## 1 Introduction
Specifically, when data are forwarded through a cache node, DRAM inserts the data into the local cache based on the cache decision results, while the input load on the SSD primarily comes from the data replaced by DRAM. As a result, the SSD experiences lower cache load and replacement frequency, allowing for more refined replica management with relatively small overhead. On the other hand, due to the filtering effect of the upper-layer cache on the workload, the request arrival patterns in the lower-layer cache tend to be different. This characteristic can be leveraged to implement differentiated cache replacement policies across multiple cache layers, adapting to their respective request access patterns, thereby improving overall cache hit rate. To address the above issues, this paper proposes a cache management scheme oriented towards hierarchical cache architectures in ICN. In the following text, we will refer to it as the hierarchical cache management policy (denoted as HCM). The core ideas of HCM are as follows:* A differentiated cache replacement policy is proposed to accommodate the varying request access patterns across different cache layers. At the DRAM cache layer, LRU is used to prioritize retaining short-term popular data. At the SSD cache layer, a multi-queue replacement policy based on cache utility is implemented, with the goal of storing higher-utility data (such as long-term popular data or data with high retrieval costs) in SSDs for a longer period;
* Considering the limited lifespan of SSDs, a probabilistic insertion-based SSD cache admission filtering mechanism is introduced. By leveraging the redundancy and popularity attributes of data in ICN, this mechanism effectively reduces the write load on the SSD while improving the overall cache hit rate. We conducted extensive simulations based on Icarus [16] and comprehensively evaluated the performance of HCM under various application scenarios using performance metrics such as cache hit rate, network link load, and SSD write load. The experimental results show that HCM consistently demonstrates significant cache performance advantages under different request workloads and replica placement strategies, highlighting its wide applicability across multiple application scenarios. Furthermore, HCM is able to maintain stable performance gains under different cache capacity settings, demonstrating its excellent scalability. It should be noted that the approach proposed in this paper is not limited to ICN. It can also be applied to other distributed caching and storage scenarios, where nodes may utilize a multi-level cache hierarchy consisting of DRAM and SSD. Designing efficient cache replacement policies to improve cache resource management and system performance is equally crucial in these contexts. The ideas of SSD cache filtering and hierarchical cache replacement in HCM can be effectively applied to such environments as well. However, in this paper, we focus on the ICN context for the following reasons: First, the coupled nature of forwarding and caching in ICN presents unique challenges for cache management. For example, the limited resources of routers constrain the complexity of cache management, and features such as on-path caching impose higher demands on write throughput. On the other hand, symmetric routing in ICN, along with features like ubiquitous and transparent caching, provides greater flexibility and design space for cache management schemes. Therefore, while the HCM method has broader applicability, exploring it within the ICN context allows us to address specific challenges and optimize cache management schemes for this network architecture. The remainder of this paper is organized as follows. Section 2 provides an overview of the hierarchical cache architecture in ICN and related research on ICN cache replacement. Section 3 introduces the hierarchical cache management architecture designed in this paper. Section 4 elaborates on the hierarchical cache management policy and its core components.