IETF AUTOCONF Shubhranshu Singh Internet-Draft JaeHoon Kim Expires:April 07, 2006 SAMSUNG AIT Charles E. Perkins Nokia Research Center Pedro M. Ruiz University of Murcia Thomas Clausen Ecole polytechnique October 06, 2005 Ad hoc network autoconfiguration: terminology and problem statement draft-singh-autoconf-adp-01 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. The autonomous nature of these networks requires the existence of an autoconfiguration mechanism. This document explains terminologies, problem statement and solution requirements 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 . . . . . . . . . . . . 8 4.4 Dealing with network mergers and partitions . . . . . . . . 9 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 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 networks (e.g. Internet) some of them might act as gateways towards those networks. There are a number of solutions on interconnecting ad hoc networks to 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 ad hoc network autoconfiguration related terminologies such as standalone MANET, MANET local addresses, etc. This document provides definition of such terminologies, in addition to problem statement and solution requirements for address autoconfiguration in MANET. 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 by a set of mobile devices equipped with one or more wireless interfaces. Nodes are characterized by random mobility and run ad hoc routing protocols for multi-hop communication. MANET Node - A device with one or more wireless interfaces and associated IPv address(es) which is used by the MANET routing protocol in use. MANET local address - An IP address configured on a MANET node, which is 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 IPv4 or IPv6 address configured on a MANET node, which is valid for communication with the nodes located in the Internet. These addresses can also be used for communication with nodes within the MANET. Internet gateway - A node connected to ad hoc network as well as to the Internet and capable of providing global addressing and bidirectional connectivity to MANET nodes. Internet gateways should provide topologically correct IPv6 prefixes. This process can be done in a reactive, proactive or hybrid manner. 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 consisting of a group of MANET nodes capable of spontaneously creating a multi-hop ad hoc network without any 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 IP networks. They can be envisioned as a standalone MANET with one or more Internet Gateways taking part both in the MANET and in the external network. 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 mobility of the nodes. Network partitioning - The process by which an ad hoc network (either standalone or hybrid) which was previously connected, 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 ad hoc nodes detect the merger of two or more initially isolated MANETs. Network partition detection - The process by which ad hoc nodes detect the partition of a single MANET into two or more networks. 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 There are Specifications for address autoconfiguration in the traditional IPv6 networks e.g. RFC 2462,RFC 2461, etc. However, due to the challenges presented by MANET (as defined and understood by the IETF MANET WG), these specifications need to be extended for MANET environment. Unlike in the traditional IP networks, each ad hoc node, besides being traffic end-point, should be capable of forwarding 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. 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, should be 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. Many protocol specifications used in the traditional IP networks e.g. RFCs 2462, 2461 etc. do, however, assume that subnet-local signals (e.g. link-local multicast signal) are received by each of the hosts on the particular subnet without being forwarded by the routers defining the subnet boundary. There is a growing requirement for address autoconfiguration solutions in the MANET environment - to be used by the ad hoc nodes constituting standalone networks as well as edge networks. However, the solutions should be designed with a minimal modification and should be compliant with the specifications that are widely used in the traditional IP networks. 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. 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. Some parallels can be drawn between the "manet local" addressing and the "zeroconf" solution devised within the IETF working group of the same name. 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, battlefield networks, surveillance networKs, etc. For these networks, IPv4 and/or IPv6 address auto-configuration mechanism is needed. These addresses should be routable only within the particular ad hoc Singh, et al. Expires August 5, 2005 [Page 7] Internet-Draft ADP February 2005 network and should be unique even in situations where two or more networks, initially isolated, merge together to form a single network. Network merger can occur anytime and makes the address uniqueness maintenance quite challenging in such situations. 4.2 Ad hoc network at the edge of infra-structure network Fig.1. shows an ad hoc network deployed at the edge of the Internet. 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 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. 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. 4.3 Temporarily hybrid ad hoc network Temporarily hybrid ad hoc network scenario arise due to the situation where an ad hoc network may be sometimes stand-alone and sometimes Singh, et al. Expires August 5, 2005 [Page 8] Internet-Draft ADP February 2005 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 Dealing with network merges and partitions 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 severe 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 introduces 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 addresses from being allocated to any other node. However, since initially isolated ad hoc networks allocates addresses independent with each other, there remains some probability of more than one node using same address once two/more independent ad hoc networks merge. Singh, et al. Expires August 5, 2005 [Page 9] Internet-Draft ADP February 2005 5. Requirements In order to offer a lightweight but interoperable auto-configuration mechanism a number of requirements SHOULD be satisfied. These requirements include: Extensibility - The mechanism SHOULD be able to accomodate future extensions and optimizations. Efficiency - Given that network resources tend to be scarce in MANETs, autoconfiguration mechanisms SHOULD be lightweight in nature, and avoid making an excessive use of the network resources. Independence from ad hoc routing protocols - Autoconfiguration mechanisms SHOULD be able to operate with different proactive and reactive routing protocols. Interoperable with fixed IP networks - When there are one or more Internet gateways within a MANET, the address autoconfiguration approach should provide global addresses to MANET nodes in such a way that they MUST be able to interoperate with any IP host in the Internet, using standard protocols. Resilience and robustness - Given the dynamic nature of MANETs, autoconfiguration mechanisms SHOULD be resilient and roubust to packet losses, network partitions, network merges as well as disconnections from fixed IP networks or Internet Gateways. Validity both for IPv4 and IPv6 - Autoconfiguration mechanisms SHOULD be capable of working both for IPV4 and IPv6 autoconfiguration. Scalable - MANET autoconfiguration protocols should avoid increasing congestion in the MANET as the number of MANET nodes increases, or as they travel at higher speeds, or as more communication partners launch applications within the ad hoc network, or as the frequency of network partitions increases. Simplicity - Autoconfiguration mechanisms should be easy to test and deploy. 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 Samsung AIT, Comm & Network Lab Phone: +82 31 280 9569 Email: Shubhranshu@gmail.com JaeHoon Kim Samsung AIT Comm & Network 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 Pedro M. Ruiz University of Murcia Dept. Information and Communications Eng. Facultad de Informatica Campus de Espinardo s/n, Spain Phone: +34 968367646 Email: pedrom@dif.um.es 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/ 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. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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