rfc9033.original   rfc9033.txt 
6TiSCH T. Chang, Ed. Internet Engineering Task Force (IETF) T. Chang, Ed.
Internet-Draft M. Vucinic Request for Comments: 9033 M. Vučinić
Intended status: Standards Track Inria Category: Standards Track Inria
Expires: March 16, 2021 X. Vilajosana ISSN: 2070-1721 X. Vilajosana
Universitat Oberta de Catalunya Universitat Oberta de Catalunya
S. Duquennoy S. Duquennoy
RISE SICS RISE SICS
D. Dujovne D. Dujovne
Universidad Diego Portales Universidad Diego Portales
September 12, 2020 May 2021
6TiSCH Minimal Scheduling Function (MSF) 6TiSCH Minimal Scheduling Function (MSF)
draft-ietf-6tisch-msf-18
Abstract Abstract
This specification defines the 6TiSCH Minimal Scheduling Function This specification defines the "IPv6 over the TSCH mode of IEEE
(MSF). This Scheduling Function describes both the behavior of a 802.15.4" (6TiSCH) Minimal Scheduling Function (MSF). This
node when joining the network, and how the communication schedule is Scheduling Function describes both the behavior of a node when
managed in a distributed fashion. MSF is built upon the 6TiSCH joining the network and how the communication schedule is managed in
Operation Sublayer Protocol (6P) and the Minimal Security Framework a distributed fashion. MSF is built upon the 6TiSCH Operation
for 6TiSCH. Sublayer Protocol (6P) and the minimal security framework for 6TiSCH.
Requirements Language
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on March 16, 2021. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9033.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Interface to the Minimal 6TiSCH Configuration . . . . . . . . 4 1.1. Requirements Language
3. Autonomous Cells . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Related Documents
4. Node Behavior at Boot . . . . . . . . . . . . . . . . . . . . 6 2. Interface to the Minimal 6TiSCH Configuration
4.1. Start State . . . . . . . . . . . . . . . . . . . . . . . 6 3. Autonomous Cells
4.2. Step 1 - Choosing Frequency . . . . . . . . . . . . . . . 7 4. Node Behavior at Boot
4.3. Step 2 - Receiving EBs . . . . . . . . . . . . . . . . . 7 4.1. Start State
4.4. Step 3 - Setting up Autonomous Cells for the Join 4.2. Step 1 - Choosing Frequency
Process . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Step 2 - Receiving EBs
4.5. Step 4 - Acquiring a RPL Rank . . . . . . . . . . . . . . 8 4.4. Step 3 - Setting up Autonomous Cells for the Join Process
4.6. Step 5 - Setting up first Tx negotiated Cells . . . . . . 8 4.5. Step 4 - Acquiring a RPL Rank
4.7. Step 6 - Send EBs and DIOs . . . . . . . . . . . . . . . 8 4.6. Step 5 - Setting up First Tx Negotiated Cells
4.8. End State . . . . . . . . . . . . . . . . . . . . . . . . 8 4.7. Step 6 - Sending EBs and DIOs
5. Rules for Adding/Deleting Cells . . . . . . . . . . . . . . . 9 4.8. End State
5.1. Adapting to Traffic . . . . . . . . . . . . . . . . . . . 9 5. Rules for Adding and Deleting Cells
5.2. Switching Parent . . . . . . . . . . . . . . . . . . . . 11 5.1. Adapting to Traffic
5.3. Handling Schedule Collisions . . . . . . . . . . . . . . 11 5.2. Switching Parent
6. 6P SIGNAL command . . . . . . . . . . . . . . . . . . . . . . 13 5.3. Handling Schedule Collisions
7. Scheduling Function Identifier . . . . . . . . . . . . . . . 13 6. 6P SIGNAL Command
8. Rules for CellList . . . . . . . . . . . . . . . . . . . . . 13 7. Scheduling Function Identifier
9. 6P Timeout Value . . . . . . . . . . . . . . . . . . . . . . 14 8. Rules for CellList
10. Rule for Ordering Cells . . . . . . . . . . . . . . . . . . . 14 9. 6P Timeout Value
11. Meaning of the Metadata Field . . . . . . . . . . . . . . . . 14 10. Rule for Ordering Cells
12. 6P Error Handling . . . . . . . . . . . . . . . . . . . . . . 14 11. Meaning of the Metadata Field
13. Schedule Inconsistency Handling . . . . . . . . . . . . . . . 15 12. 6P Error Handling
14. MSF Constants . . . . . . . . . . . . . . . . . . . . . . . . 15 13. Schedule Inconsistency Handling
15. MSF Statistics . . . . . . . . . . . . . . . . . . . . . . . 16 14. MSF Constants
16. Security Considerations . . . . . . . . . . . . . . . . . . . 16 15. MSF Statistics
17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 16. Security Considerations
17.1. MSF Scheduling Function Identifiers . . . . . . . . . . 18 17. IANA Considerations
18. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18 17.1. MSF Scheduling Function Identifiers
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 18. References
19.1. Normative References . . . . . . . . . . . . . . . . . . 18 18.1. Normative References
19.2. Informative References . . . . . . . . . . . . . . . . . 20 18.2. Informative References
Appendix A. Example of Implementation of SAX hash function . . . 20 Appendix A. Example Implementation of the SAX Hash Function
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 Contributors
Authors' Addresses
1. Introduction 1. Introduction
The 6TiSCH Minimal Scheduling Function (MSF), defined in this The 6TiSCH Minimal Scheduling Function (MSF), defined in this
specification, is a 6TiSCH Scheduling Function (SF). The role of an specification, is a 6TiSCH Scheduling Function (SF). The role of an
SF is entirely defined in [RFC8480]. This specification complements SF is entirely defined in [RFC8480]. This specification complements
[RFC8480] by providing the rules of when to add/delete cells in the [RFC8480] by providing the rules of when to add and delete cells in
communication schedule. This specification satisfies all the the communication schedule. This specification satisfies all the
requirements for an SF listed in Section 4.2 of [RFC8480]. requirements for an SF listed in Section 4.2 of [RFC8480].
MSF builds on top of the following specifications: the Minimal IPv6 MSF builds on top of the following specifications: "Minimal IPv6 over
over the TSCH Mode of IEEE 802.15.4e (6TiSCH) Configuration the TSCH Mode of IEEE 802.15.4e (6TiSCH) Configuration" [RFC8180],
[RFC8180], the 6TiSCH Operation Sublayer Protocol (6P) [RFC8480], and "6TiSCH Operation Sublayer (6top) Protocol (6P)" [RFC8480], and
the Minimal Security Framework for 6TiSCH "Constrained Join Protocol (CoJP) for 6TiSCH" [RFC9031].
[I-D.ietf-6tisch-minimal-security].
MSF defines both the behavior of a node when joining the network, and MSF defines both the behavior of a node when joining the network, and
how the communication schedule is managed in a distributed fashion. how the communication schedule is managed in a distributed fashion.
When a node running MSF boots up, it joins the network by following When a node running MSF boots up, it joins the network by following
the 6 steps described in Section 4. The end state of the join the six steps described in Section 4. The end state of the join
process is that the node is synchronized to the network, has mutually process is that the node is synchronized to the network, has mutually
authenticated with the network, has identified a routing parent, and authenticated with the network, has identified a routing parent, and
has scheduled one negotiated Tx cell (defined in Section 5.1) to/from has scheduled one negotiated Tx cell (defined in Section 5.1) to/from
its routing parent. After the join process, the node can its routing parent. After the join process, the node can
continuously add/delete/relocate cells, as described in Section 5. continuously add, delete, and relocate cells as described in
It does so for 3 reasons: to match the link-layer resources to the Section 5. It does so for three reasons: to match the link-layer
traffic, to handle changing parent and to handle a schedule resources to the traffic, to handle changing parent, and to handle a
collision. schedule collision.
MSF works closely with the IPv6 Routing Protocol for Low-Power and MSF works closely with the IPv6 Routing Protocol for Low-Power and
Lossy Networks (RPL), specifically the routing parent defined in Lossy Networks (RPL), specifically the routing parent defined in
[RFC6550]. This specification only describes how MSF works with the [RFC6550]. This specification only describes how MSF works with the
routing parent; this parent is referred to as the "selected parent". routing parent; this parent is referred to as the "selected parent".
The activity of MSF towards the single routing parent is called a The activity of MSF towards the single routing parent is called a
"MSF session". Though the performance of MSF is evaluated only when "MSF session". Though the performance of MSF is evaluated only when
the "selected parent" represents the node's preferred parent, there the "selected parent" represents the node's preferred parent, there
should be no restrictions to use multiple MSF sessions, one per should be no restrictions to use multiple MSF sessions, one per
parent. The distribution of traffic over multiple parents is a parent. The distribution of traffic over multiple parents is a
routing decision that is out of scope for MSF. routing decision that is out of scope for MSF.
MSF is designed to operate in a wide range of application domains. MSF is designed to operate in a wide range of application domains.
It is optimized for applications with regular upstream traffic, from It is optimized for applications with regular upstream traffic, from
the nodes to the Destination-Oriented Directed Acyclic Graph (DODAG the nodes to the Destination-Oriented Directed Acyclic Graph (DODAG)
[RFC6550]) root. root [RFC6550].
This specification follows the recommended structure of an SF This specification follows the recommended structure of an SF
specification, given in Appendix A of [RFC8480], with the following specification, given in Appendix A of [RFC8480], with the following
adaptations: adaptations:
* We have reordered some sections, in particular to have the section * We have reordered some sections, in particular to have the section
on the node behavior at boot (Section 4) appear early in this on the node behavior at boot (Section 4) appear early in this
specification. specification.
