CHAPTER2 Ethernet Unit
2-15-2 Description of terminology
■TCP/IP (Transmission Control Protocol/Internet Protocol)
TCP/IP is a general term for a group of standard protocols for carrying out communi- cations over the Internet centering around TCP and IP protocols. Computers and PCs capable of accessing the Internet all use TCP/IP protocols.
The Ethernet unit contains TCP, IP, ICMP, ARP and TELNET protocols.
TCP | IP | |
ARP | ||
TELNET | UDP | |
ICMP | ||
| ||
HTTP | FTP |
TCP/IP protocols
■Ethernet
*The protocols making up TCP/IP are also comprised of many protocols other than those shown in the figure on the left. Protocols are a set of conventions (or rules) that must be mutually complied with so that controllers and PCs can communicate with the other party.
The Ethernet is basically one type of standard for network system hardware. Ethernet is a network invented by the Xerox Corporation (USA) in the early 1970’s and cur- rently forms an international standard known as IEE802.3. The Ethernet physically consists of cable types such as
Another feature of the Ethernet is the use of CSMA/CD as a data transmission method (see below).
■CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
CSMA/CD is a method of sending signals, developed by combining a CSMA data transmission method with a transmission error handling method called CD.
CSMA refers to joint use of one transmission cable by many devices connected over a network. CSMA is therefore a method for checking network status beforehand and then transmitting the data after verifying that transmission is possible.
CD is a method for handling data collisions that occur on the network. In this method, when a data collision (conflict) occurs, that data is
Many devices can be connected to the Ethernet by using these CSMA/CD methods. However, performance cannot be guaranteed in
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