Julius Rückert

PeerfactSim.KOM: A simulation framework for Peer-to-Peer systems

Since P2P systems have become popular in the late nineties, simulation of these systems has always been a preferable method of performance evaluation. Simulations facilitate the development and evaluation of new protocols and mechanisms, while enabling a comparison of existing solutions. In this paper, we present PeerfactSim.KOM, a discrete-event P2P simulator that is suitable for a wide range of varying scenarios in the area of P2P. It consists of a layered architecture, provides a broad selection of P2P protocols for the modeled layers, and eases the implementation of new components through its modular design. In addition, the simulator provides helpful tools to configure and evaluate a simulation scenario.

Position Paper: Software-Defined Network Service Chaining

Network service chaining allows composing services out of multiple service functions. Traditional network service functions include, e.g., firewalls, TCP optimizers, web proxies, or higher layer applications. Network service chaining requires flexible service function deployment models. Related work facilitating service chaining include, e.g., the network service header proposal discussed at the IETF or the complementary work on network function virtualization (NFV) at ETSI. This position paper presents a high-level concept and architecture to enable service chaining using Software Defined Networking (SDN), specifically OpenFlow in a telecommunication environment. The paper discusses required functionalities, challenges, and testbed aspects to implement and test such an approach. Finally, the set of implemented service functions and management interfaces are highlighted to demonstrate the approach as a proof of concept for a selection of relevant use cases.

Simonstrator: simulation and prototyping platform for distributed mobile applications

The increasing market penetration of mobile devices, such as smartphones and tablets, poses additional challenges on the design of distributed systems. Due to the heterogeneous environment consisting of both, mobile and fixed devices, a multitude of effects on different scales need to be considered. Microscopic effects, such as an individual users interaction with the device, as well as macroscopic effects, such as scalability with the number of users have an impact on the systems performance. The combined evaluation of micro- and macroscopic effects requires both, simulations and prototypical deployments. Furthermore, insights obtained through prototypes during user studies can lead to refined protocols and algorithms, thereby contributing to the overall design process. To enable parallel assessment of micro- and macroscopic effects, we propose the Simonstrator platform, consisting of a lightweight framework for the development and instrumentation of distributed systems as well as runtime environments for (i) the interaction with common simulators, (ii) the deployment on testbeds, and (iii) Android devices. The platform is specifically targeted towards distributed systems for heterogeneous scenarios, considering mobile and fixed networks. We show sample simulations and prototypical deployments of two exemplary use cases: a live video streaming system and a middleware for augmented reality games, highlighting different evaluation goals and environments supported by the proposed Simonstrator platform.

Software-Defined Multicast for Over-the-Top and Overlay-based Live Streaming in ISP Networks

The increasing amount of over-the-top (OTT) live streams and the lack of global network layer multicast support poses challenges for a scalable and efficient streaming over the Internet. Content Delivery Networks (CDNs) help by delivering the streams to the edge of almost every Internet Service Provider (ISP) network of the world but usually also end there. From there on, the streams are to be delivered to the clients using IP unicast, although an IP multicast functionality would be desirable to reduce the load on CDN nodes, transit links, and the ISP infrastructure. IP multicast is usually not available due to missing control and management features of the protocol. Alternatively, Peer-to-Peer (P2P) mechanisms can be applied to extend the overlay multicast functionality of the CDN towards the clients. Unfortunately, P2P only improves the situation for the CDN but makes it more challenging for the ISP as even more unicast flows are generated between clients inside and outside the ISP network. To tackle this problem, a Software-Defined Networking-based cross-layer approach, called Software-Defined Multicast (SDM), is proposed in this paper, enabling ISPs to offer network layer multicast support for OTT and overlay-based live streaming as a service. SDM is specifically tailored towards the needs of P2P-based video stream delivery originating from outside the ISP network and can easily be integrated with existing streaming systems. Prototypical evaluations show significantly improved network layer transmission efficiencies when compared to other overlay streaming mechanisms, down to a level as low as for IP multicast, at linearly bounded costs.

Quality adaptation in p2p video streaming based on objective qoe metrics

The transmission of video data is a major part of traffic on todays Internet. Since the Internet is a highly dynamic environment, quality adaptation is essential in matching user device resources with the streamed video quality. This can be achieved by applying mechanisms that follow the Scalable Video Coding (SVC) standard, which enables scalability of the video quality in multiple dimensions. In SVC-based streaming, adaptation decisions have long been driven by Quality of Service (QoS) metrics, such as throughput. However, these metrics do not well match the way human users perceive video quality. Therefore, in this paper, the classical SVC-based video streaming approach is expanded to consider Quality of Experience (QoE) for adaptation decisions. The video quality is assessed using existing objective techniques with a high correlation to the human perception. The approach is evaluated in context of a P2P-based Video-on-Demand (VoD) system and shows that by making peers favor always layers with a high estimated QoE but not necessarily high bandwidth requirements, the performance of the entire system can be enhanced in terms of playback delay and SVC video quality by up to 20%. At the same time, content providers are able to reduce up to 60 of their server costs, compared to the classical QoS-based approach.