* We added sections on the interface to the minimal 6TiSCH * We added sections on the interface to the minimal 6TiSCH
configuration (Section 2), the use of the SIGNAL command configuration (Section 2), the use of the SIGNAL command
(Section 6), the MSF constants (Section 14) and the MSF statistics (Section 6), the MSF constants (Section 14), and the MSF
(Section 15). statistics (Section 15).
1.1. Requirements Language
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
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Related Documents
This specification uses messages and variables defined in IEEE Std
802.15.4-2015 [IEEE802154]. It is expected that those resources will
remain in the future versions of IEEE Std 802.15.4; in which case,
this specification also applies to those future versions. In the
remainder of the document, we use [IEEE802154] to refer to IEEE Std
802.15.4-2015 as well as future versions of IEEE Std 802.15.4 that
remain compatible.
2. Interface to the Minimal 6TiSCH Configuration 2. Interface to the Minimal 6TiSCH Configuration
In a TSCH network, time is sliced up into time slots. The time slots In a Time-Slotted Channel Hopping (TSCH) network, time is sliced up
are grouped as one or multiple slotframes which repeat over time. into time slots. The time slots are grouped as one or multiple
The TSCH schedule instructs a node what to do at each time slot, such slotframes that repeat over time. The TSCH schedule instructs a node
as transmit, receive or sleep [RFC7554]. In case of a slot to what to do at each time slot, such as transmit, receive, or sleep
transmit or receive, a channel is assigned to the time slot. The [RFC7554]. For time slots for transmitting or receiving, a channel
tuple (slot, channel) is indicated as a cell of TSCH schedule. MSF is assigned to the time slot. The tuple (slot, channel) is indicated
is one of the policies defining how to manage the TSCH schedule. as a cell of the TSCH schedule. MSF is one of the policies defining
how to manage the TSCH schedule.
A node implementing MSF SHOULD implement the Minimal 6TiSCH A node implementing MSF SHOULD implement the minimal 6TiSCH
Configuration [RFC8180], which defines the "minimal cell", a single configuration [RFC8180], which defines the "minimal cell", a single
shared cell providing minimal connectivity between the nodes in the shared cell providing minimal connectivity between the nodes in the
network. The MSF implementation provided in this specification is network. The MSF implementation provided in this specification is
based on the implementation of the Minimal 6TiSCH Configuration. based on the implementation of the minimal 6TiSCH configuration.
However, an implementor MAY implement MSF based on other However, an implementor MAY implement MSF based on other
specifications as long as the specification defines a way to specifications as long as the specification defines a way to
advertise the EB/DIO among the network. advertise the Enhanced Beacons (EBs) and DODAG Information Objects
(DIOs) among the network.
MSF uses the minimal cell for broadcast frames such as Enhanced MSF uses the minimal cell for broadcast frames such as Enhanced
Beacons (EBs) [IEEE802154] and broadcast DODAG Information Objects Beacons (EBs) [IEEE802154] and broadcast DODAG Information Objects
(DIOs) [RFC6550]. Cells scheduled by MSF are meant to be used only (DIOs) [RFC6550]. Cells scheduled by MSF are meant to be used only
for unicast frames. for unicast frames.
To ensure there is enough bandwidth available on the minimal cell, a To ensure there is enough bandwidth available on the minimal cell, a
node implementing MSF SHOULD enforce some rules for limiting the node implementing MSF SHOULD enforce some rules for limiting the
traffic of broadcast frames. For example, the overall broadcast traffic of broadcast frames. For example, the overall broadcast
traffic among the node and its neighbors SHOULD NOT exceed 1/3 of the traffic among the node and its neighbors SHOULD NOT exceed one-third
bandwidth of minimal cell. One of the algorithms that fulfills this of the bandwidth of minimal cell. One of the algorithms that
requirement is the Trickle timer defined in [RFC6206] which is fulfills this requirement is the Trickle timer defined in [RFC6206],
applied on DIO messages [RFC6550]. However, any such algorithm of which is applied to DIO messages [RFC6550]. However, any such
limiting the broadcast traffic to meet those rules is implementation- algorithm of limiting the broadcast traffic to meet those rules is
specific and is out of the scope of MSF. implementation-specific and is out of the scope of MSF.
3 slotframes are used in MSF. MSF schedules autonomous cells at Three slotframes are used in MSF. MSF schedules autonomous cells at
Slotframe 1 (Section 3) and 6P negotiated cells at Slotframe 2 Slotframe 1 (Section 3) and 6P negotiated cells at Slotframe 2
(Section 5) ,while Slotframe 0 is used for the bootstrap traffic as (Section 5), while Slotframe 0 is used for the bootstrap traffic as
defined in the Minimal 6TiSCH Configuration. The same slotframe defined in the minimal 6TiSCH configuration. The same slotframe
length for Slotframe 0, 1 and 2 is RECOMMENDED. Thus it is possible length for Slotframe 0, 1, and 2 is RECOMMENDED. Thus it is possible
to avoid the scheduling collision between the autonomous cells and 6P to avoid the scheduling collision between the autonomous cells and 6P
negotiated cells (Section 3). The default slotframe length negotiated cells (Section 3). The default slotframe length
(SLOTFRAME_LENGTH) is RECOMMENDED for Slotframe 0, 1 and 2, although (SLOTFRAME_LENGTH) is RECOMMENDED for Slotframe 0, 1, and 2, although
any value can be advertised in the EBs. any value can be advertised in the EBs.
3. Autonomous Cells 3. Autonomous Cells
MSF nodes initialize Slotframe 1 with a set of default cells for MSF nodes initialize Slotframe 1 with a set of default cells for
unicast communication with their neighbors. These cells are called unicast communication with their neighbors. These cells are called
'autonomous cells', because they are maintained autonomously by each "autonomous cells", because they are maintained autonomously by each
node without negotiation through 6P. Cells scheduled by 6P node without negotiation through 6P. Cells scheduled by 6P
transaction are called 'negotiated cells' which are reserved on Transaction are called "negotiated cells", which are reserved on
Slotframe 2. How to schedule negotiated cells is detailed in Slotframe 2. How to schedule negotiated cells is detailed in
Section 5. There are two types of autonomous cells: Section 5. There are two types of autonomous cells:
* Autonomous Rx Cell (AutoRxCell), one cell at a Autonomous Rx Cell (AutoRxCell): One cell at a
[slotOffset,channelOffset] computed as a hash of the EUI64 of the [slotOffset,channelOffset] computed as a hash of the 64-bit
node itself (detailed next). Its cell options bits are assigned Extended Unique Identifier (EUI-64) of the node itself (detailed
as TX=0, RX=1, SHARED=0. next). Its cell options bits are assigned as TX=0, RX=1,
* Autonomous Tx Cell (AutoTxCell), one cell at a SHARED=0.
[slotOffset,channelOffset] computed as a hash of the layer 2 EUI64
destination address in the unicast frame to be transmitted Autonomous Tx Cell (AutoTxCell): One cell at a
[slotOffset,channelOffset] computed as a hash of the Layer 2
EUI-64 destination address in the unicast frame to be transmitted
(detailed in Section 4.4). Its cell options bits are assigned as (detailed in Section 4.4). Its cell options bits are assigned as
TX=1, RX=0, SHARED=1. TX=1, RX=0, SHARED=1.
To compute a [slotOffset,channelOffset] from an EUI64 address, nodes To compute a [slotOffset,channelOffset] from an EUI-64 address, nodes
MUST use the hash function SAX as defined in Section 2 of MUST use the hash function SAX as defined in Section 2 of
[SAX-DASFAA] with consistent input parameters, for example, those [SAX-DASFAA] with consistent input parameters, for example, those
defined in Appendix A. The coordinates are computed to distribute defined in Appendix A. The coordinates are computed to distribute
the cells across all channel offsets, and all but the first slot the cells across all channel offsets, and all but the first slot
offset of Slotframe 1. The first time offset is skipped to avoid offset of Slotframe 1. The first time offset is skipped to avoid
colliding with the minimal cell in Slotframe 0. The slot coordinates colliding with the minimal cell in Slotframe 0. The slot coordinates
derived from a given EUI64 address are computed as follows: derived from a given EUI-64 address are computed as follows:
* slotOffset(MAC) = 1 + hash(EUI64, length(Slotframe_1) - 1) slotOffset(MAC) = 1 + hash(EUI64, length(Slotframe_1) - 1)
* channelOffset(MAC) = hash(EUI64, NUM_CH_OFFSET)
channelOffset(MAC) = hash(EUI64, NUM_CH_OFFSET)
The second input parameter defines the maximum return value of the The second input parameter defines the maximum return value of the
hash function. Other optional parameters defined in SAX determine hash function. Other optional parameters defined in SAX determine
the performance of SAX hash function. Those parameters could be the performance of SAX hash function. Those parameters could be
broadcasted in EB frame or pre-configured. For interoperability broadcast in an EB frame or preconfigured. For interoperability
purposes, the values of those parameters can be referred from purposes, Appendix A provides the reference values of those
Appendix A. parameters.
AutoTxCell is not permanently installed in the schedule but added/ AutoTxCell is not permanently installed in the schedule but is added
deleted on demand when there is a frame to be sent. Throughout the or deleted on demand when there is a frame to be sent. Throughout
network lifetime, nodes maintain the autonomous cells as follows: the network lifetime, nodes maintain the autonomous cells as follows:
* Add an AutoTxCell to the layer 2 destination address which is * Add an AutoTxCell to the Layer 2 destination address, which is
indicated in a frame when there is no 6P negotiated Tx cell in indicated in a frame when there is no 6P negotiated Tx cell in the
schedule for that frame to transmit. schedule for that frame to transmit.
* Remove an AutoTxCell when: * Remove an AutoTxCell when:
- there is no frame to transmit on that cell, or - there is no frame to transmit on that cell, or
- there is at least one 6P negotiated Tx cell in the schedule for - there is at least one 6P negotiated Tx cell in the schedule for
the frames to transmit. the frames to transmit.
