From the linked pdf in the footnotes, looks like they are rolling their own network protocol:<p>"At launchtime, the VPN protocol will be a Google proprietary protocol; however, to ensure a high throughput while minimizing battery consumption, we will soon adopt IPsec as the data tunnel protocol due to its native support in Android.<p>We may eventually use other protocols, such as Wireguard, as their native support improves or on platforms where no specific protocols have a specific advantage."