path: root/doc/rfc/rfc8376.txt

Internet Engineering Task Force (IETF)                   S. Farrell, Ed.
Request for Comments: 8376                        Trinity College Dublin
Category: Informational                                         May 2018
ISSN: 2070-1721


              Low-Power Wide Area Network (LPWAN) Overview

Abstract

   Low-Power Wide Area Networks (LPWANs) are wireless technologies with
   characteristics such as large coverage areas, low bandwidth, possibly
   very small packet and application-layer data sizes, and long battery
   life operation.  This memo is an informational overview of the set of
   LPWAN technologies being considered in the IETF and of the gaps that
   exist between the needs of those technologies and the goal of running
   IP in LPWANs.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8376.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  LPWAN Technologies  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  LoRaWAN . . . . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.1.  Provenance and Documents  . . . . . . . . . . . . . .   4
       2.1.2.  Characteristics . . . . . . . . . . . . . . . . . . .   4
     2.2.  Narrowband IoT (NB-IoT) . . . . . . . . . . . . . . . . .  10
       2.2.1.  Provenance and Documents  . . . . . . . . . . . . . .  10
       2.2.2.  Characteristics . . . . . . . . . . . . . . . . . . .  11
     2.3.  Sigfox  . . . . . . . . . . . . . . . . . . . . . . . . .  15
       2.3.1.  Provenance and Documents  . . . . . . . . . . . . . .  15
       2.3.2.  Characteristics . . . . . . . . . . . . . . . . . . .  16
     2.4.  Wi-SUN Alliance Field Area Network (FAN)  . . . . . . . .  20
       2.4.1.  Provenance and Documents  . . . . . . . . . . . . . .  20
       2.4.2.  Characteristics . . . . . . . . . . . . . . . . . . .  21
   3.  Generic Terminology . . . . . . . . . . . . . . . . . . . . .  24
   4.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .  26
     4.1.  Naive Application of IPv6 . . . . . . . . . . . . . . . .  26
     4.2.  6LoWPAN . . . . . . . . . . . . . . . . . . . . . . . . .  26
       4.2.1.  Header Compression  . . . . . . . . . . . . . . . . .  27
       4.2.2.  Address Autoconfiguration . . . . . . . . . . . . . .  27
       4.2.3.  Fragmentation . . . . . . . . . . . . . . . . . . . .  27
       4.2.4.  Neighbor Discovery  . . . . . . . . . . . . . . . . .  28
     4.3.  6lo . . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     4.4.  6tisch  . . . . . . . . . . . . . . . . . . . . . . . . .  29
     4.5.  RoHC  . . . . . . . . . . . . . . . . . . . . . . . . . .  29
     4.6.  ROLL  . . . . . . . . . . . . . . . . . . . . . . . . . .  30
     4.7.  CoAP  . . . . . . . . . . . . . . . . . . . . . . . . . .  30
     4.8.  Mobility  . . . . . . . . . . . . . . . . . . . . . . . .  31
     4.9.  DNS and LPWAN . . . . . . . . . . . . . . . . . . . . . .  31
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  31
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  32
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  39
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  40
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   This document provides background material and an overview of the
   technologies being considered in the IETF's IPv6 over Low Power Wide-
   Area Networks (LPWAN) Working Group (WG).  It also provides a gap
   analysis between the needs of these technologies and currently
   available IETF specifications.






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   Most technologies in this space aim for a similar goal of supporting
   large numbers of very low-cost, low-throughput devices with very low
   power consumption, so that even battery-powered devices can be
   deployed for years.  LPWAN devices also tend to be constrained in
   their use of bandwidth, for example, with limited frequencies being
   allowed to be used within limited duty cycles (usually expressed as a
   percentage of time per hour that the device is allowed to transmit).
   As the name implies, coverage of large areas is also a common goal.
   So, by and large, the different technologies aim for deployment in
   very similar circumstances.

   While all constrained networks must balance power consumption /
   battery life, cost, and bandwidth, LPWANs prioritize power and cost
   benefits by accepting severe bandwidth and duty cycle constraints
   when making the required trade-offs.  This prioritization is made in
   order to get the multiple-kilometer radio links implied by "Wide
   Area" in LPWAN's name.

   Existing pilot deployments have shown huge potential and created much
   industrial interest in these technologies.  At the time of writing,
   essentially no LPWAN end devices (other than for Wi-SUN) have IP
   capabilities.  Connecting LPWANs to the Internet would provide
   significant benefits to these networks in terms of interoperability,
   application deployment, and management (among others).  The goal of
   the LPWAN WG is to, where necessary, adapt IETF-defined protocols,
   addressing schemes, and naming conventions to this particular
   constrained environment.

   This document is largely the work of the people listed in the
   Contributors section.

2.  LPWAN Technologies

   This section provides an overview of the set of LPWAN technologies
   that are being considered in the LPWAN WG.  The text for each was
   mainly contributed by proponents of each technology.

   Note that this text is not intended to be normative in any sense; it
   simply exists to help the reader in finding the relevant Layer 2 (L2)
   specifications and in understanding how those integrate with IETF-
   defined technologies.  Similarly, there is no attempt here to set out
   the pros and cons of the relevant technologies.









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2.1.  LoRaWAN

2.1.1.  Provenance and Documents

   LoRaWAN is a wireless technology based on Industrial, Scientific, and
   Medical (ISM) that is used for long-range low-power low-data-rate
   applications developed by the LoRa Alliance, a membership consortium
   <https://www.lora-alliance.org/>.  This document is based on Version
   1.0.2 of the LoRa specification [LoRaSpec].  That specification is
   publicly available and has already seen several deployments across
   the globe.

2.1.2.  Characteristics

   LoRaWAN aims to support end devices operating on a single battery for
   an extended period of time (e.g., 10 years or more), extended
   coverage through 155 dB maximum coupling loss, and reliable and
   efficient file download (as needed for remote software/firmware
   upgrade).

   LoRaWAN networks are typically organized in a star-of-stars topology
   in which Gateways relay messages between end devices and a central
   "network server" in the backend.  Gateways are connected to the
   network server via IP links while end devices use single-hop LoRaWAN
   communication that can be received at one or more Gateways.
   Communication is generally bidirectional; uplink communication from
   end devices to the network server is favored in terms of overall
   bandwidth availability.

   Figure 1 shows the entities involved in a LoRaWAN network.

   +----------+
   |End Device| * * *
   +----------+       *   +---------+
                        * | Gateway +---+
   +----------+       *   +---------+   |   +---------+
   |End Device| * * *                   +---+ Network +--- Application
   +----------+       *                 |   | Server  |
                        * +---------+   |   +---------+
   +----------+       *   | Gateway +---+
   |End Device| * * *   * +---------+
   +----------+
       Key: *      LoRaWAN Radio
            +---+  IP connectivity

                      Figure 1: LoRaWAN Architecture





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   o  End Device: a LoRa client device, sometimes called a "mote".
      Communicates with Gateways.

   o  Gateway: a radio on the infrastructure side, sometimes called a
      "concentrator" or "base station".  Communicates with end devices
      and, via IP, with a network server.

   o  Network Server: The Network Server (NS) terminates the LoRaWAN
      Medium Access Control (MAC) layer for the end devices connected to
      the network.  It is the center of the star topology.

   o  Join Server: The Join Server (JS) is a server on the Internet side
      of an NS that processes join requests from an end devices.

   o  Uplink message: refers to communications from an end device to a
      network server or application via one or more Gateways.

   o  Downlink message: refers to communications from a network server
      or application via one Gateway to a single end device or a group
      of end devices (considering multicasting).

   o  Application: refers to application-layer code both on the end
      device and running "behind" the NS.  For LoRaWAN, there will
      generally only be one application running on most end devices.
      Interfaces between the NS and the application are not further
      described here.

   In LoRaWAN networks, end device transmissions may be received at
   multiple Gateways, so, during nominal operation, a network server may
   see multiple instances of the same uplink message from an end device.

   The LoRaWAN network infrastructure manages the data rate and Radio
   Frequency (RF) output power for each end device individually by means
   of an Adaptive Data Rate (ADR) scheme.  End devices may transmit on
   any channel allowed by local regulation at any time.

   LoRaWAN radios make use of ISM bands, for example, 433 MHz and 868
   MHz within the European Union and 915 MHz in the Americas.

   The end device changes channels in a pseudorandom fashion for every
   transmission to help make the system more robust to interference and/
   or to conform to local regulations.









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   Figure 2 shows that after a transmission slot, a Class A device turns
   on its receiver for two short receive windows that are offset from
   the end of the transmission window.  End devices can only transmit a
   subsequent uplink frame after the end of the associated receive
   windows.  When a device joins a LoRaWAN network, there are similar
   timeouts on parts of that process.

   |----------------------------|         |--------|     |--------|
   |             Tx             |         |   Rx   |     |   Rx   |
   |----------------------------|         |--------|     |--------|
                                |---------|
                                 Rx delay 1
                                |------------------------|
                                 Rx delay 2

        Figure 2: LoRaWAN Class A Transmission and Reception Window

   Given the different regional requirements, the detailed specification
   for the LoRaWAN Physical layer (PHY) (taking up more than 30 pages of
   the specification) is not reproduced here.  Instead, and mainly to
   illustrate the kinds of issue encountered, Table 1 presents some of
   the default settings for one ISM band (without fully explaining those
   here); Table 2 describes maxima and minima for some parameters of
   interest to those defining ways to use IETF protocols over the
   LoRaWAN MAC layer.

