime expires use of the address should be immediately discontinued or negotiated. o Address autoconfiguration solution SHOULD work well even when some nodes are temporarily disconnected or asleep. o When duplicate addresses are detected, those nodes with conflicting addresses MUST resolve the conflict. Singh, et al. Expires September 7, 2006 [Page 6] Internet-Draft ADP March 2006 4. Problem statement Specifications have been developed for address autoconfiguration in the traditional IP based network such as RFC 2462, RFC 3315 and RFC 2461. However, these specifications are not applicable to MANET nodes as-is due to their unique properties. Unlike in the traditional IP networks, each MANET node besides being traffic end- point, normally expected to forward traffic destined for other hosts. That is each MANET node normally acts as a "router" as well as a "host". Additionally, the notion of all nodes being able to access a shared communication medium fails in MANET since every node in a particular MANET do not share the same physical link. In MANET, a single transmission does not suffice for a broadcast or link-local multicast to reach all nodes constituting a particular MANET. Transmissions which are otherwise not supposed to be forwarded by routers, such as limited broadcast and link-local multicast, may need to be forwarded by the intermediate nodes in order to reach desired MANET node. In other words, nodes constituting a MANET do not share access to a single multicast-capable link for signaling. The above mentioned RFCs for address autoconfiguration in the traditional IP network assume that subnet-local signals (e.g. link-local multicast signals) are received by each of the hosts on the particular subnet without being forwarded by the routers defining the subnet boundary. Ad hoc networks can either be deployed as a standalone network or as an edge network attached to the Internet. Indeed, IETF MANET WG has this point of view for developing the MANET routing protocols. There is a growing requirement for a standard address autoconfiguration solution for MANETs that can be used by MANET nodes constituting standalone networks or edge networks. The solution should be designed with minimum modification, if any, and should be compliant with the specifications that are widely used in the traditional IP networks. The address autoconfiguration protocol has to carefully distinguish between cases when a gateway offers a routing prefix, from the case when a "local" prefix has to be used since no routing prefix is available for the purpose. 4.1. Stand-alone ad hoc network Standalone ad hoc networks are formed by a group of MANET nodes capable of spontaneously forming a multi-hop ad hoc network and has no connection (either direct of via gateways) to other IP networks such as the Internet. Examples of standalone ad hoc networks are temporary networks such as Singh, et al. Expires September 7, 2006 [Page 7] Internet-Draft ADP March 2006 conference-room networks, battlefield networks, surveillance networks, etc. In order to communicate among themselves, MANET nodes need to use Standard IP address autoconfiguration mechanism for configuring their interface(s). These addresses should be routable only within the particular ad hoc network and their uniqueness should be maintained even in situations where two or more networks, initially disjoint, merge together to form a single network. Due to the mobility and wireless properties of the nodes, network merger can occur anytime. 4.2. Ad hoc network at the edge of infra-structure network H1 | +---------------+ | Internet | +---------------+ * * * * GW1* * | GW2 | | ---N1 | / | | N4 | N2--- N5 | | N3-----------+ Fig. 1: Hybrid ad hoc network connected to Internet. Hybrid networks can be envisioned as an standalone network connected to the Internet via one or more Internet Gateways. These gateways are located between the two networks and are capable of providing globally routable addresses as well as bi-directional connectivity to the ad hoc nodes connected to them either directly (1-hop) or via one or more intermediate nodes. These gateways may either be fixed or mobile, single or multiple, equipped with one or more wired and/or wireless interfaces. Fig.1. shows an ad hoc network deployed at the edge of the Internet. Ad hoc nodes may use Internet gateway for global prefix allocation and globally