6TiSCH MR. Palattella, Ed.
Internet-Draft LIST
Intended status: Informational P. Thubert
Expires: June 19, 2017 cisco
T. Watteyne
Linear Technology / Dust Networks
Q. Wang
Univ. of Sci. and Tech. Beijing
December 16, 2016
Terminology in IPv6 over the TSCH mode of IEEE 802.15.4e
draft-ietf-6tisch-terminology-08
Abstract
This document provides a glossary of terminology used in IPv6 over
the TSCH mode of IEEE 802.15.4e (6TiSCH). This document extends
existing terminology documents for Low-power and Lossy Networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 19, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Security Considerations . . . . . . . . . . . . . . . . . . . 8
4. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Normative References . . . . . . . . . . . . . . . . . . 8
4.2. Informative References . . . . . . . . . . . . . . . . . 9
4.3. External Informative References . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The IEEE802.15.4 Medium Access Control (MAC) has evolved with the
Time Slotted Channel Hopping (TSCH) mode for industrial-type
applications. It provides deterministic capabilities to the point
that a packet that pertains to a certain flow crosses the network
from node to node following a very precise schedule, like a train
leaves intermediate stations at precise times along its path.
This document provides additional terminology elements to cover terms
that are new to the context of TSCH wireless networks and other
deterministic networks.
2. Terminology
The draft extends [RFC7102] and use terms from [RFC6550] and
[RFC6552], which are all included here by reference.
The draft does not reuse terms from IEEE802.15.4e such as "path" or
"link" which bear a meaning that is quite different from classical
IETF parlance.
This document adds the following terms:
6TiSCH: IPv6 over the Timeslotted Channel Hopping (TSCH) mode of
IEEE802.15.4e. It defines (i) the 6top sublayer; (ii) a
set of protocols for setting up a TSCH schedule in
distributed approach, for managing the allocation of
resources; and (iii) the architecture to bind them
together, for use in IPv6 TSCH based networks.
6top: The "6TiSCH Operation Sublayer" (6top) is the next
highest layer of the IEEE802.15.4e TSCH medium access
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control layer. It implements and terminates the "6top
Protocol" (6P), and contains a "6top Scheduling Function"
(SF).
SF: The "6top Scheduling Function" (SF) "is the cell
management entity that add or delete cells dynamically
based on its allocation policy in order to fulfill cell
requirements. The cell negotiation with a neighbor is
done using 6P. General guidelines for designing a SF are
provided in [I-D.ietf-6tisch-6top-protocol].
SFID: The "6top Scheduling Function Identifier" (SFID) is a
4-bit field identifying a SF. Defined in
[I-D.ietf-6tisch-6top-protocol].
6P: The "6top Protocol" (6P) allows neighbor nodes to
communicate to add/delete cells to one another in their
TSCH schedule. Defined in
[I-D.ietf-6tisch-6top-protocol].
6P Transaction: Part of the "6top Protocol" (6P), the action of two
neighbors exchanging a 6P request message and the
corresponding 6P response message. Defined in
[I-D.ietf-6tisch-6top-protocol].
ASN: Absolute Slot Number, the total number of timeslots that
have elapsed since the PAN coordinator has started the
TSCH network. Incremented by one at each timeslot. It
is wide enough to not roll over in practice. See
[IEEE802154-2015] and [RFC7554].
Blacklist of Frequencies: A set of frequencies which should not be
used for communication. See [IEEE802154-2015] and
[RFC7554].
BBR: Backbone Router. In the 6TiSCH architecture, an LBR and
also a IPv6 ND-efficiency-aware Router (NEAR)
[I-D.chakrabarti-nordmark-6man-efficient-nd]. Performs
ND proxy operations between registered devices and
classical ND devices that are located over the backbone.
Broadcast Cell: A scheduled cell used for broadcast transmission.
Bundle: A group of equivalent scheduled cells, i.e. cells
identified by different [slotOffset, channelOffset],
which are scheduled for a same purpose, with the same
neighbor, with the same flags, and the same slotframe.
