TCP

What if a simple packet(s) could bring down the internet? In the world of TCP/IP, vulnerabilities like SYN flood attacks have threatened network stability for decades. This deep dive explores the ingenious mitigation known as TCP SYN cookies, from the basics of TCP state management to its pragmatic trade-offs and lessons for modern engineering. Transmission Control Block The Transmission Control Block (TCB) is a critical data structure created when a TCP entity opens a TCP connection. A TCB contains the whole state of the connection and must maintain all information required to send and receive segments. ...

In today’s fast paced digital word, miliseconds count. The traditional way that TCP connections are established, known as the three-way handshake (3WHS), introduces a significant latency cost: at least one full Round-Trip Time (RTT) before any actual data can be exchanged. For applications like web browsing, where many connections are short-lived or frequently re-established, this delay can severely impact user experience. This is where TCP Fast Open (TFO) comes in. Documented in RFC 7413, TFO is an experimental TCP mechanism designed to save up to one full RTT by allowing data to be carried in the initial SYN and SYN-ACK packets of a TCP connection, enabling the receiving end to consume it during the handshake itself. ...