Giving the Monkey a Smaller Club

Over at the ACM blog, there is a terrific article about software design that has direct application to network design and architecture.

The problem is that once you give a monkey a club, he is going to hit you with it if you try to take it away from him.

What do monkeys and clubs have to do with software or network design? The primary point of interaction is security. The club you intend to make your network operator’s life easier is also a club an attacker can use to break into your network, or damage its operation. Clubs are just that way. If you think of the collection of tools as not just tools, but also as an attack surface, you can immediately see the correlation between the available tools and the attack surface. One way to increase security is to reduce the attack surface, and one way to reduce the attack surface is tools, reduce the number of tools—or the club.

The best way to reduce the attack surface of a piece of software is to remove any unnecessary code.

Consider this: the components of any network are actually made up of code. So to translate this to the network engineering world, you can say:

The best way to reduce the attack surface of a network is to remove any unnecessary components.

What kinds of components? Routing protocols, transport protocols, and quality of service mechanisms come immediately to mind, but the number and kind of overlays, the number and kind of virtual networks might be further examples.

There is another issue here that is not security related specifically, but rather resilience related. When you think about network failures, you probably think of bugs in the code, failed connectors, failed hardware, and other such causes. The reality is far different, however—the primary cause of network failures in real life is probably user error in the form of misconfiguration (or misconfiguration spread across a thousand routers through the wonders of DevOps!). The Mean Time Between Mistakes (MTBM) is a much larger deal than most realize. Giving the operator too many knobs to solve a single problem is the equivalent of giving the monkey a club.

Simplicity in network design has many advantages—including giving the monkey a smaller club.