Internet Engineering Task Force M. Goyal, Ed.
Internet-Draft University of Wisconsin
Intended status: Experimental Milwaukee
Expires: September 5, 2012 E. Baccelli
INRIA
A. Brandt
Sigma Designs
J. Martocci
Johnson Controls
March 4, 2012
A Mechanism to Measure the Quality of a Point-to-point Route in a Low
Power and Lossy Network
draft-ietf-roll-p2p-measurement-03
Abstract
This document specifies a mechanism that enables an RPL router to
measure the quality of an existing route towards another RPL router
in a low power and lossy network, 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
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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 September 5, 2012.
Copyright Notice
Copyright (c) 2012 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
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The Measurement Object (MO) . . . . . . . . . . . . . . . . . 4
3.1. Format of the base MO . . . . . . . . . . . . . . . . . . 5
3.2. Secure MO . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Originating a Measurement Request . . . . . . . . . . . . . . 9
4.1. To Measure A Hop-by-hop Route with a Global
RPLInstanceID . . . . . . . . . . . . . . . . . . . . . . 10
4.2. To Measure A Hop-by-hop Route with a Local
RPLInstanceID . . . . . . . . . . . . . . . . . . . . . . 10
4.3. To Measure A Source Route . . . . . . . . . . . . . . . . 11
5. Processing a Measurement Request at an Intermediate Router . . 12
5.1. Determining Next Hop For An MO Measuring A Source Route . 13
5.2. Determining Next Hop For An MO Measuring A Hop-by-hop
Route . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Processing a Measurement Request at the Target . . . . . . . . 14
7. Processing a Measurement Reply at the Origin . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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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]. RPL [I-D.ietf-roll-rpl], the IPv6
Routing Protocol for LLNs, 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
[I-D.ietf-roll-routing-metrics]. 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
[I-D.ietf-roll-routing-metrics] 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 are not overly strict;
otherwise the P2P-RPL route discovery may fail even though a route,
much better than the one currently being used, exists.
This document specifies a mechanism that enables an RPL router to
measure the aggregated values of the routing metrics along an
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existing route to another RPL router in an LLN, thereby allowing the
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.
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].
Additionally, this document uses terminology from
[I-D.ietf-roll-terminology], [I-D.ietf-roll-rpl] and
[I-D.ietf-roll-p2p-rpl]. The following terms, originally defined in
[I-D.ietf-roll-p2p-rpl], are redefined in the following manner.
Origin: The origin 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.
Target: The target refers to the RPL router at the end point of the
P2P route being measured.
Intermediate Router: An RPL router, other than the origin and the
target, on the P2P route being measured.
2. Overview
The mechanism described in this document can be used by an origin in
an LLN to measure the aggregated values of the routing metrics along
a P2P route to a target within the LLN. Such a route could be a
source route or a hop-by-hop route established using RPL
[I-D.ietf-roll-rpl] or P2P-RPL [I-D.ietf-roll-p2p-rpl]. The origin
sends a Measurement Request message along the route. The Measurement
Request accumulates the values of the routing metrics as it travels
towards the target. Upon receiving the Measurement Request, the
target unicasts a Measurement Reply message, carrying the accumulated
values of the routing metrics, back to the origin. Optionally, the
origin may allow an intermediate router to generate the Measurement
Reply if it already knows the relevant routing metric values along
rest of the route.
3. The Measurement Object (MO)
This document defines two new RPL Control Message types, the
Measurement Object (MO), with code 0x06 (to be confirmed by IANA),
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and the Secure MO, with code 0x86 (to be confirmed by IANA). 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| SequenceNo| Num | Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Origin Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Target Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Address[1..Num] .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. 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:
o RPLInstanceID: The origin sets this field to indicate the
RPLInstanceID of the route being measured. An intermediate router
MUST discard the received MO message if it is not aware of the RPL
Instance specified by the RPLInstanceID value. If the
RPLInstanceID is a local value, the RPL Instance is identified by
both the RPLInstanceID and the Origin Address fields. An
intermediate router MUST set the RPLInstanceID field in the
outgoing MO packet to the same value that it had in the
corresponding incoming MO packet.
