Optimizing the Reliable Distribution of Large Files within CDNs

Recently, there is a growing interest in the applications of wireless sensor networks (WSNs). A set of sensor nodes is deployed in order to collectively survey an area of interest and/or perform specific surveillance tasks in some of the applications, such as battlefield reconnaissance. Due to the harsh deployment environments and limited energy supply, nodes may fail, which impacts the connectivity of the whole network. Since a single node failure (cut-vertex) will destroy the connectivity and divide the network into disjoint blocks, most of the existing studies focus on the problem of single node failure. However, the failure of multiple nodes would be a disaster to the whole network and must be repaired effectively. Only few studies are proposed to handle the problem of multiple cut-vertex failures, which is a special case of multiple node failures. Therefore, this paper proposes a comprehensive solution to address the problems of node failure (single and multiple). Collaborative Single Node Failure Restoration algorithm (CSFR) is presented to solve the problem of single node failure only with cooperative communication, but CSFR-M, which is the extension of CSFR, handles the single node failure problem more effectively with node motion. Moreover, Collaborative Connectivity Restoration Algorithm (CCRA) is proposed on the basis of cooperative communication and node maneuverability to restore network connectivity after multiple nodes fail. CSFR-M and CCRA are reactive methods that initiate the connectivity restoration after detecting the node failure(s). In order to further minimize the energy dissipation, CCRA opts to simplify the recovery process by gridding. Moreover, the distance that an individual node needs to travel during recovery is reduced by choosing the nearest suitable candidates. Finally, extensive simulations validate the performance of CSFR, CSFR-M and CCRA.

Replica placement in ring based content delivery networks

Broadband network technologies have improved the bandwidth of the edge of the Internet but its core is still a bottleneck for large file transfers. Content Delivery Networks (CDNs), built at the edge of the Internet, are able to reduce the workload of network backbones but their scalability and network reach is often limited, especially in case of QoS-bound delivery services. By using the emerging CDN internetworking, a CDN can dynamically exploit resources of other cooperating CDNs to face peak loads and temporary malfunctions without violating QoS levels negotiated with content providers. This paper proposes an architectural schema and an algorithm to minimize transfer time of large files taking into account the SLA constraints agreed between the CDN in charge of content delivery and the content provider, while respecting the maximum budget that the CDN can pay to peer CDNs to ensure its revenue. The experimental analysis confirms the benefits of applying the proposed algorithm in CDN internetworking to enforce SLA guarantees of CDN services.

Over the last years, the content delivery network (CDN) market has been witnessing globally an increase in the development of cloud-based CDNs, as they constitute a viable and cost-effective alternative to traditional commercial CDNs. Towards that direction, Social-Aware Virtual Network Embedding (SAViNE) for wireless content delivery within the OpenLab project aims at establishing, assessing, and prototyping a novel framework for deploying a CDN over the wireless cloud. Specifically, the goal of SAViNE is to provide experimental validation of the efficiency of social network analysis (SNA) - inspired surrogate server placement strategies, devised for fostering content delivery. The proposed framework has been integrated with the OpenLab experimental facilities, providing a run-time environment for CDN deployment, operation, and performance evaluation over the wireless environment. The framework’s feasibility and scalability is experimentally validated. The study is complemented with repeatability evaluation of experimental measurements, related to the resulting CDN’s operational efficiency.

Today’s content delivery networks (CDNs) use large sets of globally distributed servers, advanced routing techniques, and dynamic server selection to provide users with low delay, reliable access to Web, and streaming content. These strategies allow CDNs to extend their reach and performance into large numbers of networks around the globe. However, nearly 20% of Internet users reside in China, where local regulations and network policies make it challenging for global CDNs to serve foreign content from servers in China and limit the effectiveness of their traditional strategies for low-latency content delivery. Recently, a number of China-specific CDNs have partnered with global CDNs to provide service in the country. However, little is known about how CDNs in China are implemented, nor their impact on performance. In this paper, we are the first to investigate the impact of China’s unique policy and networking environment on CDN implementations and deployments. We find that deployments inside China exhibit different client-mapping behavior than global ones, namely, through static server selection for clients given a customer site, and through region-specific clients partitioning and mapping rather than using live network information. We also show that ignoring these properties can significantly impact server selection quality. Our results can be useful for optimization of CDNs in China.

