VPN over DNS
The Android app SlowDNS presents a VPN carried over DNS, an inventive option for networks that allow DNS but restrict other traffic.
The diagram makes the basic tradeoff visible: DNS can cross places where other traffic is filtered, but it imposes tight throughput and packet-size limits.
It is a historic and technical exhibit, not a recommendation for bypassing network policy.
Primary source: https://play.google.com/store/apps/details?id=com.in.troiddns