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Versions: (draft-goyal-roll-p2p-measurement) 00 01 02 03 04 05 06 07 08 10 RFC 6998

Internet Engineering Task Force                            M. Goyal, Ed.
Internet-Draft                                   University of Wisconsin
Intended status: Experimental                                  Milwaukee
Expires: October 3, 2013                                     E. Baccelli
                                                                   INRIA
                                                               A. Brandt
                                                           Sigma Designs
                                                             J. Martocci
                                                        Johnson Controls
                                                           April 1, 2013


A Mechanism to Measure the Routing Metrics along a Point-to-point Route
                    in a Low Power and Lossy Network
                   draft-ietf-roll-p2p-measurement-10

Abstract

   This document specifies a mechanism that enables an RPL router to
   measure the aggregated values of given routing metrics along an
   existing route towards another RPL router, thereby allowing the
   router to decide if it wants to initiate the discovery of a better
   route.

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).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on October 3, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Measurement Object (MO)  . . . . . . . . . . . . . . . . .  6
     3.1.  Format of the base MO  . . . . . . . . . . . . . . . . . .  6
     3.2.  Secure MO  . . . . . . . . . . . . . . . . . . . . . . . . 11
   4.  Originating a Measurement Request  . . . . . . . . . . . . . . 11
     4.1.  When Measuring A Hop-by-hop Route with a Global
           RPLInstanceID  . . . . . . . . . . . . . . . . . . . . . . 12
     4.2.  When Measuring A Hop-by-hop Route with a Local
           RPLInstanceID With Route Accumulation Off  . . . . . . . . 13
     4.3.  When Measuring A Hop-by-hop Route with a Local
           RPLInstanceID With Route Accumulation On . . . . . . . . . 14
     4.4.  When Measuring A Source Route  . . . . . . . . . . . . . . 16
   5.  Processing a Measurement Request at an Intermediate Point  . . 17
     5.1.  When Measuring A Hop-by-hop Route with a Global
           RPLInstanceID  . . . . . . . . . . . . . . . . . . . . . . 18
     5.2.  When Measuring A Hop-by-hop Route with a Local
           RPLInstanceID With Route Accumulation Off  . . . . . . . . 19
     5.3.  When Measuring A Hop-by-hop Route with a Local
           RPLInstanceID With Route Accumulation On . . . . . . . . . 20
     5.4.  When Measuring A Source Route  . . . . . . . . . . . . . . 21
     5.5.  Final Processing . . . . . . . . . . . . . . . . . . . . . 21
   6.  Processing a Measurement Request at the End Point  . . . . . . 22
     6.1.  Generating the Measurement Reply . . . . . . . . . . . . . 23
   7.  Processing a Measurement Reply at the Start Point  . . . . . . 23
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 26
     11.2. Informative References . . . . . . . . . . . . . . . . . . 27
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27







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1.  Introduction

   Point to point (P2P) communication between arbitrary routers in a Low
   power and Lossy Network (LLN) is a key requirement for many
   applications [RFC5826][RFC5867].  The IPv6 Routing Protocol for LLNs
   (RPL) [RFC6550] constrains the LLN topology to a Directed Acyclic
   Graph (DAG) built to optimize the routing costs to reach the DAG's
   root.  The P2P routing functionality, available under RPL, has the
   following key limitations:

   o  The P2P routes are restricted to use the DAG links only.  Such P2P
      routes may potentially be suboptimal and may lead to traffic
      congestion near the DAG root.

   o  RPL is a proactive routing protocol and hence requires all P2P
      routes to be established ahead of the time they are used.  Many
      LLN applications require the ability to establish P2P routes "on
      demand".

   To ameliorate situations where the core RPL's P2P routing
   functionality does not meet the application requirements
   [I-D.ietf-roll-p2p-rpl] describes P2P-RPL, an extension to core RPL.
   P2P-RPL provides a reactive mechanism to discover P2P routes that
   meet the specified routing constraints [RFC6551].  In some cases, the
   application requirements or the LLN's topological features allow a
   router to infer these routing constraints implicitly.  For example,
   the application may require the end-to-end loss rate and/or latency
   along the route to be below certain thresholds or the LLN topology
   may be such that a router can safely assume its destination to be
   less than a certain number of hops away from itself.

   When the existing routes are deemed unsatisfactory but the router
   does not implicitly know the routing constraints to be used in P2P-
   RPL route discovery, it may be necessary for the router to measure
   the aggregated values of the routing metrics along the existing
   route.  This knowledge will allow the router to frame reasonable
   routing constraints to discover a better route using P2P-RPL.  For
   example, if the router determines the aggregate ETX (Expected Number
   of Transmissions) [RFC6551] along an existing route to be "x", it can
   use "ETX < x*y", where y is a certain fraction, as the routing
   constraint for use in P2P-RPL route discovery.  Note that it is
   important that the routing constraints not be overly strict;
   otherwise, the P2P-RPL route discovery may fail even though a route
   exists that is much better than the one currently being used.

   This document specifies a mechanism that enables an RPL router to
   measure the aggregated values of the routing metrics along an
   existing route to another RPL router in an LLN, thereby allowing the



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   router to decide if it wants to discover a better route using P2P-RPL
   and determine the routing constraints to be used for this purpose.
   Thus, the utility of this mechanism is dependent on the existence of
   P2P-RPL, which is targeting publication as an Experimental RFC.  It
   makes sense, therefore, for this document also to target publication
   as an Experimental RFC.  The hope is that experiments with P2P-RPL
   and the mechanism defined in this document will result in feedback on
   the utility and benefits of this document and it will be revised and
   progressed on the Standards Track based on this feedback.

1.1.  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
   [RFC2119].

   This document uses terminology from [RFC6550],
   [I-D.ietf-roll-terminology] and [I-D.ietf-roll-p2p-rpl].
   Additionally, this document defines the following terms.

   Start Point: The Start Point refers to the RPL router that initiates
   the measurement process defined in this document and is the start
   point of the P2P route being measured.

   End Point: The End Point refers to the RPL router at the end point of
   the P2P route being measured.

   Intermediate Point: An RPL router, other than the Start Point and the
   End Point, on the P2P route being measured.

   The following terms, already defined in [I-D.ietf-roll-p2p-rpl], have
   been redefined in this document in the following manner.

   Forward direction: The direction from the Start Point to the End
   Point.

