802.11s Tutorial r5 - IEEE 802

1 November 2006 Slide 1 ieee TutorialIEEE TutorialOverview of the Amendment forWireless Local Area MeshNetworkingW. Steven Conner, Intel Kruys, Cisco SystemsKyeongsoo (Joseph) Kim, STMicroelectronicsJuan Carlos Zuniga, InterDigital Comm. 802 Plenary, DallasMonday, Nov 13, 2006, 6:30 PM November 2006 Slide 2 ieee TutorialKey Contributors Donald E. Eastlake 3rd, Motorola Susan Hares, NextHop Guido Hiertz, Philips Meiyuan Zhao, IntelNovember 2006 Slide 3 ieee TutorialAbstract Network communications with end devices is increasingly wireless. Many standards for wireless networking are now taking the next step to support mesh architectures in which data is commonly forwarded on paths consisting of multiple wireless hops . This Tutorial will explore the amendment being developed to add mesh capabilities to the wireless local area networking (WLAN) 2006 Slide 4 ieee TutorialOutline Part 1, W.

2 Steven Conner Overview Extensible Framework Part 2, Jan Kruys Security Routing Part 3, Joseph Kim Interworking Data Frame Format and 6 Address Scheme Part 4, Juan Carlos Zuniga MAC Enhancements Beaconing, Synchronization, and PowersaveNovember 2006 Slide 5 ieee TutorialPart 1: OverviewW. Steven Conner, Intel Corp. Overview Extensible FrameworkNovember 2006 Slide 6 ieee TutorialWhy, What, How?November 2006 Slide 7 ieee TutorialClassic WLAN= radio linkBSS = Basic Service SetAPSTASTASTASTASTASTASTASTAESS = Extended Service Set SSIDAPAPAPW ired InfrastructureWireless Paradox: WLAN Access Points are Typically WiredNovember 2006 Slide 8 ieee TutorialUnwire the WLAN with MeshMeshAPSTASTASTASTASTASTASTASTAW ired Infrastructure= mesh radiolinkESS = Extended Service Set SSIDMeshAPMeshPointMeshAPMeshAPNovember 2006 Slide 9 ieee TutorialWhy Mesh?

3 What s so good about Mesh? Enables rapid deployment with lower-cost backhaul Easy to provide coverage in hard-to-wire areas Self-healing, resilient, extensible Under the right circumstances: Greater range due to multi-hop forwarding Higher bandwidth due to shorter hops Better battery life due to lower power transmissionNovember 2006 Slide 10 ieee TutorialWhat is ieee is an amendment being developed to the ieee WLAN (Wireless Local Area Networks) standard. The current standard is ieee plus the following ratified amendments (available for download from ): , , , MAC Quality of Service Enhancements , Spectrum and Transmit Power Management Extensions in the 5 GHz band in Europe , MAC Security Enhancements , GHz 5 GHz Operation in JapanNovember 2006 Slide 11 ieee Scope WLAN Mesh Networking Integrates mesh networking services and protocols with at the MAC Layer Primary Scope.

4 Amendment to ieee to create a Wireless Distribution System with automatic topology learning and wireless path configuration Small/medium mesh networks (~32 forwarding nodes) can be larger Dynamic, radio-awarepath selection in the mesh, enabling data delivery on single-hop and multi-hop paths (unicast and broadcast/multicast) Extensible to allow support for diverse applications and future innovation Use security or an extension thereof Compatible with higher layer protocols (broadcast LAN metaphor)November 2006 Slide 12 ieee Scope (cont.)No Redesign of Existing PHY(.11a/b/g/n) is an amendment to the MACN ovember 2006 Slide 13 ieee TutorialStructure of the WG Active Task Groups in the Wireless Local Area Network Working Group, : , TGk, Radio Resources Measurement , TGm, Maintenance , TGn, High Throughput , TGp, Wireless Access in the Vehicle Environment , TGr, Fast Roaming , TGs, Mesh Networking , TGT, Wireless Performance Prediction , TGu, Interworking with External Networks , TGv, Wireless Network Management , TGw, Protected Management Frames , TGy, 3850-3700 MHz Operation in the USAN ovember 2006 Slide 14 ieee Standardization Progress and StatusNovember 2006 Slide 15 ieee TutorialCall for Call for ProposalsProposalsIEEE Timeline January 04: Formation of Mesh Study Group July 04.

