Subject: #1047 - Paths in USEPRO

From: "Charles Lindsey" <[email-masked]>
Date: Thu, 10 Nov 2005 20:43:43 GMT

Although not immediately relevant to USEFOR, Harald did ask us (on Sept
13th) to consider some related text in USEPRO, because it is closely
related to the syntax in USEFOR. Currently, my latest proposed text in
USEPRO contains 3 paragraphs telling you how to construct a
<path-identity> using
   1. an <fqdn>
   2. an IP address
   3. a <bareword>

Since we have decided to disallow IP addresses in <path-identity>s (they
are now only allowed in <souce-identity>s, aka diagnostics), that second
parapgraph has to come out.

Harald therefore proposed the following:

<Path-identity>s can take the following forms (in decreasing order of
preference):

1. A fully qualified domain name (FQDN) that can be resolved to an email
server via an MX, A or AAAA record according to the procedures of
[RFC2821]; this guarantees that the name is unique, and makes it easy to
contact the administrators if needed.

2. A fully qualified domain name (FQDN) that is guaranteed to be
unique by the administrators of the domain; for instance, the
uniqueness of "server.example.org" could be guaranteed by the
administrator of "example.org" even if nothing is stored in the
DNS for that name.

...

According to [RFC 2142], the forms "usenet@server" and "news@server"
are common addresses for a news server administrator.

His #1 is broadly the same as my #1, but his #2 introduces the possibility
of an FQDN that does not resolve to anything.

I was not happy about that (though it has been seen in the Real World).
Nobody else has expressed an opinion that I can recall, so we are stuck
without a decision.

So I propose a compromise as follows:
   a) we say in #1 that the FQDN "SHOULD" resolve to something (maybe not
      mailable); I agree that the "MUST" implied by my original #1 was a
      bit strong - no great disaster strikes if it is violated.
   b) we are silent about the possibility of its not resolving to
      anything; so anyone who does that has violated a "SHOULD" and maybe
      caused inconvenience to somebody, but that is what goes with any
      "SHOULD" territory.

So #1 would now look like:

1. A fully qualified domain name (FQDN) that SHOULD be resolvable in the
DNS (whether via an A, AAAA or MX record or an equivalent CNAME), thus
guaranteeing a unique identity. Ideally, it will also provide a means to
contact the administrators by email (according to [RFC 2142], the forms
"usenet@server" and "news@server" are common addresses for a news server
administrator).

Harald's #3 (which would then become #2) is virtually the same as mine:

3. Some other (arbitrary) name believed to be unique and registered
at least with all other news-servers sending articles directly to
the given one. This option SHOULD NOT be used unless the earlier
options are unavailable, or unless the name is of longstanding
usage and cessation would be unduly disruptive, or unless one
of the earlier options is provided as well.

Is all that acceptable to everybody?

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131 Fax: +44 161 436 6133   Web: http://www.cs.man.ac.uk/~chl
Email: [email-masked]      Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
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