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CMT II: An Agent Based Framework for Comprehensive IP Measurements Thomas Pfeiffenberger and Thomas Fichtel Advanced Networking Center Salzburg Research Forschungsgesellschaft mbH 5020 Salzburg, Austria Email: {tpfeiff, tfichtel}@salzburgresearch.at

Abstract— The Communication Measurement Tool II (CMT II) is a framework for comprehensive IP measurements. It is the next development stage of the succeeded measurement framework called CMToolset. The purpose of an distributed measurement framework, like CMT II is to provide detailed information about the network for performance evaluation, network engineering or detecting network problems. Regarding this point CMT II operates on different layers of the OSI layer model, as well as it is designed in an open structure in order to allow further extensions for upcoming protocols, networks and applications. Furthermore CMT II is designed to conduct active as well as passive measurements. CMT II is based on the agent framework JADE, which allows the deployment of measurement agents on different platforms and the interaction with other agent frameworks. Unlike other measurement tools, CMT II can also be applied on wireless or mobile scenarios to study the influences of wireless and mobile data transmissions.

I. I NTRODUCTION This paper first gives an introduction into IP measurements and it describes the necessity of comprehensible measurements. It also gives a short overview over existing measurement initiatives and tools and explains its similarities and differences to CMT II, including the historical development of CMToolset. The special architecture of CMT II based on the agent platform JADE is described in detail in the third section of this paper, followed by the annotation of the different measurement methods. Finally exemplary measurement results are presented and the further development of CMT II is discussed. The ongoing growth of the Internet in the last decade enhances the requirements for precise measurements. Internet measurement, based on active measurement techniques, is an important part of performance measurement system. The main focus on today’s measurements are collecting and analysing of network information on the purpose of performance evaluation, network engineering and detecting network problems. Furthermore, accurate, representative and comprehensive measurements are a fundamental part regarding the development of system models. To analyse the long term behaviour or to control the quality of service (QoS) of a flow in the Internet, measurements can be applied. To make these measurements comparable it is extremely important to standardize the measurement procedures. There are various ongoing activities in the IETF and the ITU-T to establish measurement standards. Several groups in this

standardization bodies, the Working Group (WG) for IETF and the Study Group (SG) for ITU-T, will deal with the possibility to establish standards for different kinds of information gathering in the Internet. The Remote Monitoring (RMON) WG, at the IETF, is responsible for remote monitoring. The former real-time flow-measurement (RTFM) WG was focused to examine the mechanism to capture export flow data to external accounting systems. Today the IP Flow Information Export (IPFIX) WG and the Packet Sampling (PSAMP) WG will deal with this topic. Active performance measurements metrics, like the one way delay, will be adopted by the IP Performance Measurement (IPPM) WG. One of the goals of this WG is to standardize a measurement and management protocol for test equipments to interoperate between different vendors. The IPPM WG cooperates also with other standardization bodies, like the ITU-T SG 12 and SG 13, to discus and establish these metrics. The ITU-T SG 4 works on a new recommendation for performance measurements of IP networks and services. The recommendation O.iptest implies an IP test packet format to interoperate between different test equipment, analog to IPPM. II. S TATE OF THE A RT A. Measurement Types There are to common approaches two evaluate the performance of the Internet. On the one hand the active measurement approach and the other hand the passive measurement approach. For a better understanding of the behaviour of the Internet both can be used in conjunction with one another. There are different approaches for passive measurements in the Internet, like Remote Monitoring (RMON), Simple Network Managment Protocol (SNMP) or Cisco IOS NetFlow. The passive approach does not increase load on the network and it measures real load on the network and its behaviour. The active approach injects traffic to the network. By generating traffic between a sender and a receiver it is possible to evaluate the QoS or the Service Level Agreement (SLA). Collecting the results from active or passive measurements will bring extra traffic to the network. Therefor it is very important to define the measurement scenario in such a way that the additional traffic will not influence the measurements itself. This could be done by an extra management network or by collecting the measurement results at a defined stage.

