The difference between TCP and UDP

At the transport layer of TCP/IP model there are 2 protocols, so called TCP and UDP.

So, what’s the difference between TCP and UDP?

Let’s see the difference and features each other.

Table of contents

Reliability

The biggest difference between TCP and UDP is the reliability.

In the case of UDP, when it send packet it don’t secure connections.

Even if packets are lost, UDP don’t resend the packet.

However in the case of TCP, it secure connections before sending the packet.

TCP secure connections by 3 way handshake.

①Before sending the packet, sender set the ACK flag of TCP header control flags to 1 and send it to receiver.

from:https://www.lifewire.com/tcp-headers-and-udp-headers-explained-817970

②Receiver set the SYN flag to 1 with remaining ACK flag to 1, and resend it to sender.

③Finally sender send the TCP header with setting SYN flag to 0 and ACK flag to 1.

When these 3 steps have completed, the connection between sender and receiver have established and data can be exchanged.