   Reverse direction: The direction from the End Point to the Start
   Point.


2.  Overview

   The mechanism described in this document can be used by a Start Point
   in an LLN to measure the aggregated values of selected routing
   metrics along a P2P route to an End Point within the LLN.  The route
   is measured in the Forward direction.  Such a route could be a Source
   Route or a Hop-by-hop Route established using RPL [RFC6550] or P2P-



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   RPL [I-D.ietf-roll-p2p-rpl].  Such a route could also be a "mixed"
   route with the initial part consisting of hop-by-hop ascent to the
   root of a non-storing DAG [RFC6550] and the final part consisting of
   a source-routed descent to the End Point.  The Start Point decides
   what metrics to measure and sends a Measurement Request message,
   carrying the desired routing metric objects, along the route.  If a
   Source Route is being measured, the Measurement Request carries the
   route inside an Address vector.  If a Hop-by-hop Route is being
   measured, the Measurement Request identifies the route by its
   RPLInstanceID [RFC6550] (and, in case the RPLInstanceID is a local
   value, the Start Point's IPv6 address associated with the route).  On
   receiving a Measurement Request, an Intermediate Point updates the
   routing metric values inside the message and forwards it to the next
   hop on the route.  Thus, the Measurement Request accumulates the
   values of the routing metrics for the complete route as it travels
   towards the End Point.  Upon receiving the Measurement Request, the
   End Point unicasts a Measurement Reply message, carrying the
   accumulated values of the routing metrics, back to the Start Point.
   Optionally, the Start Point may allow an Intermediate Point to
   generate the Measurement Reply if the Intermediate Point already
   knows the relevant routing metric values along rest of the route.

   The Measurement Request may include an Address vector that serves one
   of the following functions:

   o  To accumulate a Source Route for End Point's use: If a Hop-by-hop
      Route with a local RPLInstanceID is being measured, the Start
      Point may require each Intermediate Point to add its global or
      unique local IPv6 address to an Address vector inside the
      Measurement Request.  The Source Route, thus accumulated, can be
      used by the End Point to reach the Start Point.  In particular,
      the End Point may use the accumulated Source Route to send the
      Measurement Reply back to the Start Point.  In this case, the
      Start Point includes a suitably-sized Address vector in the
      Measurement Request.  The size of the Address vector puts a hard
      limit on the length of the accumulated route.  An Intermediate
      Point is not allowed to modify the size of the Address vector and
      must discard a received Measurement Request if the Address vector
      is not large enough to contain the complete route.

   o  To carry the Source Route being measured: The Start Point may
      insert an Address vector inside the Measurement Request to carry
      the Source Route being measured.  Also, the root of a global non-
      storing DAG may insert an Address vector, carrying a Source Route
      from itself to the End Point, inside a Measurement Request message
      if this message had been traveling along this DAG so far.  This
      Source Route must consist of global or unique local IPv6
      addresses.  An Intermediate Point is not allowed to modify an



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      existing Address vector before forwarding the Measurement Request
      further.  In other words, an Intermediate Point must not modify
      the Source Route along which the Measurement Request is currently
      traveling.


3.  The Measurement Object (MO)

   This document defines two new RPL Control Message types, the
   Measurement Object (MO), with code TBD1, and the Secure MO, with code
   TBD2.  An MO serves as both Measurement Request and Measurement
   Reply.

3.1.  Format of the base MO

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | RPLInstanceID | Compr |T|H|A|R|B|I|   SeqNo   |  Num  | Index |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                       Start Point Address                     .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                       End Point Address                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                       Address[0..Num-1]                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                   Metric Container Option(s)                  .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


           Figure 1: Format of the base Measurement Object (MO)

   The format of a base MO is shown in Figure 1.  A base MO consists of
   the following fields:





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   o  RPLInstanceID: This field specifies the RPLInstanceID of the Hop-
      by-hop Route along which the Measurement Request travels (or
      traveled initially until it switched over to a Source Route).

   o  Compr: In many LLN deployments, IPv6 addresses share a well known,
      common prefix.  In such cases, the common prefix can be elided
      when specifying IPv6 addresses in the Start Point/End Point
      Address fields and the Address vector.  The "Compr" field, a 4-bit
      unsigned integer, is set by the Start Point to specify the number
      of prefix octets that are elided from the IPv6 addresses in Start
      Point/End Point Address fields and the Address vector.  The Start
      Point will set the Compr value to zero if full IPv6 addresses are
      to be carried in the Start Point Address/End Point Address fields
      and the Address vector.

   o  Type (T): This flag is set to one if the MO represents a
      Measurement Request.  The flag is set to zero if the MO is a
      Measurement Reply.

   o  Hop-by-hop (H): The Start Point MUST set this flag to one if (at
      least the initial part of) the route being measured is hop-by-hop.
      In that case, the Hop-by-hop Route is identified by the
      RPLInstanceID, the End Point Address and, if the RPLInstanceID is
      a local value, the Start Point Address fields inside the
      Measurement Request.  Here, the Start Point Address field is
      required to be same as the DODAGID (the identifier of the
      destination-oritented DAG root) [RFC6550] of the route being
      measured.  The Start Point MUST set the H flag to zero if the
      route being measured is a Source Route specified in the Address
      vector.  An Intermediate Point MUST set the H flag in an outgoing
      Measurement Request to the same value that it had in the
      corresponding incoming Measurement Request unless it is the root
      of the non-storing global DAG, identified by the RPLInstanceID,
      along which the Measurement Request had been traveling so far and
      the Intermediate Point intends to insert a Source Route inside the
      Address vector to direct it towards the End Point.  In that case,
      the Intermediate Point MUST set the H flag to zero.

   o  Accumulate Route (A): A value 1 in this flag indicates that the
      Measurement Request is accumulating a Source Route for use by the
      End Point to send the Measurement Reply back to the Start Point.
      Route accumulation MUST NOT be used (i.e., this flag MUST NOT be
      set to 1) inside a Measurement Request unless it travels along a
      Hop-by-hop Route represented by a local RPLInstanceID (i.e., H =
      1, RPLInstanceID has a local value).  Route accumulation MAY be
      used (i.e., this flag MAY be set to 1) if the Measurement Request
      is traveling along a Hop-by-hop Route with a local RPLInstanceID.
      In this case if the route accumulation is on, an Intermediate