The size of the bundle refers to the number of cells it
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contains. For a given slotframe length, the size of the
bundle translates directly into bandwidth. A bundle is a
local abstraction thar represents a half-duplex link for
either sending or receiving, with bandwidth that amounts
to the sum of the cells in the bundle. A bundle is
globally identified by (source MAC, destination MAC,
TrackID). At Layer 3, a pair of bundles forms a link.
By using a well-known constant, NULLT, as TrackId for a
L3 link, the IP link between adjacent nodes A and B
comprises 2 bundles: (macA, macB, NULLT) and (macB, macA,
NULLT). At Layer 2, a pair of bundles forms a switching
state. Considered a segment A-B-C along a track, there
are two bundles in node B, one incoming = (macA, macB,
trackId) and one outgoing = (macB, macC, trackId).
CCA: Clear Channel Assessment. Mechanism defined in
[IEEE802154-2015], section 6.2.5.2. In a TSCH network,
CCA can be used to detect other radio networks in
vicinity. Nodes listen the channel before sending, to
detect other ongoing transmissions. Because the network
is synchronized, CCA cannot be used to detect colliding
transmission within the same network. CCA is necessary
for the 6TiSCH minimal configuration
[I-D.ietf-6tisch-minimal] in shared slots, and in
presence of multiple instances of 6TiSCH networks.
Cell: A single element in the TSCH schedule, identified by a
slotOffset, a channelOffset, a slotframeHandle. A cell
can be scheduled or unscheduled.
Centralized Cell Reservation: A reservation of a cell done by a
centralized entity (e.g., a PCE) in the network.
Centralized Track Reservation: A reservation of a track done by a
centralized entity (e.g., a PCE) in the network.
ChannelOffset: Identifies a row in the TSCH schedule. The number of
available channelOffset values is equal to the number of
available frequencies. The channelOffset translates into
a frequency when the communication takes place, resulting
in channel hopping. See [RFC7554].
Channel Distribution/Usage (CDU) matrix: : Matrix of cells (i,j)
representing the spectrum (channel) distribution among
the different nodes in the 6TiSCH network. The CDU
matrix has width in timeslots, equal to the period of the
network scheduling operation, and height equal to the
number of available channels. Every cell (i,j) in the
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CDU, identified by (slotOffset, channelOffset), belongs
to a specific chunk. It has to be noticed that such a
matrix which includes all the cells grouped in chunks,
belonging to different slotframes, is different from the
TSCH schedule.
Chunk: A well-known list of cells, distributed in time and
frequency, within a CDU matrix; a chunk represents a
portion of a CDU matrix. The partition of the CDU in
chunks is globally known by all the nodes in the network
to support the appropriation process, which is a
negotiation between nodes within an interference domain.
A node that manages to appropriate a chunk gets to decide
which transmissions will occur over the cells in the
chunk within its interference domain (i.e., a parent node
will decide when the cells within the appropriated chunk
are used and by which node, among its children.
Dedicated Cell: A cell that is reserved for a given node to transmit
to a specific neighbor.
Deterministic Network: The generic concept of deterministic network
is defined in [I-D.ietf-detnet-architecture]. When
applied to 6TiSCH it refers to the reservation of tracks
which guarantee an end to end latency and optimize the
PDR for well-characterized flows.
Distributed Cell Reservation: A reservation of a cell done by one or
more in-network entities (typically a connection
endpoint).
Distributed Track Reservation: A reservation of a track done by one
or more in-network entities (typically a connection
endpoint).
EB: Enhanced Beacon frame used by a node to announce the
presence of the network. It contains enough information
for a joining node to synchronize to the network. See
[IEEE802154-2015] and [RFC7554].
Hard Cell: A scheduled cell which the 6top sublayer cannot relocate.
Hopping Sequence: Ordered sequence of frequencies, identified by a
Hopping_Sequence_ID, used for channel hopping, when
translating the channel offset value into a frequency
(i.e., PHY channel). See [IEEE802154-2015] and
[RFC7554].
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IE: Information Element, a Type-Length-Value containers
placed at the end of the MAC header, used to pass data
between layers or devices. Some IE identifiers are
managed by the IEEE [IEEE802154-2015]. Some IE
identifiers are managed by the IETF
[I-D.kivinen-802-15-ie].
JCE: The Join Coordination Entity (JCE) is a central entity
that coordinates the joining of new nodes in the network.
