## 2 Selected Routing Protocols
OLSRv2 is a proactive routing protocol that builds upon the core algorithms of OLSR while introducing new features, such as routing multipoint relay (MPR), flexible link metrics, and extensible message formats. It consists of three primary components: neighborhood discovery, MPR selection, and topology establishment. OLSRv2 utilizes two types of control messages: HELLO and TOPOLOGY CONTROL (TC). The neighborhood discovery process enables nodes to identify their one-hop neighbors within radio range. During this process, HELLO messages convey link status information, indicating whether a link is symmetric, asymmetric, or a multipoint relay. Neighborhood discovery is complete once a bidirectional link between two nodes is established. OLSRv2 also employs two methods for MPR selection, flooding MPR selection and routing MPR selection, with flooding MPR selection being important for managing traffic forwarding across the network. Flooding MPR selection is used to reduce control traffic in the network and boost the efficiency of the routing protocol. To form an MPR set, each node is required to select potential candidates from its bidirectional neighbors. Only those nodes that belong to the MPR set are allowed to forward control traffic. Routing MPR selection is similar to flooding MPR selection, but its purpose is to minimize the network topology. Nodes that are not included in the MPR routing set do not need to forward information about the link state. The process of establishing the network topology relies on the dissemination of link state information [34, 35, 36, 37]. The BATMAN protocol was developed to overcome the shortcomings of OLSR, specifically in networks with unreliable links. It functions by having each participating node maintain a record of distances to other nodes within the network, with routing decisions made based on the shortest distance. Instead of requiring comprehensive global topology information, each node retains only limited data regarding the optimal next hop to reach other nodes. This eliminates the need for global awareness of local topological changes [38, 39]. BATMAN represents an innovative and distinct approach to routing. Although it constructs routing tables and is considered a proactive routing protocol, it adopts a biologically inspired method similar to AntHocNET. Unlike traditional link state or distance-vector protocols, BATMAN does not aim to explicitly discover or calculate routes. Instead, it focuses on identifying which neighboring node provides the most optimal path to each originator [40, 41]. In BATMAN, routing information is not directly exchanged. Instead, each node broadcasts Originator Messages (OGMs) at regular intervals, typically every second. When neighboring nodes receive these OGMs, they re-broadcast them. The route selection for a specific destination is determined based on the node from which the greatest number of OGMs for that destination has been received. The number of OGMs that can be processed is limited by a dynamically moving window, which restricts the historical data used to describe a route. BATMAN's scalability relies on packet loss; OGMs are transmitted as unreliable UDP packets, similar to other algorithms. Continuous OGM broadcasts would congest the network without packet loss. Consequently, BATMAN's scalability is dependent on packet loss, making it unsuitable for reliable wired networks [42, 43, 44]. Babel, a recent mesh routing protocol defined by IETF RFC 6126, demonstrates performance that is twice as fast as BATMAN and effectively handles traffic through its efficient path selection mechanism. Similar to HWMP, Babel utilizes comparable route cost metrics, yet it does not rely on a fixed routing strategy. It is proactive but also includes reactive features and is implemented on Linux and OpenWrt. Based on the Bellman-Ford algorithm, Babel aims to prevent routing pathologies such as loops and black holes using a feasibility condition and sequence numbers for routing updates.