IEEE 802.11 無線區域網路系統及通訊協定林文宗博士現任：明新科技大學資訊工程系助理教授明新科技大學電算中心網路組組長經歷：工研院資通所無線通訊技術組顧問

IEEE 802.11IEEE 802.11無線區域網路系統及通訊協定無線區域網路系統及通訊協定

林文宗博士　　　現任：明新科技大學資訊工程系助理教授　　　　　　明新科技大學電算中心網路組組長　　　經歷：工研院資通所無線通訊技術組顧問　　　　　　麟瑞科技無線通訊技術顧問　　　　　　明新科技大學電算中心網路組組長　　　　　　國立清華大學資訊工程學系博士　　　 E-mail: [email protected]

802.11s D3802.11s D3

Mesh NetworkMesh Network

(C) All rights reserved by Assistant Professor Wen-Tsung Lin.(C) All rights reserved by Assistant Professor Wen-Tsung Lin. 33

WLAN Mesh definitionsWLAN Mesh definitionsA WLAN Mesh is an IEEE 802.11-based A WLAN Mesh is an IEEE 802.11-based

Wireless Distribution System (Wireless Distribution System (WDS))part of a Distribution System, consisting of a part of a Distribution System, consisting of a

set of two or more Mesh Access Point set of two or more Mesh Access Point interconnected via IEEE 802.11 wireless links interconnected via IEEE 802.11 wireless links and communicating via the WLAN Mesh and communicating via the WLAN Mesh Services.Services.

automatic topology learningautomatic topology learningdynamic path selectiondynamic path selection

across multiple hopsacross multiple hops


Usage ModelsUsage Models (1) (1)

Office

Bedroom

Den

Internet

Mesh AP

Mesh SoftAP PCs Mesh AP CE Devices

Non-MeshClients

Home Network

Non-meshclients

Soft Mesh AP

Small Enterprise


Usage Models (Usage Models (22))

Inside APOutside APInside APOutside AP

Large enterprise usage model.

University Campus

Community Area

Park Area

University Campus

Community Area

Park Area

University Campus

Community Area

Park Area

Campus/ Community Network


Usage Models (Usage Models (33))

Public Safety Public Access: Urban Streets


New DefinitionsNew Definitions Mesh Awake WindowMesh Awake Window

A period of time where the mesh STA operates in awake state afteA period of time where the mesh STA operates in awake state after its Beacon or Probe Response frame transmission that container its Beacon or Probe Response frame transmission that contained the Mesh Awake Window element.d the Mesh Awake Window element.

MCCA (MCCA (mesh coordinated channel accessmesh coordinated channel access)) A coordination function for the MBSS.A coordination function for the MBSS.

MCCAOP (mesh coordinated channel access opportunity)MCCAOP (mesh coordinated channel access opportunity) A period of time that is set up between a transmitter and a receiveA period of time that is set up between a transmitter and a receive

r.r. MCF (mesh coordination function)MCF (mesh coordination function)

A coordination function that combines aspects of the contention-bA coordination function that combines aspects of the contention-based and reduced contention access methods.ased and reduced contention access methods.

The MCF includes the functionality provided by both enhanced disThe MCF includes the functionality provided by both enhanced distributed channel access (EDCA) and mesh controlled channel acctributed channel access (EDCA) and mesh controlled channel access (MCCA).ess (MCCA).

Mesh BSSMesh BSSThe 802.11 wireless mesh networkThe 802.11 wireless mesh network


Overview – Mesh BSSOverview – Mesh BSS A mesh BSS is an IEEE 802.11 LAN consisting of autonoA mesh BSS is an IEEE 802.11 LAN consisting of autono

mous STAs.mous STAs. Inside the mesh BSS, all the STAs canInside the mesh BSS, all the STAs can

establish peer-to-peer wireless linksestablish peer-to-peer wireless links transfer messages mutually without any topological constraints.transfer messages mutually without any topological constraints.

multi-hop capabilitymulti-hop capability messages may be transferred between STAs that are not in direct messages may be transferred between STAs that are not in direct

communication with each other over a single instance of the wirelcommunication with each other over a single instance of the wireless medium.ess medium.

all STAs in a mesh BSS are directly connected at the MAC layerall STAs in a mesh BSS are directly connected at the MAC layer even if the STAs are out of coverage area of each other. even if the STAs are out of coverage area of each other.

enhances the range of the STAsenhances the range of the STAs significant benefit for a wireless LAN deploymentsignificant benefit for a wireless LAN deployment some of the STAs may only propagate the messages for other STsome of the STAs may only propagate the messages for other ST

As.As.


Overview – Mesh STAOverview – Mesh STA mesh STAmesh STA

QoS STAsQoS STAs support mesh servicessupport mesh services Mesh Basic Service Set (MBSS)Mesh Basic Service Set (MBSS)

The QoS functionality of a mesh STA is limited The QoS functionality of a mesh STA is limited Mesh STAs support non-AP STA operation under the HCF using Mesh STAs support non-AP STA operation under the HCF using

TXOPs gained through the EDCA mechanism.TXOPs gained through the EDCA mechanism. MeshBSS (MBSS)MeshBSS (MBSS)

no HC, none of HCCA, polled TXOP operation, admission control no HC, none of HCCA, polled TXOP operation, admission control or TSPEC setup are applicable for mesh STAsor TSPEC setup are applicable for mesh STAs

Mesh STAs may utilize No Ack, no explicit acknowledgment and BMesh STAs may utilize No Ack, no explicit acknowledgment and Block Ack operation.lock Ack operation.


Example of MBSS – Example of MBSS – mesh STAs, mesh APs, and portalsmesh STAs, mesh APs, and portals


Example of MBSSExample of MBSS

Distribution SystemDistribution System(DS)(DS)

WLAN MeshWLAN Mesh

Mesh LinksMesh Links802.11 MAC/PHY802.11 MAC/PHY

802.11 BSS802.11 BSS

802.11 ESS802.11 ESS

L2 Switch

Mesh PortalMesh Portal

Mesh APMesh AP

Mesh APMesh AP

STASTA

L3 Router

Portal


Mesh functionalitiesMesh functionalities Mesh discoveryMesh discovery Mesh peering managementMesh peering management Mesh securityMesh security Mesh beaconing and synchronizationMesh beaconing and synchronization Mesh Coordination FunctionMesh Coordination Function Mesh power managementMesh power management Mesh channel switchingMesh channel switching Three address, four address, and extended addressed Three address, four address, and extended addressed

frame formatsframe formats Mesh Path Selection and ForwardingMesh Path Selection and Forwarding Interworking with external networksInterworking with external networks Intra-Mesh Congestion ControlIntra-Mesh Congestion Control


Mesh discoveryMesh discovery Scanning to discover the operating mesh BSS.Scanning to discover the operating mesh BSS.

active scanning scanning passive scanning scanning

Each Each mesh STA is responsible for is responsible for transmitting transmitting Beacon frames periodically frames periodically responding with the responding with the Probe Response frame when the P frame when the P

robe Request frame is receivedrobe Request frame is received so that the neighbor mesh STAs can perform the mesh so that the neighbor mesh STAs can perform the mesh

discovery appropriately.discovery appropriately. The identification of the mesh BSS is given by the The identification of the mesh BSS is given by the

Mesh ID element contained in the Beacon and th contained in the Beacon and the Probe Response frames.e Probe Response frames.