B. Internet Performance Measurement Architectures and Initiatives The following part will give an overview about other projects and activities in the field of distributed active measurements in the Internet. Some related work is done in different research centers. The SATURNE platform [1] performs active end to end measurements according to the IPPM metrics. A traffic sender, called emission module, injects active UDP packets to the network. The capture module receive and analyses the probe traffic flows. The results are stored in database. The database is one part of the data management module. The second part is the graphical representation of the results. To synchronize the emission module and the capture module for a accurate time, a GPS hardware or the network time protocol (NTP) is used. The main goal of the SATURNE platform is to validate and monitor the observance of SLAs between Internet Service Providers (ISP) and customers. Surveyor [2] is an additional measurement infrastructure and is hosted at the Advanced Network & Service Group. The project supports the IPPM metrics to measure the performance on links between two hosts. To provide multi-point measurements hosts are equipped with GPS hardware to synchronize the local clock. A further aim of the project is to develop tools to analyse these measurements to understand the complexity and the behaviour of today’s Internet. Test Traffic Measurements (TTM) is a service with license costs offered by RIPE NCC [3]. It is based on distributed hardware boxes with GPS devices to synchronize the internal clock, similar to other projects. This Test Box Hosts can be ordered at RIPE NCC. The measured parameters are also based on metrics defined by the IPPM WG. The Internet end to end Performance Monitoring (IEPM) group at Stanford Linear Accelerator Center (SLAC) is working since 1995 on monitoring Internet connectivity on a high speed network. Different tools, like PingER, are developed to analyze and measure the behavior of the end to end performance of a link. The National Laboratory for Applied Network Research (NLANR) started the Active Measurement Project (AMP) with the focus on active multi-point measurements and analyses on high performance connection networks. The measurements are based on round trip time (RTT), packet loss, topology discovery and throughput. The AMP are used in the high performance networks of the National Science Foundation (NSF). The architecture consists of distributed active monitors for generating active measurements between each other. The collected data from the active monitors are sent to the analysis machine. By using a web browser the calculated results from the analysis machine can be displayed. Skitter is a tool developed by the Cooperative Association for Internet Data Analysis (CAIDA). By using skitter it is possible to make active probes in the Internet. By collecting information about the time to live (TTL) and RTT on each hop between source and destinations, route changes or spe-

cial events can be detected. CIADA provides also tools and frameworks to analyse the collected data. The Evergrow Traffic Observatory Measurement InfrastruCture (ETOMIC) [4] is a active measurement infrastructure developed in the Evergrow project. The main goal is to setup measurements with a very fine timescale (up to 10 nano seconds) in a globally synchronized measurement infrastructure. To achieve this fine timescale and the globally synchronized measurement infrastructure GPS equipment is used. The active measurement boxes are equipped with Endace DAG 3.6 GE capture cards for passive monitoring. with these cards boxes are enabled to capture the packets on the interfaces with speed of gigabits per second. By using scripts and APIs a measurement scenarios can be specified. The measurement scenarios and the results are stored in a database. A very simple and easy web interface is used to administrate measurements and results. A further project at the NLNAR is the Passive Measurement and Analyses (PMA) [5] project. The goal of the PMA project is to find key performance indicators (KPI) of the Internet. This KPIs are used to describe the behaviour of the Internet and to understand and deliver new insights for users, service providers and network providers. Passive monitor points are available up to a speed of 10Gigabit/s and are used on high speed networks. Traces from the PMA project are available at the PMA Web page in the Dag PoS format. The One Way Active Measurement Protocol (OWAMP) [6] developed by the IPPM WG defines two inter–dependent protocols, the OWAMP-Control and the OWAMP-Test. This two protocols allow heterogeneous test equipment to interact with each other. It is possible to specify sender and receiver address, port number and the type of traffic. Security and authentication is also an important part in this protocol. Only authenticated user and measurement points can configure measurement scenarios. At the moment there are two known implementation of this protocol. The OWAMP implementation from Internet2 and the J-OWAMP implementation from the University of Aveiro. CMT II OWAMP from Salzburg Research is based on the J-OWAMP implementation. A remote interoperability test of these three implementations was done during an interoperability event organised by the EU project MOME, see [7]. C. Time Accuracy and Synchronization In order to perform multi-point correlation or end to end delay measurements an accurate time synchronization scheme for the distributed measurement system is required. The used measurement points should have GPS equipment or use NTP for synchronization. This is necessary to provide a highprecision time systems for distributed multi-point active measurements. To provide high-precision timestamps it is also important to use special hardware for receiving or sending packets. A further important aspect to provide high accurate timestamps is the process scheduling mechanism in the used operating system.

