Wireless Networking

04 September 2004Quintin Krisp

OverviewWireless LAN ApplicationsWireless LAN TechnologyIEEE 802.11 StandardIEEE 802.11 Protocol ArchitectureIEEE 802.11 RelativesWi-Fi Security

Wireless LAN ApplicationsLAN Extension:Buildings with large open areas (e.g. Manufacturing plants, Warehouses)Historical buildings: may not damage buildingSmall offices: wired LANs not economicalMay be mixed with fixed wiring system (hence LAN extension)Either a single-cell or multiple-cell wireless LANCross-building interconnection:Point-to-point wireless link between buildings (e.g. Rural Monash Campuses)Typically connecting bridges or routersUsed where cable connection not possible (e.g. across a street)

Single Cell Wireless LANControl module (CM) and User Module (UM).

Multi-Cell Wireless LAN

Wireless LAN ApplicationsNomadic access:Between a LAN hub and mobile data terminal (e.g. laptop)Transfer of data from laptop to serverCampus or cluster of buildings

Ad hoc networks:Peer-to-peer (no centralized server)Temporary connection (e.g. conference)

a) Infrastructure Wireless LANb) Ad hoc LAN

Wireless LAN TechnologyInfrared (IR) LANs:Individual cell of IR LAN limited to single roomIR light does not penetrate opaque wallsMore immune to electromagnetic interference (radio transmission or microwave ovens)No licenses requiredSpread spectrum LANs:Mostly operate in ISM (industrial, scientific, and medical) bandsNo Federal Communications Commission (FCC) licensing is required in USANarrowband microwave:Microwave frequencies but not use spread spectrumSome require FCC licensing

Electromagnetic Spectrum for Telecommunications

802.11 StandardIEEE 802 committee began in 1987 within the IEEE 802.4 group

Initial interest developing ISM-based wireless LAN using equivalent of token-passing bus MAC protocol

Token bus not suitable for radio medium, caused inefficient use of the radio frequency spectrum

IEEE 802.11 formed in 1990 as new working group devoted specifically to wireless LANs

802.11 Protocol ArchitectureDistributed Coordination Function DFCLower MAC sublayer, uses Ethernet contention algorithm to provide access to all trafficContention protocol designed to handle two or more stations accessing network traffic simultaneouslyPoint Coordination Function (PCF)Centralized MAC algorithm to provide contention-free serviceAP polls according to list, no collisions occurLogical Link Control (LLC)Provide an interface to higher layersPerforms basic link-layer functions such as error control

802.11 Protocol Architecture

802.11 Relatives802.11d: Modification to comply with other countries802.11e: Add Quality of Service (QOS)802.11f: Improve communication between APs for authentication802.11h: Modification to comply with Europe802.11i: Improve WLAN security802.11j: Modification to comply with Japan802.11k: Provide measurement info of APs802.11m: Minor Mods to previous Pubs

802.11 Relatives802.11n: Increase WLAN raw throughput802.11p: Utilize 5.9 GHz band for Intelligent Transportation System802.11o: Faster handoff, prioritize voice traffic over data802.11q: Frame tagging for VLAN segregation802.11r: Standardize fast-hand-off802.11s: Self-healing/self-configuring Mesh networks802.11t: Performance prediction

802.11 Relatives802.11d: New CountriesWhere 802.11 family not allowed to operateSpecification similar to 802.11bMain difference, configuration fine-tuned at MAC level to comply with rules of country or district network to operateRules subject to variation include allowed: frequencies, power levels, and signal bandwidth

802.11 Relatives802.11e: Quality of Service (QOS)Goal: Develop QOS technology to help Wi-Fi networks avoid problems when transmitting time-sensitive data like voice and videoOne 802.11e innovation starting to be used: frame bursting or packet burningImproves ratio of data-to-network overhead by sending larger amounts of data in individual framesCan only speed up mixed 802.11b/802.11g networksInitial improvement better if all equipment from same manufacturer

802.11 Relatives802.11f: Inter-Access Point CommunicationCommunication between Wi-Fi APs a problem depending on manufactureAPs will be able to offer fast handoffEliminates break in service when roamingSome features tie with 802.11i security standard802.11h: Compatibility with European RegsSupplementary to MAC layer, comply w/5Ghz WLANsRequire transmission power control (TPC), limits minimum power required to reach furthest userRequire dynamic frequency selection (DFS), selects radio channel at AP to minimize interference with other systems

