TCP/IP is the backbone of modern network communication, connecting devices across the world. TCP/IP at its core is a suite of protocols that enables the transmission of data between computers, facilitating the foundation of the interconnected global network. At the Application Layer of TCP/IP is where the interaction between software applications and the network occurs. The user-centric protocols such as HTTP, SMTP, FTP, POP3, IMAP and DNS facilitate various tasks at this layer such as web browsing, email communication, and file transfer. This comprehensive survey conducted an exploration of the performance, security and privacy issues at the application layer of the TCP/IP. It initiated by providing a background of TCP/IP model, it鈥檚 architecture and the core characteristics, with major focus on the application layer. This paper aimed to discuss the state-of-the-art of performance, privacy and security concerns in TCP/IP application layer. It also proposed future research areas to equip researchers, practitioners, policy makers and the decision makers with tangible knowledge, offering guidance in navigating the performance, privacy and security concerns in TCP/IP Application Layer. It aimed to discuss the current performance, privacy and security research gaps at the Application Layer of the TCP/IP Model. The findings of this research sheds light on the performance, privacy and security issues while suggesting the countermeasures to strengthen and optimize the overall performance, security and privacy of TCP/IP model at the application layer. The paper finally suggests future directions and research areas at the TCP/IP application layer.