See [I-D.ietf-6tisch-minimal-security] and
[I-D.ietf-6tisch-dtsecurity-secure-join].
JA: The Join Assistant (JA) is a one-hop neighbor of a
joining node that may facilitate it to become meaningful
part of the network (e.g., by serving as a local
connectivity point to the remainder of the network). JA
emits EBs, used by JNs to synchronize to the network.
See [I-D.ietf-6tisch-minimal-security] and
[I-D.ietf-6tisch-dtsecurity-secure-join].
JN: The Joining Node (JN) is a device attempting to join a
particular 6TiSCH network. See
[I-D.ietf-6tisch-minimal-security].
Join Protocol: The protocol which secures initial communication
between a joining node and the JCE.
LBR: Low-power Lossy Network (LLN) Border Router. It is an
LLN device, usually powered, that acts as a Border Router
to the outside within the 6TiSCH architecture.
Link: A communication facility or medium over which nodes can
communicate at the link layer, i.e., the layer
immediately below IP. Thus, the IETF parlance for the
term "Link" is adopted, as opposed to the IEEE802.15.4e
terminology.
Operational Network: A IEEE802.15.4e network whose encryption/
authentication keys are determined by some algorithms/
protocols. There may be network-wide group keys, or per-
link keys.
(to) Relocate a Cell: The action operated by the 6top sublayer of
changing the slotOffset and/or channelOffset of a soft
cell.
(to) Schedule a Cell: The action of turning an unscheduled cell into
a scheduled cell.
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Scheduled cell: A cell which is assigned a neighbor MAC address
(broadcast address is also possible), and one or more of
the following flags: TX, RX, shared, timeskeeping. A
scheduled cell can be used by the IEEE802.15.4e TSCH
implementation to communicate. A scheduled cell can be
either a hard or a soft cell.
Shared Cell: A cell marked with both the "TX" and "shared" flags.
This cell can be used by more than one transmitter node.
A back-off algorithm is used to resolve contention. See
[IEEE802154-2015] and [RFC7554].
SlotOffset: Identifies a column in the TSCH schedule, i.e., the
number of timeslots since the beginning of the current
iteration of the slotframe. See [IEEE802154-2015] and
[RFC7554].
Slotframe: A collection of timeslots repeating in time, analogous to
a superframe in that it defines periods of communication
opportunities. It is characterized by a slotframe_ID,
and a slotframe_size. Multiple slotframes can coexist in
a node's schedule, i.e., a node can have multiple
activities scheduled in different slotframes, based on
the priority of its packets/traffic flows. The timeslots
in the Slotframe are indexed by the SlotOffset; the first
timeslot is at SlotOffset 0. See [IEEE802154-2015] and
[RFC7554].
Soft Cell: A scheduled cell which the 6top sublayer can relocate.
Timeslot: A basic communication unit in TSCH which allows a
transmitter node to send a frame to a receiver neighbor,
and that receiver neighbor to optionally send back an
acknowledgment. See [IEEE802154-2015] and [RFC7554].
Time Source Neighbor: A neighbor that a node uses as its time
reference, and to which it needs to keep its clock
synchronized. See [IEEE802154-2015] and [RFC7554].
Track: A determined sequence of cells along a multi-hop path.
It is typically the result of a track reservation. The
node that initializes the process of establishing a track
is the owner of the track. The latter assigns a unique
identifier to the track, called TrackID.
TrackID: Unique identifier of a track, assigned by the owner of
the track.
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TSCH: Time Slotted Channel Hopping, a medium access mode of the
[IEEE802154-2015] standard which uses time
synchronization to achieve ultra low-power operation and
channel hopping to enable high reliability. See
[IEEE802154-2015] and [RFC7554].
TSCH Schedule: A matrix of cells, each cell indexed by a slotOffset
and a channelOffset. The TSCH schedule contains all the
scheduled cells from all slotframes and is sufficient to
qualify the communication in the TSCH network. The
number of channelOffset values (the "height" of the
matrix) is equal to the number of available frequencies.
See [IEEE802154-2015] and [RFC7554].
Unscheduled Cell: A cell which is not used by the IEEE802.15.4e TSCH
implementation. See [IEEE802154-2015] and [RFC7554].