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      Point adds its unicast global/unique-local IPv6 address (after
      eliding Compr number of prefix octets) to the Address vector in
      the manner specified in Section 5.3.  In other cases, this flag
      MUST be set to zero on transmission and ignored on reception.
      Route accumulation is not allowed when the Measurement Request
      travels along a Hop-by-hop Route with a global RPLInstanceID,
      i.e., along a global DAG, because:

      *  The DAG's root may need the Address vector to insert a Source
         Route to the End Point; and

      *  The End Point can presumably reach the Start Point along this
         global DAG (identified by the RPLInstanceID field).

   o  Reverse (R): A value 1 in this flag inside a Measurement Request
      indicates that the Address vector contains a complete Source Route
      from the Start Point to the End Point, which can be used, after
      reversal, by the End Point to send the Measurement Reply back to
      the Start Point.  This flag MAY be set to one inside a Measurement
      Request only if a Source Route, from the Start Point to the End
      Point, is being measured.  Otherwise, this flag MUST be set to
      zero on transmission and ignored on reception.

   o  Back Request (B): A value 1 in this flag serves as a request to
      the End Point to send a Measurement Request towards the Start
      Point.  On receiving a Measurement Request with the B flag set to
      one, the End Point SHOULD generate a Measurement Request to
      measure the cost of its current (or the most preferred) route to
      the Start Point.  Receipt of this Measurement Request would allow
      the Start Point to know the cost of the back route from the End
      Point to itself and thus determine the round-trip cost of reaching
      the End Point.

   o  Intermediate Reply (I): A value 1 in this flag serves as a
      permission to an Intermediate Point to generate a Measurement
      Reply if it knows the aggregated values of the routing metrics
      being measured for the rest of the route.  Setting this flag to
      one may be useful in scenarios where the Hop Count [RFC6551] is
      the routing metric of interest and an Intermediate Point (e.g. the
      root of a non-storing global DAG or a common ancestor of the Start
      Point and the End Point in a storing global DAG) may know the Hop
      Count of the remainder of the route to the End Point.  This flag
      MAY be set to one only if a Hop-by-hop Route with a global
      RPLInstanceID is being measured (i.e., H = 1, RPLInstanceID has a
      global value).  Otherwise, this flag MUST be set to zero on
      transmission and ignored on reception.





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   o  SeqNo: A 6-bit sequence number, assigned by the Start Point, that
      allows the Start Point to uniquely identify a Measurement Request
      and the corresponding Measurement Reply.

   o  Num: This field indicates the number of elements, each (16 -
      Compr) octets in size, inside the Address vector.  If the value of
      this field is zero, the Address vector is not present in the MO.

   o  Index: If the Measurement Request is traveling along a Source
      Route contained in the Address vector (i.e., H = 0), this field
      indicates the index in the Address vector of the next hop on the
      route.  If the Measurement Request is traveling along a Hop-by-hop
      Route with a local RPLInstanceID and the Route Accumulation is on
      (i.e., H = 1, RPLInstanceID has a local value, A = 1), this field
      indicates the index in the Address vector where an Intermediate
      Point receiving the Measurement Request must store its IPv6
      address.  Otherwise, this field MUST be set to zero on
      transmission and ignored on reception.

   o  Start Point Address: A unicast global or unique local IPv6 address
      of the Start Point after eliding Compr number of prefix octets.
      If the Measurement Request is traveling along a Hop-by-hop Route
      and the RPLInstanceID field indicates a local value, the Start
      Point Address field MUST specify the DODAGID value that, along
      with the RPLInstanceID and the End Point Address, uniquely
      identifies the Hop-by-hop Route being measured.

   o  End Point Address: A unicast global or unique local IPv6 address
      of the End Point after eliding Compr number of prefix octets.

   o  Address[0..Num-1]: A vector of unicast global or unique local IPv6
      addresses (with Compr number of prefix octets elided) representing
      a Source Route:

      *  Each element in the vector has size (16 - Compr) octets.

      *  The total number of elements inside the Address vector is given
         by the Num field.

      *  The Start Point and End Point addresses MUST NOT be included in
         the Address vector.

      *  The Address vector MUST NOT contain any multicast addresses.

      *  If the Start Point wants to measure a Hop-by-hop Route with a
         local RPLInstanceID and accumulate a Source Route for the End
         Point's use (i.e., the Measurement Request has the H flag set
         to 1, RPLInstanceID set to a local value and the A flag set to



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         1), it MUST include a suitably-sized Address vector in the
         Measurement Request.  As the Measurement Request travels over
         the route being measured, the Address vector accumulates a
         Source Route that can be used by the End Point, after reversal,
         to reach (and, in particular, to send the Measurement Reply
         back to) the Start Point.  The route MUST be accumulated in the
         Forward direction but the IPv6 addresses in the accumulated
         route MUST be reachable in the Reverse direction.  An
         Intermediate Point MUST add only a global or unique local IPv6
         address to the Address vector and MUST NOT modify the size of
         the Address vector.

      *  If the Start Point wants to measure a Source Route, it MUST
         include an Address vector, containing the route being measured,
         inside the Measurement Request.  Similarly, if the Measurement
         Request had been traveling along a global non-storing DAG so
         far, the root of this DAG may insert an Address vector,
         containing a Source Route from itself to the End Point, inside
         the Measurement Request.  In both cases, the Source Route
         inside the Address vector MUST consist only of global or unique
         local IPv6 addresses that are reachable in the Forward
         direction.  Further, in both cases, an Intermediate Point MUST
         NOT modify the contents of the existing Address vector before
         forwarding the Measurement Request further.  In other words, an
         Intermediate Point MUST NOT modify the Source Route along which
         the Measurement Request is currently traveling.  The Start
         Point MAY set the R flag in the Measurement Request to one if
         the Source Route inside the Address vector can be used by the
         End Point, after reversal, to reach (and, in particular, to
         send the Measurement Reply back to) the Start Point.  In other
         words, the Start Point MAY set the R flag to one only if all
         the IPv6 addresses in the Address vector are reachable in the
         Reverse direction.

   o  Metric Container Options: A Measurement Request MUST contain one
      or more Metric Container options [RFC6550] to accumulate the
      values of the selected routing metrics in the manner described in
      [RFC6551] for the route being measured.

