Special-purpose devices called routers are designed to read the destination address fields in IP protocol to decide where to send (route) the packet next. The current version of the IP protocol, IPv4, uses 32-bit-long address. Those addresses consist of four 8-bit numbers separated by periods. When users type a URL in their browser, that name is translated into the appropriate address. For example, the Acme Manufacturing Company’s publicly accessible Web server might have an IP address of 135.22.74.10, but anyone wishing to visit the site can enter the URL of www.acme.com in their browser instead of that IP address. An organization’s border router checks the contents of the destination address field of every packet it receives. If the address is not that of the organization, the packet is forwarded on to another router on the Internet. If the destination address matches that of the organization, the packet undergoes one or more tests before being allowed in.