Transmission Control Protocol/ Internet Protocol (TCP/IP) is the backbone of Internet transmission. The Transport Layer of the TCP/IP stack, which includes TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) protocols, plays a crucial role in ensuring reliable communication between devices over a network. To come up with measures that make networks more secure, it is important to learn about the vulnerabilities that exist in the transport TCP/IP stack and then have an understanding of the typical attacks carried out in such layer. This paper explores how the TCP Protocol works, the TCP/IP 3 Way Handshake, TCP Header Structure, the typical vulnerabilities and the classical attacks of transport layer TCP/IP, tools, and solutions adopted to prevent and reduce the chances of some of these attacks. The findings indicated that the major TCP/ IP stack transport layer threats include Finger printing, SYN Flood, TCP reassembly and sequencing, IP Spoofing, TCP session hijacking, RST and FIN denial of service attack, Ping of Death, Low Rate/ Shrew Attacks. Their preventive measures and mechanisms are discussed.