   +-----------------------+-------------------------------------------+
   |       Parameters      |               Default Value               |
   +-----------------------+-------------------------------------------+
   |       Rx delay 1      |                    1 s                    |
   |                       |                                           |
   |       Rx delay 2      |     2 s (must be RECEIVE_DELAY1 + 1 s)    |
   |                       |                                           |
   |      join delay 1     |                    5 s                    |
   |                       |                                           |
   |      join delay 2     |                    6 s                    |
   |                       |                                           |
   |     868MHz Default    |  3 (868.1,868.2,868.3), data rate: 0.3-50 |
   |        channels       |                   kbit/s                  |
   +-----------------------+-------------------------------------------+

               Table 1: Default Settings for EU 868 MHz Band









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   +------------------------------------------------+--------+---------+
   | Parameter/Notes                                |  Min   |   Max   |
   +------------------------------------------------+--------+---------+
   | Duty Cycle: some but not all ISM bands impose  |   1%   |    no   |
   | a limit in terms of how often an end device    |        |  limit  |
   | can transmit.  In some cases, LoRaWAN is more  |        |         |
   | restrictive in an attempt to avoid congestion. |        |         |
   |                                                |        |         |
   | EU 868 MHz band data rate/frame size           |  250   |  50000  |
   |                                                | bits/s |  bits/s |
   |                                                |  : 59  |  : 250  |
   |                                                | octets |  octets |
   |                                                |        |         |
   | US 915 MHz band data rate/frame size           |  980   |  21900  |
   |                                                | bits/s |  bits/s |
   |                                                |  : 19  |  : 250  |
   |                                                | octets |  octets |
   +------------------------------------------------+--------+---------+

         Table 2: Minima and Maxima for Various LoRaWAN Parameters

   Note that, in the case of the smallest frame size (19 octets), 8
   octets are required for LoRa MAC layer headers, leaving only 11
   octets for payload (including MAC layer options).  However, those
   settings do not apply for the join procedure -- end devices are
   required to use a channel and data rate that can send the 23-byte
   Join-Request message for the join procedure.

   Uplink and downlink higher-layer data is carried in a MACPayload.
   There is a concept of "ports" (an optional 8-bit value) to handle
   different applications on an end device.  Port zero is reserved for
   LoRaWAN-specific messaging, such as the configuration of the end
   device's network parameters (available channels, data rates, ADR
   parameters, Rx Delay 1 and 2, etc.).

   In addition to carrying higher-layer PDUs, there are Join-Request and
   Join-Response (aka Join-Accept) messages for handling network access.
   And so-called "MAC commands" (see below) up to 15 bytes long can be
   piggybacked in an options field ("FOpts").

   There are a number of MAC commands for link and device status
   checking, ADR and duty cycle negotiation, and managing the RX windows
   and radio channel settings.  For example, the link check response
   message allows the NS (in response to a request from an end device)
   to inform an end device about the signal attenuation seen most
   recently at a Gateway and to tell the end device how many Gateways
   received the corresponding link request MAC command.




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   Some MAC commands are initiated by the network server.  For example,
   one command allows the network server to ask an end device to reduce
   its duty cycle to only use a proportion of the maximum allowed in a
   region.  Another allows the network server to query the end device's
   power status with the response from the end device specifying whether
   it has an external power source or is battery powered (in which case,
   a relative battery level is also sent to the network server).

   In order to operate nominally on a LoRaWAN network, a device needs a
   32-bit device address, which is assigned when the device "joins" the
   network (see below for the join procedure) or that is pre-provisioned
   into the device.  In case of roaming devices, the device address is
   assigned based on the 24-bit network identifier (NetID) that is
   allocated to the network by the LoRa Alliance.  Non-roaming devices
   can be assigned device addresses by the network without relying on a
   NetID assigned by the LoRa Alliance.

   End devices are assumed to work with one or quite a limited number of
   applications, identified by a 64-bit AppEUI, which is assumed to be a
   registered IEEE EUI64 value [EUI64].  In addition, a device needs to
   have two symmetric session keys, one for protecting network artifacts
   (port=0), the NwkSKey, and another for protecting application-layer
   traffic, the AppSKey.  Both keys are used for 128-bit AES
   cryptographic operations.  So, one option is for an end device to
   have all of the above plus channel information, somehow
   (pre-)provisioned; in that case, the end device can simply start
   transmitting.  This is achievable in many cases via out-of-band means
   given the nature of LoRaWAN networks.  Table 3 summarizes these
   values.

   +---------+---------------------------------------------------------+
   | Value   | Description                                             |
   +---------+---------------------------------------------------------+
   | DevAddr | DevAddr (32 bits) =  device-specific network address    |
   |         | generated from the NetID                                |
   |         |                                                         |
   | AppEUI  | IEEE EUI64 value corresponding to the join server for   |
   |         | an application                                          |
   |         |                                                         |
   | NwkSKey | 128-bit network session key used with AES-CMAC          |
   |         |                                                         |
   | AppSKey | 128-bit application session key used with AES-CTR       |
   |         |                                                         |
   | AppKey  | 128-bit application session key used with AES-ECB       |
   +---------+---------------------------------------------------------+

              Table 3: Values Required for Nominal Operation




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   As an alternative, end devices can use the LoRaWAN join procedure
   with a join server behind the NS in order to set up some of these
   values and dynamically gain access to the network.  To use the join
   procedure, an end device must still know the AppEUI and a different
   (long-term) symmetric key that is bound to the AppEUI (this is the
   application key (AppKey), and it is distinct from the application
   session key (AppSKey)).  The AppKey is required to be specific to the
   device; that is, each end device should have a different AppKey
   value.  Finally, the end device also needs a long-term identifier for
   itself, which is syntactically also an EUI-64 and is known as the
   device EUI or DevEUI.  Table 4 summarizes these values.

     +---------+----------------------------------------------------+
     | Value   | Description                                        |
     +---------+----------------------------------------------------+
     | DevEUI  | IEEE EUI64 naming the device                       |
     |         |                                                    |
     | AppEUI  | IEEE EUI64 naming the application                  |
     |         |                                                    |
     | AppKey  | 128-bit long-term application key for use with AES |
     +---------+----------------------------------------------------+

                Table 4: Values Required for Join Procedure

   The join procedure involves a special exchange where the end device
   asserts the AppEUI and DevEUI (integrity protected with the long-term
   AppKey, but not encrypted) in a Join-Request uplink message.  This is
   then routed to the network server, which interacts with an entity
   that knows that AppKey to verify the Join-Request.  If all is going
   well, a Join-Accept downlink message is returned from the network
   server to the end device.  That message specifies the 24-bit NetID,
   32-bit DevAddr, and channel information and from which the AppSKey
   and NwkSKey can be derived based on knowledge of the AppKey.  This
   provides the end device with all the values listed in Table 3.

   All payloads are encrypted and have data integrity.  MAC commands,
   when sent as a payload (port zero), are therefore protected.
   However, MAC commands piggybacked as frame options ("FOpts") are sent
   in clear.  Any MAC commands sent as frame options and not only as
   payload, are visible to a passive attacker, but they are not
   malleable for an active attacker due to the use of the Message
   Integrity Check (MIC) described below.

   For LoRaWAN version 1.0.x, the NwkSKey session key is used to provide
   data integrity between the end device and the network server.  The
   AppSKey is used to provide data confidentiality between the end
   device and network server, or to the application "behind" the network
   server, depending on the implementation of the network.



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   All MAC-layer messages have an outer 32-bit MIC calculated using AES-
   CMAC with the input being the ciphertext payload and other headers
   and using the NwkSkey.  Payloads are encrypted using AES-128, with a
   counter-mode derived from [IEEE.802.15.4] using the AppSKey.
   Gateways are not expected to be provided with the AppSKey or NwkSKey,
   all of the infrastructure-side cryptography happens in (or "behind")
   the network server.  When session keys are derived from the AppKey as
   a result of the join procedure, the Join-Accept message payload is
   specially handled.

   The long-term AppKey is directly used to protect the Join-Accept
   message content, but the function used is not an AES-encrypt
   operation, but rather an AES-decrypt operation.  The justification is
   that this means that the end device only needs to implement the AES-
   encrypt operation.  (The counter-mode variant used for payload
   decryption means the end device doesn't need an AES-decrypt
   primitive.)

   The Join-Accept plaintext is always less than 16 bytes long, so
   Electronic Code Book (ECB) mode is used for protecting Join-Accept
   messages.  The Join-Accept message contains an AppNonce (a 24-bit
   value) that is recovered on the end device along with the other Join-
   Accept content (e.g., DevAddr) using the AES-encrypt operation.  Once
   the Join-Accept payload is available to the end device, the session
   keys are derived from the AppKey, AppNonce, and other values, again
   using an ECB mode AES-encrypt operation, with the plaintext input
   being a maximum of 16 octets.

2.2.  Narrowband IoT (NB-IoT)

2.2.1.  Provenance and Documents

   Narrowband Internet of Things (NB-IoT) has been developed and
   standardized by 3GPP.  The standardization of NB-IoT was finalized
   with 3GPP Release 13 in June 2016, and further enhancements for
   NB-IoT are specified in 3GPP Release 14 in 2017 (for example, in the
   form of multicast support).  Further features and improvements will
   be developed in the following releases, but NB-IoT has been ready to
   be deployed since 2016; it is rather simple to deploy, especially in
   the existing LTE networks with a software upgrade in the operator's
   base stations.  For more information of what has been specified for
   NB-IoT, 3GPP specification 36.300 [TGPP36300] provides an overview
   and overall description of the Evolved Universal Terrestrial Radio
   Access Network (E-UTRAN) radio interface protocol architecture, while
   specifications 36.321 [TGPP36321], 36.322 [TGPP36322], 36.323
   [TGPP36323], and 36.331 [TGPP36331] give more detailed descriptions





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   of MAC, Radio Link Control (RLC), Packet Data Convergence Protocol
   (PDCP), and Radio Resource Control (RRC) protocol layers,
   respectively.  Note that the description below assumes familiarity
   with numerous 3GPP terms.

   For a general overview of NB-IoT, see [nbiot-ov].

