MANET Autoconfiguration (AUTOCONF) S. Singh Internet-Draft A. Bhatia Intended status: Informational Samsung India Expires: December 9, 2008 June 07, 2008 IP Link Model for MANET draft-singh-autoconf-linkmodel-00 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 December 9, 2008. Abstract The stateless as well as stateful address autoconfiguration Protocols, as specified by the IETF, supports links with different properties. However, often these protocols assume specific properties and behavior from the underlying link type, as for example link-layer multicasting. The solution designer and implementers consider these specific link behavior while designing or extending these protocols. IETF Autoconf WG goal is to standardize mechanism for address autoconfiguration of nodes in a Mobile Ad Hoc Network (MANET). Before designing such protocol, the link model for MANET as seen by the IP needs to be clearly understood . However, there is no document describing IP link model for MANET. This document is an attempt to bridge this gap. Singh & Bhatia Expires December 9, 2008 [Page 1] Internet-Draft IP Link Model for MANET June 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IP Link Model for MANET . . . . . . . . . . . . . . . . . . . . 4 3.1. Multi-access Link Model . . . . . . . . . . . . . . . . . . 4 3.2. Sub-IP Link Model . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Singh & Bhatia Expires December 9, 2008 [Page 2] Internet-Draft IP Link Model for MANET June 2008 1. Introduction The stateless as well as stateful address autoconfiguration Protocols [ADDRCONF],[DHCP] supports links with different properties. However, often these protocols assume specific properties and behavior from the underlying link type, as for example link-layer multicasting. The solution designer and implementers consider these specific link behavior while designing or extending these protocols. IETF Autoconf WG goal is to standardize mechanism for address autoconfiguration of nodes in a Mobile Ad Hoc Network (MANET). Before designing such protocol, the link model for MANET as seen by the IP needs to be clearly understood. However, there is no document describing IP link model for MANET. This document is an attempt to bridge the gap. Section 2 provides terminologies which are used in this document. Section 3.1 details IP multi-access link model for MANET. Section 3.2 details sub-IP link model for MANET. 2. Terminology Node a device that implements IP. Link a communication facility or medium over which nodes can communicate at the link layer, i.e., the layer immediately below IP. Examples are Ethernets (simple or bridged), PPP links, X.25, Frame Relay, or ATM networks as well as Internet-layer (or higher- layer) "tunnels", such as tunnels over IPv4 or IPv6 itself. non-broadcast multi-access (NBMA) a link to which more than two interfaces can attach, but that does not support a native form of multicast or broadcast (e.g., X.25, ATM, frame relay, etc.). shared media a link that allows direct communication among a number of nodes, but attached nodes are configured in such a way that they do not have complete prefix information for all on-link destinations. That is, at the IP level, nodes on the same link may not know that they are neighbors; by default, they communicate through a router. Router a node that forwards IP packets not explicitly addressed to itself. MANET Router A router that participates in MANET routing protocols such As [AODV],[OLSR]. Singh & Bhatia Expires December 9, 2008 [Page 3] Internet-Draft IP Link Model for MANET June 2008 Subnet generally refer to a topological area that uses the same address prefix, where that prefix is not further subdivided except into individual addresses. 3. IP Link Model for MANET This section provides detail of link model for MANET as seen by the IP. Two possible models have been explained: multi-access link model and sub-IP link model. Multi access link model is commonly assumed by the MANET community while designing and implementing MANET protocols. The sub-IP link model came into discussion multiple times in the Autoconf WG as an alternative approach. 