Autoconf E. Baccelli, Ed. Internet-Draft INRIA Intended status: Informational M. Townsley, Ed. Expires: January 7, 2010 Cisco Systems July 6, 2009 IP Addressing Model in Ad Hoc Networks draft-baccelli-autoconf-adhoc-addr-model-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 January 7, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document describes a model for configuration of IP addresses and subnet prefixes on the interfaces of routers which connect to links Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 1] Internet-Draft Ad Hoc IP Addressing July 2009 with undetermined connectivity properties. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Applicability Statement . . . . . . . . . . . . . . . . . . . . 3 4. IP Subnet Prefix Configuration Policy . . . . . . . . . . . . . 3 5. IP Address Configuration Policy . . . . . . . . . . . . . . . . 4 6. Addressing Model . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. IPv4 Addressing Model . . . . . . . . . . . . . . . . . . . 4 6.2. IPv6 Addressing Model . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Appendix A. Open Issues . . . . . . . . . . . . . . . . . . . . . 5 Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 2] Internet-Draft Ad Hoc IP Addressing July 2009 1. Introduction The appropriate configuration (IP addresses and subnet prefixes) of a router's network interfaces is a pre-requisite to the correct functionning of routing protocols. Depending on the nature of the link to which an interface connects, assumptions can be made in terms of connectivity to other interfaces which ultimately affect the overall network topology. Different network topologies translate into different configurations of IP on a given interface, for example, whether two interfaces are configured to appear within the same subnet or not. Absent such connectivity assumptions, there is no de facto translation into a given interface configuration. This document proposes a model for configuration of IP addresses and subnet prefixes on routers' interfaces to links with undetermined connectivity properties. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 3. Applicability Statement The configuration proposed by this model is applicable to any router's interface. It specifies addresses and subnet prefixes to be configured on network interfaces. When assumptions can be made regarding the connectivity to other interfaces on the link, these SHOULD be considered when configuring subnet prefixes. 4. IP Subnet Prefix Configuration Policy If the link to which an interface connects enables no assumptions of connectivity to other interfaces, the only addresses which can be assumed "on link", are the address(es) of that interface itself. Subnet prefix configuration on such interfaces must thus not make any promises in terms of direct (one hop) IP connectivity to IP addresses other than that of the interface itself. This translates in the following policy: no two such interfaces in the network should be Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 3] Internet-Draft Ad Hoc IP Addressing July 2009 configured with the same subnet prefix. As communication is allowed between interfaces of different routers on the same link even if these interfaces are configured to appear within different subnets, IP packet exchange between routers on that link is still enabled. If on the contrary, assumptions can be made regarding connectivity to other interfaces on the link, these SHOULD be considered when configuring IP subnet prefixes, and the corresponding interfaces MAY be configured with the same subnet prefix. 5. IP Address Configuration Policy Routing protocols running on a router may exhibit different interface address uniqueness requirements: some have no such requirements, others, have requirements going from local uniqueness only, to uniqueness within the routing domain at least. Configuring an IP address that is unique within the routing domain satisfies the less stringent uniqueness requirements of local uniqueness, while also enabling protocols which have the most stringent requirements of uniqueness within the routing domain. This translates in the following policy: an IP address assigned to an interface that connects to a link with undetermined connectivity properties shall be unique at least within the routing domain. 6. Addressing Model Section 4 and Section 5 describe policies for IP address and subnet prefix configuration on an interface of a router, when that interface connects to a link. The following describes how these policies translate into practical address models, respectively for IPv4 and IPv6. 6.1. IPv4 Addressing Model In an IPv4 environment, the policies described in Section 4 and Section 5 translate as such: o An IP address configured on this interface should be unique, at least within the routing domain, and o A subnet prefix configured on this interface should be of length /32. Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 4] Internet-Draft Ad Hoc IP Addressing July 2009 6.2. IPv6 Addressing Model In an IPv6 environment, the policies described in Section 4 and Section 5 translate as such: o An IP address configured on this interface should be unique, at least within the routing domain, and o A subnet prefix configured on this interface should be of length /128. 7. IANA Considerations This document has no actions for IANA. 8. Security Considerations This document does currently not describe any security considerations. 9. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Appendix A. Open Issues The following issues were extensively discussed among the design team, without reaching a conclusion. MANET Link Model - no satisfying MANET link model was formulated to date. Use of Link Local Addresses - while the use of link local addresses on interfaces connecting to a MANET link is not prohibited, the semantics of "link local" in this context is yet to be defined, taking into account the unusual requirements that follow, concerning such addresses. These requirements include for example uniqueness within a scope spanning beyond a single IP hop. Global Uniqueness Requirements - it remains to be determined whether or not the scope of AUTOCONF includes applications other than routing protocols running on the router, which may communicate with outside the routing domain and which for that, require Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 5] Internet-Draft Ad Hoc IP Addressing July 2009 globally unique addresses. Appendix B. Contributors This document reflects discussions and contributions from several individuals including (in alphabetical order): Teco Boot: teco@inf-net.nl Ulrich Herberg: ulrich@herberg.name Thomas Narten: narten@us.ibm.com Charles Perkins: charliep@computer.org Authors' Addresses Emmanuel Baccelli INRIA Email: Emmanuel.Baccelli@inria.fr URI: http://www.emmanuelbaccelli.org/ Mark Townsley Cisco Systems Email: townsley@cisco.com Baccelli, Ed. & Townsley, Ed. Expires January 7, 2010 [Page 6]