Today, an increasing number of important network services, such as content distribution, replicated services, and storage systems, are deploying overlays across multiple Internet sites to deliver better performance, reliability and adaptability. Currently however, such network services must individually reimplement substantially similar functionality. For example, applications must configure the overlay to meet their specific demands for scale, service quality and reliability. Further, they must dynamically map data and functions onto network resources-including servers, storage, and network paths-to adapt to changes in load or network conditions.In this paper, we present Opus, a large-scale overlay utility service that provides a common platform and the necessary abstractions for simultaneously hosting multiple distributed applications. In our utility model, wide-area resource mapping is guided by an application's specification of performance and availability targets. Opus then allocates available nodes to meet the requirements of competing applications based on dynamically changing system characteristics. Specifically, we describe issues and initial results associated with: i) developing a general architecture that enables a broad range of applications to push their functionality across the network, ii) constructing overlays that match both the performance and reliability characteristics of individual applications and scale to thousands of participating nodes, iii) using Service Level Agreements to dynamically allocate utility resources among competing applications, and iv) developing decentralized techniques for tracking global system characteristics through the use of hierarchy, aggregation, and approximation.

IBMThis article focuses on the multireceiver data dissemination problem. Initially, IP multicast formed the basis for efficiently supporting such distribution. More recently, overlay networks have emerged to support point-to-multipoint communication. Both techniques focus on constructing trees rooted at the source to distribute content among all interested receivers. We argue, however, that trees have two fundamental limitations for data dissemination. First, since all data comes from a single parent, participants must often continuously probe in search of a parent with an acceptable level of bandwidth. Second, due to packet losses and failures, available bandwidth is monotonically decreasing down the tree.To address these limitations, we present Bullet, a data dissemination mesh that takes advantage of the computational and storage capabilities of end hosts to create a distribution structure where a node receives data in parallel from multiple peers. For the mesh to deliver improved bandwidth and reliability, we need to solve several key problems: (i) disseminating disjoint data over the mesh, (ii) locating missing content, (iii) finding who to peer with (peering strategy), (iv) Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or direct commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 ( right rate from all peers (flow control), and (v) recovering from failures and adapting to dynamically changing network conditions. Additionally, the system should be self-adjusting and should have few user-adjustable parameter settings. We describe our approach to addressing all of these problems in a working, deployed system across the Internet. Bullet outperforms state-of-the-art systems, including BitTorrent, by 25-70% and exhibits strong performance and reliability in a range of deployment settings. In addition, we find that, relative to tree-based solutions, Bullet reduces the need to perform expensive bandwidth probing.

Overcast and a two-metric (delay-constrained, cost-optimized) overlay.

We believe that application-aware networks will be a core component in the development and deployment of emerging network services. However, previous attempts at enabling application-awareness in the network have failed due to issues with security, resource allocation, and cost of deployment. The emergence of the Extensible Markup Language (XML), an open standard that enables data interoperability, along with advances in hardware, software, and networking technologies, serves as the catalyst for the development of service-oriented networking (SON). SON enables network components to become application-aware, so that they are able to understand data encoded in XML and act upon that data intelligently to make routing decisions, enforce QoS or security policies, or transform the data into an alternate representation. This paper describes the motivation behind service-oriented networking, the potential benefits of introducing application-aware network devices into service-oriented architectures, and discusses research challenges in the development of SON-enabled network appliances.

The key principles behind current peer-to-peer research include fully distributing service functionality among all nodes participating in the system and routing individual requests based on a small amount of locally maintained state. The goals extend much further than just improving raw system performance: such systems must survive massive concurrent failures, denial of service attacks, etc. These efforts are uncovering fundamental issues in the design and deployment of distributed services. However, the work ignores a number of practical issues with the deployment of general peer-to-peer systems, including i) the overhead of maintaining consistency among peers replicating mutable data and ii) the resource waste incurred by the replication necessary to counteract the loss in locality that results from random content distribution. This position paper argues that the key challenge in peer-to-peer research is not to distribute service functions among all participants, but rather to distribute functions to meet target levels of availability, survivability, and performance. In many cases, only a subset of participating hosts should take on server roles. The benefit of peerto-peer architectures then comes from massive diversity rather than massive decentralization: with high probability, there is always some node available to provide the required functionality should the need arise.