A First Stab at 802.11 Metrics

1. A First Stab at 802.11 Metrics Bob Mandeville bob@iometrix.com B. Mandeville, Iometrix

2. Introduction • We present a first cut of a list of metrics believed to be important for wireless performance • This presentation is AP-centric • Does not mean there are not important client-centric metrics as well! • Input welcome! • Please help with identifying additional metrics B. Mandeville, Iometrix

3. Considerations • We need to be able to reference well-defined metrics for wireless when we build test definitions and test cases • In defining metrics it is important to focus on the wireless aspects of the metrics • we need to concentrate on what is special about wireless metrics (examples to follow) B. Mandeville, Iometrix

4. Initial List of Wireless Performance Metrics • Maximum Forwarding Rate • FWMOL (Fwd rate at max offered load) • Frame Loss, Frame Loss Rate • Latency • Jitter • Association Capacity, Association Rate • Rate versus Range B. Mandeville, Iometrix

5. RFC 2285 Considerations • RFCs 2285 and 2889 define terms and methods for testing wired switched Ethernet performance • Basic definitions contain useful content for wireless metric definitions but we cannot take those definitions and directly apply them to wireless • How do traffic orientations and configurations translate to 802.11? • Need to specify protocol modifiers • Could be a long list, starting with RTS/CTS, fragmentation, security modes… • Measure metrics under optimum signal conditions • Conducted signals - DUT can do no better than this! B. Mandeville, Iometrix

6. First shot at defining wireless forwarding rate • Definition of wireless forwarding rate should include a clear treatment of at least the following aspects (3 slides): • The metric (wireless forwarding rate) must indicate what interfaces, wireless and wired, are the source and destination of the measurement traffic configuration: • .11 to .3 • .11 to .11 • .11 to .3 to .11 • Could call this aspect of the metric ‘traffic configuration’ • It is specific to 802.11 • RFC 2285 only defines traffic orientation (unidirectional, bidirectional) and distribution (partial mesh, full mesh) B. Mandeville, Iometrix

7. First shot considerations… • Need to distinguish between the inherent fwd rate capabilities of a device and the possibly reduced capabilities in a real wireless environment • Need to specify what protocol exchanges must take place before the measurement of the metric can take place • association/authentication rates and capacities are separate metrics B. Mandeville, Iometrix

8. More considerations • Need to define what address sequencing is to be used when measuring wireless forwarding rate • Need to define traffic pattern including burst. • RFC 2285 definition for burst does not apply (minimum ifg) • Perhaps to be defined outside of forwarding rate definition • Need to discuss list of modifiers that may be applied to forwarding rate measurement: RTS/CTS, fragmentation B. Mandeville, Iometrix

9. Carry-over definitions • RFC 2285 definitions of Intended Load and Offered Load (developed with half-duplex Ethernet in mind) are very relevant for 802.11 contentious shared medium • RFC 2285 distinctions between ‘maximum forwarding rate’ and ‘forwarding rate at maximum offered load’ are relevant to 802.11 B. Mandeville, Iometrix

10. Going forward… • Does group think the initial list of performance metrics is of value? • Does group think the considerations for wireless forwarding rate metric enumerated here form basis for going forward with work further on the definition • Is there something missing? • Is there another better approach? • Again: definition of a wireless performance metric is not a test definition but supplies a necessary component for wireless test definitions B. Mandeville, Iometrix