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

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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.

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slide1

“Measuring the performance of an active network measurement platform”

Timo-Pekka Heikkinen

TKK Networking laboratory

Supervisor: Prof. Raimo Kantola

Instructor: Lic. Tech. Marko Luoma

contents
Theory part

Terms and concepts

Practical part

Brix system

Results

Conclusions

Future work

Contents
theory part
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
terms and concepts 1
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
terms and concepts 2
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
practical part
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
devices
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

brix architecture

BrixWorx

Consolidator

Collector

Local Registry

Network Registry

Operations Center GUI,

Subscriber portal GUI

Verifier

Verifier

Test

Verifier

Brix Architecture
brix reporting
Brix Reporting

Data from the Brix system

results 1 4 case 1
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

results 2 4 case 1
Results (2/4), case 1

Measured one-way delay between Brix 1000 and Brix 100 verifiers

results 3 4 case 2
Results (3/4), case 2

Effects of high load on the delay measured by the Brix system

results 4 4 case 2
Results (4/4), case 2

Core router failure as reported by the Brix system.

conclusions 1 2 case 1
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
conclusions 2 2 case 2
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
future work
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
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