# ICN-Based Enhanced Content Delivery for CDN
## 2 Background and Related Work
### Related Work  
CDN and ICN are two network paradigms proposed to enhance the content distribution efficiency in the presence of service limitations in current IP networks. Previous studies regarding the discussion of these two paradigms can be classified into two broad classes:  
1. Comparative studies: These studies have attempted to conduct comparative analyses of these two paradigms to evaluate their respective performance bounds. In their research, [PERSON] et al. [27] discussed the differences between CDN and NDN in terms of distribution efficiency, protocol overhead, security, robustness, and cost, and testbed research was conducted to compare the data transmission efficiency of the two paradigms, with the conclusion being that NDN outperforms CDN under the same network topology and cache storage budget. In [28], [PERSON] et al. constructed comparable testbeds on cloud computing platforms for CDN and CCN separately to systematically compare their performance metrics in content delivery capability. This research found that CCN is comparable to CDN, even though it introduces overhead in content chunk decoding and restructuring. [PERSON] et al. [29] studied the performance bounds of these paradigms using optimization models and proposed a comparative model to gauge the performance difference of a CDN with respect to CCN. The results showed that, under the same total caching storage, CDN can have slightly better performance than CCN. In [30], real-world experiments were conducted to compare the performance of NDN and two leading CDNs (Akamai and Fastly). The results showed that although NDN can provide satisfactory service, it lags behind CDN due to the hardware infrastructure and software/protocol immaturity. NDN outperforms in terms of server load balancing and failure resiliency enabled by ubiquitous caching. The comparative studies have shown that ICN does not necessarily outperform CDN in terms of content distribution efficiency; however, it is favorable in terms of lower management cost and better resiliency. Rather than being two separate models, these two can be explored to complement each other. 2. Hybrid studies: Some prior research proposed to integrate CDN and ICN using hybrid approaches to achieve better performance. Ref. [31] proposed a named content delivery network called nCDN, which embeds NDN into the existing CDN framework by setting up NDN running over UDP/TCP to simplify the implementation and improve efficiency. In nCDN, ICN is only in charge of request routing and content delivery. Similarly, in [32], the authors borrow the ICN name-based routing idea and integrate it into the CDN architecture with a centralized routing engine to fully exploit the ISP underlay network infrastructure. In [33], [PERSON] et al. integrate NDN with CDN as two network slices with the technology of Network Function Virtualization (NFV). In this architecture, NDN serves as a service slice designated for request routing and in-network caching over a specific region. The CDN slice is considered the content publisher of the NDN slice. Upon the first request for a particular content, the content is retrieved from the CDN service slice and simultaneously published to the NDN slice. Instead of building a CDN using NDN by the direct borrowing of the NDN network, the authors in [34] proposed another CDN-NDN architecture called iCDN, with two major mechanisms: first, to fully utilize in-networking caching, iCDN builds a cache hierarchy with the CDN full-mesh topology to exploit on-path and off-path caches and cuts the forwarding plane's dependency on routing information; second, iCDN introduces a new forwarding strategy for enabling the forwarding plane to make efficient decisions. [PERSON] et al. [35] designed a CDN architecture over MobilityFirst in the application layer so that minor modification is needed for existing protocol stack. Meanwhile, it uses a self-certifying naming schema to enable low-cost, efficient content validation and uses proactive caching to further improve the performance of CDN.