Abstract. Ubiquitous in-network caching is one of the key aspects of information-centric networking (ICN) which has recently received widespread research interest. In one of the key relevant proposals known as Networking Named Content (NNC), the premise is that leveraging in-network caching to store content in every node it traverses along the delivery path can enhance content delivery. We question such indiscriminate universal caching strategy and investigate whether caching less can actually achieve more. Specifically, we investigate if caching only in a subset of node(s) along the content delivery path can achieve better performance in terms of cache and server hit rates. In this paper, we first study the behavior of NNC's ubiquitous caching and observe that even naïve random caching at one intermediate node within the delivery path can achieve similar and, under certain conditions, even better caching gain. We propose a centrality-based caching algorithm by exploiting the concept of (ego network) betweenness centrality to improve the caching gain and eliminate the uncertainty in the performance of the simplistic random caching strategy. Our results suggest that our solution can consistently achieve better gain across both synthetic and real network topologies that have different structural properties. Keywords: Information-centric networking, caching, betweenness centrality. Information-centric networking (ICN) has recently attracted significant attention, with various research initiatives (e.g., [4] and COMET [5] ) targetting this emerging research area. The main reasoning for advocating the departure from the current host-to-host communications paradigm to an information/content-centric one is that the Internet is currently mostly used for content access and delivery, with a high volume of digital content (e.g., 3D/HD movies, photos etc.) delivered to users who are only interested in the actual content rather than the source location. As such, we no longer need a natively supported content distribution framework. While the Internet was designed for and still focuses on host-to-host communication, ICN shifts the emphasis to content objects that can be cached and accessed from anywhere within the network rather than from the end hosts only. In ICN, content names are decoupled from host addresses, effectively separating the role of identifier and locator in distinct contrast to current IP addresses which are serving both purposes. Naming content directly enables the exploitation of in-network caching in order to improve delivery of popular content. Each content object can now be uniquely identified and authenticated without being associated to a specific host. This enables application-independent caching of content pieces that can be re-used by other end users requesting the same content. In fact, one of the salient ICN features is in-network caching, with potentially every network element (i.e., router) caching all content fragments 1 that traverse it; in this context, if a matching request is received while a fragment is still in its cache store, it will be forwarded to the requester from that element, avoiding going all the way to the hosting server. Out of the current ICN approaches, NNC [2] advocates such indiscriminate content caching. We argue that such an indiscriminate universal caching strategy is unnecessarily costly and sub-optimal and attempt to study alternative in-network caching strategies for enhancing the overall content delivery performance. We address the central question of whether caching only at a specific sub-set of nodes en route the delivery path can achieve better gain. If yes, which are these nodes to cache and how can we choose them? Our contribution in this study is three-fold. First, we contribute to the understanding of ubiquitous caching in networked systems by providing insights into its behavior for specific topology types. Second, we demonstrate that selective instead of ubiquitous caching can achieve higher gain even when using simplistic random selection schemes. Third, we propose a centrality-driven caching scheme by exploiting the concept of (ego network) betweenness derived from the area of complex/social network analysis, where only selected nodes in the content delivery path cache the content. The rationale behind such a selective caching strategy is that some nodes have higher probability of getting a cache hit in comparison to others and by strategically caching the content at "better" nodes, we can decrease the cache eviction rate and, therefore, increase the overall cache hit rate. In the next section, we define the system of interest and layout our arguments and rationale with a motivating example illustrating that caching less can be more. We then describe our centrality-based caching scheme that can consistently outperform ubiquitous caching. We carry out a systematic simulation study that explores the parameter space of the caching systems, diverging from existing work in networked caches which mostly considers topologies with highly regular structure (e.g., string and tree topologies [6] [7] [8]), with the content source(s) usually located at the root of the topology forcing a sense of direction on content flows for tractable modeling and approximation. We present results for both regular and non-regular topologies, including scale-free topologies whose properties imitate closely the real Internet topology.
REF investigates if caching only in a subset of nodes along the path in ICNs can achieve better performance in terms of cache hit rate.
Cache “less for more” in information-centric networks
in Proc. of the IFIP-TC6 Networking Conference
Computer Science