1515

Topology discoveryTopology discovery Mesh PointsMesh Points

Passive scanningPassive scanning Periodic beaconsPeriodic beacons

Active scanningActive scanning ProbesProbes

Look for matching profilesLook for matching profiles (Mesh ID, Path Selection Prot(Mesh ID, Path Selection Prot

ocol ID, Link Metric ID)ocol ID, Link Metric ID) Membership is determined bMembership is determined b

y securepeer links with neigy securepeer links with neighborshbors


Multi-radio supportMulti-radio support Each MP may have one or more logical radio interfaceEach MP may have one or more logical radio interface Each interface belongs to one Unified Channel GraphEach interface belongs to one Unified Channel Graph


RoutingRouting Optimizations for unicast trafficOptimizations for unicast traffic Might support for multicast/broadcastMight support for multicast/broadcast 802.11s Routing802.11s Routing

Layer-2 routing based on MAC addressesLayer-2 routing based on MAC addresses HWMPHWMP

Hybrid Wireless Mesh ProtocolHybrid Wireless Mesh Protocol Default routing protocolDefault routing protocol

RA-OLSRRA-OLSR Radio-Aware Optimized Link State RoutingRadio-Aware Optimized Link State Routing Optional routing protocolOptional routing protocol


RA-OLSR – Key ConceptsRA-OLSR – Key Concepts Multi-point relays (MPRs)Multi-point relays (MPRs)

Cover 2-hop neighborhoodCover 2-hop neighborhood Only MPRs send updatesOnly MPRs send updates

Message reduction in spaceMessage reduction in space

Link state reduction (optional)Link state reduction (optional) Main ideaMain idea

Farther away nodes are updated with less frequencyFarther away nodes are updated with less frequency

Message reduction in timeMessage reduction in time


Mesh peering managementMesh peering management

A mesh BSS is formed based on mutual linA mesh BSS is formed based on mutual link establishment.k establishment.When two neighbor mesh STAs agree to establWhen two neighbor mesh STAs agree to establ

ish a link each other, they establish mesh peeriish a link each other, they establish mesh peering and become peer mesh STAs upon the sucng and become peer mesh STAs upon the successful completion of this process.cessful completion of this process.

A mesh STA may establish mesh peering with A mesh STA may establish mesh peering with multiple neighbor mesh STAs.multiple neighbor mesh STAs.


Mesh securityMesh security In an MBSS, In an MBSS, mesh link security protocols are used to are used to auth

enticate a mesh peering and to a mesh peering and to establish session keys bet session keys between a pair of mesh STAs.ween a pair of mesh STAs. Key derivation functionKey derivation function Authentication Using a Pre-Shared SecretAuthentication Using a Pre-Shared Secret Keys and key derivation algorithm for the mesh Authenticated MeKeys and key derivation algorithm for the mesh Authenticated Me

sh Peering Exchangesh Peering Exchange Authenticated Mesh Peering ExchangeAuthenticated Mesh Peering Exchange Mesh Group Key HandshakeMesh Group Key Handshake

Mesh link security protocols rely on the existence of a comMesh link security protocols rely on the existence of a common pairwise master key (PMK) at the two mesh STAs.mon pairwise master key (PMK) at the two mesh STAs.


Mesh beaconing and Mesh beaconing and synchronizationsynchronization

In order to assist mesh discovery , all the mIn order to assist mesh discovery , all the mesh STAs transmit Beacon frames periodicesh STAs transmit Beacon frames periodically.ally.mesh power managementmesh power managementsynchronization in a mesh BSSsynchronization in a mesh BSS

Neighbor Offset ProtocolNeighbor Offset Protocol default synchronization protocoldefault synchronization protocol

Mesh Beacon Collision AvoidanceMesh Beacon Collision Avoidance mitigate the collision of Beacon frames among hidden nodmitigate the collision of Beacon frames among hidden nod

es.es.


Mesh Coordination FunctionMesh Coordination Function

A mesh STA uses the Mesh Coordination A mesh STA uses the Mesh Coordination Function (MCF) for the channel access.Function (MCF) for the channel access.MCF contention-based channel accessMCF contention-based channel access

EDCAEDCA contention-based channel accesscontention-based channel access

MCCAMCCAMCF controlled channel access (MCCA)MCF controlled channel access (MCCA)MCCA is a reservation based channel access and MCCA is a reservation based channel access and

aims to optimize the efficiency of frame exchanges aims to optimize the efficiency of frame exchanges in the mesh BSS.in the mesh BSS.


Mesh power managementMesh power management The mesh STA The mesh STA tracks the power mode of each of the power mode of each of

its neighbor peer mesh STAs, and delivers the fraits neighbor peer mesh STAs, and delivers the frames based on the rules defined in Power save in mes based on the rules defined in Power save in a mesh BSS.a mesh BSS.

3 modes3 modes Active modeActive mode Light Sleep modeLight Sleep mode the Deep Sleep modethe Deep Sleep mode


Mesh channel switchingMesh channel switching MBSS channel switching protocolMBSS channel switching protocol

When a mesh STA tries to switch the operating When a mesh STA tries to switch the operating channel, it uses the channel switch protocol.channel, it uses the channel switch protocol.

The channel switch protocol enables the propagation of The channel switch protocol enables the propagation of the channel switching event throughout the mesh BSS, the channel switching event throughout the mesh BSS, prior to the channel switch execution.prior to the channel switch execution.


Three address, four address, and Three address, four address, and extended addressed frame formatsextended addressed frame formats

Three address, four address, and Three address, four address, and extended addressed frame formats enable the distribution addressed frame formats enable the distribution of messages over of messages over multiple instances of the of the wireless medium within a mesh BSS and wireless medium within a mesh BSS and integration to the ESS.integration to the ESS. Frame addressing and forwarding in an MBSSFrame addressing and forwarding in an MBSS


Mesh Path Selection and Mesh Path Selection and ForwardingForwarding

Mesh Path Selection enables Mesh Path Selection enables route discovery over multiple instances of the wireless medium over multiple instances of the wireless medium within a mesh BSS.within a mesh BSS.

HWMPHWMP Hybrid Wireless Mesh ProtocolHybrid Wireless Mesh Protocol default path selection protocol for the mesh BSS.default path selection protocol for the mesh BSS.

proactive path selection reactive path selection

Link metrics are used to determine the candidate path Link metrics are used to determine the candidate path to the destination of the mesh path.to the destination of the mesh path.

link metriclink metric airtime link metricairtime link metric


MAC data transport over an MBSSMAC data transport over an MBSS


Interworking with external networksInterworking with external networks

A mesh BSS may have A mesh BSS may have zero or more portals that may be connected to one or portals that may be connected to one or more LAN segments.more LAN segments.multiple portalsmultiple portals

configurationconfigurationmanage the configurationmanage the configuration


Intra-mesh congestion controlIntra-mesh congestion control Intra-mesh congestion control Intra-mesh congestion control

offer flow control over the multi-hop environmentoffer flow control over the multi-hop environment mitigate the wasteful wireless medium utilization mitigate the wasteful wireless medium utilization

caused by buffer overflow at downstream nodescaused by buffer overflow at downstream nodes

three main mechanismsthree main mechanisms Local congestion monitoringLocal congestion monitoring congestion detection, congestion control signalingcongestion detection, congestion control signaling local rate control.local rate control.


Access controlAccess control AuthenticationAuthentication

four authentication methodsfour authentication methods Open System authenticationOpen System authentication

admits any STA to the DSadmits any STA to the DS Shared Key authenticationShared Key authentication

relies on WEP to demonstrate knowledge of a WEP encryption krelies on WEP to demonstrate knowledge of a WEP encryption keyey

FT authentication (fast BSS transition defined in 802.11r) relies on keys derived during the initial mobility domain associatiorelies on keys derived during the initial mobility domain associatio

n to authenticate the non-AP stationsn to authenticate the non-AP stations Simultaneous Authentication of Equals (SAE)

uses finite field cryptography to prove knowledge of a shared password

Preauthentication: authenticated to many APs simultaneously


Establishing the IEEE 802.11 Establishing the IEEE 802.11 associationassociation


Frame formatFrame format


Frame control field (1)Frame control field (1)

Type and subtype fieldsType and subtype fieldsValid type and subtype combinationsValid type and subtype combinations

EDITORIAL NOTE—This subtype value needs to be allocated before sponsor ballot by ANA.


