# MMNET: A Multi-Modal Network Architecture for Underwater Networking
#### 1.1.2 Difficult Route Forwarding  
The routing and forwarding of traditional UWSN depends on the node address. Even though the new software-defined network architecture (SDN) is based on the node address in the form of flow table to forward the packets [7, 9, 13, 14, 15, 16]. However, in UWSN, there may be such a situation as: Other underwater nodes in the same area may have the latest sensing data of the area, and the data consumers can ignore the information of the nodes themselves. Unlike using the node address to aggregate the sensing data, this scenario can use the data name to request the data, regardless of which node satisfies the data request. The requesting node requests data or content by sending a message containing the desired content name. Using names to represent data helps packets identify and discover different parameters or components of data [17, 18, 19, 20, 21, 22]. When any node with the required data receives the message of interest, it only needs to send the data message containing the required data. However, the existing network based on node address cannot support this routing and forwarding method based on name very well. Recently, people have proposed underwater named data networking (NDN) network architecture for this scenario, but these architectures are only designed for content-based routing and cannot support other routing methods, such as geographic-location-based routing. In order to meet the needs of various underwater routing methods, an extensible UWSN framework supporting multiple routing modes is needed. On the Internet, a variety of scalable network architectures are proposed to support different routing and forwarding, and new routing and forwarding protocols can  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Media**} & **Propagation** & **Data** & \multirow{2}{*}{**Distance/km**} & \multirow{2}{*}{**Media Dependency**} \\  & **Speed (m/s)** & & & \\ \hline MI & \(3.33\times 107\) & \(\sim\)M & 0.01–0.1 & Conductivity \\  & & & & Multi-path, Doppler, temperature, \\ Acoustic & 1500 & \(\sim\)K & 1–20 & pressure, salinity, environment \\  & & & & sound noise \\ Optical & \(3.33\times 107\) & \(\sim\)M & 0.01–0.1 & Light scattering, line of sight \\ RF(Radio & & & & communication, ambient light noise \\ Frequency) & \(3.33\times 107\) & \(\sim\)M & 0.01–0.6 & Attenuation \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of underwater MI (magnetic induction), acoustic, and optical communications.  
be extended smoothly. With the development of underwater applications, UWSNs also need scalability and corresponding capabilities.1.1.3. Applications That Are Difficult to Organize  
The current UWSN systems are usually application-oriented, and the system designed for one application cannot be applied to other applications [1; 2; 3; 4; 5]. With the development of underwater applications, the traditional application-oriented UWSN architecture has been unable to meet the increasingly complex requirements of underwater tasks. The existing network architecture cannot meet the needs of all tasks in a unified way. Under the support of the same network architecture, multiple applications interfere with each other, and cannot provide personalized network resources for each application, resulting in the application of each other to seize network resources, resulting in the waste of network resources, and may affect the normal operation of the entire network architecture function. Therefore, we need a network framework that can allow multiple underwater applications to run simultaneously on the same physical UWSN system without interfering with each other.