## 1 Introduction  
The traditional network architecture has strongly supported the vigorous development of the Internet over the years. However, it has become gradually insufficient [1] as the current usage of the Internet is increasingly focused on content retrieval and dissemination, while its transmission architecture, proposed in the 1960s, is still based on the end-to-end communication paradigm. The mismatch between the location-based routing and the distributed retrieval schemes is the basic reason for several significant insufficiencies of the Internet [2]. Such as security, mobility management, and scalability. Based on the above background, the future networks proposed to overcome the shortcomings of the traditional Internet has become a research hotspot, and ICN is considered one of the most influential solutions in many scenarios [3]. The primary difference between ICN and the existing Internet is that the former focuses on the content itself rather than its location. The shift from host-to-host to content-centric in ICN provides a natural solution to most of the issues faced by the IP infrastructure today, which are accrued by current Internet trends. The current representative ICN architectures are Data-Oriented Network Architecture (DONA) [4], Publish/Subscribe Internet Routing Paradigm (PSIRP) [5], Network of Information (NetInf) [6] and MobilityFirst [7, 8], Content-Centric Networking (CCN) [9] in Named Data Networking (NDN) project [10]. In addition, some are designed to smoothly transfer from the current network to ICN [11]. The first-class citizen in ICN is the content,not the end host. By naming content at the network layer, ICN supports name-based routing, which decouples routing from the location. Furthermore, all of the candidate ICN architectures share a fundamental principle of universal in-network caching. In-network caching, one of the most essential features of ICN, is used to store data packets for future retrieval [12], and its benefits can be roughly divided into three categories [13]: From the perspective of Internet Service Provider, the in-network caching can resolve the requests for stored content, so those content will not be repeatedly transmitted in the core network. By offloading the core network traffic to each autonomous system, the traffic load on the core network is greatly reduced. From the perspective of the content provider, the traffic load on the content server can also be reduced, because the in-network caching prevents the requests to the content server. From the perspective of the user, in-network caching is closer to users compared with content providers, which reduces the latency for users to retrieve content objects. The benefits that in-network caching brings are particularly similar to those of the content distribution network (CDN) [14]. And the success of commercial CDN proves the effectiveness of in-network caching. Improving caching performance is a hot issue in the current related research fields of ICN. To realize in-network caching, network nodes (nodes and routers are not distinguished in this paper) are equipped with content storage composing the caching network. The cache is only equipped on specific nodes in CDN, and its access rate is not high. Thus, low-cost hard disks can be used as storage media, which makes the content storage space almost infinite. However, ICN requires line-speed execution for caching and therefore has higher requirements for storage media. On the one hand, these high-speed storage media are expensive; on the other hand, the maximum capacity of these high-speed storage media is limited. Consequently, the total amount of cache in ICN is limited. A reasonable cache size allocation scheme can make the best of the limited cache space to result in better performance. The goal of our work is to make the most of the given total cache budget by allocating it to each node in the network effectively.