Application Working Group M. Ruhl
Internet Draft: Indicating the Presence of a Coverpage Cisco Systems
Document: draft-ietf-fax-coverpage-01.txt Feb. 23, 1999
Expires: Aug. 23, 1999
Indicating the Presence of a Coverpage in the
Fax-over-SMTP Environment
Status of this memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.
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Abstract
In traditional GSTN-based fax, a coverpage is often sent before the
actual document. Some of the uses for a coverpage are:
o routing the document to the correct recipient
o identifying the sender
o providing comments to the recipient about the document
o page count
o transmission date
Current fax-over-SMTP aware applications do not have a standard way
to indicate that a coverpage has been included with a message, or that
there is a good possibilty that a coverpage is part of the message.
This memo provides a mechanism to indicate that a coverpage has been
included or has probably incluced in a message.
1. Background
In traditional GSTN-based fax, a coverpage is often sent before the
actual document. Coverpages typically include information to
identify the sender, the receiver, the date and time, a comment as
to what the message contains, page count, and any other data the
sender deems necessary.
A fax coverpage contains nearly the same information as the SMTP
envelope [SMTP1] and headers [SMTP2].
Fax-over-SMTP applications may or may not include a coverpage when
sending a message. There is currently no method to indicate that
a coverpage has been included with a fax message. Also,
fax-over-SMTP applications that receive a message can have the
ability to generate a coverpage. Knowing when or if to do this
is not defined.
Not knowing if coverpage information has been included can lead to
serveral problems. The most serious of which is that duplicate or
inconsistent data can be generated.
This memo provides a method to indicate that a coverpage is indeed
included or that a coverpage has a good possibilty of being part of
the message.
1.1 Conventions Used in this Document
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
in this document are to be interpreted as defined in "Key words for
use in RFCs to Indicate Requirement Levels" [KEYWORDS].
2. Current Practices for Coverpage Inclusion
When a fax-over-SMTP application sends a message, there are
serveral methods for including a coverpage in the message. All of
those methods are described below:
1) Include the coverpage in the same MIME [MIME1] part as the
document.
2) Include the coverpage in a separate MIME part from the document
MIME part.
3) Include recipient information in the SMTP envelope [GSTNADDR].
4) Not include a coverpage at all.
There is no standard way to indicate which of these methods are
being used. In addition, if the second method is used, there is
no way to identify the separate [MIME] part as a coverpage.
2.1 Analysis of Current Practices
An SMTP message sent by a traditional MUA will almost never include
a coverpage in the message attachment.
Current practices for fax-over-SMTP allow any coverpage to be
included with a message. However, a receiving application has no
indication that the message includes a coverpage. If a receiving
application has the ability to generate a coverpage, there is the
possibilty of duplicate or inconsistant coverpage data being
generated. If a message that has a coverpage included is forwarded,
it may be useful to replace the coverpage. Since there is no way to
identify that a coverpage has been included, the replacement would
require human intervention.
3. Fax-over-SMTP Coverpage Extensions
From the analysis of the current practices, it is apparent that
fax-over-SMTP applications require a method to indicate that a
coverpage may or may not be present. The following methods use
new MIME conetent information to solve this problem.
The MIME sub type defined in the MIME Sub-type Registrations for
Unified Messaging Internet draft [UNIF-MSG], is used as a starting
point for this mechanism.
3.1 Coverpage is Known to be Present
If a fax-over-SMTP application generates a message that will
include a coverpage as part of the message, it MUST generate a
message in the following manner:
1) The top level MIME Content-Type MUST be "multipart/fax-message";
2) The message MUST be a minimum of two MIME parts. The first part
MUST contain the coverpage. Subsequent parts will contain the
document;
3) The MIME part that contains the coverpage MUST have the header
Content-Coverpage with a value of "yes".
4) The MIME part that contains the coverpage SHOULD have the header
Content-Description. The text SHOULD describes the MIME part as
a coverpage;
5) The MIME part that contains the coverpage SHOULD have the header
Content-Disposition. The disposition-type SHOULD be "attachment".
The parameter filename SHOULD indicate that the MIME part is a
coverpage.
If a multipart/fax-message enclosure includes more than one MIME
part that is identified as a coverpage ("Content-Coverpage: yes"),
a receiver SHOULD only use the first part identified as a coverpage.
This will allow a sender forwarded messages to prepend a new
coverpage to a message without removing older coverpages.
The Content-Disposition header will allow traditional MUAs to
decide if the coverpage should be displayed inline, or as an
attachment.
The Content-Description and filename will allow a user to identify
an undisplayed attachment as a coverpage. On issue that should be
noted about the Content-Description, is that it is "human readable"
text. This can cause problems for internationalization and
localization.
3.1.1 Example
The following message include a MIME part which is a coverpage and
a MIME part which is the document being sent.
Date: Tue, 02 Feb 1999 14:40:32 -0800
To: The Boss <FAX=+14445556666@cisco.com>
From: Joe Man <joeman@cisco.com>
Subject: Updating the Document
Mime-Version: 1.0
Content-Type: multipart/fax-message; bounday="theBoundary"
--theBoundary
Content-Type: image/tiff; name="coverpage.tiff"
Content-Coverpage: yes
Content-Transfer-Encoding: base64
Content-Description: This part is a coverpage
Content-Disposition: attachment; filename="coverpage.tiff"
0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAAAAAA
AAAAAAAAEAAAZAAAAAEAAAD+////AAAAAAAAAAD////////////////////
--theBoundary
Content-Type: image/tiff; name="document.tiff"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
--theBoundary--
3.2 Coverpage is Possibly Present
When a fax-over-SMTP application receives a message that might have
a coverpage, it MUST generate the message in the following manner.
