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Usenet Message Format and Special Headers
(Page 2 of 3)
Usenet Header Categories and Common Headers
All Usenet headers are defined according
to the standard header format defined in RFC 822:
<header name>: <header
value>
As with e-mail messages, headers
may extend on to multiple lines, following the indenting
procedure described in the RFC 822 standard.
The current standard for Usenet messages,
RFC 1036, describes the header types for Usenet messages. The headers
are divided into two categories: mandatory headers and optional
headers. Some are the same as headers of the equivalent name used for
e-mail, some are similar to e-mail headers but used in a slightly different
way, while others are unique to Usenet. Table 264
describes these header fields and how they are used.
Table 264: Usenet Header Categories and Headers
Header
Category
|
Header
Name
|
Description
|
Mandatory
Headers
|
From:
|
The e-mail address of the user
sending the message, as for e-mail.
|
Date:
|
The date and
time that the message was originally posted to Usenet. This is usually
the date/time that the user submitted the article to his or her local
NNTP server.
|
Newsgroups:
|
Indicates the newsgroup or set
of newsgroups to which the message is being posted. Multiple newsgroups
are specified by separating them with a comma; for example: Newsgroups:
news.onegroup,rec.secondgroup.
|
Subject:
|
Describes the
subject or topic of the message. Note that this header is mandatory
on Usenet despite being optional for e-mail; it is important because
it is used by readers to decide what messages to open.
|
Message-ID:
|
Provides a unique code for identifying
a message; normally generated when a message is sent. The message ID
is very important in Usenet, arguably more so than in e-mail. The reason
is that delivery of e-mail is performed based on recipient e-mail addresses,
while the propagation
of Usenet messages is controlled using
the message ID header.
|
Path:
|
This is an
informational field that shows the path of servers that a particular
copy of a message followed to get to the server where it is being read.
Each time a server forwards a Usenet article, it adds its own name to
the list in the Path header. The entries are usually separated
by exclamation points.
For example, if a user on Usenet server A posts a message, and
it is transported from A to G, then X, then F
and finally to the server Q where a second user reads it, the
person on server Q would see something like this in the Path
header: Q!F!X!G!A.
|
Optional
Headers
(part 1 of 2)
|
Reply-To:
|
It is possible to reply back
to a Usenet article author using e-mail, which by default goes to the
address in the From: line. If this header is present, the address
it contains is used instead of the default From: address.
|
Sender:
|
This header
indicates the e-mail address of the user who is sending the message,
if different from the message originator. This is functionally the same
as the Sender: header in e-mail messages, but is used in a slightly
different way. Normally, when a Usenet message is posted, the sender's
e-mail address is automatically filled in to the From: line.
If the user manually specifies a different From: line, the address
from which the message was actually sent is usually included in the
Sender: line. This is used to track the true originating point
of articles.
|
Followup-To:
|
A reply to a Usenet message is
usually made back to Usenet itself, and is called a follow-up.
By default, a follow-up goes to the newsgroup(s) specified in the original
message's Newsgroups: header. However, if the Followup-To:
header is included, follow-ups to that message go to the newsgroups
specified in the Followup-To: header instead.
This header is sometimes used to route replies to a message
to a particular group. Note, however, that when a user replies to a
message, this field only controls what appears in the new message's
Newsgroups: line by default. The user can override the Newsgroups:
header manually.
|
Optional
Headers
(part 2 of 2)
|
Expires:
|
All Usenet
messages are maintained on each server for only a certain period of
time, due to storage limitations. The expiration interval for each newsgroup
is controlled by the administrator of each site. If present, this line
requests a different expiration for a particular message; it is usually
used only for special articles. For example, if a weekly announcement
is posted every Monday morning, each article might be set to expire
the following Monday morning, to make sure that people see the most
current version.
|
References:
|
This header lists the message
IDs of prior messages in a conversation. For example, if someone posts
a question to a newsgroup with message ID AA207, and a reply
to that message is made, the software will automatically insert the
line References: AA207 into the reply. This is used by software
to group together articles into conversations (called threads)
to make it easier to follow discussions on busy newsgroups.
|
Control:
|
Indicates that
the article is a control message and specifies a control action to be
performed, such as creating a new newsgroup.
|
Distribution:
|
By default, most messages are
propagated on Usenet worldwide. If specified, this line restricts the
distribution of a message to a smaller area, either geographical or
organizational.
|
Organization:
|
Describes the
organization to which the article sender belongs. Often filled in automatically
with the name of the users Internet Service Provider.
|
Keywords:
|
Contains a list of comma-separated
keywords that may be of use to the readers of the message. Keywords
can be useful when searching for messages on a particular subject matter.
This header is not often used.
|
Summary:
|
A short summary
of the message; again, rarely used in practice.
|
Approved:
|
This header is added by the moderator
of a moderated newsgroup to tell the Usenet software that the message
has been approved for posting.
|
Lines:
|
A count of
the number of lines in the message.
|
Xref:
|
While Usenet articles are identified
by message ID, they are also given a number by each Usenet server as
they are received. These article numbers, which differ from one system
to the next, are usually listed in this cross-reference header.
This information is used when a message is cross-posted to multiple
groups. In that case, as soon as a user reads the message in one group,
it is marked as having been read in all the others where it was posted.
This way, if the user later reads one of those other groups, they will
not see the message again.
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