   Section 4 describes how a Start Point sets various fields inside a
   Measurement Request in different cases.  Section 5 describes how an
   Intermediate Point processes a received Measurement Request before
   forwarding it further.  Section 6 describes how the End Point
   processes a received Measurement Request and generate a Measurement
   Reply.  Finally, Section 7 describes how the Start Point processes a
   received Measurement Reply.  In the following discussion, any
   reference to discarding a received Measurement Request/Reply with "no
   further processing" does not preclude updating the appropriate error



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   counters or any similar actions.

3.2.  Secure MO

   A Secure MO follows the format in Figure 7 of [RFC6550], where the
   base format is the base MO shown in Figure 1.  Sections 6.1, 10 and
   19 of [RFC6550] describe RPL security framework.  These sections are
   applicable to the use of Secure MO messages as well except as
   constrained in this section.  An LLN deployment MUST support the use
   of Secure MO messages so that it has the ability to invoke RPL-
   provided security mechanisms and prevent misuse of the measurement
   mechanism by unauthorized routers.

   The Start Point determines whether Secure MO messages are to be used
   in a particular route measurement and if yes the Security
   Configuration (see definition in [I-D.ietf-roll-p2p-rpl]) to be used
   for the purpose.  The Start Point MUST NOT set the "Key Identifier
   Mode" field to value 1 inside this Security Configuration since this
   setting indicates the use of a per-pair key which is not suitable for
   securing the Measurement Request messages that travel over multiple
   hops.  A router (an Intermediate Point or the End Point),
   participating in a particular route measurement,

   o  MUST generate a Secure MO message (a Measurement Request or a
      Measurement Reply) if the received Measurement Request is a Secure
      MO.  The Security Configuration used in generating a Secure MO
      message MUST be same as the one used in the received message.

   o  MUST NOT generate a Secure MO message if the received Measurement
      Request is not a Secure MO.

   A router MUST discard a received Measurement Request if it cannot
   follow the above mentioned rules.  If the Start Point sends a
   Measurement Request in a Secure MO message using a particular
   Security Configuration, it MUST discard the corresponding Measurement
   Reply it receives with no further processing unless the Measurement
   Reply is received in a Secure MO message generated with same Security
   Configuration as the one used in the Measurement Request.

   In the following discussion, any reference to an MO message is also
   applicable to a Secure MO message unless noted otherwise.


4.  Originating a Measurement Request

   A Start Point sets various fields inside the Measurement Request it
   generates in the manner described below.  The Start Point MUST also
   include the routing metric objects [RFC6551] of interest inside one



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   or more Metric Container options inside the Measurement Request.  The
   Start Point then determines the next hop on the route being measured.
   If a Hop-by-hop route is being measured (i.e., H = 1), the next hop
   is determined using the RPLInstanceID, the End Point Address and, if
   RPLInstanceID is a local value, the Start Point Address fields in the
   Measurement Request.  If a Source Route is being measured (i.e., H =
   0), the Address[0] element inside the Measurement Request contains
   the next hop address.  The Start Point MUST ensure that

   o  the next hop address is a unicast address; and

   o  the next hop is on-link; and

   o  the next hop is in the same RPL routing domain
      [I-D.ietf-roll-terminology] as the Start Point;

   failing which the Start Point MUST discard the Measurement Request
   without sending.  Depending on the routing metrics, the Start Point
   must initiate the routing metric objects inside the Metric Container
   options by including the routing metric values for the first hop on
   the route being measured.  Finally, the Start Point MUST unicast the
   Measurement Request to the next hop on the route being measured.

   The Start Point MUST maintain state for just transmitted Measurement
   Request for a life time duration that is large enough to allow the
   corresponding Measurement Reply to return.  This state consists of
   the RPLInstanceID, the SeqNo and the End Point Address fields of the
   Measurement Request.  The life time duration for this state is
   locally determined by the Start Point and may be deployment specific.
   This state expires when the corresponding Measurement Reply is
   received or when the life time is over, whichever occurs first.
   Failure to receive the corresponding Measurement Reply before the
   expiry of a state may occur due to a number of reasons including
   unwillingness on part of an Intermediate Point or the End Point to
   process the Measurement Request.  The Start Point should take such
   possibilities in account when deciding whether to generate another
   Measurement Request for this route.  The Start Point MUST discard a
   received Measurement Reply with no further processing if the state
   for the corresponding Measurement Request has already expired.

4.1.  When Measuring A Hop-by-hop Route with a Global RPLInstanceID

   If a Hop-by-hop Route with a global RPLInstanceID is being measured
   (i.e., H = 1, RPLInstanceID has a global value), the MO MUST NOT
   contain an Address vector and various MO fields MUST be set in the
   following manner:





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   o  RPLInstanceID: MUST be set to the RPLInstanceID of the route being
      measured.

   o  Compr: MUST be set to specify the number of prefix octets that are
      elided from the IPv6 addresses in Start Point/End Point Address
      fields.

   o  Type (T): MUST be set to one since the MO represents a Measurement
      Request.

   o  Hop-by-hop (H): MUST be set to one.

   o  Accumulate Route (A): This flag MUST be set to zero.

   o  Reverse (R): This flag MUST be set to zero.

   o  Back Request (B): This flag MAY be set to one to request the End
      Point to send a Measurement Request to the Start Point.

   o  Intermediate Reply (I): This flag MAY be set to one if the Start
      Point expects an Intermediate Point to know the values of the
      routing metrics being measured for the remainder of the route.

   o  SeqNo: Assigned by the Start Point so that it can uniquely
      identify the Measurement Request and the corresponding Measurement
      Reply.

   o  Num: This field MUST be set to zero.

   o  Index: This field MUST be set to zero.

   o  Start Point Address: MUST be set to a unicast global/unique-local
      IPv6 address of the Start Point after eliding Compr number of
      prefix octets.

   o  End Point Address: MUST be set to a unicast global/unique-local
      IPv6 address of the End Point after eliding Compr number of prefix
      octets.