D. CMToolset History

A. Management Layer

The first idea to develop a remote controlled distributed measurement framework comes up in 1997. In a joint project with the Telekom Austria, an Austrian Telecom company and Internet provider, a first prototype of an remote controlled distributed measurement framework was developed. Since this time many efforts have been taken to improve the measurement framework. The main focus was to make active multipoint measurements with a very accurate timing. CMToolset supports to generate different kinds of traffic models. Further developments were done in a joint project with Siemens Austria to make the distributed measurement agents platform independent. So it was possible to run the agent on several operating system, such as SunOS, VxWorks, Windows and Linux. In the European IST project AQUILA new developments were made. A native GPS support for the distributed measurement agents were implemented. To handle the big amount of measurement data a new database model were designed. The measurement scenarios and the measurement results are controlled via a WEB based graphical user interface. All this features offer the possibility to use CMToolset in a distributed active measurement scenarios to evaluate the behaviour of a flow in the Internet or to control the QoS and the SLA. To compare measurement results after or during a measurement scenarios will bring new possibilities for an network operator to manage their networks. Due to the history of CMToolset different publications either about CMToolset or using CMToolset are available, see [8]–[10].

The management layer is responsible for the administration of measurement tasks as well as to be a connector between the database and the measurement agents. A measurement task is defined by the following main parameters: • name • type (defines the measurement method) • start and end time • derivative time • results (defines the type of results) These parameters are only main parameters, additional arguments are necessary depending on the type of measurement. For traceability all measurement tasks are held in the database. The management agent periodically polls the database for new measurement tasks. These new tasks are analysed and then sent to the appropriate measurement agent. The communication between the management agent and the measurement agent is done via Foundation for Intelligent Physical Agents (FIPA) compliant messages. These messages are addressed by fully qualified agent names, which measurement agents have to apply when joining the measurement framework. Because of JADE the fully qualified name consists of two parts, the platform name and the agent name (e.g.: agent1@platform). The management agent monitors the execution of measurement tasks and reports events and states into the database. Measurement results produced by measurement agents are sent to the management agent, in order to be verified upon correctness and stored in the database.

III. A RCHITECTURE CMT II uses a distributed architecture of management and measurement agents. As illustrated in figure 1 CMT II consists of four main parts: The management layer, measurement layer, presentation layer and the database. In order to simplify the development of the framework as well as future agent development, CMT II is based on the Java Agent Development Framework (JADE) [11]. Because of JADE the measurement framework builds up a platform which consists of containers of agents, see III-E. JADE is responsible for the communication, administration and mobility of the measurement agents. Additionally to the CMT II framework an appropriate time service is essential. For starting and stopping measurement tasks and especially for one-way delay measurements it is absolutely necessary to synchronise clocks of the complete CMT II framework. The time synchronization is either be done with GPS for high accuracy measurement agents or via NTP for standard agents, which is already used in other measurement tools. Using NTP for time synchronization one’s have to be clear in mind that NTP traffic can influence results and therefore a separate network should be used. CMT II handles this problem by using a time-triggered architecture where management information and results depending on the configuration are transmitted before and after the actual measurement. In the following sections the different layers of CMT II are explained more detailed.

B. Measurement Layer The measurement layer has to fulfil the measurement tasks. This layer consists of many different measurement agents which are doing the measurement jobs. There are single-point agents (e.g. for passive monitoring) and multi-point agents (e.g. for sender-receiver scenarios). A detailed description of all possible measurement scenarios is presented in section IV. When a measurement agent is started it registers itself at the management agent concerning its measurement capabilities and host specific parameters (e.g. network interfaces). The measurement agent monitors its own status and utilisation and reports those values and events to the management layer, in order to ensure traceability of results. C. Presentation Layer The presentation layer is used to make the measurement results available for the community. In the simplest way this is realised with CMT II graphical user interface (GUI). With the CMT II GUI the user on the one hand can create and manage measurement tasks and on the other hand visualize measurement results. Regarding this point statistical analysis of results and user definable graphs are provided. The calculation of the empirical mean, median, variance and standard deviation is done during execution and at the end of the measurement task. The second possibility to allow access to measurement results is via the export interface. With the export interface results are dumped into an ascii text file and are provided for

