The Internet is based on a U. S. government project called . Today, the Internet is a collection of networks, tied together by common . Tier 1 networks form the Internet , a system of high-capacity routers and fiber-optic communication links arranged in a(n) topology. Networks that form the Internet are maintained by that offer access to consumers. Before data travels over the Internet, it is divided into by a protocol called , which also reassembles the data when it reaches its destination. Every device on the Internet uses an IP address. addresses are 32 bits long, whereas addresses are 128 bits long, providing billions and billions of possible addresses. Addresses are assigned by servers. IP addresses that are temporarily assigned are called addresses, whereas permanent ones are called addresses. IP addresses cannot be routed over the Internet and are usually assigned to devices within LANs. Because it is difficult to remember IP addresses, the name system allocates easy-to-remember domain names. -level domains include and .edu. The servers that track these names are a vulnerable point in Internet security.