Here is the full context about the auth protocol in the spec: Authentication Protocol Before the flow of messages begins, two applications must authenticate.

Here is the full context about the auth protocol in the spec: Authentication Protocol Before the flow of messages begins, two applications must authenticate. A simple plain-text protocol is used for authentication; this protocol is a SASL profile, and maps fairly directly from the SASL specification. The message encoding is NOT used here, only plain text messages. In examples, "C:" and "S:" indicate lines sent by the client and server respectively. Protocol Overview The protocol is a line-based protocol, where each line ends with \r\n. Each line begins with an all-caps ASCII command name containing only the character range [A-Z_], a space, then any arguments for the command, then the \r\n ending the line. The protocol is case-sensitive. All bytes must be in the ASCII character set. Commands from the client to the server are as follows: