Why does a video call skip instead of waiting for lost data?

A video call skips because it is better to lose a moment than to freeze while waiting for it. The internet offers two ways to send data between programs. TCP provides reliable, ordered, error-checked delivery, so the web, email and file transfers rely on it. UDP is a connectionless datagram service that prioritises time over reliability. Time-sensitive applications often use UDP because dropping packets is preferable to waiting for packets delayed by retransmission.

Here is the trade-off. TCP is connection-oriented: sender and receiver first agree on parameters in a three-way handshake. That handshake, plus retransmission and error detection, adds to reliability but lengthens latency. UDP skips all of it. Messages are sent without negotiating a connection, and UDP does not keep track of what it has sent. There is no guarantee of delivery, ordering or duplicate protection.

For a web page, a missing byte would ruin the page, so waiting is right. For a voice or video call, a packet that arrives a second late is useless, because the conversation has moved on. That is why UDP suits voice calls and online games, and also tiny question-and-answer exchanges such as looking up a Domain Name System address.

Both protocols use ports to hand data to the right program. A port is a communication endpoint that identifies a specific process or network service on a machine, a number from 0 to 65535, so your browser, your game and your chat app can all share one address without mixing up their data.