4.2.  When Measuring A Hop-by-hop Route with a Local RPLInstanceID With
      Route Accumulation Off

   If a Hop-by-hop Route with a local RPLInstanceID is being measured
   and the Start Point does not want the MO to accumulate a Source Route
   for the End Point's use, the MO MUST NOT contain the Address vector
   and various MO fields MUST be set in the following manner:





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   o  RPLInstanceID: MUST be set to the RPLInstanceID of the route being
      measured.

   o  Compr: MUST be set to specify the number of prefix octets that are
      elided from the IPv6 addresses in Start Point/End Point Address
      fields.

   o  Type (T): MUST be set to one since the MO represents a Measurement
      Request.

   o  Hop-by-hop (H): MUST be set to one.

   o  Accumulate Route (A): This flag MUST be set to zero.

   o  Reverse (R): This flag MUST be set to zero.

   o  Back Request (B): This flag MAY be set to one to request the End
      Point to send a Measurement Request to the Start Point.

   o  Intermediate Reply (I): This flag MUST be set to zero.

   o  SeqNo: Assigned by the Start Point so that it can uniquely
      identify the Measurement Request and the corresponding Measurement
      Reply.

   o  Num: This field MUST be set to zero.

   o  Index: This field MUST be set to zero.

   o  Start Point Address: This field MUST contain the DODAGID value
      (after eliding Compr number of prefix octets) associated with the
      route being measured.  This DODAGID MUST also be a global or
      unique local IPv6 address of the Start Point.

   o  End Point Address: MUST be set to a unicast global or unique local
      IPv6 address of the End Point after eliding Compr number of prefix
      octets.

4.3.  When Measuring A Hop-by-hop Route with a Local RPLInstanceID With
      Route Accumulation On

   If a Hop-by-hop Route with a local RPLInstanceID is being measured
   and the Start Point desires the MO to accumulate a Source Route for
   the End Point to send the Measurement Reply message back, the MO MUST
   contain a suitably-sized Address vector and various MO fields MUST be
   set in the following manner:





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   o  RPLInstanceID: MUST be set to the RPLInstanceID of the route being
      measured.

   o  Compr: MUST be set to specify the number of prefix octets that are
      elided from the IPv6 addresses in Start Point/End Point Address
      fields and the Address vector.

   o  Type (T): MUST be set to one since the MO represents a Measurement
      Request.

   o  Hop-by-hop (H): MUST be set to one.

   o  Accumulate Route (A): This flag MUST be set to one.

   o  Reverse (R): This flag MUST be set to zero.

   o  Back Request (B): This flag MAY be set to one to request the End
      Point to send a Measurement Request to the Start Point.

   o  Intermediate Reply (I): This flag MUST be set to zero.

   o  SeqNo: Assigned by the Start Point so that it can uniquely
      identify the Measurement Request and the corresponding Measurement
      Reply.

   o  Num: This field MUST specify the number of address elements, each
      (16 - Compr) octets in size, that can fit inside the Address
      vector.

   o  Index: This field MUST be set to zero to indicate the position in
      the Address vector where the next hop must store its IPv6 address.

   o  Start Point Address: This field MUST contain the DODAGID value
      (after eliding Compr number of prefix octets) associated with the
      route being measured.  This DODAGID MUST also be a global or
      unique local IPv6 address of the Start Point.

   o  End Point Address: MUST be set to a unicast global or unique local
      IPv6 address of the End Point after eliding Compr number of prefix
      octets.

   o  Address vector: The Address vector must be large enough to
      accomodate a complete Source Route from the End Point to the Start
      Point.  All the bits in the Address vector field MUST be set to
      zero.






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4.4.  When Measuring A Source Route

   If a Source Route is being measured, the Start Point MUST set various
   MO fields in the following manner:

   o  RPLInstanceID: This field does not have any significance when a
      Source Route is being measured and hence can be set to any value.

   o  Compr: MUST be set to specify the number of prefix octets that are
      elided from the IPv6 addresses in Start Point/End Point Address
      fields and the Address vector.

   o  Type (T): MUST be set to one since the MO represents a Measurement
      Request.

   o  Hop-by-hop (H): MUST be set to zero.

   o  Accumulate Route (A): This flag MUST be set to zero.

   o  Reverse (R): This flag SHOULD be set to one if the Source Route in
      the Address vector can be reversed and used by the End Point to
      send the Measurement Reply message back to the Start Point.
      Otherwise, this flag MUST be set to zero.

   o  Back Request (B): This flag MAY be set to one to request the End
      Point to send a Measurement Request to the Start Point.

   o  Intermediate Reply (I): This flag MUST be set to zero.

   o  SeqNo: Assigned by the Start Point so that it can uniquely
      identify the Measurement Request and the corresponding Measurement
      Reply.

   o  Num: This field MUST specify the number of address elements, each
      (16 - Compr) octets in size, inside the Address vector.

   o  Index: This field MUST be set to zero to indicate the position in
      the Address vector of the next hop on the route.

   o  Start Point Address: MUST be set to a unicast global or unique
      local IPv6 address of the Start Point after eliding Compr number
      of prefix octets.

   o  End Point Address: MUST be set to a unicast global or unique local
      IPv6 address of the End Point after eliding Compr number of prefix
      octets.





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   o  Address vector:

      *  The Address vector MUST contain a complete Source Route from
         the Start Point to the End Point (excluding the Start Point and
         the End Point).

      *  Each address appearing in the Address vector MUST be a unicast
         global or unique local IPv6 address.  Further, each address
         MUST have the same prefix as the Start Point Address and the
         End Point Address.  This prefix, whose length in octets is
         specified in the Compr field, MUST be elided from each address.

      *  The IPv6 addresses in the Address vector MUST be reachable in
         the Forward direction.

      *  If the R flag is set to one, the IPv6 addresses in the Address
         vector MUST also be reachable in the Reverse direction.


5.  Processing a Measurement Request at an Intermediate Point

   A router (an Intermediate Point or the End Point) MAY discard a
   received MO with no processing to meet any policy-related goal.  Such
   policy goals may include the need to reduce the router's CPU load or
   to enhance its battery life or to prevent misuse of this mechanism by
   unauthorized nodes.

   A router MUST discard a received MO with no further processing if the
   value in the Compr field inside the received message is more than
   what the router considers the length of the common prefix used in
   IPv6 addresses in the LLN to be.

   On receiving an MO, if a router chooses to process the packet
   further, it MUST check if one of its IPv6 addresses is listed as
   either the Start Point or the End Point Address.  If neither, the
   router considers itself an Intermediate Point and MUST process the
   received MO in the following manner.

   An Intermediate Point MUST discard the packet with no further
   processing if the received MO is not a Measurement Request (i.e., T =
   0).  This is because the End Point unicasts a Measurement Reply
   directly to the Start Point.  So, the Intermediate Point treats a
   transiting Measurement Reply as a data packet and not an RPL control
   message.

