Ghosts of OSI: The Spectre Haunting IP - the sporks space

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2024-05-09 14:00:05

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?

LDAP. The “Lightweight” Directory Access Protocol comes from the fact it’s basically DAP, but on IP. What’s DAP? That’s the protocol used to access X.500 directories in an OSI network; LDAP is lightweight because it’s on IP. X.500 has a certain hierarchical scheme for describing addressing entities, where you describe them by the properties like country, department, etc. This is all designed to make directory lookups easier. Another aspect is you could then easily route things with mistakes made in the address easily, as the real post office does.

While most other aspects of OSI may be dead, X.500 thrives via LDAP. When both OpenLDAP and Active Directory are built on the foundation of it. Even TLS uses X.500, via X.509. It might not have an entire directory (instead PKI and root certificates), but the core pieces are there.

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