Using Alternate Access Mappings in Extranet Deployments

Alternate access mappings (AAM) are rules used by SharePoint that describe how to map web requests to the proper web application and site. It tells SharePoint what URLs to return in the content so that users can properly navigate the SharePoint site. Most commonly, AAMs are used with reverse proxy-publishing and load-balancing scenarios. A reverse proxy is a device that sits between the end user and the SharePoint server. Requests made to the SharePoint server are first received by the reverse proxy firewall, such as an Internet request via HTTPS. The reverse proxy will then forward the request to the SharePoint server as an HTTP request. This process is referred to as off-box Secure Sockets Layer (SSL) termination. The AAMs are used to translate the internal URL back to the correct public URL. This ensures that the end user navigates the SharePoint site seamlessly when accessing resources from an external URL. Additional AAM scenarios include forwarding the web requests to different port numbers.