Post Office Protocol: Version 3: Extended service offerings
RFC 1082
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(November 1988; No errata)
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Network Working Group M. Rose
Request for Comments: 1082 TWG
November 1988
Post Office Protocol - Version 3
Extended Service Offerings
Status of This Memo
This memo suggests a simple method for workstations to dynamically
access mail from a discussion group server, as an extension to an
earlier memo which dealt with dynamically accessing mail from a
mailbox server using the Post Office Protocol - Version 3 (POP3).
This RFC specifies a proposed protocol for the Internet community,
and requests discussion and suggestions for improvements. All of the
extensions described in this memo to the POP3 are OPTIONAL.
Distribution of this memo is unlimited.
Introduction and Motivation
It is assumed that the reader is familiar with RFC 1081 that
discusses the Post Office Protocol - Version 3 (POP3) [RFC1081].
This memo describes extensions to the POP3 which enhance the service
it offers to clients. This additional service permits a client host
to access discussion group mail, which is often kept in a separate
spool area, using the general POP3 facilities.
The next section describes the evolution of discussion groups and the
technologies currently used to implement them. To summarize:
o An exploder is used to map from a single address to
a list of addresses which subscribe to the list, and redirects
any subsequent error reports associated with the delivery of
each message. This has two primary advantages:
- Subscribers need know only a single address
- Responsible parties get the error reports and not
the subscribers
Rose [Page 1]
RFC 1082 POP3 Extended Service November 1988
o Typically, each subscription address is not a person's private
maildrop, but a system-wide maildrop, which can be accessed
by more than one user. This has several advantages:
- Only a single copy of each message need traverse the
net for a given site (which may contain several local
hosts). This conserves bandwidth and cycles.
- Only a single copy of each message need reside on each
subscribing host. This conserves disk space.
- The private maildrop for each user is not cluttered
with discussion group mail.
Despite this optimization of resources, further economy can be
achieved at sites with more than one host. Typically, sites with
more than one host either:
1. Replicate discussion group mail on each host. This
results in literally gigabytes of disk space committed to
unnecessarily store redundant information.
2. Keep discussion group mail on one host and give all users a
login on that host (in addition to any other logins they may
have). This is usually a gross inconvenience for users who
work on other hosts, or a burden to users who are forced to
work on that host.
As discussed in [RFC1081], the problem of giving workstations dynamic
access to mail from a mailbox server has been explored in great
detail (originally there was [RFC918], this prompted the author to
write [RFC1081], independently of this [RFC918] was upgraded to
[RFC937]). A natural solution to the problem outlined above is to
keep discussion group mail on a mailbox server at each site and
permit different hosts at that site to employ the POP3 to access
discussion group mail. If implemented properly, this avoids the
problems of both strategies outlined above.
ASIDE: It might be noted that a good distributed filesystem
could also solve this problem. Sadly, "good"
distributed filesystems, which do not suffer
unacceptable response time for interactive use, are
few and far between these days!
Given this motivation, now let's consider discussion groups, both in
general and from the point of view of a user agent. Following this,
extensions to the POP3 defined in [RFC1081] are presented. Finally,
some additional policy details are discussed along with some initial
experiences.
Rose [Page 2]
RFC 1082 POP3 Extended Service November 1988
What's in a Discussion Group
Since mailers and user agents first crawled out of the primordial
ARPAnet, the value of discussion groups have been appreciated,
(though their implementation has not always been well-understood).
Described simply, a discussion group is composed of a number of
subscribers with a common interest. These subscribers post mail to a
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