3.1. Multi-access Link Model In this model there are forwarding nodes called MANET Routers which participate in the MANET routing protocol e.g. [AODV],[OLSR]. There may be non-MANET nodes (clients or routers) attached to non- MANET interface e.g., via wired Ethernet. Collection of these MANET routers constitute a Mobile Ad Hoc Network (MANET). MANET is bounded by the MANET Border Router and is considered as a site with multiple subnets where subnet is a topological area that uses the same address prefix. From the IP perspective, MANET is a cloud of links where link is considered as a topological area bounded by routers that decrement IPv4 TTL or IPv6 Hop Limit when forwarding IP packets. MANET nodes are often wireless and mobile. Besides, nodes may join, leave and form network in an ah hoc manner. The set of all the nodes on the same link receive the link-local messages and are able to communicate with each other at the link layer. This implies that the MANET links have the same properties as shared media [SH-MEDIA]. Moreover, asymmetric and non-transitive wireless media characteristics result in dynamic link i.e. the set of nodes on a particular link as well as the number of links changes with time. Here, set of one hop neighbors and on-link nodes are not equivalent because some nodes in a one hop neighbor set may not be able to directly communicate due to non transitive physical link characteristics. Hence the set of on-link nodes is always subset of one hop neighbor set. In MANET, some of the protocols may require MANET wide communication, For example Duplicate Address Detection. Since multi access link model does not consider whole MANET as one link, the protocol developer or designer has to provide some solution for MANET wide communication. How to perform site scoped multicast communication is out of scope of this document and should be considered during the solution space discussion. Singh & Bhatia Expires December 9, 2008 [Page 4] Internet-Draft IP Link Model for MANET June 2008 As discussed before, in this model set of on-link nodes may not be same as set of neighbor nodes. To have these two sets equivalent, either underlying physical link can be enhanced for transitiveness through abstraction layer or all the on-link nodes should have the same neighbor cache entries. Also, issues with the shared media and asymmetric reachanbility needs to be considered while designing any solution with this model assumption. 3.2. Sub-IP Link Model In this model, MANET is a multi hop network bounded by MANET routers and from the IP perspective considered as a single link. With this link model MANET may be considered as NBMA network and may be used to emulate the services provided to the IPv6 layer by conventional broadcast media such as Ethernet. Since link is considered as a topological area bounded by routers that decrement IPv4 TTL or IPv6 Hop Limit when forwarding IP packets, therefore in order for IP to see MANET as single link, the forwarding plane needs to work below IP and MANET routers are required to be configured to operate at the sub IP layer. MANET nodes are often wireless and mobile but these characteristics does not change the set of nodes seen by IP on a particular link. IEEE 802.11s is an example of sub-IP model where multi-hop forwarding is done at L2. However this approach does not address the scenario where MANET consists of heterogeneous access technologies i.e. this approach is suitable only for network with homogeneous link technology. Besides, this model may have performance issues if IP protocols make heavy use of link local multicasting. This model could also be realized by providing sub-IP abstraction layer such that IP is unaware of Ad-hoc, wireless and mobile characteristics of MANET. One possible concern with this approach is loss of end to end transparency due to link enhancement provided by IP sub layer. 4. Security Considerations TBD 5. Normative References [ADDRCONF] Singh & Bhatia Expires December 9, 2008 [Page 5] Internet-Draft IP Link Model for MANET June 2008 Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862", Sep 2007. [DHCP] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6), RFC 3315", July 2003. [AODV] Perkins, C., Belding Royer, E., and S. Das, "Ad hoc On- Demand Distance Vector (AODV) Routing, RFC 3561", July 2003. [OLSR] Clausen, T. and P. Jacquet, "RFC 3626 - Optimized Link State Routing Protocol (OLSR), RFC 3626", Oct 2003. [NDP] Narten, T., "Neighbor Discovery for IP version 6 (IPv6), RFC 4861", Sep 2007. [MANET-Arch] Chakeres, I. and J. Macker, "Mobile Ad hoc Network Architecture", IETF Draft", Dec 2007. [SH-MEDIA] Barden, B., Postel, J., and Y. Rekhter, "Internet Architecture Extensions for Shared Media", RFC 1620", May 1994. Authors' Addresses Shubhranshu Singh Samssung India Bangalore, India Email: Shubranshu@gmail.com Ashutosh Bhatia Samsung India Bangalore, India Email: Ashutosh.bhatia.iisc@gmail.com Singh & Bhatia Expires December 9, 2008 [Page 6] Internet-Draft IP Link Model for MANET June 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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