Fascinating.
So then how to VPN's work performantly?
I'd always assumed my VPN implemented TCP and UDP over a TCP connection. Do they not? Is the VPN connection actually just UDP?
So then how to VPN's work performantly?
I'd always assumed my VPN implemented TCP and UDP over a TCP connection. Do they not? Is the VPN connection actually just UDP?
See IPSec (most common VPN implementation): https://www.cloudflare.com/learning/network-layer/what-is-ip...
See Wireguard (increasing popularity): https://www.wireguard.com/
TCP is protocol 6, UDP protocol 17; while IPsec uses protocol 50 for ESP (encrypted) and 51 for AH (authenticated).
For pragmatic reasons (firewalls, NAT, that sort of thing) it is nowadays mostly tunneled over UDP.
Modern VPNs will usually attempt UDP first, falling back to TCP only if that does not work; unfortunately, OpenVPN doesn't seem to have that option and requires manual configuration in my experience. This means that many sysadmins configure it to use TCP for the higher success rate in most environments.
IPsec is UDP only, as is Wireguard.
(ignoring IPSec NAT-T)
Also, UDP and ESP can almost be used interchangeably for this discussion (flow control, congestion control, segmentation etc. or a lack thereof).