# A Design for SDN-Based Identifier-Locator Separation Architecture on IoT Networks
## 1 Introduction  
Network environments are rapidly changing from wired access to wireless and mobile access network environments. As the number of mobile devices are increasing and the mobile market is growing explosively, mobility becomes one of the essential factors in mobile environments. Especially in the Internet of Things (IoT), one of the major technologies of the fourth industrial revolution, these mobile and sensor devices equipped with network functions are mainly used to collect data and extract valuable information such as temperature change, fire detection, and motion sensing from the data. The IoT is generally referred to the technology for connecting various objects to the internet and networks. IoT devices can communicate with others and transmit data via embedded communication and sensing devices to those objects. The Internet of Things is used not only to connect things to a network but also to control things through sensors and to analyze data collected from things. In particular, in upcoming smart urban environments, such as smart cities and smart factories, various things can be interconnected to send and receive a lot of information, and the IoT can be used to construct a safer and more convenient urban environment based on the collected and abstracted data [1; 2; 3; 4]. Things connected to the IoT need an address system that can uniquely identify each one in the network; therefore, devices are able to use internet protocol (IP) addresses as their identifiers (IDs) and locators (LOCs) to communicate with others and to bind a host and an application in the network. This binding provides some advantages for a wired and fixed network environment because the internet was originally designed for a fixed environment. Although it is important to consider the mobility function in today's network environment, this binding still has several drawbacks such as mobility, multi-homing, and extensibility problems. The exponential increase of mobile devices especially causes the difficulties of deployment and addressing in networks. Additionally, it is hard to maintain the routing table size of a default free zone (DFZ). Therefore, binding is not suitable for current mobile-oriented network environments. To provide a mobility function with scalable routing and addressing, the ID and LOC roles of IP addresses need to be separated for the future internet. Thus, ID-LOC separation protocols have been proposed [5; 6; 7; 8; 9; 10]. These proposed protocols use two namespaces as ID and LOC, and they are classified into two types: host-based protocols and network-based protocols. Host-based protocols, such as host identity protocol (HIP) and Shim6, require the modification of a protocol stack within the hosts and a rendezvous server for maintaining ID and LOC mapping information. Additionally, it has the problem of initial deployment in a network. In contrast, network-based schemes do not modify hosts' protocol stack [8; 9]. The end nodes do not participate in any signaling procedure. The ID-LOC mapping is processed by other network components such as routers, and they forward packets using tunneling according to the mapping information. The problems are bandwidth waste and processing overhead on the network caused by tunneling. Host-based and network-based protocols also require a centralized ID-LOC mapping system such as a rendezvous server and a map server. These problems cause the scalability problem. In this paper, we propose a software-defined networking (SDN)-based identifier-locator separation architecture for IoT networks. In the proposed scheme, a distributed hash table (DHT)-based ID-LOC mapping management scheme is adopted [9; 11]. The DHT is a kind of decentralized distributed system in which each node in the system holds key set such as \(<\)key, value \(>\) pairs. It is similar to a general hash table. The key sets are stored in a DHT, so the participating node can retrieve the value by using a given key. The basic features of a DHT are that it is decentralized, scalable, reliable, and fault resilient.