1.2. The Client Tier
The client tier in the three-tier architecture model is usually a web browser. Web browser software processes and displays HTML resources, issues HTTP requests for resources, and processes HTTP responses. As discussed earlier, there are significant advantages to using a web browser as the thin-client layer, including easy deployment and support on a wide range of platforms.
There are many browser products available, and each browser product has different features. The two most popular windowing-based browsers are Netscape and Internet Explorer. While we won't describe all the features of web browsers, they have a common basic set:
Web browsers are the most obvious example of a user agent, a software client that requests resources from a web server. Other user agents include web spiders—automated software that crawls the Web and retrieves web pages—and proxy caches, software systems that retrieve and locally store web pages on behalf of many other user agents.
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