The relationship between network level protocol and Structure system

The communication between LAN and Internet is done with the support of different network hierarchy architecture and Network Level protocol. So what are their definitions and roles in this? How do we position agreements, structures, systems, and hierarchies? Let's say a few questions in detail below.

1. Several basic concepts in the hierarchical architecture

(1) Agreement

Protocol (PROTOCOL) is a communication specification. For example, in the postal communication system, the format of writing letters, the standard and writing format of envelopes, the packing of letters and the conventions of parcel cover are all communication protocols of the postal communication system. Therefore, in the process of computer network communication, in order to ensure accurate data communication between computers, a set of communication rules must be developed, which is the communication protocol.

(2) level

Stratification (Layer) is the basic method for people to deal with complex problems. When people encounter a complex problem, it is customary to break it down into several small problems and deal with them. For example, for postal communications systems, such a complex problem involving the transmission of letters between hundreds of millions of people across the country and all regions of the world, the solution is to allocate many of the functions to be implemented at different levels; The process of realizing the services and services to be completed at each level is clearly defined; systems in different regions are grouped into the same level , the same level of the same function of different systems, high-level use of services provided by the lower level, do not need to know the specific implementation of low-level services.

There are many similarities between the hierarchical architecture used in postal communication system and the architecture of computer network, whose essence is the "divide and conquer" structured approach to complex problems. The hierarchical processing method can greatly reduce the difficulty of the problem, which is the direct power of hierarchical structure in network research. Therefore, the hierarchy is another important and basic concept in the computer network architecture.

(3) interface

An interface (Interface) is a connection point in which information is exchanged between adjacent layers within the same node. For example, in a postal communication system, a mailbox is a specified interface between the sender and the postman. There is a well-defined interface between the adjacent layers of the same node, and the lower layer provides services to the high-level through the interface. As long as the interface condition is unchanged and the low-level function is unchanged, the change of the implementation method and technology of low-level function will not affect the work of the whole system. Therefore, the interface is also an important and basic concept in the computer network implementation technology.

2. Network Architecture

Network protocol is indispensable to computer network, and a complete set of complex protocols is needed for a fully functional computer network. The best way to organize a complex network protocol is to have a hierarchical structure model. To this end, the network hierarchy structure model and the collection of network hierarchy protocols are defined as the computer network Architecture (network architecture). Network architecture is a precise definition of the functions that should be implemented in computer networks, and what kind of hardware and software are used to accomplish these functions is a specific implementation problem. Architecture is abstract, and implementation is concrete, it refers to some of the hardware and software that can be run.

3. The research significance of network architecture

In 1974, IBM proposed the world's first network architecture SNA (System Network architecture), which can be easily interconnected by devices that follow the SNA architecture. As a consequent, companies have launched their own network architecture, such as the digital company's DNA. The common feature of these network architectures is that the "level" technology is adopted, and the Division, function and technical terms used in each level are different. Therefore, the computer network uses the hierarchy structure, it has the following some benefits:

Each layer is independent of each other. The high level does not need to know how the low-level is implemented, but only the services that the layer provides through the interface between the layers.

Good flexibility. When any layer changes, for example, as a result of technological advances to facilitate the implementation of technology changes, as long as the interface remains unchanged, the layers above or below this layer are unaffected. In addition, this layer can even be canceled when the service provided by a layer is no longer needed. Because each layer is independent, so each layer can choose the most appropriate implementation technology, the implementation of technology changes at all levels will not affect other layers. Easy to implement and maintain. As the entire system is segmented into a number of easily implemented and maintained small portions, the entire large and complex system becomes easy to implement, manage, and maintain.

Beneficial to the implementation of standardization. Because each layer has a clear definition, that is, each layer to achieve the function and the services provided are clear, so it is very conducive to the implementation of standardization.

With the development of information technology, the interconnection of various computer systems and Internet has become an urgent problem to be solved. The OSI reference model and the network hierarchy protocol are proposed and researched in this context.