Frame control field (2)Frame control field (2)

To DS and From DS fieldsTo DS and From DS fields


Frame control field (3)Frame control field (3) Power Management fields In an MBSSPower Management fields In an MBSS

The value of this field indicates the mode in which the mesh STA The value of this field indicates the mode in which the mesh STA will be after the completion of the frame exchange sequence.will be after the completion of the frame exchange sequence.

A value of A value of 0 in a group addressed frame indicates that the mesh S indicates that the mesh STA will be in active mode.TA will be in active mode.

For For non-peer mesh STAs, a value of 1 in a group addressed fram, a value of 1 in a group addressed frame indicates that the mesh STA will be in power save mode.e indicates that the mesh STA will be in power save mode.

For the peer mesh STAs the link specific mesh power mode rules For the peer mesh STAs the link specific mesh power mode rules are determined by the Power Management field in the individually are determined by the Power Management field in the individually addressed frame exchanged between these peers.addressed frame exchanged between these peers.


Frame control field (4)Frame control field (4) More Data field in MBSSMore Data field in MBSS

The More Data field is set to 1 by mesh STAs for The More Data field is set to 1 by mesh STAs for individually addressed MSDUs, A-MSDUs, or MMPDUs addressed MSDUs, A-MSDUs, or MMPDUs sent to a neighbor peer mesh STA when there are more fra when there are more frames to be transmitted to that mesh STA in the transmittmes to be transmitted to that mesh STA in the transmitter’s current beacon interval.er’s current beacon interval.

The More Data field is set to 1 by mesh STAs for The More Data field is set to 1 by mesh STAs for group addressed MSDUs, or MMPDUs when there are more addressed MSDUs, or MMPDUs when there are more group addressed frames to be transmitted in the transgroup addressed frames to be transmitted in the transmitter’s current beacon interval.mitter’s current beacon interval.


QoS control field (1)QoS control field (1)


QoS control field (2)QoS control field (2)


QoS control field (3)QoS control field (3) EOSP (end of service period) subfieldEOSP (end of service period) subfield

The mesh STA sets the EOSP subfield to 1 in its transmission and The mesh STA sets the EOSP subfield to 1 in its transmission and retransmissions of the PSP’s (Peer Service Period) final frame to retransmissions of the PSP’s (Peer Service Period) final frame to end a PSP and sets it to 0 otherwise.end a PSP and sets it to 0 otherwise.

Mesh Control Present subfield (1-bit)Mesh Control Present subfield (1-bit) the mesh STA sets Mesh Control Present subfield to 1.the mesh STA sets Mesh Control Present subfield to 1.

Mesh Power Save Level subfieldMesh Power Save Level subfield Power Management field = 1

1 – mesh STA is operating in deep sleep mode1 – mesh STA is operating in deep sleep mode 0 – mesh STA is operating in light sleep mode0 – mesh STA is operating in light sleep mode

Receiver Service Period Initiation (RSPI) subfield (1-bit)Receiver Service Period Initiation (RSPI) subfield (1-bit) 0 – the peer service period for the peer trigger frame receiver is n0 – the peer service period for the peer trigger frame receiver is n

ot initiated.ot initiated. 1 – the peer service period is initiated.1 – the peer service period is initiated.


Frame Body field(1)Frame Body field(1) Mesh Control field (1)Mesh Control field (1)

present inpresent in unfragmented mesh data frameunfragmented mesh data frame the first fragment of the mesh data framethe first fragment of the mesh data frame the the multi-hop management action frame transmitted by a mesh transmitted by a mesh

STASTA inserted inserted as a header of the frame body data and place and place

d as following:d as following: When the frame body contains When the frame body contains other than A-MSDU and the fra and the fra

me is me is not encrypted, the Mesh Control field is placed in the firs, the Mesh Control field is placed in the first octets of the frame body.t octets of the frame body.

When the frame body contains When the frame body contains other than A-MSDU and the fra and the frame is me is encrypted, the Mesh Control field is placed in the , the Mesh Control field is placed in the first octets of the encrypted data portion. of the encrypted data portion.

When the frame body contains When the frame body contains A-MSDU, the Mesh Control fiel, the Mesh Control field is placed in the d is placed in the Aggregate MSDU subframe header..


Frame Body field (2)Frame Body field (2)

Mesh Control field (2)Mesh Control field (2)


Frame Body field (3)Frame Body field (3) Mesh Control field (3)Mesh Control field (3)

Mesh Flags fieldMesh Flags field 8-bit 8-bit Mesh Control processingMesh Control processing

control mesh-specific header processing,control mesh-specific header processing, e.g., for mesh address extension.e.g., for mesh address extension.

Time to liveTime to live 1-octet1-octet use in multi-hop forwardinguse in multi-hop forwarding

to aid in limiting the effect of transitory path selection loopsto aid in limiting the effect of transitory path selection loops mesh sequence numbermesh sequence number

a four octeta four octet to suppress duplicatesto suppress duplicates

mesh address extension fieldmesh address extension field in some cases a 6, 12, or 18-octet containing extended addressesin some cases a 6, 12, or 18-octet containing extended addresses enabling up to a total of 6 addresses in mesh framesenabling up to a total of 6 addresses in mesh frames


Frame Body field (4)Frame Body field (4) Mesh Control field (4)Mesh Control field (4)

Mesh Flags fieldMesh Flags field

Address Extension Mode fieldAddress Extension Mode field indicate the contents of the Mesh Address Extension field.indicate the contents of the Mesh Address Extension field.


Frame Body field (5)Frame Body field (5)

Mesh Control field (5)Mesh Control field (5)Valid values for the Address Extension ModeValid values for the Address Extension Mode

Format of individual frame Format of individual frame typestypes


Control FrameControl Frame

PS-PollPS-PollPS-Poll frame is not used in MBSSPS-Poll frame is not used in MBSS

Management FramesManagement Frames


Beacon frame format (1)Beacon frame format (1)


Beacon frame format (2)Beacon frame format (2)


Probe Response frame bodyProbe Response frame body

Mesh ProcedureMesh Procedure


Mesh discovery (1)Mesh discovery (1) Beacon and/or Probe Request framesBeacon and/or Probe Request frames

Mesh Peering management (see 11C.3 (Mesh peering managemMesh Peering management (see 11C.3 (Mesh peering management)) requires that mesh STAs obtain information about neighbor ent)) requires that mesh STAs obtain information about neighbor mesh STAs.mesh STAs.

Mesh IDMesh ID indicates the identity of an MBSSindicates the identity of an MBSS A matching Mesh ID is necessary for joining a mesh.A matching Mesh ID is necessary for joining a mesh.

Candidate peer mesh STA discoveryCandidate peer mesh STA discovery installed in mesh capable devices by a variety of means that are installed in mesh capable devices by a variety of means that are b

eyond the scope of this standard. e.g., “Mike’s Mesh”

SSID field in Beacon or Probe Response frames are set to the wildcard when the frame is transmitted by mesh STA.

The wildcard SSID is used to notify non-mesh STAs that the mesh STA is neither a part of an infrastructure BSS nor an IBSS, so that the non-mesh STAs do not try to join the mesh BSS.


