Philipp Svoboda

Traffic Analysis and Modeling for World of Warcraft

The popularity of MMOGs (massively multiplayer online games) has grown fast. This new type of online games uses a different type of protocol and has other limitations to delay and packet loss than the classical well established games like FPSs (first person shooters). This paper focuses on the traffic patterns generated by a MMOG named WoW (World of Warcraft). We analyzed IP layer information like packet size and rate from network traces and user level information like session durations. Finally we present a simple synthetic traffic generator for WoW traffic clients.

Users in cells: A data traffic analysis

We present a large-scale cell based measurement analysis of the user behavior in a live operational HSDPA network. The motivations are: first, to understand the statistical properties of users in cells for refining network planning procedures; and second, to provide realistic traffic models for simulations of cellular packet-oriented networks. We provide an analysis of mean cell load over daytime, as well as models for short-term cell load in terms of user activity and throughput. Furthermore, an evaluation of user-sessions with respect to duration and mean throughput is given. Our findings lead to four different models reflecting realistic user-traffic load of cellular networks. To verify the concept we present respective simulations which investigate multiuser-scheduling in an LTE-network. They show that conventional simulation settings can lead to an overestimation of performance.

Empirical study of subjective quality for Massive Multiplayer Games

Online gaming is a member of the real time interactive multimedia services. This service suffers from all impairments on the networking layer that increase the latency, respectively the responsiveness. The quality of service (QoS) of online gaming is becoming an important issue due to a massive increase of online games (Half-life, War-craft) with a significant player community. The purpose of this project is to investigate the impact of network impairments (delay, jitter) on the perceived QoS. We hereby focus on massively multiplayer online games (MMOG), due to their amount of active users and their popularity. The initial step is to develop a test setup for subjective quality evaluation for MMOG games. The final outcome of this paper is to propose a QoS metric for online gaming.

Measured WEB Performance in GPRS, EDGE, UMTS and HSDPA with and without Caching

In this paper we present results from a measurement campaign evaluating the web performance of different mobile Internet access technologies with and without caching. We measured in GPRS, EDGE, UMTS and HSDPA radio access networks of a mobile operator in Austria. The operator has implemented a web-proxy for performance improvement. To evaluate the impact on the different technologies we ran the setup with and without the web-proxy. We defined the download time of web pages as the performance index for our work. We developed a tool to capture this parameter and derived the index for a set of web sites frequently used by the customers in the network. Beginning with an over-all comparison we will present detailed analysis for special cases. We evaluated the impact of the proxy system to different site configurations using the performance index. Finally we compared the performance numbers for HTTP with results collected from FTP transfers.

Dissecting 3G uplink delay by measuring in an operational HSPA network

Users expect mobile Internet access via 3G technologies to be comparable to wired access in terms of throughput and latency. HSPA achieves this for throughput, whereas delay is significantly higher. In this paper we measure the overall latency introduced by HSUPA and accurately dissect it into contributions of USB-modem (UE), base station (NodeB) and network controller (RNC). We achieve this by combining traces recorded at each interface along the data-path of a public operational UMTS network. The actively generated sample traffic covers real-time applications. Results show the delay to be strongly dependent on the packet size, with random components depending on synchronization issues. We provide models for latency of single network entities as well as accumulated delay. These findings allow to identify optimum settings in terms of low latency, both for application and network parameters.

Diagnosis of capacity bottlenecks via passive monitoring in 3G networks: An empirical analysis

In this work we address the problem of inferring the presence of a capacity bottleneck from passive measurements in a 3G mobile network. The study is based on one month of packet traces collected in the UMTS core network of mobilkom austria AG & Co KG, the leading mobile telecommunications provider in Austria, EU. During the measurement period a bottleneck link in the UMTS core network was revealed and removed, therefore the traces enable the accurate analysis and comparison of the traffic behavior in the two network conditions: with and without a capacity bottleneck. Two approaches to bottleneck detection are investigated. The first one is based on the signal analysis of the marginal rate distribution of the traffic aggregate along one day cycle. Since TCP-controlled traffic dominates the overall traffic mix, the presence of a bottleneck strains the aggregate rate distribution and compresses it against the capacity limit during the peak hour. The second approach is based on the analysis of several TCP performance parameters, e.g. estimated frequency of retransmissions. Such statistics are unstable due to the presence of few top users, but this effect can be counteracted with simple filtering methods. Both approaches are validated via simulations. Our results show that both approaches can be used to provide early warning about future occurrences of capacity bottlenecks, and can complement other existing monitoring tools in the operation of a production network.