5 First TGs Meeting January 05: Call for Proposals Issued July 05: Mandatory Proposal Presentations March 06: First Draft Spec AdoptedLetter Ballot TargetLetter Ballot TargetNov 06 Nov 062H 20052H 20061H 20061H 20071H 20052H 2007 Mandatory Proposal Mandatory Proposal PresentationsPresentationsDownselectionD ownselectionand mergersand ratified ratified 1H 081H 08 Timeline:Timeline:Joint SEE-Mesh/Wi-MeshProposal Confirmed (Mar 06)1H 2008 CommentCommentresolutionresolutionSponso rSponsorBallot Ballot TargetTargetNote: future projected dates based on official TGs timelineNovember 2006 Slide 16 ieee TutorialProposal Evaluation Basis Mandatory conformance documents 11-04/54r2 PAR for ieee ESS Mesh 11-04/56r1 Five Criteria for ieee ESS Mesh Evaluation documents 11-04/1174r13 Functional Requirements and Scope 11-04/1175r10 Comparison Categories and Informative Checklists 11-04/662r16 Usage Models 11-04/1477r4 Terms and Definitions for Informational documents 11-04/968r13 Issues for Mesh Media Access Coordination Component in 11s 11-04/981r1 TGs Reference Architecture Considerations 11-04/1462r0 Routing and Rbridges 11-04/1543r4 Informative Reference Bibliography for 11-04/662r16 Usage Models November 2006 Slide 17 ieee TutorialExample Mesh Networking Deployment

6 Expected to be Used Across Many Diverse Usage Expected to be Used Across Many Diverse Usage ModelsResidentialOfficeCampus/Public Access Public Safety/MilitaryNovember 2006 Slide 18 ieee Topology, Discovery, and Extensible FrameworkNovember 2006 Slide 19 ieee TutorialDevice Classes in a WLAN Mesh Network Mesh Point (MP): establishes peer links with MP neighbors, full participant in WLAN Mesh services Light Weight MP participates only in 1-hop communication with immediate neighbors (routing=NULL) Mesh AP (MAP): functionality of a MP, collocated with AP which provides BSS services to support communication with STAs Mesh Portal (MPP): point at which MSDUs exit and enter a WLAN Mesh (relies on higher layer bridging functions) Station (STA): outside of the WLAN Mesh, connected via Mesh APPortalMPSTAE xternal NetworkMPAPMPAPSTAMPSTASTAMesh PointMesh PortalMesh APStationNovember 2006 Slide 20 ieee TutorialMesh Points / Mesh StationsMesh PointsAccess PointsMesh Access PointsSet diagram of terms:November 2006 Slide 21 ieee TutorialTopology Formation.

7 Membership in a WLAN Mesh Network Mesh Points (MPs) discover candidate neighbors based on new IEs in beacons and probe response frames WLAN Mesh Capability Element Summary of active protocol/metric Channel coalescence mode and Channel precedence indicators Mesh ID Name of the mesh Mesh Services are supported by new IEs (in action frames), exchanged between MP neighbors Membership in a WLAN Mesh Network is determined by secure peer links with neighbors November 2006 Slide 22 ieee TutorialTopology Formation: Support for Single & Multi-Channel Meshes Each Mesh Point may have one or more logical radio interface: Each logical interface on one (infrequently changing) RF channel, belongs to one Unified Channel Graph Each Unified Channel Graph shares a channel precedence value Channel precedence indicator used to coalesce disjoint graphs and support channel switching for DFSE xample Unified Channel GraphsNovember 2006 Slide 23 ieee TutorialExtensible Framework Support for Mandatory and Alternative Path Selection Protocols Draft defines one mandatory protocol and metric Any vendor may implement any protocol and/or metricwithin the framework A particular mesh will have only one active protocol Only one protocol/metric will be active on a particular link at a time Mesh Points use the WLAN Mesh Capability IE to indicate which protocol is in use A mesh that is using other than mandatory protocol is not required to change its protocol when a new MP joins