2.2.2.  Characteristics

   Specific targets for NB-IoT include: module cost that is Less than US
   $5, extended coverage of 164 dB maximum coupling loss, battery life
   of over 10 years, ~55000 devices per cell, and uplink reporting
   latency of less than 10 seconds.

   NB-IoT supports Half Duplex Frequency Division Duplex (FDD) operation
   mode with 60 kbit/s peak rate in uplink and 30 kbit/s peak rate in
   downlink, and a Maximum Transmission Unit (MTU) size of 1600 bytes,
   limited by PDCP layer (see Figure 4 for the protocol structure),
   which is the highest layer in the user plane, as explained later.
   Any packet size up to the said MTU size can be passed to the NB-IoT
   stack from higher layers, segmentation of the packet is performed in
   the RLC layer, which can segment the data to transmission blocks with
   a size as small as 16 bits.  As the name suggests, NB-IoT uses
   narrowbands with bandwidth of 180 kHz in both downlink and uplink.
   The multiple access scheme used in the downlink is Orthogonal
   Frequency-Division Multiplex (OFDMA) with 15 kHz sub-carrier spacing.
   In uplink, Sub-Carrier Frequency-Division Multiplex (SC-FDMA) single
   tone with either 15kHz or 3.75 kHz tone spacing is used, or
   optionally multi-tone SC-FDMA can be used with 15 kHz tone spacing.

   NB-IoT can be deployed in three ways.  In-band deployment means that
   the narrowband is deployed inside the LTE band and radio resources
   are flexibly shared between NB-IoT and normal LTE carrier.  In Guard-
   band deployment, the narrowband uses the unused resource blocks
   between two adjacent LTE carriers.  Standalone deployment is also
   supported, where the narrowband can be located alone in dedicated
   spectrum, which makes it possible, for example, to reframe a GSM
   carrier at 850/900 MHz for NB-IoT.  All three deployment modes are
   used in licensed frequency bands.  The maximum transmission power is
   either 20 or 23 dBm for uplink transmissions, while for downlink
   transmission the eNodeB may use higher transmission power, up to 46
   dBm depending on the deployment.

   A Maximum Coupling Loss (MCL) target for NB-IoT coverage enhancements
   defined by 3GPP is 164 dB.  With this MCL, the performance of NB-IoT
   in downlink varies between 200 bps and 2-3 kbit/s, depending on the
   deployment mode.  Stand-alone operation may achieve the highest data




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   rates, up to a few kbit/s, while in-band and guard-band operations
   may reach several hundreds of bps.  NB-IoT may even operate with an
   MCL higher than 170 dB with very low bit rates.

   For signaling optimization, two options are introduced in addition to
   the legacy LTE RRC connection setup; mandatory Data-over-NAS (Control
   Plane optimization, solution 2 in [TGPP23720]) and optional RRC
   Suspend/Resume (User Plane optimization, solution 18 in [TGPP23720]).
   In the control-plane optimization, the data is sent over Non-Access
   Stratum (NAS), directly to/from the Mobile Management Entity (MME)
   (see Figure 3 for the network architecture) in the core network to
   the User Equipment (UE) without interaction from the base station.
   This means there is no Access Stratum security or header compression
   provided by the PDCP layer in the eNodeB, as the Access Stratum is
   bypassed, and only limited RRC procedures.  Header compression based
   on Robust Header Compression (RoHC) may still optionally be provided
   and terminated in the MME.

   The RRC Suspend/Resume procedures reduce the signaling overhead
   required for UE state transition from RRC Idle to RRC Connected mode
   compared to a legacy LTE operation in order to have quicker user-
   plane transaction with the network and return to RRC Idle mode
   faster.

   In order to prolong device battery life, both Power-Saving Mode (PSM)
   and extended DRX (eDRX) are available to NB-IoT.  With eDRX, the RRC
   Connected mode DRX cycle is up to 10.24 seconds; in RRC Idle, the
   eDRX cycle can be up to 3 hours.  In PSM, the device is in a deep
   sleep state and only wakes up for uplink reporting.  After the
   reporting, there is a window (configured by the network) during which
   the device receiver is open for downlink connectivity or for
   periodical "keep-alive" signaling (PSM uses periodic TAU signaling
   with additional reception windows for downlink reachability).

   Since NB-IoT operates in a licensed spectrum, it has no channel
   access restrictions allowing up to a 100% duty cycle.

   3GPP access security is specified in [TGPP33203].













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   +--+
   |UE| \                 +------+      +------+
   +--+  \                | MME  |------| HSS  |
          \             / +------+      +------+
   +--+    \+--------+ /      |
   |UE| ----| eNodeB |-       |
   +--+    /+--------+ \      |
          /             \ +--------+
         /               \|        |    +------+     Service Packet
   +--+ /                 |  S-GW  |----| P-GW |---- Data Network (PDN)
   |UE|                   |        |    +------+     e.g., Internet
   +--+                   +--------+

                    Figure 3: 3GPP Network Architecture

   Figure 3 shows the 3GPP network architecture, which applies to
   NB-IoT.  The MME is responsible for handling the mobility of the UE.
   The MME tasks include tracking and paging UEs, session management,
   choosing the Serving Gateway for the UE during initial attachment and
   authenticating the user.  At the MME, the NAS signaling from the UE
   is terminated.

   The Serving Gateway (S-GW) routes and forwards the user data packets
   through the access network and acts as a mobility anchor for UEs
   during handover between base stations known as eNodeBs and also
   during handovers between NB-IoT and other 3GPP technologies.

   The Packet Data Network Gateway (P-GW) works as an interface between
   the 3GPP network and external networks.

   The Home Subscriber Server (HSS) contains user-related and
   subscription-related information.  It is a database that performs
   mobility management, session-establishment support, user
   authentication, and access authorization.

   E-UTRAN consists of components of a single type, eNodeB. eNodeB is a
   base station that controls the UEs in one or several cells.

   The 3GPP radio protocol architecture is illustrated in Figure 4.












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   +---------+                                       +---------+
   | NAS     |----|-----------------------------|----| NAS     |
   +---------+    |    +---------+---------+    |    +---------+
   | RRC     |----|----| RRC     | S1-AP   |----|----| S1-AP   |
   +---------+    |    +---------+---------+    |    +---------+
   | PDCP    |----|----| PDCP    | SCTP    |----|----| SCTP    |
   +---------+    |    +---------+---------+    |    +---------+
   | RLC     |----|----| RLC     | IP      |----|----| IP      |
   +---------+    |    +---------+---------+    |    +---------+
   | MAC     |----|----| MAC     | L2      |----|----| L2      |
   +---------+    |    +---------+---------+    |    +---------+
   | PHY     |----|----| PHY     | PHY     |----|----| PHY     |
   +---------+         +---------+---------+         +---------+
               LTE-Uu                         S1-MME
       UE                     eNodeB                     MME

     Figure 4: 3GPP Radio Protocol Architecture for the Control Plane

   The radio protocol architecture of NB-IoT (and LTE) is separated into
   the control plane and the user plane.  The control plane consists of
   protocols that control the radio-access bearers and the connection
   between the UE and the network.  The highest layer of control plane
   is called the Non-Access Stratum (NAS), which conveys the radio
   signaling between the UE and the Evolved Packet Core (EPC), passing
   transparently through the radio network.  The NAS is responsible for
   authentication, security control, mobility management, and bearer
   management.

   The Access Stratum (AS) is the functional layer below the NAS; in the
   control plane, it consists of the Radio Resource Control (RRC)
   protocol [TGPP36331], which handles connection establishment and
   release functions, broadcast of system information, radio-bearer
   establishment, reconfiguration, and release.  The RRC configures the
   user and control planes according to the network status.  There exist
   two RRC states, RRC_Idle or RRC_Connected, and the RRC entity
   controls the switching between these states.  In RRC_Idle, the
   network knows that the UE is present in the network, and the UE can
   be reached in case of an incoming call/downlink data.  In this state,
   the UE monitors paging, performs cell measurements and cell
   selection, and acquires system information.  Also, the UE can receive
   broadcast and multicast data, but it is not expected to transmit or
   receive unicast data.  In RRC_Connected state, the UE has a
   connection to the eNodeB, the network knows the UE location on the
   cell level, and the UE may receive and transmit unicast data.  An RRC
   connection is established when the UE is expected to be active in the
   network, to transmit or receive data.  The RRC connection is
   released, switching back to RRC_Idle, when there is no more traffic;
   this is in order to preserve UE battery life and radio resources.



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   However, as mentioned earlier, a new feature was introduced for
   NB-IoT that allows data to be transmitted from the MME directly to
   the UE and then transparently to the eNodeB, thus bypassing AS
   functions.

   The PDCP's [TGPP36323] main services in the control plane are
   transfer of control-plane data, ciphering, and integrity protection.

   The RLC protocol [TGPP36322] performs transfer of upper-layer PDUs
   and, optionally, error correction with Automatic Repeat reQuest
   (ARQ), concatenation, segmentation, and reassembly of RLC Service
   Data Units (SDUs), in-sequence delivery of upper-layer PDUs,
   duplicate detection, RLC SDU discarding, RLC-re-establishment, and
   protocol error detection and recovery.

   The MAC protocol [TGPP36321] provides mapping between logical
   channels and transport channels, multiplexing of MAC SDUs, scheduling
   information reporting, error correction with Hybrid ARQ (HARQ),
   priority handling, and transport format selection.

   The PHY [TGPP36201] provides data-transport services to higher
   layers.  These include error detection and indication to higher
   layers, Forward Error Correction (FEC) encoding, HARQ soft-combining,
   rate-matching, mapping of the transport channels onto physical
   channels, power-weighting and modulation of physical channels,
   frequency and time synchronization, and radio characteristics
   measurements.

