Is FTP Based on TCP or UDP?

The File Transfer Protocol (FTP), as its name suggests, is a standard network protocol used for the transfer of computer files between a client and server on a computer network. When discussing FTP, a common question that arises is whether it operates on TCP or UDP. To address this query directly, FTP uses the Transmission Control Protocol (TCP) for data transfer, not the User Datagram Protocol (UDP). Before diving into the details of FTP's operation over TCP, let's first understand these two protocols.

Understanding TCP and UDP

TCP and UDP are both protocols used for sending bits of data — known as packets — over the internet. They both build on top of the Internet Protocol (IP), which means they’re both IP-based. However, there are essential differences between the two, primarily regarding reliability, ordering, and speed. TCP, or Transmission Control Protocol, is connection-oriented, ensuring a reliable stream of data between sender and receiver. It establishes a connection before data transmission and ensures that all data packets reach the destination in the correct order. If any packet gets lost during transmission, TCP will retransmit the packet. This makes TCP reliable but comparatively slower due to its overhead. On the other hand, UDP, or User Datagram Protocol, is a connectionless protocol. It doesn't guarantee delivery by avoiding the overhead of checking whether every packet reaches its destination. Thus, UDP is faster and more efficient for lightweight or time-sensitive applications, but it doesn't provide the reliability and ordering of TCP.

FTP and TCP

FTP was designed to facilitate reliable data transfer, which is why it utilizes TCP instead of UDP. Here are some reasons why FTP uses TCP: Reliability: FTP involves the transfer of files, where loss of data packets can lead to corruption of files. TCP’s reliability is essential to ensure that all parts of a file have been correctly received. Ordered data transfer: The ordering of data is another important aspect of file transfer. Packets must be received in the correct sequence to correctly reconstruct the file at the receiving end. TCP provides this feature, while UDP does not. Controlled flow and congestion management: TCP has built-in mechanisms for flow control and congestion management, ensuring that data is not sent at a rate faster than the recipient can handle. This is particularly important for large file transfers to prevent network congestion and loss of packets. Error checking: TCP includes error-checking mechanisms to ensure that the data sent is the same as the data received. This is vital in file transfers where errors can lead to file corruption. FTP operates over TCP in two connections for control and data. The control connection is made for the transmission of commands between the client and the server, while the data connection is for the actual transfer of files. This separation allows for reliable and efficient data transfer. In conclusion, FTP uses TCP because it requires reliable, ordered delivery of data packets that UDP cannot provide. While TCP might have more overhead due to its checks and balances, this ensures that files transferred using FTP arrive intact and error-free, which is critical in many networking and internet tasks.