NS-3 is well-known for its strong capabilities in handling multiple network interfaces and IP addressing strategies. To enhance the performance of MANET routing protocols, the NS-3 simulation tool is used to analyze these protocols, with a detailed explanation of how to set up an NS-3 simulation platform. From the perspectives of network size and dynamic topology, the end-to-end average delay and delivery rate of AODV, DSDV, and OLSR routing protocols are compared. These simulation results provide a solid foundation for further optimization and improvement of these protocols.
0. Introduction
With the rapid development of network and communication technologies, researchers face challenges in studying large-scale networks without physical hardware, designing new protocols quickly, and comparing old and new systems without expensive real-world setups. In recent years, using software to simulate network protocols, topologies, and performance has become a popular approach. This method reduces costs, increases flexibility, and improves research efficiency. Mainstream network simulation tools include OPNET, QualNet, and NS-2. However, OPNET is commercial and limited in model libraries, focusing mainly on routing. QualNet also has limitations in network layering. NS-2 is complex, with difficult module coordination and expansion. To address these issues, Professor Tom Henderson and his team at the University of Washington developed NS-3, a new open-source network simulator. Compared to other tools, NS-3 offers better multi-NIC processing and IP addressing, a clearer architecture, and the ability to directly migrate code to real network nodes. It is highly customizable for researchers.
1. Analysis of MANET Routing Protocols
Mobile Ad Hoc Networks (MANETs) are self-organized, multi-hop, and infrastructure-free networks widely used in scenarios like disaster relief and military operations. The quality of the routing protocol directly impacts network performance. Three common planar routing protocols in MANETs are DSDV, AODV, and OLSR.
DSDV is a table-driven protocol based on the traditional Distance Vector (DV) algorithm. Each node maintains a routing table for all reachable destinations. It introduces sequence numbers to distinguish between old and new routes, ensuring loop-free updates. Periodic broadcasts are required for route maintenance.
AODV is a source-initiated protocol that combines features of DSR and DSDV. When a node needs to send data, it first checks its routing table. If no route exists, it broadcasts a Route Request (RREQ). Neighbors forward RREQ until a path is found. Once a route is established, periodic Hello packets help maintain connectivity. If a link breaks, the node deletes the faulty route after a delay and sends a Route Error (RERR) packet to update neighboring nodes.
OLSR is an optimized link-state protocol that uses Multi-Point Relay (MPR) nodes to reduce control traffic. Only MPR nodes broadcast Topology Control (TC) messages, allowing other nodes to perceive the network topology. HELLO messages detect neighbors, while TC messages propagate link state information. Nodes then use Dijkstra's algorithm to compute shortest paths.
2. Building the NS-3 Simulation Platform
2.1 NS-3 Simulation Architecture
NS-3 is a discrete-event simulator composed of two main parts: the simulator core and network components. The core includes a time scheduler and a network simulation support system. Unlike NS-2, NS-3 supports both default and real-time schedulers. The simulation support system includes attribute management, logging, and tracing. Network components include nodes, applications, protocol stacks, network devices, channels, and topology builders. These components are abstracted to reflect real-world network behavior with low coupling and high cohesion. By using low-level abstraction, NS-3 ensures accurate simulation of real network performance.
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