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6TiSCH                                                      Q. Wang, Ed.
Internet-Draft                           Univ. of Sci. and Tech. Beijing
Intended status: Informational                             X. Vilajosana
Expires: April 23, 2014                  Universitat Oberta de Catalunya
                                                             T. Watteyne
                                                       Linear Technology
                                                        October 20, 2013


                    6TiSCH Operation Sublayer (6top)
                       draft-wang-6tisch-6top-00

Abstract

   The recently published [IEEE802154e] standard formalizes the concept
   of link-layer resources in LLNs.  Nodes are synchronized and follow a
   schedule.  A cell in that schedule corresponds to an atomic link-
   layer resource, and can be allocated to any pair of neighbors in the
   network.  This allows the schedule to be built to tightly match each
   node's bandwidth, latency and energy constraints.  The [IEEE802154e]
   standard does not, however, present a mechanism to do so, as building
   and managing the schedule is out of scope of the standard.  This
   document describes the 6TiSCH Operation Sublayer (6top) and the
   commands it provides to upper network layers such as RPL or GMPLS.
   The set of functionalities includes feedback metrics from cell states
   so network layers can take routing decisions, TSCH configuration and
   control procedures, and the support for decentralized and centralized
   scheduling.  In addition, 6top can be configured to enable packet
   switching at layer 2.5, analogous to GMPLS.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 23, 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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  6TiSCH Operation Sublayer (6top)  . . . . . . . . . . . . . .   4
     2.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Cell Model  . . . . . . . . . . . . . . . . . . . . . . .   5
       2.2.1.  hard cells  . . . . . . . . . . . . . . . . . . . . .   7
       2.2.2.  soft cells  . . . . . . . . . . . . . . . . . . . . .   7
     2.3.  Data Convey Model . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Commands  . . . . . . . . . . . . . . . . . . . . . . . .   9
       2.4.1.  Cell Commands . . . . . . . . . . . . . . . . . . . .  11
       2.4.2.  Slotframe Commands  . . . . . . . . . . . . . . . . .  14
       2.4.3.  Monitoring Commands . . . . . . . . . . . . . . . . .  15
       2.4.4.  Statistics Commands . . . . . . . . . . . . . . . . .  16
       2.4.5.  Network Formation Commands  . . . . . . . . . . . . .  17
       2.4.6.  Time Source Neighbor Commands . . . . . . . . . . . .  19
       2.4.7.  Neighbor Commands . . . . . . . . . . . . . . . . . .  20
       2.4.8.  Queueing Commands . . . . . . . . . . . . . . . . . .  21
       2.4.9.  Security Commands . . . . . . . . . . . . . . . . . .  23
       2.4.10. Data Commands . . . . . . . . . . . . . . . . . . . .  25
       2.4.11. Label Switching Commands  . . . . . . . . . . . . . .  26
     2.5.  Message Formats . . . . . . . . . . . . . . . . . . . . .  27
       2.5.1.  Information Elements  . . . . . . . . . . . . . . . .  27
       2.5.2.  Packet Formats  . . . . . . . . . . . . . . . . . . .  35
     2.6.  Time Sequence . . . . . . . . . . . . . . . . . . . . . .  40
       2.6.1.  Network Formation . . . . . . . . . . . . . . . . . .  40
       2.6.2.  Creating soft cells . . . . . . . . . . . . . . . . .  41
       2.6.3.  Deleting soft cells . . . . . . . . . . . . . . . . .  42
       2.6.4.  Maintaining soft cells  . . . . . . . . . . . . . . .  42
       2.6.5.  Creating hard cells . . . . . . . . . . . . . . . . .  43
       2.6.6.  Deleting hard cells . . . . . . . . . . . . . . . . .  43
     2.7.  Statistics  . . . . . . . . . . . . . . . . . . . . . . .  43
       2.7.1.  Statistics Metrics  . . . . . . . . . . . . . . . . .  43



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       2.7.2.  Statistics Configuration  . . . . . . . . . . . . . .  44
     2.8.  Monitoring  . . . . . . . . . . . . . . . . . . . . . . .  44
       2.8.1.  Monitor Configuration . . . . . . . . . . . . . . . .  44
       2.8.2.  Actuation . . . . . . . . . . . . . . . . . . . . . .  45
     2.9.  Label Switching . . . . . . . . . . . . . . . . . . . . .  45
   3.  Using 6top  . . . . . . . . . . . . . . . . . . . . . . . . .  46
     3.1.  RPL on 6top . . . . . . . . . . . . . . . . . . . . . . .  46
       3.1.1.  Support to Neighbor Discovery and Parent Selection  .  46
       3.1.2.  Support of Rank Computation . . . . . . . . . . . . .  47
       3.1.3.  Support of Control Messages Broadcast . . . . . . . .  47
       3.1.4.  Support for QoS . . . . . . . . . . . . . . . . . . .  48
     3.2.  GMPLS on 6top . . . . . . . . . . . . . . . . . . . . . .  49
       3.2.1.  Cell Reservation Support for GMPLS on 6top  . . . . .  50
       3.2.2.  Supporting QoS  . . . . . . . . . . . . . . . . . . .  50
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  50
     4.1.  Normative References  . . . . . . . . . . . . . . . . . .  50
     4.2.  Informative References  . . . . . . . . . . . . . . . . .  51
     4.3.  External Informative References . . . . . . . . . . . . .  54
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  55

1.  Introduction

   As presented in [I-D.watteyne-6tsch-tsch-lln-context], the
   [IEEE802154e] standard defines the mechanisms for a TSCH node to
   communicate, given a schedule.  It does not, however, define the
   mechanism to build and maintain the TSCH schedule, match that
   schedule to the multi-hop paths maintained by a network layer such as
   RPL or a 2.5 layer such as GMPLS, adapt the resources allocated
   between neighbor nodes to the data traffic flows, enforce a
   differentiated treatment for data generated at the application layer
   and signalling messages needed by 6LoWPAN and RPL to discover
   neighbors, react to topology changes, self-configure IP addresses, or
   manage keying material.

   In a TSCH network, the MAC layer is not in charge of setting up the
   schedule that controls the connectivity graph of the network and the
   resources allocated to each cell in that topology.  This
   responsibility is left to an upper layer, defined in this document
   and called "6top".

   This document describes the 6TiSCH Operation Sublayer (6top) and the
   main commands provided to upper network layers such as RPL or GMPLS.
   The set of functionalities include feedback metrics from cell state
   so the network layer can take routing decisions, TSCH configuration
   and control procedures, and support for the different scheduling
   mechanisms defined in [I-D.thubert-6tisch-architecture]. 6top
   addresses the set of functionalities described in
   [I-D.watteyne-6tsch-tsch-lln-context].



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   For example, network formation in a TSCH network is handled by the
   use of Enhanced Beacons (EB).  EBs include information for joining
   nodes to be able to synchronize and set up an initial network
   topology.  However, [IEEE802154e] does not specify how the period of
   EBs is configured, nor the rules for a node to select a particular
   node to join. 6top offers a set of commands so control mechanisms can
   be introduced on top of TSCH to configure nodes to join a specific
   node and obtain a unique 16-bit identifier from the network.  Once a
   network is formed, 6top maintains the network's health, allowing for
   nodes to stay synchronized.  It supplies mechanisms to manage each
   node's time source neighbor and configure the EB interval.  Network
   layers running on top of 6top take advantage of the TSCH MAC layer
   information so routing metrics, topological information, energy
   consumption and latency requirements can be adjusted to TSCH, and
   adapted to application requirements.

   TSCH requires a mechanism to manage its schedule; 6top provides a set
   of commands for upper layers to set up specific schedules, either
   explicitly by detailing specific cell information, or by allowing
   6top to establish a schedule given a bandwidth or latency
   requirement. 6top is designed to enable decentralized, centralized or
   hybrid scheduling solutions. 6top enables internal TSCH queuing
   configuration, size of buffers, packet priorities, transmission
   failure behavior, and defines mechanisms to encrypt and authenticate
   MAC slotframes.

   As described in [label-switching-154e], due to the slotted nature of
   a TSCH network, it is possible to use a label switched architecture
   on top of TSCH cells.  As a cell belongs to a specific track, a label
   header is not needed at each packet; the input cell (or bundle) and
   the output cell (or bundle) uniquely identify the data flow.  The
   6top sublayer provides operations to manage the cell mappings.

2.  6TiSCH Operation Sublayer (6top)

2.1.  Overview

   6top is a sublayer which is the next-higher layer for TSCH (Figure
   1), as detailed in [I-D.thubert-6tisch-architecture]. 6top offers
   both management and data interfaces to an upper layer.  It includes
   monitoring and statistics collection, both of which are configurable
   through the management interface.

   Protocol Stack







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   +-----------------------------------+
   | PCEP | CoAP |      | 6LoWPAN |    |
   | PCC  | DTLS | PANA |    ND   |RPL |
   +------------------------------------------+
   | TCP  |     UDP     |     ICMP     | RSVP |
   +------------------------------------------+
   |                 IPv6                     |
   +------------------------------------------+
   |               6LoWPAN HC                 |
   +------------------------------------------+
   |                 6top                     |
   +------------------------------------------+
   |          IEEE802.15.4e TSCH              |
   +------------------------------------------+
   |             IEEE802.15.4                 |
   +------------------------------------------+

                                 Figure 1

   6top distinguishes between hard cells and soft cells.  It therefore
   requires an extra flag to all cells in the TSCH schedule, as detailed
   in Section 2.2.

   When a higher layer gives 6top a 6LoWPAN packet for transmission,
   6top maps it to the appropriate outgoing priority-based queue, as
   detailed in Section 2.3.

   All commands of the management and data interfaces are detailed in
   Section 2.4.  This set of commands is designed to support
   decentralized, centralized and hybrid scheduling solutions.

   6top defines TSCH Information Elements (IEs) for neighbors nodes to
   negotiate scheduling cells in the TSCH schedule.  The format of those
   is given in Section 2.5.  Example data exchanges between neighbor
   nodes are illustrated in Section 2.6.

   Section 2.7 defines how 6top gathers statistics (e.g., link quality,
   energy level, queue usage), and what commands an upper layer can use
   to configure and retrieve statistics.

