## 1 Introduction  
With the explosive growth of the scale of Internet users and the network traffic, the Internet has grown into a bloated giant. According to the Cisco Annual Internet Report (2018-2023) [1], VR and HD video will take up most of the network traffic. In this context, the main goal of the Internet has gradually shifted from the point-to-point connection to the acquisition and distribution of contents. To meet this goal, the Information-Centric Network (ICN) has been considered as an important way to improve the existing network. By decoupling contents from the address and enabling in-network caching, ICN can better support some features such as mobility, multicast, and multi-hosting. With in-network caching, the ICN caching routers (or caching nodes) cache contents and provide content services, resulting in a lower latency in acquiring content and a smaller link traffic load on servers. In recent years, various ICN architectures have been proposed, such as CCN [2], DONA [3], COMET [4], and PURSUIT [5]. ICN architectures can be divided into two categories when it comes to content discovery mechanisms accordingly. One category is routing-by-name, which couples content routing with the name of contents. A typical representative is CCN, which maintains a PIT (Pending Information Table) for request information and an FIB (Forwarding Information Base) table for content forwarding information. This mechanism requires ICN routers to handle mass storage and content information updates. The second category is routing-by-resolution, which utilizes a dedicated device named Name Resolution System (NRS). Basically, the NRS is responsible for recording the mapping of the cached content and its caching location. In this way, users can get the NA (Network Address) of the content from the NRS. For example, DONA deploys at least one logical NRS in each autonomous system. The routing-by-resolution mechanism makes routers concentrate on routing and caching, thus alleviating their computing pressure. Correspondingly, the NRS needs to handle a large number of content name queries and updates. According to [6], NRS currently supports larger than \(10^{15}\) content indexes. Another problem with the routing-by-resolution mechanism is the communication overhead with the NRS. To face this, some research focused on providing deterministic delay resolution services in the NRS [7]. As the core function of ICN, in-network caching has received a lot of attention. Different from Content Dilvery Network (CDN), caching in ICN works at the network layer. Furthermore, ICN requires the caching router to be able to cache contents during their transmission and requires ensuring the wire-speed forwarding function, which makes it difficult for ICN to adopt a centralized content placement strategy. For simplicity, we use the term \"caching strategies\" instead for distributed content placement strategies in this paper. At present, a large number of caching strategies have been proposed to meet different optimization goals or application scenarios, such as Leave Copy Everywhere (LCE), Leave Copy Down (LCD [8]), Cache Less For More (CL4M [9]), and PROB [10]. However, the majority of the caching strategies are based on the routing-by-name mechanism, and only a few come from the routing-by-resolution mechanism. According to the information provided by the NRS, users can find the nearby content replica easily, and the routing-by-resolution mechanism can increase the hit ratio of the in-network cache and further reduce the server load. Therefore, how to design an appropriate caching strategy in the scenario with an NRS is worth further study. Furthermore, two intractable problems limit the performance of traditional ICN caching strategies. One is improper distribution of contents. Aforementioned strategies do not consider information about cached contents when caching a new content, which makes it difficult for caching routers to persistently cache popular contents, resulting in low cache performance.