Perspective: Feature Velocity¶

This chapter introduces some of the stakeholders in computer networks—network designers, application developers, end users, and network operators—to help motivate the technical requirements that shape how networks are designed and built. This presumes all design decisions are purely technical, but of course, that’s usually not the case. Many other factors, from market forces, to government policy, to ethical considerations, also influence how networks are designed and built.

Of these, the marketplace is the most influential, and corresponds to the interplay between network operators (e.g., AT&T, Comcast, Verizon, DT, NTT, China Mobile), network equipment venders (e.g., Cisco, Juniper, Ericsson, Nokia, Huawei, NEC), application and service providers (e.g., Facebook, Google, Amazon, Microsoft, Apple, Netflix, Spotify), and of course, subscribers and customers (i.e., individuals, but also enterprises and businesses). The lines between these players are not always crisp, with many companies playing multiple roles. The most notable example of this are the large cloud providers, who (a) build their own networking equipment using commodity components, (b) deploy and operate their own networks, and (c) provide end-user services and applications on top of their networks.

When you account for these other factors in the technical design process, you realize there are a couple of implicit assumptions in the textbook version of the story that need to be reevaluated. One is that designing a network is a one-time activity. Build it once and use it forever (modulo hardware upgrades so users can enjoy the benefits of the latest performance improvements). A second is that the job of building the network is largely divorced from the job of operating the network. Neither of these assumptions is quite right.

The network’s design is clearly evolving, and we have documented these changes with each new edition of the textbook over the years. Doing that on a timeline measured in years has historically been good enough, but anyone that has downloaded and used the latest smartphone app knows how glacially slow anything measured in years is by today’s standards. Designing for evolution has to be part of the decision making process.

On the second point, the companies that build networks are almost always the same ones that operate them. They are collectively known as network operators, and they include the companies listed above. But if we again look to the cloud for inspiration, we see that develop-and-operate isn’t true just at the company level, but it is also how the fastest moving cloud companies organize their engineering teams: around the DevOps model. (If you are unfamiliar with DevOps, we recommend you read Site Reliability Engineering: How Google Runs Production Systems to see how it is practiced.)

What this all means is that computer networks are now in the midst of a major transformation, with network operators trying to simultaneously accelerate the pace of innovation (sometimes known as feature velocity) and yet continue to offer a reliable service (preserve stability). And they are increasingly doing this by adopting the best practices of cloud providers, which can be summarized as having two major themes: (1) take advantage of commodity hardware and move all intelligence into software, and (2) adopt agile engineering processes that break down barriers between development and operations.

This transformation is sometimes called the “cloudification” or “softwarization” of the network, but by another name, it is known as Software Defined Networks (SDN). Whatever you call it, this new approach is a game changer, not so much in terms of how we address the fundamental technical challenges of framing, routing, fragmentation/reassembly, packet scheduling, congestion control, security, and so on, but in terms of how rapidly the network evolves to support new features.

This transformation is so important that we take it up again in the Perspective section at the end of each chapter. As these discussions will explore, what happens in the networking industry is partly about technology, but also partly about many other non-technical factors, all of which is a testament to how deeply embedded the Internet is in our lives.