   6top can be configured to monitor the cells it has scheduled in order
   to detect cells with poor performance.  It can automatically re-
   allocate those cells inside the TSCH schedule.  This behavior is
   described in Section 2.8

2.2.  Cell Model





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   [IEEE802154e] defines a set of options attached to each cell.  A cell
   can be a Transmit cell, a Receive cell, a Shared cell or a
   Timekeeping cell.  These options are not exclusive, as a cell can be
   qualified with more than one of them.  The MLME-SET-LINK.request
   command defined in [IEEE802154e] uses a linkOptions bitmap to specify
   the options of a cell.  Acceptable values are:

         b0 = Transmit

         b1 = Receive

         b2 = Shared

         b3 = Timekeeping

         b4-b7 = Reserved

   Only Transmit cells can also be marked as Shared cells.  When the
   shared bit is set, a back-off procedure is applied to handle
   collisions.  Shared behavior does not apply to Receive cells.

   6top allows an upper layer to schedule a cell at a specific
   slotOffset and channelOffset, in a specific slotframe. 6top follows
   the hard cell reservation process described in Section 2.6.5.

   In addition, 6top allows an upper layer to schedule a certain amount
   of bandwidth to a neighbor, without having to specify the exact
   slotOffset(s) and channelOffset(s). 6top follows the soft cell
   reservation process described in Section 2.6.2.  Once bandwidth is
   reserved, 6top is in charge of ensuring that this requirement is
   continuously satisfied, as described in Section 2.8. 6top dynamically
   reallocates cells if needed, and over-provisions if required.

   6top allows an upper layer to associate a hard/soft cell with a
   specific track by using a TrackID.  A TrackID is a tuple
   (TrackOwnerAddr,InstanceID), where TrackOwnerAddr is the address of
   the node which initializes the process of creating the track, i.e.,
   the owner of the track; and InstanceID is an instance identifier
   given by the owner of the track.  InstanceID comes from upper layer;
   InstanceID could for example be the local instance ID defined in RPL.

   If the TrackID is set to (0,0), the cell can be used by the best-
   effort QoS configuration or as a Shared cell.  If the TrackID is not
   set to (0,0), i.e., the cell belongs to a specific track, the cell
   MUST not be set as Shared cell.

   Given this mechanism, 6top defines hard cells (which have been
   requested specifically) and soft cells (which can be reallocated



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   dynamically).  The hard/soft flag is introduced by the 6top sublayer
   as an extension of LinkOption flags defined in [IEEE802154e].  This
   option is mandatory; all cells are either hard or soft.

   With the addition of the Hard/Soft flag, the resulting flags are:

         b0 = Transmit

         b1 = Receive

         b2 = Shared

         b3 = Timekeeping

         b4 = Hard (1)/Soft (0)

         b5-b7 = Reserved

2.2.1.  hard cells

   A hard cell is a cell that cannot be dynamically reallocated by 6top.
   A hard cell is uniquely identified by the following tuple:

         slotframe ID: ID of the slotframe this cell is part of.

         slotOffset: the slotOffset for the cell.

         channelOffset: the channelOffset for the cell.

         LinkOption bitmap: bitmap as defined in Section 2.2, including
         the hard/soft bit which MUST be set to 1.

2.2.2.  soft cells

   A soft cell is a cell that can be reallocated by 6top dynamically.
   The hard/soft bit MUST be set to 0.  This cell is installed by 6top
   given a specific bandwidth requirement.  Soft cells are installed
   through the soft cell negotiation procedure described in Section 2.6.

2.3.  Data Convey Model

   Once a TSCH schedule is established, 6top is responsible for feeding
   the data from the upper layer into TSCH.  This section describes how
   6top shapes data from the upper layer (e.g., RPL, 6LoWPAN), and feeds
   it to TSCH.  Since 6top is a sublayer between TSCH and 6LoWPAN, the
   properties associated with a packet/fragment from the upper layer
   includes the next hop neighbor (DestAddr) and expected sending
   priority of the packet (Priority), and/or TrackID(s).  The output to



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   TSCH is the fragment corresponding to the next active cell in the
   TSCH schedule.

   6top Data Convey Model

                       |
                       | (DestAddr, Priority, Fragment)
                       |
   +---------------------------------------+
   |                 I-MUX                 |
   +---------------------------------------+
     |       |       |       |    ....   |
     |       |       |       |           |
   +---+   +---+   +---+   +---+       +---+
   |   |   |   |   |   |   |   |       |   |
   |Q1 |   |Q2 |   |Q3 |   |Q4 |       |Qn |
   |   |   |   |   |   |   |   |       |   |
   +---+   +---+   +---+   +---+       +---+
     |       |       |       |           |
     |       |       |       |           |
   +---------------------------------------+
   |                 MUX                   |
   +---------------------------------------+
                      |
                      |
                    +---+
                    |PDU|
                    +---+
                      |
                      | TSCH MAC-payload
                      |

                                 Figure 2

   In Figure 2, Qi represents a queue, which is either broadcast or
   unicast, and is assigned a priority.  The number of queues is
   configurable.  The relationship between queues and tracks is
   configurable.  For example, for a given queue, only one specific
   track can be used, all of the tracks can be used, or a subset of the
   tracks can be used.

   When 6top receives a packet to transmit through a Send.data command
   (Section 2.4.10), the I-MUX module selects a queue in which to insert
   it.  If the packet's destination address is a unicast (resp.
   broadcast) address, it will be inserted into a unicast (resp.
   broadcast) queue.





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   The MUX module is invoked at each scheduled transmit cell by TSCH.
   When invoked, the MUX module goes through the queues, looking for the
   best matching frame to send.  If it finds a frame, it hands it over
   to TSCH for transmission.  If the next active cell is a broadcast
   cell, it selects a fragment only from broadcast queues.

   How the MUX module selects the best frame is configurable.  The
   following rules are a typical example:

         The frame's layer 2 destination address MUST match the neighbor
         address associated with the transmit cell.

         If the transmit cell is associated with a specific track, the
         frames in the queue corresponding to the TrackID have the
         highest priority.

         If the transmit cell is not associated with a specific track,
         i.e., TrackID=(0,0), frames from a queue with a higher priority
         MUST be sent before frames from a queue with a lower priority.

   Further rules can be configured to satisfy specific QoS requirements.

2.4.  Commands

   6top provides a set of commands as the interface with the higher
   layer.  Most of these commands are related to the management of
   slotframes, cells and scheduling information. 6top also provides an
   interface allowing an upper layer to retrieve status information and
   statistics.  This section describes the following commands provided
   by 6top.

         CREATE.hardcell: Section 2.4.1.1

         CREATE.softcell: Section 2.4.1.2

         READ.cell: Section 2.4.1.3

         UPDATE.cell: Section 2.4.1.4

         DELETE.hardcell: Section 2.4.1.5

         DELETE.softcell: Section 2.4.1.6

         REALLOCATE.softcell: Section 2.4.1.7

         CREATE.slotframe: Section 2.4.2.1

         READ.slotframe: Section 2.4.2.2



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         UPDATE.slotframe: Section 2.4.2.3

         DELETE.slotframe: Section 2.4.2.4

         CONFIGURE.monitoring: Section 2.4.3.1

         READ.monitoring: Section 2.4.3.2

         CONFIGURE.statistics: Section 2.4.4.1

         READ.statistics: Section 2.4.4.2

         RESET.statistics: Section 2.4.4.3

         CONFIGURE.eb: Section 2.4.5.1

         READ.eb: Section 2.4.5.2

         CONFIGURE.timesource: Section 2.4.6.1

         READ.timesource: Section 2.4.6.2

         CREATE.neighbor: Section 2.4.7.1

         READ.all.neighbor: Section 2.4.7.2

         READ.neighbor: Section 2.4.7.3

         UPDATE.neighbor: Section 2.4.7.4

         DELETE.neighbor: Section 2.4.7.5

         CREATE.queue: Section 2.4.8.1

         READ.queue: Section 2.4.8.2

         READ.queue.stats: Section 2.4.8.3

         UPDATE.queue: Section 2.4.8.4

         DELETE.queue: Section 2.4.8.5

         CONFIGURE.security: Section 2.4.9.1

         CONFIGURE.security.macKeyTable: Section 2.4.9.2

         CONFIGURE.security.macSecurityLevelTable:Section 2.4.9.3




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         Send.data: Section 2.4.10.1

         Receive.data: Section 2.4.10.2

         LabelSwitching.map: Section 2.4.11.1

         LabelSwitching.unmap: Section 2.4.11.2

2.4.1.  Cell Commands

   6top provides the following commands to manage TSCH cells.

2.4.1.1.  CREATE.hardcell

   Creates one or more hard cells in the schedule.  Fails if the cell
   already exists.  A cell is uniquely identified by the tuple
   (slotframe ID, slotOffset, channelOffset).

   To create a hard cell, the upper layer specifies:

         slotframe ID: ID of the slotframe this timeslot will be
         scheduled in.

         slotOffset: the slotOffset for the cell.

         channelOffset: channelOffset for the cell.

         LinkOption bitmap: bitmap as defined in Section 2.2

         target node address: the address of that node to communicate
         with over this cell.  In case of broadcast cells this is the
         broadcast address.

         TrackID: ID of the track the cell will belong to.

   6top schedules the cell and marks it as a hard cell, indicating that
   it cannot reschedule this cell.

2.4.1.2.  CREATE.softcell

   To create soft cell(s), the upper layer specifies:

         slotframe ID: ID of the slotframe the cell(s) will be scheduled
         in

         number of cells: the required number of soft cells.

         LinkOption bitmap: bitmap as defined in Section 2.2



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         target node address: the address of the node to communicate
         with over the cell(s).  In case of broadcast cells this is the
         broadcast address.

         TrackID: ID of the track the cell(s) will belong to.

         QoS level: the cell redundancy policy.  The policy can be for
         example STRICT, BEST_EFFORT, etc.

   6top is responsible for picking the exact slotOffset and
   channelOffset in the schedule, and ensure that the target node choose
   the same cell and TrackID. 6top marks these cells as soft cell,
   indicating that it will continuously monitor their performance and
   reschedule if needed.

   6top deals with the allocation process by negotiation with the target
   node.  The negotiation process is described in Section 2.6.2.  The
   command returns the list of created cells defined by (slotframe ID,
   slotOffset, channelOffset).  It fails if the required number of cells
   is higher than the available number of cells in the schedule.  It
   fails if the negotiation with the target node fails.  It fails if the
   LinkOption bitmap indicates that the cell(s) MUST be Hard.

2.4.1.3.  READ.cell

   Given a (slotframe ID, slotOffset, channelOffset), retrieves the cell
   information.  Fails if the cell does not exist.  The returned
   information contains:

         slotframe ID: ID of the slotframe where this cell is installed.

         slotOffset: the slotOffset for the cell.

         channelOffset: the selected channelOffset for the cell.