802.11 Relatives802.11i: Security SpecificationsReplaces wired equivalent privacy (WEP) encryption with temporal key integrity protocol (TKIP)Supplement TKIP with advanced encryption system (AES)Adds pre-authentication, enables user logged into a corporate-style network connected roaming capability while maintaining connectionRelies on inter-access point communication provided by 802.11f

802.11 Relatives802.11j: 5 GHz Operations in JapanMain intent, add channels in the RF band of 4.9 GHz to 5 GHzImplement changes to satisfy Japanese legal requirements concerning: transmitter output power, operational modes, channel arrangements, and spurious emission levelsLike 802.11a networksProvide speeds up to 54 MbpsEmploy OFDM Transfer Method

802.11 Relatives802.11k: Radio Resource Management Address lack of standard for managing WLANs Focuses on two key elements: AP and PC cardsGoal: make measurements from physical and data link layers available to upper layersAllow upper layers to make decisions about the radio environment and what can be accomplished in that environmentOne feature allow better traffic distribution, produce higher speed for the original AP and redirected users

802.11 Relatives802.11m: 802.11 HousekeepingPerform editorial maintenance, corrections, improvements, clarifications, and interpretations, relative to 802.11 family specification documentation 802.11n: Inter-access Point CommunicationsObjective: increase overall and throughput speed of future 802.11 protocolsReal speed 100 Mbps250 Mbps in PHY level4-5 times faster than 802.11g50 times faster than 802.11bBetter operating distance

802.11 Relatives802.11o: Vo Wi-Fi Faster HandoffA proposed IEEE group to beSpun out of the 802.11i groupFocus for standard for a fast handoff that is fully secure and compatible with 802.11i and Wi-Fi Protected Access (WPA)Current supported roaming causes brief break in data stream802.11i implementation will exacerbate the situationHandover time (70 milliseconds) make voice calls impossible

802.11 Relatives802.11p: Intelligent Transportation SystemEstablished for wireless access in vehicular environments (WAVE)Dedicated short range communications (DRC) is a general purpose communications link between the vehicle and roadside (or between vehicles) using 802.11p protocolProtocols just months oldImproves on dedicated 5.9 GHz range (1,000 ft.) and transmission speed (6 Mbps)Protocol aimed at vehicles: toll collection, vehicle safety, commerce transactions via carsGovernment pushing forward to cover highways with APs that support this new type of extra-secure hotspots that ride over 5.9 GHzManufactures expect to install chips, initially in high-end vehicles, in 2007 or 2008 time frame

802.11 Relatives802.11q: VLAN ManagementDefines mechanisms for tagging frames, allow them to be segregated into separate VLANs VLANs extend into WLAN by adding 802.11q awareness to the APFrames destined for different VLANs are transmitted by the AP wirelessly on different SSIDs with different WEP keysOnly the client associated with the VLAN receives those packetsConversely, packets coming from a client associated with a certain VLAN are tagged with 802.11q before they are forwarded into the wired network

802.11 Relatives802.11r: Fast BSS TransitionRecently founded to address fast roaming among APsSome experts think technology emerging from 802.11i and 802.11k will render 802.11r group unnecessaryGroup still defining scope and does not have a draft yet

802.11 Relatives802.11s: ESS Mesh NetworkingAims to define a MAC and PHY for mesh networksImprove coverage with no single point of failureAPs relay information hop-by-hop, router like fashionAdding nodes, scalable and redunantCan serve as indoor or outdoor networksExample: Municipalities extend fiber networks or all outdoor enterprises such as construction sites 802.11t: Wireless Performance PredictionEnable testing, comparison, and deployment planning of 802.11 WLAN devicesBased on common accepted set of performance metrics, measurement methodologies and test conditions

Wi-Fi SecurityRobust Security Network (RSN)Defined by 802.11i specificationReplaces wired equivalent privacy (WEP)Backward compatible support of Wi-Fi protected access (WPA) based on temporal key integrity protocol (TKIP)Uses advanced encryption system (AES) in addition to TKIPAES method combines a key and a 128-bit block of unencrypted data to produce a block of different encrypted data.WEP only uses 40-bit key

Wi-Fi Security802.11i Standard Acceptance ImpactBusiness community interest expected to skyrocket in next year or twoVendors already rolling out firmware enabling 802.11 compliant security protocolsImmediate impact by eliminating VPN infrastructure except when connected remotely, such as a hotelPerformance penalty for 802.11i functionality unknown

SummaryWireless LAN ApplicationsWireless LAN TechnologyIEEE 802.11 StandardIEEE 802.11 Protocol ArchitectureIEEE 802.11 RelativesWi-Fi Security