Summary of several important network communication protocols (1)

We all know that computer networks are divided into seven layers, each of which has its own network communication protocol. We can easily understand the concept of network communication protocol. However, it contains many protocols. Here we will summarize several important protocols to help you make a summary. See the text below.

Network Communication Protocol 1:

◆ RS-232-CRS-232-C

It is the specification of the OSI basic reference model physical layer. It determines the physical characteristics such as the connector shape, electrical characteristics expressed in 0 and 1, and logical characteristics that represent the meaning of the signal. RS-232-C is EIA published, is a modified version of the RS-232-B. It was originally standardized to connect DCE and DTE pull interfaces such as modem in analog communication lines and telex printers. Now many PCS also use RS-232-C as the input and output interface, RS-232-C as the interface of the PC is also very popular. The following characteristics of the RS-232-C: using direct mode, two-way communication, basic band, current ring mode, serial transmission mode, the signal form used between the DCE-DTE, the transfer mode, full duplex communication. The RS-232-C is functionally interchangeable on the 25-pin connector specified by the V.24 and V.28 recommended by the ITU. The connector used by the RS-232-C is a 25-pin plug-in connector, generally known as a 25-pin D-SUB. The DTE end is connected to the public plug at the top of the cable, and the DCE end is connected to the parent socket. The shape of the cable used by the RS-232-C is not fixed, but most use a shielded 24-core cable. The maximum cable length is 15 m. Data can be transferred at any rate below K bit/s using a RS-232-C.

Network Communication Protocol 2:

◆ RS-449

RS-449 is a standard published by EIA in 1977, which specifies the mechanical and electrical properties between DTE and DCE. RS-449 is to replace RS-232-C and the development of standards, but almost all the data communication equipment manufacturers still use the original standards, so RS-232-C is still the most popular interface and is widely used. RS-449 connectors use ISO 37-pin and 9-pin connectors, 2-channel return-word channels) All other interconnected circuits use 37-pin connectors, the channel circuit uses a 9-pin connector. The electrical characteristics of the RS-449, for the balanced circuit by the RS-422-A, generally with V.11 has the same specification, while the RS-423-A has the same specification and V.10.