Mesh discovery (2)Mesh discovery (2)

Profiles for extensibilityProfiles for extensibilityA mesh STA shall support at least one mesh A mesh STA shall support at least one mesh

profile, and shall activate one mesh profile. profile, and shall activate one mesh profile. A Mesh IDA Mesh IDA path selection protocol identifierA path selection protocol identifierA path selection metric identifierA path selection metric identifierA congestion control mode identifierA congestion control mode identifierA synchronization protocol identifierA synchronization protocol identifierAn authentication protocol identifierAn authentication protocol identifier


Mesh discovery (3)Mesh discovery (3) Candidate peer mesh STA discovery (1)Candidate peer mesh STA discovery (1)

discover candidate peer mesh STAs and their configurdiscover candidate peer mesh STAs and their configurationation

When a mesh STA discovers one or more candidate peer mesWhen a mesh STA discovers one or more candidate peer mesh STAs, it may try to establish a mesh peering with the candidh STAs, it may try to establish a mesh peering with the candidate peer mesh STA and join an MBSS depending on the candiate peer mesh STA and join an MBSS depending on the candidate peer mesh STA’s configuration.date peer mesh STA’s configuration.

Mesh STA may continue the discovery procedure after joining Mesh STA may continue the discovery procedure after joining an MBSS in order to look for other candidate peer mesh STAs an MBSS in order to look for other candidate peer mesh STAs to establish mesh peerings.to establish mesh peerings.

When a mesh STA joins an MBSS that mesh STA shall use MLMWhen a mesh STA joins an MBSS that mesh STA shall use MLME.STARTBEACONING.request with the mesh profile of the discoE.STARTBEACONING.request with the mesh profile of the discovered candidate peer mesh STA.vered candidate peer mesh STA.

After successful MLMESTARTBEACONING.request primitive the After successful MLMESTARTBEACONING.request primitive the joining mesh STA shall transmit beacons.joining mesh STA shall transmit beacons.


Mesh discovery (4)Mesh discovery (4)Candidate peer mesh STA discovery (2)Candidate peer mesh STA discovery (2)

A mesh STA performs passive or active scans tA mesh STA performs passive or active scans to discover neighbor mesh STAs.o discover neighbor mesh STAs.

A discovered mesh STA shall be considered a A discovered mesh STA shall be considered a candidate peer mesh STA if and only if all of thcandidate peer mesh STA if and only if all of the following conditions are met:e following conditions are met:A Beacon / Probe Response frame is received from A Beacon / Probe Response frame is received from

the discovered mesh STA.the discovered mesh STA.Mesh ID in the received Beacon / Probe Response fMesh ID in the received Beacon / Probe Response f

rame that matches the Mesh ID of the scanning mesrame that matches the Mesh ID of the scanning mesh STA’s mesh profile.h STA’s mesh profile.



The received Beacon or Probe Response frame contains a MeThe received Beacon or Probe Response frame contains a Mesh Configuration element that containssh Configuration element that contains

A path A path selection protocol identifier matching the scanning mesh S matching the scanning mesh STA’s path selection protocol identifierTA’s path selection protocol identifier

A path A path selection metric identifier matching the scanning mesh ST matching the scanning mesh STA’s path selection metric identifierA’s path selection metric identifier

A A congestion control mode identifier matching the scanning mesh matching the scanning mesh STA’s congestion control mode identifier.STA’s congestion control mode identifier.

A A synchronization protocol identifier matching the scanning mesh matching the scanning mesh STA’s synchronization protocol identifier.STA’s synchronization protocol identifier.

An An authentication protocol identifier matching the scanning mesh matching the scanning mesh STA’s authentication protocol identifier.STA’s authentication protocol identifier.

An Accepting Mesh Peerings field (in the Mesh Configuration fielAn Accepting Mesh Peerings field (in the Mesh Configuration field) set to 1.d) set to 1.

The BSSBasicRateSet indicated by the received Beacon or PrThe BSSBasicRateSet indicated by the received Beacon or Probe Response frame matches the BSSBasicRateSet of the scobe Response frame matches the BSSBasicRateSet of the scanning mesh STA.anning mesh STA.



A mesh STA performs passive or active scans to discover neighbA mesh STA performs passive or active scans to discover neighbor mesh STAs.or mesh STAs.

If the mesh STA is a member of an MBSS, exactly one mesh profile is If the mesh STA is a member of an MBSS, exactly one mesh profile is active.active.

When a mesh STA deactivates a mesh profile, session information obtainWhen a mesh STA deactivates a mesh profile, session information obtained while operating under that profile, such as local forwarding information ed while operating under that profile, such as local forwarding information and security associations (and related keys) created under that mesh profand security associations (and related keys) created under that mesh profile, shall be deleted.ile, shall be deleted.

A candidate peer mesh STAs becomes a peer mesh STAs only after tA candidate peer mesh STAs becomes a peer mesh STAs only after the mesh peering management protocol has successfully established he mesh peering management protocol has successfully established a mesh peering between the two mesh STAs.a mesh peering between the two mesh STAs.

When a mesh STA starts an MBSS that mesh STA shall use MLME.SWhen a mesh STA starts an MBSS that mesh STA shall use MLME.STARTBEACONING.request and specify the mesh profile for the initiatTARTBEACONING.request and specify the mesh profile for the initiated MBSS.ed MBSS.

After successful MLME-STARTBEACONING.request primitive the mesh After successful MLME-STARTBEACONING.request primitive the mesh STA shall transmit beacons.STA shall transmit beacons.


MBSS peering management MBSS peering management framework (1)framework (1)

The MBSS peering management framework supports all fThe MBSS peering management framework supports all functions to establish, management, and tear down peerinunctions to establish, management, and tear down peerings between mesh STAs.gs between mesh STAs.

MBSS peering management functions shall be invoked aftMBSS peering management functions shall be invoked after a candidate peering mesh STA is discovered via Candier a candidate peering mesh STA is discovered via Candidate peer mesh STA discovery procedure.date peer mesh STA discovery procedure.

One of the following protocols shall be invoked to establisOne of the following protocols shall be invoked to establish the mesh peering with the candidate peer mesh STA:h the mesh peering with the candidate peer mesh STA: The Mesh Peering Management (MPM) protocol that establishes The Mesh Peering Management (MPM) protocol that establishes

and manages the mesh peering between candidate peer mesh STand manages the mesh peering between candidate peer mesh STAs.As.

The Authenticated Mesh Peering Exchange (AMPE) protocol that The Authenticated Mesh Peering Exchange (AMPE) protocol that establishes and manages mesh peering and mesh TKSA between establishes and manages mesh peering and mesh TKSA between candidate peer mesh STAs.candidate peer mesh STAs.



Mesh STA shall use a Mesh Peering Instance CoMesh STA shall use a Mesh Peering Instance Controller to manage all mesh peering instances estntroller to manage all mesh peering instances established or in the process of establishment or teaablished or in the process of establishment or teardown with its peer mesh STAs and candidate perdown with its peer mesh STAs and candidate peer mesh STAs.er mesh STAs.




MBSS peering management framewMBSS peering management framework (4)ork (4)

Mesh peering Instance ControllerMesh peering Instance Controller To manage mesh peering instances by MPM (To manage mesh peering instances by MPM (Mesh Mesh

Peering ManagementPeering Management) and AMPE () and AMPE (Authenticated Mesh Authenticated Mesh Peering ExchangePeering Exchange).).

support the following functionssupport the following functions Create and destroy MPM finite state machines and AMPE finitCreate and destroy MPM finite state machines and AMPE finit

e state machinese state machines Manage instance identifier and mesh TKSA states for each meManage instance identifier and mesh TKSA states for each me

sh peering instancesh peering instance Pre-process the mesh peering instance identifier of the incomiPre-process the mesh peering instance identifier of the incomi

ng mesh peering management frames and pass the frames to ng mesh peering management frames and pass the frames to the corresponding protocol finite state machine with matching ithe corresponding protocol finite state machine with matching instance identifiernstance identifier

Pass internal command to corresponding protocol finite state Pass internal command to corresponding protocol finite state machine which has matching instance identifiermachine which has matching instance identifier



Creating mesh peering instance and Mesh TKSA for a peCreating mesh peering instance and Mesh TKSA for a peer mesh STAer mesh STA If a mesh PMKSA (pairwise master key security association) is estIf a mesh PMKSA (pairwise master key security association) is est

ablished with the candidate peer mesh STA, the mesh peering insablished with the candidate peer mesh STA, the mesh peering instance controller shall generate an AMPE finite state machine.tance controller shall generate an AMPE finite state machine.

