ne tool that network operators use to manage and understand network traffic. It accomplishes this by analyzing the contents of packets transmitted on network operators' landline and mobile networks. For the most part, DPI examines the content in the headers of packets rather than user content. It inspects and looks for patterns in header information, such as error correction, quality of ser- vice, and end-of-message bits, not the e-mail messages themselves. DPI is an application that can potentially be used by carriers to discriminate against competitors' traffic. For example, using DPI, a carrier can slow down or block traffic generated by competitors' services. See Chapter 6, "The Internet," for informa- tion on network neutrality. Network neutrality refers to carriers treating their own and competitors' traffic in an equal manner. Governments can also use DPI to monitor and censor e-mail messages that they might consider harmful. This can be a double-edged sword, however, as DPI can be used, for example, to track terrorists or people critical of the government. DPI helps carriers, ISPs, large universities, and enterprises to understand as well as manage their traffic. Providers can use it to do the following: Prioritize traffic Maintain control over proprietary information Protect networks against hackers Block traffic to certain sites Plan network capacity requirements Deep Packet Inspection: Traffic Management and Monitoring Large, modern packet networks typically carry a mix of rich media traffic, including television, movies, game, voice, and music streams, as well as data. (Previously, packet networks transmitted only data, which requires less capacity and no special treatment.) Faster processers and more affordable memory have led to new DPI switches that enable carriers, large universities, and enterprises to manage congestion in real time as well as offer new services on these diverse mobile and landline networks. In addition, organizations use it to block access to specific non-business-associated web