[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

Network Working Group                                         T. Clausen
Internet-Draft                          LIX, Ecole Polytechnique, France
Intended status: Informational                          October 27, 2008
Expires: April 30, 2009


                          The MANET Link Type
                    draft-clausen-manet-linktype-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 April 30, 2009.

Abstract

   This document describes the link characteristics and properties for
   links over which MANET protocols are designed to operate.













Clausen                  Expires April 30, 2009                 [Page 1]


Internet-Draft               MANET Link Type                October 2008


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  The MANET Router . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  MANET Interfaces . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  MANET Network Dynamics . . . . . . . . . . . . . . . . . . . .  6
   6.  The MANET Link Type  . . . . . . . . . . . . . . . . . . . . .  8
     6.1.  Connectivity: Symmetry, Transitivity, Continouity ?  . . .  8
     6.2.  Subnet Model and Addresses . . . . . . . . . . . . . . . .  9
     6.3.  Multicast and Broadcast Scopes . . . . . . . . . . . . . . 10
   7.  The MANET Addressing Architecture  . . . . . . . . . . . . . . 11
     7.1.  MANET Interface Configuration  . . . . . . . . . . . . . . 12
     7.2.  MANET Addressing Architecture Characteristics  . . . . . . 12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   10. Informative References . . . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 14

































Clausen                  Expires April 30, 2009                 [Page 2]


Internet-Draft               MANET Link Type                October 2008


1.  Introduction

   A Mobile Ad hoc NETwork, or MANET, is commonly described as a loosely
   connected set of routers with no predetermined infrastructure and
   where the routers discover and maintain, even when faced with
   dynamically changing topologies, a routing structure.  Neither the
   set of routers in the MANET nor their connections to each other can
   be assumed to be pre-determined nor to be known in advance; either
   may change randomly over the lifetime of the MANET.

   MANETs are often constructed from routers using wireless broadcast
   interfaces, such as IEEE 802.11 interfaces in ad hoc mode, in order
   to establish connectivity among each other.  Other network interfaces
   and link types, such as Ethernet or point-top-point IP over IP
   tunnels, are occasionally present between routers in a MANET, and are
   then also used by MANET protocols, such as a MANET routing protocols
   (e.g.  [RFC3626], [RFC3561], [RFC4728], [RFC3684]) calculating
   routing paths.

   This presents MANET protocols with the challenge of operating not
   only over well known link types such as an Ethernet or a point-to-
   point IP over IP tunnel, but also to over links as formed over
   wireless broadcast interfaces.

   The purpose of this document is to describe a MANET Link Type which
   accommodates both, such that a protocol designed for the MANET Link
   Type will operate correctly both when presented with e.g. "an
   Ethernet" or with "a wireless broadcast interface".

2.  Terminology

   Neighbor -  a router B is a neighbor of a router A if B can receive
      communication directly from router A, without passing through any
      intermediates at the same layer (i.e. an IP router).

   Wireless broadcast interface -  a network interface where the medium
      supports true broadcast transmissions, and where link layer
      messages can be either multicast or unicast.  The transmission
      reachability is constrained by the radio range of the
      transmittter, which can be time-varying.

   Node -  any device (router or host) that implements IP.

   Router -  a node that forwards IP packets not explicitly addressed to
      itself.






Clausen                  Expires April 30, 2009                 [Page 3]


Internet-Draft               MANET Link Type                October 2008


   MANET Router -  a router which has, at least, one MANET interface
      towards a link of the MANET Link Type, as described in this
      document, and which is capable of ensuring correct operation over
      that link.

   Host -  any node that is not a router, i.e. a host does not forward
      packets addressed to others.  A Host runs a standard IP stack, and
      is subject to no MANET Link specific assumptions.

   MANET Link -  a link of the MANET Link type, as described in this
      document.

3.  The MANET Router

   The entities that are concerned by the MANET Link Type described in
   this document are MANET routers.  A MANET Router is a router which
   has at least one, but possibly more, MANET interfaces, and zero or
   more interfaces of other types and towards other networks, as
   illustrated in Figure 1.


            \ | /
             \|/      ------- MANET Interface(s)
              |
          +---+----+
          |        |
          | Manet  |
          | Router |
          |        |
          +--------+
            |    |
            |    |    ------- NON-MANET Interface(s)
        ----+    +----

                          Figure 1: MANET Router

   MANET interfaces are the only interfaces which are exposed to links
   of the MANET Link Type, as described in this document.  Protocols
   operating directly over these MANET interfaces are, therefore, the
   only protocols which are required to be aware of the characteristics
   of the MANET Link Type.

