One thing I’m often asked in email and in person is: why should I bother learning theory? After all, you don’t install SPF in your network; you install a router or switch, which you then configure OSPF or IS-IS on. The SPF algorithm is not exposed to the user, and does not seem to really have any impact on the operation of the network. Such internal functionality might be neat to know, but ultimately–who cares? Maybe it will be useful in some projected troubleshooting situation, but the key to effective troubleshooting is understanding the output of the device, rather than in understanding what the device is doing.
In other words, there is no reason to treat network devices as anything more than black boxes. You put some stuff in, other stuff comes out, and the vendor takes care of everything in the middle. I dealt with a related line of thinking in this video, but what about this black box argument? Do network engineers really need to know what goes on inside the vendor’s black box?
Let me answer this question with another question. Wen you shift to a new piece of hardware, how do you know what you are trying to configure? Suppose, for instance, that you need to set up BGP route reflectors on a new device, and need to make certain optimal paths are taken from eBGP edge to eBGP edge. What configuration commands would you look for? If you knew BGP as a protocol, you might be able to find the right set of commands without needing to search the documentation, or do an internet search. Knowing how it works can often lead you to knowing where to look and what the commands might be. This can save a tremendous amount of time.
Back up from configuration to making equipment purchasing decisions, or specifying equipment. Again, rather than searching the documentation randomly, if you know what protocol level feature you need the software to implement, you can search for the specific support you are looking for, and know what questions to ask about the possible limitations.
And again, from a more architectural perspective–how do you know what protocol to specify to solve any particular problem if you don’t understand how the protocols actually work?
So from configuration to architecture, knowing how a protocol works can actually help you work faster and smarter by helping you ask the right questions. Just another reason to actually learn the way protocols work, rather than just how to configure them.