Autoconf                                                E. Baccelli, Ed.
Internet-Draft                                                     INRIA
Intended status: Informational                          M. Townsley, Ed.
Expires: January 11, 2010                                  Cisco Systems
                                                           July 10, 2009


                 IP Addressing Model in Ad Hoc Networks
              draft-baccelli-autoconf-adhoc-addr-model-01

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Abstract

   This document describes a model for configuration of IP addresses and
   subnet prefixes on the interfaces of routers which connect to links



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   with undetermined connectivity properties.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Applicability Statement . . . . . . . . . . . . . . . . . . . . 3
   4.  IP Subnet Prefix Configuration  . . . . . . . . . . . . . . . . 3
   5.  IP Address Configuration  . . . . . . . . . . . . . . . . . . . 4
   6.  Addressing Model  . . . . . . . . . . . . . . . . . . . . . . . 4
     6.1.  IPv4 Model  . . . . . . . . . . . . . . . . . . . . . . . . 4
     6.2.  IPv6 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
































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1.  Introduction

   The appropriate configuration (IP addresses and subnet prefixes) of a
   router's network interfaces is a prerequisite to the correct
   functioning 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 or not two interfaces are configured to appear
   within the same subnet.

   Absent such connectivity assumptions, there is no canonical
   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 more specific 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

   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



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   configured with the same subnet prefix.

   As communication is allowed between interfaces of different routers
   on a 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

   Routing protocols running on a router may exhibit different
   requirements for uniqueness of interface addresses; some have no such
   requirements, others have requirements ranging 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 should be unique at least within the routing domain.


6.  Addressing Model

   Section 4 and Section 5 describe principles for IP address and subnet
   prefix configuration on an interface of a router, when that interface
   connects to a link with undetermined connectivity properties.  The
   following describes a practical translation for these principles,
   respectively for IPv4 and IPv6.

6.1.  IPv4 Model

   For IPv4, the principles 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.




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6.2.  IPv6 Model

   For IPv6, the principles 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.  Lacking a better definition so far, a MANET link is: a link
      with undetermined connectivity properties.

   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.







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   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
      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

















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