Do Formal Methodists have Bell-Shaped Heads?

Data networking has not been kind to formal methods. The Internet’s birth gave rise to an intense culture war between the bell-heads and the net-heads, which the net-heads have largely won. In this area formal methodists have long been seen as the humourless enforcers of the defeated bell-heads. The result: formal methods are not a part of the mainstream of data networking and are largely relegated to the the thankless task of reverse engineering (security-related protocols are perhaps the rare exception). If we want to move beyond this situation we must build tools that enhance the ability to engage in the Internet culture — tools that encourage community-based development of open-source systems and embrace the open-ended exploration of design spaces that are only partially understood. 1 State the Problem Before Describing the Solution? The title of this section, sans question mark, is the same as a one-page put-down of the culture of computer networking written by Leslie Lamport in 1978 [7]. The idea is simple and seductive. Start with a specification of the problem that is independent of any solution! Then describe your solution and show that it solves the problem. What could be more simple? Motherhood and apple pie when it comes to technologies like fly-by-wire, software on deep space probes, control systems for nuclear power plants, and so on. But did this make sense in 1978 for the early pioneers of the Internet? Does it make sense today now that the Internet has grown from lab experiment to ubiquitous infrastructure? I don’t think so. The reasons are obvious. The traditional (formal) approach to protocol development is to start with a specification [5]. But we can only specify a problem when we understand what we are doing. Part of the thrill of systems-related networking in the past decades has been in exploring virgin territory opened up by Moore’s law and related exponential curves in bandwidth and memory. In addition, the exploration has not been conducted in a top-down manner, but rather in a grass-roots bottom-up way. And the active community has never agreed on exactly where it was going then or now. When I was hired at Bell Laboratories in 1991 research in Internet-related technologies was essentially banned. The networking professionals (bell-heads) knew that circuits where the only realistic technology and that the “junk” from EE and operating systems (net-heads) would never work. Bell Labs didn’t change this policy until about 1997, by which time it was too late (see Day’s interesting book [4]). Sadly, the situation may be a bit worse in Europe than elsewhere. Many EU countries set up national telecom institutes during the 1970’s, which had the unfortunate consequence of isolating communications engineers from computer scientists. Elsewhere communications has been absorbed into computer science! In networking, formal methods has historically been associated with the losing side of these culture wars.