Network Working Group A. Westine
Request for Comments: 1168 A. DeSchon
J. Postel
C.E. Ward
USC/ISI
July 1990
INTERMAIL AND COMMERCIAL MAIL RELAY SERVICES
STATUS OF THIS MEMO
This RFC discusses the history and evolution of the Intermail and
Commercial mail systems. The problems encountered in operating a
store-and-forward mail relay between commercial systems such as
Telemail, MCI Mail and Dialcom are also discussed. This RFC provides
information for the Internet community, and does not specify any
standard. Distribution of this memo is unlimited.
INTRODUCTION
The evolution of large electronic mail systems testifies to the
increasing importance of electronic mail as a means of communication
and coordination throughout the scientific research community.
This paper is a summary of the development of, and a status report
on, an experiment in protocol interoperation between mail systems of
different design. USC/Information Sciences Institute (ISI) began work
on this experiment in 1981 and over the years has provided an
evolving demonstration service for users to exchange mail between the
Internet and a few commercial mail systems.
Recently other organizations have begun to provide similar services,
demonstrating the ongoing need for interoperation of the Internet and
the commercial mail systems. We believe that ISI's pioneering work
in this area has promoted this expansion of service.
These systems include the Internet mail system, the US Sprint
Telemail system, the MCI Mail system, and the Dialcom systems. All of
the systems were designed to operate autonomously, with no convenient
mechanism to allow users of one system to send electronic mail to
users on another system.
The Intermail and Commercial Mail Relay (CMR) services described in
this paper were developed to provide a means for sending mail between
the Internet and these commercial mail systems.
Westine, DeSchon, Postel & Ward [Page 1]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
The Internet is an interconnected system of networks using the SMTP
mail protocol, which includes the ARPANET, MILNET, NSFNET, and about
700 other networks; mail relays allow the exchange of mail with
BITNET, CSNET, and the UUCP networks as well. To the users, this
Internet looks like one large mail system with at least 100,000
computers and at least 400,000 users. Figure 1 illustrates the path
of a message sent by a user on one Internet host to a user on another
Internet host. For more details on the Internet and connected
networks (see Appendix A).
As commercial mail systems came into popular use, it became clear
that a mail link between the Internet and the commercial mail systems
was necessary (see Appendix B). More and more commercial and
research entities needed to communicate with the Internet research
community, and many of these organizations (for one reason or
another) were inappropriate candidates for Internet sites. The
Intermail and CMR services allow these groups to communicate with
Internet users by purchasing electronic mail services from commercial
companies.
INTERMAIL
Intermail is an experimental mail forwarding system that allows users
to send electronic mail across mail system boundaries. The use of
Intermail is nearly transparent, in that users on each system are
able to use their usual mail programs to prepare, send, and receive
messages. No modifications to any of the mail programs on any of the
systems are required. However, users must put some extra addressing
information at the beginning of the body of their messages.
<<< Figure 1 - Internet to Internet Mail >>>
The earliest version of Intermail was developed in 1981, by Jon
Postel, Danny Cohen, Lee Richardson, and Joel Goldberg [1]. It ran on
the TOPS-20 operating system and was used to forward VLSI chip
specifications for the MOSIS project between the ARPANET and the
Telemail system. The original addressing model used in this system
was called "Source Route Forwarding". It was developed to handle
situations in which a message might travel multiple hops before
reaching its destination.
Later, in 1983, Annette DeSchon converted Intermail into a more
general-purpose mail-forwarding system, supporting forwarding between
the Internet mail system and three commercial mail systems: Telemail,
MCI Mail, and Dialcom [3,4].
Westine, DeSchon, Postel & Ward [Page 2]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
As it became apparent that the level of generality of Source Route
Forwarding was not needed, and as Intermail gained acceptance among
users, an easier approach to addressing was developed. The new
addressing model is called "Simple Forwarding". This form of
addressing, like Source Route Forwarding, appears at the beginning of
the text of each message. It can be used to include various Internet
mail header fields in addition to the standard "To" and "Cc" address
fields. This format also allows the use of special address formats,
such as U.S. postal addresses and TELEX addresses, which are
supported by the MCI Mail system. The Intermail system performed
partially automated error handling. Error messages were created by
the Intermail program and were then either approved or corrected by a
human postmaster.
