RFC 805 (rfc805) - Page 2 of 6
Computer mail meeting notes
Alternative Format: Original Text Document
Computer Mail Meeting Notes 8 February 1982
principle, be replaced by a "unique-id@location-id" model, where the
unique-id would be a globally unique id for this mailbox (independent
of location) and the location-id would be advice about where to find
the mailbox. However, it was recognized that the "user@host" model
was well established and that so many different elaborations of the
"user" field were already in use that there was no point in persuing
this "unique-id" idea at this time.
Several alternatives for the structuring and ordering of the
extensions to the "host" field to make it into a general
"location-id" were discussed.
These basically involved adding more hierarchical name information
either to the right or the left of the @, with the "higher order"
portion rightmost or leftmost. It was clear that the information
content of all these syntactic alternatives was the same, so that
the one causing least difficulty for existing systems should be
chosen. Hence it was decided to add all new information on the
right of the @ sign, leaving the "user" field to the left
completely to each system to determine (in particular to avoid the
problem that some systems already use dot (.) internally as part
of user names).
The conclusion in this area was that the current "user@host" mailbox
identifier should be extended to "ain" where "domain"
could be a hierarchy of domains.
In particular, the "host" field would become a "location" field
and the structure would read (left to right) from the most
specific to the most general.
For example: "" might be the mailbox of Jon
Postel on host F in the ISI complex of the Internet domain.
Formally, in RFC 733, the host-indicator definition rule would
become:
host indicator = ( "at" / "@" ) domains
domains = node / node "." domains
Note only one "at" or "@" is allowed, and that the domains
form a hierarchy with the most general in scope last.
And note that the choice of domain names must be
administratively controlled and the highest level domain
names must be globally unique.
Postel