SLA-based Content Delivery in Multi-CDNs

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.

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.

Video traffic has witnessed exponential growth in recent years. As the cost optimization space of Content Delivery Network (CDN) has reached a plateau, content providers are expanding their network infrastructure to accommodate this surge. To address the cost issue, content providers have turned to cost-effective Peer-to-Peer Content Delivery Network (PCDN) solutions. However, the utilization of limited-capability PCDN nodes may lead to a decline in overall streaming performance compared to powerful CDN servers. To bridge this performance gap, we present Twist. Twist is a receiver-driven multi-site transport that leverages multiple cost-effective PCDN nodes to achieve performance equivalent to traditional CDN solutions. It incorporates a joint flow control to prevent throughput drops that can occur when using multiple content sources, and a proactive retransmission algorithm to handle frequent packet loss. Our evaluations demonstrate that Twist improves download speed on PCDN nodes by 1.71x-2.09x compared to traditional PCDN streaming solutions. Furthermore, extensive A/B testing verifies that Twist enables PCDN to achieve comparable download performance and Quality of Experience (QoE) as CDN. Over three years of commercial deployment, Twist has already served over 300 million users and has handled 35% of the video traffic, resulting in substantial cost savings for a world-leading content provider.

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.

Increasing over-the-top video consumption makes the delivery of content unsustainable in the current Internet. The Internet Service Providers (ISP) have a hard time competing on value-added services with content providers and content delivery networks (CDN). We propose a new model of collaboration between content delivery actors where CDNs can deploy their software in Internet Service Providers' infrastruc-ures as NFV modules. As the ISP network state has to be kept private, a high-level SLA is used to negotiate both computing resources and connectivity, leaving it up to the ISP to optimize server placement and routes. The contribution of this paper is to formalize this problem as a Service Function Chaining Embedding problem, and to propose an algorithm to optimize the Service Function Chain to improve embedding probability and decrease consumed bandwidth in the process.

Cloud computing becomes a popular trend in recent years. In the meanwhile, content delivery network has been used for many years to distribute content all over the world. The relation between cloud computing and content delivery network is very interesting. In this paper, we proposed a cloud based content delivery network. This architecture integrates cloud infrastructure and content delivery network system together. It provides a low cost and elastic web serving cloud platform. Besides, it also provides easy way to manage data for web content developers, and accelerate the speed for users to access web sites. This system uses Hadoop Distributed File System as a cloud infrastructure service, and creates many data clusters around the world. Therefore, content providers could place content to closest node from end users. The result shows a high performance and flexible solution to build a personal content delivery network over cloud.

Internet delivery infrastructures are traditionally optimized for low-latency traffic, such as the Web traffic. However, in recent years we are witnessing a massive growth of throughput-oriented applications, such as video streaming. These applications introduce new tradeoffs and design choices for content delivery networks (CDNs). In this paper, we focus on understanding two key design choices: (1) What is the impact of the number of CDN's peering points and server locations on its aggregate throughput and operating costs? (2) How much can ISP-CDNs benefit from using path selection to maximize its aggregate throughput compared to other CDNs who only have control at the edge? Answering these questions is challenging because content distribution involves a complex ecosystem consisting of many parties (clients, CDNs, ISPs) and depends on various settings which differ across places and over time. We introduce a simple model to illustrate and quantify the essential tradeoffs in CDN designs. Using extensive analysis over a variety of network topologies (with varying numbers of CDN peering points and server locations), operating cost models, and client video streaming traces, we observe that: (1) Doubling the number of peering points roughly doubles the aggregate throughput over a wide range of values and network topologies. In contrast, optimal path selection improves the CDN aggregate throughput by less than 70\%, and in many cases by as little as a few percents. (2) Keeping the number of peering points constant, but reducing the number of location (data centers) at which the CDN is deployed can significantly reduce operating costs.

The Internet architecture, based on end-to-end connections, had difficulties to efficiently deliver the always increasing number of contents. Content Delivery Networks (CDN) have been deployed to improve the delivery. Recent research works propose a new networking architecture, much more adapted to the current Internet usage (end-users just care about the contents they want and not about the endpoints that provide them). The Content-Centric Networking (CCN) aims at replacing the IP paradigm. CCN has been investigated by the research community for few years, and some demonstrators have proved its feasibility. However, less works have addressed the CDN use-case so far. In this paper, we show that the current CCN design, which does not allow negative reply, is not suitable for interconnection with the CDN service. We then propose the use of two new tables in the CCN nodes that are interconnected to the CDN servers, in order to detect possible misses in the CDN servers and subsequently forward the requests for missing contents toward the original servers instead of the CDN surrogates. The evaluations we have performed highlight that the integration of both new tables does not incur an increase of the memory requirement and thus a cost in the node. The proposed solution is thus a viable solution to make CCN network work in close cooperation with CDN networks, each one keeping its specific business models and functions: transport for CCN, storage for CDN.

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.

Content delivery networks (CDNs) provide an efficient support for serving http and streaming media content white minimizing the network impact of content delivery as well as overcoming the server overload problem. For serving the large documents and media files, there is an additional problem of the original content distribution across the CDN edge servers. We propose an algorithm, called ALM-fastreplica, for optimizing replication of large files across the edge servers in CDNs. The original file is partitioned into k subfiles, and each subfile is replicated via a correspondingly constructed multicast tree. Nodes from the different multicast trees use additional cross-nodes connections to exchange their corresponding subfiles such that each node eventually receives an entire file. This new replication method significantly reduces file replication time, up to 5-15 times compared to the traditional unicast (or point-to-point) schema. Since a single node failure in the multicast tree during the file distribution may impact the file delivery to a significant number of nodes, it is important to design an algorithm which is able to deal with node failures. We augment ALM-FastReplica with an efficient reliability mechanism, that can deal with node failures by making local repair decisions within a particular replication group of nodes. Under the proposed algorithm, the load of the failed node is shared among the nodes of the corresponding replication group, making the performance degradation gradual.

Content Delivery Networks (CDNs) have emerged as a dominant mechanism to deliver content over the Internet. Despite their importance, to our best knowledge, large-scale analysis of CDN cache performance is lacking in prior literature. A CDN serves many content publishers simultaneously and thus has unique workload characteristics; it typically deals with extremely large content volume and high content diversity from multiple content publishers. CDNs also have unique performance metrics; other than hit ratio, CDNs also need to minimize network and disk load on cache servers. In this paper, we present measurement and analysis of caching workload at a large commercial CDN. Using detailed logs from four geographically distributed CDN cache servers, we analyze over 600 million content requests accounting for more than 1.3 petabytes worth of traffic. We analyze CDN workload from a wide range of perspectives, including request composition, size, popularity, and temporal dynamics. Using real-world logs, we also evaluate cache replacement algorithms, including two enhancements designed based on our CDN workload analysis: N-hit and content-aware caching. The results show that these enhancements achieve substantial performance gains in terms of cache hit ratio, disk load, and origin traffic volume.

With the development of computer networks, the amount of network information continues to grow. To facilitate the transfer of the increasing information, a content distribution network (CDN) is developed by adding an intermediate layer on the existing network. Technically, Caching strategy of CDN is the most important mechanism, which heavily impacts the CDN performance. On the other hand, considering the cost of operating CDN, some strategies have been proposed, aiming to save the CDN cost in terms of, e.g., power energy. This paper makes a brief review on the recent developments of CDN in terms of its caching strategy and operation cost, and discusses some potential development directions of CDN.

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