Definition: communications protocol

The formats, codes and procedures that govern data transmission between computers and mobile devices. A protocol defines the packet structure of the data and the network commands. A "protocol suite" comprises several layers, and learning each layer is essential to understanding this subject (see OSI model).

TCP/IP
TCP/IP is the standard routing protocol of the Internet and most internal networks. It ensures that every message sent was received in full (see TCP/IP). Ethernet is the physical access method that moves packets from one node to another in a local network (see Ethernet). The Internet uses several access methods (see ATM and SONET).

Conceptually Speaking TCP/IP
The following is a conceptual TCP/IP exchange:

Are you there? Yes, I am. Are you ready to receive? Yes, I am. Here comes the message--blah, blah, blah-- did you get it? Yes, I did. Here comes the next part--blah, blah, blah-- did you get it? No, I didn't - resend it. Here it comes again-- blah, blah, blah-- did you get it? Yes, I did. There is no more. Goodbye. Goodbye.

Examples
The following communications protocols are or have been widely used:

    Layer    Protocol

     1       RS-232
     1       V.35
     1       SONET

     1-2     Wi-Fi wireless
     1-2     Bluetooth wireless

     2       Ethernet
     2       Fast Ethernet
     2       Gigabit Ethernet
     2       Token Ring
     2       FDDI
     2       ATM

     3       IP      (TCP/IP)
     3       IPX     (NetWare)

     4       TCP     (TCP/IP)
     4       UDP     (TCP/IP)
     4       SPX     (NetWare)
     4       NetBEUI (NetBIOS)

     5       NetBIOS

     6       ASN.1

     7       SMB     (NetBEUI)
     7       AFP     (AppleTalk)
     7       NCP     (NetWare)
     7       NFS     (TCP/IP)
     7       HTTP    (TCP/IP)
     7       FTP     (TCP/IP)
     7       SMTP    (TCP/IP)
     7       DNS     (TCP/IP)