Communication with Chromecast happens directly over Wifi and does not involve Google services. Chromecast uses the DIAL or mDNS protocol to discover apps on the

Communication with Chromecast happens directly over Wifi and does not involve Google services. Chromecast uses the DIAL or mDNS protocol to discover apps on the local network. Some apps like Netflix can use DIAL protocol to control app on other devices, like Tivo or smart TVs, on the local network. Chromecast does have a new guest mode that allows guests to control Chromecast without connecting to Wifi network. Those commands presumably are relayed through Google servers. But it isn't turned on by default. Chromecast does need to be connected to the Internet to download the receiver app that runs on the Chromecast. If the Chromecast could cache the app, or get it from the controlling app, it could run completely disconnected from the Internet.