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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 Origin/Target Address fields
and the Address vector. The "Compr" field, a 4-bit unsigned
integer, is set by the origin to specify the number of prefix
octets that are elided from the IPv6 addresses in Origin/Target
Address fields and the Address vector. An intermediate router
MUST set the Compr field in the outgoing MO packet to the same
value that it had in the corresponding incoming MO packet. The
Compr value will be 0 if full IPv6 addresses are carried in the
Origin/Target Address fields and the Address vector.
o Type (T): This flag is set to 1 if the MO represents a Measurement
Request. The flag is cleared to 0 if the MO is a Measurement
Reply.
o Hop-by-hop (H): The origin sets this flag to 1 if the route being
measured is a hop-by-hop route. In that case, the hop-by-hop
route is identified by the RPLInstanceID and, if the RPLInstanceID
is a local value, the Origin Address serving as the DODAGID. The
origin resets this flag to 0 if the route being measured is a
source route specified in the Address vector. An intermediate
router MUST set the H flag in an outgoing MO packet to the same
value that it had in the corresponding incoming MO packet unless
the router is the root of the non-storing global DAG, identified
by the RPLInstanceID, along which the MO packet had been traveling
so far. In that case, the DAG root MUST reset the H flag to 0 in
the outgoing MO packet if it intends to insert a source route in
the Address vector to direct the MO packet towards the target.
o Accumulate Route (A): This flag is relevant only if the MO
represents a Measurement Request that travels along a hop-by-hop
route represented by a local RPLInstanceID. In other words, this
flag MAY be set to 1 only if T = 1, H = 1 and the RPLInstanceID
field has a local value. Otherwise, this flag MUST be cleared to
0. A value 1 in this flag indicates that the Measurement Request
MUST accumulate a source route for use by the target to send the
Measurement Reply back to the origin. In this case, an
intermediate router MUST add its unicast IPv6 address (after
eliding Compr number of prefix octets) to the Address vector in
the manner specified later. 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 target; and
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* The target can presumably reach the origin along this global
DAG.
o Reverse (R): This flag is relevant only if the MO represents a
Measurement Request that travels along a source route, specified
in the Address vector, to the target. In other words, this flag
MAY be set to 1 only if T = 1 and H = 0. Otherwise, this flag
MUST be cleared to 0. A value 1 in the flag indicates that the
Address vector contains a complete source route from the origin to
the target, which can be used, after reversal, by the target to
source route the Measurement Reply message back to the origin.
o Back Request (B): This flag serves as a request to the target to
send a Measurement Request towards the origin. The origin MAY set
this flag to 1 if it wants to make such a request to the target.
An intermediate router MUST set the B flag in an outgoing MO
packet to the same value that it had in the corresponding incoming
MO packet. On receiving a Measurement Request with the B flag set
to 1, the target SHOULD generate a Measurement Request to measure
the cost of its current (or the most preferred) route to the
origin. Receipt of this Measurement Request would allow the
origin to know the cost of the back route from the target to
itself and thus determine the round-trip cost of reaching the
target.
o Intermediate Reply (I): Relevant only if a hop-by-hop route is
being measured, this flag serves as a permission to an
intermediate router to generate a Measurement Reply if it knows
the cost of the rest of the route being measured. The origin MAY
set this flag to 1 if a hop-by-hop route is being measured (i.e.,
H = 1) and the origin wants to allow an intermediate router to
generate the Measurement Reply in response to this Measurement
Request. Setting this flag may be useful in scenarios where the
Hop Count [I-D.ietf-roll-routing-metrics] is the routing metric of
interest and the origin expects an intermediate router (e.g. the
root of a non-storing DAG or a common ancestor of the origin and
the target in a storing DAG) to know the Hop Count of the
remainder of the route to the target. This flag MUST be cleared
to 0 if the route being measured is a source route (i.e., H = 0).
o SequenceNo: A 6-bit sequence number, assigned by the origin, that
allows the origin to uniquely identify a Measurement Request and
the corresponding Measurement Reply. An intermediate router MUST
set this field in the outgoing MO packet to the same value that it
had in the corresponding incoming MO packet. The target MUST set
this field in a Measurement Reply message to the same value that
it had in the corresponding Measurement Request message.