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download via a web server. This has the advantage, that the research community can analyse the results with other 3rd party analysing tools (e.g. Matlab). The third alternative for accessing measurement results is the one-way active measurement protocol (OWAMP) [6] interface. OWAMP, a proposed standard that is currently going through the standardization process within IETF, specifies in which way OWAMP compliant measurement results can be accessed by OWAMP clients. The other way round OWAMP measurement tasks can be added an managed in the CMT II framework. D. Database The database plays a decisive role in the framework. It stores all measurement tasks and associated results. The database is designed in such a way, that it can be easily extended for future demands and scenarios. Beside measurement task and results data for the user administration and monitoring data of framework components is held in the database. The database is generally divided in five main segments. The user segment is responsible to limit access on the execution of measurement tasks. This can be done in a very fine granular way, so that access can be defined on the level of interfaces of measurement hops. In the database section task all measurement specific data are stored. The necessary traffic information is stored in an individual section of the database. This section stores the traffic models and tracefiles for the traffic generation, see details in section IV. In the hop area data about measurement nodes and network infrastructure is saved. Finally measurement results are located in the results section. E. JADE CMT II uses JADE for the administration and communication of the distributed architecture. JADE is a software

framework fully implemented in Java language. It simplifies the implementation of multi-agent systems through a middleware that complies with the FIPA specifications and through a set of graphical tools that supports the debugging and deployment phases. The agent platform can be distributed across machines (which not even need to share the same OS) and the configuration can be controlled via a remote GUI [11]. With JADE it is possible to centrally manage and distribute agents. Furthermore it is possible to use FIPA interaction protocols [12] for the communication between agents. These interaction protocols assure a standardised communication, so that in the near future it will be possible to integrate measurement agents of other agent-platforms into the CMT II framework. Messages can be transmitted via different message transport protocols (MTP), like for example http. Moreover JADE provides the possibility to have a redundant infrastructure in order to improve reliability. By the extension of JADE with the Lightweight Extensible Agent Platform (LEAP) [13] it is possible to run agents on mobile Java environments down to J2ME-CLDC MIDP 1.0 like PDAs or even cellphones, see figure 2. For IP measurements this signifies a new dimension of measurement scenarios, where mobile networks alone or in combination with fixed networks can be analysed. JADE makes it possible to distribute agents over the network, which allows a centralised management and update of measurement hops. F. Authentication and Security Finally authentication and security are important elements of a comprehensive measurement tool. Authentication and security applies on two layers of the CMT II framework. First in CMT II itself, where access through the GUI can only be granted after user verification. Regarding this point user access can be restricted to results of certain test or to allow the execution of measurement tasks on specific hosts. Second

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A statemodel can be defined, which defines traffic by the number of possible states M and state transition probability matrix A = {aij }, 1 ≤ i, j ≤ M , where aij denotes the state transitionP probability from state i to state j. Furthermore the constraint j=1,...,M aij = 1 is satisfied, as illustrated in example figure 3. Each state is specified trough: • state duration sd • packet send interval si • packet size ss These parameters are not necessarily fixed values. They can be sampled from a uniform, exponential or pareto distribution as well.

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CMT II uses the security features of JADE for authentication, permissions and message integrity. The JADE authentication mechanism is based on the Java authentication and authorization service (JAAS) API that enables the enforcement of differentiated access control on system users. With JADE security features it is possible to restrict the access of measurement hops to the CMT II framework as well as to have differentiated permissions of measurement hops concerning the execution of measurement tasks. Furthermore messages exchanged between agents can optionally be signed and encrypted in order to guarantee message integrity and confidentiality.

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This section deals with the different measurement scenarios of CMT II. It’s important to note that the explained scenarios are possible measurement scenarios, but CMT II is not limited to those scenarios.

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A. Active Measurement 1) Flow Measurement: Flow measurement is one of the most important scenarios with CMT II. This is used to actively generate a data flow and send it across a network. On the receiving side the flow is analysed (e.g. statistical analysis of one-way delay or packet loss) and results are reported to the management layer. In order to allow this analysis the sender puts the sequence number into the packet payload and reports the sender timestamps to the management layer. The management layer correlates the information from the sender and the receiver and stored the results into the CMT II database. The transport protocol can be TCP, TCP No Delay (which is based on the Nagle algorithm), or it can be UDP for connection-less measurements. To study the influences of Differentiated Service (DiffServe) architectures the bits of the DiffServe Code Point (DSCP) can be set arbitrarily. According to the configuration of the measurement task, results are provided at the end of the session and preliminary result are provided after specified aggregation intervals. Additionally key characteristics of every single packet can be stored as raw results in the database. CMT II provides two possibilities for generating a measurement flow.

