Watch Global, Cache Local: YouTube Network Traffic at a Campus Network - Measurements and Implications

User Generated Content has become very popular since the birth of web services such as YouTube allowing the distribution of such user-produced media content in an easy manner. YouTube-like services are different from existing traditional VoD services because the service provider has only limited control over the creation of new content. We analyze how the content distribution in YouTube is realized and then conduct a measurement study of YouTube traffic in a large university campus network. The analysis of the traffic shows that: (1) No strong correlation is observed between global and local popularity; (2) neither time scale nor user population has an impact on the local popularity distribution; (3) video clips of local interest have a high local popularity. Using our measurement data to drive trace-driven simulations, we also demonstrate the implications of alternative distribution infrastructures on the performance of a YouTube-like VoD service. The results of these simulations show that client-based local caching, P2P-based distribution, and proxy caching can reduce network traffic significantly and allow faster access to video clips

Monitoring, measurement, and control of multimedia traffic in IP networks

In this thesis, we propose several architectural components for monitoring, measurement, and control of multimedia traffic in IP networks. These architectural components are used to monitor and measure multimedia traffic at the edge of IP networks and in the core of IP networks, and to serve stored multimedia contents to clients in edge networks. We first present a technique to detect multimedia relay traffic from passively measured packet traces collected at the edge of the Internet. Recently, networked application developers have started to use end-users\u27 computers as relay nodes. These relay nodes incur costs to both users and network operators, in the form of increased bandwidth consumption. Among various streaming relayed traffic, we focus on characterizing and detecting relayed traffic generated by Skype, a popular voice over IP application that uses relays. We propose several flow-level metrics to characterize the nature of relayed traffic. These metrics together with the results obtained from the experimental characterization of Skype-relayed traffic are used to develop techniques to detect Skype-relayed traffic traversing the access point of a large network. We find that the metrics proposed can be applied more broadly in the detection of relayed traffic generated by other multimedia applications. We next present a concurrent passive monitoring architecture for IP flows at multiple locations within an IP network. The objective of such a distributed monitoring system is to sample packets belonging to a large fraction of IP flows in a cost-effective manner by carefully placing monitors and controlling their sampling rates. We consider the problem of where to place monitors within the network and how to set their sampling rates. It is particularly important to sample packets in a cost-effective manner for monitoring multimedia traffic, since multimedia traffic has high monitoring bandwidth requirements. To address the tradeoff between monitoring cost and monitoring coverage, we consider minimum cost and maximum coverage problems under various budget constraints. We formulate several problems and show that they are NP-hard. We propose greedy heuristics, and show, using synthetic and real network topologies, that the heuristics provide solutions quite close to the optimal solutions. In addition, our experiments show that a small number of monitors is often enough to monitor most of the traffic in an entire IP network. Last, we introduce and evaluate the Push-to-Peer architecture for streaming video among cooperating nodes in an edge network, that can drastically reduce the load posed on the core and access links of the network and also on the streaming servers. The main departure from previous designs is that content is proactively pushed to peers and persistently stored before the actual peer-to-peer transfers. The initial content placement increases content availability and improves the use of peer uplink bandwidth. Our specific contributions are: (i) content placement and associated pull policies that allow the optimal use of uplink bandwidth; (ii) a performance analysis of the policies in the case of a controlled environment such as DSL networks under ISP control; (iii) a distributed load balancing strategy for selection of serving peers; (iv) distributed strategies to cope with dynamic uplink bandwidth

Challenges in peer-to-peer gaming

This article is an editorial note submitted to CCR. It has NOT been peer reviewed. Authors take full responsibility for this article’s technical content. Comments can be posted through CCR Online. While multi-player online games are very successful, their fast deployment suffers from their server-based architecture. Indeed, servers both limit the scalability of the games and increase deployment costs. However, they make it easier to control the game (e.g. by preventing cheating and providing support for billing). Peer-to-peer, i.e. transfer of the game functions on each each player’s machine, is an attractive communication model for online gaming. We investigate here the challenges of peer-to-peer gaming, hoping that this discussion will generate a broader interest in the research community

Cast: P2P Patching Scheme for VoD ¢

Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose ¥§ ¦ Cast- an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in ¥§ ¦ Cast: (1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches) in the face of disruption from an early departing client. Our simulation experiments show that¥§ ¦ Cast can serve many more clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients can cache more than¨�©� � of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying the shifted forwarding technique. A threshold on the length of time during which arriving clients are served in a single session in¥� ¦ Cast serves as a knob to adjust the balance between the scalability and the clients ’ viewing quality in¥� ¦ Cast. I