What is the three-tier architecture of enterprise LAN?

Three-layer architecture of enterprise LAN: core layer (core router, three-layer switch) convergence layer (three-layer switch) access layer (layer 2 switches connected to PC). Three-tier architecture In general, the three-tier architecture is to divide the whole business application into: presentation layer, business logic layer and data access layer. The purpose of distinguishing levels is for the idea of "high cohesion and low coupling".

1. Presentation layer: Generally speaking, it is the interface presented to the user, that is, what the user sees and gains when using a system.

2. business logic layer: the operation aimed at specific problems can also be said to be the operation of data layer and the logical processing of data business.

3. data access layer: the transactions done by this layer directly operate the database, aiming at data addition, deletion, modification and query.

in software architecture design, hierarchical structure is the most common and important structure. The hierarchical structure recommended by Microsoft is generally divided into three layers, from bottom to top: data access layer, business logic layer (or domain layer) and presentation layer.

Three-tier structure principle: among the three tiers, the main functions and business logic of the system are handled in the business logic tier. The so-called three-tier architecture adds a "middle tier" between the client and the database, which is also called the component layer. The three-tier system mentioned here does not refer to the physical three-tier, or simply putting three machines or a three-tier architecture, and it is not only the b/s application that is the three-tier architecture, but the three-tier refers to the logical three-tier, even if these three layers are placed on one machine. The three-tier application puts business rules, data access, legitimacy verification and other work in the middle layer for processing. Usually, the client does not directly interact with the database, but establishes a connection with the middle layer through com/dcom communication, and then interacts with the database through the middle layer.

Extended information: Core layer

Core layer: The function of the core layer is mainly to realize the optimal transmission between backbone networks, and the design tasks of the backbone layer usually focus on redundancy, reliability and high-speed transmission. It is best to implement the control function of the network on the backbone layer as little as possible. The core layer has always been regarded as the ultimate receiver and aggregator of all traffic, so the requirements for the design of the core layer and network equipment are very strict. Core layer equipment will account for the main part of the investment. The core layer needs to consider redundancy design.