Bluetooth mesh networking explained

Bluetooth mesh networking
Developer:	Bluetooth SIG
Industry:	Lighting, IoT
Range:	100-1000 meters (depending on mesh relaying configuration)

Bluetooth Mesh is a computer mesh networking standard based on Bluetooth Low Energy that allows for many-to-many communication over Bluetooth radio. The Bluetooth Mesh specifications were defined in the Mesh Profile^[1] and Mesh Model^[2] specifications by the Bluetooth Special Interest Group (Bluetooth SIG). Bluetooth Mesh was conceived in 2014^[3] and adopted on .^[4]

Overview

Bluetooth Mesh is a mesh networking standard that operates on a flood network principle. It's based on the nodes relaying the messages: every relay node that receives a network packet that

• authenticates against a known network key
• is not in message cache
• has a TTL ≥ 2

can be retransmitted with TTL = TTL - 1. Message caching is used to prevent relaying recently seen messages.

Communication is carried in the messages that may be up to 384 bytes long, when using Segmentation and Reassembly (SAR) mechanism, but most of the messages fit in one segment, that is 11 bytes. Each message starts with an opcode, which may be a single byte (for special messages), 2 bytes (for standard messages), or 3 bytes (for vendor-specific messages).

Every message has a source and a destination address, determining which devices process messages. Devices publish messages to destinations which can be single things / groups of things / everything.

Each message has a sequence number that protects the network against replay attacks.

Each message is encrypted and authenticated. Two keys are used to secure messages: (1) network keys – allocated to a single mesh network, (2) application keys – specific for a given application functionality, e.g. turning the light on vs reconfiguring the light.

Messages have a time to live (TTL). Each time message is received and retransmitted, TTL is decremented which limits the number of "hops", eliminating endless loops.

Architecture

Bluetooth Mesh has a layered architecture, with multiple layers as below.

Layer	Functionality
Model Layer	It defines a standard way to exchange application specific messages. For example, a Light Lightness Model defines an interoperable way to control lightness. There are mandatory models, called Foundation Models, defining states and messages needed to manage a mesh network.
Access Layer	It defines mechanism to ensure that data is transmitted and received in the right context of a model and its associated application keys.
Upper Transport Layer	It defines authenticated encryption of access layer packets using an application (or device specific key). It also defines some control messages to manage Friendship or to notify the behavior of node using Heartbeat messages.
Lower Transport Layer	This layer defines a reliable (through a Block Acknowledgement) Segmented transmission upper layer packets, when a complete upper layer packet can't be carried in a single network layer packet. It also defines a mechanism to reassemble segments on the receiver.
Network Layer	This layer defines how transport packets are addressed over network to one or more nodes. It defines relay functionality for forwarding messages by a relay node to extended the range. It handles the network layer authenticated encryption using network key.
Bearer Layer	It defines how the network packets are exchanged between nodes. Mesh Profile Specification defines BLE advert bearer and BLE GATT bearer. Mesh Profile defines Proxy Protocol, through which mesh packets can be exchanged via other bearers like TCP/IP.

Types of nodes

Nodes that support the various features can be formed into a particular mesh network topology.

Feature	Functionality
Relay	receive and retransmit mesh messages over the advertising bearerto enable larger networks.
Proxy	receive and retransmit mesh messages between GATT andadvertising bearers.
Low Power	operate within a mesh network at significantly reduced receiverduty cycles only in conjunction with a node supporting the Friend feature.
Friend	help a node supporting the Low Power feature to operate by storingmessages destined for those nodes.

Theoretical limits

The practical limits of Bluetooth Mesh technology are unknown. Some limits that are built into the specification include:

Limit for a network	Value	Remarks
Maximum number of nodes	32 767	The limit is 32768 addresses and while a node may occupy more than one address, the practical limit is most likely lower.
Maximum number of groups	16 384Number of virtual groups is 2^128.
Maximum number of scenes	65 535
Maximum number of subnets	4 096
Maximum TTL	127

Mesh models

As of version 1.0 of Bluetooth Mesh specification, the following standard models and model groups have been defined:

Foundation models

Foundation models have been defined in the core specification. Two of them are mandatory for all mesh nodes.

