Thilo Ewald

Capturing Cloud Computing Knowledge and Experience in Patterns

The industry-driven evolution of cloud computing tends to obfuscate the common underlying architectural concepts of cloud offerings and their implications on hosted applications. Patterns are one way to document such architectural principles and to make good solutions to reoccurring (architectural) cloud challenges reusable. To capture cloud computing best practice from existing cloud applications and provider-specific documentation, we propose to use an elaborated pattern format enabling abstraction of concepts and reusability of knowledge in various use cases. We present a detailed step-by-step pattern identification process supported by a pattern authoring toolkit. We continuously apply this process to identify a large set of cloud patterns. In this paper, we introduce two new cloud patterns we identified in industrial scenarios recently. The approach aims at cloud architects, developers, and researchers alike to also apply this pattern identification process to create traceable and well-structured pieces of knowledge in their individual field of expertise. As entry point, we recap challenges introduced by cloud computing in various domains.

Enabling high-speed and extensible real-time communications monitoring

The use of the Internet as a medium for real-time communications has grown significantly over the past few years. However, the best-effort model of this network is not particularly well-suited to the demands of users who are familiar with the reliability, quality and security of the Public Switched Telephone Network. If the growth is to continue, monitoring and real time analysis of communication data will be needed in order to ensure good call quality, and should degradation occur, to take corrective action. Writing this type of monitoring application is difficult and time consuming: VoIP traffic not only tends to use dynamic ports, but its real-time nature, along with the fact that its packets tend to be small, impose non-trivial performance requirements. In this paper we present RTC-Mon, the Real-Time Communications Monitoring framework, which provides an extensible platform for the quick development of high-speed, real-time monitoring applications. While the focus is on VoIP traffic, the framework is general and is capable of monitoring any type of real-time communications traffic. We present testbed performance results for the various components of RTC-Mon, showing that it can monitor a large number of concurrent flows without losing packets. In addition, we implemented a proof-of-concept application that can not only track statistics about a large number of calls and their users, but that consists of only 800 lines of code, showing that the framework is efficient and that it also significantly reduces development time.

Protecting SIP-Based Networks and Services from Unwanted Communications

In recent times, SIP-based communication systems have become more and more popular (e.g., in open networks, NGN, IMS, etc.). With continuously dropping cost for the usage of such systems (e.g., VoIP, IM, IPTV), many researchers anticipate the amount of unsolicited communication within the network to reach an alarming high level in the near future. Thus, protection of such systems is needed to counter this threat. We present a holistic protection framework for SIP based infrastructures and describe the most recent enhancements of the system.

Experiences with large-scale operational trials of ALTO-enhanced P2P filesharing in an intra-ISP scenario

Application Layer Traffic Optimization (ALTO) has recently gained attention in the research and standardisation community as a way for a network operator to guide the peer selection process of distributed applications by providing network layer topology information. In particular P2P applications are expected to gain from ALTO, due to the many connections peers form among each other, often without taking network layer topology information into account. In this paper, we present results of an extensive intra-ISP trial with an ALTO-enhanced P2P filesharing software. In summary, our results show that—depending on the concrete setting and on the distribution of upload capacity in the network—ALTO enables an ISP to save operational costs significantly while not degrading application layer performance noticeably. In addition, based on our experience we are able to give advice to operators on how to save costs with ALTO while not sacrificing application layer performance at all.