Multiple mesh peering instances with the same candidate peer meMultiple mesh peering instances with the same candidate peer mesh STA may be initiated at any time.sh STA may be initiated at any time.

once a mesh peering is established successfully, all other mesh peerionce a mesh peering is established successfully, all other mesh peering instances with the same peer mesh STA shall be closed properly.ng instances with the same peer mesh STA shall be closed properly.

A new mesh peering instance may be started when the mesh STA A new mesh peering instance may be started when the mesh STA already maintains a valid mesh peering with the same peer mesh already maintains a valid mesh peering with the same peer mesh STA, due to the change of some mesh peering parameter.STA, due to the change of some mesh peering parameter.

Once the new mesh peering is established successfully, the previous Once the new mesh peering is established successfully, the previous valid mesh peering shall be closed properly.valid mesh peering shall be closed properly.



Deleting mesh peering instancesDeleting mesh peering instancesCNCL eventCNCL event

closing the mesh peering instance as well as the Meclosing the mesh peering instance as well as the Mesh TKSA that is bound to the mesh peeringsh TKSA that is bound to the mesh peering

The mesh peering instance closure may be trigThe mesh peering instance closure may be triggered by receipt of a gered by receipt of a Mesh Peering Close frame from the peer mesh STA or candidate peer m from the peer mesh STA or candidate peer mesh STA.esh STA.The Mesh Peering Close frame shall be passed to tThe Mesh Peering Close frame shall be passed to t

he corresponding mesh peering instance finite state he corresponding mesh peering instance finite state machine for further processing.machine for further processing.



Pre-processing Mesh Peering Management FramPre-processing Mesh Peering Management Frameses The mesh STA shall pre-process the incoming mesh pThe mesh STA shall pre-process the incoming mesh p

eering management frame.eering management frame. The MPM FSMs are identified by a set of data including localLiThe MPM FSMs are identified by a set of data including localLi

nkID, peerLinkID, localMAC, and peerMAC.nkID, peerLinkID, localMAC, and peerMAC. The mesh peering instance controller shall either discard the frThe mesh peering instance controller shall either discard the fr

ame or pass it to the corresponding active mesh peering instaame or pass it to the corresponding active mesh peering instance finite state machine for further processing.nce finite state machine for further processing.

If the Mesh Peering Protocol Identifier is set to “Mesh Peering If the Mesh Peering Protocol Identifier is set to “Mesh Peering Management Protocol”, Mesh Peering Management informatioManagement Protocol”, Mesh Peering Management information element shall be n element shall be pre-processed to identify the mesh peering to identify the mesh peering instance.instance.

The Authenticated Mesh Peering information element and MIC, if The Authenticated Mesh Peering information element and MIC, if present, shall be ignored.present, shall be ignored.


Mesh peering managementMesh peering management (1) (1) The Mesh Peering Management protocol is used to establisThe Mesh Peering Management protocol is used to establis

h, maintain, and close mesh peerings between mesh STAs h, maintain, and close mesh peerings between mesh STAs when security is not required.when security is not required. The MPM protocol uses mesh peering open frames, mesh peering The MPM protocol uses mesh peering open frames, mesh peering

confirm frames, and mesh peering close frames to establish, managconfirm frames, and mesh peering close frames to establish, manage, and tear down a mesh peering.e, and tear down a mesh peering.

After discovering a candidate peer mesh STA, the mesh STA may sAfter discovering a candidate peer mesh STA, the mesh STA may start the Mesh Peering Management protocol to establish a mesh petart the Mesh Peering Management protocol to establish a mesh peering with the candidate peer mesh STA.ering with the candidate peer mesh STA.

The SME controlling the mesh STA uses the Mesh Peering Instance CThe SME controlling the mesh STA uses the Mesh Peering Instance Controller to manage mesh peering instances.ontroller to manage mesh peering instances.

A mesh peering instance is a logical entity that the mesh STA uses to hA mesh peering instance is a logical entity that the mesh STA uses to handle a mesh peering or an attempt of establishing a mesh peering.andle a mesh peering or an attempt of establishing a mesh peering.

A mesh STA shall assign an AID to every peer mesh STA during the mA mesh STA shall assign an AID to every peer mesh STA during the mesh peering establishment procedure.esh peering establishment procedure.

AID 0 is reserved to indicate the presence of buffered groupcast MSDU is reserved to indicate the presence of buffered groupcast MSDUs and MMPDUs.s and MMPDUs.


Mesh peering managementMesh peering management (2) (2) The mesh STA shall start the mesh peering management The mesh STA shall start the mesh peering management

protocol in either of the following two cases.protocol in either of the following two cases. In case one, the mesh STA passively listen to incoming Mesh PeeIn case one, the mesh STA passively listen to incoming Mesh Pee

ring Open requests from a candidate peer mesh STA.ring Open requests from a candidate peer mesh STA. In case two, the mesh STA actively creates a mesh peering instanIn case two, the mesh STA actively creates a mesh peering instan

ce to establish a mesh peering with a candidate peer mesh STA.ce to establish a mesh peering with a candidate peer mesh STA.

A mesh peering instance ends when the mesh peering is A mesh peering instance ends when the mesh peering is closed.closed.


Mesh peering managementMesh peering management (3) (3) Processing Mesh Peering Management FramesProcessing Mesh Peering Management Frames

Self Protected Action framesSelf Protected Action frames The mesh STA shall process mesh peering instance idThe mesh STA shall process mesh peering instance id

entifier in the incoming mesh peering management fraentifier in the incoming mesh peering management frame using the Mesh Peering Instance Controller.me using the Mesh Peering Instance Controller.

Mesh Peering Management frames accepted by the MMesh Peering Management frames accepted by the Mesh Peering Instance Controller shall be passed to the esh Peering Instance Controller shall be passed to the corresponding mesh peering management state machicorresponding mesh peering management state machine for further processing.ne for further processing.

The MPM FSM shall classify the incoming mesh peerinThe MPM FSM shall classify the incoming mesh peering management frames to decide either to accept, reject,g management frames to decide either to accept, reject, or silently discard the frame. or silently discard the frame.


Mesh peering managementMesh peering management (4) (4)

Mesh Peering Management FramesMesh Peering Management FramesMesh Peering Open framesMesh Peering Open framesMesh Peering Confirm framesMesh Peering Confirm framesMesh Peering Close framesMesh Peering Close frames


Authenticated Mesh Peering ExchanAuthenticated Mesh Peering Exchange (1)ge (1)

The Authenticated Mesh Peering Exchange establishes aThe Authenticated Mesh Peering Exchange establishes an authenticated mesh peering between the mesh STAs, un authenticated mesh peering between the mesh STAs, under the assumption that Mesh PMKSA has already been nder the assumption that Mesh PMKSA has already been established before the initiation of the protocol via the actiestablished before the initiation of the protocol via the active authentication protocol.ve authentication protocol. An authenticated mesh peering includes a mesh peering, correspAn authenticated mesh peering includes a mesh peering, corresp

onding mesh TKSA, and the two mesh STAs mesh GTKSAs.onding mesh TKSA, and the two mesh STAs mesh GTKSAs. The Authenticated Mesh Peering Exchange uses Mesh Peering MThe Authenticated Mesh Peering Exchange uses Mesh Peering M

anagement frames. Parameters are exchanged via RSN informatianagement frames. Parameters are exchanged via RSN information element, Authenticated Mesh Peering Exchange element, and on element, Authenticated Mesh Peering Exchange element, and MIC element.MIC element.

