The network sends test packets to suspected VPN servers and blocks whatever answers like one. What to Look For, in Priority OrderNot every feature matters equally on a blocked network. You cannot know whether a VPN beats your specific network until you try it on that network. Most providers with any obfuscation clear it, and a VPN blocked at work or on a school wifi network rarely needs more. If it connects there and fails on the problem network, the network is blocking it.