Timo-Pekka Heikkinen TKK Networking laboratory Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma

1. “Measuring the performance of an active network measurement platform” Timo-Pekka Heikkinen TKK Networking laboratory Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma

2. Theory part Terms and concepts Practical part Brix system Results Conclusions Future work Contents

3. Active measurements in data communication networks Active vs. passive measurements Types of active measurement mechanisms and methods Difficulties in making active measurements Accuracy of measurements Theory part

4. Probe 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 Round-trip delay Time it takes for a probe to travel from A to B and back to A Delay jitter The amount of variation in the measured delay Packet loss A packet is declared lost when it has failed to arrive to its destination in a certain amount of time Terms and concepts 1

5. Types of delay Processing delay Time it takes for a router to process a packet Transmission delay Time it takes for a router to push a packet to the link Propagation delay Time it takes for a signal to travel across the physical medium Queuing delay Time the packet spends inside routers’ queues Terms and concepts 2

6. Measuring the performance of an active measurement system (Brix Networks) 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

7. Devices Brix 1000 Verifier • Synchronization • Brix 1000 GPS-receiver • Acted as an NTP-server • Brix 100’s NTP synched • NTP synch in the complex case • No need for GPS because RTT was measured Brix 100 Verifier

8. BrixWorx Consolidator Collector Local Registry Network Registry Operations Center GUI, Subscriber portal GUI Verifier Verifier Test Verifier Brix Architecture

9. Brix Reporting Data from the Brix system

10. Results (1/4), case 1 Cumulative probability distributions of all tested devices when measuring one-way delay. Delay shown with and without NTP-offset correction

11. Results (2/4), case 1 Measured one-way delay between Brix 1000 and Brix 100 verifiers

12. Results (3/4), case 2 Effects of high load on the delay measured by the Brix system

13. Results (4/4), case 2 Core router failure as reported by the Brix system.

14. More time should have been spent on designing the test setup 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

15. Test parameters should have been selected more carefully Measurement reports are lost too often Congestion and node failures can be detected with Brix Short link failures were undetected Conclusions (2/2), case 2

16. Case 1 should be done in a more complex network environment Case 2 should be done with the same equipment as used in case 1 GPS synchronized Brix 1000’s NTP offset measurement Future work