         LinkOption bitmap: bitmap as defined in Section 2.2

         target node address: the target address of that cell.  In case
         of broadcast cells this is the broadcast address.

         TrackID: ID of the track the cell will belong to.

   A read command can be issued for any cell, hard or soft.

2.4.1.4.  UPDATE.cell

   Update a hard cell, i.e., re-allocate it to a different slotOffset
   and/or channelOffset.  Fails if the cell does not exist.  Requires



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   both old (slotframe ID, slotOffset, channelOffset) and new (slotframe
   ID, slotOffset, channelOffset) as parameters.  And, the type of cell,
   target node address and TrackID are the fields that cannot be
   updated.  Soft cells MUST NOT be updated by the UPDATE.cell command.
   REALLOCATE.softcell (Section 2.4.1.7) MUST be used instead.

2.4.1.5.  DELETE.hardcell

   To remove a hard cell, the upper layer specifies:

         slotframe ID: the ID of the slotframe where this cell is
         installed.

         slotOffset: the slotOffset for the cell.

         channelOffset: the selected channelOffset for the cell.

   This removes the hard cell from the node's schedule.

2.4.1.6.  DELETE.softcell

   To remove a (number of) soft cell(s), the upper layer specifies:

         slotframe ID: ID of the slotframe where this cell is installed.

         number of cells: the number of cells to be removed

         LinkOption bitmap: bitmap as defined in Section 2.2

         target node address: the target address of that cell.  In case
         of broadcast cells this is the broadcast address.

         TrackID: ID of the track the cell will belong to.

   In the case a soft cell wants to be re-allocated from the allocated
   cell so a hard cell can be installed instead, the REALLOCATE.softcell
   (Section 2.4.1.7) MUST be used.

2.4.1.7.  REALLOCATE.softcell

   To force a re-allocation of a soft cell, the upper layer specifies:

         slotframe ID: ID of the slotframe where the cell is allocated.

         slotOffset: the slotOffset for that cell.

         channelOffset: the channelOffset for that cell.




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   The reallocated cell will be installed in a different slotOffset,
   channelOffset but slotframe and TrackID remain the same.  Hard cells
   MUST NOT be reallocated.

2.4.2.  Slotframe Commands

   6top provides the following commands to manage TSCH slotframes.

2.4.2.1.  CREATE.slotframe

   Creates a new slotframe.  Returns the slotframe ID that corresponds
   to its priority (SlotFrameHandle).  The command requires:

         number of timeslots: the required number of timeslots in the
         slotframe.

   Fails if the number of required timeslots is less than zero.

2.4.2.2.  READ.slotframe

   Returns the information of a slotframe given its slotframe ID.  The
   command returns:

         slotframe ID: ID of the slotframe.  (SlotFrameHandle)

         number of timeslots: the number of timeslots in the slotframe.

   Fails if the slotframe ID does not exist.

2.4.2.3.  UPDATE.slotframe

   Change the number of timeslots in a slotframe.  The command requires:

         slotframe ID: ID of the slotframe.

         number of timeslots: the number of timeslots to be updated.

   Fails if the number of required timeslots is less than zero.  Fails
   if the slotframe ID does not exist.

2.4.2.4.  DELETE.slotframe

   Deletes a slotframe.  The command requires:

         slotframe ID: ID of the slotframe.

   Fails if the slotframe ID does not exist.




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2.4.3.  Monitoring Commands

   Monitoring commands provide the means for upper layers to configure
   whether 6top must ensure the required bandwidth.  This procedure is
   achieved through overprovisioning according to cell status feedback.
   Monitoring is also in charge of reallocating soft cells that are
   under the required QoS.  The mechanism is described in Section 2.8.

2.4.3.1.  CONFIGURE.monitoring

   Configures the level of QoS the Monitoring process MUST enforce.  The
   command requires:

         slotframe ID: ID of the slotframe.

         target node address: the target neighbor address.

         enforce policy: The policy used to enforce the QoS
         requirements.  Can be for example DISABLE, BEST_EFFORT, STRICT,
         OVER-PROVISION, etc.

   Fails if the slotframe ID does not exist.

2.4.3.2.  READ.monitoring.status

   Reads the current Monitoring status.  Requires the following
   parameters.

         slotframe ID: the ID of the slotframe.

         target node address: the target neighbor address.

   Returns the QoS levels for that Target node on that slotframe.

         allocated_hard: Number of hard cells allocated.

         allocated_soft: Number of soft cells allocated.

         provisioned: the extra provisioned cells. 0 if CONFIGURE.qos
         enforce is DISABLE.

         QoS: the current QoS.  Including overprovisioned cells, i.e
         what bandwidth is being obtained including the overprovisioned
         cells.

         RQoS: the real QoS without provisioned cells.  What is the
         actual bandwidth without taking into account the
         overprovisioned cells.



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   Fails if the slotframe ID does not exist.

2.4.4.  Statistics Commands

   6top keeps track of TSCH statistics for upper layers to adapt
   correctly to medium changes.  The exact metrics for statistics are
   out of scope but the present commands SHOULD be used to configure and
   read monitored information regardless of the specific metric.

2.4.4.1.  CONFIGURE.statistics

   Configures Statistics process.  The command requires:

         slotframe ID: ID of the slotframe.  If empty monitors all
         slotframe IDs

         slotOffset: specific slotOffset to be monitored.  If empty all
         timeslots are monitored

         channelOffset: specific channelOffset to be monitored.  If
         empty all channels are monitored.

         target node address: the target neighbor address.  If empty,
         all neighbor nodes are monitored.

         metric: metric to be monitored.  This MAY be PDR, ETX, queuing
         statistics, energy-related metrics, etc.)

         window: time window to be considered for the calculations.  If
         0 all historical data is considered.

         enable: Enables statistics or disables them.

   Fails if the slotframe ID does not exist.  The statistics service can
   be configured to retrieve statistics at different levels.  For
   example to aggregate information by slotframe ID, or to retrieve
   statistics for a particular timeslot, etc.  The CONFIGURE.statistics
   enables flexible configuration and supports empty parameters that
   will force 6top to conduct statistics on all members of that
   dimension.  For example, if ChannelOffset is empty and metric is set
   as PDR, then, 6top will conduct the statistics of PDR on all of
   channels.









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2.4.4.2.  READ.statistics

   Reads a metric for the specified dimension.  Information is
   aggregated according to the parameters.  The command requires:

         slotframe ID: ID of the slotframe.  If empty aggregates
         information of all slotframe IDs

         slotOffset: the specific slotOffset for which the information
         is required.  If empty all timeslots are aggregated

         channelOffset: the specific channelOffset for which the
         information is required.  If empty all channels are aggregated.

         target node address: the target neighbor address.  If empty all
         neighbor addresses are aggregated.

         metric: metric to be read.

   Returns the value for the requested metric.

   Fails if empty metric or metric does not exits.

2.4.4.3.  RESET.statistics

   Resets the gathered statistics.  The command requires:

         slotframe ID: ID of the slotframe.  If empty resets the
         information of all slotframe IDs

         slotOffset: the specific slotOffset for which the information
         wants to be reset.  If empty statistics from all timeslots are
         reset

         channelOffset: the specific channelOffset for which the
         information wants to be reset.  If empty all statistics for all
         channels are reset.

         target node address: the target neighbor address.  If empty all
         neighbor addresses are aggregated.

         metric: metric to be reset.

   Fails if empty metric or metric does not exits.

2.4.5.  Network Formation Commands





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   EBs need to be configured, including their transmission period, the
   slotOffset and channelOffset that they SHOULD be sent on, and the
   join priority they contain.  The parameters for that command are
   optional and enable flexible configuration of EBs.  If slotframe ID
   is specified, the EBs will be configured to use that specific
   slotframe; if not, they will use the first slotframe where the
   configured slotOffset is allocated.  The slotOffset enforces the EB
   to a specific timeslot.  In case slotOffset parameter is not present,
   the EB is sent in the first available transmit timeslot.  In case
   channelOffset parameter is not set, the EB is configured to use the
   first available channel.

2.4.5.1.  CONFIGURE.eb

   Configures EBs.  The command requires:

         slotframe ID: ID of the slotframe where the EBs MUST be sent.
         Zero if any slotframe can be used.

         slotOffset: the slotOffset where the EBs MUST be sent.  Zero if
         any timeslot can be used.

         channelOffset: the channelOffset where the EBs MUST be sent.
         Zero if any channelOffset can be used.

         period: the EBs period, in seconds.

         Expiration: when the EBs periodicity will stop.  If Zero the
         period never stops.

         priority: the joining priority model that will be used for
         advertisement.  Joining priority MAY be for example
         SAME_AS_PARENT, RANDOM, BEST_PARENT+1 or DAGRANK(rank) as
         decribed in in [I-D.vilajosana-6tisch-minimal].

   Fails if the tuple (slotframe ID, slotOffset, channelOffset) is
   already scheduled.

2.4.5.2.  READ.eb

   Reads the EBs configuration.  No parameters are required.

   Returns the current EBs configuration for that slotframe, which
   contains:

         slotframe ID: the slotframe where the EB is being sent.

         slotOffset: the slotOffset where the EBs is being sent.



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         channelOffset: the channelOffset the EBs is being sent on.

         period: the EBs period.

         Expiration: when the EBs periodicity stops.  If 0 the period
         never stops.

         priority: the joining priority that this node advertises.

   Fails if the slotframe ID does not exist.

2.4.6.  Time Source Neighbor Commands

   Commands to select time source neighbors.

2.4.6.1.  CONFIGURE.timesource

   Configures the Time Source Neighbor selection process.  More than one
   time source neighbor can be selected.  The command requires:

         selection policy: The policy used to select the time source
         neighbor.  The policy MAY be for example ALL_PARENTS,
         BEST_CONNECTED, LOWEST_JOIN_PRIORITY, etc.

   Fails if any of the time source neighbors do not exist or it is not
   reachable.

2.4.6.2.  READ.timesource

   Retrieves information about the time source neighbors of that node.
   The command does not require any parameter.

   Returns the following information for each of the time sources:

         target node: address of the time source neighbor.

         statistics: includes for example minimum, maximum, average time
         correction for that time source neighbor

         policy: the used policy

   Fails if the slotframe ID or no time source neighbors exist.









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2.4.7.  Neighbor Commands

   Commands to manage neighbor table.  The commands SHOULD be used by
   the upper layer to query the neighbor related information and by the
   lower layer to keep track of neighbors information.