8 Algorithm to coordinate such a reconfiguration is out of scopeNovember 2006 Slide 24 ieee TutorialExample: Enabling Extensible Protocol and Metric Implementation5712643 Mesh Identifier:WLANMesh_HomeMesh Profile:(link state, airtime metric)XCapabilities:Path Selection: distance vector, link stateMetrics: airtime, latency1. Mesh Point X discovers Mesh (WLANMesh_Home) with Profile (link state, airtime metric)2. Mesh Point Xestablishes peer link / authenticates with neighbors in the mesh, since it is capable of supporting the Profile3. Mesh Point Xbegins participating in link state path selection and data forwarding protocolOne active protocol/metric in one mesh, but allow for alternative protocols/ metrics in different meshes8 November 2006 Slide 25 ieee TutorialPart 2: Security and RoutingJan Kruys, Cisco Systems Security Path Selection and ForwardingNovember 2006 Slide 26 ieee Security Objectives Scope Role Negotiation Authentication Key ManagementNovember 2006 Slide 27 ieee Tutorial11s Security Situation The MPs are no longer wired to one another There is no intrinsic node hierarchy MPs need to maintain secure links with many other MPsMP7MP1MP6MP2MP3MP4MP5 Wired backhaulSecure candidate linkUnsecure non-candidate linkNovember 2006 Slide 28 ieee TutorialMesh Security Considerations Functions in the scope Transport(Access point covered by 11i)

9 Functions out of the scope Internal routing External routing Forwarding Rationale Current technology is not mature enough to address all vulnerabilities from routing and forwarding There are still research questionsNovember 2006 Slide 29 ieee TutorialTransport Security Prevent unauthorized devices from directly sending and receiving traffic via the mesh Protect unicast traffic between neighbor MPs Protect broadcast traffic between neighbor MPs We need Mutually authenticate neighbor MPs Generate and manage session keys and broadcast keys Data confidentiality over a link Detect message forgeries and replays received on a linkNovember 2006 Slide 30 ieee TutorialAuthentication and Initial Key Management Basic approach is to re-use Re-use of facilitates implementation Allows other AKM schemes is widely used and is suitable for many mesh scenarios but can be replaced with small scale alternatives if required Provides a basis for secure key distribution (PMK) In a mesh, PMK is treated as token of authorization for a MP to join the mesh Authorized to send and receive messages to/from mesh neighborsNovember 2006 Slide 31 ieee TutorialDiscovery and Role Negotiation Discovery Discover the available mesh for joining What Authenticated Key Management (AKM) Protocol, Unicast and Multicast Ciphersuites are available?

10 Negotiation Enable parties to agree on the security roles and security policy to use with a peer link Who s the authenticator, who s the supplicant? Agree on which of those options enabled to useNovember 2006 Slide 32 ieee TutorialRole NegotiationAS reachableAS unreachableAuthenticatorSupplicantAS reachableAS reachableAuthenticatorSupplicantHigher MAC addressNovember 2006 Slide 33 ieee TutorialKey Management GoalsGiven a good PMK Guarantee fresh session key Demonstrate liveness of peer PMK holder Bind session key to the communicating MPs Synchronize session key use Distribute the Group Keys Both party needs to distribute its group key for broadcast/multicast protectionNovember 2006 Slide 34 ieee TutorialTGs Security: initial contactData protectionAuthentication4 way handshake (PTK/GTK distribution)PMK distributionLink state and security capabilities discoveryAuthentication ServerAuthenticatorSupplicantPeer link establishment, Security and Role negotiationNovember 2006 Slide 35 ieee TutorialTGs Security subsequent contact(new feature under discussion)Data protection4 way handshake (PTK/GTK distribution)Authentication ServerAuthenticatorSupplicant nRobust Peer link es