   The user plane is responsible for transferring the user data through
   the Access Stratum.  It interfaces with IP and the highest layer of
   the user plane is the PDCP, which, in the user plane, performs header
   compression using RoHC, transfer of user-plane data between eNodeB
   and the UE, ciphering, and integrity protection.  Similar to the
   control plane, lower layers in the user plane include RLC, MAC, and
   the PHY performing the same tasks as they do in the control plane.

2.3.  Sigfox

2.3.1.  Provenance and Documents

   The Sigfox LPWAN is in line with the terminology and specifications
   being defined by ETSI [etsi_unb].  As of today, Sigfox's network has
   been fully deployed in 12 countries, with ongoing deployments in 26
   other countries, giving in total a geography of 2 million square
   kilometers, containing 512 million people.






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2.3.2.  Characteristics

   Sigfox LPWAN autonomous battery-operated devices send only a few
   bytes per day, week, or month, in principle, allowing them to remain
   on a single battery for up to 10-15 years.  Hence, the system is
   designed as to allow devices to last several years, sometimes even
   buried underground.

   Since the radio protocol is connectionless and optimized for uplink
   communications, the capacity of a Sigfox base station depends on the
   number of messages generated by devices, and not on the actual number
   of devices.  Likewise, the battery life of devices depends on the
   number of messages generated by the device.  Depending on the use
   case, devices can vary from sending less than one message per device
   per day to dozens of messages per device per day.

   The coverage of the cell depends on the link budget and on the type
   of deployment (urban, rural, etc.).  The radio interface is compliant
   with the following regulations:

      Spectrum allocation in the USA [fcc_ref]

      Spectrum allocation in Europe [etsi_ref1] [etsi_ref2]

      Spectrum allocation in Japan [arib_ref]

   The Sigfox radio interface is also compliant with the local
   regulations of the following countries: Australia, Brazil, Canada,
   Kenya, Lebanon, Mauritius, Mexico, New Zealand, Oman, Peru,
   Singapore, South Africa, South Korea, and Thailand.

   The radio interface is based on Ultra Narrow Band (UNB)
   communications, which allow an increased transmission range by
   spending a limited amount of energy at the device.  Moreover, UNB
   allows a large number of devices to coexist in a given cell without
   significantly increasing the spectrum interference.

   Both uplink and downlink are supported, although the system is
   optimized for uplink communications.  Due to spectrum optimizations,
   different uplink and downlink frames and time synchronization methods
   are needed.

   The main radio characteristics of the UNB uplink transmission are:

   o  Channelization mask: 100 Hz / 600 Hz (depending on the region)

   o  Uplink baud rate: 100 baud / 600 baud (depending on the region)




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   o  Modulation scheme: DBPSK

   o  Uplink transmission power: compliant with local regulation

   o  Link budget: 155 dB (or better)

   o  Central frequency accuracy: not relevant, provided there is no
      significant frequency drift within an uplink packet transmission

   For example, in Europe, the UNB uplink frequency band is limited to
   868.00 to 868.60 MHz, with a maximum output power of 25 mW and a duty
   cycle of 1%.

   The format of the uplink frame is the following:

   +--------+--------+--------+------------------+-------------+-----+
   |Preamble|  Frame | Dev ID |     Payload      |Msg Auth Code| FCS |
   |        |  Sync  |        |                  |             |     |
   +--------+--------+--------+------------------+-------------+-----+

                       Figure 5: Uplink Frame Format

   The uplink frame is composed of the following fields:

   o  Preamble: 19 bits

   o  Frame sync and header: 29 bits

   o  Device ID: 32 bits

   o  Payload: 0-96 bits

   o  Authentication: 16-40 bits

   o  Frame check sequence: 16 bits (Cyclic Redundancy Check (CRC))

   The main radio characteristics of the UNB downlink transmission are:

   o  Channelization mask: 1.5 kHz

   o  Downlink baud rate: 600 baud

   o  Modulation scheme: GFSK

   o  Downlink transmission power: 500 mW / 4W (depending on the region)

   o  Link budget: 153 dB (or better)




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   o  Central frequency accuracy: the center frequency of downlink
      transmission is set by the network according to the corresponding
      uplink transmission.

   For example, in Europe, the UNB downlink frequency band is limited to
   869.40 to 869.65 MHz, with a maximum output power of 500 mW with 10%
   duty cycle.

   The format of the downlink frame is the following:

   +------------+-----+---------+------------------+-------------+-----+
   |  Preamble  |Frame|   ECC   |     Payload      |Msg Auth Code| FCS |
   |            |Sync |         |                  |             |     |
   +------------+-----+---------+------------------+-------------+-----+

                      Figure 6: Downlink Frame Format

   The downlink frame is composed of the following fields:

   o  Preamble: 91 bits

   o  Frame sync and header: 13 bits

   o  Error Correcting Code (ECC): 32 bits

   o  Payload: 0-64 bits

   o  Authentication: 16 bits

   o  Frame check sequence: 8 bits (CRC)

   The radio interface is optimized for uplink transmissions, which are
   asynchronous.  Downlink communications are achieved by devices
   querying the network for available data.

   A device willing to receive downlink messages opens a fixed window
   for reception after sending an uplink transmission.  The delay and
   duration of this window have fixed values.  The network transmits the
   downlink message for a given device during the reception window, and
   the network also selects the BS for transmitting the corresponding
   downlink message.

   Uplink and downlink transmissions are unbalanced due to the
   regulatory constraints on ISM bands.  Under the strictest
   regulations, the system can allow a maximum of 140 uplink messages






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   and 4 downlink messages per device per day.  These restrictions can
   be slightly relaxed depending on system conditions and the specific
   regulatory domain of operation.

                +---+
                |DEV| *                    +------+
                +---+   *                  |  RA  |
                          *                +------+
                +---+       *                 |
                |DEV| * * *   *               |
                +---+       *   +----+        |
                              * | BS | \  +--------+
                +---+       *   +----+  \ |        |
        DA -----|DEV| * * *               |   SC   |----- NA
                +---+       *           / |        |
                              * +----+ /  +--------+
                +---+       *   | BS |/
                |DEV| * * *   * +----+
                +---+         *
                            *
                +---+     *
                |DEV| * *
                +---+

                   Figure 7: Sigfox Network Architecture

   Figure 7 depicts the different elements of the Sigfox network
   architecture.

   Sigfox has a "one-contract one-network" model allowing devices to
   connect in any country, without any need or notion of either roaming
   or handover.

   The architecture consists of a single cloud-based core network, which
   allows global connectivity with minimal impact on the end device and
   radio access network.  The core network elements are the Service
   Center (SC) and the Registration Authority (RA).  The SC is in charge
   of the data connectivity between the BS and the Internet, as well as
   the control and management of the BSs and End Points (EPs).  The RA
   is in charge of the EP network access authorization.

   The radio access network is comprised of several BSs connected
   directly to the SC.  Each BS performs complex L1/L2 functions,
   leaving some L2 and L3 functionalities to the SC.

   The Devices (DEVs) or EPs are the objects that communicate
   application data between local Device Applications (DAs) and Network
   Applications (NAs).



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   Devices (or EPs) can be static or nomadic, as they associate with the
   SC and they do not attach to any specific BS.  Hence, they can
   communicate with the SC through one or multiple BSs.

   Due to constraints in the complexity of the Device, it is assumed
   that Devices host only one or very few device applications, which
   most of the time communicate each to a single network application at
   a time.

   The radio protocol authenticates and ensures the integrity of each
   message.  This is achieved by using a unique device ID and an
   AES-128-based message authentication code, ensuring that the message
   has been generated and sent by the device with the ID claimed in the
   message.  Application data can be encrypted at the application level
   or not, depending on the criticality of the use case, to provide a
   balance between cost and effort versus risk.  AES-128 in counter mode
   is used for encryption.  Cryptographic keys are independent for each
   device.  These keys are associated with the device ID and separate
   integrity and confidentiality keys are pre-provisioned.  A
   confidentiality key is only provisioned if confidentiality is to be
   used.  At the time of writing, the algorithms and keying details for
   this are not published.

2.4.  Wi-SUN Alliance Field Area Network (FAN)

   Text here is via personal communication from Bob Heile
   (bheile@ieee.org) and was authored by Bob and Sum Chin Sean.  Paul
   Duffy (paduffy@cisco.com) also provided additional comments/input on
   this section.

2.4.1.  Provenance and Documents

   The Wi-SUN Alliance <https://www.wi-sun.org/> is an industry alliance
   for smart city, smart grid, smart utility, and a broad set of general
   IoT applications.  The Wi-SUN Alliance Field Area Network (FAN)
   profile is open-standards based (primarily on IETF and IEEE 802
   standards) and was developed to address applications like smart
   municipality/city infrastructure monitoring and management, Electric
   Vehicle (EV) infrastructure, Advanced Metering Infrastructure (AMI),
   Distribution Automation (DA), Supervisory Control and Data
   Acquisition (SCADA) protection/management, distributed generation
   monitoring and management, and many more IoT applications.
   Additionally, the Alliance has created a certification program to
   promote global multi-vendor interoperability.

   The FAN profile is specified within ANSI/TIA as an extension of work
   previously done on Smart Utility Networks [ANSI-4957-000].  Updates
   to those specifications intended to be published in 2017 will contain



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   details of the FAN profile.  A current snapshot of the work to
   produce that profile is presented in [wisun-pressie1] and
   [wisun-pressie2].

2.4.2.  Characteristics

   The FAN profile is an IPv6 wireless mesh network with support for
   enterprise-level security.  The frequency-hopping wireless mesh
   topology aims to offer superior network robustness, reliability due
   to high redundancy, good scalability due to the flexible mesh
   configuration, and good resilience to interference.  Very low power
   modes are in development permitting long-term battery operation of
   network nodes.