   This entails that protocols which are not intended to operate over
   MANET interfaces are not required to be able to handle the
   characteristics of the MANET Link Type.

   In particular, any node connected to a MANET router over an interface
   other than a MANET interface, will see the MANET router as it would



Clausen                  Expires April 30, 2009                 [Page 4]


Internet-Draft               MANET Link Type                October 2008


   see any other IP router.  For example, in Figure 2 the hosts
   connected to the MANET router via the Ethernet link will simply
   perceive an Ethernet link with hosts and a router, oblivious to if
   the router is a MANET router or not.

               \ | /
                \|/      ------- MANET Interface(s)
                 |
             +---+----+
             |        |
             | Manet  |
             | Router |
             |        |
             +--------+
                 |
                 |       ------- Ethernet  Interface
                 |
         +-----------------------+
         |       |       |       |
       +---+   +---+   +---+   +---+
       | H |   | H |   | H |   | H |
       +---+   +---+   +---+   +---+

             Figure 2: MANET Router with Hosts on an Ethernet

   Isolated by an IP hop, hosts on the Ethernet link in Figure 2 are not
   exposed to the particularities of the MANET Link Type - similarly to
   how, say, hosts on an Ethernet connected to an OSPF router with NBMA
   interfaces are not exposed to the particularities of the NBMA Link
   Type.

4.  MANET Interfaces

   An interface is, according to [RFC4862], "a node's attachment to a
   link", indicating that an interface is a unique point of attachment
   to a single link.  It therefore follows that a MANET interface is a
   MANET routers point of attachment to a MANET Link.

   A MANET interface is often a wireless broadcast interface, as
   illustrated in Figure 3, in which 5 MANET interfaces are connected to
   the same MANET link and form a simple MANET.  If these MANET
   interfaces are wireless broadcast interfaces, their transmission
   range is limited, as indicated.








Clausen                  Expires April 30, 2009                 [Page 5]


Internet-Draft               MANET Link Type                October 2008


            -------+-------     ---+-------             Transmission
     ------+------- -------+------- -------+-------         Ranges

          \|/     \|/     \|/     \|/     \|/
           |       |       |       |       |
         +-+-+   +-+-+   +-+-+   +-+-+   +-+-+
         | A |   | B |   | C |   | D |   | E |
         +---+   +---+   +---+   +---+   +---+

               Figure 3: MANET Interface Transmission Ranges

   In this simple network, a transmission by the node C reaches only
   nodes B and D on the MANET link, due to the limited transmission
   range of the wireless broadcast interface.  Similarly, a transmission
   from node B reaches only nodes A and C and a transmission by node D
   reaches only node E - the latter might be due to environmental
   interference or obstacles, transmission power levels or antenna
   properties of node C or D (e.g. directional antennas on either or
   both of C and D).

   Note that the "Ethernet-like" interface characteristics that are
   usually assumed, where all Ethernet interfaces on the same link can
   reach each other, is a special case of this; and an Ethernet
   interface would be a perfectly acceptable MANET interface.

   This example in Figure 3 exhibits some of the characteristics of a
   MANET Link: connectivity on a link can not be assumed to be
   symmetric, nor can it be assumed to be transitive.  These MANET Link
   Type characteristics are detailed in Section 6.

5.  MANET Network Dynamics

   In a MANET, the set of participating MANET routers may change,
   possibly frequently, over time, as can the relative position of the
   MANET routers change as the network evolves.  More specifically, the
   set of MANET interfaces attached to a given MANET Link may change
   over time, and a MANET interface may change its position on a MANET
   Link, which may change the set of neighbors of that MANET interface.
   The simple network in Figure 3 may evolve over time, as illustrated
   in Figure 4, where at time t1 node A disappears from the MANET Link
   and node C and D moves out of radio range from each other and are no
   longer able to communicate.  At time t2, node F appears on the MANET
   Link, at a position where nodes C and D are within its radio range.

   The set of MANET interfaces which can be reached by a transmission
   from any MANET interface on the MANET Link may therefore also change
   over time.  In particular, the ability for a MANET interface to
   receive a transmission from another MANET interface on the same MANET



Clausen                  Expires April 30, 2009                 [Page 6]


Internet-Draft               MANET Link Type                October 2008


   Link and at a given point in time does not necessarily indicate that
   such is also possible in the future.



