Contributions published at Communication Systems Group (Burkhard Stiller)

null

The increasing assortment of devices with IP connectivity contributes to the high popularity of video sharing over the Internet. High traffic generated by such applications at the source can be better distributed using a peer-to-peer overlay, since every user forwards information to other users. Current implementations target either live or on demand video streaming. LiveShift is an application that combines both approaches. While video is transmitted through the peer-to-peer network in a live fashion, all peers participate in a distributed storage. This adds ability to replay time-shifted streams from other peers in a distributed and scalable manner. For the demonstration, a decentralized network is used, with peers running on EMANICSLab nodes and notebook computers.

null

The storage of IP traffic traces increasingly grows more complex, since data flows tend to increase largely over time. Network operator’s backbones generate each day hundreds of Gigabyte of IP flow records that need to be stored and analyzed. Handling such amount of data requires a high-performance hardware and software. One way to leverage performance requirements of a storing and analysis of traffic data is to design a distributed platform to replace centralized solutions existing today. This paper designs a scalable storage platform for IP flow records. The evaluation of the implemented prototype shows that such an approach can offer a good and practical solution for storing and retrieving high amounts of IP flow records.

null

null

null

null

null

The emergence of peer-to-peer systems poses a challenge for network providers, in particular the Internet Service Providers (ISPs). Since the routing in such peer-to-peer applications works unaware of the underlying topology, the chosen paths are not always optimal for the ISPs - on the contrary, a lot of unnecessary routes and costly connections are a consequence. ISPs have to pay for certain connections that leave their network and enter the network of another provider. By favouring intradomain traffic over the costly interdomain traffic, the ISPs have the potential to save resources and costs. Different universities and companies formed a project called SmoothIT which set itself the goal to optimise these shortcomings. The critical success factor to overcome these problems was co-operation as opposed to standalone, individual efforts to optimise the network by itself. By creating incentives for all participants the aim is to facilitate collaboration and information exchange in order to find shorter and less expensive routes. A possible architecture to enhance the communication between the ISPs and the application providers, bases on a SmoothIT information system (SIS) that shares information with the applications through a web service. The application can then choose an ideal path to route the traffic that stays within the borders of the ISP as much as possible. For the end users this results in faster download, reduced delay times and a better service quality.

Overlay applications, such as peer-to-peer file sharing systems, are very popular today and create a major share of the total traffic on the Internet. These applications typically do not use optimization mechanisms to increase traffic locality in their overlay networks. The large number of long distance inter-domain connections lead to high traffic costs to network providers, such as ISPs. In this thesis the Preference Information System for Overlay Networks (PISON), an incentive-based cooperative economically-driven traffic management mechanism, is presented. PISON allows overlay applications to optimize their overlay topology according to economic preference and network locality. This leads to the reduction of traffic cost for network providers and increased overlay application performance through improved overlay connection locality. PISON server and client prototypes are implemented and evaluated in a peer-to-peer video streaming application scenario on an international European research network. Results show, that PISON improves traffic locality of the overlay application by 77% in average in the evaluation scenario, leading to a reduction of traffic cost for network providers and allowing for application performance improvement.

null

null

The continually and rapidly changing communications possibilities and informational aspects that affect the marketplace mean that if companies are going to be able to survive they have to readily adapt to these new developments and challenges. To remain competitive, companies have to give fresh consideration to their underlying technological aspects and organizational forms. Mobile grids present an opportunity for companies to meet the needs of an increasingly nomadized society, as they enable users to access complex services in a mobile and dynamic manner, and without complications or interference. Mobile dynamic virtual organizations (MDVOs) are the form of organization that enables companies to participate dynamically in cooperative networks as desired, while still guaranteeing user mobility. The best way to implement MDVOs is by using a mobile grid. It is within this mobile grid and MDVO environment that this thesis has the task of ascertaining the economic potential for each individual actor. For this purpose, the aquaculture industry in Norway has been chosen as the application domain. The thesis analyses two scenarios relating to the commercialization of mobile grid services, and it will develop this in a three-tiered manner. One the one hand, the basis for a business plan for all the actors will be given, with cooperation agreements providing a foundation. In this connection, the i* methodology is one of the principal tools used in the analysis, On the other hand, complex taris are elaborated for all mobile grid services. Finally, each individual actor will be analysed and assessed from a financial point of view. The Monte Carlo Simulation has been used as the basis for all calculations, and for those relating to complex taris in particular.

The newly developed approach on token-based payments introduces an integration of payments with current schemes for Identity Federations based on SAML. This new design utilizes an established federation infrastructure as well as its protocols. Only relevant mechanisms to support the payment on the federation infrastructure level are extended.

Peer-to-peer (P2P) applications have the potential to improve net- work scalability and create a community in which resources are under the shared responsibility of its members. Current popular solutions target specific applications, such as file sharing and VoIP (Voice-over-IP), but important challenges prevent P2P technology from having wider acceptance in other services. Overwhelmed by interdomain traffic generated by P2P applications that build overlays asymmetric to the network topology, ISPs offer at a home user level only connections with asymmetric bandwidth. This measure efficiently hinders P2P applications. This paper introduces a new incentive model for overlay applications and ISPs to collaborate and to create at the same time a win-win situation. The approach combines two principles: (1) ISPs and P2P applications communicate to correct overlay asymmetry and (2) ISPs diminish bandwidth asymmetry by providing users additional bandwidth reserved for intradomain traffic.

Fully decentralized peer-to-peer (P2P) systems do not have a central control mechanism. Thus, different forms of control mechanisms are required to deal with selfish peers. One type of selfish behavior is the consumption of resources without providing sufficient resources. Therefore, incentive schemes encourage peers to share resources while punishing selfish peers. A well-known example of an incentive scheme is Tit-for-Tat (TFT), as used in BitTorrent. With this scheme, a peer can only consume as much resources as it provides. TFT is resilient to collusion due to relying on private histories only. However, TFT can only be applied to peers with direct reciprocity. This paper presents a private and shared history (PSH) based incentive mechanism, which supports transitive relations (indirect reciprocity). Furthermore, it is resilient to collusion and it combines private and shared histories in an efficient manner. The PSH approach uses a shared history for identifying transitive relations. Those relations are verified using private histories. Simulations show that the PSH mechanism has a higher transaction success ratio than TFT.

null

null