Figure 2 illustrates the pathways between the user mailboxes in the
commercial mail systems and the user mailboxes in the Internet via
the Intermail accounts and program modules. Figure 3 shows the
Intermail processing in more detail.
<<< Figure 2 - Commercial Mail to Intermail >>>
<<< Figure 3 - Intermail Processing >>>
COMMERCIAL MAIL RELAY
In 1988, the Commercial Mail Relay (CMR) was developed to run on a
dedicated UNIX system, replacing the TOPS-20-based Intermail system.
The CMR is a store-and-forward mail link between the Internet and two
commercial systems, Telemail and Dialcom. The only remaining
forwarding performed by the TOPS-20 Intermail system is in support of
the MCI Mail system. (This is planned for conversion to the CMR.)
The CMR supports relay-style addressing in the "Internet to
commercial system" direction, as well as Simple Forwarding in both
directions. One advantage of relay-style addressing is that users
from different commercial systems can appear on Internet mailing
lists. Another advantage is that the reply features of most Internet
user applications can be used by Internet users to respond to mail
that originated on a commercial system. Unfortunately, since we do
not have access to the address-parsing software on the commercial
systems, it is not possible for users of the commercial systems to
enter addresses directly into the message header, and they must
continue to use Simple Forwarding.
The CMR supports automated error handling, which enables the system
to provide faster turnaround on messages containing addressing
errors, and requires much less intervention from a human postmaster.
Westine, DeSchon, Postel & Ward [Page 3]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
DESCRIPTION OF THE CMR SYSTEM
The Multi-channel Memo Distribution Facility (MMDF) is used as the
system mail software because of its notion of separating the mail
queue into separate channels [5]. This makes it easy to dedicate a
channel/queue combination to each commercial system. Internet mail
comes in over the standard SMTP port, and the system parses the
destination address, queuing the message in the proper outgoing
queue. A tag can be added to outgoing traffic so that replies can be
made without any special processing at the destination site.
The CMR uses a relay mailbox on each commercial system. Commercial
users send mail to this mailbox with a Simple Forwarding Header (SFH)
at the head of their message text. Each channel, in addition to
sending outgoing mail into the commercial system, reads all messages
in the relay mailbox and places them in a spool file in the CMR host
computer.
The processing of the spool file is performed by a single daemon. It
parses each commercial system message header to find the sender and
subject, then it searches for and processes the SFH. The SFH
contains the destination Internet addresses. Figure 4a illustrates
the path of mail from the Internet to the commercial sytems. Figure
4b illustrates the path from the commercial systrems to the Internet.
Note: MCI Mail is not yet implemented.
The CMR employs a simple accounting mechanism: a shell script counts
the number of times a string marker occurs in the MMDF logs. At the
end of the month, another script uses an "awk" program to total the
number of messages sent and received with each commercial system. The
Commercial Mail Relay is being developed by Craig E. Ward. Ann
Westine served as the Postmaster for both Intermail and the CMR until
March 1989. Currently, our Action Office serves as Postmaster.
Questions may be sent to "Intermail-Request@ISI.EDU".
<<< Figure 4a - The Internet to Commercial Systems >>>
<<< Figure 4b - Commercial Systems to the Internet >>>
COMMERCIAL SYSTEMS SERVED
The CMR provides mail relay service between the Internet and two
commercial electronic mail systems: the US Sprint Telemail system
and the Dialcom system. A CMR connection to MCI Mail is under
development. MCI Mail is currently served by the TOPS-20 Intermail
system. See Appendix C for recent traffic data.