            -------+-------     ---+-------
     ------+------- -------+------- -------+-------

          \|/     \|/     \|/     \|/     \|/
           |       |       |       |       |
         +-+-+   +-+-+   +-+-+   +-+-+   +-+-+          t0
         | A |   | B |   | C |   | D |   | E |
         +---+   +---+   +---+   +---+   +---+


            -------+-------     ---+-------
     ------+-------                 -------+-------

          \|/     \|/             \|/     \|/
           |       |               |       |
         +-+-+   +-+-+           +-+-+   +-+-+          t1
         | B |   | C |           | D |   | E |
         +---+   +---+           +---+   +---+


            -------+-------     ---+-------
     ------+------- -------+------- -------+-------

          \|/     \|/     \|/     \|/     \|/
           |       |       |       |       |
         +-+-+   +-+-+   +-+-+   +-+-+   +-+-+          t2
         | B |   | C |   | F |   | D |   | E |
         +---+   +---+   +---+   +---+   +---+

                     Figure 4: MANET Network Dynamics
















Clausen                  Expires April 30, 2009                 [Page 7]


Internet-Draft               MANET Link Type                October 2008


6.  The MANET Link Type

   [Thaler] enumerates a set of properties, which are commonly assumed
   by applications and upper layer protocols, and notes that these
   assumptions are becoming increasingly less true.  The MANET Link Type
   is an example of a Link Type which challenges these assumptions.

   The MANET Link Type characteristics can be summarized as follows:

   o  connectivity can not be assumed to be symmetric within a MANET
      Link;

   o  connectivity can not be assumed to be transitive within a MANET
      Link;

   o  connectivity can not be assumed to be continuous within a MANET
      Link;

   o  the point of attachment to a MANET Link determines the view of
      that MANET link;

   o  multicast and broadcast can not be assumed to work across a MANET
      Link;

   o  a subnet is smaller than a MANET Link;

   o  addresses can not be assumed to be part of an on-link subnet on a
      MANET Link.

   It is important to note that the MANET Link Type is non-prescriptive,
   i.e. it does not *require* a link to have these characteristics in
   order for MANET protocols to operate correctly over it, however
   protocols designed for the MANET Link Type are *required* to be able
   to operate correctly also when presented with these link
   characteristics.

   This, in particular, entails that for example an Ethernet would be
   perfectly acceptable as a MANET Link and that MANET protocols would
   operate correctly when presented with an Ethernet.

6.1.  Connectivity: Symmetry, Transitivity, Continouity ?

   As indicated in Section 4, MANET interfaces on a MANET Link may not
   all be neighbors, i.e. may not be able to communicate directly
   between each other without intermediate retransmissions,
   specifically:





Clausen                  Expires April 30, 2009                 [Page 8]


Internet-Draft               MANET Link Type                October 2008


   o  node A being a neighbor of node B does not necessarily imply that
      node B is also a neighbor of node A;

   o  node A being a neighbor of nodes B and C does not necessarily
      imply that nodes B and C are neighbors.

   Furthermore, as indicated in Section 5, neighbors may change over,
   specifically:

   o  the ability for a MANET interface to receive a transmission from
      another MANET interface on the same MANET Link and at a given
      point in time does not necessarily indicate that such is also
      possible in the future.

6.2.  Subnet Model and Addresses

   [Thaler] observes that "a subnet is smaller than, or equal to a
   link", specifically that "destinations with addresses in the same
   subnet can be reached with TTL (or Hop Count) = 1".  On a MANET Link,
   a transmission with TTL (or Hop Count) = 1 can be received only by
   MANET interfaces which are neighbors of the sending MANET interface.

   The first observation is, that "subnet", "reachability without
   decrementing TTL" and "addresses within a subnet" are intimately
   related, and assume that "all interfaces with addresses within the
   same subnet are neighbors".

            -------+-------     ---+-------             Transmission
     ------+------- -------+------- -------+-------         Ranges

          \|/     \|/     \|/     \|/     \|/
           |       |       |       |       |
         +-+-+   +-+-+   +-+-+   +-+-+   +-+-+
         | A |   | B |   | C |   | D |   | E |
         +---+   +---+   +---+   +---+   +---+

                     Figure 5: MANET Subnet Challenge

   Considering node C on the MANET Link as depicted in Figure 5, this
   router can reach the MANET interfaces of node B and D in a single
   transmission and with a TTL (or Hop Count) = 1.  Nodes B, C and D
   could, therefore, be candidates for belonging to the same subnet.
   However a transmission by node B can not reach node D without being
   retransmitted by node C and so a transmission from node B with a TTL
   (or Hop Count) = 1 will not reach node D. Furthermore, due to the
   limited transmission range of node D, node D can reach neither of
   nodes B and C -- and so, nodes B, C and D can not belong to the same
   subnet.



