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Link Failures in IP Networks:. A Closer Look. Yashar Ganjali Sprint Advanced Technology Lab. August 5, 2003. Previous Work. Link Failures. Maintenance. Unplanned. 70 % of Unplanned. Shared: Router Related, Optical Related, …. Individual Link Failures. Our Work.

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Link Failures in IP Networks:

A Closer Look

Yashar Ganjali

Sprint Advanced Technology Lab.

August 5, 2003


Previous work
Previous Work

Link Failures

Maintenance

Unplanned

70 % of

Unplanned

Shared: Router Related, Optical Related, …

Individual Link Failures

Link Failures in IP Networks: A Closer Look


Our work
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

Link Failures in IP Networks: A Closer Look


Is is failures feb 2003
IS-IS Failures, Feb. 2003

Link Failures in IP Networks: A Closer Look


Number of failures per day
Number of Failures per Day

Link Failures in IP Networks: A Closer Look


Zoom in
Zoom In

Link Failures in IP Networks: A Closer Look


Zoom in cont d
Zoom In (Cont’d)

Link Failures in IP Networks: A Closer Look


High failure periods
High Failure Periods

  • Periods with a large number of failures (HNP)

  • Periods in which a large percentage of links are down (HDP)

Link Failures in IP Networks: A Closer Look


Number vs duration of failures
Number vs. Duration of Failures

Link Failures in IP Networks: A Closer Look


High failure periods1
High Failure Periods

Link Failures in IP Networks: A Closer Look


Periods with high number of failures
Periods with High Number of Failures

Link Failures in IP Networks: A Closer Look


High failure periods cont d
High Failure Periods (Cont’d)

  • We can also classify high failure periods based on spatial distribution of the links failing in those periods.

Link Failures in IP Networks: A Closer Look


Spatial distribution june 17 2003
Spatial DistributionJune 17, 2003

Link Failures in IP Networks: A Closer Look


Spatial distribution feb 26 2003
Spatial DistributionFeb. 26, 2003

Link Failures in IP Networks: A Closer Look


Links with high duration of failures
Links with High Duration of Failures

Link Failures in IP Networks: A Closer Look


Links with high number of failures
Links with High Number of Failures

Link Failures in IP Networks: A Closer Look


Matching is is failures with sonet alarms slos
Matching IS-IS Failures with SONET alarms (SLOS)

Link Failures in IP Networks: A Closer Look


Preliminary results
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.

Link Failures in IP Networks: A Closer Look


Unmatched slos alarms
Unmatched SLOS alarms

Link Failures in IP Networks: A Closer Look


Matching slos alarms
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

Link Failures in IP Networks: A Closer Look


Matching is is failures sonet alarms
Matching IS-IS Failures & SONET alarms

Link Failures in IP Networks: A Closer Look


Unmatched slos alarms considering removed links
Unmatched SLOS alarms(considering removed links)

Link Failures in IP Networks: A Closer Look


Unmatched slos alarms1
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???

Link Failures in IP Networks: A Closer Look


Research direction
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?

  • ???

Link Failures in IP Networks: A Closer Look


You always pass failures on the way to success!

Thank you!

Link Failures in IP Networks: A Closer Look


Spatial temporal correlation of failures
Spatial-Temporal Correlation of Failures

Link Failures in IP Networks: A Closer Look


Spatial temporal correlation of failures1
Spatial-Temporal Correlation of Failures

Link Failures in IP Networks: A Closer Look


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