The dominance of the Internet protocol suite has made it hard to think of anything else. Yet in the 80s and 90s, an alternative to the IP model (outside of the proprietary vendor-specific suites like SNA or DECnet) was challenging its rise: the Open Systems Interconnect, or the OSI protocol suite. The short story is while IP won, OSI didn’t disappear completely. It left its view of the world, the seven layer stack, in every CCNA course – even when it doesn’t fit IP at all.

More than that, it also left several protocols still in use today and made its mark on everyday software. They might be rebased onto IP, but their origins were in OSI. Who’s still out there?

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