   The following list contains some overall characteristics of Wi-SUN
   that are relevant to LPWAN applications.

   o  Coverage: The range of Wi-SUN FAN is typically 2 - 3 km in line of
      sight, matching the needs of neighborhood area networks, campus
      area networks, or corporate area networks.  The range can also be
      extended via multi-hop networking.

   o  High-bandwidth, low-link latency: Wi-SUN supports relatively high
      bandwidth, i.e., up to 300 kbit/s [FANOV], enables remote update
      and upgrade of devices so that they can handle new applications,
      extending their working life.  Wi-SUN supports LPWAN IoT
      applications that require on-demand control by providing low link
      latency (0.02 s) and bidirectional communication.

   o  Low-power consumption: FAN devices draw less than 2 uA when
      resting and only 8 mA when listening.  Such devices can maintain a
      long lifetime, even if they are frequently listening.  For
      instance, suppose the device transmits data for 10 ms once every
      10 s; theoretically, a battery of 1000 mAh can last more than 10
      years.

   o  Scalability: Tens of millions of Wi-SUN FAN devices have been
      deployed in urban, suburban, and rural environments, including
      deployments with more than 1 million devices.

   A FAN contains one or more networks.  Within a network, nodes assume
   one of three operational roles.  First, each network contains a
   Border Router providing WAN connectivity to the network.  The Border
   Router maintains source-routing tables for all nodes within its
   network, provides node authentication and key management services,
   and disseminates network-wide information such as broadcast
   schedules.  Second, Router nodes, which provide upward and downward
   packet forwarding (within a network).  A Router also provides



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   services for relaying security and address management protocols.
   Finally, Leaf nodes provide minimum capabilities: discovering and
   joining a network, sending/receiving IPv6 packets, etc.  A low-power
   network may contain a mesh topology with Routers at the edges that
   construct a star topology with Leaf nodes.

   The FAN profile is based on various open standards developed by the
   IETF (including [RFC768], [RFC2460], [RFC4443], and [RFC6282]).
   Related IEEE 802 standards include [IEEE.802.15.4] and
   [IEEE.802.15.9].  For Low-Power and Lossy Networks (LLNs), see ANSI/
   TIA [ANSI-4957-210].

   The FAN profile specification provides an application-independent
   IPv6-based transport service.  There are two possible methods for
   establishing IPv6 packet routing: the Routing Protocol for Low-Power
   and Lossy Networks (RPL) at the Network layer is mandatory, and
   Multi-Hop Delivery Service (MHDS) is optional at the Data Link layer.
   Figure 8 provides an overview of the FAN network stack.

   The Transport service is based on UDP (defined in [RFC768]) or TCP
   (defined in [RFC793].

   The Network service is provided by IPv6 as defined in [RFC2460] with
   an IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN)
   adaptation as defined in [RFC4944] and [RFC6282].  ICMPv6, as defined
   in [RFC4443], is used for the control plane during information
   exchange.

   The Data Link service provides both control/management of the PHY and
   data transfer/management services to the Network layer.  These
   services are divided into MAC and Logical Link Control (LLC) sub-
   layers.  The LLC sub-layer provides a protocol dispatch service that
   supports 6LoWPAN and an optional MAC sub-layer mesh service.  The MAC
   sub-layer is constructed using data structures defined in
   [IEEE.802.15.4].  Multiple modes of frequency hopping are defined.
   The entire MAC payload is encapsulated in an [IEEE.802.15.9]
   Information Element to enable LLC protocol dispatch between upper-
   layer 6LoWPAN processing and MAC sub-layer mesh processing, etc.
   These areas will be expanded once [IEEE.802.15.12] is completed.

   The PHY service is derived from a subset of the SUN FSK specification
   in [IEEE.802.15.4].  The 2-FSK modulation schemes, with a channel-
   spacing range from 200 to 600 kHz, are defined to provide data rates
   from 50 to 300 kbit/s, with FEC as an optional feature.  Towards
   enabling ultra-low-power applications, the PHY layer design is also
   extendable to low-energy and critical infrastructure-monitoring
   networks.




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   +----------------------+--------------------------------------------+
   | Layer                | Description                                |
   +----------------------+--------------------------------------------+
   | IPv6 protocol suite  | TCP/UDP                                    |
   |                      |                                            |
   |                      | 6LoWPAN Adaptation + Header Compression    |
   |                      |                                            |
   |                      | DHCPv6 for IP address management           |
   |                      |                                            |
   |                      | Routing using RPL                          |
   |                      |                                            |
   |                      | ICMPv6                                     |
   |                      |                                            |
   |                      | Unicast and Multicast forwarding           |
   +----------------------+--------------------------------------------+
   | MAC based on         | Frequency hopping                          |
   | [IEEE.802.15.4e] +   |                                            |
   | IE extensions        | Discovery and Join                         |
   |                      |                                            |
   |                      | Protocol Dispatch ([IEEE.802.15.9])        |
   |                      |                                            |
   |                      | Several Frame Exchange patterns            |
   |                      |                                            |
   |                      | Optional Mesh Under routing                |
   |                      | ([ANSI-4957-210])                          |
   +----------------------+--------------------------------------------+
   | PHY based on         | Various data rates and regions             |
   | [IEEE.802.15.4g]     |                                            |
   +----------------------+--------------------------------------------+
   | Security             | [IEEE.802.1x]/EAP-TLS/PKI Authentication   |
   |                      | TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8         |
   |                      | required for EAP-TLS                       |
   |                      |                                            |
   |                      | 802.11i Group Key Management               |
   |                      |                                            |
   |                      | Frame security is implemented as AES-CCM*  |
   |                      | as specified in [IEEE.802.15.4]            |
   |                      |                                            |
   |                      | Optional [ETSI-TS-102-887-2] Node 2 Node   |
   |                      | Key Management                             |
   +----------------------+--------------------------------------------+

                      Figure 8: Wi-SUN Stack Overview








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   The FAN security supports Data Link layer network access control,
   mutual authentication, and establishment of a secure pairwise link
   between a FAN node and its Border Router, which is implemented with
   an adaptation of [IEEE.802.1x] and EAP-TLS as described in [RFC5216]
   using secure device identity as described in [IEEE.802.1AR].
   Certificate formats are based upon [RFC5280].  A secure group link
   between a Border Router and a set of FAN nodes is established using
   an adaptation of the [IEEE.802.11] Four-Way Handshake.  A set of four
   group keys are maintained within the network, one of which is the
   current transmit key.  Secure node-to-node links are supported
   between one-hop FAN neighbors using an adaptation of
   [ETSI-TS-102-887-2].  FAN nodes implement Frame Security as specified
   in [IEEE.802.15.4].

3.  Generic Terminology

   LPWAN technologies, such as those discussed above, have similar
   architectures but different terminology.  We can identify different
   types of entities in a typical LPWAN network:

   o  End devices are the devices or the "things" (e.g., sensors,
      actuators, etc.); they are named differently in each technology
      (End Device, User Equipment, or EP).  There can be a high density
      of end devices per Radio Gateway.

   o  The Radio Gateway, which is the EP of the constrained link.  It is
      known as: Gateway, Evolved Node B or base station.

   o  The Network Gateway or Router is the interconnection node between
      the Radio Gateway and the Internet.  It is known as the Network
      Server, Serving GW, or Service Center.

   o  LPWAN-AAA server, which controls user authentication.  It is known
      as the Join-Server, Home Subscriber Server, or Registration
      Authority.  (We use the term LPWAN-AAA server because we're not
      assuming that this entity speaks RADIUS or Diameter as many/most
      AAA servers do; but, equally, we don't want to rule that out, as
      the functionality will be similar.)

   o  At last we have the Application Server, known also as Packet Data
      Node Gateway or Network Application.










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 +---------------------------------------------------------------------+
 | Function/ |           |           |            |        |           |
 |Technology |  LoRaWAN  |   NB-IoT  |   Sigfox   | Wi-SUN |    IETF   |
 +-----------+-----------+-----------+------------+--------+-----------+
 |Sensor,    |           |           |            |        |           |
 |Actuator,  |    End    |    User   |     End    |  Leaf  |   Device  |
 |device,    |  Device   | Equipment |    Point   |  Node  |   (DEV)   |
 |object     |           |           |            |        |           |
 +-----------+-----------+-----------+------------+--------+-----------+
 |Transceiver|           |  Evolved  |    Base    | Router |   Radio   |
 |Antenna    |  Gateway  |  Node B   |   Station  |  Node  |  Gateway  |
 +-----------+-----------+-----------+------------+--------+-----------+
 |Server     |  Network  |  PDN GW/  |   Service  | Border |  Network  |
 |           |  Server   |   SCEF*   |   Center   | Router |  Gateway  |
 |           |           |           |            |        |   (NGW)   |
 +-----------+-----------+-----------+------------+--------+-----------+
 |Security   |   Join    |    Home   |Registration|Authent.|  LPWAN-   |
 |Server     |  Server   | Subscriber| Authority  | Server |   AAA     |
 |           |           |   Server  |            |        |  Server   |
 +-----------+-----------+-----------+------------+--------+-----------+
 |Application|Application|Application|  Network   |Appli-  |Application|
 |           |   Server  |  Server   | Application| cation |   (App)   |
 +---------------------------------------------------------------------+

 * SCEF = Service Capability Exposure Function

                 Figure 9: LPWAN Architecture Terminology

                                                 +------+
 ()    ()   ()         |                         |LPWAN-|
   ()  () () ()       / \         +---------+    | AAA  |
() () () () () ()    /   \========|    /\   |====|Server|  +-----------+
 ()  ()   ()        |             | <--|--> |    +------+  |APPLICATION|
()  ()  ()  ()     / \============|    v    |==============|    (App)  |
  ()  ()  ()      /   \           +---------+              +-----------+
 DEV         Radio Gateways           NGW

                       Figure 10: LPWAN Architecture

   In addition to the names of entities, LPWANs are also subject to
   possibly regional frequency-band regulations.  Those may include
   restrictions on the duty cycle, for example, requiring that hosts
   only transmit for a certain percentage of each hour.








