A Mechanism to Measure the Quality of a Point-to-point Route in a Low Power and Lossy Network
draft-ietf-roll-p2p-measurement-02
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (roll WG) | |
|---|---|---|---|
| Authors | Mukul Goyal , Emmanuel Baccelli , Anders Brandt , Jerry Martocci | ||
| Last updated | 2011-10-29 (Latest revision 2011-07-11) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Reviews | |||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-roll-p2p-measurement-02
Internet Engineering Task Force M. Goyal, Ed.
Internet-Draft University of Wisconsin
Intended status: Experimental Milwaukee
Expires: May 1, 2012 E. Baccelli
INRIA
A. Brandt
Sigma Designs
J. Martocci
Johnson Controls
October 29, 2011
A Mechanism to Measure the Quality of a Point-to-point Route in a Low
Power and Lossy Network
draft-ietf-roll-p2p-measurement-02
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
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 May 1, 2012.
Copyright Notice
Copyright (c) 2011 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
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) . . . . . . . . . . . . . . . . . 4
3.1. Format of the base MO . . . . . . . . . . . . . . . . . . 5
3.2. Secure MO . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Originating a Measurement Request . . . . . . . . . . . . . . 9
4.1. To Measure A Hop-by-hop Route with a Global
RPLInstanceID . . . . . . . . . . . . . . . . . . . . . . 9
4.2. To Measure A Hop-by-hop Route with a Local
RPLInstanceID . . . . . . . . . . . . . . . . . . . . . . 9
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 . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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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 routing costs to reach the
DAG's root and requires the P2P routes to use the DAG links only.
Such P2P routes may potentially be suboptimal and may lead to traffic
congestion near the DAG root. Additionally, RPL is a proactive
routing protocol and hence all P2P routes must be established ahead
of the time they are used.
To ameliorate situations, where RPL's P2P routing functionality does
not meet the requirements, [I-D.ietf-roll-p2p-rpl] describes a
reactive mechanism to discover P2P routes that meet the specified
performance criteria. This mechanism, henceforth referred to as the
reactive P2P route discovery, allows the specification of routing
constraints [I-D.ietf-roll-routing-metrics], that the discovered
routes must satisfy. In some cases, the application requirements or
the LLN's topological features allow a router to infer the routing
constraints intrinsically. For example, the application may require
the end-to-end loss rate and/or latency on 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 intrinsically know the routing constraints to be used in P2P
route discovery, it may be necessary for the router to determine the
aggregated values of the routing metrics along the existing route.
This knowledge will allow the router to frame reasonable routing
constraints for use in P2P route discovery to determine a better
route. 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 route discovery. Note that it is important
that the routing constraints are not overly strict; otherwise the P2P
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
existing route to another RPL router in an LLN, thereby allowing the
router to decide if it wants to initiate the reactive discovery of a
more optimal route and determine the routing constraints to be used
for this purpose.
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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 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 router at the end point of the P2P
route being measured.
Intermediate Router: A 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 RPL domain to measure the aggregated values of the routing metrics
along a P2P route to a target within the same RPL domain. Such a
route could be a source route or a hop-by-hop route established using
RPL [I-D.ietf-roll-rpl] or the reactive P2P route discovery
[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 route 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),
and the Secure MO, with code 0x86 (to be confirmed by IANA). An MO
serves as both Measurement Request and Measurement Reply.
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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: Relevant only if the MO travels along a hop-by-hop
route. This field identifies the RPLInstanceID of the hop-by-hop
route being measured. If the route being measured is a source
route, this field MUST be set to 10000000 on transmission and
ignored on reception.
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 Origin/Target Address fields and
the Address vector. The "Compr" field is a 4-bit unsigned integer
that indicates the number of prefix octets that are elided from
the IPv6 addresses in Origin/Target Address fields and the Address
vector. The Compr value will be 0 if full IPv6 addresses are
carried in the Origin/Target Address fields and the Address
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vector.
o Type (T): This flag is set if the MO represents a Measurement
Request. The flag is cleared if the MO is a Measurement Reply.
o Hop-by-hop (H): This flag is set if the MO travels along 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. This flag is cleared if
the MO travels along a source route specified in the Address
vector. Note that, in case the P2P route being measured lies
along a non-storing DAG, an MO message may travel along a hop-by-
hop route till it reaches the DAG's root, which then sends it
along a source route to its destination. In that case, the DAG
root will reset the H flag and also insert the source route to the
destination inside the Address vector.
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 only if T = 1, H = 1 and the RPLInstanceID field
has a local value. Otherwise, this flag MUST be cleared. 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, the
intermediate routers MUST add their IPv6 addresses (after eliding
Compr number of prefix octets) to the Address vector in the manner
specified later.
