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Versions: (draft-hui-6man-rpl-option) 00 01 02 03 04 05 06 RFC 6553

6MAN                                                              J. Hui
Internet-Draft                                     Arch Rock Corporation
Intended status: Standards Track                             JP. Vasseur
Expires: April 26, 2011                               Cisco Systems, Inc
                                                        October 23, 2010


    RPL Option for Carrying RPL Information in Data-Plane Datagrams
                     draft-ietf-6man-rpl-option-01

Abstract

   The RPL protocol requires data-plane datagrams to carry RPL routing
   information that is processed by RPL routers when forwarding those
   datagrams.  This document describes the RPL option for use within a
   RPL domain.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 26, 2011.

Copyright Notice

   Copyright (c) 2010 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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Format of the RPL Option . . . . . . . . . . . . . . . . . . .  5
   4.  RPL Router Behavior  . . . . . . . . . . . . . . . . . . . . .  7
   5.  RPL Border Router Behavior . . . . . . . . . . . . . . . . . .  8
   6.  Usage of the RPL Option  . . . . . . . . . . . . . . . . . . .  9
   7.  Protocol Constants . . . . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   11. Changes  . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     12.2. Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16

































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1.  Introduction

   RPL is a distance vector IPv6 routing protocol designed for low power
   and lossy networks [I-D.ietf-roll-rpl].  Such networks are typically
   constrained in energy and/or channel capacity.  To conserve precious
   resources, a routing protocol must generate control traffic
   sparingly.  However, this is at odds with the need to quickly
   propagate any new routing information to resolve routing
   inconsistencies quickly.

   To help minimize resource consumption, RPL uses a slow proactive
   process to construct and maintain a routing topology but a reactive
   and dynamic approach to resolving routing inconsistencies.  In the
   steady state, RPL maintains the routing topology using a low-rate
   beaconing process.  However, when RPL detects inconsistencies that
   may prevent proper datagram delivery, RPL temporarily increases the
   beacon rate to quickly resolve those inconsistencies.  Such a dynamic
   rate of control packets operation is governed by the use of dynamic
   timers also referred to as "trickle" timers and defined in
   [I-D.ietf-roll-trickle].  By contrast with other routing protocols
   such as OSPF ([RFC2328]), RPL detects routing inconsistencies using
   data-path verification, by including routing information within the
   datagram itself.  Data-path verification quickly detects and resolves
   inconsistencies when routes are needed by the data flow itself.  In
   doing so, repair mechanisms operate only as needed, allowing the
   control and data planes to operate on similar time scales.  The main
   motivation for data path verification in Low power and Lossy Networks
   (LLNs) is that control plane traffic should be carefully bounded with
   respect to the data traffic: there is no need to solve a routing
   issues (which may be temporary) in the absence of data traffic.

   The RPL protocol constructs a Directed Acyclic Graph (DAG) that
   attempts to minimize path costs to the DAG root according to a set of
   metric and objective functions.  There are circumstances where loops
   may occur, and RPL is designed to use a data-path loop detection
   method.  This is one of the known requirements of RPL and other data-
   path usage might be defined in the future.

   To that end, this document proposes a new IPv6 option called the RPL
   Option to be carried within the IPv6 Hop-by-Hop header.  The RPL
   Option is for use only within a RPL domain.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].




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2.  Overview

   Datagrams being forwarded within a RPL domain MUST include a RPL
   Option.  For datagrams sourced within a RPL domain, the RPL Option
   MAY be included in the datagram itself.  For datagrams sourced
   outside a RPL domain, IPv6-in-IPv6 tunneling, as specified in
   [RFC2473] MUST be used to include a RPL Option.  When forwarding the
   datagram, the router MUST prepend a new IPv6 header and IPv6 Hop-by-
   Hop Options header containing the RPL Option to the existing
   datagram.  Use of tunneling ensures that the datagram is delivered
   unmodified and that ICMP errors return to the RPL Option source
   rather than the source of the original datagram.

   To help avoid IP-layer fragmentation, the RPL Option has a maximum
   size of RPL_OPTION_MAX_SIZE octets and links within a RPL domain
   SHOULD have a MTU of at least 1280 + 44 (outer IP header, Hop-by-Hop
   Option header, Option header) + RPL_OPTION_MAX_SIZE + (additional
   extension headers or options needed within RPL domain).

































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3.  Format of the RPL Option

   The RPL option is carried in an IPv6 Hop-by-Hop Options header,
   immediately following the IPv6 header.  The RPL option has the
   following format:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                     |  Option Type  |  Opt Data Len |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |O|R|F|0|0|0|0|0| RPLInstanceID |          SenderRank           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         (sub-TLVs)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 1: RPL Option

   Option Type:  TBD

   Opt Data Len:

   Down 'O':  1-bit flag indicating whether the packet is expected to
         progress Up or Down.  A router sets the 'O' flag when the
         packet is expected to progress Down (using DAO routes), and
         clears it when forwarding toward the DODAG root (to a node with
         a lower rank).  A host or RPL leaf node MUST set the 'O' flag
         to 0.

   Rank-Error 'R':  1-bit flag indicating whether a rank error was
         detected.  A rank error is detected when there is a mismatch in
         the relative ranks and the direction as indicated in the 'O'
         bit.  A host or RPL leaf node MUST set the 'R' bit to 0.