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4.  Gap Analysis

   This section considers some of the gaps between current LPWAN
   technologies and the goals of the LPWAN WG.  Many of the generic
   considerations described in [RFC7452] will also apply in LPWANs, as
   end devices can also be considered to be a subclass of (so-called)
   "smart objects".  In addition, LPWAN device implementers will also
   need to consider the issues relating to firmware updates described in
   [RFC8240].

4.1.  Naive Application of IPv6

   IPv6 [RFC8200] has been designed to allocate addresses to all the
   nodes connected to the Internet.  Nevertheless, the header overhead
   of at least 40 bytes introduced by the protocol is incompatible with
   LPWAN constraints.  If IPv6 with no further optimization were used,
   several LPWAN frames could be needed just to carry the IP header.
   Another problem arises from IPv6 MTU requirements, which require the
   layer below to support at least 1280 byte packets [RFC2460].

   IPv6 has a configuration protocol: Neighbor Discovery Protocol (NDP)
   [RFC4861]).  For a node to learn network parameters, NDP generates
   regular traffic with a relatively large message size that does not
   fit LPWAN constraints.

   In some LPWAN technologies, L2 multicast is not supported.  In that
   case, if the network topology is a star, the solution and
   considerations from Section 3.2.5 of [RFC7668] may be applied.

   Other key protocols (such as DHCPv6 [RFC3315], IPsec [RFC4301] and
   TLS [RFC5246]) have similarly problematic properties in this context.
   Each protocol requires relatively frequent round-trips between the
   host and some other host on the network.  In the case of
   cryptographic protocols (such as IPsec and TLS), in addition to the
   round-trips required for secure session establishment, cryptographic
   operations can require padding and addition of authenticators that
   are problematic when considering LPWAN lower layers.  Note that mains
   powered Wi-SUN mesh router nodes will typically be more resource
   capable than the other LPWAN technologies discussed.  This can enable
   use of more "chatty" protocols for some aspects of Wi-SUN.

4.2.  6LoWPAN

   Several technologies that exhibit significant constraints in various
   dimensions have exploited the 6LoWPAN suite of specifications
   ([RFC4944], [RFC6282], and [RFC6775]) to support IPv6 [USES-6LO].
   However, the constraints of LPWANs, often more extreme than those
   typical of technologies that have (re-)used 6LoWPAN, constitute a



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   challenge for the 6LoWPAN suite in order to enable IPv6 over LPWAN.
   LPWANs are characterized by device constraints (in terms of
   processing capacity, memory, and energy availability), and
   especially, link constraints, such as:

   o  tiny L2 payload size (from ~10 to ~100 bytes),

   o  very low bit rate (from ~10 bit/s to ~100 kbit/s), and

   o  in some specific technologies, further message rate constraints
      (e.g., between ~0.1 message/minute and ~1 message/minute) due to
      regional regulations that limit the duty cycle.

4.2.1.  Header Compression

   6LoWPAN header compression reduces IPv6 (and UDP) header overhead by
   eliding header fields when they can be derived from the link layer
   and by assuming that some of the header fields will frequently carry
   expected values. 6LoWPAN provides both stateless and stateful header
   compression.  In the latter, all nodes of a 6LoWPAN are assumed to
   share compression context.  In the best case, the IPv6 header for
   link-local communication can be reduced to only 2 bytes.  For global
   communication, the IPv6 header may be compressed down to 3 bytes in
   the most extreme case.  However, in more practical situations, the
   smallest IPv6 header size may be 11 bytes (one address prefix
   compressed) or 19 bytes (both source and destination prefixes
   compressed).  These headers are large considering the link-layer
   payload size of LPWAN technologies, and in some cases, are even
   bigger than the LPWAN PDUs. 6LoWPAN was initially designed for
   [IEEE.802.15.4] networks with a frame size up to 127 bytes and a
   throughput of up to 250 kbit/s, which may or may not be duty cycled.

4.2.2.  Address Autoconfiguration

   Traditionally, Interface Identifiers (IIDs) have been derived from
   link-layer identifiers [RFC4944].  This allows optimizations such as
   header compression.  Nevertheless, recent guidance has given advice
   on the fact that, due to privacy concerns, 6LoWPAN devices should not
   be configured to embed their link-layer addresses in the IID by
   default.  [RFC8065] provides guidance on better methods for
   generating IIDs.

4.2.3.  Fragmentation

   As stated above, IPv6 requires the layer below to support an MTU of
   1280 bytes [RFC8200].  Therefore, given the low maximum payload size
   of LPWAN technologies, fragmentation is needed.




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   If a layer of an LPWAN technology supports fragmentation, proper
   analysis has to be carried out to decide whether the fragmentation
   functionality provided by the lower layer or fragmentation at the
   adaptation layer should be used.  Otherwise, fragmentation
   functionality shall be used at the adaptation layer.

   6LoWPAN defined a fragmentation mechanism and a fragmentation header
   to support the transmission of IPv6 packets over IEEE.802.15.4
   networks [RFC4944].  While the 6LoWPAN fragmentation header is
   appropriate for the 2003 version of [IEEE.802.15.4] (which has a
   frame payload size of 81-102 bytes), it is not suitable for several
   LPWAN technologies, many of which have a maximum payload size that is
   one order of magnitude below that of the 2003 version of
   [IEEE.802.15.4].  The overhead of the 6LoWPAN fragmentation header is
   high, considering the reduced payload size of LPWAN technologies, and
   the limited energy availability of the devices using such
   technologies.  Furthermore, its datagram offset field is expressed in
   increments of eight octets.  In some LPWAN technologies, the 6LoWPAN
   fragmentation header plus eight octets from the original datagram
   exceeds the available space in the layer two payload.  In addition,
   the MTU in the LPWAN networks could be variable, which implies a
   variable fragmentation solution.

4.2.4.  Neighbor Discovery

   6LoWPAN Neighbor Discovery [RFC6775] defines optimizations to IPv6 ND
   [RFC4861], in order to adapt functionality of the latter for networks
   of devices using [IEEE.802.15.4] or similar technologies.  The
   optimizations comprise host-initiated interactions to allow for
   sleeping hosts, replacement of multicast-based address resolution for
   hosts by an address registration mechanism, multihop extensions for
   prefix distribution and duplicate address detection (note that these
   are not needed in a star topology network), and support for 6LoWPAN
   header compression.

   6LoWPAN ND may be used in not so severely constrained LPWAN networks.
   The relative overhead incurred will depend on the LPWAN technology
   used (and on its configuration, if appropriate).  In certain LPWAN
   setups (with a maximum payload size above ~60 bytes and duty-cycle-
   free or equivalent operation), an RS/RA/NS/NA exchange may be
   completed in a few seconds, without incurring packet fragmentation.

   In other LPWANs (with a maximum payload size of ~10 bytes and a
   message rate of ~0.1 message/minute), the same exchange may take
   hours or even days, leading to severe fragmentation and consuming a
   significant amount of the available network resources.  6LoWPAN ND
   behavior may be tuned through the use of appropriate values for the
   default Router Lifetime, the Valid Lifetime in the PIOs, and the



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   Valid Lifetime in the 6LoWPAN Context Option (6CO), as well as the
   address Registration Lifetime.  However, for the latter LPWANs
   mentioned above, 6LoWPAN ND is not suitable.

4.3.  6lo

   The 6lo WG has been reusing and adapting 6LoWPAN to enable IPv6
   support over link-layer technologies such as Bluetooth Low Energy
   (BTLE), ITU-T G.9959 [G9959], Digital Enhanced Cordless
   Telecommunications (DECT) Ultra Low Energy (ULE), MS/TP-RS485, Near
   Field Communication (NFC) IEEE 802.11ah.  (See
   <https://datatracker.ietf.org/wg/6lo/> for details on the 6lo WG.)
   These technologies are similar in several aspects to [IEEE.802.15.4],
   which was the original 6LoWPAN target technology.

   6lo has mostly used the subset of 6LoWPAN techniques best suited for
   each lower-layer technology and has provided additional optimizations
   for technologies where the star topology is used, such as BTLE or
   DECT-ULE.

   The main constraint in these networks comes from the nature of the
   devices (constrained devices); whereas, in LPWANs, it is the network
   itself that imposes the most stringent constraints.

4.4.  6tisch

   The IPv6 over the TSCH mode of IEEE 802.15.4e (6tisch) solution is
   dedicated to mesh networks that operate using [IEEE.802.15.4e] MAC
   with a deterministic slotted channel.  Time-Slotted Channel Hopping
   (TSCH) can help to reduce collisions and to enable a better balance
   over the channels.  It improves the battery life by avoiding the idle
   listening time for the return channel.

   A key element of 6tisch is the use of synchronization to enable
   determinism.  TSCH and 6tisch may provide a standard scheduling
   function.  The LPWAN networks probably will not support
   synchronization like the one used in 6tisch.

4.5.  RoHC

   RoHC is a header compression mechanism [RFC3095] developed for
   multimedia flows in a point-to-point channel.  RoHC uses three levels
   of compression, each level having its own header format.  In the
   first level, RoHC sends 52 bytes of header; in the second level, the
   header could be from 34 to 15 bytes; and in the third level, header
   size could be from 7 to 2 bytes.  The level of compression is managed
   by a Sequence Number (SN), which varies in size from 2 bytes to 4
   bits in the minimal compression.  SN compression is done with an



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   algorithm called Window-Least Significant Bits (W-LSB).  This window
   has a 4-bit size representing 15 packets, so every 15 packets, RoHC
   needs to slide the window in order to receive the correct SN, and
   sliding the window implies a reduction of the level of compression.
   When packets are lost or errored, the decompressor loses context and
   drops packets until a bigger header is sent with more complete
   information.  To estimate the performance of RoHC, an average header
   size is used.  This average depends on the transmission conditions,
   but most of the time is between 3 and 4 bytes.

