# Dynamic-RPL: Enhancing RPL-Based IoT Networks with Effective Support of Dynamic Topology Management
## 3 Related Works  
The standard RPL specification [12] defines how PRL operates for a single-DODAG topology in a single-instance setup. However, the design of RPL supports the construction of multi-instance RPL networks and the formation of multi-DODAG topologies. Accordingly, several research efforts have been made to realize such potential functionality. Further research attempts have also been made to utilize this support for developing dynamic topology management. A brief overview of these research works is discussed in this section and a summary is presented in Table 1.  
The proposed work in [17] addressed multi-instance RPL network management to enable QoS-Differentiation over a single-sink DODAG. It was based on forming multiple logical DODAGs over the physical DODAG topology. Each logical DODAG then runs in a distinct instance applying a different OF. In [18], a similar approach was adopted to support effective multi-instance management over a DODAG but using a single tunable OF. In those cases where multiple instances can coexist over a single DODAG, the proposed solution in [19] provides dynamic multi-instance management. It enables the on-demand formation of an instance as per the network requirements of QoS-classified data traffic. Inactive or unwanted instances are removed after a certain configured time. The proposed architecture incorporated several software components such as an instance scheduler, message controller, and instance database. A different approach was proposed in [20] to enable a multi-DODAG topology to merge into a single-sink DODAG setup. The merged sink nodes then act as a virtual sink with each running a separate RPL instance. The nodes then perform dynamic instance attachment/detachment based on the current performance of the network. It was assumed that RPL operates in a non-storing mode for all the nodes. A similar approach was also proposed in [21] to address the dynamic management of multiple RPL instances over a single-DODAG topology. It enabled flexible node attachment to an instance in order to fulfill certain network traffic requirements. This was based on supporting effective cooperation among the instances to exchange instance information. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **Methodology** & **Multi-Instance** & **Multi-DODAG** & **Dynamic Management** & **Aggregate-Able Topology** & **Customized-OF** \\ \hline
[17] & Multi-instanced DODAG & \(\surd\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\
[18] & Single-OF multi-instance & \(\surd\) & \(\times\) & \(\times\) & \(\times\) & \(\surd\) \\  & management & & & & & \\
[19] & On-demand instance & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\  & formation & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\  & Dynamic node attachment to & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\  & multiple instances & \(\surd\) & \(\times\) & \(\surd\) & \(\times\) & \(\times\) \\  & A multi-DODAG coordination & & & & & \\  & framework & \(\times\) & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\  & Dynamic DODAG partitioning & \(\times\) & \(\surd\) & \(\surd\) & \(\times\) & \(\times\) \\  & Dynamic activation and & & & & & \\
[25] & deactivation of RPL nodes as sinks & \(\times\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\times\) \\ This Study & Dynamic multi-DODAG topology management & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary and comparison of related work. It can be noticed that these research works considered dynamic management of multiple instances over a simple DODAG setup. Other solutions were also proposed to address the dynamic management of multi-DODAG setups based on topological DODAG partitioning. The proposed work in [22] introduced a simple approach to enable dynamic multi-DODAG topology based on managing DODAG sizes. It defined a coordination framework for the sink nodes to exchange their DODAG and performance information using DIO and DAO messages.