Review: A Protocol for Packet Network Intercommunication

In the paper entitled "A Protocol for Packet Network Intercommunication", Vinton G. Cerf and Robert E. Kahn propose a protocol to be used in interconnecting different packet-switched networks. The protocol is described in fair detail and anticipates certain inter-network communication issues such as establishing and terminating process communications, unreliable networks, flow control, and different data sizes. This protocol is the initial version of the TCP protocol that forms the backbone of the Internet and the modern-day implementation resembles it very closely.

There are two key ideas in this paper that I believe are the keys to understanding how the Internet as we know it today came about. The first idea is the gateway, the point where the boundaries of a network are defined and where messages pass through in order to allow communication between two different networks. The second idea is that of process level communication, which states that messages should pass through the network unmodified since the message contents and its purpose should be defined by the processes running at the endpoints (i.e. the communicating machines). These two ideas mean that, in theory any two devices in the world to communicate for almost any purpose. It is a remarkably simple idea that allowed for the explosive growth and accelerated innovation that makes the Internet very important today.

One very minor shortcoming of the paper is the suggestion that 8-bit network identifiers are sufficient. With 32-bit IPV4 addresses having been exhausted, this proposal is a glaring error, if one that is perhaps most clearly seen in hindsight. Cerf and Kahn may have envisioned at most a few dozen networks with a few supercomputers running thousands of processes whereas the modern-day Internet has millions of networks running dozens or perhaps a few hundred processes. To use an increasingly typical example, the network on my own household has 11 devices, half of which are mostly checking Facebook at any given moment.

While the paper is not meant to be a complete treatment of all concerns in inter-network communication, it is notable how closely the modern-day Internet resembles the protocol that the authors have proposed. While a seed appears to be insignificant with respect to the tree it grows into, the tree itself needs the seed to exist. The modern-day Internet owes its existence to the seed that has been planted in the form of this paper; I cannot see it not being the required initial reading for CS 255.

References

Vinton G. Cerf and Robert E. Kahn, "A Protocol for Packet Network Intercommunication", 1974