2.4.7.1.  CREATE.neighbor

   Creates an entry for a neighbor in the neighbor table.

         neighbor address: The address of the neighbor.

         neighbor stats: for example, RSSI of the last received packet
         from that neighbor, ASN when that neighbor has been added, etc.

   Returns whether the neighbor is created or not.

2.4.7.2.  READ.all.neighbor

   Returns the list of neighbors of that node.  Fails if empty.  For
   each neighbor in the list it returns:

         neighbor address: The address of the neighbor.

         neighbor stats: for example, RSSI of the last received packet
         from that neighbor, ASN when that neighbor has been added,
         packets received from that neighbor, packets sent to it, etc.

2.4.7.3.  READ.neighbor

   Returns the information of a specific neighbor of that node specified
   by its neighbor address.  Fails if it does not exists.  For that
   neighbor it returns:

         neighbor address: The address of the neighbor.

         neighbor stats: for example, RSSI of the last received packet
         from that neighbor, ASN when that neighbor has been added,
         packets received from that neighbor, packets sent to it, etc.

2.4.7.4.  UPDATE.neighbor

   Updates an entry for a neighbor in the neighbor table.  Fails if the
   neighbor does not exist.  Updates stats parameters.  Requires:

         neighbor address: The address of the neighbor.





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         neighbor stats: for example, RSSI of the last received packet
         from that neighbor, ASN when that neighbor has been added, etc.

   Returns whether the neighbor is updated or not.

2.4.7.5.  DELETE.neighbor

   Deletes a neighbor given its address.  Fails if the neighbor does not
   exists.

2.4.8.  Queueing Commands

   Queues need to be configured.  This includes queue length,
   retransmission policy, discarding of packets, etc.

2.4.8.1.  CREATE.queue

   Creates and Configures Queues.  The command SHOULD be applied for
   each required queue.  The command requires:

         txqlength: the desired transmission queue length.

         rxqlength: the desired reception queue length.

         numrtx: number of allowed retransmissions.

         age: discard packet according to its age on the queue. 0 if no
         discards are allowed.

         rtxbackoff: retransmission backoff in number of slotframes. 0
         if next available timeslot wants to be used.

         statswindow: window of time used to compute stats.

         queue priority: the priority of this queue.

         TrackIDs: a set of TrackIDs.  While it is empty, no specific
         track is associated with the queue

   Returns the queue ID.

2.4.8.2.  READ.queue

   Reads the queue configuration.  Requires the queue ID.

   The command returns:

         txqlength: the transmission queue length.



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         rxqlength: the reception queue length.

         numrtx: number of allowed retransmissions.

         age: maximum age of a packet before being discarded. 0 if no
         discards are allowed.

         rtxbackoff: retransmission backoff in number of slotframes. 0
         if next available timeslot is used.

2.4.8.3.  READ.queue.stats

   Reads the queue stats.  Requires queue ID.

   The command returns:

         txqlengthstats: average, maximum, minimum length of the
         transmission queue.

         rxqlengthstats: average, maximum, minimum length of the
         reception queue.

         numrtxstats: average, maximum, minimum number of
         retransmissions.

         agestats: average, maximum, minimum age of a packet in the
         queue.

         rtxbackoffstats: average, maximum, minimum retransmission
         backoff.

         queue priority: the priority of this queue.

         TrackIDs: a set of TrackIDs.

2.4.8.4.  UPDATE.queue

   Update a Queue.  The command requires:

         queueid: the queue ID.

         txqlength: the desired transmission queue length.

         rxqlength: the desired reception queue length.

         numrtx: number of allowed retransmissions.





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         age: discard packet according to its age on the queue. 0 if no
         discards are allowed.

         rtxbackoff: retransmission backoff in number of slotframes. 0
         if next available timeslot wants to be used.

         statswindow: window of time used to compute stats.

         queue priority: the desired priority of this queue.

         TrackIDs: the desired set of TrackIDs.

2.4.8.5.  DELETE.queue

   Deletes a Queue.  The command requires the queue ID.  All packets in
   the queue are discarded and the queue is deleted.

2.4.9.  Security Commands

   The following commands are used to manage underlying layer security.
   In that case 6top acts as delegating interface to the security
   attributes defined in the MAC PIB ([IEEE802154]).

2.4.9.1.  CONFIGURE.security

   Enables/Disables Security and configures the MAC PIB.  The command
   requires:

         enable: enables underlying layer security.

         macAutoRequestSecurityLevel: the security level used for
         automatic data requests as described by table 60 in
         [IEEE802154].

         macAutoRequestKeyIdMode: the key identifier mode used for
         automatic data requests as described by table 60 in
         [IEEE802154].

         macAutoRequestKeySource: the originator of the key for
         automatic data requests as described by table 60 in
         [IEEE802154].

         macAutoRequestKeyIndex: the index of the key used for automatic
         data requests as described by table 60 in [IEEE802154].

         macDefaultKeySource: the originator of the default key used for
         key identifier mode 0x01 as described by table 60 in
         [IEEE802154].



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         macPANCordinatorExtendedAddress: Address of the PAN coordinator
         as described by table 60 in [IEEE802154].

         macPANCordinatorShortAddress: Short address of the PAN
         coordinator as described by table 60 in [IEEE802154].

2.4.9.2.  CONFIGURE.security.macKeyTable

   Configures Security Keys.  The command requires:

         KeyIdLookupList: list of keyIdLookupDescriptor Entries as
         defined by table 61 in [IEEE802154].

         DeviceDescriptorHandleList: Implementation specific list of
         devices that are using this key.  As defined by table 61 in
         [IEEE802154].

         KeyUsageList: List of slotframe types on which this key is
         being used as specified by table 61 in [IEEE802154].

         Key: 16 octets key.  As specified by table 61 in [IEEE802154].

2.4.9.3.  CONFIGURE.security.macSecurityLevelTable

   Configures the set of security levels.  The command requires:

         FrameType: Slotframe type as defined by table 63 in
         [IEEE802154].

         Command Identifier: The command identifier as defined by table
         63 in [IEEE802154].

         Security Minimum: The minimum required security level as
         specified by table 63 in [IEEE802154].

         Device Override Security Minimum: whether the minimum security
         level can be overridden as specified by table 63 in
         [IEEE802154].

         Allowed Security Levels: the key identifier field that
         identifies the key that is being used as specified by table 63
         in [IEEE802154].









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2.4.9.4.  Security Command Behavior

   6top offers the interface to upper layers so underlying MAC layer can
   be configured.  In that sense, 6top only delegates the
   functionalities to the MAC security services.  For more details
   Section 7 on [IEEE802154] and its amendments on [IEEE802154e] SHOULD
   be referred.

2.4.10.  Data Commands

2.4.10.1.  Send.data

   The command used by upper layers to queue a packet so underlying TSCH
   sends it.  According to the specific priority, the packet is pushed
   into a Queue with the equivalent priority or following a criteria out
   of scope.  Once a packet is inserted into a queue it waits to be
   transmitted by TSCH according to the model defined in Section 2.3.
   If the queue is full or destination address is not a L2 neighbor of
   the node, failure to enqueue will be indicated to the caller.

   The required parameters are:

         src address: L2 address

         dest address: L2 unicast or broadcast address

         priority: packet priority, usually is consistent with queue
         priority

         message length: the length of the message

         message: control message or data message

         securityLevel:As defined by [IEEE802154e].

2.4.10.2.  Receive.data

   The command is invoked whenever a packet is received and inserted
   into a reception queue.  The method acts as a callback function to
   notify to the upper layers the received message.  Upper layers MUST
   terminate this indication.

   The function has the following parameters:

         src address: L2 source address

         dest address: L2 unicast or broadcast destination address




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         priority: packet priority, usually is consistent with queue
         priority

         message length: the length of the message.

         message: control message or data message

2.4.11.  Label Switching Commands

2.4.11.1.  LabelSwitching.map

   The command used by an upper layer to map an input cell or a bundle
   of input cells to an output cell or a bundle of output cells. 6top
   stores this mapping and makes sure that the packets are forwarded at
   the specific output cell/bundle.  Label Switching is enabled by the
   specified bundle as soon as the mapping is installed.

   The required parameters are:

         input cells: list of input cells (one or more cells in a
         bundle).  Each input cells is described by an unique tuple
         (slotOffset, channelOffset, destination address).

         output cells: list of output cells (one or more cells in a
         bundle).  Each output cells is described by an unique tuple
         (slotOffset, channelOffset, destination address).

         load balancing policy: A policy for load balance cell usage.
         The policy is out of scope, however an example can be use ROUND
         ROBIN policy within the cells of the same bundle.

2.4.11.2.  LabelSwitching.unmap

   The command used by upper layers to unmap one input cell or a bundle
   of input cells to an output cell or a bundle of output cells.  The
   mapping is removed from the state kept by 6top.

   The required parameters are:

         input cells: list of input cells (one or more cells in a
         bundle).  Each input cells is described by an unique tuple
         (slotOffset, channelOffset, destination address).

         output cells: list of output cells (one or more cells in a
         bundle).  Each output cells is described by an unique tuple
         (slotOffset, channelOffset, destination address).





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2.5.  Message Formats

   6top has to negotiate the scheduling of soft cells with neighbor
   nodes.  This negotiation happens through 6top-specific TSCH
   Information Elements, the format of which is defined in this section.
   For completeness, this section also details the formats of the IEs
   already defined in [IEEE802154e] and presented here without
   modification.

   6top messages can contain one or more IEs.  Section 2.5.1 defines the
   different IEs used by 6top, both the ones used without modification
   from [IEEE802154e], and the new ones defined by this document.
   Section 2.5.2 shows how several IEs are assembled to form the
   different frames used by 6top.

2.5.1.  Information Elements

   [IEEE802154e] defines Information elements (IEs).  IEs are formatted
   data objects consisting of an ID, a length, and a data payload used
   to pass data between layers or devices.  [IEEE802154e] defines Header
   IEs and Payload IEs; 6top only uses Payload IEs.  A Payload IE
   includes one or more IEs, and ends with a termination IE (ID = 0xf,
   see [IEEE802154e]).

   6top uses the following Information Elements, some defined in
   [IEEE802154e], others introduced in this document.