   Next, the Intermediate Point determines the type of the route being
   measured (by checking the values of the H flag and the RPLInstanceID
   field) and processes the received MO accordingly in the manner



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   specified next.

5.1.  When Measuring A Hop-by-hop Route with a Global RPLInstanceID

   If a Hop-by-hop Route with a global RPLInstanceID is being measured
   (i.e.  H = 1 and RPLInstanceID has a global value), the Intermediate
   Point MUST process the received Measurement Request in the following
   manner.

   If the Num field inside the received Measurement Request is not set
   to zero, thereby implying that an Address vector is present, the
   Intermediate Point MUST discard the received message with no further
   processing.

   If the Intermediate Reply (I) flag is set to one in the received
   Measurement Request and the Intermediate Point knows the values of
   the routing metrics, specified in the Metric Container options, for
   the remainder of the route, it MAY generate a Measurement Reply on
   the End Point's behalf in the manner specified in Section 6.1 (after
   including in the Measurement Reply the relevant routing metric values
   for the complete route being measured).  Otherwise, the Intermediate
   Point MUST process the received message in the following manner.

   The Intermediate Point MUST determine the next hop on the route being
   measured using the RPLInstanceID and the End Point Address.  If the
   Intermediate Point is the root of the non-storing global DAG along
   which the received Measurement Request had been traveling so far, it
   MUST process the received Measurement Request in the following
   manner:

   o  If the router does not know how to reach the End Point, it MUST
      discard the Measurement Request with no further processing and MAY
      send an ICMPv6 Destination Unreachable (with Code 0 - No Route To
      Destination) error message [RFC4443] to the Start Point.

   o  Otherwise, unless the router determines the End Point itself to be
      the next hop, the router MUST make the following changes in the
      received Measurement Request:

      *  Set the H, A, R and I flags to zero (the A and R flags should
         already be zero in the received message).

      *  Leave remaining fields unchanged (the Num field would be
         modified in next steps).  Note that the RPLInstanceID field
         identifies the non-storing global DAG along which the
         Measurement Request traveled so far.  This information MUST be
         preserved so that the End Point may use this DAG to send the
         Measurement Reply back to the Start Point.



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      *  Insert a new Address vector inside the Measurement Request and
         specify a Source Route to the End Point inside the Address
         vector as per the following rules:

         +  The Address vector MUST contain a complete route from the
            router to the End Point (excluding the router and the End
            Point);

         +  Each address appearing in the Address vector MUST be a
            unicast global or unique local IPv6 address.  Further, each
            address MUST have the same prefix as the Start Point Address
            and the End Point Address.  This prefix, whose length in
            octets is specified in the Compr field, MUST be elided from
            each address.

         +  The IPv6 addresses in the Address vector MUST be reachable
            in the Forward direction;

         If the router cannot insert an Address vector satisfying the
         rules mentioned above, it MUST discard the Measurement Request
         with no further processing and MAY send an ICMPv6 Destination
         Unreachable (with Code 0 - No Route To Destination) error
         message [RFC4443] to the Start Point.

      *  Specify in the Num field the number of address elements in the
         Address vector.

      *  Set the Index field to zero to indicate the position in the
         Address vector of the next hop on the route.  Thus, Address[0]
         element contains the address of the next hop on the route.

   The Intermediate Point MUST then complete the processing of the
   received Measurement Request as specified in Section 5.5.

5.2.  When Measuring A Hop-by-hop Route with a Local RPLInstanceID With
      Route Accumulation Off

   If a Hop-by-hop Route with a local RPLInstanceID is being measured
   and the route accumulation is off (i.e., H = 1, RPLInstanceID has a
   local value, A = 0), the Intermediate Point MUST process the received
   Measurement Request in the following manner.

   If the Num field inside the received Measurement Request is not set
   to zero, thereby implying that an Address vector is present, the
   Intermediate Point MUST discard the received message with no further
   processing.

   The Intermediate Point MUST then determine the next hop on the route



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   being measured using the RPLInstanceID, the End Point Address and the
   Start Point Address (which represents the DODAGID of the route being
   measured).  If the Intermediate Point can not determine the next hop,
   it MUST discard the Measurement Request with no further processing
   and MAY send an ICMPv6 Destination Unreachable (with Code 0 - No
   Route To Destination) error message [RFC4443] to the Start Point.
   Otherwise, the Intermediate Point MUST complete the processing of the
   received Measurement Request as specified in Section 5.5.

5.3.  When Measuring A Hop-by-hop Route with a Local RPLInstanceID With
      Route Accumulation On

   If a Hop-by-hop Route with a local RPLInstanceID is being measured
   and the route accumulation is on (i.e., H = 1, RPLInstanceID has a
   local value, A = 1), the Intermediate Point MUST process the received
   Measurement Request in the following manner.

   If the Num field inside the received Measurement Request is set to
   zero, thereby implying that an Address vector is not present, the
   Intermediate Point MUST discard the received message with no further
   processing.

   The Intermediate Point MUST then determine the next hop on the route
   being measured using the RPLInstanceID, the End Point Address and the
   Start Point Address (which represents the DODAGID of the route being
   measured).  If the Intermediate Point can not determine the next hop,
   it MUST discard the Measurement Request with no further processing
   and MAY send an ICMPv6 Destination Unreachable (with Code 0 - No
   Route To Destination) error message [RFC4443] to the Start Point.  If
   the index field has value Num - 1 and the next hop is not same as the
   End Point, the Intermediate Point MUST drop the received Measurement
   Request with no further processing.  In this case, the next hop would
   have no space left in the Address vector to store its address.
   Otherwise, the router MUST store one of its IPv6 addresses at
   location Address[Index] and then increment the Index field.  The IPv6
   address added to the Address vector MUST have the following
   properties:

   o  This address MUST be a unicast global or unique local address.

   o  This address MUST have the same prefix as the Start Point Address
      and the End Point Address.  This prefix, whose length in octets is
      specified in the Compr field, MUST be elided before the address is
      added to the Address vector.

   o  This address MUST be reachable in the Reverse direction.

   If the router does not have an IPv6 address that satisfies the



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   properties mentioned above, it MUST discard the Measurement Request
   with no further processing.

   The Intermediate Point MUST then complete the processing of the
   received Measurement Request as specified in Section 5.5.

