Can network communication be carried out without a protocol?

Can't. The most important thing in network communication is the network communication protocol. In layman's terms, the network protocol is the bridge for communication between networks. Only computers with the same network protocol can communicate and exchange information. Defined from a professional perspective, a network protocol is an agreement that computers must abide by when communicating in a network; it mainly stipulates and develops standards for the rate of information transmission, transmission code, code structure, transmission control steps, error control, etc.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Network communication cannot be done without protocols.

A network uses physical links to connect isolated workstations or hosts to form a data link, thereby achieving the purpose of resource sharing and communication. Communication is the exchange and transmission of information between people through some kind of media.

Network communication is to connect various isolated devices through the network, and realize communication between people, people and computers, and computers and computers through information exchange.

The most important thing in network communication is the network communication protocol. There are many network protocols today, and the three most commonly used network protocols in local area networks are MICROSOFT's NETBEUI, NOVELL's IPX/SPX and TCP/IP protocols. The appropriate network protocol should be selected based on your needs.

• In layman's terms, The network protocol is the bridge for communication and exchange between networks. Only computers with the same network protocol can communicate and exchange information. This is just like the various languages ​​used to communicate between people. Only by using the same language can communication be normal and smooth.

• Defined from a professional perspective, Network protocols are conventions that computers must abide by when communicating on a network, that is, communication protocols. It mainly stipulates and develops standards for the rate of information transmission, transmission code, code structure, transmission control steps, error control, etc.

Commonly used protocols

Different workstations in the network, data can be transmitted between servers, originating from the existence of an agreement. As the Internet evolved, different developers developed different communication methods. For communication to be successful and reliable, all hosts in the network must speak the same language, without dialects. Strict standards must therefore be developed to define every bit in every word in every packet between hosts. These standards come from the efforts of multiple organizations and agree on a common communication method, that is, a protocol. These make communication easier. Many protocols have been developed, but only a few have survived. Those protocols were obsolete for a variety of reasons - poor design, poor implementation, or lack of support. And those protocols that have survived have stood the test of time and become effective communication methods.

NETBEUI

NETBEUI is a non-routing protocol developed for IBM to carry NETBIOS communications. NETBEUI's lack of routing and network layer addressing capabilities is both its greatest strength and its greatest weakness. Because it does not require additional network addresses and network layer headers and tails, it is fast and efficient and is suitable for small workgroup environments where there is only a single network or the entire environment is bridged.

Because routing is not supported, NETBEUI will never become the main protocol for enterprise networks. The address

in the NETBEUI frame is the data link layer media access control (MAC) address, which identifies the network card but does not identify the network. Routers rely on network addresses to forward frames to their final destination, and NETBEUI frames completely lack this information.

Bridges are responsible for forwarding communications between networks based on data link layer addresses, but they have many shortcomings. Because all broadcast traffic must be forwarded to each network, bridges do not scale well. NETBEUI specifically includes accounting for broadcast traffic and relies on it to resolve naming conflicts. Generally speaking, bridged NETBEUI networks rarely exceed 100 hosts. Networks relying on Layer 2 switches are becoming more common. A complete translation environment reduces network utilization, although broadcasts are still forwarded to every host on the network. In fact, the combined use of 100-BASE-T Ethernet allowed the NetBIOS network to be expanded to 350 hosts before broadcast traffic became a serious problem.

IPX/SPX

IPX is the protocol group used by NOVELL for NETWARE client/server, avoiding the weaknesses of NETBEUI. However, new and different weaknesses are introduced. IPX has complete routing capabilities and can be used for large enterprise networks. It includes 32-bit network addresses, allowing many routed networks in a single environment.

The scalability of IPX is limited by its high-level broadcast communication and high overhead. The Service Advertising Protocol (SAP) limits the number of hosts in a routed network to a few thousand. Although the limitations of SAP have been overcome by smart routers and server configurations, administrators of large-scale IPX networks still have a very difficult job.

TCP/IP

Each network protocol has its own advantages, but only TCP/IP allows a complete connection to the Internet. TCP/IP was developed in the 1960s by MIT and some commercial organizations for the U.S. Department of Defense. Even if a nuclear attack destroys most of the network, TCP/IP can still maintain effective communications. ARPANET was developed based on the protocol and developed into the Internet as a communication medium for scientists and engineers.

TCP/IP has both scalability and reliability requirements. Unfortunately, speed and efficiency are sacrificed (but: TCP/IP development was funded by the government).

After the Internet became public, people began to discover the powerful functions of the global network. The ubiquity of the Internet is why TCP/IP is still used. Often without realizing it, users install the TCP/IP stack on their PCs, making this network protocol the most widely used in the world.

TCP/IP’s 32-bit addressing solution is not sufficient to support the number of hosts and networks that are about to join the Internet. A possible replacement for the current implementation is therefore IPv6.

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.

