Definition
Transmission Control Protocol (TCP) is a core internet protocol that provides reliable, ordered, and error-checked delivery of data between applications running on hosts communicating over an IP network. It establishes a connection before data transmission, ensuring that packets arrive in the correct sequence and are retransmitted if lost or corrupted. This reliability makes TCP essential for applications where data integrity is paramount, such as web browsing, email, and file transfers. For instance, when you download a file, TCP ensures all parts of the file arrive completely and in the right order. Unlike UDP, which prioritizes speed over reliability, TCP adds overhead to guarantee delivery. TCP is a fundamental concept tested on exams like CompTIA Security+, Network+, and CISSP.