5.4.  When Measuring A Source Route

   If a Source Route is being measured (i.e., H = 0), the Intermediate
   Point MUST process the received Measurement Request in the following
   manner.

   If the Num field inside the received Measurement Request is set to
   zero, thereby implying that an Address vector is not present, the
   Intermediate Point MUST discard the received message with no further
   processing.

   The Intermediate Point MUST verify that the Address[Index] element
   lists one of its unicast global or unique local IPv6 addresses (minus
   the prefix whose length in octets is specified in the Compr field),
   failing which it MUST discard the Measurement Request with no further
   processing.  The Intermediate Point MUST then increment the Index
   field and use the Address[Index] element as the next hop (unless
   Index value is now Num).  If the Index value is now Num, the
   Intermediate Point MUST use the End Point Address as the next hop.

   The Intermediate Point MUST then complete the processing of the
   received Measurement Request as specified in Section 5.5.

5.5.  Final Processing

   The Intermediate Point MUST drop the received Measurement Request
   with no further processing:

   o  If the next hop address is not a unicast address; or

   o  If the next hop is not on-link; or

   o  If the next hop is not in the same RPL routing domain as the
      Intermediate Point.

   Next, the Intermediate Point MUST update the routing metric objects,
   inside the Metric Container option(s) inside the Measurement Request,
   either by updating the aggregated value for the routing metric or by
   attaching the local values for the metric inside the object.  An
   Intermediate Point can only update the existing metric objects and
   MUST NOT add any new routing metric object to the Metric Container.
   An Intermediate Point MUST drop the Measurement Request with no



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   further processing if it cannot update a routing metric object
   specified inside the Metric Container.

   Finally, the Intermediate Point MUST unicast the Measurement Request
   to the next hop.


6.  Processing a Measurement Request at the End Point

   On receiving an MO, if a router chooses to process the message
   further and finds one of its unicast global or unique local IPv6
   addresses (minus the prefix whose length in octets is specified in
   the Compr field) listed as the End Point Address, the router
   considers itself the End Point and MUST process the received MO in
   the following manner.

   The End Point MUST discard the received message with no further
   processing if it is not a Measurement Request (i.e., T = 0).

   If the received Measurement Request traveled on a Hop-by-hop Route
   with a local RPLInstanceID with route accumulation on (i.e., H = 1,
   RPLInstanceID has a local value and A = 1), elements Address[0]
   through Address[Index - 1] in the Address vector contain a complete
   Source Route from the Start Point to the End Point, which the End
   Point MAY use, after reversal, to reach the Start Point.  Note that
   the Source Route in the Address vector does not include the Start
   Point and the End Point addresses and the individual addresses do not
   include the common prefix whose length in octets is specified in the
   Compr field.

   If the received Measurement Request traveled on a Source Route and
   the Reverse flag is set to one (i.e., H = 0, R = 1), elements
   Address[0] through Address[Num - 1] in the Address vector contain a
   complete Source Route from the Start Point to the End Point, which
   the End Point MAY use, after reversal, to reach the Start Point.
   Again, the Source Route in the Address vector does not include the
   Start Point and the End Point addresses and the individual addresses
   do not include the common prefix whose length in octets is specified
   in the Compr field.

   The End Point MUST update the routing metric objects in the Metric
   Container options if required and MAY note the measured values for
   the complete route (especially, if the received Measurement Request
   is likely a response to an earlier Measurement Request that the End
   Point had sent to the Start Point with B flag set to one).

   The End Point MUST generate a Measurement Reply message as specified
   in Section 6.1.  If the B flag is set to one in the received



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   Measurement Request, the End Point SHOULD generate a new Measurement
   Request to measure the cost of its current (or the most preferred)
   route to the Start Point.  The routing metrics used in the new
   Measurement Request MUST include the routing metrics specified in the
   received Measurement Request.

6.1.  Generating the Measurement Reply

   A Measurement Reply MUST have the Type (T) flag set to zero and need
   not contain the Address vector.  The following fields inside a
   Measurement Reply MUST have the same values as they had inside the
   corresponding Measurement Request: RPLInstanceID, Compr, SeqNo, Start
   Point Address, End Point Address and Metric Container Option(s).  The
   remaining fields inside a Measurement Reply may have any value and
   MUST be ignored on reception at the Start Point; the received
   Measurement Request can, therefore, trivially be converted into a
   Measurement Reply by setting the Type (T) flag to zero.

   A Measurement Reply MUST be unicast back to the Start Point:

   o  If the Measurement Request traveled along a global DAG, identified
      by the RPLInstanceID field, the Measurement Reply MAY be unicast
      back to the Start Point along the same DAG.

   o  If the Measurement Request traveled along a Hop-by-hop Route with
      a local RPLInstanceID and accumulated a Source Route from the
      Start Point to the End Point, this Source Route MAY be used after
      reversal to send the Measurement Reply back to the Start Point.

   o  If the Measurement Request traveled along a Source Route and the R
      flag inside the received message is set to one, the End Point MAY
      reverse the Source Route contained in the Address vector and use
      it to send the Measurement Reply back to the Start Point.


7.  Processing a Measurement Reply at the Start Point

   When a router receives an MO, it examines if one of its unicast IPv6
   addresses is listed as the Start Point Address.  If yes, the router
   is the Start Point and MUST process the received message in the
   following manner.

   If the Start Point discovers that the received MO is not a
   Measurement Reply or if it no longer maintains state for the
   corresponding Measurement Request, it MUST discard the received
   message with no further processing.

   The Start Point can use the routing metric objects inside the Metric



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   Container to evaluate the metrics for the measured P2P route.  If a
   routing metric object contains local metric values recorded by
   routers on the route, the Start Point can make use of these local
   values by aggregating them into an end-to-end metric according to the
   aggregation rules for the specific metric.  A Start Point is then
   free to interpret the metrics for the route according to its local
   policy.


8.  Security Considerations

   In general, the security considerations for the route measurement
   mechanism described in this document are similar to the ones for RPL
   (as described in Section 19 of [RFC6550]).  Sections 6.1 and 10 of
   RPL specification [RFC6550] describe RPL's security framework that
   provides data confidentiality, authentication, replay protection and
   delay protection services.  This security framework is applicable to
   the route measurement mechanism described here as well after taking
   in account the constraints specified in Section 3.2.