Recently, large-volume contents distributed by a content delivery network (CDN) on the Internet increase the load of content delivery servers and networks, which may degrade the quality of service. To overcome this problem, some mirror servers providing the same content are located on a network, and a request is navigated to one of the mirror servers. It is important to locate the mirror servers on the appropriate place in a network, as it affects the performance of the CDN. In this paper, we address the server location problem, which determines the location of the mirror servers satisfying the following two constraints: the number of the paths to the servers in a link is small, and the number of the nodes whose nearest mirror server is the same is small. The former constraint corresponds to the alleviation of the network load, and the latter constraint corresponds to the alleviation of the server load. First, we prove that this new server location problem is NP-complete. Next, we present a heuristic algorithm and evaluate it by applying to some actual network topologies. The results show that the algorithm can determine a good server location.

Modern websites use Content Delivery Networks (CDNs) to speed up the delivery of static content. However, we show that DNS-based selection of CDN servers can be refined to fully deliver on the speedup of CDNs. We propose DNS-Proxy (dp), a client-side process that shares load-balancing functionality with CDNs by choosing from among resolved CDN servers based on last mile network performance. Our measurement study of CDN infrastructure deployed by five major CDN providers shows that dp reduces webpage load time by 29% on average. If dp has already resolved the domain, the reduction in webpage load time is as much as 40%. Finally, dp reduces the load time of individual static Web objects by as much as 43%. We argue that dp enables a more effective use of existing content delivery infrastructure and represents a complementary strategy to a continual increase of geographic content availability.

The proliferation of online video consumption, particularly for live events attracting massive global audiences, necessitates robust and scalable content delivery mechanisms. This article explores the critical role of Content Delivery Networks (CDNs) in facilitating the seamless distribution of live video streams to millions of concurrent viewers. It explores the fundamental architecture of CDNs, including edge servers, routing methodologies such as Geographic Load Balancing and Anycast Routing, and the importance of caching and content replication. Furthermore, it analyzes how these technologies are specifically applied to the delivery of high-demand live events, using the "Big Game" as a salient example. The "Big Game" refers to the major annual championship football event in the United States that consistently ranks among the most-watched broadcasts worldwide. The document concludes by considering emerging trends in CDN technology that promise to further enhance the efficiency and performance of live video delivery.

The presence of bottlenecks in the Internet reduces the performance of content delivery in typical client-server applications such as Web browsing and media streaming. Caching and server farm architectures have been a good solution to this problem since the World Wide Web became very popular, but now they are not enough to support new e-business solutions. Content delivery networks (CDNs) distribute content by placing it on several surrogate servers across the Internet and try to overcome these bottlenecks. In CDN scenarios a good request routing algorithm selects the best surrogate for a client's request; it makes its decision using metrics received by the network and the surrogate. Typical metrics are network latency, hop count, available Internet bandwidth, and surrogate load. We analyze the impact of different request routing algorithms on the delivery performance of CDNs. A new request routing algorithm, called WSE (worst surrogate exclusion), is proposed. Worst surrogate exclusion excludes those surrogates that provide the client with low performance and prevents surrogates overloading. Simulation results show that WSE can reduce users average response time and efficaciously exploit the CDN's capacity.

We analyze competition between Internet Service Providers (ISPs) where consumers demand heterogeneous content within two Quality-of-Service (QoS) regimes, Net Neutrality and Paid Prioritization, and show that paid prioritization increases the static efficiency compared to a neutral network. We also consider paid prioritization intermediated by Content Delivery Networks (CDNs). While the use of CDNs is welfare neutral, it results in higher consumer prices for internet access. Regarding incentives to invest in network capacity we show that discriminatory regimes lead to higher incentives than the neutral regime as long as capacity is scarce, while investment is highest in the presence of CDNs.