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 only if T = 1 and H = 0. Otherwise, this flag MUST be
cleared. 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 if it wants to make such a request to the target. On
receiving this request, the target MAY 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.
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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 if a hop-by-hop route is being measured (i.e., H =
1) and the origin wants to allow the intermediate routers to
generate the Measurement Reply in response to this Measurement
Request. Setting this flag may be useful in scenarios where 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
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.
o Num: This field indicates 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: An 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 contain the DODAGID value that, along
with the RPLInstanceID, uniquely identifies within the RPL domain
the hop-by-hop route being measured.
o Target Address: An IPv6 address of the target after eliding Compr
number of prefix octets.
o Address[1..Num]: A vector of IPv6 addresses (with Compr number of
prefix octets elided) representing a source route to the target:
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* 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. An
intermediate router adding its address to the Address vector
MUST ensure that its address does not already exist in the
vector.
* 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 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.
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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 in the manner described below. Additionally, 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 that carry the routing metric objects of
interest. If required, 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 as described below, the origin MUST
unicast the MO message to the next hop on the P2P route.
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;
o Accumulate Route (A): This flag MUST be cleared;
o Reverse (R): This flag MUST be cleared;
o Back Request (B): This flag MAY be set if the origin wants to
request the target to generate a Measurement Request back to
itself;
o Intermediate Reply (I): This flag MAY be set if the origin wants
to permit the intermediate routers to generate the Measurement
Reply on the target's behalf;
o Num: This field MUST be set to zero;
o Index: This field MUST be set to zero.
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;
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o Accumulate Route (A): This flag MUST be cleared;
o Reverse (R): This flag MUST be cleared;
o Back Request (B): This flag MAY be set if the origin wants to
request the target to generate a Measurement Request back to
itself;
o Intermediate Reply (I): This flag MAY be set if the origin wants
to permit the intermediate routers to generate the Measurement
Reply on the target's behalf;
o Num: This field MUST be set to zero;
o Index: This field MUST be set to zero;
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;
o Accumulate Route (A): This flag MUST be set;
o Reverse (R): This flag MUST be cleared;
o Back Request (B): This flag MAY be set if the origin wants to
request the target to generate a Measurement Request back to
itself;
o Intermediate Reply (I): This flag MAY be set if the origin wants
to permit the intermediate routers to generate the Measurement
Reply on the target's behalf;
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 set to zero;
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;
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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 RPLInstanceID: This field MUST be set to 10000000;
o Hop-by-hop (H): This flag MUST be cleared;
o Accumulate Route (A): This flag MUST be cleared;
o Reverse (R): This flag MUST be set 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;
o Back Request (B): This flag MAY be set if the origin wants to
request the target to generate a Measurement Request back to
itself;
o Intermediate Reply (I): This flag MUST be cleared.
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
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 origin'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.
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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 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.
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 not, 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 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.
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.
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5.1. Determining Next Hop For An MO Measuring A Source Route
In case the received MO is measuring a source route (H=0), the router
MUST 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. An MO message MUST NOT leave
the RPL domain where it originated. Hence, an intermediate router
MUST discard an MO message traveling along a source route if the next
hop on the way does not lie within the RPL domain.
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 DODAGID (same as 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.
o If the router is the root of the non-storing DAG along which the
received MO message has been traveling, the router MUST do the
following:
* Reset the H, A and R flags.
* Insert 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;
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+ 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 IPv6 addresses listed as the Target Address, it
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.
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 if desired.
The target MUST generate a Measurement Reply 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, the target MAY reverse the source route contained in the
Address vector and use it to send the Measurement Reply back to
the origin.
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o If the Measurement Request traveled along a source route and the R
flag inside the received message is set, 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 is set in the received Measurement Request, 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 IPv6
addresses is listed as the Origin Address. If yes, the router 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 SHOULD examine the routing metric objects inside the
Metric 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 MAY 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 bogus 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:
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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 domain where it is originated. Hence, any
security problems associated with the mechanism would be limited
to the RPL domain where the MO message is generated.
o 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 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
rule protect the network against some of the security concerns
even if a compromised node inserts the Address vector inside the
MO message.
9. IANA Considerations
IANA is requested to allocate a new code point in the "RPL Control
Codes" registry for the "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 Pascal Thubert,
Richard Kelsey and Zach Shelby in the development of this document.
11. References
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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., Cragie,
R., and J. Martocci, "Reactive Discovery of Point-to-Point
Routes in Low Power and Lossy Networks",
draft-ietf-roll-p2p-rpl-04 (work in progress), July 2011.
[I-D.ietf-roll-routing-metrics]
Vasseur, J., Kim, M., Pister, K., Dejean, N., and D.
Barthel, "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]
Winter, T., Thubert, P., Brandt, A., Clausen, T., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., and J.
Vasseur, "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.
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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/
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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