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ZigBee Technical Overview
Wireless JapanTokyo, Japan
July 23, 2008
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Presented by:
Drew Gislason
President and CTO
San Juan Software
Former ZigBee Alliance Secretary to the
Application Framework Group
E-mail: [email protected]
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ZigBee Technical Overview
Latest Version of the ZigBee Specification: ZigBee-2007
The ZigBee-2007 Specification contains definition of twofeature sets:
ZigBee feature set
ZigBee PRO feature set The ZigBee and ZigBee PRO feature sets interoperate,
network wise, in a limited way within a single network:
ZigBee devices may join PRO networks as an end device
ZigBee PRO devices may join ZigBee networks as an end
device ZigBee and ZigBee PRO devices fully interoperate at the
application level on the same network
ZigBee and ZigBee PRO devices fully interoperate ifstandard security mode is used on the network
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ZigBee Feature Set
ZigBee Feature Set
Ad-hoc self forming networks
Mesh and Cluster Tree
Unicast, broadcast and groupcast
Logical Device Types
Coordinator, Router and End Device
Optional Network Manager for PAN ID conflict and frequency agility
Standard Application Services
Device and Service Discovery
Optional acknowledged service
Optional fragmentation/re-assembly service
Cluster Library support to standard definition of application messages
Mechanism to support mix of Public andManufacturer Specific profiles in thesame network, all supported by standard ZigBee network and applicationfeatures
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ZigBee Feature Set
ZigBee Feature Set (continued)
Security
Authentication and Encryption at Network and Application levels.
Symmetric Key with AES-128
Key Hierarchy: Network Keys and Application Link Keys (optional)
Qualification
Platform Conformance Certification
Manufacturer Specific Product Certification
Public Profile Product Certification
Regularly Scheduled Interoperability Events
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ZigBee PRO Feature Set
ZigBee PRO Feature Set
Ad-hoc self forming networks
Mesh only
Many to One and Source Routing Enhancements
Network layer multicastSame Logical Device Types as ZigBee feature set (ZC, ZR, ZED)
Network Manager for PAN ID conflict resolution and frequency agility
Same Application Services as ZigBee feature set
Two security modes:
Standard security compatible with ZigBee feature set High security
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ZigBee PRO Feature Set
ZigBee PRO Features (continued)
Security
Symmetric Key with AES-128
Authentication and Encryption at Network and Application levels.
Key Hierarchy: Master Keys (optional), Network Keys and Link Keys(optional)
Qualification
Platform Conformance Certification
Manufacturer Specific Product Certification
Public Profile Product Certification
Regularly Scheduled Interoperability Events
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ZigBee and ZigBee PRO Protocol Stack
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Stack Architecture
IE E E 802.15.4defined
ZigBee TM Alliancedefined
End manufacturerdefined
Layerfunction
Layerinterface
Ph ysical (PHY) Layer
Medium A ccess Control (MAC ) Layer
Network (NW K) Layer-
Application Support Sublayer (APS)
APS Message
BrokerManagemen
t
APS Security
Management
Reflector
Management
ApplicationObject 240
Application
Object 1
Application (APL) Layer
ZigBee Device Object
(ZDO )
Endpoint 240
APSD E -SAP
Endpoint 1
APSD E -S AP
Endpoint 0
APSD E -S AP
NLDE -SAP
M LD E-S APM LM E-SAP
PD-SAP PLM E -S AP
Security
Management
Message
Broker
Routing
Management
Network
Management
2.4 GHz Radio 868/915 MHz Radio
Security
Service
Provider
ZDOPublic
Interfaces
Application F ramework
Z
DOManagementPlane
APSME-
SAP
NL
ME-SAP
NLME -SAP
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Application Device Type Model
802.15.4
Device Type
FFD
FullFunction Device
RFD
ReducedFunctionDevice
Distinguishes the
type of hardwareplatform
Logical
Device Type
ZigBee
Coordinator
ZigBee
Router
Distinguishes theLogical Device
Types deployed in
a specific network
ZigBee
End
Device
Application
Device Type
e.g.
