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Who still can't post to xml-dev scripsit:
> You mean absolute host names and local ones were once in competition
> for DNS purposes, right? And you say that absolute names triumphed
> because one doesn't see too many local ones in *published* addresses?
No, I mean that before DNS was heard of, there was the Arpanet HOSTS.TXT
file, which specified absolute names for the small subset of connected
computers on the Arpanet, and then there was UUCP naming. Since UUCP-style
names are dead or the nearest thing to it, I will explicate.
Once upon a time, if you weren't lucky enough to be on the Arpanet, you
typically addressed your email something like this:
host1!host2!host3!...!hostn!username
Interpreted as a routing instruction, this meant to pass the email
to the computer named host1, which would pass it to the computer
named host2, which ... would pass it to the computer named hostn
for delivery to hostn's local user named username. Well and good.
But what was the source of these names: host1, host2, etc.? They
had purely local interpretation. Thus, host1 was the name of that
particular computer *according to your local computer*, which had
names for all the computers it could reach directly. And host2,
in turn, was the name of that second computer *according to host1*.
Your computer might have a completely different name for host2,
or no name at all. And as for hostn, that name might be known only
to hostn-1. There was neither in principle nor in practice any
central registry like DNS where these names could be looked up.
This system, while theoretically completely general, had an obious
practical difficulty: how did you give someone an email address
short of sending him an email? As an email traveled through the
system, the sender's address was continuously transformed by prepending
the local name of the last relay, thus making it possible to reply
(provided naming was sufficiently reciprocal, as sometimes it was not).
But how specify it in the first place? In practice, people tended
to specify "bang paths" (bang = !) from certain "well-known hosts"
such as ihnp4, seismo, ucbvax, decvax. (I name them so that old-timers
can have the pleasure of seeing these hostnames once again.)
So if you knew, as people generally did, the correct bang path from
you to the well-known hosts, you could prepend that to your intended
recipient's partial bang path, and hopefully the mail got through.
There was some effort made to map the system as a directed graph with
named links with attached costs, and a program called "pathalias"
was used to rewrite the bang paths into cheaper routes with the same
effect. But the mapping effort, being post hoc, never quite caught
up with reality, and mail loops whereby hosta routed to hostb, which
routed back to hosta, were far from rare.
The DNS, on the other hand, grew out of the inability of all Arpanet
(later Internet) hosts to keep up with the growth of the HOSTS.TXT file,
and the administrative difficulties of managing such a large butflat
absolute name space. Converting the name space to a hierarchy, and
writing a distributed hierarchical implementation, made the DNS
sufficiently scalable to support the many-orders-of-magnitude larger
Internet of today.
For many a year, the domainists and bangists met and did intellectual
battle on the fields of Usenet. Pathalias was even modified to understand
bang paths that contained domain names, but bang paths were finally
sent to the scrap heap by the invention of the ISP, which allowed even
leaf computers to be effectively, if intermittently, on the Internet.
And now though sometimes our email addresses are annoyingly long, or
short but arbitrary, and even from time to time still contain the
dreaded %-hack (which is not documented anywhere, including here),
we can put them even on our business cards, along with those other
absolute names, our postal addresses and worldwide telephone numbers.
Shall relative names return? Who is willing to stand up and be counted?
--
John Cowan <jcowan@reutershealth.com>
http://www.reutershealth.com http://www.ccil.org/~cowan
Yakka foob mog. Grug pubbawup zink wattoom gazork. Chumble spuzz.
-- Calvin, giving Newton's First Law "in his own words"
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