This provides nice summary of protocols, it would be a switch between (Regular VPN vs Stronger VPN).
TCP vs UDP
Long story short: TCP is heavier and slower than UDP. UDP is a preferred choice for speed, TCP is preferred when Internet connection is unstable.
TCP provides highly reliable, ordered, and checked for error delivery of information between applications. TCP is a connection based protocol which means that TCP first establishes a connection between two devices and only then sends data. Additionally, TCP performs flow control, error detection and correction to ensure that all packets are delivered. All data transferred via TCP is guaranteed to be delivered in the same order it was sent. TCP is heavier, its header size is 20 bytes while UDP is only 8 bytes. All of the above causes network overhead and makes TCP much slower. TCP is an excellent choice on unreliable networks, however, since TCP will check for lost packets and automatically resend them.
UDP is a more efficient protocol since it doesn’t establish a direct channel between two devices, it provides a connectionless datagram service that emphasizes reduced latency over reliability. UDP only sends information, but does not care if it ever reaches the intended destination or gets lost in the process, avoiding the overhead of error processing at the network interface level. Since UDP does not take time to establish connection, never checks for errors and does not track the packets, time-sensitive applications (gaming, streaming, VoIP) often use UDP because dropping packets is preferable to waiting for delayed packets. Sounds bad, right? Not really since the packets are virtually never lost in real life unless the Internet connection is unreliable.
Here is some info about ports:
Common applications/processes often use specifically reserved port numbers for receiving service requests from clients:
HTTPS (TLS/SSL) – 443 TCP/UDP // HTTP – 80 UDP/TCP // OpenVPN – 1194 TCP/UDP // PPTP – 1723 TCP/UDP // L2TP – 1701 UDP // SSTP – 443 TCP // Cisco IPsec – 1293 TCP/UDP, 500 TCP/UDP // IKEv2 (Internet Key Exchange) – 500 TCP/UDP
Since default configurations for specific processes are well known, network admins can easily block certain ports to restrict a particular traffic. For instance, when 1194 port is blocked, OpenVPN doesn’t work unless VPN software can forward OpenVPN traffic via a port that is open.
So in order to bypass restrictive firewalls that block ports (college and corporate networks, for instance), VPN providers offer port forwarding typically to 443, 80, 53, 22 ports:
PORT FORWARDING TO PORT 443
Forwarding VPN traffic to port 443 is the best way to bypass firewall restrictions since port 443 is used for encrypted TLS/SSL traffic by default. In other words, web browsers establish secure HTTPS connections using port 443. So as long as access to https:// websites is not restricted, port 443 is open. Additionally, since port 443 is used for encrypted communication, VPN traffic sent over 443 will sort of “blend in” with the rest (deep packet inspection can still detect it, of course).