         Defined in [IEEE802154e] and used by 6top without modification:



               TSCH Synchronization IE (Section 2.5.1.1)

               TSCH Slotframe and Link IE (Section 2.5.1.2)

               TSCH Timeslot Template IE (Section 2.5.1.3)

               TSCH Channel Hopping IE (Section 2.5.1.4)

         Defined by 6top:



               6top Opcode IE (Section 2.5.1.5)

               6top Bandwidth IE (Section 2.5.1.6)

               6top TrackID IE (Section 2.5.1.7)



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               6top Generic Schedule IE (Section 2.5.1.8)

2.5.1.1.  TSCH Synchronization IE

   A Synchronization IE (SyncIE) contains Information allowing a node to
   synchronize to a TSCH network, including the current ASN and a join
   priority.  Synchronization IE MUST be included in all TSCH Enhanced
   Beacons.

   6top re-uses this IE as defined in [IEEE802154e].

   Format of a TSCH Synchronization IE (SyncIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|          ASN                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 ASN                           | Join Priority |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 3

   Length=6

   SubID=0x1a

   T=0, i.e., short type

   ASN (5 octets) contains the Absolute Slot Number corresponding to the
   timeslot in which the TSCH Enhanced Beacon is sent.

   The Join Priority can be used by a joining device to select among
   beaconing devices when multiple beacons are heard.  The PAN
   coordinator's join priority is zero.  A lower value of join priority
   indicates that the device is the preferred one to connect to.  As
   suggested by [I-D.vilajosana-6tisch-minimal], the beaconing device's
   join priority is its DAGRank(rank).

2.5.1.2.  TSCH Slotframe and Link IE

   The Slotframe and Link IE (FrameAndLinkIE) contains one or more
   slotframes and their respective cells that a beaconing device
   advertises to allow other devices to join the network.

   6top re-uses this IE as defined in [IEEE802154e].

   Format of a TSCH Slotframe and Link IE (FrameAndLinkIE).




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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|  NumFrame     |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
   |                                                               |
   //               Slotframe and cell information                //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 4

   Length=variable

   SubID=0x1b

   T=0, i.e., short type

   NumFrame is set to the total number of slotframe descriptors
   contained in the TSCH Enhanced Beacon.

   Format of a slotframe descriptor.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   FrameID      |            FrameLen          |   NumCell     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //          Cell information for each cell (5x NumCell)        //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 5

   The FrameID field shall be set to the slotframeHandle that uniquely
   identifies the slotframe.

   The FrameLen field shall be set to the size of the slotframe in
   number of timeslots.

   The NumCell field shall be set to the number of cells that belong to
   the specific slotframe identified by the slotframeHandle.

   Format of a Cell information.








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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        SlotOffset             |        ChannelOffset          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  LinkOption   |
   +-+-+-+-+-+-+-+-+

                                 Figure 6

   SlotOffset shall be set to the slotOffset of this cell.

   ChannelOffset shall be set to the channelOffset of this cell.

   LinkOption indicates whether this cell is a TX cell, an RX cell, or a
   SHARED TX cell, whether the device to which it is being linked is to
   be used for clock synchronization, and whether this cell is hard
   cell.

2.5.1.3.  TSCH Timeslot Template IE

   Timeslot Template IE (SlotTemplateIE) defines Timeslot template being
   used by the TSCH device.

   6top re-uses this IE as defined in [IEEE802154e].

   Format of a TSCH Timeslot Template IE (SlotTemplateIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|  TemplateID   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 7

   Length=1

   SubID=0x1c

   T=0, i.e., short type

   TemplateID shall be set to a Timeslot template handle.  The full
   timeslot template, which contains the macTimeslotTemplate of TSCH
   (total 25 octets), MAY be included.(see [IEEE802154e]).

2.5.1.4.  TSCH Channel Hopping IE

   Channel Hopping IE (ChHoppingIE) defines the Hopping Sequence being
   used by the TSCH device.



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   6top re-uses this IE as defined in [IEEE802154e].

   Format of a TSCH Channel Hopping IE (ChHoppingIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Length         | SubID |T| HopSequenceID |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 8

   Length=1

   SubID=0x09

   T=1, i.e., long type

   HopSequenceID shall be set to a Hopping Sequence handle.  The full
   Hopping Sequence information MAY be included. (see [IEEE802154e]).

2.5.1.5.  6top Opcode IE

   6top Opcode IE (OpcodeIE) defines operation codes of packets in 6top
   sublayer.

   This IE is not present in [IEEE802154e] and is defined by 6top.

   Format of a 6top Opcode IE (OpcodeIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|   OpcodeID    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 9

   Length=1

   SubID=0x41

   T=0, i.e., short type

   OpcodeID field shall be set to one of the following codes.

         0x00: Reserve Soft Cell Request

         0x01: Reserve Soft Cell Response




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         0x02: Remove Soft Cell Request

         0x03: Reserve Hard Cell Request

         0x04: Remove Hard Cell Request

2.5.1.6.  6top Bandwidth IE

   Bandwidth IE (BwIE) defines the number of cells to be reserved or
   actually be reserved.

   This IE is not present in [IEEE802154e] and is defined by 6top.

   Format of a 6top Bandwidth IE (BwIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|    FrameID    |   NumCell     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 10

   Length=2

   SubID=0x42

   T=0, i.e., short type

   FrameID MAY be set to the SlotFrameHandle to identify the slotframe
   from which cells are reserved.  FrameID field MAY be set to NOP,
   which means no specific slotframe is associated.

   NumCell shall be set to the number of cells.  When BwIE is combined
   with the OpecodeID of Reserve Soft Cell Request, NumCell presents how
   many cells are required to reserve; and when BwIE is combined with
   the OpecodeID of Reserve Soft Cell Response, NumCell presents how
   many cells are reserved successfully.

2.5.1.7.  6top TrackID IE

   TrackID IE (TrackIdIE) describes the track which the reserved/removed
   cell(s) are associated with.

   This IE is not present in [IEEE802154e] and is defined by 6top.

   Format of a 6top TrackID IE (TrackIdIE).





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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|OwnerInstID|rev|               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
   //                                                              //
   |                   TrackOwnerAddr                              |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 11

   Length=3 or 7.  When length=3, TrackOwnerAddr is 2 bytes short
   address, and when length=7, TrackOwnerAddr is 6 bytes long address.

   SubID=0x43

   T=0, i.e., short type

   The combination of TrackOwnerAddr and OwnerInstId represents a
   specific TrackID.

2.5.1.8.  6top Generic Schedule IE

   Generic Schedule IE (ScheduleIE) describes cell sets.  In different
   packets, ScheduleIE represents different information.  See
   Section 2.5.2 for more detail.

   This IE is not present in [IEEE802154e] and is defined by 6top.

   Format of a 6top Generic Schedule IE (ScheduleIE).

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Length      |    SubID    |T|                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   //                   Schedule Body                             //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 12

   Length=variable

   SubID=0x44

   T=0, i.e., short type




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   Schedule Body carries one or more schedule object.  An object MAY
   carry a TLV (Type-Length-Value), which MAY itself comprise other
   TLVs.  TLV format is as follows.  Type: 1 byte, Length: 1 byte,
   Value: variable

   The following are some examples of schedule object TLV.

   Example 1.  Cell Set TLV

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type=1      |    Length     |     FrameID   |  NumCell    |F|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        CellObjects                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 13

   FrameID shall be set to the slotframeHandle that uniquely identifies
   the slotframe.

   NumCell shall be set to the number of cells that belong to the
   specific slotframe identified by the slotframeHandle.

   F=1 means the specified cells equals to what are listed in
   CellObjects, and F=0 means the specified cells equals to what are not
   listed in CellObjects.

   CellObjects carries the information for one or more cells, including
   SlotOffset, ChannelOffset, LinkOption (Figure 6).

   Example 2.  Schedule Matrix TLV

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type=2      |    Length     |  FrameID      |StartSlotOffset|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |StartSLotOffset|    NumSlot    |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   //                 SlotBitMap (2x NumSlot)                     //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 14




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   FrameID field MUST be set to the slotframeHandle that uniquely
   identifies the slotframe.

   StartSlotOffset field (2 octets) MUST be set to the slotOffset in the
   specific slotframe identified by the slotframeHandle.

   NumSlot field MUST be set to the number of timeslots from
   StartSlotOffset in the specific slotframe identified by the
   slotframeHandle.

   SlotBitMap (per timeslot) indicates for the given timeslot which
   channels are specified.  For the 16 channels in 2.4GHz band, 2-octets
   are used to indicate which channel is specified.  For example, given
   a timeslot and a SlotBitmap with value (10001000,00010000); the
   bitmap represents that ChannelOffset-0, ChannelOffset-4,
   ChannelOffset-11 are specified.

2.5.2.  Packet Formats

   This section describes the packets used in 6top to form a network,
   reserve/maintain bandwidth using soft cells, and reserve/remove hard
   cells in both the transmitter side and receiver sides.  Each of these
   packets uses one or more IEs defined in Section 2.5.1.

2.5.2.1.  TSCH Enhanced Beacon

   The TSCH Enhanced Beacon is used to announce the presence of the
   network and allows new nodes to join.  It is an Enhanced Beacon
   packet defined in [IEEE802154e] with the following Payload IEs:

         TSCH Synchronization IE (Section 2.5.1.1)

         TSCH Timeslot Template IE (Section 2.5.1.3)

         TSCH Channel Hopping IE (Section 2.5.1.4)

         TSCH Slotframe and Link IE (Section 2.5.1.2)

   Payload IE of TSCH Enhanced Beacon Packet












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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|             SyncIE            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        SyncIE                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         SyncIE                |      SlotTemplateIE           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |SlotTemplateIE |               ChHoppingIE                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                        FrameAndLinkIE                       //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 15

   Length=variable

   GroupID=0x1, i.e., MLME IE

   T=1, i.e., payload IE

   See Section 2.5.1.1, Section 2.5.1.3, Section 2.5.1.4,Section 2.5.1.2
   for SyncIE, SlotTemplateIE, ChHoppingIE and FrameAndLinkIE.

2.5.2.2.  Soft Cell Reservation Request

   A Soft Cell Reservation Request packet is a DATA packet defined in
   [IEEE802154e] with the following payload IE.

   Payload IE of Soft Cell Reservation Request

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|          OpcodeIE             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OpcodeIE      |                  BwIE                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    BwIE       |                                               |
   +-+-+-+-+-+-+-+-+                                               |
   //                          ScheduleIE                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 16

   Length=variable



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   GroupID=0x1, i.e., MLME IE

   T=1, i.e., payload IE

   The OpcodeID field in the 3-octet OpcodeIE SHOULD be set to 0x00,
   indicates Reserve Soft Cell Request operation.

   The NumCell field in 4-octet BwIE SHOULD be set to the number of
   cells needed to be reserved.