APME – Authenticated Mesh Peering ExchangeAPME – Authenticated Mesh Peering Exchange The major functions provided by AMPE are Security Capability SelectiThe major functions provided by AMPE are Security Capability Selecti

on and Key Management.on and Key Management.



Instance Pairwise Cipher Suite SelectionInstance Pairwise Cipher Suite Selection Pairwise cipher suite selectors WEP-40, WEP-104, and Pairwise cipher suite selectors WEP-40, WEP-104, and

TKIP shall not be used as the pairwise cipher suite wheTKIP shall not be used as the pairwise cipher suite when dot11MeshSecurityActivated is enabled.n dot11MeshSecurityActivated is enabled.

Group Cipher Suite SelectionGroup Cipher Suite Selection The mesh STA shall not use a different group cipher suThe mesh STA shall not use a different group cipher su

ite than the one used by the peer mesh STA or candidaite than the one used by the peer mesh STA or candidate peer mesh STA in the same MBSS.te peer mesh STA in the same MBSS.

In other words, the group cipher suite selection should be the sIn other words, the group cipher suite selection should be the same for every mesh STA in the same MBSS.ame for every mesh STA in the same MBSS.



MGTK DistributionMGTK Distribution The mesh STA shall distribute the MGTK to the peer mThe mesh STA shall distribute the MGTK to the peer m

esh STA using the Mesh Peering Open frame during thesh STA using the Mesh Peering Open frame during the Authenticated Mesh Peering Exchange.e Authenticated Mesh Peering Exchange.

Upon successful completion of AMPE, each mesh STA Upon successful completion of AMPE, each mesh STA shall establish states for the peer mesh STA’s mesh Gshall establish states for the peer mesh STA’s mesh GTKSA.TKSA.



Mesh Peering Management frames for Authenticated MesMesh Peering Management frames for Authenticated Mesh Peering Exchangeh Peering Exchange The Mesh Peering Management frames shall be generated with aThe Mesh Peering Management frames shall be generated with a

dditional information using RSN information element and AMPE indditional information using RSN information element and AMPE information element to support Authenticated Mesh Peering Exchanformation element to support Authenticated Mesh Peering Exchange.ge.

Mesh Peering Open frame contents for Authenticated Mesh Peering EMesh Peering Open frame contents for Authenticated Mesh Peering Exchangexchange

Processing Mesh Peering Open frames for Authenticated Mesh PeeriProcessing Mesh Peering Open frames for Authenticated Mesh Peering Exchangeng Exchange

Mesh Peering Confirm frame content for Authenticated Mesh Peering Mesh Peering Confirm frame content for Authenticated Mesh Peering ExchangeExchange

Processing Mesh Peering Confirm action framesProcessing Mesh Peering Confirm action frames Mesh Peering Close frame content for Authenticated Mesh Peering EMesh Peering Close frame content for Authenticated Mesh Peering E

xchangexchange Processing Mesh Peering Close action framesProcessing Mesh Peering Close action frames


Mesh Group Key HandshakeMesh Group Key Handshake The Mesh Group Key Handshake may be used bThe Mesh Group Key Handshake may be used b

y either mesh STA, after a secure mesh peering hy either mesh STA, after a secure mesh peering has been established, to update the MGTK that it uas been established, to update the MGTK that it uses to protect group addressed MPDUs that it trases to protect group addressed MPDUs that it transmits to its peer mesh STAs.nsmits to its peer mesh STAs. The mesh STA may update its MGTK when a mesh peThe mesh STA may update its MGTK when a mesh pe

ering is terminated.ering is terminated. The Mesh Group Key handshake exchange shall includThe Mesh Group Key handshake exchange shall includ

e two messages:e two messages: Message 1: Mesh Group Key Inform frameMessage 1: Mesh Group Key Inform frame Message 2: Mesh Group Key Acknowledge frameMessage 2: Mesh Group Key Acknowledge frame


MBSS channel switching (1)MBSS channel switching (1) The procedures may also be useful for other purposes. ThThe procedures may also be useful for other purposes. Th

e mesh channel switch may be triggered by the need to ave mesh channel switch may be triggered by the need to avoid interference to a detected radar signal, or to reassign oid interference to a detected radar signal, or to reassign mesh STA channels to ensure the MBSS connectivity.mesh STA channels to ensure the MBSS connectivity. Channel Switch protocolChannel Switch protocol

To resolve conflicts in case more than one mesh STA initiates a chanTo resolve conflicts in case more than one mesh STA initiates a channel switch concurrently, each mesh STA utilizes a Mesh Channel Switnel switch concurrently, each mesh STA utilizes a Mesh Channel Switch Timer and a Current Precedence Value.ch Timer and a Current Precedence Value.

A mesh STA that determines the need to switch the channel shall initiate A mesh STA that determines the need to switch the channel shall initiate a channel switch attempt and transmit a Mesh Channel Switch Announcea channel switch attempt and transmit a Mesh Channel Switch Announcement frame to each of its peer mesh STAs to announce its intent.ment frame to each of its peer mesh STAs to announce its intent.

The Mesh Channel Switch Announcement frame may be transmitted usinThe Mesh Channel Switch Announcement frame may be transmitted using individually or group addressed frames.g individually or group addressed frames.

The mesh STA shall include the Mesh Channel Switch Announcement elThe mesh STA shall include the Mesh Channel Switch Announcement element in its Beacon frames and Probe Response frames during the chanement in its Beacon frames and Probe Response frames during the channel switch process.nel switch process.


MBSS channel switching (2)MBSS channel switching (2) Channel Switch across a regulatory classChannel Switch across a regulatory class

When dot11RegulatoryClassesImplemented is true and When dot11RegulatoryClassesImplemented is true and the mesh STAs is capable of operating in multiple regulthe mesh STAs is capable of operating in multiple regulatory classes, the mesh STA shall include the Supporteatory classes, the mesh STA shall include the Supported Regulatory Classes element within its Mesh Peering d Regulatory Classes element within its Mesh Peering Open frames.Open frames.

The Supported Regulatory Classes element announces the reThe Supported Regulatory Classes element announces the regulatory classes that the mesh STA supports.gulatory classes that the mesh STA supports.


Mesh path selection and forwarding Mesh path selection and forwarding framework (1)framework (1)

““mesh path selection” and “mesh forwarding”mesh path selection” and “mesh forwarding” used to describe selection of single-hop or multi-hop paused to describe selection of single-hop or multi-hop pa

ths and forwarding of data and multihop action frames ths and forwarding of data and multihop action frames across these paths between mesh STAs at the link layacross these paths between mesh STAs at the link layer.er.

A single path selection method is used in an MBSS to determiA single path selection method is used in an MBSS to determine paths.ne paths.

Data messages use four or six addressesData messages use four or six addresses the 6-address format is designed such that an intermediate methe 6-address format is designed such that an intermediate me

sh STA on a mesh path need not maintain forwarding informatish STA on a mesh path need not maintain forwarding information for any IEEE 802 entity outside the MBSS.on for any IEEE 802 entity outside the MBSS.



Extensible path selection frameworkExtensible path selection framework This standard includes an extensible framework to enable flexible This standard includes an extensible framework to enable flexible

implementation of path selection protocols and metrics within the implementation of path selection protocols and metrics within the mesh framework.mesh framework.

The standard includes a default mandatory path selection protocol The standard includes a default mandatory path selection protocol (HWMP) and default mandatory path selection metric (Airtime Link (HWMP) and default mandatory path selection metric (Airtime Link Metric) for all implementations, to ensure interoperability between Metric) for all implementations, to ensure interoperability between mesh STAs.mesh STAs.

A mesh STA may include multiple protocol implementations (that iA mesh STA may include multiple protocol implementations (that is, the default protocol, optional protocols, vendor specific protocols, the default protocol, optional protocols, vendor specific protocols, etc.) as well as multiple metric implementations, but only one pas, etc.) as well as multiple metric implementations, but only one path selection protocol and only one path selection metric shall be uth selection protocol and only one path selection metric shall be used by a mesh STA at a time.sed by a mesh STA at a time.



