## 2 Related Work
### Scalability  
Scalability is a key issue for ICN name resolution design. For hierarchical name-based NRS, scalability can be improved by aggregating the hierarchical names. For the flat name based NRS, since flat names are difficult to aggregate, the hierarchical aggregation of the flat names can be realized based on domain division. [PERSON] et al. proposed a scalable Name-based Inter-Domain Routing (NIDR) system based on hierarchical naming to support the resolution of large-scale information objects, as well as to reduce the inter-domain traffic [23]. NIDR adapts two key technologies to increase its scalability. Firstly, NIDR utilizes a URL-like content naming structure and routes by the domain name of the content name rather than the full content name. Secondly, only a small subset of Internet domain names were announced at the inter-domain level. Domain names unknown to the NIDR system were first mapped (and routed) to their corresponding Attachment Point (AP) networks in the NIDR by a name resolution service. By limiting the number of domain names, NIDR systems can reduce the control overhead and improve the scalability of the NRS. [PERSON] et al. proposed a CCN-based name mapping system (NRS-MS), which provides name resolution services for CCN [24]. The NRS-MS saved and maintained the mappings of names, such as name-to-name and name-to-locator. NRS-MS added the name resolution step to address the scalability issue of CCN routing and to support producer mobility in ICN. [PERSON] proposed an approach using a popularity-aware intra-domain mobile content management model, on the basis of which the NRS tracks the current location of mobile content only when the content has a sufficiently high popularity and sufficiently low mobility, while it discovers low popularity/highly mobile content via broadcasting [25]. Scalability gains lie in reducing total signaling and memory requirements of the NRS. One popular approach to improve the scalability for flat name-based NRS is to use a DHT-based routing method to store the name bindings in appropriate resolvers via hash functions. Nested and hierarchical DHT architecture were utilized to implement distributed and scalable NRS based on flat names, such as Multi-level Distributed Hash Table (MDHT) [22], Hierarchical Distributed Hash Table (HDHT) [26], Scalable Multi-level Virtual Distributed Hash Table (SVMDHT) [27], and Hierarchical Pastry (H-Pastry) [28]. However, the administrative scope of the DHT mechanism is a prominent problem [20], and the existing methods have almost no specific solutions to solve the problem of hierarchical and nested area division and management. [PERSON] et al. proposed a container structure to represent the residing place of content or information objects for scalable routing of flat names [29]. This article utilized a hierarchical container rather than hierarchical naming to improve the system scalability. In addition, to improve the manageability of the container, a nested structure was adopted to allow recursive querying. The concept of a container can be extented to real-world networks, for example, local, regional, or Internet Service Provider (ISP). [PERSON] et al. [30] demonstrated the feasibility of deploying DONA by leveraging cloud computing facilities and discussesed the potential of cloud technologies towards enhancing the scalability of DONA. To overcome the shortcomings of DHT, NRSs based on Bloom Filter (BF) were proposed. BF is mainly used to check whether an element exists in a set and can be used as the aggregating information of the existential state of the flat name, which can help improve the system scalability. BF has two major benefits: one is that BF has a fixed constant time of insertion and search, which is completely independent of the number of names that already exist in the set. Another important and powerful property of bloom filter is the efficient support for the union of bloom filters with the same size and set of hash functions, which can be implemented with bitwise OR [31]. [PERSON] et al.