   The ScheduleIE specifies a candidate cell set, from which the cells
   SHOULD be reserved.  ScheduleIE MAY be empty, means there is no
   constrain on which cells SHOULD not be reserved.

   In addition, TrackIdIE can be added in the packet to associate the
   reserved soft cells to a specific TrackID.

2.5.2.3.  Soft Cell Reservation Response

   Soft Cell Reservation Response is a DATA packet defined in
   [IEEE802154e] with the following payload IE.

   Payload IE of Soft Cell Reservation Response

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|          OpcodeIE             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OpcodeIE      |                  BwIE                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    BwIE       |                                               |
   +-+-+-+-+-+-+-+-+                                               |
   //                          ScheduleIE                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 17

   Length=variable

   GroupID=0x1, i.e., MLME IE

   T=1, i.e., payload IE

   The OpcodeID field in the 3-octet OpcodeIE SHOULD be set to 0x01,
   indicates Reserve Soft Cell Response operation.





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   The NumCell field in 4-octet BwIE SHOULD be set to the number of
   cells which have been reserved successfully.

   The ScheduleIE SHOULD specify all of the cells which have been
   reserved successfully.

   In addition, TrackIdIE can be added in the packet to associate the
   reserved soft cells to a specific TrackID.

2.5.2.4.  Soft Cell Remove Request

   Soft Cell Remove Request is a DATA packet defined in [IEEE802154e]
   with the following payload IE.

   Payload IE of Soft Cell Remove Request

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|          OpcodeIE             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OpcodeIE      |                                               |
   +-+-+-+-+-+-+-+-+                                               |
   //                          ScheduleIE                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 18

   Length=variable

   GroupID=0x1, i.e., MLME IE

   T=1, i.e., payload IE

   The OpcodeID field in the 3-octet OpcodeIE SHOULD be set to 0x02,
   indicates Remove Soft Cell Request operation.

   The ScheduleIE SHOULD specify all the cells that need to be removed.

2.5.2.5.  Hard Cell Reservation Request

   Hard Cell Reservation Request packet is a DATA packet defined in
   [IEEE802154e] with the following payload IE.

   Payload IE of Hard Cell Reservation Request






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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|          OpcodeIE             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OpcodeIE      |                                               |
   +-+-+-+-+-+-+-+-+                                               |
   //                          ScheduleIE                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 19

   Length=variable

   GroupID=0x1, i.e., MLME IE

   T=1, i.e., payload IE

   The OpcodeID field in the 3-octet OpcodeIE SHOULD be set to 0x03,
   indicates Reserve Hard Cell Request operation.

   The ScheduleIE SHOULD specify all the cell that need to be reserved.

   In addition, TrackIdIE can be added in the packet to associate the
   reserved hard cells to a specific TrackID.

2.5.2.6.  Hard Cell Remove Request

   Hard Cell Remove Request is a DATA packet defined in [IEEE802154e]
   with the following payload IE.

   Payload IE of Hard Cell Remove Request

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Length        |GroupID|T|          OpcodeIE             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | OpcodeIE      |                                               |
   +-+-+-+-+-+-+-+-+                                               |
   //                          ScheduleIE                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 20

   Length=variable

   GroupID=0x1, i.e., MLME IE



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   T=1, i.e., payload IE

   The OpcodeID field in the 3-octet OpcodeIE SHOULD be set to 0x04,
   indicates Remove Hard Cell Request operation.

   The ScheduleIE SHOULD specify all the cells that need to be removed.

2.6.  Time Sequence

   6top neighbors exchange 6top-specific packets in the following cases,
   each detailed in a subsection.

         Network formation (Section 2.6.1)

         Creating soft cells (Section 2.6.2)

         Deleting soft cells (Section 2.6.3)

         Maintaining soft cells (Section 2.6.4)

         Creating hard cells (Section 2.6.5)

         Deleting hard cells (Section 2.6.6)

2.6.1.  Network Formation

   Network formation consists of two processes: joining and maintenance.

2.6.1.1.  Joining

   A node already in the network sends out TSCH Enhanced Beacons
   periodically.

   When a node is joining an existing network, it listens for TSCH
   Enhanced Beacons.  After collecting one or more TSCH Enhanced BEACONs
   (the format of which is detailed in Section 2.5.2.1), the joining
   node MUST do the following.

         Initialize a neighbor table.  Establish a neighbor table and
         record all of the information described in the TSCH Enhanced
         BEACONs as its initial schedule with those neighbors.

         Select a time source neighbor.  According to the Joining
         Priority described by SyncIEs, the joining node chooses time
         source neighbors. 6top does not specify the criteria to choose
         time source neighbors from the Enhanced BEACONs.





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         Select cells for Enhanced Beacons.  The joining node selects
         one or more cells to indicate in its own Enhanced Beacons,
         which MAY be the same as the cells used by its neighbors for
         Enhanced Beacon broadcast, and record those cell(s) into the
         TSCH schedule with LinkType=ADVERTISING.

         Its Enhanced Beacons SHOULD include the cell(s) selected for EB
         purposes.  The EB cells MUST be configured with LinkOption to
         "Receive" and "Timekeeping", telling its neighbors that the
         cell is used for broadcast.

         Start broadcasting Enhanced Beacon and communicate with
         neighbors.

2.6.1.2.  Maintenance

   Nodes MAY broadcast Enhance Beacons on the cells marked with
   LinkType=ADVERTISING, and listen for Enhanced Beacons from neighbors
   on the cells with LinkOption = "Receive" and "Timekeeping".  If a
   cell with LinkType=ADVERTISING has both the "Receive" and
   "Timekeeping" LinkOptions set, which means that the cell is shared by
   neighbors and itself for broadcasting, then broadcasting Enhanced
   Beacon has higher priority.

   Whenever a node receives an Enhanced Beacon, it SHOULD update its
   schedule if there is a difference regarding to the cells used for
   synchronizing with the advertiser of the Enhanced Beacon.

2.6.2.  Creating soft cells

   The upper layer instructs 6top to schedule one or more soft cells by
   calling the Create soft cell command.  This command can also be
   called by the monitoring process internal to 6top.

   When receiving a Create soft cell command, Node A's 6top sublayer
   forms a Soft Cell Reservation Request packet which includes the BwIE
   and ScheduleIE Information Elements.  The BwIE indicates the number
   of cells to be reserved (N1); the ScheduleIE indicates set of a
   candidate cells from which the new cells SHOULD be selected.  If the
   ScheduleIE is empty, Node A indicates there is no constraint on cell
   selection.

   The Soft Cell Reservation Request is sent to the neighbor (Node B)
   with whom new cells need to be scheduled.  After receiving the Soft
   Cell Reservation Request, Node B selects the cells from the candidate
   cell set defined by the ScheduleIE in the Soft Cell Reservation
   Request, and forms a Soft Cell Reservation Response packet.  In the
   Cell Reservation Response packet, the BwIE indicates the number of



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   cells actually being reserved (N2); the ScheduleIE indicates those
   reserved cells.  If N2 is smaller than N1, node B indicates to node A
   that there are not enough qualified cells to be reserved.  Node B
   MUST record the reserved cells into its local schedule when sending
   the Soft Cell Reservation Response.  After receiving the Soft Cell
   Reservation Response, Node A MUST record the reserved cells into its
   local schedule.

   The policy to build a candidate cell set and the policy to select
   cells from the candidate cell set to reserve are out of scope.

   The format of Schedule Body is flexible.  For example, Node A can use
   Cell Set TLV defined in Figure 13 with field 'F' set to '0', and the
   CellObjects includes all of the cells being used by Node A. In
   another word, the cell candidate set is all of the cells not being
   included in the list defined by CellObjects.

   The behavior of the nodes when the soft cells negotiation fails is
   out of scope.

2.6.3.  Deleting soft cells

   The upper layer instructs 6top to delete one or more soft cells by
   calling the Delete soft cell command (Section 2.4.1.6).  This command
   can also be called by the monitoring process internal to 6top
   (Section 2.8).

   When receiving a Delete soft cell command, Node A's 6top sublayer
   selects cells to be removed from its local schedule, and creates a
   Soft Cell Remove Request, which includes a ScheduleIE Information
   Element.  The ScheduleIE indicates which specific cells to remove
   with a neighbor (Node B).  The cells specified in the ScheduleIE
   SHOULD be removed from local schedule of Node A when the Soft Cell
   Remove Request is sent to Node B. When receiving the Soft Cell Remove
   Request, the cells specified in the ScheduleIE SHOULD be removed from
   the local schedule of Node B.

   The policy to select cells corresponding to a Delete soft cell
   command is out of scope.

2.6.4.  Maintaining soft cells

   The monitoring process internal to 6top (Section 2.8) is responsible
   for monitoring and re-scheduling soft cells to meet some QoS
   requirements.  The monitoring process MAY issue a soft cell
   Maintenance command, which indicate a set of cells to be re-allocated
   in the TSCH schedule.




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   When receiving a soft cell Maintenance command, 6top initializes a
   Soft Cell Remove Request (Section 2.6.3) with the neighbor in
   question, followed by a Soft Cell Reservation Request
   (Section 2.6.2).

2.6.5.  Creating hard cells

   The upper layer instructs 6top to create one or more hard cells by
   calling the Create hard cell command.

   When receiving a Create hard cell command, Node A's 6top sublayer
   creates a Hard Cell Reservation Request, including a ScheduleIE.  The
   ScheduleIE indicates which specific cells with a neighbor (Node B) to
   be added.  The cells specified in the ScheduleIE SHOULD be added in
   local schedule of Node A while the Hard Cell Reserve Request is sent
   to Node B. When receiving the Hard Cell Reserve Request, the cells
   specified in the ScheduleIE SHOULD be added in the local schedule of
   Node B.

2.6.6.  Deleting hard cells

   The upper layer instructs 6top to delete one or more hard cells by
   calling the Delete hard cell command.

   When receiving a Delete hard cell command, Node A's 6top sublayer
   creates a Hard Cell Remove Request, including a ScheduleIE.  The
   ScheduleIE indicates which specific cells with a neighbor (Node B) to
   be removed.  The cells specified in the ScheduleIE SHOULD be removed
   from local schedule of Node A while the Hard Cell Remove Request is
   sent to Node B. When receiving the Hard Cell Remove Request, the
   cells specified in the ScheduleIE SHOULD be removed from the local
   schedule of Node B.

2.7.  Statistics

   The 6top Statistics Function (SF) is responsible for collecting
   statistics, which it can provide to an upper layer and the Monitoring
   Function (Section 2.8).

