What Is an Entity Agreement?

A communication agreement refers to the rules and conventions that both entities must follow to complete a communication or service. A plurality of data communication systems of different geographical locations interconnected through communication channels and devices must have a common language between them to enable them to work together to achieve information exchange and resource sharing. What to communicate, how to communicate, and when to communicate must follow some mutually acceptable rules. This rule is the communication protocol.

letter of agreement

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A communication agreement refers to the rules and conventions that both entities must follow to complete a communication or service. Multiple geographic locations interconnected by communication channels and devices

A communication agreement refers to the rules and conventions that both entities must follow to complete a communication or service. The agreement defines

The communication protocol is mainly composed of the following three elements:

Syntax: how to communicate, including the format, encoding, and signal level of the data (

The communication protocol is hierarchical, reliable and effective. ^[2]

The basic concepts of a layered communication architecture are as follows:

1. The communication function is divided into several levels, each level completes a part of the function, and each level cooperates with each other to complete the communication function.

2. Each layer only deals with two directly adjacent layers. It uses the functions provided by the next layer to provide the higher layer with services that can be completed by this layer.

3. Each layer is independent, the interlayer can be implemented using the most suitable technology, and each layer can be developed and tested independently. When the technological progress of one layer changes, as long as the interface relationship remains unchanged, other layers are not affected.

The hierarchical structure is shown in the figure. Each layer implements relatively independent functions. The lower layer provides services to the upper layer. The upper layer is the users of the lower layer. Each layer cooperates with each other to complete the communication function.

The communication protocols commonly used in the local area network mainly include three protocols: TCP / IP, NETBEUI, and IPX / SPX. Each protocol has its applicable application environment.

TCP/IP Communication protocol 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 achieve interconnection between different networks, the US Department of Defense developed the TCP / IP architecture and protocols between 1977 and 1979. TCP / IP is a combination of a number of sub-protocols with professional uses. These sub-protocols include TCP, IP, UDP, ARP, ICMP, etc. TCP / IP has developed rapidly due to its low implementation cost, secure and reliable communication between multiple platforms, and routableness, 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 used as the default communication protocol.

NetBEUI Communication protocol NetBEUI protocol

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

IPX/SPX Communication protocol IPX / SPX protocol

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