Efficient Cache Placement Strategy in Two-Tier Wireless Content Delivery Network

Wireless networking is a crucial component of communication in this era of digitization. The key characteristics that determine a wireless network's performance are smooth connectivity, quicker communication, and increased customer satisfaction. Scalability deals with the erratic workload and new resources that are added to the network. Scalability is crucial for both Quality of Experience (QoE) and Quality of Service (QoS) in such a power-constrained environment because wireless devices are battery-operated. Managing power consumption and network performance simultaneously in scalable networking scenario is quite challenging, especially during handover. This research proposed a methodology to assess the impact of scalability on wireless node power consumption and network performance in order to develop energy-efficient handoff mechanisms. The Type-I and Type-II wireless node sets were used between the WiFI and WiMAX networks in a vertical handover scenario. In the study, two distinct scalability scenarios were taken into account. Three distinct voltage levels—cutoff voltage, nominal voltage, and charge voltage —had been used to examine the consumption of power. Throughput, residual energy, and Packet Delivery Ratio (PDR) were computed to examine the network's performance in a scalable, power-constrained context. Two different scalability scenarios were considered in the study. The power consumption was investigated using three different voltage levels: charge voltage, nominal voltage, and cutoff voltage. The network's performance under scalable, power-constrained conditions was investigated by computing throughput, packet delivery ratio (PDR), and residual energy. The result obtained in the study showed the variation in battery drainage of wireless nodes under the effect of various scalability factors. This study will provide a blueprint for developing novel algorithms which eventually will improvise network performance and strengthen the base of Green Networking.

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.

Replica placement in ring based content delivery networks

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.

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.

This paper addresses the Quality of Service (QoS) degradation problem of wireless relay node failures in multihop Worldwide interoperable Microwave Access (WiMAX) and Long Term Evolution (LTE) networks. In general, node protection in a communication network increases the reliability of the traffic flow from source to destination. For wireless networks, implementing the traditional 1+1 protection scheme increases the capital cost, as resources cannot be fully utilized. On the other hand, the design and implementation of the 1:N protection scheme in wireless networks for greater value of N (> 2) is very difficult, due to wireless network coverage and the physical layer design. To overcome the above drawbacks, a technique based on network coding is proposed for node protection in multihop wireless networks. In multihop wireless networks, few research efforts are concentrated on node protection schemes using network coding. Moreover, to best of our knowledge, no reports have been published on measuring the QoS performance for node protection in 4G wireless networks using network coding. In this paper, we first describe the node protection scheme using XOR network coding for multihop 4G wireless networks. Then, we measure the QoS performance, such as packet delivery ratio (PDR), latency and jitter, for different scenarios. The scenarios include a failure of a single relay node and failures of two relay nodes with and without our protection scheme and user's mobility. The simulation results show that the QoS performance with protection against a single relay node failure and failures of two relay nodes are very close to that of no failure scenario, while the network reliability increases due to the protection mechanism. Also, we report a decoding problem in multihop wireless networks using XOR network coding.

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.

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.

Towards simulation and optimization of cache placement on large virtual content distribution networks

In this paper we present a method to assess measurements for link quality estimation in wireless networks. Quality of service (QoS) is increasingly important in 3G wireless networks. Commonly, the end to end QoS is defined by delay and error rate. To meet the end-to-end QoS requirements it is very important to control the error rates on the air interface. The error rates can be controlled by change the energy per bit on the air interface. A mismatching energy assignment will either result in a waste of capacity or in a violation of the error rate requirements for the air interface. Thus, the link quality estimation is critical for performance and capacity of wireless networks. In this paper we present a method to evaluate the value of possible measurements for link quality estimation. This method supports the selection process of appropriate measurements and allows the comparison of their performance. As an example, we apply the presented method to an UMTS 12.2 kbps connection.

Device-to-device (D2D) cache placement and content delivery is a recent technology that exploits idle memory capacity of mobile devices and promises to fulfill users' content needs with very low delay and without using the scarce cellular network capacity. Recent literature on D2D caching mostly concentrated on optimal cache placement and mostly disregarded the required discovery mechanisms and the accompanying overhead. In this work we propose a clustering-based procedure that is used to cache content at the helper nodes along with advertisement and discovery procedures for content delivery. We implement a Long Term Evolution (LTE)-based simulation setup to evaluate the proposed schemes. Numerical results reveal that the clustering-based user and content discovery significantly improves cellular offloading and reduces the discovery overhead with a minimal sacrifice from delay.

Content delivery network (CDN) with a high quality-of-service (QoS) requirement deals with three challenging problems: 1) a cache server deployment problem to determine where to locate cache servers, 2) a request routing problem to settle which cache server serves a user request, and 3) a content replication problem to decide which content is stored in a cache server. Cooperation among cache servers significantly improves the user QoS by increasing the cached content diversity of the network. Since the aforementioned problems are tightly coupled, we formulate a new CDN model which jointly considers all the three problems under the cooperative content replication with optimal solutions using integer linear programming. As the joint optimization problem is an NP-hard problem, we propose a greedy heuristic algorithm which is close to the optimal solution. We consider two scenarios for application of the algorithm, where the popularities of contents are identical and are different among nodes. The performance of the algorithm is investigated on the actual topology sampled from the Level 3 CDN network. By increasing the cached content diversity in the network, the joint optimization problem under the cooperative content replication shows higher performance than that of the non-cooperation case.

A new multi-rat scheduling algorithm for heterogeneous wireless 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.

Content Distribution Networks (CDN) appeared a decade ago as a method for reducing latencies, improving performance experienced by Internet users, and limiting the effect of flash-crowds, so as balance load in servers. Content Distribution has evolved in different ways (e.g. cloud computing structures and video streaming distribution infrastructures). The solution proposed in early CDN was the location of several controlled caching servers close to clients, organized and managed by a central control system. Many companies deployed their own CDN infrastructure– and so demonstrating the resulting effectiveness. However, the business model of these networks has evolved from the distribution of static web objects to video streaming. Many aspects of deployment and implementation remain proprietary, evidencing the lack of a general CDN model, although the main design concepts are widely known. In this work, the authors represent the structure of a CDN and the performance of some of its parameters, using queuing theory, simplifying the redirection schema and studying the elements that could determine the improvement in performance. The main contribution of the work is a general expression for a CDN environment and the relationship between different variables like caching hit ratios, network latency, number of surrogates, and server capacity; this proves that the use of CDN outperform the typical client/server architecture.