This illustration shows two dotted-line boxes, one representing a London installation, the other a Tokyo installation. These boxes are separated by a line bearing the label "Wide Area Network." Within each box, the single sign-on server appears on a separate computer. To the right of it are the directory server and identity management database. These two entities are located within a dotted line box indicating that they reside on the same computer. An arrow runs between the database in one installation and the database in the other, indicating that these databases are replicated. Between the browser and the single sign-on server sits the DNS server for that installation. Arrows run from the browser to the single sign-on server to the directory and finally to the database. A separate arrow represents operations between the single sign-on server and the database that do not involve the directory.