routable address configuration. However, for such network sufficient but limited detail about Internet gateway(s) operation is required. Singh, et al. Expires September 7, 2006 [Page 8] Internet-Draft ADP March 2006 4.3. Temporarily hybrid ad hoc network Temporarily hybrid MANET scenario arises due to the situation where an ad hoc network may be sometimes stand-alone and sometimes connected to the Internet e.g. a car or subway network connected while parked or at station and disconnected otherwise. Problems related with this ad hoc network operation scenario are similar to those introduced in the above two scenarios. However, in this case, ad hoc nodes should detect the loss of reachability to the Internet and SHOULD maintain their allocated addresses for the lifetime which has been assigned during the autoconfiguration process. For local addresses, no such lifetime is necessary, but could anyway be assigned as a minimal protection against partitioning. 4.4. Network merger and partitioning By the nature of MANET, two or more ad hoc networks which are initially isolated, can merge together or a single ad hoc network can get partitioned into two or more separate networks, at any moment in time. As a consequence of network partitioning, some of the routes in MANET nodes become invalid and hence some nodes may become unreachable. It is desirable that network partitioning is detected due to reasons such as re-use of resources that were initially used by the outgoing nodes. Network merger can lead to duplication of addresses. Normally, once an address is allocated to a node, it continues using it and collaborating to detect and resolve duplicates in case its address is allocated to any other node. Since initially isolated networks had allocated addresses independent with each other, there remains some probability of more than one node using same address. Worst possible scenario can occur when number of address conflicts after merger are as many as number of nodes. This can happen if, for example, addresses were allocated within initially independent MANETs from the same address-range. Singh, et al. Expires September 7, 2006 [Page 9] Internet-Draft ADP March 2006 5. Goals Goals listed below are by no means exhaustive. Additional goals may be found necessary as the protocol design, implementation and deployment takes place. Below listed goals is an effort to give a bigger scope and as such may or may not fall within the scope of the AUTOCONF WG. These goals include: - As mentioned in the above sections, MANETs can be either standalone or connected to the Internet via one or more Internet gateways. MANET nodes MUST implement a mechanism to configure "local address(es)" when standalone. It MAY configure global address(es) when connected to the Internet. Nodes MUST ensure address uniqueness, explained under next bullet, before configuring them to their interfaces. It MAY be required that the configured global addresses are usable even after connectivity with the Internet is lost. - Each node MUST collaborate and resolve conflicts in case its address is duplicated to ensure uniqueness of the tentative address. If the particular address is being used by some other node, either one or both nodes MUST stop using the address. In this situation an alternative address MAY be generated. - As mentioned in section 4.4, network Merger is quite possible in MANETs. This may or may not result in multiple nodes using same address. However, it is desirable that each node runs mechanism to ensure the uniqueness of its current address-in-use. - Network partitioning is equally probably scenario in MANET and, is desirable that network partitioning is detected due to the reasons mentioned in section 4.4. Hence, MANET nodes MAY need a mechanism, either independent or integrated with the the main protocol, to detect network partitioning. - Protocol should be designed to avoid as many security pitfalls as can be avoided. This may involve using collaboration histories and out-of-band mechanisms requiring user interventions. Singh, et al. Expires September 7, 2006 [Page 10] Internet-Draft ADP March 2006 6. Security Considerations Since this document does not specify any protocol, no additional security vulnerabilities are created. However, given the importance of an aoutoconfiguration protocol as a bootstrapping process, it is important that protocols are designed