# A Dual-Connectivity Mobility Link Service for Producer Mobility in the Named Data Networking
## 2 Named Data Networking  
NDN reorganizes the existing Internet communication paradigm based on information. This is a concept that attaches great importance to the information itself, not the place. Instead of designating a location such as an IP address, information is considered to be the best independent subject by giving the information a unique identifier or name. Given that the public Internet is getting more crowded, implementing the Internet that focuses on the information itself increases flexibility. It could optimize the flow of information and eliminate the congestion of the points through which information passes.  
In NDN communication, a consumer requests a specific content to a producer through an Interest packet. The producer transmits the content requested by the consumer in the Data packet [2]. Additional data structures such as Content Store (CS), a Pending Interest Table (PIT), and a Forwarding Information Base (FIB) are defined for such a content-based communication. The CS is a local cache for Data packets that have been passed through the NDN node. The PIT records pending Interests that have yet to be served. Each PIT entry aggregates the same Interests it receives and remembers incoming NDN faces so that it can build reverse paths for the Interests for data packet forwarding. The FIB is used to forward Interests toward NDN nodes, which have the corresponding content for the Interests. The reference implementation of NDN has been published [18]. The Named Data Networking Forwarder (NFD) implements the core NDN structure.  
The NFD interacts with other components via common interface objects called Faces, which are responsible for connection management. A Face can connect the NFD with local applications as well as other local NDN modules, such as the RIB, or remote Faces located at other NDN nodes. The face consists of two components: link service and transport. The NDN link service is a component of the NDN face, and it is responsible for managing the connections between two NDN nodes. The NDN faces connect NDN nodes and transport Interests and Data packets between them [19]. The faces are generated when a new association is detected between two NDN nodes, and they are removed when the connectivity between two NDN nodes is broken. When the producer changes its point of attachment to a new NAR (nNAR), the current NDN faces connecting the producer with the previous NAR (pNAR) are removed and new NDN faces are created to connect the producer with the nNAR. The producer then registers its content to the nNAR via the new NDN faces. The NLSR routing protocol at the nNAR announces the presence of the contents to the NDN routers on the network. Until new routing information is disseminated over the network, many Interests sent to the producer may not reach the producer. These lost Interests usually arrive at the out-of-date pNAR.  
The Routing Information Base (RIB) interacts with the FIB via a local Face to manage the FIB. A Name-based routing protocol such as the NLSR [7] interacts with the RIB to install the routing information taken from other NDN router nodes. The RIB includes the Auto Prefix Propagator (APP), which registers local content prefixes to the remote RIB at the current NAR using command Interests [20]. When the remote RIB receives command Interests, it updates its FIB in the NFD and the local content prefixes in the NLSR to accurately reflect the received content prefixes.