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IV. M EASUREMENT M ETHODS

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A trace file defines the traffic by a special file which consists of lines, one per packet, which define packet size and time until next packet. After processing all entries execution starts again at the beginning. With the trace file it is possible to define any kind of traffic pattern. The trace file can also be generated out of a tcpdump trace file. 2) Path Discovery: This method is used to get the more information about the network. During flow measurements it makes sense to simultaneously make a path discovery to get into the ”black-box” called network. This is done by making traceroutes and storing results into the database. These result can than be visualized to get an overview of the involved hops. Additionally with this method it is possible to detect routechanges and to analyse these changes.

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In this section we want to discuss a measurement example, which has been created with CMT II. In this scenario we had two measurement points. The sender was at Salzburg Research (Austria) and the receiver at Budapest University of Technology and Economics (Hungary). We measured the perceptual speech quality of an emulated VoIP point–to– point transmission from Salzburg to Hungary. Here, the term emulated means, that we generate network traffic with VoIP characteristics, but without carrying speech in the payload of each packet. However, since we use the extended E–Model for speech quality evaluation, which only takes delay and packet loss patterns into account, this constraint does not really hurt. Consequently, the actual packets are UDP packets with an additional RTP header and 160 Bytes of empty payload. These packets are sent in a 20 ms interval. 4.5 4 MOS

Besides active measurement CMT II allows also passive measurement. In this context passive measurement can be used as a stand alone measurement or in combination with active measurement. By the use of passive measurement it is for example possible to analyse data over different measurement points. CMT II provides three types of passive measurement: 1) Packet Capture: For packet capturing two different methods can be used. First, a measurement hop equiped with a packet capture card (e.g. Endace DAG 3.7G card) can be used for high precision results. This has the advantage, that the DAG card uses high precision time stamps for receiving packets independent of the utilisation of the system. Second, a measurement hop equiped with a standard network interface card using the libpcap 1 can be set in promiscuous mode. Thus allowing to capture packets, but with less precision than the DAG card and the disadvantage of loosing packets under high utilisation [18]. 2) SNMP: Passive measurement can also be done via the simple network management protocol (SNMP). Therefore agents have to be configured to poll SNMP compatible hosts and store the information into the database. With SNMP it is possible to gather any kind of information, even information about the configuration or software version. These information together with the measurement results leads to an overall picture of them measurement and increases the quality of measurement documentation and traceability.

V. M EASUREMENT E XAMPLE

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3) Anomaly Detection: CMT II can also bes used for anomaly detection in IP networks. Therefore passive measurement data, captured as described in the sections IV-B.1, is analysed with different methods. The anomaly detection is based on statistical analysis and unsupervised learning with the focus on the detection of anomalies caused by malicious activities such as Denial of Service attacks or network probes [19].

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3) OWAMP: The one-way active measurement protocol not only defines the exchange of measurement results, furthermore it specifies the procedure of one-way delay measurements [6]. Regarding this point an OWAMP compliant flow is generated by the sender, transmitted over the network and analysed by the receiver. In opposite to the standard OWAMP-clients results are stored in the CMT II database for traceability and documentation. According OWAMP it is possible to combine sender or receiver of different vendors. 4) Perceptual Measurement: CMT II supports a new a new approach of network measurement called perceptual quality. In this new approach not the single network parameter is important, instead an overall quality value is determined. This type of measurement is especially for VoIP (or other multimedia transmissions) very helpful, because it gives a quality rating from the users point of view. At the moment CMT II provides a method based on an modified and extended version of the E-Model [14]–[16] described in [17], which is used to predict the perceptual quality of VoIP transmissions. CMT II not only emulates VoIP by sending out VoIP like flows, but also transmits real audio data, which is stored into the database for further processing, like perceptual evaluation of speech quality (PESQ) with 3rd party tools. For the audio transmission via real-time protocol (RTP) CMT II supports three different audio codecs (G.711, G.723.1, GSM) with variable packet length.

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Fig. 5. Perceptual VoIP speech quality evaluation. Each unit on the x–axis denotes a 10 second interval, in which the corresponding MOS, packet loss and mean delay have been calculated. Concerning speech quality, the MOS can be interpreted as (bad) 0 ≤ MOS ≤ 4.5 (good).

As can bee seen in figure 5, the Mean Opinion Score (MOS) of the perceptual quality decreases significantly at the beginning of the transmission, due to also significant packetloss. The reason for this packet-loss could not be determined an should therefore be investigated in further research.

