I think its more correct to say x.25 was virtual circuit based - over a packet based system. x.25 had a MFT (Metric Fuck Ton) of error checking (at each layer

I think its more correct to say x.25 was virtual circuit based - over a packet based system. x.25 had a MFT (Metric Fuck Ton) of error checking (at each layer). I used to work in OSI based networking - debugging OSI issues was an art - no wireshark back then However You could do some cool things with osi based networking binary attachments natively supported, years before the internet had it. Interworking between legacy system like Telex, I used to have my own telex number and answerback and could have had an x.400 email address at the country level. Ps id take site you linked with pinch of salt no mention of PAD's for example.