communications protocol

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Related to communications protocol: bandwidth, TCP

communications protocol

Hardware and software that governs data transmission between computers and mobile devices. The term "protocol" is very generic and is used for hundreds of different communications methods. A protocol may define the packet structure of the data transmitted or the control commands that manage the session, or both. A protocol "suite" such as TCP/IP is made up of several levels of functionality. Learning the 7-layer protocol hierarchy, known as the "OSI model," is essential for understanding protocols. See OSI model and interface.

TCP/IP and Ethernet
TCP/IP is the standard routing protocol of the Internet and most internal networks. It ensures that every message sent was received in full. Ethernet is an access method that is responsible for moving packets from one node to another. See TCP/IP, Ethernet, Token Ring, ATM, IPX, SPX, NetBIOS, NetBEUI and SS7.

Conceptually Speaking

The following are very conceptual exchanges managed by TCP/IP and Ethernet.

TCP/IP Protocol
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.

Ethernet Access Method (Shared Hub Example)
Is the network busy? Yes, it is. Wait random amount of time. Is the network busy? Yes, it is. Wait random amount. Is the network busy? No, it isn't. Here goes the frame... did it collide with another packet on the line? No, it didn't. Is the network busy? Yes, it is. Wait random amount. Is the network busy? No, it isn't. Here goes the next frame... did it collide? Yes, it did. Wait random amount. Is the network busy? No, it isn't. Here goes the frame again... did it collide?


The following communications protocols are or have been widely used (name in parentheses is the protocol suite). There are a large number of protocols at all layers. For a comprehensive list with detailed descriptions, visit

Layer Protocol

     1       RS-232
     1       V.35
     1       SONET

     1-2     802.11 wireless (Wi-Fi)
     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)
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