Path selection metrics and protocolsPath selection metrics and protocols The mesh extensibility framework allows a mesh to be iThe mesh extensibility framework allows a mesh to be i

mplemented with any path selection metric(s) and/or amplemented with any path selection metric(s) and/or any path selection protocol(s).ny path selection protocol(s).

The implemented path selection protocol and path seleThe implemented path selection protocol and path selection metric shall be identified by a unique identifierction metric shall be identified by a unique identifier

Active Path Selection Protocol IdentifierActive Path Selection Protocol Identifier Active Path Selection Metric IdentifierActive Path Selection Metric Identifier

Link metric reportingLink metric reporting Link metric reporting may assist a mesh STA into learniLink metric reporting may assist a mesh STA into learni

ng about the metric of its link to another mesh STA frong about the metric of its link to another mesh STA from the viewpoint of that other mesh STA.m the viewpoint of that other mesh STA.


Link Metric ExampleLink Metric Example


Addressing for Data ForwardingAddressing for Data Forwarding

6-Address scheme6-Address scheme


Addressing –Example 1Addressing –Example 1


Addressing –Example 2Addressing –Example 2



Mesh Data frames and Multihop Action frames are designed to suppoMesh Data frames and Multihop Action frames are designed to support multi-hop frame forwarding in an MBSS using the Mesh Control fielrt multi-hop frame forwarding in an MBSS using the Mesh Control field.d.



Example Addressing for a Mesh Data frame transmitted aExample Addressing for a Mesh Data frame transmitted and forwarded on a mesh path from an mesh AP to a portalnd forwarded on a mesh path from an mesh AP to a portal



Addressing and Forwarding of Individually Addressing and Forwarding of Individually Addressed FramesAddressed FramesAt Source mesh STAs (1)At Source mesh STAs (1)

Frames that originate at a mesh STA and are intendFrames that originate at a mesh STA and are intended for another mesh STA in the MBSS shall be traned for another mesh STA in the MBSS shall be transmitted using the 4-address formatsmitted using the 4-address format

Address 1: The address of the next-hop mesh STA (towarAddress 1: The address of the next-hop mesh STA (toward the Destination mesh STA according to the forwarding ind the Destination mesh STA according to the forwarding informationformation

Address 2: The address of the Transmitter mesh STAAddress 2: The address of the Transmitter mesh STA Address 3: The address of the Destination mesh STAAddress 3: The address of the Destination mesh STA Address 4: The address of the Source mesh STAAddress 4: The address of the Source mesh STA



Addressing and Forwarding of Individually Addressed FraAddressing and Forwarding of Individually Addressed Framesmes At Source mesh STAs (2)At Source mesh STAs (2)

Frames that do not originate or are not intended for another mesh STFrames that do not originate or are not intended for another mesh STA in the MBSS shall be transmitted using the 6-address formatA in the MBSS shall be transmitted using the 6-address format

Address 1: The address of the next-hop mesh STA (toward the destinatioAddress 1: The address of the next-hop mesh STA (toward the destination mesh STA according to forwarding informationn mesh STA according to forwarding information

Address 2: The address of the Transmitter mesh STAAddress 2: The address of the Transmitter mesh STA Address 3: The address of the destination mesh STA at the end of the meAddress 3: The address of the destination mesh STA at the end of the me

sh pathsh path Address 4: The address of the source mesh STA at the beginning of the Address 4: The address of the source mesh STA at the beginning of the

mesh pathmesh path Address 5: The address of the destination end point (may be the same as Address 5: The address of the destination end point (may be the same as

Address 3 if the destination is the mesh STA at the end of the mesh path)Address 3 if the destination is the mesh STA at the end of the mesh path) Address 6: The address of the source end point (may be the same as AdAddress 6: The address of the source end point (may be the same as Ad

dress 4 if the source is the mesh STA at the beginning of the mesh path)dress 4 if the source is the mesh STA at the beginning of the mesh path)


InterworkingInterworking (1) (1) Overview of interworking in a mesh BSSOverview of interworking in a mesh BSS

An MBSS functions like an IEEE 802 LAN segment thaAn MBSS functions like an IEEE 802 LAN segment that is compatible with IEEE 802.1D.t is compatible with IEEE 802.1D.

The MBSS appears as a single access domain.The MBSS appears as a single access domain. An MBSS may have zero or more portals that may be connectAn MBSS may have zero or more portals that may be connect

ed to one or more LAN segments.ed to one or more LAN segments. In case two portals connect the MBSS to one external LAN seIn case two portals connect the MBSS to one external LAN se

gment, broadcast loops may occur and the IEEE 802.1D bridgigment, broadcast loops may occur and the IEEE 802.1D bridging protocol may cause the LAN ports of one of the portals to bng protocol may cause the LAN ports of one of the portals to be closed.e closed.

These cases can be prevented by proper configuration measuresThese cases can be prevented by proper configuration measures


InterworkingInterworking (2) (2) Portal announcement protocolPortal announcement protocol

The Portal Announcement (PANN) element is used to announce tThe Portal Announcement (PANN) element is used to announce the presence of a mesh STA collocated with a portal in the mesh Bhe presence of a mesh STA collocated with a portal in the mesh BSS.SS.

Portal Announcements allow mesh STAs to select the appropriate porPortal Announcements allow mesh STAs to select the appropriate portal and build a path towards it.tal and build a path towards it.

2 Conditions for generating and sending a PANN2 Conditions for generating and sending a PANN Case A: Original transmissionCase A: Original transmission

All of the following applies:All of the following applies: The mesh STA is collocated with portalThe mesh STA is collocated with portal dot11MeshPortalAnnouncementProtocol is set to TRUEdot11MeshPortalAnnouncementProtocol is set to TRUE At every dot11MeshPortalAnnouncementIntervalAt every dot11MeshPortalAnnouncementInterval

Case B: PropagationCase B: Propagation All of the following applies:All of the following applies:

The mesh STA has received a Portal AnnouncementThe mesh STA has received a Portal Announcement The decremented time to live of the Portal Announcement is equal tThe decremented time to live of the Portal Announcement is equal t

o or greater than 1o or greater than 1 dot11MeshForwarding is set to TRUEdot11MeshForwarding is set to TRUE


InterworkingInterworking (3) (3) Mesh portal data forwarding behavior (1)Mesh portal data forwarding behavior (1)

Mesh portals can learn the addresses of the mesh STAs and of deMesh portals can learn the addresses of the mesh STAs and of devices attached to these mesh STAs through the receipt of path selvices attached to these mesh STAs through the receipt of path selection messages and messages carrying proxy information.ection messages and messages carrying proxy information.

Handling of frames that originated in the MBSSHandling of frames that originated in the MBSS A mesh STA address or a proxied address that the mesh portal knows is A mesh STA address or a proxied address that the mesh portal knows is

reachable through the MBSS:reachable through the MBSS: The mesh portal forwards the frame to the destination mesh STA.The mesh portal forwards the frame to the destination mesh STA.

An address that the mesh portal knows is outside the MBSS:An address that the mesh portal knows is outside the MBSS: The mesh portal forwards the frame on the external network.The mesh portal forwards the frame on the external network.

A group address:A group address: The mesh portal forwards the frame on the external network as a grThe mesh portal forwards the frame on the external network as a gr

oup addressed frame.oup addressed frame. An address unknown to the mesh portal:An address unknown to the mesh portal:

The mesh portal forwards the frame on the external network.The mesh portal forwards the frame on the external network.


