In tree-based multicast systems, a relatively small number of interior nodes carry the load of forwarding multicast messages. This works well when the interior nodes are highly available, d d cated infrastructure routers but it poses a problem for application-level multicast in peer-to-peer systems. SplitStreamadV esses this problem by striping the content across a forest of interior-nodno# sjoint multicast trees that d stributes the forward ng load among all participating peers. For example, it is possible to construct efficient SplitStream forests in which each peer contributes only as much forwarding bandH d th as it receives. Furthermore, with appropriate content encod ngs, SplitStream is highly robust to failures because a nod e fai ure causes the oss of a single stripe on average. We present thed#' gnand implementation of SplitStream and show experimental results obtained on an Internet testbed and via large-scale network simulation. The results show that SplitStreamd istributes the forward ing load among all peers and can accommod'9 peers with different band0 d capacities while imposing low overhead for forest constructionand maintenance.

mechanism to estimate Internet network distance (i.e., round-trip delay or network hops). Network distance estimation is important in many applications, for example, network-aware overlay construction and server selection. There are several proposals for distance estimation in the Internet but they all suffer from problems that limit their benefit. Most rely on a small set of infrastructure nodes that are a single point of failure and limit scalability. Others use sets of peers to compute coordinates but these coordinates can be arbitrarily wrong if one of these peers is malicious. While it may be reasonable to secure a small set of infrastructure nodes, it is unreasonable to secure all peers. PIC addresses these problems: it does not rely on infrastructure nodes and it can compute accurate coordinates even when some peers are malicious. We present PIC's design, experimental evaluation, and an application to network-aware overlay construction and maintenance.

self-organizing substrate for distributed applications and support powerful abstractions such as distributed hash tables (DHTs) and group communication. However, in most of these systems, lack of control over key placement and routing paths raises concerns over autonomy, administrative control and accountability of participating organizations. Additionally, structured p2p overlays tend to assume global connectivity while in reality, network address translation and firewalls limit connectivity among hosts in different organizations. In this paper, we present a general technique that ensures content/path locality and administrative autonomy for participating organizations, and provides natural support for NATs and firewalls. Instances of conventional structured overlays are configured to form a hierarchy of identifier spaces that reflects administrative boundaries and respects connectivity constraints among networks.

An electronic payment system ideally should provide security, anonymity, fairness, transferability and scalability. Existing payment schemes often lack either anonymity or scalability. In this paper we propose Who-Pay, a peer-to-peer payment system that provides all the above properties. For anonymity, we represent coins with public keys; for scalability, we distribute coin transfer load across all peers, rather than rely on a central entity such as the broker. This basic version of WhoPay is as secure and scalable as existing peer-to-peer payment schemes such as PPay, while providing a much higher level of user anonymity. We also introduce the idea of real-time double spending detection by making use of distributed hash tables (DHT), which further improves the security level of WhoPay. To evaluate how well WhoPay distributes load among peers, we have run simulations with several different configurations. The simulation results show that the majority of the system load is handled by the peers under typical peer availability, indicating that WhoPay should scale well. 1

We present versatile anycast, which allows a service running on a varying collection of nodes scattered over a wide-area network to present itself to the clients as one running on a single node. Providing a single logical address enables the client-side software to preserve the traditional service access model based on single access points. At the same time, the dynamic composition of anycast groups implemented by versatile anycast enables the server-side service infrastructure to evolve and adapt to changing network conditions. We implement versatile anycast using Mobile IPv6, which decouples the logical addresses of mobile nodes from their physical location. We exploit that decoupling to implement logical service addresses that are not bound to any physical nodes, and employ standard MIPv6 mechanisms to dynamically map each such address onto individual service nodes. Our solution enables a service to transparently hand off clients among the service nodes at the network level while preserving optimal routing between the clients and the service nodes. We demonstrate that the overhead of versatile anycasting is very low. In particular, the client-perceived handoff time is shown to be a linear function of the latencies among the client and the service nodes participating in the handoff. 1

Abstract—It has become apparent for quite some time that the Internet has evolved from a network connecting pairs of end-hosts to a substrate for information dissemination. While this shift towards information centric networking has been clearly demonstrated by the proliferation of file sharing and content delivery applications, it has not been reflected in a corresponding shift in network architecture. To address this issue, we designed MultiCache, an information-centric architecture aiming at the efficient use of network resources. MultiCache is based on two primitives: multicast and caching. It exploits overlay multicast as a means for content delivery and takes advantage of multicast forwarding information to locate, in an anycast fashion, nearby caches that have been themselves fed via multicast. We evaluate MultiCache against a widespread file sharing application (BitTorrent) with respect to both network resource consumption and end-user experience. Index Terms—Information centric, content centric, publishsubscribe, peer to peer, multicast, caching I.

Abstract – Peer-to-Peer (P2P) networks and their applications gain increasing importance in today’s Internet, as already today the majority of IP traffic is caused by P2P applications. Since the upcoming of Napster a lot of research has been done in this area producing interesting and promising results. Still, growing demands like less data rate consumption, faster and more reliable search responses and the development of new applications engage many researchers worldwide. In this tutorial we therefore provide an overview about the area of P2P networking, its basic methods and a classification into unstructured and structured P2P networks. However the focus of this work is put on structured P2P networks, for which we explain in detail the most important routing algorithms. Based on this overview we can provide a discussion of the major advantages and disadvantages of the different P2P approaches, focusing especially on the applicability of P2P networks in heterogeneous environments.

Anycasting was introduced to facilitate efficient communication between distributed Internet services and their clients, as it allows client requests to be automatically routed to nearby service instances. However, even though several anycast implementations have been proposed, their various limitations prevent them from being widely adopted by large-scale distributed systems. This paper identifies the key limitations of existing anycast implementations, and proposes how to implement anycast such that all these limitations are addressed without harming the performance of anycast communication. Our solution relies on address-translation capabilities present in modern operating systems. These capabilities have originally been designed for communication with mobile nodes. However, we demonstrate that one can exploit them to implement versatile anycasting at low cost. 1

We consider the problem of content-based routing and dissemination of highly-distributed, fast data streams from multiple sources to multiple receivers. Our target application domain includes real-time, stream-based monitoring applications and large-scale event dissemination. We introduce SemCast, a new semantic multicast approach that, unlike previous approaches, eliminates the need for content-based forwarding at interior brokers and facilitates fine-grained control over the construction of dissemination overlays. We present the initial design of SemCast and provide an outline of the architectural and algorithmic challenges as well as our initial solutions. Preliminary experimental results show that SemCast can significantly reduce overall bandwidth requirements compared to traditional event-dissemination approaches.

The use of SuperPeers has been proposed to improve the performance of both Structured and Unstructured Peer-to-Peer (P2P) Networks. In this paper, we study the performance of Yao-Graph based SuperPeer Topologies for Hierarchical P2P networks. Since a Yao-Graph is defined as a geometric structure, we are using the ”Highways ” proximity clustering and placement scheme to assign geometric co-ordinates to SuperPeers and Peers with respect to the underlying network conditions. Because of the lightweight structure of Yao-Graphs, the resulting hierarchical P2P networks have promising properties with regard to scalability and performance, while still offering the benefits of the P2P approach with regard to resiliency. 1