This paper describes issues in current multicast content delivery network (CDN) architecture and presents a framework for multicast CDN to satisfy the requirements for content delivery service (Hayashi et al., 2005). In our experience, requirements for CDN (Hayashi et al., 2005) are not perfectly covered by possible current methods using current group management protocols such as IGMP (B. Cain et al., 2002) and MLD (R. Vida et al., 2004). Therefore, we propose a new framework for multicast CDN to support authentication authorization & accounting (AAA) and QoS control

Content delivery over Internet is optimized for low use perceived latency by designing specialized Content Distribution Network (CDN). Content servers are connected through a content switch the distributes client requests among them to achieve load balancing across the servers. The content switch is located one-hop away from the servers. Server load balancing is one factor in achieveing low user perceived latency and improving operational efficiency. Traffic engineering is another factor that is generally and integrated with serverload balancing for CDN optimization. In this thesis we propose a request routing algorithm for a CDN that was designed to integrate server selection and traffic engineering functions in the request routing system. The CDN employs MPLS in the network for traffic engineering. The proposed algorithm optimizes content delivery for user perceived latency by achieving server load balancing and network traffic loan manaement among alternative paths. It also improves operational efficiency of the CDN by eliminating bottleneck paths and increasing utilization of underutilized servers and paths.

Mobile and wireless technology has revolutionized people’s lives by enabling data delivery anytime, anywhere, liberating the users from the restrictions of wired networks. In addition broadband communications permit high speed data connections. Since multimedia content delivered on-line requires reasonably high data rates and today’s wireless networks (3G, Wi-Fi, WiMAX etc) can support the quality requirements of media streaming delivery, while mobile devices handheld or not (Pocket PC, smart phones, laptop pc etc) are able to accommodate a variety of content formats, content delivery has become an indisputable trend. This paper presents such a content delivery network, the ENAMORADO architecture, which is the outcome of the work carried out in the IST project ENAMORADO (Enabling Nomadic Agents in a Multimedia Oriented Architecture of Distributed Objects). The ENAMORADO architecture covers the full content delivery chain from the media producers to the end users incorporating the content production, annotation, aggregation, adaptation and delivery. The paper describes the reference architecture of the infrastructure as well as the testbed used in the components integration and validation process. In addition further system evaluation results are presented.

SummaryIn today's dynamic video landscape, an end user needs services to be delivered to any devices anytime with less delay over the Internet. Now users' expectation has changed; they want faster time‐to‐market, cost reduction, and the ability to adjust according to the evolving requirements, which are a limit for the traditional server‐based approach. The explosive growth of the internet multimedia application needs a new approach to content delivery to overcome the limitations of server‐based techniques. Cloud‐based content delivery networks (CCDNs) have recently started to emerge where contents are cached from the cloud storage and delivered through the distribution service to meet quality of services (QoS) of requested services. In this paper, we dealt with CCDN deployment problem and proposed a new eigenvalue‐based edge infrastructure for a network service provider to serve the users with a variation on proximity interest concerning operational cost and user QoS satisfaction. The edge infrastructure designing is a two‐step process: (a) ideal location search for placing edge server and (b) edge server placement and capacity provisioning. The performance of the proposed approach is appraised via modeling and simulation. Performance evaluation outcomes are exhibited to manifest the effectiveness and competitiveness of our approach when compared with existing algorithms.

MapReduce is an emerging programming paradigm and an associated implementation for processing and generating big data which has been widely applied in data-intensive systems. In cloud environment, node and task failure is no longer accidental but a common feature of large-scale systems. In MapReduce framework, although the rescheduling based fault-tolerant method is simple to implement, it failed to fully consider the location of distributed data, the computation and storage overhead. Thus, a single node failure will increase the completion time dramatically. In this paper, a Checkpoint and Replication Oriented Fault Tolerant scheduling algorithm (CROFT) is proposed, which takes both task and node failure into consideration. Preliminary experiments show that with less storage and network overhead . CROFT will significantly reduce the completion time at failure time, and the overall performance of MapReduce can be improved at least over 30% than original mechanism in Hadoop. DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.4324