3.3.5 Providing Internet access Public access across the Internet allows enterprise applications to be accessible for employees to log in and work from home or to provide customers with access. However, public access warrants one of the highest levels of security, particularly if sensitive information is to be made accessible. Companies that provide Internet access often come with continuous availability requirements. The architecture shown Figure 3-20 augments the very Highly Secure, Continuously Available environment with Edge Servers to enhance performance. The Edge Server components in this architecture are geographically distributed at strategic locations across the Internet. They are intended to cache static content and place that content in closer proximity to groups of users that suffer from poor performance. Some analysis of the geographic patterns of use must occur to determine where to most effectively place these machines. This performance optimization is commonplace on the Internet. By selecting view source from a browser that is displaying virtually any popular Web site, careful analysis of the Uniform Resource Locators (URLs) in the Hypertext Markup Language (HTML) reveals that the page is actually assembled from numerous sites. To increase performance, these sites are often selected based on the geographic location of end-user's browsers. This architecture is secured by layers of firewalls and reverse proxy mechanisms. It further decreases security risks by protecting the internal machines from each other. For example, in the standard or highly secure architectures, if a Web Application Server machine obtains a virus, there is nothing to prevent that virus from spreading to the Lotus Instant Messaging and Web Conferencing and Lotus Team Workplace machines. A common mistake is to assume that internal machines simply aren't susceptible to viruses