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    • Performance Monitoring Interface for the 802.11b Networks Yusun Chang Akshay Dayal Robert Liu CS6255 Project Background Presentation
    • Contents
      • I. Introduction
      • II. 802.11b Protocol Operation
      • III. System Overview & Design
      • IV. Existing Tool Support
      • V. Future Works
    • Introduction
      • Goal of the Project
        • Design and implementation of an NMS
        • Monitoring IEEE 802.11b AP & local user
        • Performing effective management job
      NMS 802.11b Access Point
      • Wireless environment
        • Power Loss
        • Long Propagation Delay
        • Fading
        • Interference
        • Random & Burst Errors
      Introduction(cont’d) Transmitters Receivers Signal Processing Packet Scheduler User Receiver User Signal Multiplexer time Signal strength Signal strength time
    • Wireless Communication Packet based Wireless LANs 802.11 HiperLAN/2 Bluetooth Cellular circuit based CDMA IS-95 (2.5G) CDMA-2000 (3G) UMTS (3G) WCDMA (3G) GSM GPRS (2.5G) EDGE (3G )
        • Large coverage area
        • Users are actually mobile
        • Low data rates
        • Limited coverage area
        • No mobility support
        • High data rates
      Introduction(cont’d)
    • Contents
      • I. Introduction
      • II. 802.11b Protocol Operation
      • III. System Overview & Design
      • IV. Existing Tool Support
      • V. Future Works
      • Physical layer Radio
        • DSSS(Direct Sequence Spread spectrum)
          • Most frequently used radio
          • Data rate
          • - 1Mbps/DBPSK(Differential Binary Phase Shift Keying)
          • - 2Mbps/QDBPSK
          • - 5.5Mbps, 11Mbps/ CCK (Complementary Code Keying)
          • 2.4GHz ISM Band
        • FHSS(Frequency Hoping Spread Spectrum)
        • IR(Infra Red)
      802.11b Protocol operation(Physical Layer)
      • The PCF Protocol
        • AP polls mobile stations one after another by sending polling message
          • Slot time: signal propagation and processing delay (20 s)
          • SIFS (10 s) : the shortest interval
          • PIFS (30 s) : 1 SIFS + slot time
      802.11b Protocol operation(MAC) [4]
      • The DCF Protocol
        • Employs the CSMA/CA mechanism for contention based access
          • SIFS (10 s)
          • DIFS (50 s) : 1 SIFS + 2 slot times
          • Access mechanism
          • - Select time slot(CW:Contention Window) randomly [0~31]
          • - Decrement when medium is idle more than DIFS
          • - When CW expires, access the channel
          • - If medium is busy, back off CW exponentially
      802.11b Protocol operation(MAC) [4]
    • RTS/CTS/DATA/ACK and NAV[4] 802.11b Protocol operation(MAC) Frozen CW in DCF Initial attempt Previous frame DIFS 31 slots time 1 st retransmission Previous frame DIFS 63 slots time 6 th retransmission Previous frame DIFS time 1023 slots DSSS CW size 0 10 10 10 15 B 13 23 Busy 0 5 A 10 Slot times Next Stage TX/ RX 5 slot times Initial Slots Station
      • I. Introduction
      • II. 802.11b Protocol Operation
      • III. System Overview & Design
      • IV. Existing Tool Support
      • V. Future Works
    • System Overview Maximize Throughput Minimize Power Usage Minimize Packet Loss
    • Packet Loss
      • Packet Errors
      • Packet Collisions
      • Obstructions
      • Interference
      • Low signal strength for distance
    • Packet Loss
      • Packet Errors
      • Packet Collisions
      • Few users experiencing problems
      • Many users experiencing problems
      • Boost signal strength
      • Adjust data rates, other parameters
    • MIBs Tables: dot11PhyTxPower SupportedDataRatesTx SupportedDataRatesRx Objects: dot11EDThreshold (from dot11PhyDSSSEntry TABLE) dot11BeaconPeriod (from SMT Station Config TABLE) dot11OperationalRateSet (from SMT Station Config TABLE)
    • For correcting packet loss due to packet errors the system will adjust the power levels using the dot11PhyTxPower Table. For correcting packet loss due to packet collision the system will adjust the beacon period . If the beacon period is too small then the beacon packets will contribute to the traffic. RTS Threshold – If throughput is slow, decrease RTS threshold Fragmentation Threshold – Tricky to balance, small size vs number of packets, large size vs transmission time Retry Limits – Lower retry limits MIBs
    • Simple State Diagram Packet Loss occurring Figure out cause Increase Power Adjust data rates & beacon period No Packet Loss Monitor Network Lower power & adjust data rates/beacon period Packet Collisions Packet Errors
    • Access Point
      • For implementation and testing we will be using a Linksys WAP11 :
        • It is easy to setup and supports 802.11b
        • It can transfer data at the rate of 11 Mbps
        • It supports roaming
        • Compatible with all major O/Ss
      • I. Introduction
      • II. 802.11b Protocol Operation
      • III. System Design Overview
      • IV. Existing Tool Support
      • V. Future Works
    • Existing Tool Support (1)
      • WAP11 Unix Configuration Utility
      • LinkSys does not provide Linux SNMP client
      • The use of this tool fills the gap of initial setup and configuration on our Linux working environment
    • Existing Tool Support (2)
      • Wireless Access Point utilities for Unix (ap-utils-1.4.1)
      • Provides a set of utilities to configure and monitor wireless AP using SNMP protocols
      • Supports LinkSys WAP 11 hardware and its private mib – AT76C510.MIB.
