Internet DRAFT - draft-palattella-6tisch-terminology
draft-palattella-6tisch-terminology
6TiSCH MR. Palattella, Ed.
Internet-Draft SnT/Univ. of Luxembourg
Intended status: Informational P. Thubert
Expires: April 14, 2014 cisco
T. Watteyne
Linear Technology / Dust Networks
Q. Wang
Univ. of Sci. and Tech. Beijing
October 11, 2013
Terminology in IPv6 over the TSCH mode of IEEE 802.15.4e
draft-palattella-6tisch-terminology-00
Abstract
6TiSCH proposes an architecture for an IPv6 multilink subnet that is
composed of a high speed powered backbone and a number of
IEEE802.15.4e TSCH wireless networks attached and synchronized by
backbone routers. This document extends existing terminology
documents available for Low-power and Lossy Networks to provide
additional terminology elements.
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 RFC
2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 14, 2014.
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 9
6.3. External Informative References . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
A new breed of Time Sensitive Networks is being developed to enable
traffic that is highly sensitive to jitter and quite sensitive to
latency. Such traffic is not limited to voice and video, but also
includes command and control operations such as in industrial
automation or in-vehicle sensors and actuators.
At IEEE802.1, the "Audio/Video Task Group", was renamed TSN for Time
Sensitive Networking. The IEEE802.15.4 Medium Access Control (MAC)
has evolved with IEEE802.15.4e which provides in particular the Time
Slotted Channel Hopping (TSCH) mode for industrial-type applications.
Both provide 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.
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2. Terminology
The draft extends [I-D.ietf-roll-terminology] and use terms from RFC
6550 [RFC6550] and RFC 6552 [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
IEEE 802.15.4e. It defines a set of IETF sublayers and
protocols (in particular, for setting up a schedule with
a centralized or distributed approach, managing the
resource allocation), as well as the architecture to bind
them together, for use in IPv6 TSCH based networks.
6F: IPv6 Forwarding. One of the three forwarding model
supported by 6TiSCH. Packets are routed at layer 3,
where QoS and RED operations are expected to prioritize
flows with differentiated services.
6top: 6top is the adaptation layer between TSCH and upper
layers like 6LoWPAN and RPL. It is defined in
[I-D.draft-wang-6tsch-6top].
6top Data Convey Model: Model describing how the 6top adaptation
layer feeds the data flow coming from upper layers into
TSCH. It is composed by an I-MUX module, a MUX module, a
set of priority queues, and a PDU (Payload Data Unit).
ASN: Absolute Slot Number, the timeslot counter, incremented
by one at each timeslot. It is wide enough to not roll
over in practice. See
[I-D.watteyne-6tsch-tsch-lln-context].
Blacklist: Set of frequencies which should not be used for
communication.
BBR: Backbone Router. In the 6TiSCH architecture, it is an
LBR and also a NEAR. It performs ND proxy operations
between registered devices and classical ND devices that
are located over the backbone.
Bundle: A group of equivalent scheduled cells, i.e. cells
identified by different [slotOffset, channelOffset],
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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
contains. Given the length of the slotframe, the size of
the bundle translates directly into bandwidth, either
logical, or physical.
Cell: A single element in the TSCH sloframe, identified by a
slotOffset value, a channelOffset value, a slotframe_ID
and Hopping_Sequence_ID. A cell can be scheduled or
unscheduled. During an unscheduled cell, the node does
not communicate. When a cell is scheduled, it is
assigned a MAC-layer slotframe identifier, a neighbor MAC
address (which can be the broadcast address), and one or
more of the following flags: TX, RX, shared,
timeskeeping, hard. A broadcast cell is an alias for "a
scheduled cell with neighbor address the broadcast
address".
ChannelOffset: Identifies a row in the TSCH slotframe. The number
of available channelOffsets is equal to the number of
available frequencies. The channelOffset translates into
a frequency when the communication takes place, resulting
in channel hopping, as detailed in
[I-D.watteyne-6tsch-tsch-lln-context].
Communication Paradigm: It is Associated with the Information Model
[RFC3444] of the state that is exchanged, and indicates:
the location of that state (e.g., centralized vs.
distributed, RESTful, etc.), the numbers of parties
(e.g., P2P vs. P2MP) and the relationship between parties
(e.g., master/slave vs. peers) at a high level of
protocol abstraction. Layer 5 client/server REST is a
typical communication paradigm, but industrial protocols
also use publish/subscribe which is P2MP and source/sink
which is MP2MP and primarily used for alarms and alerts
at the application layer. At layer 3, basic flooding,
P2P synchronization and path-marking (RSVP-like) are
commonly used paradigms, whereas at layer 2, master/slave
polling and peer-to-peer forwarding are classical
examples.