Westine, DeSchon, Postel & Ward [Page 4]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
Telemail is an international commercial service. Some of the
Telemail systems served by the CMR include MAIL/USA, NASAMAIL/USA,
and GSFC/USA. Some government agencies, such as NASA and the
Environmental Protection Agency, have dedicated Telemail systems.
Companies also exist that purchase bulk services from Telemail and
resell the service to individuals. Omnet's Sciencenet is a very
popular example of this type of service.
Dialcom is a commercial service similar to Telemail in that it has
facilities for allowing groups to purchase tailored services, and
some government agencies (such as the National Science Foundation and
the U.S. Department of Agriculture) have special group-access plans.
The IEEE Computer Society also has a dedicated group service, called
IEEE Compmail, which is open to members of the IEEE Computer Society.
MCI Mail is operated by MCI and is marketed to large companies as
well as individual users.
Specific examples of the users of Intermail and the CMR are as
follows:
1) Scientists in Oceanography, Astronomy, Geology, and Agriculture
use Intermail and the CMR to communicate with colleagues. Many of
these scientists have accounts on "Sciencenet", which is actually
part of a Telemail system administered by Omnet.
(2) The IEEE Computer Society's publication editors use the Dialcom
system "Compmail" to manage the papers being prepared for their
numerous publications. Many of the authors are in university
departments with access to the Internet. Intermail and the CMR
support a significant exchange of large messages containing
manuscripts.
(3) NASA uses Telemail systems for its own work and has extensive
exchanges through its own relay service, as well as Intermail and the
CMR, for communicating with university scientists on the Internet.
Other developments to interoperate between the Internet and
Commercial mail systems are:
(1) The Merit gateway to Sprintmail and IEEE Compmail
(2) The CNRI gateway to MCI Mail
(3) The Ohio State University gateway to Compuserve, and,
(4) NASA-Ames gateway to Telemail
Westine, DeSchon, Postel & Ward [Page 5]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
ACCEPTABLE USE POLICY FOR INTERMAIL AND THE CMR
The Internet is composed of many networks sponsored by many
organizations. However, all the Internet's long-haul networks are
provided by U.S. government agencies. Each of these agencies limits
the use of the facilities it provides in some way. In general, the
statement by an agency about how its facilities may be used is called
an "Acceptable Use Policy".
The various agencies involved in the Internet are currently preparing
their Acceptable Use Policy statements. Most of these are in draft
form and have not been released as official agency statements as yet.
None of these policies are currently available as online documents.
In the least restrictive case, all bona fide researchers and
scholars, public and private, from the United States and foreign
countries (unless denied access by national policy) are allowed
access.
The Intermail and Commercial Mail Relay (CMR) systems at ISI are
resources provided by the Defense Advanced Research Projects Agency
(DARPA) for computing and communication. Use of these resources must
be limited to DARPA-sponsored work or other approved government
business (or must otherwise meet the acceptable use policy of DARPA),
only.
However, DARPA, as a member of the Federal Research Internet
Coordinating Committee (FRICC), has agreed to the FRICC draft policy
for communication networks, which provides in part that: "The member
agencies of the FRICC agree to carry all traffic that meets the
Acceptable Use Policy of the originating member agency".
Thus, e-mail messages (i.e., "traffic") that meet the Acceptable Use
Policy of an agency and pass through some facility of that agency
(i.e., "the originating member") on the way to Intermail or CMR are
allowed.
The current member agencies of the FRICC are DARPA, NSF, DOE, NASA,
and NIH.
BITNET and UUCP (and other) networks are interconnected to the
Internet via mail relays. It is the responsibility of the managers
of these mail relays to ensure that the e-mail messages ("traffic")
that enter the Internet via their mail relays meet the Acceptable Use
Policy of the member agency providing the Internet access.
Westine, DeSchon, Postel & Ward [Page 6]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
In addition, we cannot allow CMR or Intermail to be used simply as a
bridge between two commercial systems, even though CMR has this
technical capability. At least one end of the communication must be
related to FRICC acceptable use.
