274 CHAPTER 15 Next-generation Internet architecture · · · On-demand video distribution: Online video distribution has very clear quality of service requirements for low delay and high bandwidth. This application domain requires a network where such requirements can be provided either through explicit QoS functionality or through overprovisioning. In some cases, it may also be beneficial to have multicast support to distribute video to multi- ple receivers in parallel. Secure banking: For secure banking (and many other security-related uses), there is typically an acceptable trade-off toward higher security guarantees at the cost of performance. This application domain may require heavy- weight security protocols to provide authentication of end-system identities, privacy of communication, and defenses against DoS or man-in-the-middle attacks. The use of cryptographic functions in these protocols typically implies that the throughput performance is considerably lower than in conventional networks. Sensor network: Sensor networks are typically based on embedded nodes with a limited battery lifetime. Protocols for such systems aim to minimize the use of energy while providing near real-time access to sensor information. Nodes may be put into a sleep state to conserve their energy. Thus, the net- work protocols used in this domain are fundamentally different from the ones used in the current Internet, where continuous end-to-end connectivity is assumed. These examples illustrate that it is extremely difficult, if not impossible, to design a single network protocol that can provide the performance and QoS needed for video distribution, as well as the security needed for online banking and the energy conservation needed for sensor networks. Therefore, it is desir- able that the future Internet support multiple different networks in parallel. End-user applications can connect to the virtual network that is most suitable for them. Single infrastructure Despite the need for diversity in the protocols used in the network, it is highly desirable to use a single physical infrastructure to provide network connectivity. A single infrastructure allows the amortization of system cost over all networks deployed. This need for sharing cost becomes particularly apparent when consider- ing that the alternative would require the deployment of separate sets of links and routers for each individual network. Sharing of network infrastructure has been a crucial aspect of the current Inter- net. The use of statistical multiplexing for network traffic is at the core of the Internet design and has allowed the Internet to grow to its current scale. However, to support different network protocols, multiplexing has to happen at a different level in the system. Hardware resources need to be shared among networks with different protocols rather than packets within the same network. This kind of resource sharing can be achieved with network virtualization.