The AutoRxCell MUST always remain scheduled after synchronization. The AutoRxCell MUST always remain scheduled after synchronization.
6P CLEAR MUST NOT erase any autonomous cells. 6P CLEAR MUST NOT erase any autonomous cells.
Because of hash collisions, there will be cases that the AutoTxCell Because of hash collisions, there will be cases that the AutoTxCell
and AutoRxCell are scheduled at the same slot offset and/or channel and AutoRxCell are scheduled at the same slot offset and/or channel
offset. In such cases, AutoTxCell always take precedence over offset. In such cases, AutoTxCell always take precedence over
AutoRxCell. Notice AutoTxCell is a shared type cell which applies AutoRxCell. Notice AutoTxCell is a shared type cell that applies a
backs-off mechanism. When the AutoTxCell and AutoRxCell collide, back-off mechanism. When the AutoTxCell and AutoRxCell collide,
AutoTxCell takes precedence if there is a packet to transmit. When AutoTxCell takes precedence if there is a packet to transmit. When
in a back-off period, AutoRxCell is used. In case of conflicting in a back-off period, AutoRxCell is used. In the case of conflict
with a negotiated cell, autonomous cells take precedence over with a negotiated cell, autonomous cells take precedence over
negotiated cells, which is stated in [IEEE802154]. However, when the negotiated cells, which is stated in [IEEE802154]. However, when the
Slotframe 0, 1 and 2 use the same length value, it is possible for a Slotframe 0, 1, and 2 use the same length value, it is possible for a
negotiated cell to avoid the collision with AutoRxCell. Hence, the negotiated cell to avoid the collision with AutoRxCell. Hence, the
same slotframe length for Slotframe 0, 1 and 2 is RECOMMENDED. same slotframe length for Slotframe 0, 1, and 2 is RECOMMENDED.
4. Node Behavior at Boot 4. Node Behavior at Boot
This section details the behavior the node SHOULD follow from the This section details the behavior the node SHOULD follow from the
moment it is switched on, until it has successfully joined the moment it is switched on until it has successfully joined the
network. Alternative behaviors may be involved, for example, when network. Alternative behaviors may be involved, for example, when
alternative security solutions are used for the network. Section 4.1 alternative security solutions are used for the network. Section 4.1
details the start state; Section 4.8 details the end state. The details the start state; Section 4.8 details the end state. The
other sections detail the 6 steps of the joining process. We use the other sections detail the six steps of the joining process. We use
term "pledge" and "joined node", as defined in the term "pledge" and "joined node", as defined in [RFC9031].
[I-D.ietf-6tisch-minimal-security].
4.1. Start State 4.1. Start State
A node implementing MSF SHOULD implement the Constrained Join A node implementing MSF SHOULD implement the Constrained Join
Protocol (CoJP) for 6TiSCH [I-D.ietf-6tisch-minimal-security]. As a Protocol (CoJP) for 6TiSCH [RFC9031]. As a corollary, this means
corollary, this means that a pledge, before being switched on, may be that a pledge, before being switched on, may be preconfigured with
pre-configured with the Pre-Shared Key (PSK) for joining, as well as the Pre-Shared Key (PSK) for joining, as well as any other
any other configuration detailed in configuration detailed in [RFC9031]. This is not necessary if the
([I-D.ietf-6tisch-minimal-security]). This is not necessary if the node implements a security solution that is not based on PSKs, such
node implements a security solution not based on PSKs, such as as [ZEROTOUCH-JOIN].
([I-D.ietf-6tisch-dtsecurity-zerotouch-join]).
4.2. Step 1 - Choosing Frequency 4.2. Step 1 - Choosing Frequency
When switched on, the pledge randomly chooses a frequency from the When switched on, the pledge randomly chooses a frequency from the
channels that the network cycles amongst, and starts listening for channels through which the network cycles and starts listening for
EBs on that frequency. EBs on that frequency.
4.3. Step 2 - Receiving EBs 4.3. Step 2 - Receiving EBs
Upon receiving the first EB, the pledge continues listening for Upon receiving the first EB, the pledge continues listening for
additional EBs to learn: additional EBs to learn:
1. the number of neighbors N in its vicinity 1. the number of neighbors N in its vicinity, and
2. which neighbor to choose as a Join Proxy (JP) for the joining 2. which neighbor to choose as a Join Proxy (JP) for the joining
process process.
After having received the first EB, a node MAY keep listening for at After having received the first EB, a node MAY keep listening for at
most MAX_EB_DELAY seconds or until it has received EBs from most MAX_EB_DELAY seconds or until it has received EBs from
NUM_NEIGHBOURS_TO_WAIT distinct neighbors. This behavior is defined NUM_NEIGHBOURS_TO_WAIT distinct neighbors. This behavior is defined
in [RFC8180]. in [RFC8180].
During this step, the pledge only gets synchronized when it received During this step, the pledge only gets synchronized when it has
enough EB from the network it wishes to join. How to decide whether received enough EB from the network it wishes to join. How to decide
an EB originates from a node from the network it wishes to join is whether an EB originates from a node from the network it wishes to
implementation-specific, but MAY involve filtering EBs by the PAN ID join is implementation-specific, but MAY involve filtering EBs by the
field it contains, the presence and contents of the IE defined in PANID field it contains, the presence and contents of the Information
[I-D.ietf-6tisch-enrollment-enhanced-beacon], or the key used to Element (IE) defined in [RFC9032], or the key used to authenticate
authenticate it. it.
The decision of which neighbor to use as a JP is implementation- The decision of which neighbor to use as a JP is implementation-
specific, and discussed in [I-D.ietf-6tisch-minimal-security]. specific and is discussed in [RFC9031].
4.4. Step 3 - Setting up Autonomous Cells for the Join Process 4.4. Step 3 - Setting up Autonomous Cells for the Join Process
After having selected a JP, a node generates a Join Request and After having selected a JP, a node generates a Join Request and
installs an AutoTxCell to the JP. The Join Request is then sent by installs an AutoTxCell to the JP. The Join Request is then sent by
the pledge to its selected JP over the AutoTxCell. The AutoTxCell is the pledge to its selected JP over the AutoTxCell. The AutoTxCell is
removed by the pledge when the Join Request is sent out. The JP removed by the pledge when the Join Request is sent out. The JP
receives the Join Request through its AutoRxCell. Then it forwards receives the Join Request through its AutoRxCell. Then it forwards
the Join Request to the join registrar/coordinator (JRC), possibly the Join Request to the Join Registrar/Coordinator (JRC), possibly
over multiple hops, over the 6P negotiated Tx cells. Similarly, the over multiple hops, over the 6P negotiated Tx cells. Similarly, the
JRC sends the Join Response to the JP, possibly over multiple hops, JRC sends the Join Response to the JP, possibly over multiple hops,
over AutoTxCells or the 6P negotiated Tx cells. When the JP received over AutoTxCells or the 6P negotiated Tx cells. When the JP receives
the Join Response from the JRC, it installs an AutoTxCell to the the Join Response from the JRC, it installs an AutoTxCell to the
pledge and sends that Join Response to the pledge over AutoTxCell. pledge and sends that Join Response to the pledge over AutoTxCell.
The AutoTxCell is removed by the JP when the Join Response is sent The AutoTxCell is removed by the JP when the Join Response is sent
out. The pledge receives the Join Response from its AutoRxCell, out. The pledge receives the Join Response from its AutoRxCell,
thereby learns the keying material used in the network, as well as thereby learns the keying material used in the network, as well as
other configuration settings, and becomes a "joined node". other configuration settings, and becomes a "joined node".
When 6LoWPAN Neighbor Discovery ([RFC8505]) (ND) is implemented, the When 6LoWPAN Neighbor Discovery (ND) [RFC8505] is implemented, the
unicast packets used by ND are sent on the AutoTxCell. The specific unicast packets used by ND are sent on the AutoTxCell. The specific
process how the ND works during the Join process is detailed in process how the ND works during the join process is detailed in
[I-D.ietf-6tisch-architecture]. [RFC9030].
4.5. Step 4 - Acquiring a RPL Rank 4.5. Step 4 - Acquiring a RPL Rank
Per [RFC6550], the joined node receives DIOs, computes its own Rank, Per [RFC6550], the joined node receives DIOs, computes its own Rank,
and selects a routing parent. and selects a routing parent.
4.6. Step 5 - Setting up first Tx negotiated Cells 4.6. Step 5 - Setting up First Tx Negotiated Cells
Once it has selected a routing parent, the joined node MUST generate Once it has selected a routing parent, the joined node MUST generate
a 6P ADD Request and install an AutoTxCell to that parent. The 6P a 6P ADD Request and install an AutoTxCell to that parent. The 6P
ADD Request is sent out through the AutoTxCell, containing the ADD Request is sent out through the AutoTxCell, containing the
following fields: following fields:
* CellOptions: set to TX=1,RX=0,SHARED=0 CellOptions: Set to TX=1, RX=0, SHARED=0.
* NumCells: set to 1
* CellList: at least 5 cells, chosen according to Section 8 NumCells: Set to 1.
CellList: At least 5 cells, chosen according to Section 8.
The joined node removes the AutoTxCell to the selected parent when The joined node removes the AutoTxCell to the selected parent when
the 6P Request is sent out. That parent receives the 6P ADD Request the 6P Request is sent out. That parent receives the 6P ADD Request
from its AutoRxCell. Then it generates a 6P ADD Response and from its AutoRxCell. Then it generates a 6P ADD Response and
installs an AutoTxCell to the joined node. When the parent sends out installs an AutoTxCell to the joined node. When the parent sends out
the 6P ADD Response, it MUST remove that AutoTxCell. The joined node the 6P ADD Response, it MUST remove that AutoTxCell. The joined node
receives the 6P ADD Response from its AutoRxCell and completes the 6P receives the 6P ADD Response from its AutoRxCell and completes the 6P
transaction. In case the 6P ADD transaction failed, the node MUST Transaction. In the case that the 6P ADD transaction failed, the
issue another 6P ADD Request and repeat until the Tx cell is node MUST issue another 6P ADD Request and repeat until the Tx cell
installed to the parent. is installed to the parent.