DETAILS OF CMR SYSTEM USE
The CMR host computer is Internet host INTERMAIL.ISI.EDU
(128.9.2.203). The users of the commercials system are required to
know the proper gateways between the Internet and other networks such
as BITNET, CSNET, or UUCP. Users on networks interconnected to the
Internet likewise need to know how to reach the Internet to send mail
through INTERMAIL.ISI.EDU to a commercial system.
The relay connection to Telemail is through their host TELEMAIL/USA.
The general syntax for Telemail addresses is
"[USER/ORGANIZATION]HOST/COUNTRY", making the full address for the
relay mailbox:
[INTERMAIL/USCISI]TELEMAIL/USA
Users across the entire Telemail service can send mail to this
address. Users on the TELEMAIL host need only send to INTERMAIL.
Internet users can use the basic Telemail format, append a
"%TELEMAIL" to it, and mail to the resulting address as if it really
existed on INTERMAIL.ISI.EDU, e.g.:
[CWARD/USCISI]TELEMAIL/USA%TELEMAIL@INTERMAIL.ISI.EDU
Note that the CMR system will accept anything before the "%TELEMAIL",
that is, the CMR does not validate Telemail addresses before
transmitting them to Telemail.
The CMR handles Dialcom mail delivery in a similar way, but this
system has what might be called "virtual hosts". Groups can be set
up with an alias system to allow easier intra-group access. For
example, both NSF and USDA share the same Dialcom host (157); but,
while both groups send relay messages to Intermail, their actual
fully qualified Dialcom mailboxes are different. For example, NSF's
mailbox is NSF153, and USDA's mailbox is AGS9999.
Mail going in either direction may use an embedded Simple Forwarding
Header. An SFH must be the first part of the message text. It
starts with a "Forward:" field followed by a "To:" field. "Cc:",
"Subject:", and other fields may follow the "To:" fields. The SFH is
terminated by a blank line.
Westine, DeSchon, Postel & Ward [Page 7]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
This is a template of an SFH:
Forward: Destination-Network
To: User@host1, User@host2,
User2@host2
Cc: User@host1
Subject: This subject supercedes the subject in the host net header
<Blank-Line>
Dialcom syntax is "Host-ID:User-ID", for example, 134:ABC1234. This
format will work from any Dialcom host; but users in the same group
as ABC would be able to use the user name, for example, JSMITH.
Using the SFH format, mail to a Dialcom system could be sent as
follows:
To: Intermail@ISI.EDU
Subject: Test Message
Forward: Compmail
To: 134:ABC1234
Here is the text of the message.
Proper destination network names include ARPA, Telemail, Compmail,
NSF-Mail, and USDA-Mail.
It is possible for a user to make mistakes at many points in the
process. Errors are handled as automatically as possible by the CMR.
Many errors are caught in the standard Internet mail traffic, and
users receive the usual error messages from the system. Messages
with incorrect commercial system addresses or faulty SFHs are also
automatically returned to sender. Messages that the software cannot
handle are sent to the CMR's user-service mailbox, Intermail-
Request@ISI.EDU. This mailbox has been set up to take care of user
problems and to be a central distribution point for user
instructions.
PROBLEMS
Several problems arise from the store-and-forward nature of the CMR.
One of the biggest is that almost all of the commercial systems lack
a machine-to-machine interface -- the CMR software must mimic a human
user of the commercial system. Another problem is that the Internet
and a commercial system have different forms (or syntax) for
electronic mail addresses. A major goal of the CMR project is to
make the link between networks as transparent as possible, allowing
Internet users to use off-the-shelf mail programs. Making commercial
Westine, DeSchon, Postel & Ward [Page 8]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
address formats fit the Internet standard is a major task [2].
Compatibility with Internet addressing standards is also a concern.
The commercial accounts are not able to take advantage of the
transparency features of the Domain Name System (DNS) (see Appendix
D); and some commercial addresses are incompatible with the Internet
syntax--this requires Internet users to continue using the older
methods.
