Daniel Schlosser

Energy Efficient Virtual Network Embedding

Waste of energy due to over-provisioning and over-dimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach.

An Evaluation of QoE in Cloud Gaming Based on Subjective Tests

Cloud Gaming is a new kind of service, which combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users remotely from a data center. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. The end device only needs a broadband internet connection and the ability to display High Definition (HD) video. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for service quality in terms of bandwidth and latency for the underlying network. In this paper we present the results of a subjective user study we conducted into the user-perceived quality of experience (QoE)in Cloud Gaming. We design a measurement environment, that emulates this new type of service, define tests for users to assess the QoE, derive Key Influence Factors (KFI) and influences of content and perception from our results.

Internet access traffic measurement and analysis

The fast changing application types and their behavior require consecutive measurements of access networks. In this paper, we present the results of a 14-day measurement in an access network connecting 600 users with the Internet. Our application classification reveals a trend back to HTTP traffic, underlines the immense usage of flash videos, and unveils a participant of a Botnet. In addition, flow and user statistics are presented, which resulting traffic models can be used for simulation and emulation of access networks.

Gaming in the clouds: QoE and the users’ perspective

Abstract Cloud Gaming is a new kind of service, which combines the successful concepts of Cloud Computing and Online Gaming. It provides the entire game experience to the users remotely from a data center. The player is no longer dependent on a specific type or quality of gaming hardware, but is able to use common devices. The end device only needs a broadband internet connection and the ability to display High Definition (HD) video. While this may reduce hardware costs for users and increase the revenue for developers by leaving out the retail chain, it also raises new challenges for service quality in terms of bandwidth and latency for the underlying network. In this paper we present the results of a subjective user study we conducted into the user-perceived quality of experience (QoE) in Cloud Gaming. We design a measurement environment, that emulates this new type of service, define tests for users to assess the QoE, derive Key Influence Factors (KIF) and influences of content and perception from our results.

ALEVIN - A Framework to Develop, Compare, and Analyze Virtual Network Embedding Algorithms

Network virtualization is recognized as an enabling technology for the Future Internet. Applying virtualization of network resources leads to the problem of mapping virtual resources to physical resources, known as “Virtual Network Embedding” (VNE). Several algorithms attempting to solve this problem have been discussed in the literature, so far. However, comparison of VNE algorithms is hard, as each algorithm focuses on different criteria. To that end, we introduce a framework to compare different algorithms according to a set of metrics, which allow to evaluate the algorithms and compute their results on a given scenario for arbitrary parameters.

Provisioning and Operation of Virtual Networks

In todays Internet, requirements of services regarding the underlying transport network are very diverse. In the future, this diversity will increase and make it harder to accommodate all services in a single network. A possible approach to keep up with this diversity in future networks is the deployment of isolated, custom tailored networks on top of a single shared physical substrate. The COMCON (COntrol and Monitoring of COexisting Networks) project aims to define a reference architecture for setup, control, and monitoring of virtual networks on a provider- and operator-grade level. In this paper, we present the building blocks and interfaces of our architecture.

Throughput Performance of the ActiveMQ JMS Server

Communication among distributed software components according to the publish/subscribe principle is facilitated by the Java messaging service (JMS). JMS can be used as a message routing platform if the subscribers install filter rules on the JMS server. However, it is not clear whether its message throughput is sufficient to support large-scale systems. In this paper, we investigate the capacity of the high performance JMS server implementation ActiveMQ. In contrast to other studies, we focus on the message throughput in the presence of filters and show that filtering reduces the performance significantly. We present a model for the message processing time at the server and validate it by measurements. This model takes the number of installed filters and the replication grade of the messages into account and predicts the overall message throughput for specific application scenarios.

Source traffic characterization for thin client based office applications

A thin client is a small network computer which is used as a remote screen visualizing the output of software applications running on a central server. To provide a seamless service to thin client users the network connection between the client and the server must be dimensioned properly. In this paper we therefore characterize the traffic generated by different types of thin client users when working with popular office applications like Microsoft Word, Excel, or PowerPoint. We analyze the traffic patterns measured in our testbed environment and thus provide a basis for subsequent research studies as well as for administrators to estimate the amount and the characteristics of user generated traffic.

Performance comparison of windows-based thin-client architectures

The basic idea behind thin-client architectures is to run applications on a central server instead of installing them separately on each client. The Windows remote desktop protocol (RDP) and the Citrix presentation server are two well known approaches to separate the location of where the user input is processed from the computer he is actually working on. While both alternatives solve the same problem, they rely on significantly different mechanisms to handle the exchange of user input and screen updates between client and server. In this paper we therefore compare the performance of both protocols under different aspects. In particular, we study the load caused on network layer as well as the satisfaction of the end user with the service quality achieved by the different terminal services. As this performance heavily depends on the current network conditions, we emulate realistic scenarios in a controlled testbed environment and measure the time required for typical office tasks on application layer. As a result, we quantify the Quality-of-Experience (QoE) perceived by the end-user, compare the overhead required by the different available protocols, and unveil their advantages and disadvantages. Our results can be used to decide which protocol to use in which scenario.

Power Consumption Analysis of Data Center Architectures

The high power consumption of data centers confronts the providers with major challenges. However, not only the servers and the cooling consume a huge amount of energy, but also the data center network architecture makes an important contribution. In this paper, we introduce different data center architectures and compare them regarding their power consumption. The results show that there are some differences which should not be neglected and that with only minor modifications of the architecture, it is possible to save a huge amount of energy.