trying to provide as much security as possible. Previous work on security in stand-alone ad hoc networks has shown that only a limited amount of security can be provided due to the absence of central entities or security infraestructures capable of validating the identity of nodes. In particular, given that the main goal of an autoconfiguration protocol is to provide nodes with IP addresses, special care needs to be taken to study the mapping of identities to addresses. In particular, this is of paramount importance in MANETs, in which reconfigurations and duplicates may occur. In the case of hybrid MANET scenarios, security remains being a difficult challenge, but an additional number of security services are likely to be provided including among others authentication and access control. Security mechanisms for autoconfiguration protocols SHOULD be designed so that they continue being effective even when parts of the network get temporarilly partition, and eventually lose Internet connectivity. Singh, et al. Expires September 7, 2006 [Page 11] Internet-Draft ADP March 2006 7. Acknowledgements The authors would like to acknowledge the following people for their technical contributions, discussions, reviews and comments : Ruffino Simone, Raquel Morera, Jari Arkko, Dave Thaler, Joe Macker, Christophe jelger, Alicia Trivino and Carlos J. Bernardos. Singh, et al. Expires September 7, 2006 [Page 11] Internet-Draft ADP March 2006 Appendix A. Normative References o [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. o [2] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. o [3] Engelstad, P., Tonnesen, A., Hafslund, A. and G. Egeland, "Internet Connectivity for Multi-Homed Proactive Ad Hoc Networks", First IEEE International Conference on Sensor and Ad hoc Communications and Networks, October 2004. o [4] Ryuji Wakikawa et. al. Global connectivity for IPv6 Mobile Ad Hoc Networks, IETF "draft-wakikawa-manet-globalv6-03.txt" o [5] Shubhranshu Singh, Kim, JH., Choi, YG., Kang, KL. and YS. Roh, "Mobile multi-gateway support for IPv6 mobile ad hoc networks" I-D draft-singh-manet-mmg-00.txt, June 2004. o [6] Perkins, C., Malinen, J., Wakikawa, R. and E. Belding-Royer, "IP Address Autoconfiguration for Ad Hoc Networks", I-D draft-perkins-manet-autoconf-01.txt, November 2001. o [7] Cha, H., Park, J. and H. Kim, "Extended Support for Global Connectivity for IPv6 Mobile Ad Hoc Networks", October 2003. o [8] Jeong, J., Park, J., Kim, H. and D. Kim, "Ad Hoc IP Address Autoconfiguration", I-D draft-jeong-adhoc-ip-addr-autoconf-02.txt, February 2004. o [9] Paakkonen, P., Rantonen, M. and J. Latvakoski, "IPv6 addressing in a heterogeneous MANET-network", I-D draft-paakkonen-addressing-htr-manet-00.txt, December 2003. o [10] Jelger, C., Noel, T. and A. Frey, "Gateway and address autoconfiguration for IPv6 adhoc networks", I-D draft-jelger-manet-gateway-autoconf-v6-02.txt, April 2004. o [11] Sun, Y. and E. Belding-Royer, "A study of dynamic addressing techniques in mobile ad hod networks", I-D Wireless communication and mobile computing, May 2004. o [12] C. Bernardos and M. Calderon, "Survey of IP address autoconfigura- tion mechnisms ofr MANETs," Internet Draft, draft-bernardos-manet- autoconf-survey-00.txt, July 2005, work in progress. Singh, et al. Expires September 7, 2006 [Page 12] Internet-Draft ADP March 2006 o [13] Engelstad, P., Tonnesen, A., Hafslund, A. and G. Egeland, "Internet Connectivity for Multi-Homed Proactive Ad Hoc Networks", First IEEE International Conference on Sensor and Ad hoc Communications and Networks, October 2004. Singh, et al. Expires September 7, 2006 [Page 13] Internet-Draft ADP March 2006 Authors' Addresses Shubhranshu Samsung AIT, Comm Lab Phone: +82 31 280 9569 Email: Shubranshu@gmail.com JaeHoon Kim Samsung AIT, Comm Lab Phone: +82 31 280 9532 Email: jaehoonk@samsung.com Charles E. Perkins Nokia Research Center, Communications Systems Laboratory Phone: +1 650 625 2986 Email: charliep@iprg.nokia.com Thomas Heide Clausen LIX, Ecole Polytechnique Phone: +33 6 6058 9349 Email: T.Clausen@computer.org URI: http://www.lix.polytechnique.fr/Labo/Thomas.Clausen/ Pedro M. Ruiz University of Murcia Phone: +34 968367646 Email: pedrom@dif.um.es Singh, et al. Expires September 7, 2006 [Page 14] Internet-Draft ADP March 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Singh, et al. Expires September 7, 2006 [Page 15]