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o Num: The origin sets this field to indicate the number of fields
in 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 (T=1,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 A flag is set
(T=1,H=1,A=1 and RPLInstanceID field has a local value), this
field indicates the index in the Address vector where an
intermediate router receiving the MO message must store its IPv6
address. Otherwise, this field MUST be set to zero on
transmission and ignored on reception.
o Origin Address: A unicast IPv6 address of the origin after eliding
Compr number of prefix octets. If the MO is traveling along a
hop-by-hop route and the RPLInstanceID field indicates a local
value, the Origin Address field MUST specify the DODAGID value
that, along with the RPLInstanceID, uniquely identifies the hop-
by-hop route being measured.
o Target Address: A unicast IPv6 address of the target after eliding
Compr number of prefix octets.
o Address[1..Num]: A vector of unicast IPv6 addresses (with Compr
number of prefix octets elided) representing a source route to the
target:
* 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.
* When the Measurement Request is traveling along a hop-by-hop
route with local RPLInstanceID and has the A flag set, the
Address vector is used to accumulate a source route to be used
by the target to send the Measurement Reply back to the origin.
In this case, the route MUST be accumulated in the forward
direction, i.e., from the origin to the target. The target
router would reverse this route to obtain a source route from
itself to the origin. The IPv6 addresses in the accumulated
route MUST be accessible in the backward direction, i.e., from
the target to the origin. An intermediate router adding its
address to the Address vector MUST ensure that its address does
not already exist in the vector.
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* When the Measurement Request is traveling along a source route,
the Address vector MUST contain a complete route to the target
and the IPv6 addresses in the Address vector MUST be accessible
in the forward direction, i.e., from the origin to the target.
A router (origin or an intermediate router) inserting an
Address vector inside an MO MUST ensure that no address appears
more than once inside the vector. Each router on the way MUST
ensure that the loops do not exist within the source route.
The origin MAY set the R flag in the MO if the route in the
Address vector represents a complete route from the origin to
the target and this route can be used after reversal by the
target to send the Measurement Reply message back to the
origin.
* The origin and target addresses MUST NOT be included in the
Address vector.
* The Address vector MUST NOT contain any multicast addresses.
o Metric Container Options: An MO MUST contain one or more Metric
Container options to accumulate the routing metric values for the
route being measured.
3.2. Secure MO
A Secure MO message follows the format in Figure 7 of
[I-D.ietf-roll-rpl], where the base format is the base MO shown in
Figure 1.
4. Originating a Measurement Request
If an origin needs to measure the routing metric values along a P2P
route towards a target, it generates an MO message and sets its
fields as described in Section 3.1. The setting of MO fields in
specific cases is described below. In all cases, the origin MUST set
the T flag to 1 to indicate that the MO represents a Measurement
Request. The origin MUST also include one or more Metric Container
options inside the MO to carry the routing metric objects of
interest. Depending on the metrics being measured, the origin must
also initiate these routing metric objects by including the values of
the routing metrics for the first hop on the P2P route being
measured.
After setting the MO fields appropriately, the origin MUST unicast
the MO message to the next hop on the P2P route.
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4.1. To Measure A Hop-by-hop Route with a Global RPLInstanceID
If a hop-by-hop route with a global RPLInstanceID is being measured,
the MO message MUST NOT contain the Address vector and the following
MO fields MUST be set in the manner specified below:
o Hop-by-hop (H): This flag MUST be set to 1.
o Accumulate Route (A): This flag MUST be cleared to 0.
o Reverse (R): This flag MUST be cleared to 0.
o Num: This field MUST be cleared to 0.
o Index: This field MUST be cleared to 0.
