What are the communication protocols?

Communication agreement refers to the rules and agreements that entities on both sides must follow to complete communications or services. Multiple data communication systems in different geographical locations are interconnected through communication channels and equipment. In order for them to work together to achieve information exchange and resource sharing, they must have a common language. What, how and when to communicate must all follow some mutually acceptable rules. This rule is the communication protocol.

Commonly used communication protocols in LAN mainly include TCP/IP, NETBEUI and IPX/SPX. Each protocol has its applicable application environment.

TCP/IP

The history of TCP/IP (Transport Control Protocol/Internet Protocol, Transmission Control Protocol/Internet Protocol) should be traced back to the predecessor of the Internet - the ARPAnet era . In order to realize the interconnection between different networks, the U.S. Department of Defense developed the TCP/IP architecture and protocols from 1977 to 1979. TCP/IP is composed of a set of multiple sub-protocols with professional purposes, including TCP, IP, UDP, ARP, ICMP, etc. TCP/IP has developed rapidly due to its advantages such as low implementation cost, secure and reliable communication between multiple platforms, and routability, and has become a standard protocol in the Internet. In the 1990s, TCP/IP has become the preferred protocol in local area networks. In the latest operating systems (such as Windows 7, Windows XP, Windows Server 2003, etc.), TCP/IP has been installed as the default communication protocol.

NetBEUI protocol

NetBEUI (NetBIOS Enhanced User Interface) protocol is developed and improved from NetBIOS (Network Basic Input and Output System). This protocol only requires simple configuration It consumes less network resources and can provide very good error correction functions. It is a fast and effective protocol. However, due to its limited network node support (up to 254 nodes) and non-routing nature, it is only suitable for small LANs based on Windows operating systems.

IPX/SPX protocol

IPX/SPX (Internet Packet Exchange/Sequence Packet Exchange) protocol is mainly used in Novell LAN based on NetWare operating system, based on other operations The system's LAN (such as Windows Server 2003) can communicate with the Novell network through the IPX/SPX protocol. In Windows 2000/XP/2003 systems, the IPX/SPX protocol and NetBEUI protocol are collectively called NWLink.

RS-232-C

RS-232-C is the specification of the physical layer part of the OSI basic reference model. It determines the physical characteristics such as connector shape, and 0 and 1 represents the electrical characteristics and the logical characteristics that represent the signal meaning.

RS-232-C is published by EIA and is a modified version of RS-232-B. It was originally standardized for connecting DCEs such as modems and DTE pull interfaces such as teleprinters in analog communication lines. Many personal computers also use RS-232-C as the input and output interface, and personal computers using RS-232-C as the interface are also very popular.

RS-232-C has the following features: straight-through mode, two-way communication, basic frequency band, current loop mode, serial transmission mode, signal form used between DCE-DTE, handover mode, full-duplex communication . RS-232-C is functionally interchangeable in the 25-pin connector specified by ITU recommendations V.24 and V.28.

The connector used by RS-232-C is a 25-pin plug-in connector, generally called a 25-pin D-SUB. The top of the cable on the DTE end is connected to a male plug, and the DCE end is connected to a female socket.

The shape of the cable used for RS-232-C is not fixed, but mostly shielded 24-core cables are used. The maximum length of the cable is 15m. Data transmission is possible using RS-232-C at any rate up to 200K bits/second.

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