Another general problem to be solved is to reduce the amount of time
needed to maintain the system. Because most commercial systems force
our software to mimic a human user, automatic error detection and
handling are quite complex. The Intermail system requires human
intervention in processing failed mail. A goal of the CMR is to
fully automate these processes.
A related problem facing the CMR, as well as its predecessor
Intermail, is the frequency with which commercial systems change
their software. The changes are usually minor and do not bother most
human users; however, the CMR depends on being able to recognize
certain strings. To avoid the necessity of rebuilding the whole CMR
when these strings change, most of the string markers are stored in
ASCII files that are read at run time.
The translation of commercial system addresses has created a new set
of problems, most of which are caused by the use of "special"
characters by the commercial systems.
Telemail uses square brackets ("[" and "]") around user names. While
these characters are not special by Internet standards when found in
the local part of an address, many (perhaps most) Internet mailers
refuse to accept these characters unless they are quoted. MMDF was
modified locally to correct this.
The square bracket problem is even worse for users of IBM mainframe
machines, many of which are used on BITNET. The square bracket is
not a printable character on many BITNET IBM hosts, and all kinds of
strange addresses can result from its use.
The colon is another example. Dialcom uses it as the delimiter
between host and mailbox. However, the colon is a special character
in the Internet mail standard [2]. Users can avoid this problem by
using the SFH and placing the Dialcom address at the beginning of the
message text. Although the CMR can accept addresses with colons,
many Internet hosts and relays are unable to accept addresses that
contain colons. Mail with colons in the address fields is often
rejected by Internet hosts and is returned to the Intermail-Request
mailbox for error processing. This can cause significant delays.
Westine, DeSchon, Postel & Ward [Page 9]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
Problems have also been caused by confusion about which hosts are
mail relays between the Internet and other systems compatible with
the Internet mail standard [2]. (e.g., BITNET, UUCP, and CSNET).
When the CMR was implemented, a decision was made that the CMR would
not keep track of these mail relays. When a relay is changed, as the
BITNET mail relays were in 1988, mail may be rejected because the
host either no longer exists or refuses the mail.
The mail relay problem is a subset of the larger problem of
communicating information about new features and changes to the user
community. Virtually none of the users of the CMR are local. Many
are hidden behind the veil of the commercial system. (Dealing with
commercial system customer support people has proven to be
frustrating -- few of them seem to understand the concept of
machine-to-machine exchanges.) Enhancements to commercial software
that necessitate minor changes can disrupt some CMR users for days.
Another problem that has not been adequately solved is validation of
commercial system addresses and processing of failed commercial
system mail. The Telemail system will not validate a user/host
combination until after the full text of the message has been
transmitted. If a long message is sent to an invalid address, it can
be very expensive in terms of wasted time and connect charges.
Telemail also gives inadequate information when the host is correct
but the user name is not. The failed mail notice received from
Telemail is of little use to either a human reader or the CMR
software. The only information that Telemail returns is the message
ID number -- it provides no subject, and no text to distinguish the
message from the numerous others that pass through the mailbox.
Dialcom does a better job of validating addresses. If an address is
not recognized, the system immediately prompts for a correction. A
simple <RETURN> will delete the invalid address from the list.
The commercial systems are geared for paying customers to send and
receive mail to other paying customers. They are not equipped to
handle reverse billing, or "collect calls." ISI is currently charged
for connect time needed to transmit and receive mail to and from
other Internet sites. A possible solution to this problem would be
to extend the CMR. to include accounting and billing procedures that
would pass the costs of CMR to its users.
What had been GTE Telemail became Sprint SprintMail, Telenet became
Sprintnet, and the host TELEMAIL/USA became SM66/USA.
In April 1990, Sprint installed its X.400 implementation. For the
time being, the old-style Interconnect syntax will work. The CMR
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RFC 1168 Intermail and Commercial Mail Relay Services July 1990
telemail channel and the Simple Forwarding Header (SFH) processor,
were modified to accept either format in the SprintMail "From" field.
