MANET Autoconfiguration (AUTOCONF) S. Singh Internet-Draft J. Kim Expires: April 23, 2006 Samsung AIT, Comm Lab C. Perkins Nokia Research Center, Communications Systems Laboratory T. Clausen LIX, Ecole Polytechnique P. Ruiz University of Murcia October 24, 2005 Ad hoc network autoconfiguration: definition and problem statement draft-singh-autoconf-adp-02 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 August 5, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract A Mobile Ad Hoc NETwork (MANET) is formed by the association of Singh, et al. Expires August 5, 2005 [Page 1] Internet-Draft ADP February 2005 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 autoconfiguration mechanism. This document gives definition, problem statement and goals for ad hoc network autoconfiguration. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Singh, et al. Expires August 5, 2005 [Page 2] Internet-Draft ADP February 2005 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 tightly related to the issue of discovering Internet gateways and auto- configuring global addresses that are routable within the Internet. Usually, autoconfiguration of 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 standalone MANET, MANET local address, etc. This document provides definition of these terminologies, in addition to problem statement and goals for ad hoc network autoconfiguration. Singh, et al. Expires August 5, 2005 [Page 3] Internet-Draft ADP February 2005 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) Mobile Ad hoc Network (MANET) - A network formed dynamically in an arbitrary manner by a collection of mobile devices equipped with one or more wireless interfaces. Normally, nodes are characterized by random mobility and support multi-hop communication. Multi-hop property requires that each node should act as a "host" as well as a "router". Network topology is dynamic in nature due to the mobile nature of MANET nodes. 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 among MANET nodes as well as with the nodes located on the Internet. Internet gateway - An edge node connected to MANET as well as to the Internet and capable of providing global addresses and bidirectional connectivity to MANET nodes. Internet gateways should provide topologically correct IPv6 prefixes. Internet gateway mostly runs 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 - A network 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. Singh, et al. Expires August 5, 2005 [Page 4] Internet-Draft ADP February 2005 Hybrid ad hoc network - A network formed by a group of MANET nodes, capable of spontaneously forming a multi-hop ad hoc network, in which one or more of the nodes act as Internet Gateways providing access to other 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, this proccess happens as a consequence of the node mobility. 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 the mobility of the nodes. When this happens, some of the routes in MANET nodes become invalid hence some nodes may become unreachable. 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 August 5, 2005 [Page 5] Internet-Draft ADP February 2005 3. Assumptions o Routes between nodes in the ad hoc network MUST NOT leak into the Internet. 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 A gateway can be treated as a default router for the Internet. o A gateway SHOULD maintain active routes for all nodes within the MANET which are actively engaged in communications with their partners in 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 routing prefix, then those two gateways MUST coordinate their routing tables so that they exhibit equal reachability for all nodes within that routing prefix. o Multiple gateways may offer several different routing prefixes. A node may choose which gateway's 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. o When duplicate addresses are detected, the node which has had the address for the least amount of time MUST discontinue. Alternatively, BOTH nodes MUST discontinue using this address. Singh, et al. Expires August 5, 2005 [Page 6] Internet-Draft ADP February 2005 4. Problem statement Several specifications have been developed for address autoconfiguration in the traditional IP based network e.g. RFC 2462, RFC 2461, RFC 3315, etc. However, these specifications cannot be used as-is by the MANET nodes due to their unique properties. Unlike in traditional IP networks, each MANET node, besides being traffic end-point, normally expected to be capable of forwarding traffic traffic destined for other hosts i.e each ad hoc 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 all nodes in a 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. Transmissions which are otherwise not supposed to be forwarded by routers, such as limited broadcast and link-local multicast, are forwarded by the nodes in order to reach all the MANET nodes. In other words, nodes constituting an ad-hoc network do not share access to a single multicast-capable link for signaling. The address autoconfiguration related protocol specifications such as RFCs 2462, 2461, etc as used in traditional IP networks, 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 an standalone MANET 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 solutions in the MANET environment that can be used by MANET nodes constituting standalone networks as well as edge networks. However, the solutions should be designed with a minimal modification, if any, and should be compliant with the specifications that are widely used in the traditional IP networks. The 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. In this way, a single addressing solution is obtained, but just as within the Internet there are different kinds of addresses. However, there may be differences which are discovered as more development occurs towards the specification of the address autoconfiguration protocol. 