4.7. Step 6 - Send EBs and DIOs 4.7. Step 6 - Sending EBs and DIOs
The node starts sending EBs and DIOs on the minimal cell, while The node starts sending EBs and DIOs on the minimal cell, while
following the transmit rules for broadcast frames from Section 2. following the transmit rules for broadcast frames from Section 2.
4.8. End State 4.8. End State
For a new node, the end state of the joining process is: At the end state of the joining process, a new node:
* it is synchronized to the network * is synchronized to the network,
* it is using the link-layer keying material it learned through the
secure joining process
* it has selected one neighbor as its routing parent
* it has one AutoRxCell
* it has one negotiated Tx cell to the selected parent
* it starts to send DIOs, potentially serving as a router for other
nodes' traffic
* it starts to send EBs, potentially serving as a JP for new pledges
5. Rules for Adding/Deleting Cells * is using the link-layer keying material it learned through the
secure joining process,
* has selected one neighbor as its routing parent,
* has one AutoRxCell,
* has one negotiated Tx cell to the selected parent,
* starts to send DIOs, potentially serving as a router for other
nodes' traffic, and
* starts to send EBs, potentially serving as a JP for new pledges.
5. Rules for Adding and Deleting Cells
Once a node has joined the 6TiSCH network, it adds/deletes/relocates Once a node has joined the 6TiSCH network, it adds/deletes/relocates
cells with the selected parent for three reasons: cells with the selected parent for three reasons:
* to match the link-layer resources to the traffic between the node * to match the link-layer resources to the traffic between the node
and the selected parent (Section 5.1) and the selected parent (Section 5.1),
* to handle switching parent or(Section 5.2)
* to handle a schedule collision (Section 5.3)
Those cells are called 'negotiated cells' as they are scheduled * to handle switching the parent (Section 5.2), or
through 6P, negotiated with the node's parent. Without specific
declaration, all cells mentioned in this section are negotiated cells * to handle a schedule collision (Section 5.3).
and they are installed at Slotframe 2.
These cells are called "negotiated cells" as they are scheduled
through 6P and negotiated with the node's parent. Without specific
declaration, all cells mentioned in this section are negotiated
cells, and they are installed at Slotframe 2.
5.1. Adapting to Traffic 5.1. Adapting to Traffic
A node implementing MSF MUST implement the behavior described in this A node implementing MSF MUST implement the behavior described in this
section. section.
The goal of MSF is to manage the communication schedule in the 6TiSCH The goal of MSF is to manage the communication schedule in the 6TiSCH
schedule in a distributed manner. For a node, this translates into schedule in a distributed manner. For a node, this translates into
monitoring the current usage of the cells it has to one of its monitoring the current usage of the cells it has to one of its
neighbors, in most cases to the selected parent. neighbors, in most cases to the selected parent.
skipping to change at page 9, line 40 skipping to change at line 446
The goal of MSF is to manage the communication schedule in the 6TiSCH The goal of MSF is to manage the communication schedule in the 6TiSCH
schedule in a distributed manner. For a node, this translates into schedule in a distributed manner. For a node, this translates into
monitoring the current usage of the cells it has to one of its monitoring the current usage of the cells it has to one of its
neighbors, in most cases to the selected parent. neighbors, in most cases to the selected parent.
* If the node determines that the number of link-layer frames it is * If the node determines that the number of link-layer frames it is
attempting to exchange with the selected parent per unit of time attempting to exchange with the selected parent per unit of time
is larger than the capacity offered by the TSCH negotiated cells is larger than the capacity offered by the TSCH negotiated cells
it has scheduled with it, the node issues a 6P ADD command to that it has scheduled with it, the node issues a 6P ADD command to that
parent to add cells to the TSCH schedule. parent to add cells to the TSCH schedule.
* If the traffic is lower than the capacity, the node issues a 6P * If the traffic is lower than the capacity, the node issues a 6P
DELETE command to that parent to delete cells from the TSCH DELETE command to that parent to delete cells from the TSCH
schedule. schedule.
The node MUST maintain two separate pairs of the following counters The node MUST maintain two separate pairs of the following counters
for the selected parent, one for the negotiated Tx cells to that for the selected parent: one for the negotiated Tx cells to that
parent and one for the negotiated Rx cells to that parent. parent and one for the negotiated Rx cells to that parent.
NumCellsElapsed : Counts the number of negotiated cells that have NumCellsElapsed: Counts the number of negotiated cells that have
elapsed since the counter was initialized. This counter is elapsed since the counter was initialized. This counter is
initialized at 0. When the current cell is declared as a initialized at 0. When the current cell is declared as a
negotiated cell to the selected parent, NumCellsElapsed is negotiated cell to the selected parent, NumCellsElapsed is
incremented by exactly 1, regardless of whether the cell is used incremented by exactly 1, regardless of whether the cell is used
to transmit/receive a frame. to transmit or receive a frame.
NumCellsUsed: Counts the number of negotiated cells that have been NumCellsUsed: Counts the number of negotiated cells that have been
used. This counter is initialized at 0. NumCellsUsed is used. This counter is initialized at 0. NumCellsUsed is
incremented by exactly 1 when, during a negotiated cell to the incremented by exactly 1 when, during a negotiated cell to the
selected parent, either of the following happens: selected parent, either of the following happens:
* The node sends a frame to the parent. The counter increments
regardless of whether a link-layer acknowledgment was received
or not.
* The node receives a valid frame from the parent. The counter
increments only when the frame is a valid IEEE802.15.4 frame.
The cell option of cells listed in CellList in 6P Request frame * The node sends a frame to the parent. The counter increments
regardless of whether a link-layer acknowledgment was received
or not.
* The node receives a valid frame from the parent. The counter
increments only when a valid frame per [IEEE802154] is received
by the node from its parent.
The cell option of cells listed in CellList in a 6P Request frame
SHOULD be either (Tx=1, Rx=0) only or (Tx=0, Rx=1) only. Both SHOULD be either (Tx=1, Rx=0) only or (Tx=0, Rx=1) only. Both
NumCellsElapsed and NumCellsUsed counters can be used for both type NumCellsElapsed and NumCellsUsed counters can be used for both types
of negotiated cells. of negotiated cells.
As there is no negotiated Rx Cell installed at initial time, the As there is no negotiated Rx cell installed at initial time, the
AutoRxCell is taken into account as well for downstream traffic AutoRxCell is taken into account as well for downstream traffic
adaptation. In this case: adaptation. In this case:
* NumCellsElapsed is incremented by exactly 1 when the current cell * NumCellsElapsed is incremented by exactly 1 when the current cell
is AutoRxCell. is AutoRxCell.
* NumCellsUsed is incremented by exactly 1 when the node receives a * NumCellsUsed is incremented by exactly 1 when the node receives a
frame from the selected parent on AutoRxCell. frame from the selected parent on AutoRxCell.
Implementors MAY choose to create the same counters for each Implementors MAY choose to create the same counters for each neighbor
neighbor, and add them as additional statistics in the neighbor and add them as additional statistics in the neighbor table.
table.
The counters are used as follows: The counters are used as follows:
1. Both NumCellsElapsed and NumCellsUsed are initialized to 0 when 1. Both NumCellsElapsed and NumCellsUsed are initialized to 0 when
the node boots. the node boots.
2. When the value of NumCellsElapsed reaches MAX_NUM_CELLS: 2. When the value of NumCellsElapsed reaches MAX_NUM_CELLS:
* If NumCellsUsed > LIM_NUMCELLSUSED_HIGH, trigger 6P to add a
single cell to the selected parent * If NumCellsUsed is greater than LIM_NUMCELLSUSED_HIGH, trigger
* If NumCellsUsed < LIM_NUMCELLSUSED_LOW, trigger 6P to remove a 6P to add a single cell to the selected parent.
single cell to the selected parent
* Reset both NumCellsElapsed and NumCellsUsed to 0 and go to * If NumCellsUsed is less than LIM_NUMCELLSUSED_LOW, trigger 6P
step 2. to remove a single cell to the selected parent.
* Reset both NumCellsElapsed and NumCellsUsed to 0 and restart
#2.
The value of MAX_NUM_CELLS is chosen according to the traffic type of The value of MAX_NUM_CELLS is chosen according to the traffic type of
the network. Generally speaking, the larger the value MAX_NUM_CELLS the network. Generally speaking, the larger the value MAX_NUM_CELLS
is, the more accurate the cell usage is calculated. The 6P traffic is, the more accurately the cell usage is calculated. By using a
overhead using a larger value of MAX_NUM_CELLS could be reduced as larger value of MAX_NUM_CELLS, the 6P traffic overhead could be
well. Meanwhile, the latency won't increase much by using a larger reduced as well. Meanwhile, the latency won't increase much by using
value of MAX_NUM_CELLS for periodic traffic type. For bursty a larger value of MAX_NUM_CELLS for periodic traffic type. For
traffic, larger value of MAX_NUM_CELLS indeed introduces higher bursty traffic, a larger value of MAX_NUM_CELLS indeed introduces
latency. The latency caused by slight changes of traffic load can be higher latency. The latency caused by slight changes of traffic load
absolved by the additional scheduled cells. In this sense, MSF is a can be alleviated by the additional scheduled cells. In this sense,
scheduling function trading latency with energy by scheduling more MSF is a Scheduling Function that trades latency with energy by
cells than needed. Setting MAX_NUM_CELLS to a value at least 4x of scheduling more cells than needed. Setting MAX_NUM_CELLS to a value
the recent maximum number of cells used in a slot frame is at least four times the recent maximum number of cells used in a
RECOMMENDED. For example, a 2 packets/slotframe traffic load results slotframe is RECOMMENDED. For example, a two packets/slotframe
an average 4 cells scheduled (2 cells are used), using at least the traffic load results in an average of four cells scheduled (two cells
value of double number of scheduled cells (which is 8) as are used), using at least the value of double the number of scheduled
MAX_NUM_CELLS gives a good resolution on cell usage calculation. cells (which is eight) as MAX_NUM_CELLS gives a good resolution on
the cell usage calculation.
