In the context of virtualization and cloud computing, a currently interesting topic is the movement of network functions into the cloud. Since these Virtualized Network Functions have high performance and availability requirements, the placement and resilient deployment of these functions are important issues. In this paper, we present a real-world mechanism implemented for OpenStack that supports arbitrary placement functions for performance optimization and resilience provisioning. In addition, we provide an example of how this mechanism can be used in practice.

Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer-related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches—caches already available on the market and caches expected to become available in the future—can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Motivated by our findings, we propose a proximity-aware peer-selection mechanism that avoids the increase of the transit traffic and improves the cache efficiency. We support the analytical results by extensive simulations and experiments with real BitTorrent clients.

P2P applications attract a lot of users and generate the dominant portion of the overall traffic in the Internet today. On the one hand, this large amount of traffic results in high operational costs for ISPs, mainly because of expensive interdomain connections. On the other hand, the performance of P2P applications is constricted by suboptimal peer selection or by bandwidth limitations of ISPs. To overcome these problems, the collaboration of P2P applications and ISPs is desirable, where locality promotion is one of the possible approaches. In this paper, we propose a locality promotion mechanism based on BGP routing information of an ISP and show by simulations that it can reduce inter-domain traffic, prefers shorter connections and peering links over transit links while P2P applications can achieve a better performance as well.

P2P streaming has attracted much attention recently with promises for higher revenues and better load distribution. Still, the majority of P2P video streaming systems today employ the one-size-fits-all concept where the same video bit-rate is offered to all users. Here the promising H.264/Scalable Video Coding (SVC) standard is seen as a necessity in not only supporting heterogeneous resources, but also in reducing the impact of P2P dynamics on the perceived Quality-of-Experience (QoE). In this demonstration we present our streaming application that uses SVC to adapt to different user requirements and resources. The application employs a novel QoE- aware layer selection algorithm that maximizes flexibility through SVC while taking impact on QoE into consideration.

Peer-to-peer file-sharing systems are responsible for a significant share of the traffic between Internet service providers (ISPs) in the Internet. In order to decrease their peer-to-peer related transit traffic costs, many ISPs have deployed caches for peer-to-peer traffic in recent years. We consider how the different types of peer-to-peer caches - caches already available on the market and caches expected to become available in the future - can possibly affect the amount of inter-ISP traffic. We develop a fluid model that captures the effects of the caches on the system dynamics of peer-to-peer networks, and show that caches can have adverse effects on the system dynamics depending on the system parameters. We combine the fluid model with a simple model of inter-ISP traffic and show that the impact of caches cannot be accurately assessed without considering the effects of the caches on the system dynamics. We identify scenarios when caching actually leads to increased transit traffic. Our analytical results are supported by extensive simulations and experiments with real BitTorrent clients.

Locality-awareness is considered as a promising approach to increase the efficiency of content distribution by peer-to-peer (P2P) networks, e.g., BitTorrent. It is intended to reduce the inter-domain traffic which is costly for Internet service providers (ISPs) and simultaneously increase the performance from the viewpoint of the P2P users, i.e, shorten download times. This win-win situation should be achieved by a preferred exchange of information between peers which are located closely to each other in the underlying network topology. A set of studies shows that these approaches can lead to a win-win situation under certain conditions, and to a win-no lose situation in most cases. However, the scenarios used assume mostly homogeneous peer distributions and that all peers have the same access speed. This is not the case in practice according to several measurement studies. Therefore, we extend previous work in this paper by studying scenarios with real-life, skewed peer distributions and heterogeneous access bandwidths of peers. We show that even a win-no lose situation is difficult to achieve under those conditions and that the actual impact for a specific peer depends heavily on the used locality-aware peer selection and the concrete scenario. Therefore, we conclude that current proposals need to be refined so that users of P2P networks can be sure that they also benefit from their use. Otherwise, a broad acceptance of the concept of locality-awareness in the user community of P2P networks will not take place.

Peer-to-Peer (P2P) systems gained popularity and are responsible for a large share of today's Internet traffic. Nevertheless, their dynamic nature and the intended lack of control through central instances make their behavior unpredictable and, therefore, it is difficult to achieve a high level of Quality-of-Service for P2P traffic. Thus, peers are themselves responsible for dealing with these issues by applying so-called self-organization mechanisms to deal with their heterogeneity, unpredictable behavior, and asymmetric resources. This paper discusses and classifies relevant self-organizing aspects of P2P systems, including metrics and mechanisms. Hereby, the key focus is in better understanding on how such self-organizing mechanisms - originally designed to improve the performance of P2P overlays - affect the underlying Internet infrastructure.

Locality promotion in P2P content distribution networks is currently a major research topic. One of the goals of all discussed approaches is to reduce the interdomain traffic that causes high costs for ISPs. However, the focus of the work in this field is generally on the type of locality information that is provided to the overlay and on the entities that exchange this information. An aspect that is mostly neglected is how this information is used by the peers. In this paper, we consider the predominant approach of Biased Neighbor Selection and compare it with Biased Unchoking, which is an alternative locality aware peer selection strategy that we propose in this paper. We show that both mechanisms complement each other for the BitTorrent file sharing application and achieve the best performance when combined.

Introducing location-awareness in overlay networks allows for a higher efficiency of the offered services, e.g., shorter search times or higher throughput. This is especially important for business applications supported by overlays. In this paper, we will illustrate how such an increase in efficiency causes congestion in an otherwise well-dimensioned locality-aware overlay using a Distributed Hash Table (DHT). In particular, we will use a Vertical Handover (VHO) support system using a Pastry substrate as an example. We will describe the occuring congestion problem and identify the underlying reasons. Thus, we describe the basic trade-off between efficiency and load-inequality. Furthermore, we introduce a solution for the specific issue observed, and conduct a performance evaluation identifying the major influence factors and optimization potential for future work.

Vertical handovers (VHO) are expected to be a key feature in Beyond 3G (B3G) networks. This paper presents a CAN-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to retrieve rapidly the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability. We show by means of simulation the efficiency and the scalability of our approach in comparison to a standard CAN implementation

Vertical handovers (VHO) are expected to be a key feature in beyond 3G (B3G) networks. This paper presents and evaluates a Pastry-based P2P overlay network for supporting vertical handover in B3G networks. The P2P overlay is used to quickly locate attachment points (APs) for mobile entities and to retrieve rapidly the configuration and coverage information of these APs. The advantage of the P2P-based solution is its distributed nature, its scalability, and its self-organizing capability. The performance of the P2P-based VHO support architecture is evaluated in terms of the search time for APs, the scalability of the algorithm, and for homogenous and heterogeneous network layouts. In addition, the solution is compared with the conventional client-server approach

Classical admission control approaches take either descriptor or measurement based information about the traffic into account without relating them to each other. We propose a experience-based AC (EBAC) which uses an empirical percentile of the effective reservation utilization to determine a suitable overbooking factor. In this paper, we show the impact of different measurement time scale resolutions and different quantiles on the performance of the system. We propose aging mechanisms for statistic collection to make the system adaptive to traffic mixes that change over time. We illustrate their effectiveness by simulation results.