2.7.1.  Statistics Metrics

   6top is in charge of keeping statistics from a set of metrics
   gathered from the behavior of the TSCH layer.

   The statistics data related to node states and cell metrics SHOULD be
   provided to upper layer for management, e.g., for RPL to calculate
   the node's Rank or for GMPLS to the required bandwidth is met.  The
   specific algorithm to generate the statistics is out of scope.



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   However, the statistics component SHOULD include the following
   metrics:

   1.  LinkThroughput: associated with a link, Node A->Node B. For
       example, LinkThroughput can be calculated with:
       SUM(NumOfCell(i)*NumOfBytePerPacket)/(FrameLen(i)*SlotDuration)
       where NumOfCell(i) is the total number of cells from Node A to
       Node B in Slotframe-i, FrameLen(i) is the length of Slotframe-i.
       The unit is Byte/second.

   2.  Latency: associated with a link, Node A->Node B. For example,
       latency can be expressed as Minimum and Maximum Latency.  Minimum
       Latency = Min(MinNumOfSlot(i),i=1..) * SlotDuration and Maximum
       Latency = Max(MaxNumOfSlot(i),i=1..) * SlotDuration where,
       MinNumOfSlot(i) and MaxNumOfSlot(i) are the minimum or maximum
       number of timeslots between two dedicated cells from Node A to
       Node B in Slotframe-i, respectively.

   3.  LinkQuality.  For example, average LQI, ETX;

   4.  TafficLoad.  For example, Queue Full Rate, Queue Empty Rate;

   5.  NodeEnergy.  For example, E_E=E_bat / [E_0 (T-t)/T].

2.7.2.  Statistics Configuration

   The Statistics Function SHOULD be configurable.  The configuration
   parameters SHOULD include:

         LinkQualityStatisticsEn

         TafficLoadStatisticsEn

         DeviceStatisticsEn

   6top statistics function is enabled/disabled and configured by the
   commands defined in Section 2.4.4

2.8.  Monitoring

   The 6top Monitoring Function (MF) is responsible for monitoring cell
   quality, traffic load, and issuing soft cell Maintenance commands, or
   Create/Delete soft cell commands.  The data provided by the
   Statistics Function MAY be used as an input of MF in taking a
   monitoring decision.

2.8.1.  Monitor Configuration




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   Monitoring Function SHOULD be configurable.  The configuration
   parameters SHOULD include:

         MaintainCellEn.

         CreateDeleteCellEn.

         QosLevel.  QosLevel SHOULD associate with specific neighbor
         address.  QosLevel MAY reflect the latency constraint, cell
         quality constraint, and so on.  The value of QosLevel works as
         the bandwidth redundancy coefficient.

   The 6top monitoring function is enabled/disabled and configured by
   the commands defined in Section 2.4.3

2.8.2.  Actuation

   The cell quality statistics MAY be used to generate soft a cell
   Maintenance command, which triggers a soft cell Maintenance procedure
   (see Section 2.6.4).  The traffic load statistics MAY be used to
   generate internal Create (resp. Delete) soft cell commands, which
   trggiers a soft cell Reservation (resp. Remove) process (see
   Section 2.6.2 and Section 2.6.3).

   The policy to generate the soft cell Maintenance command and the
   policy to generate Create/Delete soft cell commands is out of scope.

   The policy to generate Create/Delete soft cell commands MAY take
   QosLevel into account.  For example, there are two slotframes
   existing, Slotframe-1 consists of 32 timeslots, Slotframe-2 consists
   of 96 timeslots; timeslot duration is 10ms; QosLevel=1.5.  If, from
   the traffic load statistics, MF determines that 2 packet/second
   SHOULD be added, then the MF generates a Create soft cell command,
   where FrameID=2, NumCell=3.

2.9.  Label Switching

   Label Switching Fuction (LS) in 6top is responsible for maintaining
   the mapping of input cells and output cells in the same track in a
   particular node.  By keeping that mapping, layer 3 routing can be
   avoided as packets are forwarded by the 6top sublayer according to
   the input cells they were received on.  The selected output cell is
   one of the cells that forward the packet to the subsequent hop in the
   track.  As cells can be grouped in bundles, 6top can maintain
   mappings from input bundles to output bundles and provide a policy to
   select the output cell according to the input cell.





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3.  Using 6top

   This part describes how 6top gives support to specific upper layers.

3.1.  RPL on 6top

   6top provides a set of functionalities so higher layers can obtain
   information about the status of the network and take advantage of the
   slotted structure to improve metric calculation and objective
   function optimization.  The following sections describe how RPL can
   make use of 6top sublayer.

   In order to optimize the combination of RPL and TSCH, 6top provides
   specific support to RPL in the following aspects:

         RPL Neighbor Discovery and Parent Selection

         RPL Rank Computation

         RPL Control Messages Broadcast

         QoS

3.1.1.  Support to Neighbor Discovery and Parent Selection

   The Section 2.4.7 defines a set of commands so the neighbor table can
   be managed and queried by RPL.  An entry to the neighbor table is
   inserted whenever an EBs is received at L2.  The EB causes the 6top
   sublayer to create an entry to the neighbors table.  A neighbor table
   entry contains a set of statistics with respect to that specific
   neighbor such as the ASN when the last packet has been received from
   that neighbor, a set of cell quality metrics (RSSI, LQI), number of
   packets sent to it or number of packets received from it amongst
   others. 6top updates that table upon sending or reception of a packet
   from/to a neighbor.  RPL can query at any time the neighbor table to
   retrieve information about a particular neighbor.  This information
   can be used to compute the routing objective function as for example
   the Zero Objective function as described in
   [I-D.vilajosana-6tisch-minimal].  Parent selection can also be driven
   by the information contained on the neighbor table as well as
   complemented with the cells statistics defined in Section 2.4.4 and
   Section 2.7.

   6top enables RPL to configure EB periodicity.  By controlling the EBs
   periodicity, RPL can configure how network dynamism and support to
   mobility are addressed, as more frequent beacons the more prone to
   cope with mobility.  Section 2.4.5 enables to configure how the
   network is formed and EBs periodicity.



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   RPL MAY want to select the policy to determine the time source
   neighbor, this can be interesting when time source neighbors can be
   aligned to the routing topology, i.e., the selected time source
   neighbor can be the node's favorite parent in a specific DODAG.
   Section 2.4.6 describes the 6top command to set up the desired
   policy.  The policy is selected by RPL and enforced by the 6top
   sublayer.

   The rule for 6top to select and maintain time source neighbors is as
   follows:

         The time source neighbor of a node SHOULD be a member of the
         node's neighbor set.

         Time source neighbors SHOULD be the neighbors which have a
         relatively lower join priority in the neighbor set.  A lower
         join priority indicates that the neighbor is closer to the TSCH
         PAN coordinator.

         The link between a node and one of its time source neighbors
         SHOULD be a good link quality.

3.1.2.  Support of Rank Computation

   The RPL objective function is computed using a set of metrics.  The
   [I-D.vilajosana-6tisch-minimal] defines how Zero Objective Function
   is used to configure the rank and metrics used from 6top statistics.
   The specific metrics, and how the objective function is calculated
   are out of scope.  However, 6top builds a set of functionalities to
   provide more accurate statistics of the underlying layer so the
   objective function can be accommodated to the nature of a TSCH MAC
   layer.

   6top provides statistics for rank computation as described in
   Section 2.4.4 and Section 2.7.  The function used to compute the rank
   based on those statistics is out of scope.  However, the provided
   metrics are aligned to the behavior of the TSCH MAC layer.

3.1.3.  Support of Control Messages Broadcast

   In RPL, some control messages, e.g., DIO in storing mode, need to be
   broadcast to all neighbor nodes.  The broadcast channel requirement
   has to be addressed by 6top by configuring TSCH to provide such a
   channel.

   In order to decouple the upper (RPL) layer from TSCH, instead of
   carrying DIO messages in Enhance Beacons, 6top introduces a mechanism
   to establish broadcast cells.



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   In TSCH schedule, every cell has the LinkType attribute.  If
   LinkType=ADVERTISING, indicates that the cell MAY be used to send an
   Enhanced Beacon.  When a node forms its Enhanced Beacon, the cell,
   with LinkType=ADVERTISING, SHOULD be included in the FrameAndLinkIE,
   and its LinkOption field SHOULD be set to the combination of
   "Receive" and "Timekeeping".  The receiver of the Enhanced Beacon MAY
   be listening at the cell to get the Enhanced Beacon ([IEEE802154e]).
   6top takes this way to establish broadcast channel, which not only
   allows TSCH broadcast Enhanced Beacon, but also allows an upper layer
   like RPL broadcast.

   To support DIO and DAO broadcasts, 6top uses the payload of a Data
   Packet to carry the DIO or DAO.  The message is inserted into the
   queue associated with the cells which LinkType is set to ADVERTISING.
   Then, taking advantage of the broadcast cell feature established with
   FrameAndLinkIE as described above, the data packet with DIO or DAO in
   the payload can be received by neighbors, which enforces to the
   maintenance of DODAG.

   A LinkOption combining "Receive" and "Timekeeping" bits indicates to
   the receivers of the Enhanced Beacon that the cell MUST be used as a
   broadcast cell.  The frequency of sending Enhance Beacon or other
   broadcast messages by upper layer is determined by the timers
   associated with the messages.  For example, the transmission of
   Enhance Beacons is triggered by a timer in 6top; transmission of a
   DIO message is triggered by the trickle timer of RPL.

3.1.4.  Support for QoS

   The TSCH MAC layer is decoupled from the upper layer, and the
   interaction between the upper layer ad TSCH is asynchronous.  This
   means that the MAC layer executes a schedule and checks at each
   timeslot according to the type of cell whether there is something to
   send or receive.  If that is the case the packet is transmitted and
   the MAC layer continues its operation.  When an upper layer sends a
   packet, this packet is pushed into a queue waiting to the MAC layer
   to read it and send it in a particular timeslot according to is
   destination and priority (Section 2.3). 6top provides a set of queue
   management operations which enable upper layers to create different
   queues and determine their priorities.  This allows different classes
   of traffic to be handled by the routing layer, i.e. inserting a
   packet to a specific queue according to its priority.