Clausen                  Expires April 30, 2009                 [Page 9]


Internet-Draft               MANET Link Type                October 2008


   This leads to the second observation, that the only set of addresses
   which on a MANET Link can be guaranteed reachable in a single
   transmission with TTL (or Hop count) = 1 are those of the
   transmitting interface.  The only addresses which can belong to the
   same subnet on a MANET Link are, therefore, the addresses assigned to
   the same MANET interface.

   While the MANET interfaces of nodes B and C in Figure 5 may not be
   configured with addresses from within the same subnet, these may
   still communicate e.g. as point-to-point links where the two
   endpoints have addresses from unrelated address spaces.

6.3.  Multicast and Broadcast Scopes

   IPv4 Limited Broadcast (255.255.255.255) and IPv4 and IPv6 Link Local
   Multicast (FFx2::) are specified to not be forwarded [RFC3927]
   [RFC4291] [RFC3330].  As a consequence, on a MANET Link:

   o  the scope within which a Limited Broadcast or a Link Local
      Multicast transmission can be received is limited to that of the
      transmitting MANET interface and its neighbors.

   In other words, the broadcast and link local multicast scope of a
   MANET interface on a MANET Link is the MANET interfaces which are
   within transmission range.  In figure Figure 6, the broadcast and
   multicast scope of node C is, as indicated, the MANET interfaces of
   nodes B and D; the broadcast and multicast scope of node D is the
   MANET interface of node E.

                                ---+-------               Multicast
                    -------+-------                         Scopes

          \|/     \|/     \|/     \|/     \|/
           |       |       |       |       |
         +-+-+   +-+-+   +-+-+   +-+-+   +-+-+
         | A |   | B |   | C |   | D |   | E |
         +---+   +---+   +---+   +---+   +---+

               Figure 6: MANET Broadcast and Multicast Scope

   Symmetrically, a broadcast or a link local multicast can be received
   by any MANET interface within transmission range of the transmitter,
   whether those are the receivers intended or not.  Due to the fact
   that connectivity can not be assumed to be symmetric, the transmitter
   may not a priori know which MANET interfaces have received the
   broadcast or link local multicast, nor can it be assumed that the
   recipients a posteriori can signal that they received the broadcast
   or link local multicast.



Clausen                  Expires April 30, 2009                [Page 10]


Internet-Draft               MANET Link Type                October 2008


7.  The MANET Addressing Architecture

   This section presents an addressing architecture model for MANETs,
   which preserves the integrity of the conventional IP addressing
   architecture while allowing for the particularities of the MANET Link
   Type.  In particular, the applications and protocols running on hosts
   are not exposed to a MANET Link.  Only MANET interfaces of MANET
   routers are required to be aware of the MANET Link Type, and to be
   configured according to the characteristics of the MANET Link Type.

   A MANET router is a router with at least one MANET interface towards
   a MANET Link and, possibly, with zero or more other interfaces
   towards other routers or hosts.  The MANET router may, as any router
   be delegated zero or more prefixes, which it may assign, integrally
   or as subnet prefixes, to any links of its non-MANET interfaces,
   which are configured accordingly.  Hosts and routers on these non-
   MANET interfaces may be assigned addresses from within these prefixes
   according to the address (auto)configuration mechanisms governing
   these (non-MANET) links, such as [RFC4862] and [RFC2131].

   Considering the example in Figure 7, the MANET router is delegated
   the prefix p::/48.  Subnet-prefixes p:1::/62, p:2::/62 and p:3::/63
   from p::/48 are derived and assigned to the non-MANET links.
   Interfaces on these links are configured with addresses from within
   the subnet prefix of that link, as usual.

                                                                      M
                                                                      A
                                \ | /                                 N
                                 \|/      ------- MANET Interface(s)  E
                                  |                                   T
                            +-  --+---  -+
                            |            |
                                Manet    | p::/48
   .........................|   Router   |..............................
                            |            |
                            +-  ------  -+                            N
      p:1::/62               |    |     |              p:3::/62       o
     +-------+-------+-------+    |     +-------+-------+-------+     n
     |       |       |       |    |     |       |       |       |     |
   +---+   +---+   +---+   +---+  |   +---+   +---+   +---+   +---+   M
   | H |   | H |   | H |   | H |  |   | H |   | H |   | H |   | H |   A
   +---+   +---+   +---+   +---+  |   +---+   +---+   +---+   +---+   N
                                  |                                   E
                     -------------+----------------                   T
                               p:2::/62





Clausen                  Expires April 30, 2009                [Page 11]


Internet-Draft               MANET Link Type                October 2008


                Figure 7: MANET Router and Prefixes Example

   The configuration of MANET interface(s) of the MANET router requires
   special attention, and is detailed in Section 7.1.

