The application layer of the Internet is believed to be layer 7, the transport layer is layer 4, the IP (internetworking or simply network) layer is layer 3, and the link or subnet layer is layer 2. Three aspects of the Internet architecture deserve special attention. First, the fact that no single company controls any aspect of the infrastructure allows for innovation and evolution without interference from outside parties. The second important feature of the Internet's design is its distributed nature. The original designers intended the Internet to be a global communications system that would be able to accommodate more users than traditional communication systems could. To do this, they decided not to place any restrictions on who can connect to what part of the network. Any individual or organization can set up their own computer on the Internet by purchasing IP addresses from one of several companies that offer this service. They can then connect other computers or devices (such as phones, tablets, or television sets) to these computers via a device called a router. Routers act as intermediaries between different parts of the Internet so that packets can be sent from one location to another. The last important characteristic of the Internet is its ability to survive damage. As mentioned earlier, the core of the Internet is made up of thousands of large organizations that maintain and operate their own networks in order to connect with other networks around the world.