## 5 Enhancing QoS and QoE in ICN
### SDN-Based ICN Solutions  
Software-defined networking (SDN) [89] is essential for enhancing and managing QoS and QoE in modern networks due to its centralized control and traffic engineering capabilities. SDN separates the control plane from the data plane [90], allowing efficient resource allocation, load-balancing congestion control, and traffic prioritization, all of which are essential to maintaining high QoS and QoE. SDN plays a pivotal role in advancing ICN by enabling dynamic control and programmatically efficient management of network resources. SDN enhances ICN's content distribution, caching, and retrieval capabilities by providing a centralized platform for managing content routing, caching policies, and QoS requirements. SDN controllers leverage a variety of protocols, such as OpenFlow, to communicate with forwarding devices, enabling real-time adjustments to network policies and traffic flows. In addition, SDN allows for the seamless integration of ICN with existing network infrastructures, facilitating incremental deployment and migration strategies. One strategy used by some research works in this domain is utilizing the traffic engineering ability and independent control layer of SDN. [PERSON] et al. [91] proposed an information-centric wireless network virtualization technique that transmits time-sensitive multimedia data with the delay-bounded QoS guaranteed in SDN environments. The authors combined the inherent advantages of SDN with the in-network caching feature of ICN to provide maximum effective capacity and minimum transmission delay. [PERSON] et al. [92] utilized the SDN controller to keep track of the routing information for mobile users in an NDN environment and showed improvement in several QoS metrics. Another strategy adopted by some SDN-based approaches is implementing an intermediate layer to translate names into IP addresses. This layer, often functioning as a proxy and overlay, is prevalent in modern networks where proxy servers are common. Several works [93; 94; 95] have leveraged proxy servers to manage ICN networks efficiently. [PERSON] et al. [94] utilized a proxy to envelop and hash messages between the CCNx daemon and the OpenFlow switch. This proxy's wrapper module hashed the content name prefix in the interest packet and embedded it within the existing IP packet. The authors considered off-path caching and addressed cache replication issues to enhance hit ratios. However, the wrapper added a slight delay and marginally reduced forwarding efficiency by 5%. [PERSON] et al. [95] employed multiple proxies, each including a shared and distributed hash table that served as the content index. Upon receiving interests, the controller directed them to the nearest proxy for data retrieval. If the proxy located the requested data in its hash table, it sent the interest to the cache node holding the data; otherwise, it forwarded the interest to the closest proxy server. However, this method risks overloading proxies as they handle all interests by resolving and forwarding them to the controller. [PERSON] et al. [96] proposed an SDN-based NDN architecture to support IP-compatible ICN packets. The Multi-Protocol Label Switching (MPLS) technique was used to encapsulate and label the NDN payload within IP packets. [PERSON] et al. [97] presented an OpenFlow-compatible key-based routing solution to enable content-centric networks to be deployed on the current TCP/IP-based architecture. End hosts were distinguished by virtual identifiers utilized for network communication. This SDN-over-ICN model demonstrated improved transmission efficiency and high QoE. Table 4 lists various ICN frameworks that utilize SDN to enhance QoS and QoE metrics. Comparative Analysis of SDN-Based Strategies  
To compare the strategies listed in Table 4, we can categorize them into the following subgroups: (i) optimized centralized management and (ii) NFV-based solutions. The first category leverages the global view and programmability of SDN to enhance core ICN functions.