7.1.  MANET Interface Configuration

   As described in Section 6.2, on a MANET Link the only addresses which
   can be guaranteed to be reachable with TTL (or Hop Count) = 1, and
   therefore can be admitted to be within the same subnet, are the
   addresses assigned to the sending MANET interface.  Consequently,
   MANET interfaces must be configured such that:

   o  no two MANET interfaces appear within the same subnet, i.e. with
      the same prefix and prefix length.

   This can be, and is commonly, accomplished by configuring MANET
   interfaces with a /32 (IPv4) or a /128 (IPv6) address, e.g. as an
   unnumbered interface, borrowing a single IP address from a non-MANET
   interface of the MANET router.

   It is worth noting that prefix lengths shorter than /128 (IPv6) or
   /32 (IPv4) are possible on MANET interfaces, as long as the prefixes
   are unique to a single MANET interface.  Note that the above
   statements are not an exception, but simply a clarification that
   MANET are no different from other networks in this respect.

7.2.  MANET Addressing Architecture Characteristics

   The MANET addressing architecture presented in this section makes a
   clear separation between the role of MANET router and host in a
   MANET, recognizing that:

   o  MANET Link Type characteristics are only exposed to MANET
      interfaces of MANET-aware routers, running appropriate protocols;

   o  routers and hosts, and more generally networks/subnets, on non-
      MANET interface(s) are not subject to the particularities of the
      MANET Link Type but are isolated herefrom by an IP hop;

   o  applications and protocols on hosts and routers, and more
      generally networks/subnets, on non-MANET interfaces run
      unmodified.

   Note that this addressing architecture is similar to how routing in
   the existing Internet is structured.  Routers run their routing
   protocol over router interconnects with various characteristics to
   which only the routing protocols are privy.  On the other hand, hosts



Clausen                  Expires April 30, 2009                [Page 12]


Internet-Draft               MANET Link Type                October 2008


   connect to routers over interfaces with well-defined characteristics.

8.  Security Considerations

   This document does not currently present any security considerations.

9.  IANA Considerations

   This document does not have any IANA actions

10.  Informative References

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC3330]  IANA, IANA., "Special-Use IPv4 Addresses", RFC 3330,
              September 2002.

   [RFC3561]  Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
              Demand Distance Vector (AODV) Routing", RFC 3561,
              July 2003.

   [RFC3626]  Clausen, T. and P. Jacquet, "The Optimized Link State
              Routing Protocol", RFC 3626, October 2003.

   [RFC3684]  Ogier, R., Templin, f., and M. Lewis, "Topology
              Dissemination Based on Reverse-Path Forwarding", RFC 3684,
              February 2004.

   [RFC4728]  Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
              Routing Protocol (DSR) for Mobile Ad Hoc Networks for
              IPv4", RFC 4728, February 2007.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              May 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4862]  Narten, T., Thomson, S., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [Thaler]   Thaler, D., "Evolution of the IP Model", Work In
              Progress draft-thaler-ip-model-evolution-01.txt,
              July 2008.





Clausen                  Expires April 30, 2009                [Page 13]


Internet-Draft               MANET Link Type                October 2008


Appendix A.  Acknowledgments

   This document is greatly inspired from discussions with Dave Thaler
   (Microsoft), Jari Arkko (Ericsson), Mark Townsley (Cisco), Ian
   Chakeres (Motorola).

   Christopher Dearlove (BAE Systems) and Emmanuel Baccelli (INRIA) both
   provided reviews and insightful comments on early iterations of this
   text.

Author's Address

   Thomas Heide Clausen
   LIX, Ecole Polytechnique, France

   Phone: +33 6 6058 9349
   EMail: T.Clausen@computer.org
   URI:   http://www.thomasclausen.org/

































Clausen                  Expires April 30, 2009                [Page 14]


Internet-Draft               MANET Link Type                October 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.

   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, THE IETF TRUST 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.

Intellectual Property

   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.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.












Clausen                  Expires April 30, 2009                [Page 15]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/