QoS Measurements Methods and Tools

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1 QoS Measurements Methods and Tools Contact: Jarmo prokkola Tel: VTT Technical Reseach Centre of Finland Easy Wireless Workshop, IST Summit, Budapest,

2 Network performance vs. QoS Network traffic measurements are employed to study the pure network performance Active measurements are performed by injecting traffic with known properties into the network Passive measurements consists of monitoring the existing traffic flow(s) at one or more points QoS measurements lie logically above network traffic measurements, and relate to the performance of networking applications. Objective QoS relates to something concrete and quantitative Packet loss, Delay, Jitter, Connection break length Subjective QoS corresponds to the service quality from the user perspective. Mean Opinion Score (MOS) tests are often used Subjective QoS can be estimated within certain limits from the basis of objective QoS (e.g., PESQ algorithm) 2

3 The purpose of QoS measurements & monitoring Answers to the question: How do the applications see the network? Real time QoS monitoring benefits Network administrators Network equipment manufacturers (testing) Networking application developers Operators End users Networking performance QoS aware applications (e.g., adapting video traffic flow) Handover triggering Congestion control management Accurate QoS measurements can be used by Network equipment manufacturers (testing) Networking application developers Researchers 3

4 Common QoS Measurement Architecture d c b a QoS (real time monitor or database) QoS analysis tool Traffic measurement tool Measurement point (network node) Traffic measurement tool Measurement point (network node) Figure 1. Functional decomposition of QoS measurement architecture. QoS measurement architecture includes: (a) Measurement points Located at network nodes (e.g., hosts, routers, firewalls) (b) Traffic measurement tool Captures packets and collects information of the desired traffic flow (c) QoS analysis tool Analyzes the collected data and calculates the actual QoS statistics (d) QoS monitor or database Analysis can be done in real time, and/or after the traffic traces have been collected. Analysis can be centralized to a specific server, or distributed to the network. 4

5 Single point measurements Round trip performance Figure 2. A single point measurement architecture. Measurement tool is operating in a single network node Round trip (RT) performance RT delay, RT jitter, RT packet loss Service response time E.g., HTTP, or commonly TCP performance Single point traffic statistics Offered traffic load, throughput, number of packets, packet sizes One way performance can not be measured 5

6 Two point measurements end to end performance Uplink (UL) performance Downlink (DL) performance Figure 3. An end to end measurement architecture. If the measurement tool is connected to both communicating nodes, this is called end to end measurement. One way performance can be measured separately for UL and DL Delay, jitter, packet loss, Directional traffic flow performance, e.g., real time traffic flows, UDP Traffic statistics from both points Real time monitoring requires control traffic Enables also two way monitoring possibility in a single point Requires flow identification and timing synchronization (for delay) between measurement points 6

7 Multipoint Measurements End to end performance can be split to network segment performances. E.g., what is the access network performance vs. core network performance? Enables bottleneck identification (e.g., how do individual network devices work?) Network segment 1 performance end to end performance Network segment 2 performance Measurement tool units could be passive components, and e.g., network administrator could activate monitoring when needed Analysis and result collection is challenging Measurement units could e.g., communicate with a centralized analysis tool Figure 4. An example of a 3 point measurement architecture. 7

8 QoS measurement tools used in EW: MOSET Figure 5. MOSET architecture. MOSET (VTT s freeware) is an active mobile service testing tool A testing application for mobile phone Execution of measurements / tests Instant results A testing server Collect & manage results Distribute test applications and tests Service response time measurements Connection establishment Retrieval of service content from network Measures HTTP/TCP performance from the user point or view 8

9 QoS measurement tools used in EW: QoSMeT Figure 6. QoSMeT architecture. QoSMeT (VTT) is a passive tool for measuring one way end to end network QoS from the application s point of view Real time measurements & accurate per packet statistics Is able to measure QoS of 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 QoSMeT can be run in the same device with the measured application or within the network path at desired points Measures e.g.: Delay, Jitter, Packet loss, Connection break duration (e.g., during a handover), Throughput and Offered load, and the volume of data sent/received GPS is used for clock synchronization 9

10 QoS measurement tools used in EW: M5 Multi Analyzer M5 (NetHawk) enables protocol monitoring, call and session tracing, key performance indicator (KPI) analysis, QoS measurements, and radio optimization measurements Monitors and analyzes UTRAN, GERAN, UMAN, IMS, WiMAX and core network interfaces at the same time. Supports all common transport techniques STM 1/OC 3, STM 4/OC 12, E1/J1/T1 in different modes and Ethernet Product components: Standard PC, NetHawk Adapters & cables and NetHawk M5 analysis SW Enables multipoint flow measurements with QoSMeT QoSMeT handles the end points, while M5 takes traces within the network path and decodes QoSMeT s control packets 10

11 QoS measurement tools used in EW: Agent based solution Figure 7. Agents taking delay measurements: It is seen that during video reception there is clearly more delay in the network. The EW agent (Moviquity) is a software component attached to the terminal and server software: Measurement of main E2E QoS parameters (BW, delay, jitter, packet loss) Action control (switch to preferred network, codec change) Three kinds of agents are required: Server Agent (EWSA) including Central Agent Network/Domain Agent (EWDA) User/Mobile Agent (EWMA) Via continuous feedback, it is possible to monitor actively the communications environment. Complete knowledge of the network and service status helps the server: To share and administrate resources with better efficiency Provide the maximum possible quality to the user taking into account the network the application service and the user profile 11

12 EW Measurement Examples: VHO Performance Delay 10 Connection break length 0.16 Delay [s] Connection loss length [s] Time [s] 0.01 Time [s] A simple handover scenario (VoIP application using Mobile IP): LAN WLAN 3G WLAN LAN Great differences in delay and jitter between network technologies (e.g., 3G one way delay is only barely acceptable for VoIP) Connection break length is on the order of seconds during handovers 12

13 EW Measurement Examples: HSDPA vs. WCDMA performance in a live network Downlink goodput/throughput performance as a function of data packet size Goodput [kbit/s] Goodput UDP HSDPA UDP 3G TCP HSDPA TCP 3G UDP HSDPA Throughput UDP packet size [B], TCP downloaded file size [B] A great improvement with HSDPA is got as compared to the basic 3G/WCDMA With UDP, goodput near to the operator s limit (1 Mbit/s) is achieved with reasonably small packet sizes. However, good TCP performance still requires quite large packet size RT delay is high also in HSDPA, thus limiting the performance of TCP => A typical WWW user does not see the real potential of HSDPA! 13

14 EW Measurement Examples: Multipoint Measurements in VTT s CNL 3G Network Delay [s] End to end Radio access RNC simulator Ethernet (after RNC) Uplink delay behavior in different sections of the network Lightly loaded network, to minimize the effects of queuing delay Measurement time [s] Most of the total delay is caused by the radio access part The effect of laboratory LAN is practically meaningless 14

15 Conclusions The complexity of QoS measurements grow when increasing the number of measurement points While single point measurements are simple, the information provided is very limited Analysis of even a large monitoring network can be simple if only traffic statistics are needed. However, traffic flow behavior analysis is complicated and needs also clock synchronization if delay measurements are desired. QoS measurements play important role in EW, several tools are used, and new tools have been developed The tools are used in revealing the performance of the existing networks, giving feedback to applications, and in measuring the performance of the developed QoS methods. Interesting performance behaviors have been found in numerous measurements in EW, and several publications have been done. 15