RS-449

RS-449 is a standard published by EIA in 1977, which specifies the mechanical and electrical characteristics between DTE and DCE. RS-449 is a standard developed to replace RS-232-C, but almost all data communication equipment manufacturers still use the original standard, so RS-232-C is still the most popular interface and is widely used. The RS-449 connector uses ISO standard 37-pin and 9-pin connectors. All interconnected circuits except the secondary channel (return word channel) circuit use the 37-pin connector, and the secondary channel The circuit uses a 9-pin connector. The electrical characteristics of RS-449 are specified by RS-422-A for balanced circuits and have roughly the same specifications as V.11, while RS-423-A has generally the same specifications as V.10. V.35 V.35 is a universal terminal interface specification. In fact, V.35 is a modem specification for 48Kbps synchronous data transmission on a 60-108kHz group bandwidth line. Part of it describes the terminal interface specification. V.35 does not specify the mechanical characteristics, that is, the shape of the connector. However, due to the popularity of the American Bell specification modem of 48Dbps-64Kbps, the 34-pin ISO2593 is widely used. The electrical conditions of audio modems for analog transmission use V.28 (unbalanced current loop interconnect circuit), while wideband modems use balanced current loop circuits. X.21 X.21 is a specification for the interface between synchronous terminals (DTE) and line terminals (DCE) in public data networks. Mainly stipulates two functions: one is that, like other interfaces, it stipulates the physical layer of electrical characteristics, connector shape, functional characteristics of interconnected circuits, etc.; the other is the network that controls the network switching function. Control steps define the functions of the network layer. In a dedicated line connection, only the physical layer function is used, while in a line-switched data network, both physical layer and network layer functions are used. The connector pins used for the X.21 interface only use 15 pins. The electrical characteristics refer to V.10 and V.11 of the V series interface electrical conditions respectively. The synchronization of the digital network is slave synchronization that is subordinate to the network master clock.

HDLC (Advanced Data Link Control Protocol)

HDLC is a control protocol with high reliability and high-speed transmission. Its characteristics are as follows: it can transmit any combination of bits; it can continuously transmit data without waiting for a response from the receiving end; it has strict error control; it is suitable for communication between computers. HDLC is equivalent to a standard method of the data link layer part of the OSI basic reference model. HDLC has a wide range of applications, and most of the data link layers of modern protocols are based on HDLC.

SDLC (Synchronous Data Link Control)

is a protocol developed by IBM and becomes the data link control layer protocol of SNA. In fact, it is also included in HDLC.

FDDI (Fiber Distributed Data Interface)

The transmission speed of FDDI is 100Mbps, the transmission media is optical fiber, and it is a token-controlled LAN. The physical transmission clock speed of FDDI is 125MHz, but the actual speed is only 100Mbps. The maximum number of workstations that can actually be connected is 500, but it is recommended to use less than 100. There are basically two types of FDDI connection forms: one is a ring structure composed of two rings, a primary loop and a secondary loop; the other is a tree structure with the hub as the center. The distance between workstations is 2KM using optical fiber and 100M using twisted pair. However, for single-mode optical fiber, standards have been established that the distance between nodes can be extended to more than 2KM. FDDI has three interfaces: DAS (dual accessory station); SAS (single accessory station); hub (Concentrater). Usually only the primary loop is used, and the secondary loop is in standby mode as a backup system.

SNMP (Simple Network Management Protocol)

A network management protocol in the TCP/IP protocol set. has been widely adopted. Using the SNMP management model, the protocol for managing INTERNET works at the application layer of TCP/IP. The advantage is that the protocol can be specified without relying on the properties of the network physical layer. A common protocol can be used for all networks and management. A client/server approach can be used between the manager and the managed, which can be called an agent (tool). ); if the manager works as a client, it can be called a manager or management station. The functions of the agent should include the management of the operating system and network management layer, obtain the seven-layer information about the object, and use the SNMP network management protocol to notify the administrator of the information. The manager itself should request that information about the objects be stored in the virtual database of the MIB (Management Information Base) contained in the agent. For SNMP, it is required to be able to obtain or set objects from management to the agent network management object itself. The agent should complete the response requested by the manager. At the same time, the agent itself should also notify the manager of events that occur due to the agent. 10. Point-to-point protocol PPP (point to point protocol) PPP, formulated as RFC1171/1172, is an Internet standard protocol for relaying LAN protocols including IP on point-to-point lines. PPP has been compatible with multiple protocols since its creation and is designed to have a data link that does not depend on network layer protocols. When PPP is used to relay various network layer protocols, each network layer protocol must have certain specifications corresponding to PPP, and some of these specifications already exist. The actual installation of PPP has begun, especially router manufacturers that must adapt to multi-protocols are actively adopting PPP. PPP is composed of two protocols: one is LCP (Data Link Control Protocol) used to ensure a data link that is independent of the protocol; the other is used to implement the network layer protocol control function in the PPP environment. NCP (Network Control Protocol). For its purpose, NCP needs to be specified in each network layer protocol. The specific name of NCP differs in the corresponding network layer protocol. To be more precise, the protocol specified by PPP is only LCP. As for how to put NCP and network layer protocols into PPP frames, it is up to the manufacturers who develop various network layer protocols. PPP frames have the function of transmitting LCP, NCP and network layer protocols. There are no special restrictions on the physical layer specifications utilizing LCP. Common physical connectors such as RS-232-C, RS-422/423, and V.35 can be used. There are no special regulations on the application field of transmission speed. You can use the transmission speed allowed by the physical layer specifications. Instead, use a full-duplex communication line.

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