Sprint uses the following syntax for X.400:
(O:USCISI,UN:INTERMAIL,TS:SM66)
The SFH processor will "translate" this into:
/O=USCISI/UN=INTERMAIL/TS=SM66/%TELEMAIL
The channel program will reverse the process. In the translation,
parentheses become slashes, colons become equal signs and commas
become slashes and vice versa.
Unfortunately, the translation algorithm is not foolproof. A
Sprint/Internet relay did not use the same field names and values as
those in SprintMail. Consequently, a CMR translated address can not
be sent unmodified to Sprint's relay, Sprint.COM, and Sprint.COM
processed addresses cannot be sent unmodified to the CMR.
From experimentation, the modifications necessary to a CMR processed
address to make it acceptable to Sprint.COM are (1) take the "non-
standard" X.400 fields of "UN" and "TS" and prepend "DD." to them,
(2) add the country field and code (C:US) and (3) add the Telemail
administrative domain name (ADMD:Telemail). The above example would
become:
/O=USCISI/DD.UN=INTERMAIL/DD.TS=SM66/ADMD=TELEMAIL/C=US/@Sprint.COM
The country code must be changed from "US" to "USA." The CMR queue
name must also be appended: "%TELEMAIL."
The situation is further complicated by Sprint's decision to only
relay mail to and from its own administrative domain. Other X.400
ADMDs may be added in the future if payment problems can be overcome.
SprintMail encoded Internet addresses are not parsed correctly by the
SFH processor, but that should not be a major problem -- who on the
Internet is going to send to the commercial side of the relay?
When the NSF decided to terminate NSFMAIL, it became clear that the
CMR Project needed a way to get news out to the commercial users.
The CMR channel programs now are able to append a news file to the
end of messages going into the commercial networks. After
transmitting a message, each channel checks for a news file with the
channel name and if present, sends it.
Westine, DeSchon, Postel & Ward [Page 11]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
The biggest costs of the CMR are the connect times to the Sprintnet
X.25 network and the commercial machines. Making the CMR transmit
faster is the current number one problem.
Three strategies are being pursued:
- Improve the implementation of the current method
- Change the method to take advantage of changes in the commercial
software
- Upgrade the modems and increase the number of phone lines
For a list of known problems or bugs in the CMR software, see the
Appendix of the program logic manual [6].
FUTURE DIRECTIONS
No software project is ever completed, and the CMR is no exception.
There are many possible extensions, some more difficult than others.
One addition that will be made to the CMR is a channel for
interacting with MCI Mail. MCI Mail is one of the original TOPS-20
commercial systems that were serviced by Intermail; the CMR will need
to replace this function before all of the TOPS-20 machines are
removed from service on the Internet.
The adaptability of the CMR is such that adding new commercial
systems should not be a major problem. Additional commercial systems
under consideration include General Electric's GENIE, Western Union's
EasyLink, and Compuserve.
One possible addition to the CMR system could be maintenance of a
list of gateways. This would allow commercial system users to
incorporate the native address formats of other networks into the
SFHs. An advantage of this would be that users could simply tell the
CMR to forward a message to BITNET, for example, and the CMR would
find the gateway and properly format the address for that gateway.
To increase the ease of use to Internet users, the system might treat
each commercial system as an Internet host and create DNS database
records for them. This would allow users to send mail to a non-
Internet user at an Internet-style domain name.
Another improvement would be the possibility of accepting X.400-style
addressing. The current system rejects them.
Westine, DeSchon, Postel & Ward [Page 12]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
In order to further reduce the hazards of string changes in the
commercial system software, an AI component could be added to the
commercial system interfaces. Such an AI component might be able to
"figure out" what marker a new prompt represents and to remember it.
ACCESS INFORMATION
For instructions on how to use Intermail and CMR contact Intermail-
Request@ISI.EDU.
REFERENCES
[1] Cohen, D., "A Suggestion for Internet Message Forwarding for
MOSIS", IEN-180, USC/Information Sciences Institute, March 1981.
[2] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", RFC-822, University of Delaware, August 1982.