   A 6top implement MUST provide at least a Broadcast Queue, a Transmit
   Queue, and a Receive Queue.  RPL can configure the queues with
   Internal Queueing Command (Section 2.4.8.1).  The Broadcast Queue is
   associated with cells with LinkType=ADVERTISING in sender's schedule,
   and LinkOption="Receive" and "Timekeeping" in all neighbors'



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   schedule.  This indicates that the cells can be used as broadcast
   cells from the sender to its neighbors.  A Transmit Queue is
   associated with the dedicated Transmit cells or Shared Cells.  RPL
   can benefit from having different priority queues to improve latency
   or provide integrated services with different priorities, i.e.
   different traffic classes.

   Data Communication Commands (Section 2.4.10) can be used to send
   control messages and data messages.  The operation is used to insert
   a message to an specific queue.

   For example a suitable configuration can include two Broadcast Queues
   with priority High and Low, respectively; three Transmit Queues, with
   priority High, Mid, and Low, respectively; and one Receive Queue.

   When DestAddr is a broadcast address, its related MAC layer packets
   will be pushed into the Broadcast Queue with the corresponding
   priority. 6top is responsible for feeding these packets to TSCH at
   broadcast cells.

   When DestAddr is unicast address, its related MAC layer packets will
   be push into the Transmit Queue with corresponding priority. 6top is
   responsible for feeding these packets to TSCH at Transmit cells or
   Shared Cells.

   6top conducts a QoS policy, which is out of scope.  Here is an
   example.  Packets in higher priority queue MUST be sent out before
   the packets in lower priority queue.  Then, when there is an
   available broadcast/unicast cell, 6top checks the broadcast/unicast
   queue with higher priority first, if there is a packet, then feeds it
   to TSCH at the cell, otherwise it checks broadcast/unicast queue with
   lower priority further. 6top repeats the process, until it finds a
   broadcast/unicast packet to feed to TSCH or finds that all of
   broadcast/unicast queues are empty.

3.2.  GMPLS on 6top

   GMPLS is a 2.5 layer service that is used to forward packets based on
   the concept of generalized labels.  Labels are determined by a
   reservation protocol during the formation of a multi-hop path.  As
   defined by [RFC3471], [RFC3473] and [RFC4606] a generalized label
   identifies a flow of data through a set of nodes that conform to a
   multi-hop path.  Instead of being written implicitly into a field in
   each packet, as is the case in MPLS [RFC3031], the generalized label
   is kept at each node in the form of a table.  The table can be used
   to map input cells to output cells so routing decisions can be taken
   at that layer.




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   In order to optimize the combination of GMPLS and TSCH, 6top provides
   specific support to GMPLS in the following aspects:

         Cell Reservation Support

         QoS

3.2.1.  Cell Reservation Support for GMPLS on 6top

   The GMPLS control plane is used to send path reservation requests and
   reservation confirmations.  When reservation confirmations are
   received, GMPLS needs to configure the underlying MAC layer to
   provide the required bandwidth. 6top provides a set of commands to
   deal with bandwidth allocation, i.e., cell allocation.  Section 2.4.1
   describes the operations that GMPLS layer MAY use for cell
   configuration.  Note that 6top supports different types of
   reservations: soft cell and hard cell.  How the reservation
   requirements are expressed is out of scope, but 6top is able to
   handle a reservation done as a specific bandwidth requirement, done
   through specifying exact cells.

   The [I-D.vilajosana-6tisch-minimal] defines a pre-configured schedule
   that can be used to bootstrap the network.  Those cells can be seen
   as a GMPLS control plane where RPL routes can be formed and Track
   reservations issued.

   GMPLS can also give different priorities to its control plane and
   data plane.  It can for example be interesting to have a higher
   priority for control messages so the network adapts to new bandwidth
   requirements quickly.  In contrast, data plane messages can be given
   a higher priority when they need to meet higher throughput or lower
   latency. 6top provides commands (Section 2.4.8) to manage MAC layer
   queues and assign different priorities to them.

3.2.2.  Supporting QoS

   GMPLS can use 6top statistics to determine whether some QoS
   requirement is met.  Metrics defined in Section 2.7 and operations
   defined in Section 2.4.4 can be used by GMPLS to trigger new
   bandwidth allocation, or to map different input bundles to output
   bundles.

4.  References

4.1.  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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4.2.  Informative References

   [RFC2205]  Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, December 1998.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

   [RFC3036]  Andersson, L., Doolan, P., Feldman, N., Fredette, A., and
              B. Thomas, "LDP Specification", RFC 3036, January 2001.

   [RFC3471]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Functional Description", RFC 3471,
              January 2003.

   [RFC3473]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.

   [RFC3819]  Karn, P., Bormann, C., Fairhurst, G., Grossman, D.,
              Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
              Wood, "Advice for Internet Subnetwork Designers", BCP 89,
              RFC 3819, July 2004.

   [RFC4606]  Mannie, E. and D. Papadimitriou, "Generalized Multi-
              Protocol Label Switching (GMPLS) Extensions for
              Synchronous Optical Network (SONET) and Synchronous
              Digital Hierarchy (SDH) Control", RFC 4606, August 2006.

   [RFC4919]  Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
              over Low-Power Wireless Personal Area Networks (6LoWPANs):
              Overview, Assumptions, Problem Statement, and Goals", RFC
              4919, August 2007.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, September 2007.

   [RFC5548]  Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
              "Routing Requirements for Urban Low-Power and Lossy
              Networks", RFC 5548, May 2009.






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   [RFC5826]  Brandt, A., Buron, J., and G. Porcu, "Home Automation
              Routing Requirements in Low-Power and Lossy Networks", RFC
              5826, April 2010.

   [RFC5867]  Martocci, J., De Mil, P., Riou, N., and W. Vermeylen,
              "Building Automation Routing Requirements in Low-Power and
              Lossy Networks", RFC 5867, June 2010.

   [RFC5673]  Pister, K., Thubert, P., Dwars, S., and T. Phinney,
              "Industrial Routing Requirements in Low-Power and Lossy
              Networks", RFC 5673, October 2009.

   [RFC6282]  Hui, J. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              September 2011.

   [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.

   [RFC6568]  Kim, E., Kaspar, D., and JP. Vasseur, "Design and
              Application Spaces for IPv6 over Low-Power Wireless
              Personal Area Networks (6LoWPANs)", RFC 6568, April 2012.

   [RFC6606]  Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem
              Statement and Requirements for IPv6 over Low-Power
              Wireless Personal Area Network (6LoWPAN) Routing", RFC
              6606, May 2012.

   [RFC6755]  Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
              for OAuth", RFC 6755, October 2012.

   [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.

   [I-D.thubert-6tisch-architecture]
              Thubert, P., Assimiti, R., and T. Watteyne, "An
              Architecture for IPv6 over the TSCH mode of IEEE
              IEEE802.15.4e", draft-thubert-6tisch-architecture-00 (work
              in progress), October 2013.

   [I-D.palattella-6tisch-terminology]
              Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
              "Terminology in IPv6 over the TSCH mode of IEEE



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              802.15.4e", draft-palattella-6tisch-terminology-00 (work
              in progress), October 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.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-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.tsao-roll-security-framework]
              Tsao, T., Alexander, R., Daza, V., and A. Lozano, "A
              Security Framework for Routing over Low Power and Lossy
              Networks", draft-tsao-roll-security-framework-02 (work in
              progress), March 2010.

   [I-D.thubert-roll-asymlink]
              Thubert, P., "RPL adaptation for asymmetrical links",
              draft-thubert-roll-asymlink-02 (work in progress),
              December 2011.

   [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.ietf-roll-p2p-rpl]
              Goyal, M., Baccelli, E., Philipp, M., Brandt, A., and J.
              Martocci, "Reactive Discovery of Point-to-Point Routes in
              Low Power and Lossy Networks", draft-ietf-roll-p2p-rpl-17
              (work in progress), March 2013.

   [I-D.ietf-roll-trickle-mcast]
              Hui, J. and R. Kelsey, "Multicast Protocol for Low power
              and Lossy Networks (MPL)", draft-ietf-roll-trickle-
              mcast-05 (work in progress), August 2013.

   [I-D.thubert-6lowpan-backbone-router]




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              Thubert, P., "6LoWPAN Backbone Router", draft-thubert-
              6lowpan-backbone-router-03 (work in progress), February
              2013.

   [I-D.sarikaya-core-sbootstrapping]
              Sarikaya, B., Ohba, Y., Moskowitz, R., Cao, Z., and R.
              Cragie, "Security Bootstrapping Solution for Resource-
              Constrained Devices", draft-sarikaya-core-
              sbootstrapping-04 (work in progress), April 2012.

   [I-D.gilger-smart-object-security-workshop]
              Gilger, J. and H. Tschofenig, "Report from the 'Smart
              Object Security Workshop', 23rd March 2012, Paris,
              France", draft-gilger-smart-object-security-workshop-00
              (work in progress), October 2012.

   [I-D.phinney-roll-rpl-industrial-applicability]
              Phinney, T., Thubert, P., and R. Assimiti, "RPL
              applicability in industrial networks", draft-phinney-roll-
              rpl-industrial-applicability-02 (work in progress),
              February 2013.

   [I-D.ietf-core-coap]
              Shelby, Z., Hartke, K., and C. Bormann, "Constrained
              Application Protocol (CoAP)", draft-ietf-core-coap-18
              (work in progress), June 2013.

4.3.  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) Amendment 1: MAC sublayer", April
              2012.

   [IEEE802154]
              IEEE standard for Information Technology, "IEEE std.
              802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
              and Physical Layer (PHY) Specifications for Low-Rate
              Wireless Personal Area Networks", June 2011.

   [OpenWSN]  , "Berkeley's OpenWSN Project Homepage", ,
              <http://www.openwsn.org/>.

   [label-switching-154e]






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              Morell, A., Vilajosana, X., Lopez-Vicario, J., and T.
              Watteyne, "Label Switching over IEEE802.15.4e Networks.
              Transactions on Emerging Telecommunications Technologies",
              June 2013.

Authors' Addresses

   Qin Wang (editor)
   Univ. of Sci. and Tech. Beijing
   30 Xueyuan Road
   Beijing, Hebei  100083
   China

   Phone: +86 (10) 6233 4781
   Email: wangqin@ies.ustb.edu.cn


   Xavier Vilajosana
   Universitat Oberta de Catalunya
   156 Rambla Poblenou
   Barcelona, Catalonia  08018
   Spain

   Phone: +34 (646) 633 681
   Email: xvilajosana@uoc.edu


   Thomas Watteyne
   Linear Technology
   30695 Huntwood Avenue
   Hayward, CA  94544
   USA

   Phone: +1 (510) 400-2978
   Email: twatteyne@linear.com
















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