## 3 The Concept of Building the EviNS Software Framework
However, with sufficient connectivity within the hydroacoustic network, data transmission can occur through neighboring participants who are within a working distance from the desired data sources or recipients. These neighboring participants contribute to redirecting the data flow in the correct direction. To address this challenge, the EviNS software framework incorporates two specialized data routing protocols, i.e., static routing and avalanche routing, both of which control the number of transmitted packets. According to the static routing protocol, each network participant is pre-assigned one of the two roles: either a relay or a passive participant. Upon receiving a data packet, the relay participant forwards it to the next address (also pre-assigned) of another relay participant, and this process continues until the data reaches its final recipient. While this protocol can be efficient in terms of energy consumption and data delivery time, it suffers from limited applicability due to the inability to alter the geometry of the hydroacoustic network after it has been deployed underwater. The second protocol is designed for networks with rapidly changing geometries (such as those involving mobile participants like Autonomous Underwater Vehicles (AUVs)). While it may be redundant in terms of the amount of transmitted data within the network (and consequently, energy consumption), it reliably functions with any network dynamics. Under this protocol, each network participant determines the current data packet number that they have received. If a packet is not intended for them and is received for the first time, they redirect it to other network participants within their working range. This process continues until the package reaches its intended recipient. The utilization of these protocols in practical scenarios was conducted as a part of a study in [25]. This study investigated the performance characteristics of a digital hydroacoustic network built upon these protocols, as well as the advantages and disadvantages associated with their practical use. The findings revealed that the combination of properties inherent to these protocols confers an advantage to users in networks with dynamically changing geometry--such as acoustically interconnected cooperative or coordinated groups of fast-moving AUVs. Notably, these advantages encompass minimal transmission time and the highest probability of successful data delivery to the ultimate recipient within the network. However, it is essential to acknowledge that the specific energy consumption for transmitting a unit of information within such a network is relatively high (attributable to frequent data delivery route duplication). Consequently, the autonomous operational duration of such a network remains relatively short. In the following section, the implementation of a number of network and link layer protocols that were developed and deployed by the authors within the EviNS software framework is presented. This implementation is capable of functioning in a dynamic network. However, in cases of rapid changes in network geometry, it may struggle to adapt to the evolving connections among its mobile participants. Under this protocol, network participants periodically search for and reassign data delivery routes (for relatively short periods). During data transmission, packets are only forwarded by those participants included in the updated route and designated as relay nodes. It is expected that the use of this protocol will result in relatively low levels of excess data transmission in the network (and consequently, lower energy consumption) compared to avalanche routing. However, this protocol is not intended for use in networks with rapidly changing geometries. In other words, the presented implementation of this network-level protocol strikes a compromise between network dynamics and energy efficiency and is limited to applications where such a compromise is acceptable.