Live broadcast over a peer-to-peer (P2P) network imposes a unique set of challenges to a digital rights management (DRM) system. Highly correlated service request arrivals at the start of a live event require peak-load provisioning if clients acquire licenses at playback time. Distributing the license management load across a P2P network requires the digital rights management system to ensure the integrity of both digital rights, the protection of client privacy and, at the same time, system scalability. In this paper we describe the requirements imposed on a digital rights management system in distributing live broadcast over a P2P network and present our design of such a system to meet the above challenges. We discuss the system's operation under a number of threat models and how to extend the system to further improve scalability and support network digital video recording (DVR). We close the paper after presenting some scalability results collected from a production P2P live broadcast network using our DRM design.

Live broadcast over a P2P (peer-to-peer) network imposes a unique set of challenges to a digital rights management system. Highly correlated service request arrivals at the start of a live event require peak-load provisioning if clients acquire licenses at playback time. Distributing the license management load across a P2P network requires the digital rights management system to ensure the integrity of both digital rights, the protection of client privacy and, at the same time, system scalability. In this paper we describe the requirements imposed on a digital rights management system in distributing live broadcast over a P2P network and present our design of such a system to meet the above challenges. We discuss the system's operation under a number of threat models and how to extend the system to further improve scalability. We close the paper after presenting some scalability results collected from a production P2P live broadcast network using our DRM design.

A number of commercial peer-to-peer (P2P) systems for live streaming have been introduced in recent years. The behavior of these popular systems has been extensively studied in several measurement papers. Due to the proprietary nature of these commercial systems, however, these studies have to rely on a “black-box” approach, where packet traces are collected from a single or a limited number of measurement points, to infer various properties of traffic on the control and data planes. Although such studies are useful to compare different systems from the end-user's perspective, it is difficult to intuitively understand the observed properties without fully reverse-engineering the underlying systems. In this paper, we describe the network architecture of Zattoo, one of the largest production live streaming providers in Europe at the time of writing, and present a large-scale measurement study of Zattoo using data collected by the provider. To highlight, we found that even when the Zattoo system was heavily loaded with as high as 20 000 concurrent users on a single overlay, the median channel join delay remained less than 2-5 s, and that, for a majority of users, the streamed signal lags over-the-air broadcast signal by no more than 3 s.

Television transmitted over IP (IPTV) presents numerous opportunities for users as well as service providers, and has attracted significant interest from business and research communities in recent years. Among the emerging IPTV delivery architectures, the peer-to-peer based delivery mechanism is considered attractive due to the relative ease of service deployment. However, the question of how well P2PTV applications would support a growing number of users has not been fully investigated so far. In this paper, we try to address this question by studying scalability and efficiency factors in a typical P2P based live streaming network. Through the use of the data provided by a production P2PTV system, we carry out simulations whose results show that there are still hurdles to overcome before P2P based live streaming could become widely used.

A number of commercial peer-to-peer systems for live streaming, such as PPLive, Joost, LiveStation, SOPCast, TVants, etc. have been introduced in recent years. The behavior of these popular systems has been extensively studied in several measurement papers. Due to the proprietary nature of these commercial systems, however, these studies have to rely on a "black-box" approach, where packet traces are collected from a single or a limited number of measurement points, to infer various properties of traffic on the control and data planes. Although such studies are useful to compare different systems from end-user's perspective, it is difficult to intuitively understand the observed properties without fully reverse-engineering the underlying systems. Our paper presents a large-scale measurement study of Zattoo, one of the largest production live streaming providers in Europe, using data collected by the provider. To highlight, we found that even when the Zattoo system was heavily loaded with as high as 20,000 concurrent users on a single overlay, the median channel join delay remained less than 2 to 5 seconds, and that, for a majority of users, the streamed signal lags over-the-air broadcast signal by no more than 3 seconds. To motivate the measurement study, we also present a description of the Zattoo network architecture.

A P2PTV system allows users to watch live video streams redistributed by other users via a peer-to-peer (P2P) network. In an ideal world, each peer in a P2P network would be able to redistribute more bytes than it receives. A P2PTV system built from such peers can support a virtually unlimited number of peers; with only a single copy of content stream injected into the network, it can redistribute the content to all peers. Two factors in the development of the Internet prevented the realization of this scenario: the deployment of asymmetric access networks and the adoption of NAT boxes. For real-time live streaming, such peer asymmetry and incompatibility is a limiting factor on the P2P network scalability. We first develop a basic formal analysis of the effect of bandwidth asymmetry on P2P network scalability. Then we present several characteristics of peer asymmetry as measured on the Zattoo P2PTV network. Our simulation results, driven by the measured peer characteristics, confirm that we cannot rely on P2P network alone to distribute live streaming content on today's Internet.

Anycast routing is very useful for many applications such as resource discovery in delay tolerant networks (DTNs). In this paper, based on a new DTN model, we first analyze the any-cast semantics for DTNs. Then we present a novel metric named EMDDA (expected multi-destination delay for anycast) and a corresponding routing algorithm for anycast routing in DTNs. Extensive simulation results show that the proposed EMDDA routing scheme can effectively improve the efficiency of anycast routing in DTNs. It outperforms another algorithm, minimum expected delay (MED) algorithm, by 11.3% on average in term of routing delays and by 19.2% in term of average max queue length.

Compared with file-sharing and distributed hash table (DHT) network, P2P video streaming is more vulnerable to denial of service (DoS) attacks because of its high bandwidth demand and stringent time requirement. This paper studies the design of DoS resilient streaming networks using credit systems. We propose a novel framework-ripple-stream-to improve DoS resilience of P2P streaming. Ripple-stream leverages existing credit systems to introduce credit constraints in overlay construction such that malicious nodes are pushed to the fringe of overlays. Combining credit constraints with overlay optimization techniques, ripple-stream can achieve both DoS resilience and overlay efficiency

Network-overlay construction today assumes two-way communication capability - each host can initiate outgoing connections as well as accepting incoming connections. This is often not true on the current Internet due to several reasons, for example, the use of network address translation (NAT) and firewalls. Our experiments with eDonkey and Gnutella file-sharing systems reveal that as many as 36% of the hosts may be guarded - not accepting incoming connections. This presents a challenge to overlay construction because not all hosts are capable of receiving and forwarding requests. We propose an overlay optimization called e* to help existing overlay protocols overcome the reachability problem. Furthermore, e* builds very efficient overlay networks in terms of latency. Under realistic scenarios involving guarded hosts, e* can reduce the average overlay latency by 28-61% compared with existing protocols.

We call end-hosts behind network address translator (NAT) gateways or firewalls guarded hosts, and otherwise open hosts. In this paper, we empirically measure the prevalence of guarded hosts in two popular peer-to-peer file sharing systems, eDonkey and Gnutella, and study the characteristics of their shared files. By performing passive and active probes, we found that about 25-36% of eDonkey and Gnutella users reside on guarded hosts and that the ratio of files shared by guarded hosts is also non-trivial. When discounting guarded hosts, we found that a popular file's availability, i.e., the number of copies available for download, decreases by 25-30%. Our measurement study testifies to the significant impact guarded hosts may have on the performance of current peer-to-peer file sharing systems, and points to a need to consider their presence when designing next generation peer-to-peer systems.