In case that a node booted or disappeared from the network, the cell In the case that a node has booted or has disappeared from the
reserved at the selected parent may be kept in the schedule forever. network, the cell reserved at the selected parent may be kept in the
A clean-up mechanism MUST be provided to resolve this issue. The schedule forever. A cleanup mechanism MUST be provided to resolve
clean-up mechanism is implementation-specific. The goal is to this issue. The cleanup mechanism is implementation-specific. The
confirm those negotiated cells are not used anymore by the associated goal is to confirm that those negotiated cells are not used anymore
neighbors and remove them from the schedule. by the associated neighbors and remove them from the schedule.
5.2. Switching Parent 5.2. Switching Parent
A node implementing MSF SHOULD implement the behavior described in A node implementing MSF SHOULD implement the behavior described in
this section. this section.
Part of its normal operation, the RPL routing protocol can have a As part of its normal operation, RPL can have a node switch parent.
node switch parent. The procedure for switching from the old parent The procedure for switching from the old parent to the new parent is
to the new parent is: the following:
1. the node counts the number of negotiated cells it has per 1. The node counts the number of negotiated cells it has per
slotframe to the old parent slotframe to the old parent.
2. the node triggers one or more 6P ADD commands to schedule the
2. The node triggers one or more 6P ADD commands to schedule the
same number of negotiated cells with same cell options to the new same number of negotiated cells with same cell options to the new
parent parent.
3. when that successfully completes, the node issues a 6P CLEAR
command to its old parent
For what type of negotiated cell should be installed first, it 3. When that successfully completes, the node issues a 6P CLEAR
depends on which traffic has the higher priority, upstream or command to its old parent.
downstream, which is application-specific and out-of-scope of MSF.
The type of negotiated cell that should be installed first depends on
which traffic has the higher priority, upstream or downstream, which
is application-specific and out of scope of MSF.
5.3. Handling Schedule Collisions 5.3. Handling Schedule Collisions
A node implementing MSF SHOULD implement the behavior described in A node implementing MSF SHOULD implement the behavior described in
this section. Other schedule collisions handling algorithm can be an this section. Other algorithms for handling schedule collisions can
alternative of the algorithm proposed in this section. be an alternative to the algorithm proposed in this section.
Since scheduling is entirely distributed, there is a non-zero Since scheduling is entirely distributed, there is a nonzero
probability that two pairs of nearby neighbor nodes schedule a probability that two pairs of nearby neighbor nodes schedule a
negotiated cell at the same [slotOffset,channelOffset] location in negotiated cell at the same [slotOffset,channelOffset] location in
the TSCH schedule. In that case, data exchanged by the two pairs may the TSCH schedule. In that case, data exchanged by the two pairs may
collide on that cell. We call this case a "schedule collision". collide on that cell. We call this case a "schedule collision".
The node MUST maintain the following counters for each negotiated Tx The node MUST maintain the following counters for each negotiated Tx
cell to the selected parent: cell to the selected parent:
NumTx: Counts the number of transmission attempts on that cell. NumTx: Counts the number of transmission attempts on that cell.
Each time the node attempts to transmit a frame on that cell, Each time the node attempts to transmit a frame on that cell,
NumTx is incremented by exactly 1. NumTx is incremented by exactly 1.
NumTxAck: Counts the number of successful transmission attempts on NumTxAck: Counts the number of successful transmission attempts on
that cell. Each time the node receives an acknowledgment for a that cell. Each time the node receives an acknowledgment for a
transmission attempt, NumTxAck is incremented by exactly 1. transmission attempt, NumTxAck is incremented by exactly 1.
Since both NumTx and NumTxAck are initialized to 0, we necessarily Since both NumTx and NumTxAck are initialized to 0, we necessarily
have NumTxAck <= NumTx. We call Packet Delivery Ratio (PDR) the have NumTxAck less than or equal to NumTx. We call Packet Delivery
ratio NumTxAck/NumTx; and represent it as a percentage. A cell with Ratio (PDR) the ratio NumTxAck/NumTx and represent it as a
PDR=50% means that half of the frames transmitted are not percentage. A cell with a PDR equal to 50% means that half of the
acknowledged. frames transmitted are not acknowledged.
Each time the node switches parent (or during the join process when Each time the node switches parent (or during the join process when
the node selects a parent for the first time), both NumTx and the node selects a parent for the first time), both NumTx and
NumTxAck MUST be reset to 0. They increment over time, as the NumTxAck MUST be reset to 0. They increment over time, as the
schedule is executed and the node sends frames to that parent. When schedule is executed, and the node sends frames to that parent. When
NumTx reaches MAX_NUMTX, both NumTx and NumTxAck MUST be divided by NumTx reaches MAX_NUMTX, both NumTx and NumTxAck MUST be divided by
2. MAX_NUMTX needs to be a power of two to avoid division error. 2. MAX_NUMTX needs to be a power of two to avoid division error.
For example, when MAX_NUMTX is set to 256, from NumTx=255 and For example, when MAX_NUMTX is set to 256, and NumTx=255 and
NumTxAck=127, the counters become NumTx=128 and NumTxAck=64 if one NumTxAck=127, the counters become NumTx=128 and NumTxAck=64 if one
frame is sent to the parent with an Acknowledgment received. This frame is sent to the parent with an acknowledgment received. This
operation does not change the value of the PDR, but allows the operation does not change the value of the PDR but allows the
counters to keep incrementing. The value of MAX_NUMTX is counters to keep incrementing. The value of MAX_NUMTX is
implementation-specific. implementation-specific.
The key for detecting a schedule collision is that, if a node has The key for detecting a schedule collision is that, if a node has
several cells to the selected parent, all cells should exhibit the several cells to the selected parent, all cells should exhibit the
same PDR. A cell which exhibits a PDR significantly lower than the same PDR. A cell that exhibits a PDR significantly lower than the
others indicates than there are collisions on that cell. others indicates that there are collisions on that cell.
Every HOUSEKEEPINGCOLLISION_PERIOD, the node executes the following Every HOUSEKEEPINGCOLLISION_PERIOD, the node executes the following
steps: steps:
1. It computes, for each negotiated Tx cell with the parent (not for 1. It computes, for each negotiated Tx cell with the parent (not for
the autonomous cell), that cell's PDR. the autonomous cell), that cell's PDR.
2. Any cell that hasn't yet had NumTx divided by 2 since it was last 2. Any cell that hasn't yet had NumTx divided by 2 since it was last
reset is skipped in steps 3 and 4. This avoids triggering cell reset is skipped in steps 3 and 4. This avoids triggering cell
relocation when the values of NumTx and NumTxAck are not relocation when the values of NumTx and NumTxAck are not
skipping to change at page 13, line 9 skipping to change at line 614
Every HOUSEKEEPINGCOLLISION_PERIOD, the node executes the following Every HOUSEKEEPINGCOLLISION_PERIOD, the node executes the following
steps: steps:
1. It computes, for each negotiated Tx cell with the parent (not for 1. It computes, for each negotiated Tx cell with the parent (not for
the autonomous cell), that cell's PDR. the autonomous cell), that cell's PDR.
2. Any cell that hasn't yet had NumTx divided by 2 since it was last 2. Any cell that hasn't yet had NumTx divided by 2 since it was last
reset is skipped in steps 3 and 4. This avoids triggering cell reset is skipped in steps 3 and 4. This avoids triggering cell
relocation when the values of NumTx and NumTxAck are not relocation when the values of NumTx and NumTxAck are not
statistically significant yet. statistically significant yet.
3. It identifies the cell with the highest PDR. 3. It identifies the cell with the highest PDR.
4. For any other cell, it compares its PDR against that of the cell 4. For any other cell, it compares its PDR against that of the cell
with the highest PDR. If the subtraction difference between the with the highest PDR. If the subtraction difference between the
PDR of the cell and the highest PDR is larger than PDR of the cell and the highest PDR is larger than
RELOCATE_PDRTHRES, it triggers the relocation of that cell using RELOCATE_PDRTHRES, it triggers the relocation of that cell using
a 6P RELOCATE command. a 6P RELOCATE command.
The RELOCATION for negotiated Rx cells is not supported by MSF. The RELOCATION for negotiated Rx cells is not supported by MSF.
6. 6P SIGNAL command 6. 6P SIGNAL Command
The 6P SIGNAL command is not used by MSF. The 6P SIGNAL command is not used by MSF.
7. Scheduling Function Identifier 7. Scheduling Function Identifier
The Scheduling Function Identifier (SFID) of MSF is The Scheduling Function Identifier (SFID) of MSF is 0. How the value
IANA_6TISCH_SFID_MSF. How the value of IANA_6TISCH_SFID_MSF is of 0 was chosen is described in Section 17.
chosen is described in Section 17.
8. Rules for CellList 8. Rules for CellList
MSF uses 2-step 6P Transactions exclusively. 6P transactions are MSF uses two-step 6P Transactions exclusively. 6P Transactions are
only initiated by a node towards its parent. As a result, the cells only initiated by a node towards its parent. As a result, the cells
to put in the CellList of a 6P ADD command, and in the candidate to put in the CellList of a 6P ADD command, and in the candidate
CellList of a RELOCATE command, are chosen by the node initiating the CellList of a RELOCATE command, are chosen by the node initiating the
6P transaction. In both cases, the same rules apply: 6P Transaction. In both cases, the same rules apply:
* The CellList is RECOMMENDED to have five or more cells.