4.2. To Measure A Hop-by-hop Route with a Local RPLInstanceID
If a hop-by-hop route with a local RPLInstanceID is being measured
and the MO is not accumulating a source route for the target's use,
the MO message MUST NOT contain the Address vector and the following
MO fields MUST be set in the manner specified below:
o Hop-by-hop (H): This flag MUST be set to 1.
o Accumulate Route (A): This flag MUST be cleared to 0.
o Reverse (R): This flag MUST be cleared to 0.
o Num: This field MUST be cleared to 0.
o Index: This field MUST be cleared to 0.
o Origin Address: This field MUST contain the DODAGID value (after
eliding Compr number of prefix octets) associated with the route
being measured.
If a hop-by-hop route with a local RPLInstanceID is being measured
and the origin desires the MO to accumulate a source route for the
target to send the Measurement Reply message back, it MUST set the
following MO fields in the manner specified below:
o Hop-by-hop (H): This flag MUST be set to 1.
o Accumulate Route (A): This flag MUST be set to 1.
o Reverse (R): This flag MUST be cleared to 0.
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o Intermediate Reply (I): This flag MUST be cleared to 0.
o Address vector: The Address vector must be large enough to
accomodate a complete source route from the origin to the target.
All the bits in the Address vector field MUST be cleared to 0.
o Num: This field MUST specify the number of address elements that
can fit inside the Address vector.
o Index: This field MUST be set to 1.
o Origin Address: This field MUST contain the DODAGID value (after
eliding Compr number of prefix octets) associated with the route
being measured.
4.3. To Measure A Source Route
If a source route is being measured, the origin MUST set the
following MO fields in the manner specified below:
o Hop-by-hop (H): This flag MUST be cleared to 0.
o Accumulate Route (A): This flag MUST be cleared to 0.
o Reverse (R): This flag SHOULD be set to 1 if the source route in
the Address vector can be reversed and used by the target to
source route the Measurement Reply message back to the origin.
Otherwise, this flag MUST be cleared to 0.
o Intermediate Reply (I): This flag MUST be cleared to 0.
o Address vector:
* The Address vector MUST contain a complete route from the
origin to the target (excluding the origin and the target).
* The IPv6 addresses (with Compr prefix octets elided) in the
Address vector MUST be accessible in the forward direction,
i.e., from the origin to the target.
* To prevent loops in the source route, the origin MUST ensure
compliance to the following rules:
+ Any IPv6 address MUST NOT appear more than once in the
Address vector.
+ If the Address vector includes multiple IPv6 addresses
assigned to the origin's interfaces, such addresses MUST
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appear back to back inside the Address vector.
* Each address appearing in the Address vector MUST be a unicast
address.
o Num: This field MUST be set to indicate the number of elements in
the Address vector.
o Index: This field MUST be set to 1.
The origin MUST NOT send the packet further if the next hop address
on the source route is not on-link.
5. Processing a Measurement Request at an Intermediate Router
A router (an intermediate router or the target) MAY discard a
received MO with no further 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.
A router MUST discard a received MO with no further processing:
o If the router is not aware of the RPL Instance identified by the
RPLInstanceID (and the Origin Address, if RPLInstanceID is a local
value) field in the message.
o If the Compr field is not same as what the router considers as the
length of the common prefix used in IPv6 addresses in the LLN.
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 Origin or the Target Address. If neither, the router
considers itself an Intermediate Router and MUST process the received
MO in the following manner.
An intermediate router MUST discard the packet with no further
processing if the received MO is not a Measurement Request.
