Routers are even more intelligent than switches.
They read each packet and send it over the most efficient path possible to the appropriate destination according to a table of rules. This greater intelligence requires more processing, though, making routers less efficient than switches or hubs. The branch-office router is the lifeline back to headquarters. Because WAN bandwidth is expensive, the router uses data compression and knows when to keep local-area network traffic from going out over the connection to the main office. This is especially important over a dial-up connection, such as ISDN, where use is billed by the minute.