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Network layer. Routing Protocols Overview
Network layer consisting of several routing protocols is a part of Evologics intelligent Networking Software Framework (EviNS Framework). The framework core is compact and open source, implemented in Erlang language. The framework has relatively moderate system requirements and can be run directly on the EvoLogics acoustic modems' hardware or can be used with the DMACE - a real-time emulator of EvoLogics underwater acoustic modems.
The network we consider is a mobile ad-hoc network, including mobile source and mobile destination nodes. Considering mesh networks be a type of an ad-hoc network, where each node relays data for the network, the delivery of messages from source to destination nodes are based on flooding techniques.
All further explained routing protocols are based on flooding technique. Flood is a communication primitive that can be initiated by the base station of a sensor network to send a copy of some message to every sensor in the network. When a flood of some message is initiated, the message is forwarded by every sensor that receives the message until the sensors decide not to forward the message any more.
There are two types of proposed routing protocols: Relay – deliver a message from source to destination node, rebroadcasting it through the whole network Path find and relay – contains two steps: firstly finding path from source to destination node and than relay message through the network following this path. For the maintenance of the path, the nodes involve a routing table and this path has a time threshold to be expired.
ACK int the name means, that these protocols can be used as protocols with end-to-end acknowledgment.
Uncontrolled Flooding is the fatal law of flooding. All nodes have neighbours and route packets indefinitely. More than two neighbours create a broadcast storm.
Static routing protocol
A message is relayed till the destination node through predefined static routing.
Sequence Number Controlled Flooding
Sequence Number Controlled Flooding (SNCF) is one of controlled flooding algorithms to make flooding reliable. In SNCF, a node attaches its own address and sequence number to the packet, since every node has a memory of addresses and sequence numbers. If it receives a packet in memory, it drops it immediately
Dynamic Probabilistic Flooding
The dynamic probabilistic routing protocol controls the flooding by dynamically determining the rebroadcast probability of a node based on the local knowledge of the neighbors, thus reducing a rebroadcast messages, and therefore, increasing the overall routing reliability by decreasing the routing overhead. The Probabilistic scheme form is similar to Flooding, except that nodes only rebroadcast with a predetermined probability. When the probability is 100%, this scheme is identical to uncontrolled Flooding.
Information Carrying Based Routing Protocol
Initially a source node broadcasts the data packet and the intermediate nodes rebroadcast the received packet. Upon receiving the packet, the destination node sends a reply. The destination node's reply follows the path, recorded during the transmission of the data packet.
Sequence Number Controlled Flooding Path Finder
The path establishment process in this protocol is based on SNCF, a source node broadcasts a request to find the path and the intermediate nodes rebroadcast this packet. Upon receiving the packet, the destination node sends a reply following the first path it got, determining it as a shortest way from source to destination node.
Evologics Information Carrying Routing Protocol
A source node sends a request to find path. The intermediate nodes rebroadcast this packet using information of received signal strength and incoming signal integrity level (these parameters are included in successful reception of message in Evologics DMAC protocol). If it's to low, the node drops this packet. Upon receiving the first path, the destination node waits some time collecting information about other incoming paths. After that the destination node choose the path with the most strength signal and sends reply following this path.
A Low Overhead Routing Protocol for Underwater Acoustic Sensor Networks
LOARP has on-demand nature and consist of two protocol operations: Route Discovery and Route Maintenance. Route discovery process is based on SNCF protocol. The Route Maintenance procedure is based on monitoring the packets coming from the Transport Layer and packets that are forwarded up to the Transport Layer. So that it performs routing maintenance in an intelligent way without incurring extra overhead.