If the I flag is set to 1 in the received MO and the intermediate
router knows the values of the routing metrics, specified in the
Metric Container, for the remainder of the route, it MAY generate a
Measurement Reply on the target's behalf in the manner specified in
Section 6 (after including in the Measurement Reply the relevant
routing metric values for the complete route being measured).
Otherwise, the intermediate router MUST process the received MO in
the following manner.
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The router MUST determine the next hop on the P2P route being
measured in the manner described below. The router MUST drop the MO
with no further processing and MAY send an ICMPv6 Destination
Unreachable (with Code 0 - No Route To Destination) error message to
the source of the message if it can not determine the next hop for
the message.
After determining the next hop, the router MUST update the routing
metric objects, contained in the Metric Container options inside the
MO, either by updating the aggregated value for the routing metric or
by attaching the local values for the metric inside the object.
After updating the routing metrics, the router MUST unicast the MO to
the next hop.
5.1. Determining Next Hop For An MO Measuring A Source Route
In case the received MO is measuring a source route (H=0),
o The router MUST verify that the Address[Index] element lists one
of its unicast IPv6 addresses, failing which the router MUST
discard the MO packet with no further processing;
o The router MUST then increment the Index field and use the
Address[Index] element as the next hop. If Index is greater than
Num, the router MUST use the Target Address as the next hop.
An intermediate router MUST discard the MO packet with no further
processing if the next hop address is not on-link or is not a unicast
address. To prevent loops, an intermediate router MUST check if the
Address vector includes multiple IPv6 addresses assigned to the
router's interfaces and if such addresses do not appear back to back
inside the Address vector. In this case, the router MUST discard the
MO packet with no further processing.
5.2. Determining Next Hop For An MO Measuring A Hop-by-hop Route
If the received MO is measuring a hop-by-hop route (H=1), the router
MUST use the RPLInstanceID, the Target Address and, if RPLInstanceID
is a local value, the Origin Address to determine the next hop for
the MO. Moreover,
o If the RPLInstanceID of the hop-by-hop route is a local value and
the A flag is set, the router MUST check if the Address vector
already contains one of its IPv6 addresses. If yes, the router
MUST discard the packet with no further processing. Otherwise,
the router MUST store one of its IPv6 addresses (after eliding
Compr prefix octets) at location Address[Index] and then increment
the Index field.
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o If the router is the root of the non-storing DAG along which the
received MO message has been traveling so far, the router MUST do
the following:
* Reset the H, A and R flags.
* Remove any existing Address vector inside the MO.
* Insert a new Address vector inside the MO and specify a source
route to the target inside the Address vector as per the
following rules:
+ The Address vector MUST contain a complete route from the
router to the target (excluding the router and the target);
+ The IPv6 addresses (with Compr prefix octets elided) in the
Address vector MUST be accessible in the forward direction,
i.e., towards the target;
+ To prevent loops in the source route, the router MUST ensure
that
- Any IPv6 address MUST NOT appear more than once in the
Address vector;
- If the Address vector includes multiple IPv6 addresses
assigned to the router's interfaces, such addresses MUST
appear back to back inside the Address vector.
+ Each address appearing in the Address vector MUST be a
unicast address.
* Specify in the Num field the number of address elements in the
Address vector.
* Set the Index field to 1.
6. Processing a Measurement Request at the Target
On receiving an MO, if a router chooses to process the packet further
and finds one of its unicast IPv6 addresses listed as the Target
Address, the router considers itself the target and MUST process the
received MO in the following manner.
The target MUST discard the packet with no further processing if the
received MO is not a Measurement Request.
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The target 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
target had sent to the origin with B flag set to 1).
