## 4 Proposed LOADng Enhancement for IoT Networks
### Considered IoT Applications and Network Model  
This work considers an IoT network as presented in Figure 1. The network is composed of simple nodes and Internet-connected nodes, hereafter referred to as INs. The simple nodes represent devices with low capacity, equipped with IEEE 802.15.4, which are unable to realize a direct Internet connection. On the other hand, INs represent devices with high potential, equipped with IEEE 802.15.4 and another communication interface, which are able to provide direct Internet connectivity (such as 4G, Ethernet, or Wi-Fi). All of the network nodes can generate simple messages, which are sent to any network node, and Internet messages, which are directed to external Internet services. The simple messages are locally generated and processed by the nodes. In contrast, Internet messages are created locally and need to reach external services using the Internet. Thus, the INs can directly send Internet messages once they have Internet connectivity. However, simple nodes that generate Internet messages need to find an IN to work as a gateway so that they can then forward their packets. Thus, an IN that receives an Internet message from a simple node should handle and forward the message to the final IP destination using other communication interfaces.  
A smart home (SH) IoT application can be used to exemplify the use of the presented network model. In a SH, the smart objects with a low necessity of consulting external Internet services (such as lights, windows, doors, showers, and air-conditioners) can be represented by simple nodes. In contrast, smart objects that require continuous Internet-connection (such as smart meters, smart TVs, smartphones, tablets, and routers) can be represented by INs linked to the Internet using cellular network or optical fiber. Thus, as an example, a smart window can occasionally consult an external Internet service to verify the weather forecast. The smart window, to access the service, should use an IN as its gateway to the Internet. Besides, in a context of a local message exchange, an air-conditioner, when activated, can send a local message to close the smart windows without the necessity of using the Internet to perform this communication.  
Current routing solutions can address the presented network model when the simple nodes have been previously configured with a default gateway to forward their Internet messages. Thus, prior knowledge of the nodes with Internet connection capacity is required to then define a gateway for each simple node. This approach, although functional, can give rise to several issues. The obstacles that can occur using this simplistic approach are identified as: (i) high deployment time is required to define the gateway of each simple node; (ii) Internet-connected nodes can be overloaded with Internet messages from simple nodes; (iii) bad deployment can make simple nodes create long paths to their gateways; (iv) simple nodes can become unable to send Internet messages if their gateways lose Internet connectivity.  
Based on the exposed constraints, and seeking to better address the requirements of the described IoT network scenario, this work proposes a new enhancement for the LOADng protocol that is able to optimize the route discovery process for INs and improve the network performance. The proposed LOADng-IoT can simplify the discovery of Internet routes, avoiding the necessity of the prior definition of gateways for Internet messages. In addition, the proposal reduces the number of control messagesrequired to construct paths to INs and makes the data message forwarding process more reliable. The following subsections present a detailed description of the proposed LOADng-IoT.