[3] DeSchon, A. L., "MCI Mail/ARPA Mail Forwarding", USC/Information
Sciences Institute, ISI Research Report, RR-84-141, August 1984.
[4] DeSchon, A. L., "INTERMAIL, An Experimental Mail Forwarding
System", USC/Information Sciences Institute, ISI Research
Report, RR-85-158, September 1985.
[5] Kingston, D., "MMDF II: A Technical Review", Usenix Conference,
Salt Lake City, August 1984.
[6] Ward, C. E., "The Commercial Mail Relay Project: Intermail on
UNIX", USC/Information Sciences Institute, 1988.
Westine, DeSchon, Postel & Ward [Page 13]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
APPENDIX A
The Internet and Connected Networks
The Internet is a network of networks interconnected by gateways or
routers. The common element is the TCP/IP protocol suite. The
Internet now includes approximately 800 networks and 100,000 host
computers. The Internet is made up of local area networks in
research institutes and university campuses, regional networks, and
long-haul networks. These resources are supported by the using
organizations and by several US goverment agencies (including DARPA,
NSF, NASA, DOE, and NIH). The long-haul networks in the Internet
are the ARPANET, the MILNET, the NSFNET Backbone, the NASA Science
Internet (NSI), and the DOE Energy Science Network (ESNET).
Other systems using TCP/IP or other protocols may be networks of
networks or "internets" with a lower case "i". The capital "I"
Internet is the one described above.
There are other networks with (semi-) compatible electronic mail
systems. These include BITNET (and EARN and NETNORTH), UUCP (and
EUNET), CSNET, ACSNET, and JANET. Users of electronic mail may not
necessarily be aware of the boundaries between these systems and the
Internet.
The Domain Name System (DNS) is a mechanism used in the Internet for
translating names of host computers into addresses. The DNS also
allows host computers not directly on the Internet to have registered
names in the same style.
BITNET (Because It's Time NETwork)
BITNET has about 2,500 host computers, primarily at universities, in
many countries. It is managed by EDUCOM, which provides
administrative support and information services. There are three
main constituents of the network: BITNET in the United States and
Mexico, NETNORTH in Canada, and EARN in Europe. There are also
AsiaNet, in Japan, and connections in South America. Gateways exist
between BITNET and the Internet. The most common gateway used is
CUNYVM.CUNY.EDU.
CSNET (The Computer + Science Network)
CSNET has 180 member organizations, primarily computer science
research laboratories at universities and research institutes,
including international affiliates in more than a dozen countries.
CSNET has adopted DNS-style names for all its host computers. It is
administered by the University Corporation for Atmospheric Research
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RFC 1168 Intermail and Commercial Mail Relay Services July 1990
(UCAR) and provides administrative support and information services
via the CSNET Information Center (CIC) at Bolt Beranek and Newman
(BBN). The gateway between CSNET and the Internet is RELAY.CS.NET.
Note: CSNET and BITNET have officially merged into a single
organization as of October 1, 1989.
UUCP (UNIX to UNIX Copy)
UUCP is a protocol, a set of files, and a set of commands for copying
data files from one UNIX machine to another. These procedures are
widely used to implement a hop-by-hop electronic mail system. This
simple mechanism allows any UNIX host computer to join the system by
arranging a connection (dial-up or permanent) with any UNIX host
already in the system. In the basic UUCP system, mail is source
routed by the sending user through a path of connected hosts to the
destination. Currently, there are databases of connection
information (UUCP maps) and programs (pathalias) that aid in
determining routes. There is some use of DNS-style names by UUCP
hosts. EUNET is a UUCP-based network in Europe, and JUNET is a
similar net in Japan. These international branches of UUCP use DNS-
style names as well. There are many hosts that may relay mail
between UUCP and the Internet. One prominent gateway is
UUNET.UU.NET.
