# Quality-of-Service-Linked Privileged Content-Caching Mechanism for Named Data Networks
###### Abstract  
The domain of information-centric networking (ICN) is expanding as more devices are becoming a part of connected technologies. New methods for serving content from a producer to a consumer are being explored, and Named Data Networking (NDN) is one of them. The NDN protocol routes the content from a producer to a consumer in a network using content names, instead of IP addresses. This facility, combined with content caching, efficiently serves content for very large networks consisting of a hybrid and ad hoc topology with both wired and wireless media. This paper addresses the issue of the quality-of-service (QoS) dimension for content delivery in NDN-based networks. The Internet Engineering Task Force (IETF) classifies QoS traffic as (prompt, reliable), prompt, reliable, and regular, and assigns corresponding priorities for managing the content. QoS-linked privileged content caching (QLPCC) proposes strategies for Pending Interest Table (PIT) and content store (CS) management in dedicated QoS nodes for handling priority content. QoS nodes are intermediately resourceful NDN nodes between content producers and consumers which specifically manage QoS traffic. The results of this study are compared with EQPR, PRR probability cache, and Least Frequently Used (LFU) and Least Fresh First (LFF) schemes, and QLPCC outperformed the latter-mentioned schemes in terms of QoS-node CS size vs. hit rate (6% to 47%), response time vs, QoS-node CS size (65% to 90%), and hop count vs. QoS-node CS size (60% to 84%) from the perspectives of priority traffic and overall traffic. QLPCC performed predictably when the NDN node count was increased from 500 to 1000, showing that the strategy is scalable. Named Data Network (NDN); information-centric networking (ICN); quality of service (QoS); Internet of Things (IOT) +
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through the node temporarily. If the consumer request matches with the data available in the CS, then the interested data is served; otherwise, the content name, along with its associated incoming interface (information of neighboring node from which the interest packet was received), is recorded in the PIT. If the content name entry already exists in the PIT, indicating that there are other consumers waiting for the said content, then the incoming interface of the new interest is added to the content name entry of the PIT. The unsatisfied interest packet is forwarded to next node. An FIB maintains the interfaces of the neighboring nodes. The content names in the PIT are alive until the request is either satisfied or dropped due to expiry of time, pre-emption, etc. The sequence of interest-packet forwarding repeats until the interest reaches either the source of the content, or any CS of intermediate nodes where valid content is present. Once the content is found in an NDN node, the data packet (with requested content) traverses the reverse path by referring to the PIT entry and its associated interfaces to reach the consumers. The CS of the NDN nodes along the path may decide to cache the traversing content, depending upon their admission control strategy. The unique feature of an NDN is that every time a consumer requests content, the request need not be satisfied by the producer of that data. Intermediate nodes may have cached the data in their CS, and the data can be served directly from a CS. Content names are organized in a hierarchical manner, and are addressed as depicted in Figure 1 [4]. There is increasing research towards employing NDNs for communication network applications [5; 6; 7]. Research studies [8; 9] conclude that NDNs can constitute reliable network-layer protocols for networks with acceptable network throughput and latency. A survey of the existing literature shows that there is very little exploration on the QoS properties of NDNs from the context of content caching for networks which use a low-power network architecture, such as the Internet of Things (IOT).