How does traffic get through the Internet?
Mung Chiang · Cambridge University Press eBooks · 2012
We have mentioned the Internet many times so far, and all the previous chapters rely on its existence. It is about time to get into the architecture of the Internet, starting with these two chapters on the TCP/IP foundation of the Internet. A Short Answer We will be walking through several core concepts behind the evolution of the Internet, providing the foundation for the next four chapters. So the “short answer” section is going to be longer than the “long answer” section in this chapter. It is tricky to discuss the historical evolution of technologies like the Internet. Some of what we would like to believe to be the inevitable results from careful design are actually the historical legacy of accidents, or the messy requirements of backward compatibility, incremental deployability, and economic incentives. It is therefore not easy to argue about what could have happened, what could have been alternative paths in the evolution, and what different tradeoffs might have been generated. Packet switching The answer to this chapter's question starts with a fundamental idea in designing a network: when your typical users do not really require a dedicated resource, you should allow users to share resources. The word “user” here is used interchangeably with “session.” The logical unit is an application session rather than a physical user or device. For now, assume a session has just one source and one destination, i.e., a unicast session.