JANET (Joint Academic NETwork)
JANET is the primary academic network in the United Kingdom, linking
about 1,000 computers at about 100 universities and research
institutes. JANET has a domain name system similar to that of the
Internet, but the order of the domain name parts is opposite (with
the top-level domain on the left). The protocols used in JANET are
the UK "Coloured Books". The primary gateway between JANET and the
Internet is NSFNET-RELAY.AC.UK.
ACSNET (Australian Computer Science Network)
ACSNET is the principal electronic mail system for the computer
science and academic research community in Australia, connecting
about 300 sites. It works similarly to UUCP. ACSNET has a domain
naming syntax similar to that for Internet domains. The gateways
between ACSNET and the Internet are MUNNARI.OZ.AU and UUNET.UU.NET.
APPENDIX B
<<< Mail Systems Map >>>
Westine, DeSchon, Postel & Ward [Page 15]RFC 1168 Intermail and Commercial Mail Relay Services July 1990
APPENDIX C
March 1990 sent read total
Telemail 1291 768 2059
MCI Mail 56 44 100
Compmail 634 306 940
NSF-Mail 370 243 613
CGnet 171 82 253
USDA Mail 6 1 7
BellSouth 6 10 16
Other 0 0 0
Total 2534 1454 3988
Days in Month 31
Messages per Day 128.65
April 1990 sent read total
Telemail 1363 696 2059
MCI Mail 40 39 79
Compmail 771 329 1100
CGnet 361 191 552
USDA Mail 28 31 59
BellSouth 98 73 17
Other 0 0 0
Total 2661 1361 4022
Days in Month 30
Messages per Day 134.07
May 1990 sent read total
Telemail 1007 561 1568
MCI Mail 23 12 35
Compmail 815 359 1174
CGnet 406 210 616
USDA Mail 12 5 17
BellSouth 167 93 260
Other 0 0 0
Total 2430 1240 3670
Days in Month 31
Messages per Day 118.39
Westine, DeSchon, Postel & Ward [Page 16]
RFC 1168 Intermail and Commercial Mail Relay Services July 1990
APPENDIX D
The Domain Name System
The Domain Name System (DNS) provides for the translation between
host names and addresses. Within the Internet, this means
translating from a name, such as "ABC.ISI.EDU", to an IP address such
as "128.9.0.123". The DNS is a set of protocols and databases. The
protocols define the syntax and semantics for a query language to ask
questions about information located by DNS-style names. The databases
are distributed and replicated. There is no dependence on a single
central server, and each part of the database is provided in at least
two servers.
In addition to translating names to addresses for hosts that are in
the Internet, the DNS provides for registering DNS-style names for
other hosts reachable (via electronic mail) through gateways or mail
relays. The records for such name registration point to an Internet
host (one with an IP address) that acts as a mail forwarder for the
registered host. For example, the Australian host "YARRA.OZ.AU" is
registered in the DNS with a pointer to the mail relay
"UUNET.UU.NET". This gives electronic mail users a uniform mail
addressing syntax and avoids making them aware of the underlying
network boundaries.
Westine, DeSchon, Postel & Ward [Page 17]
RFC 1168 Intermail and Commercial Mail Relay Services July 1990
SECURITY CONSIDERATIONS
Security issues are not discussed in this memo.
AUTHORS' ADDRESSES
Ann Westine
USC/Information Sciences Instutite
4676 Admiralty Way
Marina del Rey, CA 90292-6695
Phone: (213) 822-1511
EMail: Westine@ISI.EDU
Annette DeSchon
USC/Information Sciences Instutite
4676 Admiralty Way
Marina del Rey, CA 90292-6695
Phone: (213) 822-1511
EMail: DeSchon@ISI.EDU
Jon Postel
USC/Information Sciences Instutite
4676 Admiralty Way
Marina del Rey, CA 90292-6695
Phone: (213) 822-1511
EMail: Postel@ISI.EDU
Craig E. Ward
USC/Information Sciences Instutite
4676 Admiralty Way
Marina del Rey, CA 90292-6695
Phone: (213) 822-1511
EMail: Ward@ISI.EDU
Westine, DeSchon, Postel & Ward [Page 18]
