# IMU: A Content Replacement Policy for CCN, Based on Immutance Content Selection
###### Abstract  
In-network caching is the essential part of Content-Centric Networking (CCN). The main aim of a CCN caching module is data distribution within the network. Each CCN node can cache content according to its placement policy. Therefore, it is fully equipped to meet the requirements of future networks demands. The placement strategy decides to cache the content at the optimized location and minimize content redundancy within the network. When cache capacity is full, the content eviction policy decides which content should stay in the cache and which content should be evicted. Hence, network performance and cache hit ratio almost equally depend on the content placement and replacement policies. Content eviction policies have diverse requirements due to limited cache capacity, higher request rates, and the rapid change of cache states. Many replacement policies follow the concept of low or high popularity and data freshness for content eviction. However, when content loses its popularity after becoming very popular in a certain period, it remains in the cache space. Moreover, content is evicted from the cache space before it becomes popular. To handle the above-mentioned issue, we introduced the concept of maturity/immaturity of the content. The proposed policy, named Immutance Used (IMU), finds the content maturity index by using the content arrival time and its frequency within a specific time frame. Also, it determines the maturity level through a maturity classifier. In the case of a full cache, the least immature content is evicted from the cache space. We performed extensive simulations in the simulator (Icarus) to evaluate the performance (cache hit ratio, path stretch, latency, and link load) of the proposed policy with different well-known cache replacement policies in CCN. The obtained results, with varying popularity and cache sizes, indicate that our proposed policy can achieve up to 14.31% more cache hits, 5.91% reduced latency, 3.82% improved path stretch, and 9.53% decreased link load, compared to the recently proposed technique. Moreover, the proposed policy performed significantly better compared to other baseline approaches. c ARTIC 2021 27 December 20  
naturally supports in-network caching and many-to-many communication [4]. When the user request contains the name or identification of the desired data object, the network attempts to respond to the request with the data object. The name can also belong to a location or a host machine. This mechanism makes CCN more general than the host-to-host communication model [5]. In-network caching provides a solution for traditional Internet architecture that works in the application layer [3]. The content of the CCN cache changes rapidly due to enormous data demands. Furthermore, CCN is a solution that works on the network layer level [6]. It allows the CCN node to cache a temporary copy of the requested content. CCN can minimize network traffic and maximize content availability by providing the desired content closer to the consumer [7]; it is difficult to decide the cache location of the content to satisfy consumer requests and improve network performance [8]. In addition, it is also important to determine which content should be removed from the cache space to accommodate new content in the cache. Improper content selection causes the degradation of network performance [9]. In-network caching faces several challenges, including limited cache storage, caching replacement and placement, caching traffic, and complex network topology [10, 11]. The performance of the CCN depends on the content placement and replacement policies. The content placement policy decides the appropriate cache location of each content [1]. Hence, the node selection for content caching should be optimized to satisfy consumer requests, with minimum overhead. Due to the limited cache capacity in the node, any cached content in the cache needs to be removed to accommodate new content [12].