Protocol is a set of rules that is necessary for communicating between the sender and the receiver. Every network protocol has a different job. Such as FTP is a file transfer protocol. With the help of which user can upload the file to the server.
It refers to structure or format of the data. It means how data will made. Syntax indicates how the network structure will be and how it will work.
It refers to meaning of each section of the bits. It means each section of bits has a unique label which is understanding by user.
It refers to the time which determines that when and how fast data should be send. In other words, how much time will be spend to send data.