The Internet provides a best effort service. When you want to send data, you just send it. You do not have to know that there is a receiver ready, or that the path exists between you and a potential receiver, or that there are adequate resources along the path for your data. You do not have to give a credit card number or order number so you can be billed. You do not have to check the wire to make sure there are no eavesdroppers.
Some people are uncomfortable with this model. They point out that this makes it hard to carry traffic that needs certain kinds of performance guarantees, or to make communication secure, or to bill people. These three aspects of the Internet are intimately connected, and in this chapter, we examine how research at UCL and elsewhere is leading to a new Internet model which accommodates them.