   This document requires all routers participating in a secure
   invocation of the route measurement process to use the Security
   Configuration decided by the Start Point.  The intention is to avoid
   compromising the overall security of the route measurement due to
   some routers using a weaker Security Configuration.  A router is
   allowed to participate in a "secure" route measurement only if it can
   support the Security Configuration in use, which also specifies the
   key in use.  It does not matter whether the key is pre-installed or
   dynamically acquired after proper authentication.  The router must
   have the key in use before it can process or generate Secure MO
   messages.  Hence, from the perspective of the route measurement
   mechanism, there is no distinction between the "preinstalled" and
   "authenticated" security modes described in RPL specification
   [RFC6550].  Ofcourse if a compromised router has the key being used,
   it could cause the route measurement to fail, or worse, insert wrong
   information in Secure MO messages.

   A rogue router acting as the Start Point could use the route
   measurement mechanism defined in this document to measure routes from
   itself to other routers and thus find out key information about the
   LLN, e.g., the topological features of the LLN (such as the identity
   of the key routers in the topology) or the remaining energy levels
   [RFC6551] in the routers.  This information can potentially be used
   to attack the LLN.  A rogue router could also use this mechanism to
   send bogus Measurement Requests to arbitrary End Points.  If
   sufficient Measurement Requests are sent, then it may cause CPU
   overload in the routers in the network, drain their batteries and
   cause traffic congestion in the network.  Note that some of these



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   problems would occur even if the compromised router were to generate
   bogus data traffic to arbitrary destinations.

   To protect against such misuse, this document allows RPL routers
   implementing this mechanism to not process MO messages (or process
   such messages selectively) based on a local policy.  For example, an
   LLN deployment might require the use of Secure MO messages generated
   using a key that could be obtained only after proper authentication.
   Note that this document requires an LLN deployment to support Secure
   MO messages so that such policies can be enforced where considered
   essential.

   Since a Measurement Request can travel along a Source Route specified
   in the Address vector, some of the security concerns that led to the
   deprecation of Type 0 routing header [RFC5095] may be valid here.  To
   address such concerns, the mechanism described in this document
   includes several remedies:

   o  This document requires that a route inserted inside the Address
      vector must be a strict Source Route and must not include any
      multicast addresses.

   o  This document requires that an MO message must not cross the
      boundaries of the RPL routing domain where it originated.  A
      router must not forward a received MO message further if the next
      hop belongs to a different RPL routing domain.  Hence, any
      security problems associated with the mechanism would be limited
      to one RPL routing domain.

   o  This document requires that a router must drop a received
      Measurement Request if the next hop address is not on-link or if
      it is not a unicast address.


9.  IANA Considerations

   This document defines two new RPL messages:

   o  "Measurement Object" (see Section 3.1), assigned a value TBD1 from
      the "RPL Control Codes" space [to be removed upon publication:
      http://www.iana.org/assignments/rpl/rpl.xml#control-codes]
      [RFC6550].  IANA is requested to allocate TBD1 from the range
      0x00-0x7F to indicate a message without security enabled.  The
      string TBD1 in this document should be replaced by the allocated
      value.  These last two sentences should be removed before
      publication.





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   o  "Secure Measurement Object" (see Section 3.2), assigned a value
      TBD2 from the "RPL Control Codes" space [to be removed upon
      publication:
      http://www.iana.org/assignments/rpl/rpl.xml#control-codes]
      [RFC6550].  IANA is requested to allocate TBD2 from the range
      0x80-0xFF to indicate a message with security enabled.  The string
      TBD2 in this document should be replaced by the allocated value.
      These last two sentences should be removed before publication.

           +------+---------------------------+---------------+
           | Code |        Description        |   Reference   |
           +------+---------------------------+---------------+
           | TBD1 |     Measurement Object    | This document |
           | TBD2 | Secure Measurement Object | This document |
           +------+---------------------------+---------------+

                             RPL Control Codes


10.  Acknowledgements

   Authors gratefully acknowledge the contributions of Ralph Droms,
   Adrian Farrel, Joel Halpern, Matthias Philipp, Pascal Thubert,
   Richard Kelsey and Zach Shelby in the development of this document.


11.  References

11.1.  Normative References

   [I-D.ietf-roll-p2p-rpl]
              Goyal, M., Baccelli, E., Philipp, M., Brandt, A., and J.
              Martocci, "Reactive Discovery of Point-to-Point Routes in
              Low Power and Lossy Networks", draft-ietf-roll-p2p-rpl-17
              (work in progress), March 2013.

   [I-D.ietf-roll-terminology]
              Vasseur, J., "Terminology in Low power And Lossy
              Networks", draft-ietf-roll-terminology-12 (work in
              progress), March 2013.

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

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
              Message Protocol (ICMPv6) for the Internet Protocol
              Version 6 (IPv6) Specification", RFC 4443, March 2006.




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   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

11.2.  Informative References

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              December 2007.

   [RFC5826]  Brandt, A., Buron, J., and G. Porcu, "Home Automation
              Routing Requirements in Low-Power and Lossy Networks",
              RFC 5826, April 2010.

   [RFC5867]  Martocci, J., De Mil, P., Riou, N., and W. Vermeylen,
              "Building Automation Routing Requirements in Low-Power and
              Lossy Networks", RFC 5867, June 2010.

   [RFC6551]  Vasseur, JP., Kim, M., Pister, K., Dejean, N., and D.
              Barthel, "Routing Metrics Used for Path Calculation in
              Low-Power and Lossy Networks", RFC 6551, March 2012.


Authors' Addresses

   Mukul Goyal (editor)
   University of Wisconsin Milwaukee
   3200 N Cramer St
   Milwaukee, WI  53211
   USA

   Phone: +1 414 2295001
   Email: mukul@uwm.edu


   Emmanuel Baccelli
   INRIA

   Phone: +33-169-335-511
   Email: Emmanuel.Baccelli@inria.fr
   URI:   http://www.emmanuelbaccelli.org/









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   Anders Brandt
   Sigma Designs
   Emdrupvej 26A, 1.
   Copenhagen, Dk-2100
   Denmark

   Phone: +45 29609501
   Email: abr@sdesigns.dk


   Jerald Martocci
   Johnson Controls
   507 E Michigan Street
   Milwaukee  53202
   USA

   Phone: +1 414 524 4010
   Email: jerald.p.martocci@jci.com

































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