Light
Sensor
e.g.
Lighting
Controller
Distinguishes the
type of device from
an end-user
perspective...
ZigBee products are a combination of Application, Logical, and Physical device types
Profiles may define specific requirements for this combination, but can also leave this up to
manufacturers
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ZigBee and ZigBee PRO Network
Communication Model (Mesh Routing)
ZigBee End Device (RFD or FFD)
ZigBee Router (FFD)
ZigBee Coordinator (FFD)
Mesh Link
Note: Mesh networking is a bandwidth and RAM efficient routing method. Mesh is
supported by both ZigBee and ZigBee Pro networks.
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ZigBee Network Communication Model
(Cluster Tree Routing)
ZigBee End Device (RFD or FFD)
ZigBee Router (FFD)
ZigBee Coordinator (FFD)
Note: Cluster Tree Routing is the backup routing method in ZigBee (SP1)
networks, used if mesh is busy.
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ZigBee PRO Network Communication
Model (Many to One and Source Routing)
ZigBee End Device (RFD or FFD)
ZigBee Router (FFD)
ZigBee Coordinator (FFD)
Concentrator
Mesh Link
Note: Concentrators may be any router in the network (not just the ZC). Source
routing allows scaling in large networks with limited RAM in most nodes.
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ZigBee and ZigBee PRO
Network Topologies and Routing
Mesh network routing permits path formation from any source device to anydestination device via a path formed by routing packets through neighbors
Table routing employs a simplified version ofAd Hoc On Demand Distance VectorRouting (AODV), an Internet Engineering Task Force (IETF) Mobile Ad Hoc Networking(MANET) submission
Used in both the ZigBee and ZigBee PRO feature sets
Cluster tree network routing directs packets up and down the tree structurecreated through network formation until they reach their destination
Must use netmask type tree routing (up and down the parent/child links)
Fails if parent/child links are not usable over time
Used only in the ZigBee feature set
Many to One and Source Routingfeatures address limitations in Mesh networkrouting where table size requirements are large in certain data transmissionscenarios
Many to One allows any device in the network to route data to a well known concentratorthrough a single routing table entry in every device
Multiple concentrators in a single network are possible
Source routing allows a concentrator to route responses back to each device supplying aMany to One data request without additional route table entries
End Devices are low powerin either feature set since they dont participate inrouting and only communicate through their parent (routers or coordinator) atapplication specified times
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ZigBee Application Model
Devices are modeled throughApplication Objects
Application Objects communicatethrough the exchange ofClusters andAttributes
Each Profile Object can contain single or
multiple Clusters and Attributes Binding mechanism ensures
interoperable exchange ofClusters/Attributes
Clusters/Attributes are sent
Directly to destination application
objects(thereby to target device)
Generic ZigBee device functions areprovided through ZigBee Device Objects
Light Switch
ZigBee Device
Objects
(e.g. ZigBee End
Device)Light Switch
Object
Light Controller
ZigBee Device
Objects
(e.g. ZigBee
Coordinator)Lighting Control
Object
On-Off
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ZigBee Application Model
Application Profiles are an agreement on a series of messages
defining an application space (for example, Home Automation or
Smart Energy)
Endpoints are a logical extension added to a single ZigBee radio
which permits support for multiple applications, addressed by the
Endpoint number (1-240)
Key Relationships:
Maximum of240 Endpoints per ZigBee Device (Endpoint 0 is reserved to
describe the generic device capabilities and Endpoint 255 is reserved for
broadcasting to all endpoints, Endpoints 241-254 are reserved for future use)
One Application Profile described per Endpoint
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Security Services Provider (SSP)
Security at each layer:
Network (NWK) layer security for network command frames (route request, routereply, route error)
Application (APL) layer security forApplication Support Sub-layer (APS) frames
Two Security Modes
Standard Mode (ZigBee and PRO feature sets) Two NWK keys, APL securityvia NWK key. Ability to switch NWK keys. Optional use ofApplication Link Keysfor pairs of communicating devices at APL.
