Multipoint QoS Measurements with QoSMeT

Pekka Perälä, Jarmo Prokkola and Marko JurvansuuConverging Networks Laboratory - VTT

pekka.perala@vtt.fiTel: +358 400 989 353

P.O. Box 1100 (Street: Kaitoväylä 1, Oulu)FI-90571 Oulu, Finland

23.09.2008

VTT TECHNICAL RESEARCH CENTRE OF FINLAND

Contents

• Introduction• Overview of QoS Measurement Tool (QoSMeT)• The multipoint measurements with QoSMeT• Measurement examples• Conclusions

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Introduction (1)

• Real-time applications demand high quality from the network (low delay, low jitter, low packet loss, etc.)

• High available BW does not always ensure QoS• Many methods reveal the overall performance of the network, but it does not

necessary reflect well on how the individual applications behave.

It is important to find out the QoS metrics of a single application• The passive E2E QoS measurements reveal the QoS experienced by an

application• VTT's QoSMeT tool measures one-way QoS metrics• For e.g. SLA verification

• However, E2E measurement is not able to locate the problematic link, it only can indicate that a performance problem exists

One solution to the problem is multipoint measurement that reveals the performance on per network segment basis.

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Introduction (2)

• Multipoint QoS measurements are continuation to the development work of QoSMeT (ITEA Easy wireless & Celtic Easy Wireless 2)

• Objective is to maintain QoS while roaming over heterogeneous networks

• The implemented demonstrator integrates traditional network analyzer and E2E QoS measurement

• QoSMeT and multipoint measurement systems have been tested not only in controlled environment, but also in public networks (HSPA, public Wi-Fi, WiMAX, etc.)

• M. Jurvansuu, J. Prokkola, M. Hanski, P. Perälä, ”HSDPA Performance in Live Networks,” In proceedings of IEEE International Conference on Communications (ICC 2007).

• Our Converging Networks Laboratory (CNL) has been the main facility for the tests in addition to public networks

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QoSMeT Overview (1)

• QoSMeT is a passive tool software for measuring one-way end-to-end network performance in real-time from the application’s point of view

• Designed for measuring especially real-time applications (e.g., VoIP, video conferencing), but other networking applications can be measured as well.

• The tool works practically over any kind of network as long as IP is supported

• No additional hardware

• One-way delay measurements require GPS time stamping (…and GPS equipment)

• Win32 platform (Linux is coming)J. Prokkola, M. Hanski, M. Jurvansuu, M. Immonen, ”Measuring WCDMA and HSDPA Delay Characteristics with QoSMeT,” In proceedings of IEEE International Conference on Communications (ICC 2007).

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QoSMeT Overview (2)

•A separate TCP connection is used for carrying the QoSMeT control data over the network if real-time mode is used

•Application is not aware of the measurement•Records in real-time:

•Average QoS statistics•Accurate per packet statistics

•The most important measured QoS metrics• Delay • Jitter (average and absolute)• Packet loss• The length of a connection break (for example during a vertical handover)

• Traffic statistics• Pseudo-subjective analysis: VoIP MOS (Mean Opinion Score) quality

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QoSMeT Measurement Examples: WCDMA and HSPA Delay and Goodput Performance

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J. Prokkola, P. Perälä, M. Hanski and E. Piri ” 3G/HSPA Performance in Live Networks from the End User Perspective,” submitted to IEEE ICC2009

VTT TECHNICAL RESEARCH CENTRE OF FINLAND

Multipoint Measurement Principle

• Multipoint measurements help to locate the performance bottlenecks by revealing the QoS of each network segment

• P. Perälä, M. Jurvansuu, J. Prokkola, ”Combined Terminal and Network Measurement System for Bottleneck Localization,” In proceedings of Tridentcom 2008

• The traffic is captured from several (> 2) measurement points (MP), where the traffic is captured

• The one-way performance can be split to the performance of network segments based on the captured data

The segment with the poorest performance can be found

According to multipoint measurement principle the network performance is divided into performances of network segments

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Multipoint measurement system

• GPS timestamping enables breaking-down the one-way delays

• Integration of QoSMeT and Nethawk M5 analyzer

• Each measurement point captures the data of interest (generated by single or multiple applications)

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Multipoint measurement system applied to UMTS.

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Public Wi-Fi network multipoint measurements (1)

• Conducted in panOulu, a city-wide WLAN (802.11g) network

• Three measurement points (two QoSMeTs and a commercial network analyzer)

• One-way delay, access network delay and Internet delay were calculated

• Packet loss was found interesting too

• UDP streams of different rates

Figure 9. panOulu measurement setup.

E2Edelay(ms)

Accessnetwork(ms)

Internet(ms)

Average delay

14.49 2.85 11.64

Figure 10. One-way delay statistics for VoIP call (steady state performance)

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Public Wi-Fi network measurements (2)

• In steady state the Internet delay is dominating (Fig. 12)

• After max bandwidth (< 10 Mbps) is exceeded, E2E delay increases due to the access network

• When access point starts discarding packets it causes increased E2E packet loss

• Internet delay is quite constant with all loads and packet loss negligible

• The access network is the bandwidth bottleneck and also the on with longest delay in stress situations

Figure 12. Average delays and packet loss

Figure 11. PanOulu delay performance with 16 Mbps offeredload.

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Conclusions & Future Work

• QoSMeT enables QoS measurement of IP networks from single applications point of view

• With multipoint measurement systems it is possible to locate performance bottlenecks in IP networks

• The multipoint measurement system combined terminal and intermediate point measurement

• The work is continued in Celtic Easy Wireless 2 project

• Kick-off meeting 23-24 of September

• Light-weight measurement agents to the network for multipoint measurements

• The amount of measurement data that is collected and processed in real-time becomes problematic

• Application adaptation based on QoS measurements (e.g., SVC)

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References

[ref1] J. Prokkola, M. Hanski, M. Jurvansuu, M. Immonen, ”Measuring WCDMA and HSDPA Delay Characteristics with QoSMeT,” In proceedings of IEEE International Conference on Communications (ICC 2007).

[ref2] M. Jurvansuu, J. Prokkola, M. Hanski, P. Perälä, ”HSDPA Performance in Live Networks,” In proceedings of IEEE International Conference on Communications (ICC 2007).

[ref3] P. Perälä, M. Jurvansuu, J. Prokkola, ”Combined Terminal and Network Measurement System for Bottleneck Localization,” In proceedings of Tridentcom 2008.

[ref4] J. Prokkola, P. Perälä, M. Hanski and E. Piri, “3G/HSPA Performance in Live Networks from the End User Perspective” submitted to IEEE ICC2009.

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