• Configuration Server (mandatory)
• Configuration Client
• Health Server (mandatory)
• Health Client

Generic models

• Generic OnOff Server, used to represent devices that do not fit any of the model descriptions defined but support the generic properties of On/Off
• Generic Level Server, keeping the state of an element in a 16-bit signed integer
• Generic Default Transition Time Server, used to represent a default transition time for a variety of devices
• Generic Power OnOff Server & Generic Power OnOff Setup Server, used to represent devices that do not fit any of the model descriptions but support the generic properties of On/Off
• Generic Power Level Server & Generic Power Level Setup Server, including a Generic Power Actual state, a Generic Power Last state, a Generic Power Default state and a Generic Power Range state
• Generic Battery Server, representing a set of four values representing the state of a battery
• Generic Location Server & Generic Location Setup Server, representing location information of an element, either global (Lat/Lon) or local
• Generic User/Admin/Manufacturer/Client Property Server, representing any value to be stored by an element
• Generic OnOff Client & Generic Level Client
• Generic Default Transition Time Client
• Generic Power OnOff Client & Generic Power Level Client
• Generic Battery Client
• Generic Location Client
• Generic Property Client

Sensors

• Sensor Server & Sensor Setup Server, representing a sensor device. Sensor device may be configured to return a measured value periodically or on request; measurement period (cadence) may be configured to be fixed or to change, so that more important value range is being reported faster.
• Sensor Client

Time and scenes

• Time Server & Time Setup Server, allowing for time synchronization in mesh network
• Scene Server & Scene Setup Server, allowing for up to 65535 scenes to be configured and recalled when needed.
• Scheduler Server & Scheduler Setup Server
• Time Client, Scene Client & Scheduler Client

Lighting

• Light Lightness Server & Light Lightness Setup Server, representing a dimmable light source
• Light CTL Server, Light CTL Temperature Server & Light CTL Setup Server, representing a CCT or "tunable white" light source
• Light HSL Server, Light HSL Hue Server, Light HSL Saturation Server & Light HSL Setup Server, representing a light source based on Hue, Saturation, Lightness color representation
• Light xyL Server & Light xyL Setup Server, representing a light source based on modified CIE xyY color space.
• Light LC (Lightness Control) Server & Light LC Setup Server, representing a light control device, able to control Light Lightness model using an occupancy sensor and ambient light sensor. It may be used for light control scenarios like Auto-On, Auto-Off and/or Daylight Harvesting.
• Light Lightness Client, Light CTL Client, Light HSL Client, Light xyL Client & Light LC Client

Provisioning

Provisioning is a process of installing the device into a network. It is a mandatory step to build a Bluetooth Mesh network.

In the provisioning process, a provisioner securely distributes a network key and a unique address space for a device. The provisioning protocol uses P256 Elliptic Curve Diffie-Hellman Key Exchange to create a temporary key to encrypt network key and other information. This provides security from a passive eavesdropper. It also provides various authentication mechanisms to protect network information, from an active eavesdropper who uses man-in-the-middle attack, during provisioning process.

A key unique to a device known as "Device Key" is derived from elliptic curve shared secret on provisioner and device during the provisioning process. This device key is used by the provisioner to encrypt messages for that specific device.

The security of the provisioning process has been analyzed in a paper presented during the IEEE CNS 2018 conference.^[5]

The provisioning can be performed using a Bluetooth GATT connection or advertising using the specific bearer.

Terminology used in the Bluetooth Mesh Model and Mesh Profile specifications

• Destination: The address to which a message is sent.
• Element: An addressable entity within a device.
• Model: Standardized operation of typical user scenarios.
• Node: A provisioned device.
• Provisioner: A node that can add a device to a mesh network.
• Relay: A node able to retransmit messages.
• Source: The address from which a message is sent.

Implementations

Approved ("qualified") by Bluetooth SIG

Bluetooth mesh implementations approved ("qualified") by Bluetooth SIG!Name!Submitter!Qualification date!QDID!Type

