With the continuous development of network technology, standalone software programs can no longer meet the demands of networked computers. As a result, various network program development architectures have emerged. Among them, the most commonly used network application development architectures can be divided into two types: the Client/Server (C/S) structure and the Browser/Server (B/S) structure. Below, we will introduce these two structures.
Introduction to C/S Architecture
C/S stands for Client/Server. In this structure, the server typically uses high-performance PCs or workstations and employs large database systems (such as Oracle or SQL Server), while the client needs to install dedicated client software. This structure can fully utilize the advantages of both ends of the hardware, reasonably distributing tasks between the client and the server, thereby reducing the communication overhead of the system. Before the year 2000, the C/S structure dominated the field of network program development. The C/S structure was first developed by Borland in the United States.
Introduction to B/S Architecture
With the advent of the Web 2.0 era, the internet architecture has shifted from the traditional C/S architecture to the more convenient and faster B/S architecture. The B/S architecture greatly simplifies the difficulty of using network applications, allowing everyone to access the internet and use the services provided online, further promoting the prosperity of the internet.
The B/S architecture brings the following two benefits:
● The client uses a unified browser. Due to the uniformity of browsers, they do not require special configurations or network connections, effectively shielding users from the differences in services provided by different service providers. Moreover, the most important point is that the interactive features of browsers make them very easy for users to use, and the inheritability of user behavior is very strong. This means that once users learn how to browse the internet, regardless of which application they use, they can apply their experience to other internet services since they all operate on the same browser interface.
● The server is based on a unified HTTP protocol. Unlike the traditional C/S architecture that uses custom application layer protocols, the B/S architecture uses a unified HTTP protocol. The use of a unified HTTP simplifies the development model for service providers, allowing server developers to adopt a relatively standardized development approach, which can significantly reduce development costs. Because of the unified HTTP protocol, there are many servers based on HTTP, such as Apache, IIS, Nginx, Tomcat, and JBoss, which can be used directly without requiring service developers to create them separately. Furthermore, even the common frameworks for developing services do not need to be developed separately; service developers only need to focus on the application logic of providing services, while all other platforms and frameworks can be used directly. Thus, the B/S architecture also simplifies the development for service providers, leading to an increasing number of internet services.
The B/S network architecture simplifies both the front-end and back-end, relying on the unified application layer protocol HTTP for data interaction. Unlike most traditional C/S internet applications that use long connection interaction modes, HTTP employs a stateless short connection communication method. Typically, a single request completes a data exchange, usually corresponding to a business logic, after which the communication connection is terminated. This approach is designed to serve more users simultaneously, as current internet applications handle millions of user requests daily, making it impossible to maintain a connection for each user after a single access.
Based on the characteristics of the HTTP protocol itself, most current B/S network architectures adopt the architectural design shown in Figure 1.1, which aims to meet the access requests of massive users while maintaining quick response times. Therefore, modern network architectures are becoming increasingly complex.
Figure 1: CDN Architecture Diagram
When a user enters the URL java.itxdl.cn in their browser, many operations occur. First, it requests DNS to resolve this domain name into the corresponding IP address, then finds the corresponding server on the internet based on this IP address and initiates a GET request to that server, which decides to return the default data resources to the accessing user. On the server side, there is actually a complex business logic: there may be many servers, and determining which server to handle the request requires a load balancing device to average all user requests; the requested data may be stored in distributed caches, static files, or databases; when the data is returned to the browser, if the browser parses the data and finds additional static resources (such as CSS, JS, or image resources), it will initiate another HTTP request, which may be handled by a CDN. Thus, a user may be involved in many operations. Every detail can affect whether this request will ultimately succeed.
No matter how the network architecture changes, there are always some fixed principles that must be followed.
● All resources on the internet must be represented by a URL, which is a Uniform Resource Locator. If you want to publish a service or resource on the internet for others to access, you must first have a unique URL. Do not underestimate this URL; it encapsulates the essence of the entire internet architecture.
● Interaction with the server must be based on the HTTP protocol. Whether you are accessing domestic or foreign data, text data or streaming media, you must follow the established protocols, meaning you must use a standardized greeting method so that the server understands what is required.
● Data presentation must occur in the browser. Once the data resources are obtained, they must be displayed in the browser to restore their appearance.
Comparison of the Two Architectures
The C/S structure and B/S structure are the two main mainstream network program development architectures in today’s world. Currently, both structures have their own market share and customer base. However, these two architectures each have their own advantages and disadvantages, which will be compared and explained from three aspects.
1. Development and Maintenance Costs
The development and maintenance costs of the C/S structure are higher than those of the B/S structure. When using the C/S structure, different programs must be developed for different clients, and software installation, debugging, and upgrades must be performed on all client machines. For example, if a company has 10 client sites using a C/S structured software, all 10 client sites need to install the client program. When even a minor change is made to the software, the system maintainer must uninstall the existing client software and install the new version, which can lead to version inconsistencies if clients do not update in a timely manner, resulting in operational failures. In contrast, B/S structured software does not require installation or maintenance on the client side. If the software used in the aforementioned company is switched from C/S to B/S structure, after upgrading the server software to the latest version, other clients only need to log back into the system to use the latest version of the software.
2. Client Load
The C/S structure’s client is responsible not only for user interaction and collecting user information but also for processing requests to the server for databases, spreadsheets, or documents over the network. Thus, the more complex the application, the larger the client program, which complicates software maintenance. In contrast, the B/S structure delegates the transaction processing logic to the server, allowing the server to handle it while the client only needs to display the information. This increases the operational data load on the application server, and if a server “crash” occurs, the consequences can be dire. Therefore, many organizations have dedicated database storage servers as a precaution.
3. Security
The C/S structure is suitable for systems used by specific personnel, allowing for strict management and software distribution to ensure system security, making such software relatively secure. In contrast, B/S structured software, due to its larger and more variable user base, tends to have lower security.
Thus, it is evident that the B/S structure has more advantages compared to the C/S structure. Nowadays, a large number of applications are adopting the B/S structure, and many software companies are competing to develop B/S version software, which are web applications. With the development of the Internet, the number of web applications based on the HTTP protocol and HTML standards is growing exponentially, and these web applications are developed using various web technologies.