darkstat
A packet sniffer that runs as a background process on a cable/DSL router, gathers all sorts of statistics about network usage, and serves them over HTTP.
Features:
* Traffic graphs.
* Traffic reports per host, and per port for each host.
* Embedded web-server with deflate compression.
* Asynchronous reverse DNS resolution using a child process.
* Small. Portable. Single-threaded. Efficient.
V6