Bluetooth Stack for Embedded Systems - MESH profile^[6]	Silvair, Inc.		98880	Profile Subsystem
Qualcomm Bluetooth Mesh^[7]	Qualcomm Technologies International, Ltd.		98856	Profile Subsystem
Silvair Mesh Models^[8]	Silvair, Inc.		99282	Profile Subsystem
Wireless Gecko Mesh Profile^[9]	Silicon Laboratories		101318	Profile Subsystem
CYW-MESH 1.0^[10]	Cypress Semiconductor Corporation		101726	Component (Tested)
Qualcomm Bluetooth Mesh Model^[11]	Qualcomm Technologies International, Ltd.		102243	Profile Subsystem
EtherMind Bluetooth Protocol Stack, 5.0 (Single Mode) + Mesh^[12]	Mindtree Limited		106544	Component (Tested)
Telink SIG Mesh SDK^[13]	Telink Semiconductor		106546	Profile Subsystem
TOSHIBA Bluetooth_stack_mesh-1^[14]	Toshiba Corporation		104143	Component (Tested)
AMICCOM Mesh Profile^[15]	AMICCOM Electronics Corporation		109370	Profile Subsystem
Amiccom Bluetooth Mesh Model^[16]	AMICCOM Electronics Corporation		110168	Profile Subsystem
Airoha SIG mesh^[17]	Airoha Technology Corp.		110202	Profile Subsystem
Marvell Mesh stack v1.0^[18]	Marvell Technology Group		110569	Component (Tested)
nRF5 SDK for Mesh ^[19]	Nordic Semiconductor	May 2, 2018	111537	Profile Subsystem
Realtek Bluetooth 5 Mesh Solution^[20]	Realsil Microelectronics Inc		115668	Profile Subsystem
STSW-BNRG-Mesh^[21]	STMicroelectronics		116029	Profile Subsystem
RDA BT Host 5.0^[22]	RDA Microelectronics, Inc.		115860	Profile Subsystem
JYMC-MESH-1^[23]	Shanghai Frequen Microelectronics Co., Ltd.		119229	End Product
RW-BLE-MESH^[24]	CEVA, Inc.		119268	Component (Tested)
ARM Ltd Cordio Mesh^[25]	ARM Ltd		116593	Profile Subsystem
Samsung SLSI Bluetooth Mesh^[26]	Samsung Electronics Co., Ltd.		122442	Profile Subsystem
Bluelet Host Stack V12^[27]	Barrot Technology Limited		123056	Component (Tested)
ESP BLE Mesh v0.6^[28]	Espressif Systems (Shanghai) Pte. Ltd.		124137	Profile Subsystem
BK3435 BLE Core Spec 5.0 with MESH^[29]	Beken Corp		127926	End Product
Actions Mesh Profile Subsystem^[30]	Actions (Zhuhai) Technology Co., Limited		127646	Profile Subsystem
AliOS Things BLE host and mesh profile v2.1.0^[31]	Alibaba (China) Co., Ltd.		129750	Host Subsystem
Tonly SIG Mesh Stack^[32]	Shenzhen Tonli Science and Technology Development Co., Ltd		130160	Profile Subsystem
Sino Wealth IBLE SIG Mesh Profile^[33]	Sino Wealth Electronic Ltd.		133403	Profile Subsystem
Qualcomm Bluetooth Mesh and Mesh Model v4.0^[34]	Qualcomm Technologies International, Ltd.		128410	Profile Subsystem
PAN1020 Mesh Profile subsystem^[35]	Shanghai Panchip Microelectronics Co., Ltd		129291	Profile Subsystem
Apache NimBLE BLE Host including BLE Mesh^[36]	JUUL Labs, Inc.		131934	Component (Tested)
Tmall mesh Stack^[37]	Alibaba (China) Co., Ltd.		128246	Profile Subsystem
ClarinoxBlue^[38]	Clarinox Technologies Pty Ltd		134454	Host Subsystem
BlueX Mesh^[39]	BlueX Microelectronics Corp Ltd.		137436	Profile Subsystem
Zephyr OS Mesh^[40]	The Linux Foundation		139259	Profile Subsystem
WCH Bluetooth Mesh^[41]	Nanjing Qinheng Microelectronics Co., Ltd.		144808	Profile Subsystem

Free and open-source software implementations

Free software and open source software implementations include the following:

• The official (included in Linux kernel by Linus Torvalds in 2001^[42]) Linux Bluetooth protocol stack BlueZ, dual free-licensed under the GPL and the LGPL, supports Mesh Profile, from release version 5.47,^[43] by providing meshctl tool (deprecated) to configure mesh devices. Release version 5.53 introduced mesh-cfgclient tool for configuring mesh networks. BlueZ was approved as a "qualified" software package by Bluetooth SIG in 2005. BlueZ is not considered to be a qualified Bluetooth Mesh stack as Bluetooth Mesh is not listed in aforementioned qualification record as a supported profile.
• Apache Mynewt NimBLE, free-licensed under the Apache License 2.0, supports Bluetooth Mesh from release version 1.2.0.^[44] It was qualified on with QDID 131934.
• Zephyr OS Mesh, free-licensed under the Apache License 2.0, supports Bluetooth Mesh from release version 1.9.0.^[45] Zephyr OS Mesh 1.14.x was qualified on with QDID 139259.