Dedicated Cell: A cell that is reserved for a given node to transmit
to a specific neighbor.
Distributed cell reservation: A reservation of a cell done by one or
more in-network entities (typically a connection
endpoint).
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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 an advertising node to
announce the presence of the network. It contains
information about the timeslot length, the current ASN
value, the slotframes and timeslots the beaconing mote is
listening on, and a 1-byte join priority (i.e., number of
hops separating the node sending the EB, and the PAN
coordinator).
FF: 6LoWPAN Fragment Forwarding. It is one of the three
forwarding model supported by 6TiSCH. The 6LoWPAN
Fragment is used as a label for switching at the 6LoWPAN
sublayer, as defined in
[I-D.thubert-roll-forwarding-frags].
GMPLS: Generalized Multi-Protocol Label Switching, a 2.5 layer
service that is used to forward packets based on the
concept of generalized labels.
Hard Cell: A scheduled cell that is locked, i.e., it cannot be moved
by 6top in the schedule. See
[I-D.draft-wang-6tsch-6top].
Hopping Sequence: 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
[I-D.watteyne-6tsch-tsch-lln-context].
IE: Information Elements, a list of Type-Length-Value
containers placed at the end of the MAC header, used to
pass data between layers or devices. A small number of
types are defined by TSCH, but a range of types is
available for extensions, and thus, is exploitable by
6TiSCH. See [I-D.watteyne-6tsch-tsch-lln-context].
I-MUX module: Inverse-Multiplexer, a classifier that receives
6LoWPAN frames and places them into priority queues.
Interaction Model: It is a particular way of implementing a
communication paradigm. Defined at a lower level of
abstraction, it includes protocol-specific details such
as a particular method (e.g., a REST GET) and a Data
Model for the state to be exchanged.
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KMP: Key Managment Protocol.
LBR: 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 incompatible
IEEE802.15.4e terminology. In the context of the 6TiSCH
architecture, which applies to Low Power Lossy Networks
(LLNs), an IPv6 subnet is usually not congruent to a
single link and techniques such as IPv6 Neighbor
Discovery Proxying and Routing Over LLNs are required to
achieve reachability within the multilink subnet. A link
is distinct from a track. In fact, link local addresses
are not expected to be used over a track for end to end
communication. Finally, from the Layer 3 perspective
(where the inner complexities of TSCH operations are
hidden to enable classical IP routing and Forwarding), a
single radio interface may be seen as a number of Links
with different capabilities for unicast or multicast
services.
Logical Cell: A cell that corresponds to granted bandwidth but is
only lazily associated to a physical cell, based on
usage.
MAC: Medium Access Control.
MUX module: Multiplexer, the entity that dequeues frames from
priority queues and associates them to a cell for
transmission.
NEAR: Energy Aware Default Router, as defined in
[I-D.chakrabarti-nordmark-6man-efficient-nd].
NME: Network Management Entity, the entity in the network
managing cells and other device resources. It may
cooperate with the PCE. It interacts with LLN nodes
through the backbone router.
PANA: Protocol for carrying Authentication for Network Access,
as defined in [RFC5191] . It is the protocol used in the
6TiSCH architecture for handling authentication during
the join process.
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PCE: Path Computation Element, the entity in the network which
is responsible for building and maintaining the TSCH
schedule, when centralized scheduling is used.
PCE cell reservation: The reservation of a cell done by the PCE.
PCE track reservation: The reservation of a track done by the PCE.
QoS: Quality of Service.
SA: Security Association.
Shared Cell: A cell that is used by more than one transmitter nodes
at the same time and on the same channelOffset. Only
cells with TX flag can be marked as "shared". A backoff
algorithm is used to resolve contention.
SlotOffset: Identifies a column in the TSCH schedule, i.e., the
number of timeslots since the beginning of the current
iteration of the slotframe.
Slotframe: A MAC-level abstraction that is internal to the node and
contains a series of timeslots of equal length and
priority. 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.
Soft Cell: A scheduled cell that is not locked, i.e., it may be
moved in the schedule within a same slotframe by 6top, as
described in [I-D.draft-wang-6tsch-6top].
