Hierarchical Caching Systems Research Articles

Hierarchical Cache-Aided Networks for Linear Function Retrieval.

In a hierarchical caching system, a server is connected to multiple mirrors, each of which is connected to a different set of users, and both the mirrors and the users are equipped with caching memories. All the existing schemes focus on single file retrieval, i.e., each user requests one file. In this paper, we consider the linear function retrieval problem, i.e., each user requests a linear combination of files, which includes single file retrieval as a special case. We propose a new scheme that reduces the transmission load of the first hop by jointly utilizing the two layers' cache memories, and we show that our scheme achieves the optimal load for the second hop in some cases.

Modeling and Analysis of a Shared Edge Caching System for Connected Cars and Industrial IoT-Based Applications

The next revolution of industrial applications, known as smart industry or Industry 4.0, will rely on Internet of Things (IoT) to automate the monitoring, inspection, and control of industrial equipment and processes. In Industry 4.0, efficient content delivery is one of the fundamental challenges to be addressed. Nowadays, the promising solution for content delivery in smart industrial applications is the use of hierarchical caching systems at the network edge (5G small cells). This approach reduces the delay for content delivery and helps improve the performance of smart industrial applications. However, the caching management is a challenging and complex task, especially in those scenarios of shared storage resources on edge devices to support multiple concurrent applications (e.g., industrial, mobile users, and connected cars applications). In this article, we study the performance of a shared edge caching system for content delivery in smart industry and connected cars applications. To do so, we propose a mathematical framework to model the performance of a hierarchical shared edge caching system. The proposed mathematical framework considers the distinct content catalogs of the different applications (e.g., industrial and connected cars applications) and content request characteristics from industrial IoT devices and vehicles. Numerical results show that the performance of the shared edge caching system is sensitive to vehicular mobility (i.e., vehicular speed).

Cooperative Caching in Two-Layer Hierarchical Cache-aided Systems

Caching has received much attention as a promising technique to overcome high data rate and stringent latency requirements in the future wireless networks. The premise of caching technique is to prefetch most popular contents closer to end users in local cache of edge nodes, e.g., base station (BS). When a user requests a content that is available in the cache, it can be served directly without being sent from the core network. In this paper, we investigate the performance of hierarchical caching systems, in which both BS and end users are equipped with a storage memory. In particular, we propose a novel cooperative caching scheme that jointly optimizes the content placement at the BS’s and users’ caches. The proposed caching scheme is analytically shown to achieve a larger global caching gain than the reference in both uncoded – and coded caching strategies. Finally, numerical results are presented to demonstrate the effectiveness of our proposed caching algorithm.
 Keywords
 Hierarchical caching system, cooperative caching, caching gain, uncoded caching, coded caching
 References
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Analysis and performance study for coordinated hierarchical cache placement strategies

Data caching has been shown to be efficient in reducing network bandwidth consumption and accelerating information access. In a caching system, an important issue is coordinating data placement to achieve optimal system performance. This paper studies cache placement strategies and their performance in cooperative hierarchical caching environments. A theoretical model is introduced to analyze the access cost of placing a set of object copies in the routing path. Using this model, the object placement problem can be formulated as an optimization problem. It is proved that the problem can be divided into subproblems, thus optimal solutions can be obtained by using dynamic programming. It is further proved that if some nodes are known to be in the optimal solution, the calculation cost of the dynamic programming algorithms can be reduced. A heuristic greedy algorithm is also presented for efficient implementation. Performance of these strategies are evaluated using simulations under both synthetic workload traces and real workload traces. It is shown that both the optimal and the heuristic strategies perform well in cooperative hierarchical caching systems.

Distributed Shared Memory for Roaming Large Volumes

We present a cluster-based volume rendering system for roaming very large volumes. This system allows to move a gigabyte-sized probe inside a total volume of several tens or hundreds of gigabytes in real-time. While the size of the probe is limited by the total amount of texture memory on the cluster, the size of the total data set has no theoretical limit. The cluster is used as a distributed graphics processing unit that both aggregates graphics power and graphics memory. A hardware-accelerated volume renderer runs in parallel on the cluster nodes and the final image compositing is implemented using a pipelined sort-last rendering algorithm. Meanwhile, volume bricking and volume paging allow efficient data caching. On each rendering node, a distributed hierarchical cache system implements a global software-based distributed shared memory on the cluster. In case of a cache miss, this system first checks page residency on the other cluster nodes instead of directly accessing local disks. Using two Gigabit Ethernet network interfaces per node, we accelerate data fetching by a factor of 4 compared to directly accessing local disks. The system also implements asynchronous disk access and texture loading, which makes it possible to overlap data loading, volume slicing and rendering for optimal volume roaming.

On Expiration-Based Hierarchical Caching Systems

Caching is an important means to scale up the growth of the Internet. Weak consistency is a major approach used in Web caching and has been deployed in various forms. The paper investigates some fundamental properties and performance issues associated with an expiration-based caching system. We focus on a hierarchical caching system based on the time-to-live expiration mechanism and present a basic model for such system. By analyzing the intrinsic timing behavior of the basic model, we derive important performance metrics from the perspectives of the caching system and end users, respectively. Based on the results for the basic model, we introduce threshold-based and randomization-based techniques to enhance and generalize the basic model further. Our results offer some important insights into a hierarchical caching system based on the weak consistency paradigm.

Retrieval and freshness thresholds in hierarchical caching systems

To scale up with the explosive Web growth, caching systems have been proposed and deployed over the Internet in recent years. Among them, hierarchical caching systems employing expiration-based consistency control mechanisms have become a viable and efficient solution. In this paper, we first analyze the performance of such hierarchical caching systems from the perspectives of both cache servers and end users. Then, we examine retrieval and freshness threshold-based approaches and their impact on system performance and user-perceived QoS. We show that by setting these thresholds appropriately, it is possible that (1) users can impose a consistency QoS requirement on the object that they wish to obtain without too much trade-off in system performance, and (2) performance bias against leaf users due to their unfavorable locations in the hierarchical structure can be mitigated.

Analysis and evaluation of expiration-based hierarchical caching systems

This paper investigates some fundamental properties and performance issues of the expiration-based caching systems. We focus on the hierarchical caching systems based on the time-to-live (TTL) expiration mechanism, and present a basic model for such systems. By analyzing the intrinsic timing behavior in this model, we derive some important performance metrics from the perspectives of caching systems and end users, respectively. We use network simulation results to further substantiate the efficacy of our analysis. Our results show some basic properties and trade-offs for a hierarchical caching system based on the weak consistency mechanism.

Hierarchical Web caching systems: modeling, design and experimental results

This paper aims at finding fundamental design principles for hierarchical Web caching. An analytical modeling technique is developed to characterize an uncooperative two-level hierarchical caching system where the least recently used (LRU) algorithm is locally run at each cache. With this modeling technique, we are able to identify a characteristic time for each cache, which plays a fundamental role in understanding the caching processes. In particular, a cache can be viewed roughly as a low-pass filter with its cutoff frequency equal to the inverse of the characteristic time. Documents with access frequencies lower than this cutoff frequency have good chances to pass through the cache without cache hits. This viewpoint enables us to take any branch of the cache tree as a tandem of low-pass filters at different cutoff frequencies, which further results in the finding of two fundamental design principles. Finally, to demonstrate how to use the principles to guide the caching algorithm design, we propose a cooperative hierarchical Web caching architecture based on these principles. Both model-based and real trace simulation studies show that the proposed cooperative architecture results in more than 50% memory saving and substantial central processing unit (CPU) power saving for the management and update of cache entries compared with the traditional uncooperative hierarchical caching architecture.