   RoHC has not been adapted specifically to the constrained hosts and
   networks of LPWANs: it does not take into account energy limitations
   nor the transmission rate.  Additionally, RoHC context is
   synchronized during transmission, which does not allow better
   compression.

4.6.  ROLL

   Most technologies considered by the LPWAN WG are based on a star
   topology, which eliminates the need for routing at that layer.
   Future work may address additional use cases that may require
   adaptation of existing routing protocols or the definition of new
   ones.  As of the time of writing, work similar to that done in the
   Routing Over Low-Power and Lossy Network (ROLL) WG and other routing
   protocols are out of scope of the LPWAN WG.

4.7.  CoAP

   The Constrained Application Protocol (CoAP) [RFC7252] provides a
   RESTful framework for applications intended to run on constrained IP
   networks.  It may be necessary to adapt CoAP or related protocols to
   take into account the extreme duty cycles and the potentially
   extremely limited throughput of LPWANs.

   For example, some of the timers in CoAP may need to be redefined.
   Taking into account CoAP acknowledgments may allow the reduction of
   L2 acknowledgments.  On the other hand, the current work in progress
   in the CoRE WG where the Constrained Management Interface (COMI) /
   Constrained Objects Language (CoOL) network management interface
   which, uses Structured Identifiers (SIDs) to reduce payload size over
   CoAP may prove to be a good solution for the LPWAN technologies.  The
   overhead is reduced by adding a dictionary that matches a URI to a
   small identifier and a compact mapping of the YANG data model into
   the Concise Binary Object Representation (CBOR).







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4.8.  Mobility

   LPWAN nodes can be mobile.  However, LPWAN mobility is different from
   the one specified for Mobile IP.  LPWAN implies sporadic traffic and
   will rarely be used for high-frequency, real-time communications.
   The applications do not generate a flow; they need to save energy
   and, most of the time, the node will be down.

   In addition, LPWAN mobility may mostly apply to groups of devices
   that represent a network; in which case, mobility is more a concern
   for the Gateway than the devices.  Network Mobility (NEMO) [RFC3963]
   or other mobile Gateway solutions (such as a Gateway with an LTE
   uplink) may be used in the case where some end devices belonging to
   the same network Gateway move from one point to another such that
   they are not aware of being mobile.

4.9.  DNS and LPWAN

   The Domain Name System (DNS) [RFC1035], enables applications to name
   things with a globally resolvable name.  Many protocols use the DNS
   to identify hosts, for example, applications using CoAP.

   The DNS query/answer protocol as a precursor to other communication
   within the Time-To-Live (TTL) of a DNS answer is clearly problematic
   in an LPWAN, say where only one round-trip per hour can be used, and
   with a TTL that is less than 3600 seconds.  It is currently unclear
   whether and how DNS-like functionality might be provided in LPWANs.

5.  Security Considerations

   Most LPWAN technologies integrate some authentication or encryption
   mechanisms that were defined outside the IETF.  The LPWAN WG may need
   to do work to integrate these mechanisms to unify management.  A
   standardized Authentication, Authorization, and Accounting (AAA)
   infrastructure [RFC2904] may offer a scalable solution for some of
   the security and management issues for LPWANs.  AAA offers
   centralized management that may be of use in LPWANs, for example
   [LoRaWAN-AUTH] and [LoRaWAN-RADIUS] suggest possible security
   processes for a LoRaWAN network.  Similar mechanisms may be useful to
   explore for other LPWAN technologies.

   Some applications using LPWANs may raise few or no privacy
   considerations.  For example, temperature sensors in a large office
   building may not raise privacy issues.  However, the same sensors, if
   deployed in a home environment, and especially if triggered due to
   human presence, can raise significant privacy issues: if an end
   device emits a (encrypted) packet every time someone enters a room in
   a home, then that traffic is privacy sensitive.  And the more that



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   the existence of that traffic is visible to network entities, the
   more privacy sensitivities arise.  At this point, it is not clear
   whether there are workable mitigations for problems like this.  In a
   more typical network, one would consider defining padding mechanisms
   and allowing for cover traffic.  In some LPWANs, those mechanisms may
   not be feasible.  Nonetheless, the privacy challenges do exist and
   can be real; therefore, some solutions will be needed.  Note that
   many aspects of solutions in this space may not be visible in IETF
   specifications but can be, e.g., implementation or deployment
   specific.

   Another challenge for LPWANs will be how to handle key management and
   associated protocols.  In a more traditional network (e.g., the Web),
   servers can "staple" Online Certificate Status Protocol (OCSP)
   responses in order to allow browsers to check revocation status for
   presented certificates [RFC6961].  While the stapling approach is
   likely something that would help in an LPWAN, as it avoids an RTT,
   certificates and OCSP responses are bulky items and will prove
   challenging to handle in LPWANs with bounded bandwidth.

6.  IANA Considerations

   This document has no IANA actions.

7.  Informative References

   [ANSI-4957-000]
              ANSI/TIA, "Architecture Overview for the Smart Utility
              Network", ANSI/TIA-4957.0000 , May 2013.

   [ANSI-4957-210]
              ANSI/TIA, "Multi-Hop Delivery Specification of a Data Link
              Sub-Layer", ANSI/TIA-4957.210 , May 2013.

   [arib_ref] ARIB, "920MHz-Band Telemeter, Telecontrol and Data
              Transmission Radio Equipment", ARIB STD-T108 Version 1.0,
              February 2012.

   [ETSI-TS-102-887-2]
              ETSI, "Electromagnetic compatibility and Radio spectrum
              Matters (ERM); Short Range Devices; Smart Metering
              Wireless Access Protocol; Part 2: Data Link Layer (MAC
              Sub-layer)", ETSI TS 102 887-2, Version V1.1.1, September
              2013.







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   [etsi_ref1]
              ETSI, "Short Range Devices (SRD) operating in the
              frequency range 25 MHz to 1 000 MHz; Part 1: Technical
              characteristics and methods of measurement", Draft ETSI
              EN 300-220-1, Version V3.1.0, May 2016.

   [etsi_ref2]
              ETSI, "Short Range Devices (SRD) operating in the
              frequency range 25 MHz to 1 000 MHz; Part 2: Harmonised
              Standard covering the essential requirements of article
              3.2 of Directive 2014/53/EU for non specific radio
              equipment", Final draft ETSI EN 300-220-2 P300-220-2,
              Version V3.1.1, November 2016.

   [etsi_unb] ETSI ERM, "System Reference document (SRdoc); Short Range
              Devices (SRD); Technical characteristics for Ultra Narrow
              Band (UNB) SRDs operating in the UHF spectrum below 1
              GHz", ETSI TR 103 435, Version V1.1.1, February 2017.

   [EUI64]    IEEE, "Guidelines for 64-bit Global Identifier
              (EUI),Organizationally Unique Identifier (OUI), and
              Company ID (CID)", August 2017,
              <http://standards.ieee.org/develop/regauth/tut/eui.pdf>.

   [FANOV]    IETF, "Wi-SUN Alliance Field Area Network (FAN) Overview",
              IETF 97, November 2016,
              <https://www.ietf.org/proceedings/97/slides/
              slides-97-lpwan-35-wi-sun-presentation-00.pdf>.

   [fcc_ref]  "Telecommunication Radio Frequency Devices - Operation
              within the bands 902-928 MHz, 2400-2483.5 MHz, and
              5725-5850 MHz.", FCC CFR 47 15.247, June 2016.

   [G9959]    ITU-T, "Short range narrow-band digital radiocommunication
              transceivers - PHY, MAC, SAR and LLC layer
              specifications", ITU-T Recommendation G.9959, January
              2015, <http://www.itu.int/rec/T-REC-G.9959>.

   [IEEE.802.11]
              IEEE, "IEEE Standard for Information technology--
              Telecommunications and information exchange between
              systems Local and metropolitan area networks--Specific
              requirements Part 11: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) Specifications",
              IEEE 802.11.






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   [IEEE.802.15.12]
              IEEE, "Upper Layer Interface (ULI) for IEEE 802.15.4 Low-
              Rate Wireless Networks", IEEE 802.15.12.

   [IEEE.802.15.4]
              IEEE, "IEEE Standard for Low-Rate Wireless Networks",
              IEEE 802.15.4, <https://standards.ieee.org/findstds/
              standard/802.15.4-2015.html>.

   [IEEE.802.15.4e]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Part 15.4: Low-Rate Wireless Personal Area
              Networks (LR-WPANs) Amendment 1: MAC sublayer",
              IEEE 802.15.4e.

   [IEEE.802.15.4g]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Part 15.4: Low-Rate Wireless Personal Area
              Networks (LR-WPANs) Amendment 3: Physical Layer (PHY)
              Specifications for Low-Data-Rate, Wireless, Smart Metering
              Utility Networks", IEEE 802.15.4g.

   [IEEE.802.15.9]
              IEEE, "IEEE Recommended Practice for Transport of Key
              Management Protocol (KMP) Datagrams", IEEE Standard
              802.15.9, 2016, <https://standards.ieee.org/findstds/
              standard/802.15.9-2016.html>.

   [IEEE.802.1AR]
              ANSI/IEEE, "IEEE Standard for Local and metropolitan area
              networks - Secure Device Identity", IEEE 802.1AR.

   [IEEE.802.1x]
              IEEE, "Port Based Network Access Control", IEEE 802.1x.

   [LoRaSpec] LoRa Alliance, "LoRaWAN Specification Version V1.0.2",
              July 2016, <https://lora-alliance.org/sites/default/
              files/2018-05/lorawan1_0_2-20161012_1398_1.pdf>.

   [LoRaWAN]  Farrell, S. and A. Yegin, "LoRaWAN Overview", Work in
              Progress, draft-farrell-lpwan-lora-overview-01, October
              2016.

