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Active Measurements on Wireless LAN

This project aims to test the real transport characteristics of two different wireless devices in an implemented network. The measurements were done using active measurement techniques and focused on factors such as encryption, operative modes, and link distances. The results provide insights into the maximum transmission speed and limitations of the tested devices. Future work includes examining time parameters and interoperability between different manufacturers.

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Active Measurements on Wireless LAN

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  1. Active Measurements on Wireless LAN I.Maric, M.Klobucar, I.Velimirovic CARNet/SRCE, Croatia

  2. Project goal(s) • To test real transport characteristics of a given wireless network (IEEE 802.11b) using active measurement • To compare two different devices included in implemented network • Limitations: • Measurement took place on the network that was already implemented and operational • Encryption was enabled on all devices

  3. Characteristics of tested wireless devices • DeviceA: CiscoAironet BRI340 Series 11Mbps WAN Ethernet Multipoint Bridge, 128 bits encryption (WEP), in point-to-point operative mode • Device B: LucentWavePOINT II Wireless Bridge Orinoco ROR, 64 bits encryption (WEP), Point-to-multipoint implemented with one omni-directional antenna on Master device Since one of the main goals of the testing was to compare two different devices included in implemented network, it was clear that devices should be compared only when operating in the same operative mode.

  4. Test network scheme (device A)

  5. Test network scheme (device A)

  6. Link distances: FER-FKIT620 m FKIT - PRAVO390 m FKIT - IMO130 m FKIT - ARHIV100 m

  7. Traffic generators and measurement technique Traffic generators: • Linux based standard PCs (Intel 486) • Software traffic generator (mgen): UDP packets, using different packet size • Max speed of generated traffic: 8.5 Mbps Measurement technique: • SNMP based tool for collecting data (ifInOctets, ifOutOctets MIB variables) • Sample period: 1 minute • Data stored in database (mSQL lightweight database)

  8. Expected results: expecting the nominal speed of 11 Mbps is not realistic. The reasons are partly in specific medium and protocol on MAC layer (CSMA/CA), while other parameters are weather conditions, quality of equipment, number of devices connected in WLAN that share the same medium, etc. The diagram shows some parameters that can limit actual transport speed. From the diagram it is clear that some parameters are under the control of a network designer (type and quality of devices) but some parameters are predefined and are not under direct control (distances, weather and other conditions, number of nodes, etc.) Expected results

  9. Results Measurements were done in 3 separated tests as follows: • Laboratory test (device A) • Test on site, point-to-point operative mode (device A) • Test on site, point-to-point & point-to-multipoint operative modes (device B)

  10. Test in lab (device A)

  11. Test on site (device A)

  12. Test on site (device B) Testing results for device B, in three different operative modes: point-to-point, point-to-multipoint 1-2 (one Master and two Slave devices) and point-to-multipoint 1-3 (one Master and three Slave devices)

  13. Comparison of two devices Maximum transmission speed (Mbps) for different packet size of generated traffic (100, 200, 500, 1000 and 1400 bytes) for devices A and B.

  14. Future work • Focus on time parameters (round trip time, response time, etc.) in order to see what are the limitations for time-sensitive applications like IP multicast, high quality voice and video over IP, etc. over wireless links • In order to test links on application level, some end-to-end testing will be performed, rather than node-to-node, as it was done in this measurements • Interoperability between different manufacturers is also an interesting topic for future research.

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