* The CellList is RECOMMENDED to have 5 or more cells.
* Each cell in the CellList MUST have a different slotOffset value. * Each cell in the CellList MUST have a different slotOffset value.
* For each cell in the CellList, the node MUST NOT have any * For each cell in the CellList, the node MUST NOT have any
scheduled cell on the same slotOffset. scheduled cell on the same slotOffset.
* The slotOffset value of any cell in the CellList MUST NOT be the * The slotOffset value of any cell in the CellList MUST NOT be the
same as the slotOffset of the minimal cell (slotOffset=0). same as the slotOffset of the minimal cell (slotOffset=0).
* The slotOffset of a cell in the CellList SHOULD be randomly and * The slotOffset of a cell in the CellList SHOULD be randomly and
uniformly chosen among all the slotOffset values that satisfy the uniformly chosen among all the slotOffset values that satisfy the
restrictions above. restrictions above.
* The channelOffset of a cell in the CellList SHOULD be randomly and * The channelOffset of a cell in the CellList SHOULD be randomly and
uniformly chosen in [0..numFrequencies], where numFrequencies uniformly chosen from [0..numFrequencies], where numFrequencies
represents the number of frequencies a node can communicate on. represents the number of frequencies a node can communicate on.
As a consequence of random cell selection, there is a non-zero chance As a consequence of random cell selection, there is a nonzero chance
that nodes in the vicinity installed cells with same slotOffset and that nodes in the vicinity have installed cells with same slotOffset
channelOffset. An implementer MAY implement a strategy to monitor and channelOffset. An implementer MAY implement a strategy to
the candidate cells before adding them in CellList to avoid monitor the candidate cells before adding them in CellList to avoid
collision. For example, a node MAY maintain a candidate cell pool collision. For example, a node MAY maintain a candidate cell pool
for the CellList. The candidate cells in the pool are pre-configured for the CellList. The candidate cells in the pool are preconfigured
as Rx cells to promiscuously listen to detect transmissions on those as Rx cells to promiscuously listen to detect transmissions on those
cells. If IEEE802.15.4 transmissions are observed on one cell over cells. If transmissions that rely on [IEEE802154] are observed on
multiple iterations of the schedule, that cell is probably used by a one cell over multiple iterations of the schedule, that cell is
TSCH neighbor. It is moved out from the pool and a new cell is probably used by a TSCH neighbor. It is moved out from the pool, and
selected as a candidate cell. The cells in CellList are picked from a new cell is selected as a candidate cell. The cells in CellList
the candidate pool directly when required. are picked from the candidate pool directly when required.
9. 6P Timeout Value 9. 6P Timeout Value
The timeout value is calculated for the worst case that a 6P response The timeout value is calculated for the worst case that a 6P response
is received, which means the 6P response is sent out successfully at is received, which means the 6P response is sent out successfully at
the very latest retransmission. And for each retransmission, it the very latest retransmission. And for each retransmission, it
backs-off with largest value. Hence the 6P timeout value is backs off with largest value. Hence the 6P timeout value is
calculated as ((2^MAXBE)-1)*MAXRETRIES*SLOTFRAME_LENGTH, where: calculated as ((2^MAXBE) - 1) * MAXRETRIES * SLOTFRAME_LENGTH, where:
* MAXBE, defined in IEEE802.15.4, is the maximum backoff exponent * MAXBE, defined in [IEEE802154], is the maximum backoff exponent
used used.
* MAXRETRIES, defined in IEEE802.15.4, is the maximum retransmission
times * MAXRETRIES, defined in [IEEE802154], is the maximum retransmission
* SLOTFRAME_LENGTH represents the length of slotframe times.
* SLOTFRAME_LENGTH represents the length of slotframe.
10. Rule for Ordering Cells 10. Rule for Ordering Cells
Cells are ordered slotOffset first, channelOffset second. Cells are ordered by slotOffset first, channelOffset second.
The following sequence is correctly ordered (each element represents The following sequence is correctly ordered (each element represents
the [slottOffset,channelOffset] of a cell in the schedule): the [slotOffset,channelOffset] of a cell in the schedule):
[1,3],[1,4],[2,0],[5,3],[6,0],[6,3],[7,9] [1,3],[1,4],[2,0],[5,3],[6,0],[6,3],[7,9]
11. Meaning of the Metadata Field 11. Meaning of the Metadata Field
The Metadata field is not used by MSF. The Metadata field is not used by MSF.
12. 6P Error Handling 12. 6P Error Handling
Section 6.2.4 of [RFC8480] lists the 6P Return Codes. Figure 1 lists Section 6.2.4 of [RFC8480] lists the 6P return codes. Table 1 lists
the same error codes, and the behavior a node implementing MSF SHOULD the same error codes and the behavior a node implementing MSF SHOULD
follow. follow.
+-----------------+----------------------+ +=================+======================+
| Code | RECOMMENDED behavior | | Code | RECOMMENDED Behavior |
+-----------------+----------------------+ +=================+======================+
| RC_SUCCESS | nothing | | RC_SUCCESS | nothing |
| RC_EOL | nothing | +-----------------+----------------------+
| RC_ERR | quarantine | | RC_EOL | nothing |
| RC_RESET | quarantine | +-----------------+----------------------+
| RC_ERR_VERSION | quarantine | | RC_ERR | quarantine |
| RC_ERR_SFID | quarantine | +-----------------+----------------------+
| RC_ERR_SEQNUM | clear | | RC_RESET | quarantine |
| RC_ERR_CELLLIST | clear | +-----------------+----------------------+
| RC_ERR_BUSY | waitretry | | RC_ERR_VERSION | quarantine |
| RC_ERR_LOCKED | waitretry | +-----------------+----------------------+
+-----------------+----------------------+ | RC_ERR_SFID | quarantine |
+-----------------+----------------------+
| RC_ERR_SEQNUM | clear |
+-----------------+----------------------+
| RC_ERR_CELLLIST | clear |
+-----------------+----------------------+
| RC_ERR_BUSY | waitretry |
+-----------------+----------------------+
| RC_ERR_LOCKED | waitretry |
+-----------------+----------------------+
Figure 1: Recommended behavior for each 6P Error Code. Table 1: Recommended Behavior for Each
6P Error Code
The meaning of each behavior from Figure 1 is: The meaning of each behavior from Table 1 is:
nothing: Indicates that this return code is not an error. No error
handling behavior is triggered.
nothing: Indicates that this Return Code is not an error. No error
handling behavior is triggered.
clear: Abort the 6P Transaction. Issue a 6P CLEAR command to that clear: Abort the 6P Transaction. Issue a 6P CLEAR command to that
neighbor (this command may fail at the link layer). Remove all neighbor (this command may fail at the link layer). Remove all
cells scheduled with that neighbor from the local schedule. cells scheduled with that neighbor from the local schedule.
quarantine: Same behavior as for "clear". In addition, remove the quarantine: Same behavior as for "clear". In addition, remove the
node from the neighbor and routing tables. Place the node's node from the neighbor and routing tables. Place the node's
identifier in a quarantine list for QUARANTINE_DURATION. When in identifier in a quarantine list for QUARANTINE_DURATION. When in
quarantine, drop all frames received from that node. quarantine, drop all frames received from that node.
waitretry: Abort the 6P Transaction. Wait for a duration randomly waitretry: Abort the 6P Transaction. Wait for a duration randomly
and uniformly chosen in [WAIT_DURATION_MIN,WAIT_DURATION_MAX]. and uniformly chosen from [WAIT_DURATION_MIN,WAIT_DURATION_MAX].
Retry the same transaction. Retry the same transaction.
13. Schedule Inconsistency Handling 13. Schedule Inconsistency Handling
The behavior when schedule inconsistency is detected is explained in The behavior when schedule inconsistency is detected is explained in
Figure 1, for 6P Return Code RC_ERR_SEQNUM. Table 1, for 6P return code RC_ERR_SEQNUM.
14. MSF Constants 14. MSF Constants
Figure 2 lists MSF Constants and their RECOMMENDED values. Table 2 lists MSF constants and their RECOMMENDED values.
+------------------------------+-------------------+ +==============================+===================+
| Name | RECOMMENDED value | | Name | RECOMMENDED value |
+==============================+===================+
| SLOTFRAME_LENGTH | 101 slots |
+------------------------------+-------------------+ +------------------------------+-------------------+
| SLOTFRAME_LENGTH | 101 slots | | NUM_CH_OFFSET | 16 |
| NUM_CH_OFFSET | 16 | +------------------------------+-------------------+
| MAX_NUM_CELLS | 100 | | MAX_NUM_CELLS | 100 |
| LIM_NUMCELLSUSED_HIGH | 75 | +------------------------------+-------------------+
| LIM_NUMCELLSUSED_LOW | 25 | | LIM_NUMCELLSUSED_HIGH | 75 |
| MAX_NUMTX | 256 | +------------------------------+-------------------+
| HOUSEKEEPINGCOLLISION_PERIOD | 1 min | | LIM_NUMCELLSUSED_LOW | 25 |
| RELOCATE_PDRTHRES | 50 % | +------------------------------+-------------------+
| QUARANTINE_DURATION | 5 min | | MAX_NUMTX | 256 |
| WAIT_DURATION_MIN | 30 s | +------------------------------+-------------------+
| WAIT_DURATION_MAX | 60 s | | HOUSEKEEPINGCOLLISION_PERIOD | 1 min |
+------------------------------+-------------------+
| RELOCATE_PDRTHRES | 50 % |
+------------------------------+-------------------+
| QUARANTINE_DURATION | 5 min |
+------------------------------+-------------------+
| WAIT_DURATION_MIN | 30 s |
+------------------------------+-------------------+
| WAIT_DURATION_MAX | 60 s |
+------------------------------+-------------------+ +------------------------------+-------------------+
Figure 2: MSF Constants and their RECOMMENDED values. Table 2: MSF Constants and Their RECOMMENDED Values
15. MSF Statistics 15. MSF Statistics
Figure 3 lists MSF Statistics and their RECOMMENDED width. Table 3 lists MSF statistics and their RECOMMENDED widths.