4.1. Stand-alone ad hoc network Examples of standalone ad hoc networks are conference-room networks, Singh, et al. Expires August 5, 2005 [Page 7] Internet-Draft ADP February 2005 battlefield networks, surveillance networKs, etc. For these networks, IP address auto-configuration mechanism is needed. These addresses should be routable only within the particular ad hoc network and should be unique even in situations where two or more networks, initially disjoint, merge together to form a single network. Network merger can occur anytime and this makes the address uniqueness maintenance quite challenging in such situations. 4.2. Ad hoc network at the edge of infra-structure network H1 | +---------------+ | Internet | +---------------+ * * * * GW1* * | GW2 | | ---N1 | / | | N4 | N2--- N5 | | N3-----------N6 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 it either directly (1-hop) or via one or more intermediate nodes. These gateways may either be fixed or mobile, single or multiple, equipped with 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 configuration of globally routable addresses. However, it introduces issues such as how MANET nodes receive and/or Internet gateway provides globally routable prefixes, etc. Hence, for such network sufficient but limited detail about Internet gateway discovery and operation is required, along with an address autoconfiguration solution. Singh, et al. Expires August 5, 2005 [Page 8] Internet-Draft ADP February 2005 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. Basically, the problems in this case are similar to those introduced in the above two cases. However, in this case, ad hoc nodes should detect the lack 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. While network partitioning may not cause any problem in the MANET's operation, it may be needed that network partitioning is detected so that the resources (e.g. limited number of addressed) can be re-used among the nodes. Network merger imposes challenges to maintain the address uniqueness. Normally, once an address is allocated to a node, it continues using it and at the same time defending its own address from being allocated to any other node. However, 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 August 5, 2005 [Page 9] Internet-Draft ADP February 2005 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 also 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 perform duplicate address detection test on addresses before configuring them to their interfaces - ensuring uniqueness of the tentative addresses. If the particular address is being used by some other node, either or both nodes MUST not use the address. In this situation an alternative address MAY be generated and tested for uniqueness. - 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, each node SHOULD run a mechanism to ensure the uniqueness of its current address-in-use. - Network partitioning is equally probably scenario in MANET. While network partitioning may not cause any problem in the MANET's ongoing operation, it MAY be needed that network partitioning is detected so that the resources such as IP addresses can be re-used among the nodes. 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 August 5, 2005 [Page 10] Internet-Draft ADP February 2005 6. Security Considerations Since this document does not specify any protocol, no additional security vulnerabilities are created. However, experience with other address autoconfiguration protocols indicates that it is difficult to expect a very high degree of security. This is especially true in an ad hoc network using manet-local addresses, since it may be unfeasible to interact with any pre-existing security infrastructure. Nevertheless, the protocols 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 August 5, 2005 [Page 11] Internet-Draft ADP February 2005 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] 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 August 5, 2005 [Page 12] Internet-Draft ADP February 2005 Authors' Addresses Shubhranshu Singh Samsung AIT, Comm Lab, S. Korea Phone: +82 31 280 9569 Email: Shubhranshu@gmail.com JaeHoon Kim Samsung AIT, Comm Lab, S. Korea Phone: +82 31 280 9532 Email: jaehoonk@samsung.com Charles E. Perkins Nokia Research Center, Comm Systems Laboratory, U.S.A Phone: +1 650 625 2986 Email: charliep@iprg.nokia.com Thomas Heide Clausen LIX, Ecole Polytechnique, France 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, Spain Phone: +34 968367646 Email: pedrom@dif.um.es Singh, et al. Expires August 5, 2005 [Page 13] Internet-Draft ADP February 2005 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. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Singh, et al. Expires August 5, 2005 [Page 14]