alt Hacker NewsWebPKI is derived from X.509, but I don't think X.509 lives on anymore. X.500 was stripped down to form LDAP, which is still in very heavy use today. There's still some X.400 systems in existence. I think some of the early cellphone generations may have used the ITU standards in the physical layer?
Of course, the biggest--and weirdest--success of the ITU standards is that the OSI model is still frequently the way networking stacks are described in educational materials, despite the fact that it bears no relation to how any of the networking stack was developed or is used. If you really dig into how the OSI model is supposed to work, one of the layers described only matters for teletypes--which were are a dying, if not dead, technology when the model was developed in the first place.
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X.509 absolutely lives on -- https://www.itu.int/rec/t-rec-x.509 last update was October 2024. However WebPKI uses PKIX which is fairly stubbornly stuck on RFC5280.
On the ITU side, they have made improvements including allowing a plain fully qualified domain name as the subject of a certificate, as an alternative to sequence of set of attributes.
If you mean the presentation layer, hard disagree. Not thinking about presentation creates problems. For example, Go treating ASCII headers as UTF-8 caused trouble. Only slightly not worrying about an HTTP/2 vs HTTP/1.1 mismatch caused trouble for reverse proxies.
Now I'm young enough not to have seen teletypes in an actual production use setting, but I've never heard anyone suggesting the presentation layer was for teletypes. That's just Google-level FUD.
X.500 was stripped down to form LDAP
There's an entire book devoted to ripping up the OSI model: https://docs.google.com/document/d/1iL0fYmMmariFoSvLd9U5nPVH...