TF: Track Forwarding. It is the simplest and fastest
forwarding model supported by 6TiSCH. It is a G-MPLS-
like forwarding model. The input cell characterises the
flow and indicates the output cell.
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. The length of the timeslot determines
the maximum size of the frame that can be exchanged.
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Time Source Neighbor: A neighbor a node uses as its time reference,
and to which it needs to keep its clock synchronized. A
node can have one or more time source neighbors.
Track: A determined sequence of cells along a multi-hop path.
It is typically the result of a reservation. The node
that initializes the process for 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.
TSCH: Time Slotted Channel Hopping, a medium access mode of the
[IEEE802154e] standard which uses time synchronization to
achieve ultra low-power operation and channel hopping to
enable high reliability.
TSCH Schedule: A matrix of cells, each cell indexed by a slotOffset
and a channelOffset. The slotframe size (the "width" of
the matrix) is the number of timeslots it contains. The
number of channelOffset values (the "height" of the
matrix) is equal to the number of available frequencies.
The TSCH schedule contains all the scheduled cells from
all slotframes and is sufficient to qualify the
communication in the TSCH network.
3. IANA Considerations
This specification does not require IANA action.
4. Security Considerations
This specification is not found to introduce new security threat.
5. Acknowledgements
Thanks to the IoT6 European Project (STREP) of the 7th Framework
Program (Grant 288445).
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444, January
2003.
[RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
Yegin, "Protocol for Carrying Authentication for Network
Access (PANA)", RFC 5191, May 2008.
[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012.
[RFC6552] Thubert, P., "Objective Function Zero for the Routing
Protocol for Low-Power and Lossy Networks (RPL)", RFC
6552, March 2012.
6.2. Informative References
[I-D.chakrabarti-nordmark-6man-efficient-nd]
Chakrabarti, S., Nordmark, E., Thubert, P., and M.
Wasserman, "Efficiency aware IPv6 Neighbor Discovery
Optimizations", draft-chakrabarti-nordmark-6man-efficient-
nd-02 (work in progress), July 2013.
[I-D.draft-sudhaakar-6tisch-coap]
Sudhaakar, R., Ed. and P. Zand, "6TiSCH Data Model for
CoAP-00 (work in progress) ", October 2013.
[I-D.draft-wang-6tsch-6top]
Wang, Q., Ed., Vilajosana, X., and T. Watteyne, "6TiSCH
Operation Sublayer (6top). draft-wang-6tisch-6top-00 (work
in progress) ", October 2013.
[I-D.ietf-roll-terminology]
Vasseur, J., "Terms used in Ruting for Low power And Lossy
Networks", draft-ietf-roll-terminology-13 (work in
progress), October 2013.
[I-D.ohba-6tsch-security]
Chasko, S., Das, S., Lopez, R., Ohba, Y., Thubert, P., and
A. Yegin, "Security Framework and Key Management Protocol
Requirements for 6TSCH", draft-ohba-6tsch-security-01
(work in progress), July 2013.
[I-D.thubert-6tisch-architecture]
Thubert, P., Assimiti, R., and T. Watteyne, "An
Architecture for IPv6 over the TSCH mode of IEEE
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IEEE802.15.4e", draft-thubert-6tisch-architecture-00 (work
in progress), October 2013.
[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.
[I-D.vilajosana-6tisch-minimal]
Vilajosana, X. and K. Pister, "Minimal 6TiSCH
Configuration", draft-vilajosana-6tisch-minimal-00 (work
in progress), October 2013.
[I-D.watteyne-6tsch-tsch-lln-context]
Watteyne, T., Palattella, M., and L. Grieco, "Using
IEEE802.15.4e TSCH in an LLN context: Overview, Problem
Statement and Goals", draft-watteyne-6tsch-tsch-lln-
context-02 (work in progress), May 2013.
6.3. External Informative References
[IEEE802154e]
IEEE standard for Information Technology, "IEEE std.
802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
Networks (LR-WPANs) Amendament 1: MAC sublayer", April
2012.
Authors' Addresses
Maria Rita Palattella (editor)
University of Luxembourg
Interdisciplinary Centre for Security, Reliability and Trust
4, rue Alphonse Weicker
Luxembourg L-2721
LUXEMBOURG
Phone: (+352) 46 66 44 5841
Email: maria-rita.palattella@uni.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, Hebei 100083
China
Phone: +86 (10) 6233 4781
Email: wangqin@ies.ustb.edu.cn
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