   [LoRaWAN-AUTH]
              Garcia, D., Marin, R., Kandasamy, A., and A. Pelov,
              "LoRaWAN Authentication in Diameter", Work in Progress,
              draft-garcia-dime-diameter-lorawan-00, May 2016.




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   [LoRaWAN-RADIUS]
              Garcia, D., Lopez, R., Kandasamy, A., and A. Pelov,
              "LoRaWAN Authentication in RADIUS", Work in Progress,
              draft-garcia-radext-radius-lorawan-03, May 2017.

   [LPWAN-GAP]
              Minaburo, A., Ed., Gomez, C., Ed., Toutain, L., Paradells,
              J., and J. Crowcroft, "LPWAN Survey and GAP Analysis",
              Work in Progress, draft-minaburo-lpwan-gap-analysis-02,
              October 2016.

   [NB-IoT]   Ratilainen, A., "NB-IoT characteristics", Work in
              Progress, draft-ratilainen-lpwan-nb-iot-00, July 2016.

   [nbiot-ov] IEEE, "NB-IoT Technology Overview and Experience from
              Cloud-RAN Implementation", Volume 24, Issue 3 Pages 26-32,
              DOI 10.1109/MWC.2017.1600418, June 2017.

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <https://www.rfc-editor.org/info/rfc2460>.

   [RFC2904]  Vollbrecht, J., Calhoun, P., Farrell, S., Gommans, L.,
              Gross, G., de Bruijn, B., de Laat, C., Holdrege, M., and
              D. Spence, "AAA Authorization Framework", RFC 2904,
              DOI 10.17487/RFC2904, August 2000,
              <https://www.rfc-editor.org/info/rfc2904>.

   [RFC3095]  Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
              Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T., Le,
              K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
              Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
              Compression (ROHC): Framework and four profiles: RTP, UDP,
              ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095,
              July 2001, <https://www.rfc-editor.org/info/rfc3095>.




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   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <https://www.rfc-editor.org/info/rfc3315>.

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, DOI 10.17487/RFC3963, January 2005,
              <https://www.rfc-editor.org/info/rfc3963>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <https://www.rfc-editor.org/info/rfc4861>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <https://www.rfc-editor.org/info/rfc4944>.

   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
              Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
              March 2008, <https://www.rfc-editor.org/info/rfc5216>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.







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   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,
              <https://www.rfc-editor.org/info/rfc6282>.

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012,
              <https://www.rfc-editor.org/info/rfc6775>.

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              DOI 10.17487/RFC6961, June 2013,
              <https://www.rfc-editor.org/info/rfc6961>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/info/rfc7252>.

   [RFC7452]  Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
              "Architectural Considerations in Smart Object Networking",
              RFC 7452, DOI 10.17487/RFC7452, March 2015,
              <https://www.rfc-editor.org/info/rfc7452>.

   [RFC7668]  Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
              Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
              Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
              <https://www.rfc-editor.org/info/rfc7668>.

   [RFC8065]  Thaler, D., "Privacy Considerations for IPv6 Adaptation-
              Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065,
              February 2017, <https://www.rfc-editor.org/info/rfc8065>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [RFC8240]  Tschofenig, H. and S. Farrell, "Report from the Internet
              of Things Software Update (IoTSU) Workshop 2016",
              RFC 8240, DOI 10.17487/RFC8240, September 2017,
              <https://www.rfc-editor.org/info/rfc8240>.







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   [Sigfox]   Zuniga, J. and B. PONSARD, "Sigfox System Description",
              Work in Progress,
              draft-zuniga-lpwan-sigfox-system-description-04, December
              2017.

   [TGPP23720]
              3GPP, "Study on architecture enhancements for Cellular
              Internet of Things", 3GPP TS 23.720 13.0.0, 2016.

   [TGPP33203]
              3GPP, "3G security; Access security for IP-based
              services", 3GPP TS 23.203 13.1.0, 2016.

   [TGPP36201]
              3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); LTE physical layer; General description", 3GPP
              TS 36.201 13.2.0, 2016.

   [TGPP36300]
              3GPP, "Evolved Universal Terrestrial Radio Access (E-UTRA)
              and Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN); Overall description; Stage 2", 3GPP TS 36.300
              13.4.0, 2016,
              <http://www.3gpp.org/ftp/Specs/2016-09/Rel-14/36_series/>.

   [TGPP36321]
              3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Medium Access Control (MAC) protocol
              specification", 3GPP TS 36.321 13.2.0, 2016.

   [TGPP36322]
              3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Radio Link Control (RLC) protocol
              specification", 3GPP TS 36.322 13.2.0, 2016.

   [TGPP36323]
              3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Packet Data Convergence Protocol (PDCP)
              specification (Not yet available)", 3GPP TS 36.323 13.2.0,
              2016.

   [TGPP36331]
              3GPP, "Evolved Universal Terrestrial Radio Access
              (E-UTRA); Radio Resource Control (RRC); Protocol
              specification", 3GPP TS 36.331 13.2.0, 2016.






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   [USES-6LO] Hong, Y., Gomez, C., Choi, Y-H., and D-Y. Ko, "IPv6 over
              Constrained Node Networks(6lo) Applicability & Use cases",
              Work in Progress, draft-hong-6lo-use-cases-03, October
              2016.

   [wisun-pressie1]
              Beecher, P., "Wi-SUN Alliance", March 2017,
              <http://indiasmartgrid.org/event2017/10-03-2017/4.%20Round
              table%20on%20Communication%20and%20Cyber%20Security/1.%20P
              hil%20Beecher.pdf>.

   [wisun-pressie2]
              Heile, B., "Wi-SUN Alliance Field Area Network
              (FAN)Overview", As presented at IETF 97, November 2016,
              <https://www.ietf.org/proceedings/97/slides/
              slides-97-lpwan-35-wi-sun-presentation-00.pdf>.

Acknowledgments

   Thanks to all those listed in the Contributors section for the
   excellent text.  Errors in the handling of that are solely the
   editor's fault.

   In addition to those in the Contributors section, thanks are due to
   (in alphabetical order) the following for comments:

   Abdussalam Baryun
   Andy Malis
   Arun (arun@acklio.com)
   Behcet SariKaya
   Dan Garcia Carrillo
   Jiazi Yi
   Mirja Kuhlewind
   Paul Duffy
   Russ Housley
   Samita Chakrabarti
   Thad Guidry
   Warren Kumari

   Alexander Pelov and Pascal Thubert were the LPWAN WG Chairs while
   this document was developed.

   Stephen Farrell's work on this memo was supported by Pervasive
   Nation, the Science Foundation Ireland's CONNECT centre national IoT
   network <https://connectcentre.ie/pervasive-nation/>.






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Contributors

   As stated above, this document is mainly a collection of content
   developed by the full set of contributors listed below.  The main
   input documents and their authors were:

   o  Text for Section 2.1 was provided by Alper Yegin and Stephen
      Farrell in [LoRaWAN].

   o  Text for Section 2.2 was provided by Antti Ratilainen in [NB-IoT].

   o  Text for Section 2.3 was provided by Juan Carlos Zuniga and Benoit
      Ponsard in [Sigfox].

   o  Text for Section 2.4 was provided via personal communication from
      Bob Heile and was authored by Bob and Sum Chin Sean.  There is no
      Internet-Draft for that at the time of writing.

   o  Text for Section 4 was provided by Ana Minabiru, Carles Gomez,
      Laurent Toutain, Josep Paradells, and Jon Crowcroft in
      [LPWAN-GAP].  Additional text from that document is also used
      elsewhere above.

   The full list of contributors is as follows:

      Jon Crowcroft
      University of Cambridge
      JJ Thomson Avenue
      Cambridge, CB3 0FD
      United Kingdom

      Email: jon.crowcroft@cl.cam.ac.uk


      Carles Gomez
      UPC/i2CAT
      C/Esteve Terradas, 7
      Castelldefels 08860
      Spain

      Email: carlesgo@entel.upc.edu










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      Bob Heile
      Wi-Sun Alliance
      11 Robert Toner Blvd, Suite 5-301
      North Attleboro, MA  02763
      United States of America

      Phone: +1-781-929-4832
      Email: bheile@ieee.org


      Ana Minaburo
      Acklio
      2bis rue de la Chataigneraie
      35510 Cesson-Sevigne Cedex
      France

      Email: ana@ackl.io


      Josep PAradells
      UPC/i2CAT
      C/Jordi Girona, 1-3
      Barcelona 08034
      Spain

      Email: josep.paradells@entel.upc.edu


      Charles E. Perkins
      Futurewei
      2330 Central Expressway
      Santa Clara, CA 95050
      United States of America

      Email: charliep@computer.org


      Benoit Ponsard
      Sigfox
      425 rue Jean Rostand
      Labege  31670
      France

      Email: Benoit.Ponsard@sigfox.com
      URI:   http://www.sigfox.com/






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      Antti Ratilainen
      Ericsson
      Hirsalantie 11
      Jorvas  02420
      Finland

      Email: antti.ratilainen@ericsson.com


      Chin-Sean SUM
      Wi-Sun Alliance
      20, Science Park Rd 117674
      Singapore

      Phone: +65 6771 1011
      Email: sum@wi-sun.org


      Laurent Toutain
      Institut MINES TELECOM ; TELECOM Bretagne
      2 rue de la Chataigneraie
      CS 17607
      35576 Cesson-Sevigne Cedex
      France

      Email: Laurent.Toutain@telecom-bretagne.eu


      Alper Yegin
      Actility
      Paris
      France

      Email: alper.yegin@actility.com


      Juan Carlos Zuniga
      Sigfox
      425 rue Jean Rostand
      Labege  31670
      France

      Email: JuanCarlos.Zuniga@sigfox.com
      URI:   http://www.sigfox.com/







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Author's Address

   Stephen Farrell (editor)
   Trinity College Dublin
   Dublin  2
   Ireland

   Phone: +353-1-896-2354
   Email: stephen.farrell@cs.tcd.ie










































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