In the last few years, however, the distinction between packet forwarding and application processing has become less clear. New applications are being distributed across the Internet, and in many cases these applications make their own forwarding decisions. These new hybrid applications can sometimes be implemented by extending traditional routers and switches to support a modest amount of application-specific processing. For example, so-called level-7 switches sit in front of server clusters and forward HTTP requests to a specific server based on the requested URL. However, overlay networks are quickly emerging as the mechanism of choice for introducing new functionality into the Internet.