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“Measuring the performance of an active network measurement platform”. Timo-Pekka Heikkinen TKK Networking laboratory Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma. Theory part Terms and concepts Practical part Brix system Results Conclusions Future work. Contents.
“Measuring the performance of an active network measurement platform”
TKK Networking laboratory
Supervisor: Prof. Raimo Kantola
Instructor: Lic. Tech. Marko Luoma
Active vs. passive measurements
Types of active measurement mechanisms and methods
Difficulties in making active measurements
Accuracy of measurementsTheory part
An artificial packet containing information relevant to the measurement (e.g. timestamp, seq. # etc.)
One-way latency (delay)
Time it takes for a probe to travel from point A to point B in a network
Time it takes for a probe to travel from A to B and back to A
The amount of variation in the measured delay
A packet is declared lost when it has failed to arrive to its destination in a certain amount of timeTerms and concepts 1
Time it takes for a router to process a packet
Time it takes for a router to push a packet to the link
Time it takes for a signal to travel across the physical medium
Time the packet spends inside routers’ queuesTerms and concepts 2
Two test cases / network environments
Simple network topology
Comparison of the Brix system versus an well-known accurate measurement system (AX4000)
(Relatively) Complex network topology
Is Brix able to detect certain events in the network?
Overall, how does the Brix system perform?Practical part
Brix 1000 Verifier
Brix 100 Verifier
Data from the Brix system
Cumulative probability distributions of all tested devices when measuring one-way delay. Delay shown with and without NTP-offset correction
Measured one-way delay between Brix 1000 and Brix 100 verifiers
Effects of high load on the delay measured by the Brix system
Core router failure as reported by the Brix system.
Brix 100’s are not accurate enough to measure sub-millisecond one-way delays
Clock instability big issue
Accuracy ~940 μs, ~120 μs with NTP corr.
Brix 1000’s are accurate when using GPS synchronization
Clocks stabile enough
Accuracy ~50 μs, ~10 μs with NTP corr.
AX4000 accuracy ~1 microsecond (when using only one clock)Conclusions (1/2), case 1
Measurement reports are lost too often
Congestion and node failures can be detected with Brix
Short link failures were undetectedConclusions (2/2), case 2
Case 2 should be done with the same equipment as used in case 1
GPS synchronized Brix 1000’s
NTP offset measurementFuture work