      • Three utilities ~
        • ap-config : to config and get stats from Atmel-MIB based APs
        • ap-mrtg : to get stat from AP and return it in MRTG parsable format
        • ap-trapd : to receive, parse and log trap messages from AP
    • Existing Tool Support (2, continued)
      • Wireless Access Point utilities for Unix (ap-utils-1.4.1)
      • ap-config :
        • Configure and get stats from AP that supports MIB-II, IEEE 802.11 MIB and NWN DOT11EXT MIB, in addition to the private MIB.
        • Set bridging and wireless options, radio signal power.
        • Get information about AP software and hardware:
            • Dynamically updated wireless port statistics
            • Latest events and errors
            • List of current associated stations with information about signal quality and station activity.
    • Existing Tool Support (2, continued)
      • Wireless Access Point utilities for Unix (ap-utils-1.4.1)
      • ap-mrtg :
        • Get stat from AP and return it in MRTG (Multi Router Traffic Grapher) parseable format.
        • Get Ethernet statistics in bytes, wireless statistics in packets, associated stations number and Link Quality/Signal Strength stats from AP in client mode .
    • Existing Tool Support (2, continued)
      • Wireless Access Point utilities for Unix (ap-utils-1.4.1)
      • ap-trapd :
        • A SNMP trap processing daemon that accepts traps, parse them and store useful data using syslog, at logging LEVEL0.
        • Generic traps :
          • ColdStart / WarmStart
          • LinkDown / LinkUp
        • Specific traps :
          • Reset / Startup
          • APClientAssociating / APClientConnected
    • Existing Tool Support (3)
      • Cricket
      • Tool that supports traffic data collection which can be visualized (real-time trending) over the web.
      • A configuration, polling, and data-display engine wrapped around the Round Robin Database (RRD) tool.
      • Main components in Cricket:
        • Collector – runs from cron (e.g. every 5 mins) and fetches data from devices according to the info in the config tree.
        • Grapher – CGI application that allows user traversal of the config tree and the recorded data from a web browser.
        • Threshold Monitors – alert mechanism for sending traps.
      • I. Introduction
      • II. 802.11b Protocol Operation
      • III. System Design Overview
      • IV. Existing Tool Support
      • V. Future Works
    • Future Works Thank you !!
      • Setup the working environment for the experiment:
        • LinkSys WAP11 and the wireless network
        • Laptop running Linux (client user)
        • NMS Workstation
      • Gather relevant data on the performance-related MIB objects
      • Analyze the data for feasibility studies
      • Design and Implement performance monitoring and optimization interface (NMS) for AP and local users
      • System evaluation
    • References [1] D avid Kotz, Kobby Essien, Analysis of a campus-wide wireless network, Proceedings of the 8th annual international conference on Mobile computing and networking, September 23-28, 2002, Atlanta, Georgia, USA   [2] Diane Tang, Mary Baker, Analysis of a local-area wireless network, Proceedings of the 6th annual international conference on Mobile computing and networking, p.1-10, August 06-11, 2000, Boston, Massachusetts, United States   [3] Hutchins, R.; Zegura, E.W, Measurements from a campus wireless network, Communications, 2002. ICC 2002. IEEE International Conference on , Volume: 5, 28, April-2 May 2002, Pages:3161 - 3167 vol.5   [4] IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, P802.11, 1999.   [ 5 ] WAP11 Unix Configuration Utility: http://wap11gui.sourceforge.net/   [ 6 ] Wireless Access Utilities for Unix: http://ap-utils.polesye.net /   [ 7 ] Multi Router Traffic Grapher: http:// people.ee.ethz.ch/~oetiker/webtools/mrtg /   [ 8 ] Cricket: http:// cricket.sourceforge.net /   [ 9 ] RRD Tool: http:// people.ee.ethz.ch/~oetiker/webtools/rrdtool /   [10 ] Net-SNMP: http://www.net-snmp.org /   [ 11 ] Linksys: http:// www.linksys.com/products/product.asp?prid =157&scid=7   [ 12 ] 802.11 presentation: http://www.umiacs.umd.edu/partnerships/ltsdocs2004/Agrawala_talk.pdf