| 单词 | protocol |
| 释义 | protocol From the Greek protokollon, for a leaf of paper glued to a manuscript volume and describing its contents. The rules and conventions for exchanging information between computers or across computer networks. Protocols comprise conventions that, at a basic level, commonly include the dimensions of line setup, transmission mode, code set, and non-data exchanges of information such as error control. Protocols have two major functions: handshaking and line discipline. • Handshaking: The sequence that occurs between the devices over the circuit, establishing the fact that the circuit is available and operational. The handshaking process also establishes the level of device compatibility, and determines the speed of transmission by mutual agreement. • Line discipline: The sequence of network operations that actually transmits and receives the data, controls errors in transmission, deals with the sequencing of message sets (e.g., packets, blocks, frames, and cells), and provides for confirmation or validation of data received. As there exists a wide range of protocols that address various aspects of the communications between devices, protocols often are organized into protocol suites, such as the TCP/IP protocol suite, or layered architectures, such as the OSI Reference Model. In such a tiered approach, the lowest layer addresses physical issues of connectivity and signal format, and the highest layer in the most complete suite addresses applications issues dealing with the user interface. See also handshaking, Hellenologophobia, line discipline, OSI Reference Model, and TCP/IP protocol suite. 74570c16.qxd 9/11/07 12:27 PM Page 393 |
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