A Discrete-Event Network Simulator

Nix-Vector Routing Documentation

Nix-vector routing is a simulation specific routing protocol and is intended for large network topologies. The on-demand nature of this protocol as well as the low-memory footprint of the nix-vector provides improved performance in terms of memory usage and simulation run time when dealing with a large number of nodes.

Model Description

The source code for the NixVectorRouting module lives in the directory src/nix-vector-routing.

ns-3 nix-vector-routing performs on-demand route computation using a breadth-first search and an efficient route-storage data structure known as a nix-vector.

When a packet is generated at a node for transmission, the route is calculated, and the nix-vector is built. The nix-vector stores an index for each hop along the path, which corresponds to the neighbor-index. This index is used to determine which net-device and gateway should be used. To route a packet, the nix-vector must be transmitted with the packet. At each hop, the current node extracts the appropriate neighbor-index from the nix-vector and transmits the packet through the corresponding net-device. This continues until the packet reaches the destination.

Scope and Limitations

Currently, the ns-3 model of nix-vector routing supports IPv4 p2p links as well as CSMA links. It does not (yet) provide support for efficient adaptation to link failures. It simply flushes all nix-vector routing caches. Finally, IPv6 is not supported.


The usage pattern is the one of all the Internet routing protocols. Since NixVectorRouting is not installed by default in the Internet stack, it is necessary to set it in the Internet Stack helper by using InternetStackHelper::SetRoutingHelper


The examples for the NixVectorRouting module lives in the directory src/nix-vector-routing/examples.

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