VI. F URTHER W ORK In this paper the measurement framework CMT II is described. It is mentioned that CMT II is the next development stage of CMToolset, which has been developed since 1997 in different research projects. Also CMT II development is not stopped, instead it is a continuous development process for new measurement methods as well as for new upcoming standards. We hope that our approach of an agent based framework is successful in order to satisfy the community and to encourage more people to use CMT II. Concerning further development the expansion of the data collection mechanisms, especially regarding the collection of information from the lower layers of the OSI model to get a deeper insight into traffic measurements is planned. Furthermore, the export interfaces have to be improved to allow more extensive analysis and the security management has to be extended in order to secure inter–domain measurements. Last but not least, we plan to extend the available traffic models and conduct further tests on mobile devices, like cellphones or PDAs. R EFERENCES [1] J. Corral, G. Texier, and L. Toutain, “End-to-end active measurement architecture in ip networks (saturne),” in Proceedings of PAM2003, La Jolla, CA, USA, April 2003. [2] S. Kalidindi and M. Zekauskas, “Surveyor: An Infrastructure for Internet Performance Measurements,” in Proceedings of INET’99, San Jose, CA, USA, 1999. [3] F. Georgatos et al, “Providing Active Measurements as a Regular Service for ISPs,” in Proceedings of the Passive and Active Measurements Workshop (PAM2001), Amsterdam, NED, April 2001. [4] D. Morato, E. Magana, M. Izal, J. Aracil, F. Naranjo, F. Astiz, and U. Alonso, “ETOMIC: A testbed for universal active and passive measurements,” in Proceedings of Tridentcom 2005, Trento, Italy, February 2005. [5] J. B. Micheel, “Designing a passive measurement and analysis infrastructur for the research community,” in ACM SIGCOMM MineNet05, Philadelphia, USA, August 2005. [6] S. Shalunov, B. Teitelbaum, A. Karp, J. W. Boote, and M. J. Zekauskas, A One-way Active Measurement Protocol (OWAMP), IETF Network working Group Internet Draft, Rev. 14, December 2004. [Online]. Available: http://www.ietf.org/internet-drafts/draft-ietf-ippm-owdp-14. txt [7] MoMe. (2005, October) Mome: Cluster of european projects aimed at monitoring and measurement. [Online]. Available: http: //www.ist-mome.org/ [8] U. Hofmann, T. Pfeiffenberger, and B. Hechenleitner, “One-way-delay measurements with cmtoolset,” in Proceedings of IPCCC 2000, Phonix, USA, February 2000. [9] U. Hofmann, I. Miloucheva, T. Pfeiffenberger, and F. Strohmeier, “Evaluation of architectures for qos analysis of applications in internet environment,” in Proceedings of ICTSM10, Monterey, USA, October 2002. [10] ——, “Active monitoring toolkit for longterm qos analysis in large scale internet,” in Proceedings of IPS Workshop, Budapest, Hungary, March 2004. [11] Telecom Italia Lab. (2005, August) Jade: Java agent development framework. [Online]. Available: http://jade.tilab.com [12] F. Bellifemine, A. Poggi, and G. Rimassa, “Jade - a fipa-compliant agent framework,” in Proceedings of PAAM’99, London, April 1999, pp. 97– 108. [13] F. Bergenti and A. Poggi, “Leap: A fipa platform for handheld and mobile devices,” in ATAL ’01: Revised Papers from the 8th International Workshop on Intelligent Agents VIII. London, UK: Springer-Verlag, 2002, pp. 436–446. [14] ITU-T, Recommendation G.107 - The E-Model, a computational model for use in transmission planning, ITU-T Std., March 2003.

[15] ——, Recommendation G.108 - Application of the e-model: A planning guide., ITU-T Std., May 1999. [16] ——, Recommendation G.113 Appendix I - Provisional planning values for the equipment impairment factor Ie and packet-loss robustness factor Bpl., ITU-T Std., May 2002. [17] T. Fichtel, “Perceptual quality assessment of voip in wlan,” Master’s thesis, Salzburg University of Applied Sciences and Technologies, 2005. [18] L. Deri, “Improving passive packet capture:beyond device polling,” in Proceedings of SANE 2004, Amsterdam, September 2004. [19] R. Kwitt and T. Strohmeier, “Towards Anomaly Detection in Network Traffic by Statistical Means and Machine Learning,” in Proceedings of the 3rd International Workshop on Internet, Performance, Simulation, Monitoring and Measurements, Warsaw, Poland, March 2005.