For those with a long memory—no, even longer than that—there were once things called Network Operating Systems (NOS’s). These were not the kinds of NOS’s we have today, like Cisco IOS Software, or Arista EOS, or even SONiC. Rather, these were designed for servers. The most common example was Novell’s Netware. These operating systems were the “bread and butter” of the networking world for many years. I was a Certified Netware Expert (CNE) version 4.0, and then 4.11, before I moved into the routing and switching world. I also deployed Banyan’s Vines, IBM’s OS/2, and a much simpler system called LANtastic, among others.
What were these pieces of software? They were largely built around providing a complete environment for the network user. These systems began with file sharing and directory services and included a small driver that would need to be installed on each host accessing the file share. This small driver was actually a network stack for a proprietary set of protocols. For Vines, this was VIP; for Netware, it was IPX. Over time, these systems began to include email, and then, as a natural outgrowth of file sharing and email, directory services. For some time, there was a serious race on to push ever more features into these network operating systems. For instance, a Vines server could not only act as an email server, a file server, and a directory server, it could also act as a router, connecting two Ethernet segments and pushing traffic between them.
What happened? Why and how did these kinds of systems disappear—almost overnight it seems? After all, they provided a lot of very interesting services. You could use one of these systems as a corporate directory, adding each person’s contact information directly into the system itself. Once the person was there, you could assign them rights to file shares, individual files, and even services running on one of the servers. For instance, you could build an application on a framework within Vines that would run across multiple Vines server—the distribution of the data and the application were all handled in the Vines operating system itself, so long as you built it to their framework—and then simply give people access to it. Lotus Notes, which is still in use today from what I understand was an overlay service of the same style. You didn’t need to worry about access control, the difference between authentication and authorization, etc.; these were all built into the system
Why don’t we see these in widespread use today? The “official” reason, if there is such a thing, is the standardization of the IP protocol stack, and its widespread deployment, caused all of these operating systems to be replaced by a federation of other protocols and applications. For instance, FTP opened up the ability to upload and download files across an IP network, and SMTP standardized the various email clients so email gateways were no longer needed.
A more unofficial answer might be this: these systems tried to do too much. Rather than being a series of smaller systems, each of which solved a particular problem, each of these systems tried to solve every problem, from access control to routing. These systems became bloated and difficult to operate over time. The resource tree, which was grounded in X.500, in Netware 4.11 was a thing of beauty, if you like staring at Mandelbrot patterns. If there were some access control problem, it could take hours to work through the various layers of permissions, and how each was being inherited from the level above.
Further, these large scale, monolithic servers eventually could not keep up with the smaller tools that were being iteratively improved in the IP and OSI protocol suites. As networks grew, and routing became more important, these operating systems struggled to keep up with complex wide area networks.
Network operating systems are another story of complex, multifaceted, monolithic solutions to a lot of different problems. As with all such solutions, smaller, simpler systems simply overrun the capabilities of the monolithic systems through quick iteration of a smaller problem space. While these systems started out simple, they quickly took on too much, and ended up being difficult to deploy and maintain.