3. Security Considerations
Since this document specifies terminology and does not specify new
procedures or protocols, it raises no new security issues.
4. References
4.1. Normative References
[RFC2309] Braden, B., Clark, D., Crowcroft, J., Davie, B., Deering,
S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G.,
Partridge, C., Peterson, L., Ramakrishnan, K., Shenker,
S., Wroclawski, J., and L. Zhang, "Recommendations on
Queue Management and Congestion Avoidance in the
Internet", RFC 2309, DOI 10.17487/RFC2309, April 1998,
<http://www.rfc-editor.org/info/rfc2309>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<http://www.rfc-editor.org/info/rfc3444>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<http://www.rfc-editor.org/info/rfc6550>.
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[RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)",
RFC 6552, DOI 10.17487/RFC6552, March 2012,
<http://www.rfc-editor.org/info/rfc6552>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <http://www.rfc-editor.org/info/rfc7102>.
[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015,
<http://www.rfc-editor.org/info/rfc7554>.
4.2. Informative References
[I-D.chakrabarti-nordmark-6man-efficient-nd]
Chakrabarti, S., Nordmark, E., Thubert, P., and M.
Wasserman, "IPv6 Neighbor Discovery Optimizations for
Wired and Wireless Networks", draft-chakrabarti-nordmark-
6man-efficient-nd-07 (work in progress), February 2015.
[I-D.ietf-6tisch-6top-protocol]
Wang, Q. and X. Vilajosana, "6top Protocol (6P)", draft-
ietf-6tisch-6top-protocol-03 (work in progress), October
2016.
[I-D.ietf-6tisch-dtsecurity-secure-join]
Richardson, M., "6tisch Secure Join protocol", draft-ietf-
6tisch-dtsecurity-secure-join-00 (work in progress),
December 2016.
[I-D.ietf-6tisch-minimal]
Vilajosana, X. and K. Pister, "Minimal 6TiSCH
Configuration", draft-ietf-6tisch-minimal-17 (work in
progress), November 2016.
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[I-D.ietf-6tisch-minimal-security]
malisa.vucinic@st.com, m., Simon, J., and K. Pister,
"Minimal Security Framework for 6TiSCH", draft-ietf-
6tisch-minimal-security-00 (work in progress), December
2016.
[I-D.ietf-detnet-architecture]
Finn, N. and P. Thubert, "Deterministic Networking
Architecture", draft-ietf-detnet-architecture-00 (work in
progress), September 2016.
[I-D.kivinen-802-15-ie]
Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information
Element for IETF", draft-kivinen-802-15-ie-04 (work in
progress), October 2016.
[I-D.thubert-6lo-rfc6775-update-reqs]
Thubert, P. and P. Stok, "Requirements for an update to
6LoWPAN ND", draft-thubert-6lo-rfc6775-update-reqs-07
(work in progress), April 2016.
[I-D.thubert-roll-forwarding-frags]
Thubert, P. and J. Hui, "LLN Fragment Forwarding and
Recovery", draft-thubert-roll-forwarding-frags-02 (work in
progress), September 2013.
4.3. External Informative References
[IEEE802154-2015]
IEEE standard for Information Technology, "IEEE Std
802.15.4-2015 Standard for Low-Rate Wireless Personal Area
Networks (WPANs)", December 2015.
Authors' Addresses
Maria Rita Palattella (editor)
Luxembourg Institute of Science and Technology
Department 'Environmental Research and Innovation' (ERIN)
41, rue du Brill
Belvaux L-4422
Luxembourg
Phone: (+352) 275 888-5055
Email: mariarita.palattella@list.lu
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Pascal Thubert
Cisco Systems, Inc
Village d'Entreprises Green Side
400, Avenue de Roumanille
Batiment T3
Biot - Sophia Antipolis 06410
France
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Thomas Watteyne
Linear Technology / Dust Networks
30695 Huntwood Avenue
Hayward, CA 94544
USA
Phone: +1 (510) 400-2978
Email: twatteyne@linear.com
Qin Wang
Univ. of Sci. and Tech. Beijing
30 Xueyuan Road
Beijing 100083
China
Phone: +86 (10) 6233 4781
Email: wangqin@ies.ustb.edu.cn
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