## 1 Introduction
In this paper, CoAP node indicates its sensor, which can provides the sensing resource, responses the request of another client, and is equipped CoAP protocol in the constrained network environment. As a CoAP sensor moves around different wireless networks, its IP connectivity may be disrupted, which may result in the loss of important sensing data, or delay of time-critical data. In CoAP, the IP address of CoAP node, is registered with the Domain Naming Server (DNS). The DNS configuration involves operation by humans as much as possible. If the CoAP server node moves between different IP domains, the client may not find the server location, _i.e._, IP address, if the human may not configure the changed IP address on DNS in time. To prevent the previously described mobility problem of a Web server node, an existing mobility management protocol may be used. The IETF has developed various standard mobility management protocols. The mobility management for network layer, Mobile IPv4/v6 (MIPv4/v6) [6] and its variants, including Fast Mobile IPv4/v6 (FMIPv4/v6) [7], Hierarchical Mobile IPv4/v6 (HMIPv4/v6) [8], and Proxy Mobile IPv4/v6 (PMIPv4/v6) [9] were developed. The transport layer uses TCP migrate and the mobile Stream Control Transmission Protocol [10]. For the application layer, SIP-based approaches [11] have been proposed to manage mobility in next-generation wireless networks. Unfortunately, most standard mobility management protocols add high signaling overhead from tunneling and binding operations, and are quite complex, incurring high processing and energy consumption. Additionally, most standard mobility management protocols require the modification of the network infrastructure such as Internet access router and mobile nodes. Furthermore, these standard mobility management protocols do not address the characteristics of a constrained IP network, such as limitations in packet size, high packet loss ratio, and sleep mode operation. Therefore, the protocols mentioned previously may not be suitable for mobility management in a WoT environment with constrained device and network characteristics; for example, with low processing and energy constraints, or in sleep mode operation. With regard to the objective functionality of mobility management, the objective of a WoT environment differs from that of existing IETF mobility management protocols. More specifically, in conventional IETF mobility management protocols, the objective of mobility management is to enable a mobile node to initiate a session and be provided with an application service in a seamless manner during an IP handover. In a WoT environment, however, the objective is to enable a mobile sensing node to timely send measured data to a remote client whenever the client requests it. Therefore, a WoT environment needs a novel mobility management protocol that can satisfy the previously described objective, considering constraints on processing capability, energy consumption, and other characteristics, such as sleeping mode operation. [PERSON] _et al._ presented a lightweight Mobile IPv6 with IPSec, which is aware of the requirements of the IoT and analyzes the efficiency and security adapted to IoT-devices capabilities [12, 13]. The authors proposed the lightweight Mobile IPv6, which does not execute the route optimization and return routability of the original Mobile IPv6, to be integrated into constrained devices with a low capacity in terms of memory and communication capabilities. Additionally, the authors investigated the requirements for supporting the mobility management in IoT environment [12]: global identifiers, IPv6-based protocol, communication costs, packet encapsulation, and movement detection. In the lightweight Mobile IPv6, the home agent and foreign agent play a role as middle agent in order to deliver the ingoing packet, _i.e.,_ control packet and real packet to the mobile node or corresponding node.