InterworkingInterworking (4) (4) Mesh portal data forwarding behavior (2)Mesh portal data forwarding behavior (2)

Handling of frames that enter the MBSSHandling of frames that enter the MBSS A mesh STA address or proxied address that the mesh portal A mesh STA address or proxied address that the mesh portal

knows is inside the MBSS:knows is inside the MBSS: The mesh portal forwards the frame to the destination mesh STA.The mesh portal forwards the frame to the destination mesh STA.

A group address:A group address: Transmit the frame within the MBSS using the forwarding procedTransmit the frame within the MBSS using the forwarding proced

ure for group addressed framesure for group addressed frames An address that is unknown to the mesh portal:An address that is unknown to the mesh portal:

The mesh portal has two options:The mesh portal has two options: Attempt to establish a path to the destination for subsequent Attempt to establish a path to the destination for subsequent

deliverydelivery Transmit the frame within the MBSS using the forwarding proTransmit the frame within the MBSS using the forwarding pro

cedure for group addressed framescedure for group addressed frames


Airtime link metricAirtime link metric Airtime reflects the amount of channel resources Airtime reflects the amount of channel resources

consumed by transmitting the frame over a particconsumed by transmitting the frame over a particular link.ular link. A default link metric that may be used by a path selectiA default link metric that may be used by a path selecti

on protocol to identify an efficient radio-aware path.on protocol to identify an efficient radio-aware path. The extensibility framework allows this metric to be oveThe extensibility framework allows this metric to be ove

rridden by any path selection metric as specified in the rridden by any path selection metric as specified in the mesh profile.mesh profile.


HWMPHWMP (1) (1) Hybrid Wireless Mesh ProtocolHybrid Wireless Mesh Protocol

A mesh path selection protocol that combines the flexibA mesh path selection protocol that combines the flexibility of on-demand path selection with proactive topologility of on-demand path selection with proactive topology tree extensions.y tree extensions.

The combination of The combination of reactive and and proactive elements of HWMP elements of HWMP enables efficient path selection in a wide variety of mesh netwenables efficient path selection in a wide variety of mesh networks.orks.

HWMP uses a common set of protocol primitives, generation aHWMP uses a common set of protocol primitives, generation and processing rules inspired by Ad Hoc On Demand Distance nd processing rules inspired by Ad Hoc On Demand Distance Vector (AODV) protocol adapted for MAC address-based path Vector (AODV) protocol adapted for MAC address-based path selection and link metric awareness.selection and link metric awareness.

IETF RFC 3561IETF RFC 3561 HWMP supports two modes of operation depending on the coHWMP supports two modes of operation depending on the co

nfiguration.nfiguration. On demand modeOn demand mode Proactive tree building modeProactive tree building mode


HWMPHWMP (2) (2)


HWMP (3)HWMP (3)

On-demand route discoveryOn-demand route discoveryUsed in intra-mesh routing for routing optimizatUsed in intra-mesh routing for routing optimizat

ionsionsRadio Metric AODV (RM-AODV)Radio Metric AODV (RM-AODV)

RFC 3561RFC 3561

Proactive routingProactive routingUsed when a root portal (MPP) is presentUsed when a root portal (MPP) is presentTree-based routingTree-based routing


HWMP – On-demandHWMP – On-demand Main idea (very similar to AODV)Main idea (very similar to AODV)

Route discoveryRoute discovery Reverse paths set up by pathrequests(broadcast/unicast)Reverse paths set up by pathrequests(broadcast/unicast)

Path repliesare sent unicast by destination or the interPath repliesare sent unicast by destination or the intermediate nodesmediate nodes

Loop freedomLoop freedom Supported by using a destination sequence numberSupported by using a destination sequence number

Route maintainenceRoute maintainence When a link error is detected, a route error is sent by unicastWhen a link error is detected, a route error is sent by unicast Route errors are rate-controlledRoute errors are rate-controlled


HWMP – Tree-based routingHWMP – Tree-based routing Proactive RREQ mechanismProactive RREQ mechanism

Root issues a broadcast RREQ (Route request)Root issues a broadcast RREQ (Route request) MPs may respond with unicast RREP (Route reply)MPs may respond with unicast RREP (Route reply) 2-way handshaking2-way handshaking

Proactive RANN mechanismProactive RANN mechanism Root issues a broadcast Root announcementRoot issues a broadcast Root announcement MP responds with a RREQMP responds with a RREQ Root responds with a RREPRoot responds with a RREP 3-way handshaking3-way handshaking


Proactive RREQ MechanismProactive RREQ Mechanism The root MP periodically propagatThe root MP periodically propagat

es a PREQ into the networkes a PREQ into the network Destination address set to all 1sDestination address set to all 1s TO=1 and RF=1TO=1 and RF=1

Upon reception of a PREQ, each Upon reception of a PREQ, each MP has to create or refresh a path MP has to create or refresh a path to the root MPto the root MP ““Proactive PREP”= 0, MP may seProactive PREP”= 0, MP may se

nd a proactive PREP if requirednd a proactive PREP if required ““Proactive PREP” =1, MP shall seProactive PREP” =1, MP shall se

nd a proactive PREPnd a proactive PREP


HWMP –Tree-based routingHWMP –Tree-based routing Tree maintainenceTree maintainence

MPPs monitor the root and take oMPPs monitor the root and take over if the root fails (Root arbitratiover if the root fails (Root arbitration)n)

MPs monitor upstream links and MPs monitor upstream links and may switch to back up linksmay switch to back up links

3-1 →3-2-13-1 →3-2-1 RERRs sent for failing linksRERRs sent for failing links

Downstream nodesDownstream nodes May select their own back up patMay select their own back up pat

hshs AODV path holdersAODV path holders


HWMP – Example 1HWMP – Example 1 On-demand path setup On-demand path setup

to inside of the meshto inside of the mesh MP4 –MP9MP4 –MP9

MP4 sends a RREQMP4 sends a RREQ MP9 sends back a RREMP9 sends back a RRE

PP


HWMP – Example 2HWMP – Example 2 On-demand set up tOn-demand set up t

o outside mesho outside mesh MP4 –XMP4 –X

MP4 does not have MP4 does not have a routea route

Broadcasts a RREQBroadcasts a RREQ MP4 does not receivMP4 does not receiv

e a responsee a response MP4 directs messageMP4 directs message

s for X to MP1s for X to MP1 MP1 sends to XMP1 sends to X


HWMP – Example 3HWMP – Example 3 Routing through root tRouting through root t

o outside of mesho outside of mesh MP4-XMP4-X

MP4 learns MP1 via RMP4 learns MP1 via Root announcement meoot announcement messagesssages

MP4 sends to MP1MP4 sends to MP1 MP1 sends to XMP1 sends to X


HWMP – Example 4HWMP – Example 4 Routing through root to insiRouting through root to insi

de of the meshde of the mesh MP4 →MP9MP4 →MP9

MP4 sends to MP1MP4 sends to MP1 MP1 knows MP9 is inside the MP1 knows MP9 is inside the

meshmesh Forwards to MP9Forwards to MP9

MP9 may send a RREQ to MMP9 may send a RREQ to MP4 to discover a shorter pathP4 to discover a shorter path2929

Reference: Routing Reference: Routing


AP a

AP b

AP c

AP f

AP d

AP e

APa has a packet to transmit to APf

Ongoingcommunication

““SMART”: an exampleSMART”: an example

Even if the primary selected path to

reach the destination is goes

trough APb, APa will choose an

alternative path transmitting the packet to APd

Documents

IEEE 802.11 無線區域網路系統及通訊協定 林文宗博士 現任：明新科技大學資訊工程系助理教授 明新科技大學電算中心網路組組長 經歷：工研院資通所無線通訊技術組顧問

IEEE 802.11 無線區域網路系統及通訊協定林文宗博士現任：明新科技大學資訊工程系助理教授明新科技大學電算中心網路組組長經歷：工研院資通所無線通訊技術組顧問