1 / 14

Network Performance Monitoring at Small Time Scales

Dina Papagiannaki, Rene Cruz, Christophe Diot. Network Performance Monitoring at Small Time Scales. Motivation. Network management for large-scale networks almost exclusively relies on SNMP. SNMP reports on aggregate link activity for the duration of the polling interval (5 mins).

addo
Download Presentation

Network Performance Monitoring at Small Time Scales

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dina Papagiannaki, Rene Cruz, Christophe Diot Network Performance Monitoring at Small Time Scales

  2. Motivation • Network management for large-scale networks almost exclusively relies on SNMP. • SNMP reports on aggregate link activity for the duration of the polling interval (5 mins). • Operators provision their network around these values according to provider-specific “acceptable” utilization levels.

  3. Questions • Can one infer delay “degradation” from SNMP link counters? • Can one infer delay performance from output link utilization? • At what time scale should these measurements be taken? • How do we summarize such high-resolution measurements in a 5-minute counter?

  4. Terminology • A micro-congestion episode is a short-lived episode in the lifetime of a link when packets face increased delays due to crosstraffic. • Metrics: Amplitude, Duration, Frequency

  5. Measurement Data: Sampling the Output Queue • Collect packet traces from links attached to the same router (set 1: OC-3, set 2: OC-12) • Compute single-hop delay using GPS accurate timestamps for arrival and departure OC-3 OC-3

  6. Methodology • Compute link throughput for non-overlapping time intervals of (1ms, 10ms, 100ms, 1s) duration • Collect all delay samples for each interval • Associate throughput level with delay distribution d2 d1 Output Link  

  7. Delay performance (OC-3)

  8. NO QUEUEING DELAY Instantaneous link utilization and delay • Instantaneous link utilization may be high even when packets do not experience congestion!

  9. 5 minutes too long to capture micro-congestion 5 minutes

  10. Inference of Duration and Frequency • If a micro-congestion episode persists in time, it should be visible across time scales • For each time scale τ we count the number of intervals exceedingθ throughput level • Measure fraction of overloaded intervals within each 5-minute interval Output link

  11. Reporting interval Inference of Duration (cntd) • If the fraction of “congested” intervals exceeding θ at time scale τ+1 is greater than the fraction of “congested” intervals at time scale τ, then significant fluctuations at time scale τ.

  12. Duration/Frequency

  13. Summary • 5 minute average utilization measurements can hide micro-congestion episodes. • There is no unique time scale that captures micro-congestion. • Impact needs to be studied at multiple time scales simultaneously. • New metric to address network performance monitoring at small time scales.

  14. Ongoing Work • We need to identify the impact of • Link capacity • Traffic arrival pattern • We have instrumented an entire router and analyze busy periods.

More Related