On the Complexity of Optimal Request Routing and Content Caching in Heterogeneous Cache Networks
Mostafa Dehghan,Bo Jiang,Anand Seetharam,Ting He,Theodoros Salonidis,Jim Kurose,Don Towsley,Ramesh K. Sitaraman +7 more
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This work investigates the problem of developing optimal joint routing and caching policies in a network supporting in-network caching with the goal of minimizing expected content-access delay and identifies the structural property of the user-cache graph that makes the problem NP-complete.Abstract:
In-network content caching has been deployed in both the Internet and cellular networks to reduce content-access delay. We investigate the problem of developing optimal joint routing and caching policies in a network supporting in-network caching with the goal of minimizing expected content-access delay. Here, needed content can either be accessed directly from a back-end server (where content resides permanently) or be obtained from one of multiple in-network caches. To access content, users must thus decide whether to route their requests to a cache or to the back-end server. In addition, caches must decide which content to cache. We investigate two variants of the problem, where the paths to the back-end server can be considered as either congestion-sensitive or congestion-insensitive, reflecting whether or not the delay experienced by a request sent to the back-end server depends on the request load, respectively. We show that the problem of optimal joint caching and routing is NP-complete in both cases. We prove that under the congestion-insensitive delay model, the problem can be solved optimally in polynomial time if each piece of content is requested by only one user, or when there are at most two caches in the network. We also identify the structural property of the user-cache graph that makes the problem NP-complete. For the congestion-sensitive delay model, we prove that the problem remains NP-complete even if there is only one cache in the network and each content is requested by only one user. We show that approximate solutions can be found for both cases within a $(1-1/e)$ factor from the optimal, and demonstrate a greedy solution that is numerically shown to be within 1% of optimal for small problem sizes. Through trace-driven simulations, we evaluate the performance of our greedy solutions to joint caching and routing, which show up to 50% reduction in average delay over the solution of optimized routing to least recently used caches.read more
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The Role of Caching in Future Communication Systems and Networks
TL;DR: Caching has been studied for more than 40 years and has recently received increased attention from industry and academia as mentioned in this paper, with the following goal: to convince the reader that content caching is an exciting research topic for the future communication systems and networks.
Proceedings ArticleDOI
It's Hard to Share: Joint Service Placement and Request Scheduling in Edge Clouds with Sharable and Non-Sharable Resources
TL;DR: A constant-factor approximation algorithm for the homogeneous case and efficient heuristics for the general case are developed, which show that while the problem is polynomial-time solvable without storage constraints, it is NP-hard even if each edge cloud has unlimited communication or computation resources.
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Joint Optimization of Caching, Computing, and Radio Resources for Fog-Enabled IoT Using Natural Actor–Critic Deep Reinforcement Learning
TL;DR: This paper simultaneously tackles the issues of content caching strategy, computation offloading policy, and radio resource allocation, and propose a joint optimization solution for the fog-enabled IoT and uses the actor–critic reinforcement learning framework to solve the joint decision-making problem.
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Online Collaborative Data Caching in Edge Computing
TL;DR: An online algorithm, called CEDC-O, is proposed, developed based on Lyapunov optimization, works online without requiring future information, and achieves provable close-to-optimal performance.
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