X.400

~ the obit ~

x.400 sits in the part of network history i can read about but cannot personally remember. By the time i got a modem in 1998 the argument was already settled and nobody mentioned that there had been one. Mail was an address with an at sign in the middle of it, and it worked the way water works when you turn a tap. It had not occurred to me that a committee of national telephone monopolies had spent the previous fifteen years trying very hard to make it something else.

The standard came out of CCITT, the body that later became the ITU-T, and the first recommendations were published in october 1984 in what everyone calls the Red Book. A substantially rewritten version followed in 1988, the Blue Book, then more in 1992, and the recommendations were consolidated again as F.400/X.400 in june 1999. ISO published essentially the same architecture in parallel under the name MOTIS. Two standards bodies, one design, and a strong sense on all sides that this was going to be the answer.

The architecture was serious work. Messages moved between Message Transfer Agents and users sat behind User Agents. Above both of those sat two kinds of domain. An Administration Management Domain was run by a country's postal and telephone authority. A Private Management Domain was run by a company inside it. That is not an accident of design, it is the design. X.400 assumed that email would be carried the way telephone calls were carried, by licensed national operators, for money, per message.

For a while it looked inevitable. The United States adopted GOSIP as a federal standard on 15 february 1989 and began enforcing it on 15 august 1990, meaning federal agencies had to buy this stack. European procurement rules pointed the same way. By 1989 twenty two vendors supported it, and by 1994 something like a million mailboxes were connected. Then on 15 may 1995 the American profile was revised to permit specifications from the IETF as well, and after that the interest drained out of the whole OSI project within a few years.

~ the rap sheet ~

~ the address ~

People blame the addresses and people are right to. An X.400 originator and recipient address is a set of labeled attributes rather than a string: country, administration domain, private domain, organization, organizational units, surname, given name, initials. Written out it looks like a form. It was a form. You could not tell it to somebody over the phone without spelling every field, and a mistake in any one of them failed the delivery.

Worse, the fields were not used consistently. The administration domain in particular was sometimes a name and sometimes a single space that had to be preserved exactly, and different national carriers made different choices about it. Getting a message from one X.400 system to another X.400 system was not reliably easier than getting it out to the internet. RFC 1327 was published in 1992 purely to define how X.400 addresses map onto internet ones, and was later reworked as the MIXER specification. When a standard needs a second standard to translate its own addresses, the market has already made a note.

Against this, SMTP was a much shorter document that had shipped in 1982, two years earlier, and cost nothing to implement. The internet side kept changing its specification whenever it needed to, published the result for free, and never asked anybody's ministry for permission. Every feature X.400 had that SMTP lacked, and there were real ones, turned out to matter less than the fact that anyone could write a mail server on a friday.

~ where it still runs ~

Calling this a death is generous to the point of being wrong, which is why the grave says dormant. X.400 is not gone. Air traffic control runs on it: the ATS Message Handling System, AMHS, is built on X.400 profiles and moves flight plans between control centers, replacing the older AFTN teleprinter network. Defense messaging uses it. So do parts of banking and industrial EDI, and Deutsche Telekom has kept an X.400 service running for German industry long after everyone assumed it must have been switched off.

What actually ended in 2007 was its life as ordinary email. Microsoft Exchange had carried an X.400 connector and a message transfer agent for years, and Exchange Server 2007 shipped without either. That was the last place an office worker could have bumped into the thing without knowing what it was. After that it belonged entirely to sectors where a message has to be prioritized and legally accounted for, and where replacing a working system costs more than living with it.

So the standard designed to be universal ended up surviving only in the places where change is prohibitively expensive. It got the wrong kind of permanence. Somewhere over an ocean right now a flight plan is moving between two control centers as an X.400 message, addressed to an organizational unit rather than a person, in a format specified before i had ever seen a computer.

@}-->--

              )
             (_)
            .-'-.
            |   |
            |   |
            |   |
            |   |
          __|   |__   .-.
       .-'  |   |  `-:   :
      :     `---'     :-'
       `-._       _.-'
           '""""""

« previous  ·  random  ·  next »