The target MUST generate a Measurement Reply message. The
Measurement Reply message MUST have the same SequenceNo field as the
received Measurement Request message. The received Measurement
Request message can be trivially converted into the Measurement Reply
by reseting the T flag to zero. The target MAY remove the Address
vector from the Measurement Reply if desired. The target MUST then
unicast the Measurement Reply back to the origin:
o If the Measurement Request traveled along a DAG with a global
RPLInstanceID, the Measurement Reply MAY be unicast back to the
origin along the same DAG.
o If the Measurement Request traveled along a hop-by-hop route with
a local RPLInstanceID and the A flag inside the received message
is set to 1, the target MAY reverse the source route contained in
the Address vector and use it to send the Measurement Reply back
to the origin.
o If the Measurement Request traveled along a source route and the R
flag inside the received message is set to 1, the target MAY
reverse the source route contained in the Address vector and use
it to send the Measurement Reply back to the origin.
If the B flag in the received Measurement Request is set to 1, the
target MAY generate a new Measurement Request to measure the cost of
its current (or the most preferred) route to the origin. The routing
metrics used in the new Measurement Request MUST include the routing
metrics specified in the received Measurement Request.
7. Processing a Measurement Reply at the Origin
When a router receives an MO, it examines if one of its unicast IPv6
addresses is listed as the Origin Address. If yes, the router is the
origin and MUST process the received message in the following manner.
The origin MUST discard the packet with no further processing if the
received MO is not a Measurement Reply or if the origin has no
recollection of sending a Measurement Request with the sequence
number listed in the received MO.
The origin MUST examine the routing metric objects inside the Metric
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Container options to evaluate the quality of the measured P2P route.
If a routing metric object contains local metric values recorded by
routers on the route, the origin MUST aggregate these local values
into an end-to-end value as per the aggregation rules for the metric.
8. Security Considerations
The mechanism defined in this document can potentially be used by a
compromised router to generate bogus Measurement Requests to
arbitrary target routers. Such Measurement Requests may cause
processing overload in the routers in the network, drain their
batteries and cause traffic congestion in the network. Note that
some of these problems would occur even if the compromised router
were to generate bogus data traffic to arbitrary destinations.
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 Instance where it originated. A router must
drop a received MO message if it is not aware of the RPL Instance
referred to in the message. Hence, any security problems
associated with the mechanism would be limited to one RPL
Instance.
o This document requires that a router must drop a received MO
message if the next hop address is not on-link or if it is not a
unicast address.
o This document requires that a router must check the source route
inside the Address vector of each received MO message to ensure
that it does not contain a loop involving the router. The router
must drop the received packet if the source route does contain
such a loop. This and the previous two rules protect the network
against some of the security concerns even if a compromised node
inserts a malformed Address vector inside the MO message.
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9. IANA Considerations
IANA is requested to allocate new code points in the "RPL Control
Codes" registry for the "Measurement Object" and "Secure Measurement
Object" described in this document.
+------+---------------------------+---------------+
| Code | Description | Reference |
+------+---------------------------+---------------+
| 0x06 | Measurement Object | This document |
| 0x86 | Secure Measurement Object | This document |
+------+---------------------------+---------------+
RPL Control Codes
10. Acknowledgements
Authors gratefully acknowledge the contributions of Matthias Philipp,
Pascal Thubert, Richard Kelsey and Zach Shelby in the development of
this document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informative 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-08
(work in progress), March 2012.
[I-D.ietf-roll-routing-metrics]
Barthel, D., Vasseur, J., Pister, K., Kim, M., and N.
Dejean, "Routing Metrics used for Path Calculation in Low
Power and Lossy Networks",
draft-ietf-roll-routing-metrics-19 (work in progress),
March 2011.
[I-D.ietf-roll-rpl]
Brandt, A., Vasseur, J., Hui, J., Pister, K., Thubert, P.,
Levis, P., Struik, R., Kelsey, R., Clausen, T., and T.
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Winter, "RPL: IPv6 Routing Protocol for Low power and
Lossy Networks", draft-ietf-roll-rpl-19 (work in
progress), March 2011.
[I-D.ietf-roll-terminology]
Vasseur, J., "Terminology in Low power And Lossy
Networks", draft-ietf-roll-terminology-06 (work in
progress), September 2011.
[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.
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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