1. Yashar Ganjali Sprint Advanced Technology Lab. August 5, 2003 Link Failures in IP Networks: A Closer Look

2. August 5, 2003Link Failures in IP Networks: A Closer Look 2 Previous Work Link Failures UnplannedMaintenance Individual Link Failures Shared: Router Related, Optical Related, … 70 % of Unplanned

3. August 5, 2003Link Failures in IP Networks: A Closer Look 3 Our Work Goal: gaining a deeper understanding of the causes & characteristics of link failures How: –Using SONET alarm logs –Focusing on high failure links/periods

4. August 5, 2003Link Failures in IP Networks: A Closer Look 4 IS-IS Failures, Feb. 2003

5. August 5, 2003Link Failures in IP Networks: A Closer Look 5 Number of Failures per Day

6. August 5, 2003Link Failures in IP Networks: A Closer Look 6 Zoom In

7. August 5, 2003Link Failures in IP Networks: A Closer Look 7 Zoom In (Cont’d)

8. August 5, 2003Link Failures in IP Networks: A Closer Look 8 High Failure Periods 1.Periods with a large number of failures (HNP) 2.Periods in which a large percentage of links are down (HDP)

9. August 5, 2003Link Failures in IP Networks: A Closer Look 9 Number vs. Duration of Failures

10. August 5, 2003Link Failures in IP Networks: A Closer Look 10 High Failure Periods

11. August 5, 2003Link Failures in IP Networks: A Closer Look 11 Periods with High Number of Failures

12. August 5, 2003Link Failures in IP Networks: A Closer Look 12 High Failure Periods (Cont’d) We can also classify high failure periods based on spatial distribution of the links failing in those periods.

13. August 5, 2003Link Failures in IP Networks: A Closer Look 13 Spatial Distribution June 17, 2003

14. August 5, 2003Link Failures in IP Networks: A Closer Look 14 Spatial Distribution Feb. 26, 2003

15. August 5, 2003Link Failures in IP Networks: A Closer Look 15 Links with High Duration of Failures

16. August 5, 2003Link Failures in IP Networks: A Closer Look 16 Links with High Number of Failures

17. August 5, 2003Link Failures in IP Networks: A Closer Look 17 Matching IS-IS Failures with SONET alarms (SLOS) IS-IS Failure% MatchedIS-IS Failure% Matched STK.Feb-Jun.20030.58STK.Feb-Jun.2003-NM-NRR0.65 STK.Feb-Jun.2003-HDL0.68STK.Feb-Jun.2003-NM-NRR-HDL0.85 STK.Feb-Jun.2003-HDP0.19STK.Feb-Jun.2003-NM-NRR-HDP0.65 STK.Feb-Jun.2003-HNL0.77STK.Feb-Jun.2003-NM-NRR-HNL0.84 STK.Feb-Jun.2003-HNP0.56STK.Feb-Jun.2003-NM-NRR-HNP0.78 STK.Feb-Jun.2003-NM0.61STK.Feb-Jun.2003-NM-RR0.29 STK.Feb-Jun.2003-NM-HDL0.69STK.Feb-Jun.2003-NM-RR-HDL0.00 STK.Feb-Jun.2003-NM-HDP0.28STK.Feb-Jun.2003-NM-RR-HDP0.07 STK.Feb-Jun.2003-NM-HNL0.81STK.Feb-Jun.2003-NM-RR-HNL0.16 STK.Feb-Jun.2003-NM-HNP0.65STK.Feb-Jun.2003-NM-RR-HNP0.26

18. August 5, 2003Link Failures in IP Networks: A Closer Look 18 Preliminary Results About 58% of all failures match with a SLOS alarm. High Failure Links have a higher correlation with SLOS alarms (85%) Router Related Failures show much less correlation than other classes (0-29%). Periods with high number of failures show more correlation than periods with high duration of failures.

19. August 5, 2003Link Failures in IP Networks: A Closer Look 19 Unmatched SLOS alarms

20. August 5, 2003Link Failures in IP Networks: A Closer Look 20 Matching SLOS alarms Problem: A large percentage (45%) of SLOS alarms do not correspond to any IS-IS failures Solution: Remove links which are not up or links which go down for ever Result: Less than 2% of SLOS alarms do not correspond to any IS-IS failures

21. August 5, 2003Link Failures in IP Networks: A Closer Look 21 Matching IS-IS Failures & SONET alarms

22. August 5, 2003Link Failures in IP Networks: A Closer Look 22 Unmatched SLOS alarms (considering removed links)

23. August 5, 2003Link Failures in IP Networks: A Closer Look 23 Unmatched SLOS alarms Spread over time Almost half of them have a matching alarm (SLOS SLOS cleared) Minimum time between SLOS and SLOS cleared is 9 seconds. More investigation???

24. August 5, 2003Link Failures in IP Networks: A Closer Look 24 Research Direction High Failure Periods: Study cascading effects, spatial distribution of failures High Failure Links: Predicting future failures based on passed ones. Network Availability: How do failures affect network availability? ???

25. August 5, 2003Link Failures in IP Networks: A Closer Look 25 You always pass failures on the way to success! Thank you!

26. August 5, 2003Link Failures in IP Networks: A Closer Look 26 Spatial-Temporal Correlation of Failures

27. August 5, 2003Link Failures in IP Networks: A Closer Look 27 Spatial-Temporal Correlation of Failures