Flexible traffic management in broadband access networks using Software Defined Networking

Over the years, the demand for high bandwidth services, such as live and on-demand video streaming, steadily increased. The adequate provisioning of such services is challenging and requires complex network management mechanisms to be implemented by Internet service providers (ISPs). In current broadband network architectures, the traffic of subscribers is tunneled through a single aggregation point, independent of the different service types it belongs to. While having a single aggregation point eases the management of subscribers for the ISP, it implies huge bandwidth requirements for the aggregation point and potentially high end-to-end latency for subscribers. An alternative would be a distributed subscriber management, adding more complexity to the management itself. In this paper, a new traffic management architecture is proposed that uses the concept of Software Defined Networking (SDN) to extend the existing Ethernet-based broadband network architecture, enabling a more efficient traffic management for an ISP. By using SDN-enabled home gateways, the ISP can configure traffic flows more dynamically, optimizing throughput in the network, especially for bandwidth-intensive services. Furthermore, a proof-of-concept implementation of the approach is presented to show the general feasibility and study configuration tradeoffs. Analytic considerations and testbed measurements show that the approach scales well with an increasing number of subscriber sessions.

Demo: Software-Defined Network Service Chaining

Network Function Virtualization is a promising approach for network operators to allow moving network functions from hardware appliances to a pure software-based solution. In combination with software-defined networking concepts, this also allows for flexible service chaining approaches. In this paper, a proof-of-concept implementation of a recently proposed fully software-based service chaining approach with network service function isolation is presented. The prototype runs on standard hardware and includes a set of exemplary network functions to show the general feasibility of the approach. Furthermore, it shows the application of the high-level API of the system by using it to integrate an operator and a customer self-service portal. The demonstration setup comprises real mobile devices and runs on an OpenFlow testbed using state-of-the-art hardware switches.

Towards the Description and Execution of Transitions in Networked Systems

Today’s distributed systems have to work in changing environments and under different working conditions. To provide high performance under these changing conditions, many distributed systems implement adaptive behavior. While simple adaptation through parameter tuning can only react to a limited range of conditions, a switch between different mechanisms at runtime enables broader adaptivity. However, distributed systems that switch mechanisms at runtime lack a clear abstraction for the adaptive behavior and, thus, usually interleave the adaptation and actual application logic. This leads to complex and error-prone systems that are hard to maintain and not easy to extend.

TOPT: Supporting flash crowd events in hybrid overlay-based live streaming

Recent studies show that an increasing number of over-the-top live streams is delivered over the Internet. For the delivery of those streams, the dynamically changing and potentially large number of users imposes a major challenge. Flash crowds, where the number of users multiplies or significantly drops in a very small time frame, can cause serious degradations in the streaming performance. Due to the missing support for global network-layer multicast, overlay-based approaches have been broadly studied, showing that, with relaxed time constraints, they can scale well with the number of users. Yet, to support flash crowds, scaling has to happen quickly to keep up also with rapidly changing populations. Only a few approaches exist that focus on this aspect by influencing the streaming topology and, so far, it is not clear if and how these mechanisms can be applied to state-of-the-art hybrid streaming systems. Therefore, in this paper, TOPT is proposed, integrating new as well as existing mechanisms in a common framework. The evaluation shows that the streaming topology, indeed, plays a major role during flash crowds. The lightweight and decentralized tree-forming and topology optimization mechanisms of TOPT, combined with tracker extensions to attach new peers in batches, greatly help improving the streaming performance in terms of reduced playback interruptions by more than 60% and slight reduction in communication overhead at an acceptable increase in average startup delays by 24%.

RASP: Using OpenFlow to push overlay streams into the Underlay

Internet video streaming causes the second largest transfer volume and is the second fastest growing application class in Internet traffic analysis [3]. In this context, also the streaming of live content becomes increasingly relevant as more traditional broadcasters start delivering content over the Internet. Today, live video streaming services rely on IP-unicast delivery or closed IP-multicast systems inside single administrative domains. Approaches such as Content Delivery Networks (CDNs) are used to improve the unicast delivery of content. They usually end at the edge of the residential broadband access Internet Service Provider (ISP) networks that connect end users to the Internet. For live content delivery, network layer multicast would be desirable for ISPs as well as content providers to reduce the load due to parallel unicast connections for the same content. Because of the well-known drawbacks and limitations of IP-multicast [2], however, network layer multicast support is usually not available.