Use TcpRuleRecvProto rules to describe length-based protocols. Length-based protocols are protocols in which the number of bytes to be received from the server can be extracted from a fixed location in a protocol header. This rule type is specified by XML nodes with the name TcpRuleRecvProto.
Use TcpRuleRecvUntil rules to describe protocols in which the end of a server response can be detected by a terminating sequence of bytes. This rule type is specified by XML nodes with the name TcpRuleRecvUntil.