   Forwarding-Error 'F':  1-bit flag indicating that this node can not
         forward the packet further towards the destination.  The 'F'
         bit might be set by a child node that does not have a route to
         destination for a packet with the Down 'O' bit set.  A host or
         RPL leaf node MUST set the 'F' bit to 0.

   RPLInstanceID:  8-bit field indicating the DODAG instance along which
         the packet is sent.

   SenderRank:  16-bit field set to zero by the source and to
         DAGRank(rank) by a router that forwards inside the RPL network.

   Values within the RPL option are expected to change en-route.  Nodes
   that do not understand the RPL option MUST discard the packet.  Thus,



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   according to [RFC2460] the two high order bits of the Option Type
   must be equal set to '01' and the third bit is equal to '1'.  The RPL
   Option Data Length is variable.

   The action taken by using the RPL Option and the potential set of
   sub-TLVs carried within the RPL Option MUST be specified by the RFC
   of the protocol that use that option.  No TLVs are currently defined.












































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4.  RPL Router Behavior

   Routers MUST include a RPL Option when forwarding datagrams that do
   not already contain a RPL Option.  If one does not already exist,
   routers MUST use IPv6-in-IPv6 tunneling, as specified in [RFC2473] to
   include a RPL Option in datagrams that are sourced by other nodes.
   This ensures that the original datagram is delivered unmodified.

   Performing IP-in-IP encapsulation may grow the datagram to a size
   larger than the IPv6 min MTU of 1280 octets.  To help avoid IP-layer
   fragmentation caused by IP-in-IP encapsulation, links within a RPL
   domain SHOULD be configured with a MTU of at least 1280 + 44 (outer
   IP header, Hop-by-Hop Option header, Option header) +
   RPL_OPTION_MAX_SIZE + (additional extension headers or options needed
   within RPL domain).




































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5.  RPL Border Router Behavior

   RPL Border Routers (referred to as LBRs in
   [I-D.ietf-roll-terminology]) are responsible for ensuring that a RPL
   Option is only used within a RPL domain.

   For datagrams entering the RPL domain, RPL Border Routers MUST drop
   received datagrams that contain a RPL Option in the IPv6 Extension
   headers.

   For datagrams exiting the RPL domain, RPL Border Routers MUST remove
   the RPL Option from the datagram and update the IPv6 Payload Length
   field accordingly.






































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6.  Usage of the RPL Option

   The RPL option is only for use within a RPL domain.  RPL routers MUST
   process and include the RPL option when forwarding datagrams to other
   nodes within the RPL domain.  Routers on the edge of a RPL domain
   MUST remove the RPL option when forwarding datagrams to nodes outside
   the RPL domain.












































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7.  Protocol Constants

   RPL_OPTION_MAX_SIZE 128
















































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8.  Acknowledgements

   The authors thank Richard Kelsey, Vishwas Manral, Erik Nordmark,
   Pascal Thubert, and Tim Winter, for their comments and suggestions
   that helped shape this document.














































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9.  IANA Considerations

   The RPL option requires an IPv6 Option Number.


   HEX         act  chg  rest
   ---         ---  ---  -----
     1          01    1  01011


   The first two bits indicate that the IPv6 node MUST discard the
   packet if it doesn't recognize the option type, and the third bit
   indicates that the Option Data may change en-route.

   This document also creates a new IANA registry for the sub-TLVs.  No
   sub-TLVs are defined in this specification.  The policy for this
   registry [RFC5226] is IETF Review.


































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10.  Security Considerations

   This option may be used a several potential attacks since routers may
   be flooded by bogus datagram containing the RPL option.  It is thus
   RECOMMENDED for routers to implement a rate limiter for datagrams
   using the RPL option.













































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11.  Changes

   (This section to be removed by the RFC editor.)

   Draft 01:

      - Specify that a node must discard the packet if it doesn't
      recognize the RPL option.

      - Include RPL loop detection bits in the base header such that an
      IPv6 Hop-by-Hop Option header with the minimal RPL option consumes
      only 8 octets.







































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12.  References

12.1.  Normative References

   [I-D.ietf-roll-rpl]
              Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
              Kelsey, R., Levis, P., Networks, D., Struik, R., and J.
              Vasseur, "RPL: IPv6 Routing Protocol for Low power and
              Lossy Networks", draft-ietf-roll-rpl-13 (work in
              progress), October 2010.

   [I-D.ietf-roll-trickle]
              Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
              "The Trickle Algorithm", draft-ietf-roll-trickle-04 (work
              in progress), August 2010.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, December 1998.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

12.2.  Informative References

   [I-D.ietf-roll-terminology]
              Vasseur, J., "Terminology in Low power And Lossy
              Networks", draft-ietf-roll-terminology-04 (work in
              progress), September 2010.














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Authors' Addresses

   Jonathan W. Hui
   Arch Rock Corporation
   501 2nd St. Ste. 410
   San Francisco, California  94107
   USA

   Phone: +415 692 0828
   Email: jhui@archrock.com


   JP Vasseur
   Cisco Systems, Inc
   11, Rue Camille Desmoulins
   Issy Les Moulineaux,   92782
   France

   Email: jpv@cisco.com
































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