+-----------------+-------------------+ +=================+===================+
| Name | RECOMMENDED width | | Name | RECOMMENDED width |
+-----------------+-------------------+ +=================+===================+
| NumCellsElapsed | 1 byte | | NumCellsElapsed | 1 byte |
| NumCellsUsed | 1 byte | +-----------------+-------------------+
| NumTx | 1 byte | | NumCellsUsed | 1 byte |
| NumTxAck | 1 byte | +-----------------+-------------------+
+-----------------+-------------------+ | NumTx | 1 byte |
+-----------------+-------------------+
| NumTxAck | 1 byte |
+-----------------+-------------------+
Figure 3: MSF Statistics and their RECOMMENDED width. Table 3: MSF Statistics and Their
RECOMMENDED Widths
16. Security Considerations 16. Security Considerations
MSF defines a series of "rules" for the node to follow. It triggers MSF defines a series of "rules" for the node to follow. It triggers
several actions, that are carried out by the protocols defined in the several actions that are carried out by the protocols defined in the
following specifications: the Minimal IPv6 over the TSCH Mode of IEEE following specifications: "Minimal IPv6 over the TSCH Mode of IEEE
802.15.4e (6TiSCH) Configuration [RFC8180], the 6TiSCH Operation 802.15.4e (6TiSCH) Configuration" [RFC8180], "6TiSCH Operation
Sublayer Protocol (6P) [RFC8480], and the Constrained Join Protocol Sublayer (6top) Protocol (6P)" [RFC8480], and "Constrained Join
(CoJP) for 6TiSCH [I-D.ietf-6tisch-minimal-security]. Protocol (CoJP) for 6TiSCH" [RFC9031]. Confidentiality and
Confidentiality and authentication of MSF control and data traffic authentication of MSF control and data traffic are provided by these
are provided by these specifications whose security considerations specifications whose security considerations continue to apply to
continue to apply to MSF. In particular, MSF does not define a new MSF. In particular, MSF does not define a new protocol or packet
protocol or packet format. format.
MSF uses autonomous cells for initial bootstrap and the transport of MSF uses autonomous cells for initial bootstrap and the transport of
join traffic. Autonomous cells are computed as a hash of nodes' join traffic. Autonomous cells are computed as a hash of nodes'
EUI64 addresses. This makes the coordinates of autonomous cell an EUI-64 addresses. This makes the coordinates of autonomous cell an
easy target for an attacker, as EUI64 addresses are visible on the easy target for an attacker, as EUI-64 addresses are visible on the
wire and are not encrypted by the link-layer security mechanism. wire and are not encrypted by the link-layer security mechanism.
With the coordinates of autonomous cells available, the attacker can With the coordinates of autonomous cells available, the attacker can
launch a selective jamming attack against any nodes' AutoRxCell. If launch a selective jamming attack against any node's AutoRxCell. If
the attacker targets a node acting as a JP, it can prevent pledges the attacker targets a node acting as a JP, it can prevent pledges
from using that JP to join the network. The pledge detects such a from using that JP to join the network. The pledge detects such a
situation through the absence of a link-layer acknowledgment for its situation through the absence of a link-layer acknowledgment for its
Join Request. As it is expected that each pledge will have more than Join Request. As it is expected that each pledge will have more than
one JP available to join the network, one available countermeasure one JP available to join the network, one available countermeasure
for the pledge is to pseudo-randomly select a new JP when the link to for the pledge is to pseudorandomly select a new JP when the link to
the previous JP appears bad. Such strategy alleviates the issue of the previous JP appears bad. Such a strategy alleviates the issue of
the attacker randomly jamming to disturb the network but does not the attacker randomly jamming to disturb the network but does not
help in case the attacker is targeting a particular pledge. In that help in the case the attacker is targeting a particular pledge. In
case, the attacker can jam the AutoRxCell of the pledge, in order to that case, the attacker can jam the AutoRxCell of the pledge in order
prevent it from receiving the join response. This situation should to prevent it from receiving the join response. This situation
be detected through the absence of a particular node from the network should be detected through the absence of a particular node from the
and handled by the network administrator through out-of-band means. network and handled by the network administrator through out-of-band
means.
MSF adapts to traffic containing packets from the IP layer. It is MSF adapts to traffic containing packets from the IP layer. It is
possible that the IP packet has a non-zero DSCP (Diffserv Code Point possible that the IP packet has a nonzero DSCP (Differentiated
[RFC2474]) value in its IPv6 header. The decision how to handle that Services Code Point) [RFC2474] value in its IPv6 header. The
packet belongs to the upper layer and is out of scope of MSF. As decision how to handle that packet belongs to the upper layer and is
long as the decision is made to hand over to MAC layer to transmit, out of scope of MSF. As long as the decision is made to hand over to
MSF will take that packet into account when adapting to traffic. MAC layer to transmit, MSF will take that packet into account when
adapting to traffic.
Note that non-zero DSCP value may imply that the traffic is Note that nonzero DSCP values may imply that the traffic originated
originated at unauthenticated pledges, referring to at unauthenticated pledges (see [RFC9031]). The implementation at
[I-D.ietf-6tisch-minimal-security]. The implementation at IPv6 layer the IPv6 layer SHOULD rate limit this join traffic before it is
SHOULD rate-limit this join traffic before it is passed to 6top passed to the 6top sublayer where MSF can observe it. If there is no
sublayer where MSF can observe it. In case there is no rate limit rate limit for join traffic, intermediate nodes in the 6TiSCH network
for join traffic, intermediate nodes in the 6TiSCH network may be may be prone to a resource exhaustion attack, with the attacker
prone to a resource exhaustion attack, with the attacker injecting injecting unauthenticated traffic from the network edge. The
unauthenticated traffic from the network edge. The assumption is assumption is that the rate-limiting function is aware of the
that the rate limiting function is aware of the available bandwidth available bandwidth in the 6top Layer 3 bundle(s) towards a next hop,
in the 6top L3 bundle(s) towards a next hop, not directly from MSF, not directly from MSF, but from an interaction with the 6top sublayer
but from an interaction with the 6top sublayer that manages that ultimately manages the bundles under MSF's guidance. How this
ultimately the bundles under MSF's guidance. How this rate-limit is rate limit is implemented is out of scope of MSF.
implemented is out of scope of MSF.
17. IANA Considerations 17. IANA Considerations
17.1. MSF Scheduling Function Identifiers 17.1. MSF Scheduling Function Identifiers
This document adds the following number to the "6P Scheduling This document adds the following number to the "6P Scheduling
Function Identifiers" sub-registry, part of the "IPv6 over the TSCH Function Identifiers" subregistry, part of the "IPv6 Over the TSCH
mode of IEEE 802.15.4e (6TiSCH) parameters" registry, as defined by Mode of IEEE 802.15.4 (6TiSCH)" registry, as defined by [RFC8480]:
[RFC8480]:
+----------------------+-----------------------------+-------------+
| SFID | Name | Reference |
+----------------------+-----------------------------+-------------+
| IANA_6TISCH_SFID_MSF | Minimal Scheduling Function | RFC_THIS |
| | (MSF) | |
+----------------------+-----------------------------+-------------+
Figure 4: New SFID in 6P Scheduling Function Identifiers subregistry. +======+===================================+===========+
| SFID | Name | Reference |
+======+===================================+===========+
| 0 | Minimal Scheduling Function (MSF) | RFC 9033 |
+------+-----------------------------------+-----------+
IANA_6TISCH_SFID_MSF is chosen from range 0-127, which is used for Table 4: New SFID in the "6P Scheduling Function
IETF Review or IESG Approval. Identifiers" Subregistry
18. Contributors The SFID was chosen from the range 0-127, which has the registration
procedure of IETF Review or IESG Approval [RFC8126].
* Beshr Al Nahas (Chalmers University, beshr@chalmers.se) 18. References
* Olaf Landsiedel (Chalmers University, olafl@chalmers.se)
* Yasuyuki Tanaka (Inria-Paris, yasuyuki.tanaka@inria.fr)
19. References 18.1. Normative References
19.1. Normative References [IEEE802154]
IEEE, "IEEE Standard for Low-Rate Wireless Networks", IEEE
Standard 802.15.4-2015, DOI 10.1109/IEEESTD.2016.7460875,
April 2016,
<https://ieeexplore.ieee.org/document/7460875>.
[RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH) Requirement Levels", BCP 14, RFC 2119,
Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180, DOI 10.17487/RFC2119, March 1997,
May 2017, <https://www.rfc-editor.org/info/rfc8180>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8480] Wang, Q., Ed., Vilajosana, X., and T. Watteyne, "6TiSCH [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
Operation Sublayer (6top) Protocol (6P)", RFC 8480, "Definition of the Differentiated Services Field (DS
DOI 10.17487/RFC8480, November 2018, Field) in the IPv4 and IPv6 Headers", RFC 2474,
<https://www.rfc-editor.org/info/rfc8480>. DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012, DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>. <https://www.rfc-editor.org/info/rfc6550>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Requirement Levels", BCP 14, RFC 2119, Writing an IANA Considerations Section in RFCs", BCP 26,
DOI 10.17487/RFC2119, March 1997, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, [RFC8180] Vilajosana, X., Ed., Pister, K., and T. Watteyne, "Minimal
"Definition of the Differentiated Services Field (DS IPv6 over the TSCH Mode of IEEE 802.15.4e (6TiSCH)
Field) in the IPv4 and IPv6 Headers", RFC 2474, Configuration", BCP 210, RFC 8180, DOI 10.17487/RFC8180,
DOI 10.17487/RFC2474, December 1998, May 2017, <https://www.rfc-editor.org/info/rfc8180>.