Traffic monitoring and analysis in 3G networks: lessons learned from the METAWIN project

A 3G network is a magnificently complex object embedded in a highly heterogeneous and ever-changing usage environment. It combines the functional complexity of the wireless cellular paradigm with the protocol dynamics of TCP/IP networks. Understanding such an environment is more urgent and at the same time more difficult than for legacy 2G networks. Continuous traffic monitoring by means of an advanced system, coupled with routine expert-driven traffic analysis, provides an in-depth understanding of the status and performances of the network as well as of the statistical behaviour of the user population. Such knowledge allows for a better engineering and operation practice of the whole network, and specifically the early detection of hidden risks and emerging troubles. Furthermore, the exploitation of certain TCP/IP dynamic behaviour, particularly the TCP control-loop, coupled with information extracted from the 3GPP layers, provides a cost-effective means to monitor the status of the whole network without requiring access to all network elements. In this article the main lessons are summarized learned from a two-year research activity on traffic monitoring and analysis on top of an operational 3G network.Ein 3G-Mobilfunknetz stellt ein extrem komplexes Gebilde dar, das in ein stark heterogenes und ständig wechselndes Umfeld eingebettet ist. In ihm werden komplexe Funktionen der Mobilfunkübertragung mit TCP/IP-Protokollen verbunden. Ein tiefes Verständnis dieses Systems ist dringend erforderlich, aber sehr schwierig im Vergleich zu vorhandenen 2G-Netzen. Nur die kontinuierliche Beobachtung dieses modernen Übertragungssystems erlaubt es, sowohl die Leistungsfähigkeit des Netzes zu verstehen als auch das statistische Benutzerverhalten zu interpretieren. Die daraus gewonnenen Erkenntnisse begünstigen sowohl eine verbesserte Netzplanung als auch einen optimalen Betrieb und gestatten es darüber hinaus, verborgene Risiken und vorhandene Schwierigkeiten sehr früh zu erkennen. Insbesondere erlaubt die Beobachtung bestimmter TCP/IP-Dynamik gemeinsam mit der Information, die aus den 3GPP-Schichten gewonnen wird, eine kostengünstige Möglichkeit, den Zustand des Gesamtnetzes zu erfassen ohne jedes Einzelelement des Netzes zu erfassen. In diesem Artikel sind die wesentlichen Erkenntnisse zusammengefasst, die in Folge eines zweijährigen Forschungsprojektes zur Beobachtung und Analyse eines 3G-Mobilfunknetzes gewonnen wurden.

Time synchronization performance of desktop computers

Time synchronization is a vital requirement for various applications. Especially the synchronization of desktop computers to the Coordinated Universal Time (UTC) yields numerous use cases, such as distributed measurements. Several solutions address this need, at different levels of price and accuracy. In this work we evaluate on the achievable precision in time synchronization of a desktop PC, for example, assisted by a low-budget GPS receiver. This is achieved by a novel measurement setup, which is comparing the software synchronized internal clock of the PC to a rubidium frequency standard. Our results show, that the synchronization offsets of the software clocks of all tested PCs have positive mean (time lag) in the order of 10 µs. The respective standard deviation is typically an order of magnitude lower. Thereby the unknown interrupt latency is the limiting factor for the accuracy. With this work we show that today (2011) 10 µs of precision can be achieve at very low cost.

Traffic generation application for simulating online games and M2M applications via wireless networks

In this paper we present results of traffic modeling and simulation of multiplayer real-time games and M2M applications using TCP protocol over Telekom Serbia HSPA mobile network, performed within the FP7 LOLA project. In this experimentation, the RTT (Round Trip Time) and cell statistics are analysed. For this purpose, a traffic generation application is developed for Android phones to generate traffic pattern for emerging Machine Type Communication and online multiplayer games in mobile wireless network for different offset of tests. Application is activated by setting the corresponding parameters related to desired test case, i.e. duration of testing, size and frequency of the data packets that the application sends to the server. The main goal of the cell statistic analysis is to evaluate potential impact of additional simulated traffic in view of increasing data-centric users on the performance of mobile wireless radio network.

Modeling randomness in network traffic

A continuous challenge in the field of network traffic modeling is to map recorded traffic onto parameters of random processes, in order to enable simulations of the respective traffic. A key element thereof is a convenient model which is simple, yet, captures the most relevant statistics. This work aims to find such a model which, more precisely, enables the generation of multiple random processes with arbitrary but jointly characterized distributions, auto-correlation functions and cross-correlations. Hence, we present the definition of a novel class of models, the derivation of a respective closed-form analytical representation and its application on real network traffic. Our modeling approach comprises: (i) generating statistical dependent Gaussian random processes, (ii) introducing auto-correlation to each process with a linear filter and, (iii) transforming them sample-wise by real-valued polynomial functions in order to shape their distributions. This particular structure allows to split the parameter fitting problem into three independent parts, each of which solvable by standard methods. Therefore, it is simple and straightforward to fit the model to measurement data.