TFTP Message Formats

Unlike FTP, all communication in TFTP is accomplished in the form of discrete messages that follow a particular message format. The reason why TFTP and FTP are so different in this regard is because of the different transport protocols they use. FTP uses TCP, which allows data to be streamed a byte at a time; FTP also makes use of a dedicated channel for commands. TFTP runs on UDP, which uses a conventional header/data formatting scheme.

The original TFTP standard defines five different types of messages: read request (RRQ), write request (WRQ), data (DATA), acknowledgment (ACK), and error (ERROR). The TFTP option extension feature defines a sixth message: option acknowledgment (OACK). Of these six messages, the first two share ...

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