<https://www.rfc-editor.org/info/rfc2474>.
[I-D.ietf-6tisch-minimal-security] [RFC8480] Wang, Q., Ed., Vilajosana, X., and T. Watteyne, "6TiSCH
Vucinic, M., Simon, J., Pister, K., and M. Richardson, Operation Sublayer (6top) Protocol (6P)", RFC 8480,
"Constrained Join Protocol (CoJP) for 6TiSCH", Work in DOI 10.17487/RFC8480, November 2018,
Progress, Internet-Draft, draft-ietf-6tisch-minimal- <https://www.rfc-editor.org/info/rfc8480>.
security-15, December 10, 2019,
<https://tools.ietf.org/html/draft-ietf-6tisch-minimal-
security-15>.
[I-D.ietf-6tisch-enrollment-enhanced-beacon] [RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Dujovne, D. and M. Richardson, "IEEE 802.15.4 Information Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
Element encapsulation of 6TiSCH Join and Enrollment RFC 9030, DOI 10.17487/RFC9030, May 2021,
Information", Work in Progress, Internet-Draft, draft- <https://www.rfc-editor.org/info/rfc9030>.
ietf-6tisch-enrollment-enhanced-beacon-14, February 21,
2020, <https://tools.ietf.org/html/draft-ietf-6tisch-
enrollment-enhanced-beacon-14>.
[I-D.ietf-6tisch-architecture] [RFC9031] Vučinić, M., Ed., Simon, J., Pister, K., and M.
Thubert, P., "An Architecture for IPv6 over the TSCH mode Richardson, "Constrained Join Protocol (CoJP) for 6TiSCH",
of IEEE 802.15.4", Work in Progress, Internet-Draft, RFC 9031, DOI 10.17487/RFC9031, May 2021,
draft-ietf-6tisch-architecture-28, October 29, 2019, <https://www.rfc-editor.org/info/rfc9031>.
<https://tools.ietf.org/html/draft-ietf-6tisch-
architecture-28>.
[IEEE802154] [RFC9032] Dujovne, D., Ed. and M. Richardson, "Encapsulation of
IEEE standard for Information Technology, "IEEE Std 6TiSCH Join and Enrollment Information Elements",
802.15.4 Standard for Low-Rate Wireless Personal Area RFC 9032, DOI 10.17487/RFC9032, May 2021,
Networks (WPANs)", DOI 10.1109/IEEE P802.15.4-REVd/D01, <https://www.rfc-editor.org/info/rfc9032>.
<http://ieeexplore.ieee.org/document/7460875/>.
[SAX-DASFAA] [SAX-DASFAA]
Ramakrishna, M.V. and J. Zobel, "Performance in Practice Ramakrishna, M.V. and J. Zobel, "Performance in Practice
of String Hashing Functions", DASFAA , of String Hashing Functions", DASFAA,
DOI 10.1142/9789812819536_0023, 1997, DOI 10.1142/9789812819536_0023, 1997,
<https://doi.org/10.1142/9789812819536_0023>. <https://doi.org/10.1142/9789812819536_0023>.
19.2. Informative References 18.2. Informative References
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>.
[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using [RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554, Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015, DOI 10.17487/RFC7554, May 2015,
<https://www.rfc-editor.org/info/rfc7554>. <https://www.rfc-editor.org/info/rfc7554>.
[I-D.ietf-6tisch-dtsecurity-zerotouch-join]
Richardson, M., "6tisch Zero-Touch Secure Join protocol",
Work in Progress, Internet-Draft, draft-ietf-6tisch-
dtsecurity-zerotouch-join-04, July 8, 2019,
<https://tools.ietf.org/html/draft-ietf-6tisch-dtsecurity-
zerotouch-join-04>.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>. <https://www.rfc-editor.org/info/rfc8505>.
Appendix A. Example of Implementation of SAX hash function [ZEROTOUCH-JOIN]
Richardson, M., "6tisch Zero-Touch Secure Join protocol",
Work in Progress, Internet-Draft, draft-ietf-6tisch-
dtsecurity-zerotouch-join-04, 8 July 2019,
<https://tools.ietf.org/html/draft-ietf-6tisch-dtsecurity-
zerotouch-join-04>.
Considering the interoperability, this section provides an example of Appendix A. Example Implementation of the SAX Hash Function
implemention SAX hash function [SAX-DASFAA]. The input parameters of
the function are:
* T, which is the hashing table length To support interoperability, this section provides an example
* c, which is the characters of string s, to be hashed implementation of the SAX hash function [SAX-DASFAA]. The input
parameters of the function are:
* T, which is the hashing table length.
* c, which is the characters of string s, to be hashed.
In MSF, the T is replaced by the length of slotframe 1. String s is In MSF, the T is replaced by the length of slotframe 1. String s is
replaced by the mote EUI64 address. The characters of the string c0, replaced by the node EUI-64 address. The characters of the string,
c1, ..., c7 are the 8 bytes of EUI64 address. c0 through c7, are the eight bytes of the EUI-64 address.
The SAX hash function requires shift operation which is defined as The SAX hash function requires shift operation, which is defined as
follow: follow:
* L_shift(v,b), which refers to left shift variable v by b bits * L_shift(v,b), which refers to the left shift of variable v by b
* R_shift(v,b), which refers to right shift variable v by b bits bits
* R_shift(v,b), which refers to the right shift of variable v by b
bits
The steps to calculate the hash value of SAX hash function are: The steps to calculate the hash value of SAX hash function are:
1. initialize variable h to h0 and variable i to 0, where h is the 1. Initialize variable h, which is the intermediate hash value, to
intermediate hash value and i is the index of the bytes of EUI64 h0 and variable i, which is the index of the bytes of the EUI-64
address address, to 0.
2. sum the value of L_shift(h,l_bit), R_shift(h,r_bit) and ci
3. calculate the result of exclusive or between the sum value in
Step 2 and h
4. modulo the result of Step 3 by T
5. assign the result of Step 4 to h
6. increase i by 1
7. repeat Step2 to Step 6 until i reaches to 8
The value of variable h is the hash value of SAX hash function. 2. Sum the value of L_shift(h,l_bit), R_shift(h,r_bit), and ci.
The values of h0, l_bit and r_bit in Step 1 and 2 are configured as: 3. Calculate the result of the exclusive OR between the sum value in
Step 2 and h.
* h0 = 0 4. Modulo the result of Step 3 by T.
* l_bit = 0
* r_bit = 1 5. Assign the result of Step 4 to h.
6. Increase i by 1.
7. Repeat Step 2 to Step 6 until i reaches to 8.
The value of variable h is the hash value of the SAX hash function.
The values of h0, l_bit, and r_bit in Step 1 and Step 2 are
configured as:
h0 = 0
l_bit = 0
r_bit = 1
The appropriate values of l_bit and r_bit could vary depending on the The appropriate values of l_bit and r_bit could vary depending on the
the set of motes' EUI64 address. How to find those values is out of set of nodes' EUI-64 address. How to find those values is out of the
the scope of this specification. scope of this specification.
Contributors
Beshr Al Nahas
Chalmers University
Email: beshr@chalmers.se
Olaf Landsiedel
Chalmers University
Email: olafl@chalmers.se
Yasuyuki Tanaka
Toshiba
Email: yatch1.tanaka@toshiba.co.jp
Authors' Addresses Authors' Addresses
Tengfei Chang (editor) Tengfei Chang (editor)
Inria Inria
2 rue Simone Iff 2 rue Simone Iff
75012 Paris 75012 Paris
France France
Email: tengfei.chang@inria.fr Email: tengfei.chang@gmail.com
Malisa Vucinic Mališa Vučinić
Inria Inria
2 rue Simone Iff 2 rue Simone Iff
75012 Paris 75012 Paris
France France
Email: malisa.vucinic@inria.fr Email: malisa.vucinic@inria.fr
Xavier Vilajosana Xavier Vilajosana
Universitat Oberta de Catalunya Universitat Oberta de Catalunya
156 Rambla Poblenou 156 Rambla Poblenou
08018 Barcelona Catalonia 08018 Barcelona Catalonia
Spain Spain
Email: xvilajosana@uoc.edu Email: xvilajosana@uoc.edu
Simon Duquennoy Simon Duquennoy
RISE SICS RISE SICS
skipping to change at page 22, line 15 skipping to change at line 1081
Universitat Oberta de Catalunya Universitat Oberta de Catalunya
156 Rambla Poblenou 156 Rambla Poblenou
08018 Barcelona Catalonia 08018 Barcelona Catalonia
Spain Spain
Email: xvilajosana@uoc.edu Email: xvilajosana@uoc.edu
Simon Duquennoy Simon Duquennoy
RISE SICS RISE SICS
Isafjordsgatan 22 Isafjordsgatan 22
164 29 Kista SE-164 29 Kista
Sweden Sweden
Email: simon.duquennoy@gmail.com Email: simon.duquennoy@gmail.com
Diego Dujovne Diego Dujovne
Universidad Diego Portales Universidad Diego Portales
Escuela de Informatica y Telecomunicaciones Escuela de Informática y Telecomunicaciones
Av. Ejercito 441 Av. Ejército 441
Santiago Santiago
Region Metropolitana Región Metropolitana
Chile Chile
Phone: +56 (2) 676-8121 Phone: +56 (2) 676-8121
Email: diego.dujovne@mail.udp.cl Email: diego.dujovne@mail.udp.cl
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