See also

• Cabir (computer worm)
• BlackArch
• Bluejacking
• Bluebugging
• Bluesnarfing
• AirDrop

Notes and References

1. Web site: Mesh Profile Bluetooth® Specification. 2017-07-13. Bluetooth Technology Website. PDF download. 2017-07-18.
2. Web site: Mesh Model Bluetooth® Specification. 2017-07-13. Bluetooth Technology Website. PDF download. 2017-07-18.
3. Web site: Range Limitation? What Range Limitation? Introducing Mesh Networks Bluetooth Technology Website. blog.bluetooth.com. dead. https://web.archive.org/web/20160409092727/http://blog.bluetooth.com/range-limitation-what-range-limitation-introducing-mesh-networks/. 2016-04-09. 2017-07-06.
4. Web site: Low Energy: Mesh Bluetooth Technology Website. www.bluetooth.com. dead. https://web.archive.org/web/20170901202951/https://www.bluetooth.com/what-is-bluetooth-technology/how-it-works/le-mesh. 2017-09-01. 2017-07-18.
5. Book: Adomnicai. A.. Fournier. J. J. A.. Masson. L.. 2018 IEEE Conference on Communications and Network Security (CNS) . Hardware Security Threats Against Bluetooth Mesh Networks . 2018-05-30. 1–9. https://ieeexplore.ieee.org/document/8433184. 10.1109/CNS.2018.8433184. 978-1-5386-4586-4. 52004479 .
6. Web site: QD ID 98880 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
7. Web site: QD ID 98856 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
8. Web site: QD ID 99282 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
9. Web site: QD ID 101318 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
10. Web site: QD ID 101726 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
11. Web site: QD ID 102243 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2017-11-15.
12. Web site: QD ID 106544 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-03-05.
13. Web site: QD ID 106546 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-03-05.
14. Web site: QD ID 104143 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-03-05.
15. Web site: QD ID 109370 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-04-05.
16. Web site: QD ID 110168 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-04-05.
17. Web site: QD ID 110202 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-04-05.
18. Web site: QD ID 110569 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-05-03.
19. Web site: nRF5 SDK for Mesh / Bluetooth Low Energy / Products / Home - Ultra Low Power Wireless Solutions from NORDIC SEMICONDUCTOR. Systems. eZ. www.nordicsemi.com. en-GB. 2018-05-03.
20. Web site: QD ID 115668 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-09-15.
21. Web site: QD ID 116029 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-09-15.
22. Web site: QD ID 115860 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-09-15.
23. Web site: QD ID 119229 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-11-07.
24. Web site: QD ID 119268 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-11-07.
25. Web site: QD ID 116593 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-12-21.
26. Web site: QD ID 122442 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-12-21.
27. Web site: QD ID 123056 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2018-12-21.
28. Web site: QD ID 124137 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-01-24.
29. Web site: QD ID 127926 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-04-14.
30. Web site: QD ID 127646 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-04-14.
31. Web site: QD ID 129750 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-05-06.
32. Web site: QD ID 130160 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-05-06.
33. Web site: QD ID 133403 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-06-19.
34. Web site: QD ID 128410 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-06-19.
35. Web site: QD ID 129291 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-08-27.
36. Web site: QD ID 131934 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-08-27.
37. Web site: QD ID 128246 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-08-27.
38. Web site: QD ID 134454 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-08-27.
39. Web site: QD ID 137436 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2019-08-27.
40. Web site: QD ID 139259 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2020-03-12.
41. Web site: QD ID 144808 Launch Studio - Listing Details. launchstudio.bluetooth.com. 2020-06-01.
42. Web site: BlueZ History. 2019-09-07. BlueZ.
43. Web site: BlueZ » Blog Archive » Release of BlueZ 5.47. www.bluez.org. 2017-10-27.
44. Web site: RN-1.2.0 - Apache Mynewt - Apache Software Foundation. cwiki.apache.org. 2018-07-02.
45. Web site: Release Notes Zephyr Kernel 1.9.0. docs.zephyrproject.org. 2020-03-21.