At the most basic level, Rumble is a search engine for your network; it sends out probes, listens for replies, normalizes the results, applies fingerprints, and makes this data easy to query. Similar to web crawlers, Rumble will follow links between assets, this includes HTTP redirects, but also things like SunRPC portmappers, UPnP SSDP endpoints, and other services that point the way to additional data. mDNS (also known as ZeroConf or Bonjour) is one of these services.