Re: Win95 FAQ isn't making it to rtfm


Steve Summit (
Wed, 7 May 1997 08:01:09 -0700 (PDT)

In <>, Gordon Fecyk wrote:
> Now I just realized that my computer's clock was a whole week behind (!) so
> maybe THAT had something to do with it. :-) However, would screwed up dates
> cause the posting not to materialize on the archive, or even to propogate
> out to the rest of Usenet?

As a matter of fact, they could. I don't know if this was your
whole problem, and I can't explain exactly why the FAQ list you
mentioned is "disappearing," but I can explain this issue.

A central part of the Usenet news distribution running at any
site is the "history file," which keeps track of every article
which that server has seen recently. Among other things, the
history file is used to reject duplicate articles. Due to
Usenet's "flood fill" algorithm, it's normal for a site to
receive multiple copies of the same article from multiple
sources, and once it's got one copy properly filed, it doesn't
need any more.

Needless to say, with today's Usenet volumes, the history file
can be quite large. (Just now,'s is 66 meg.) One of
the parameters which a Usenet news administrator can tune is the
size of the history file, or stated another way, the length of
time a particular article stays in the history file. A period of
two weeks used to be common, but I wouldn't be surprised if many
sites have moved to one week as the volume has grown. (I don't
know what time interval eskimo's 66 meg history file represents.)

Now comes the interesting part. If an article arrives which is
so old that it wouldn't be in the history file, a site has no way
of knowing whether it had seen that article before or not, so it
discards it anyway. The length of time that articles stay in the
history file is always at least as long as a site's expiration
interval, so an article which is older than the history file
interval would have expired by now whether it had been seen
before or not.

The upshot of this is that the Date: field is one of the vital
headers in a Usenet message. It's not just a random bit of
trivia which is there for (human) readers' benefit; it transmits
information which is central to the news processing and
distribution mechanism. (In a somewhat controversial decision,
at least one major, mainstream piece of news distribution
software a few years ago started rejecting articles whose Date:
lines didn't match the exact format specified by RFC822 and
RFC1036; that way it didn't have to use a more robust but
slower date parser which could deal with so many nonstandard
variations.) If you post an article with a Date: header a week
old, many if not most news systems will treat it as last week's
news, and will quietly discard it.

Steve Summit