High Security Mode (PRO feature set only) Two NWK keys, separate LinkKeys for pairs of communicating devices at APL. Master Keys with the TrustCenter for key transport and key establishment. Ability to switch NWK keys.Entity authentication between all pairs of communicating devices.
Security Implementation Trust Center Creates and distributes the Network Keys. Manages switch from
active to secondary Network Key (Standard and High Security Modes).Optionally supports Master Keys and Trust Center Link Key establishment andtransport (Optional in Standard security mode and mandatory in High Securitymode)
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Security Services Provider (SSP)
Key Hierarchy
Master Key (could be programmed in or provided *in the clear* from the
Trust Center) High Security mode only
Network Key (used for all NWK commands from any device and forAPS
messaging) Standard and High Security modes Link Keys (used for each pair of communicating devices) Standard
and High Security modes
Features in either Security Mode
Authentication and Encryption
Freshness (frame counters)
Message Integrity
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Security Service in Standard Mode
Unsecured
key-transport
NWKKey
Basis of security between
two (or group of) devices
Factory or out-of-
band installed
Frame Security
ServiceSecures all frames
(except key-transport)
Key-Transport Service
Unsecured key-transport of
NWK key
Authentication Service
Secure authenticationthat a device shares a
NWK key.
NWK key is used as basis
of security services
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Security Service in High Security Mode
Unsecured
key-transport
Link Key/NWKKey
Basis of security between
two (or group of) devices
MasterKey
Basis for long-term security
between two devices
Factory
installed
Frame Security Service
Secures all frames
(except key-transport)
Key-Transport Service
Secure key-transport ofgrouplink keys
Key-Transport Service
Secure key-transport ofmasterkeys
Authentication Service
Secure authentication that adevice shares a link key.
Link key is used as basis of
security services
Secured key-transport
from trust center
SKKE
protocol or
Key
Transport
Secured key-transport
of group link keys
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Feature Sets andApplication Deployment
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Feature Sets
Agreement of stack parameters, settings and policies for a familyof application profiles (including manufacturer specific applicationprofiles)
Current feature sets:
ZigBee (mesh routing+cluster tree routing) Beacon-less, mesh network
Supports any application profile
ZigBee PRO(mesh routing with enhancements)
Beacon-less, mesh network
Enhanced support for large networks
Enhanced security mode
Application layer compatibility with ZigBee feature set
Feature set identifier supplied in beacon payload. Devices joinappropriate networks supporting desired feature set.
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Deployment
Commissioning
Devices are programmed for a specific feature set or to join specificalternate feature set networks
If multiple networks with the same feature set are present, the applicationneeds mechanisms to help the device select the correct network
Provision security keys (unless they are provided over the air)
Establish command/control relationships in the network (binding)
Commissioning can take place via a dedicated commissioning tool(laptop or PDA) or via installation key presses on a remote control orthe device itself
Common Maintenance Operations requiring application supportAdding new devices to an existing network
Combining networks
Replacing devices in a network
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Summary
The ZigBee and ZigBee PRO feature sets provide an ad-hoc,self forming network topology supporting mesh routing
ZigBee and ZigBee PRO feature sets provide an agreementon specific configuration parameters and network settings tocreate multi-vendor interoperable networks
ZigBee application profiles are an agreement on messageformats and command/response exchanges which provide adocumented method to create interoperable device types
Current status on the ZigBee Ecosystem:
45 product listings for the ZigBee and ZigBee PRO feature setson 21 platforms provides application developers with a richenvironment to deploy interoperable products.
28 Smart Energy and Home Automation product manufacturersat last months interoperability event!
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ZigBee Technical Overview
Questions?