1) The Content-Coverpage header MUST be used. The headers value MUST
be "probable";
2) A Content-Description header SHOULD be used. The text SHOULD
indicate that the MIME part might contain a coverpage.
When a fax message is "onramped" (converting a fax message received
from the GSTN network to an SMTP message), there is no way to
determine if coverpage information has been included. However,
because GSTN fax users usually include coverpage information with fax
transmissions, it is very likely that an onramped message will
include a coverpage information as part of the message.
Note: it is entirely possible for coverpage information to be a
separate page, or included with the first page of the message.
3.2.1 Examples
The following message indicates that a coverpage is possibly part
of the document data.
Date: Tue, 02 Feb 1999 14:40:32 -0800
To: Joe Man <joeman@cisco.com>
From: The Boss <FAX=+14445556666@cisco.com>
Subject: Updating the Document
Mime-Version: 1.0
Content-Type: image/tiff; name="document.tiff";
Content-Coverpage: probable
Content-Transfer-Encoding: base64
Content-Description: This document might contain coverpage info
Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
The following message contains more than one body part, and
indicates that a coverpage could be part of the document data.
Date: Tue, 02 Feb 1999 14:40:32 -0800
To: Joe Man <joeman@cisco.com>
From: The Boss <FAX=+14445556666@cisco.com>
Subject: Updating the Document
Mime-Version: 1.0
Content-Type: multipart/fax-message; bounday="theBoundary"
This message was generated by Mike's fax to e-mail generator.
--theBoundary
Content-Type: image/tiff; name="document.tiff"
Content-Coverpage: probable
Content-Transfer-Encoding: base64
Content-Description: This document probably has a coverpage
Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
--theBoundary--
3.3 Coverpage is NOT Present
When a fax-over-SMTP application sends a message with no coverpage,
the message MUST NOT use the "Content-Coverpage" header. If the
application sends a multipart message, it SHOULD use the
"multipart/fax-message" content-type.
3.3.1 Examples
The following message does NOT include a coverpage:
Date: Tue, 02 Feb 1999 14:40:32 -0800
To: Joe Man <joeman@cisco.com>
From: The Boss <FAX=+14445556666@cisco.com>
Subject: Updating the Document
Mime-Version: 1.0
Content-Type: image/tiff; name="document.tiff";
Content-Transfer-Encoding: base64
Content-Description: Picture of the Grand Canyon
Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
The following multipart message does NOT have a coverpage:
Date: Tue, 02 Feb 1999 14:40:32 -0800
To: Joe Man <joeman@cisco.com>
From: The Boss <FAX=+14445556666@cisco.com>
Subject: Updating the Document
Mime-Version: 1.0
Content-Type: multipart/fax-message; bounday="theBoundary"
--theBoundary
Content-Type: text/plain
This message was generated by Mike's fax to e-mail generator.
--theBoundary
Content-Type: image/tiff; name="document.tiff"
Content-Transfer-Encoding: base64
Content-Description: Picture of the Grand Canyon
Content-Disposition: attachment; filename="document.tiff"
AAAADgAAAA8AAAAQAAAAEQAAABIAAAATAAAAFAAAABUAAAAWAAAAFwAAABg
GgAAABsAAAAcAAAAHQAAAB4AAAAfAAAAIAAAACEAAAAiAAAAIwAAACQAAAA
--theBoundary--
3.4 Ramifications to Non-Compliant Applications
If a fax-over-SMTP application is not compliant with the above described
mechanism, there should be no impact. An application that does not
recognize the "multipart/fax-message" content-type will treat the content
type as multipart/mixed as per [MIME2]. If the application does not
recognize the "Content-Coverpage" header, it will be ignored as per
[MIME1].
4. MIME Syntax
4.1 multipart/fax-message
Please see [UINF-MSG] for the multipart/fax-message regristration.
4.2 Content-Coverpage Syntax
Using [ABNF] the Content-Coverpage header is defined as:
MIME-extension-field := "Content-Coverpage" ":" value
value := "yes" /
"probable"
5. Security Considerations
A coverpage can be easily created to mislead the recipient. [SMTP2]
headers can easily be forged. Because of this neither method
should be used as a security measure. Both methods are useful as
informational data about the message.
A cover page might reveal information about the sender and their
activities (sending fax number, time of sending).
Please see [MIME2] for further security considerations.
6. References
[ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
ABNF", RFC 2234, November 1997.
[GSTNADDR] C. Allocchio, "GSTN address element extensions in e-mail
Services", Internet Draft Work in Progress, September 1998.
[KEYWORDS] Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[MIME1] N. Freed, N. Borenstein, "Multipurpose Internet Mail Extensions",
RFC 2045, November 1996.
[MIME2] N. Freed, N. Borenstein, "Multipurpose Internet Mail Extensions",
RFC RFC 2046, November 1996.
[SMTP1] Jonathan B. Postel, "Simple Mail Transfer Protocol", RFC 821,
August 1982.
[SMTP2] David H. Crocker, "Standard for the Format of ARPA Internet Text
Messages, RFC 822, August 13, 1982
[UNIF-MSG] Greg Vaudreuil, Glenn Parsons,"MIME Sub-type Registrations
for unified messaging", Internet Draft Work in Progress,
draft-ema-vpim-um-00.txt, Februrary 1, 1999.
7. Acknowledgements
Thanks to Dan Wing for his suggestions and editorial comments. Without
his help, this document would not say what it does.
Thanks to Larry Masinter for his comments on coverpages and onramps.
Thanks to Graham Kline for all of his general comments.
8. Author Information
Micheal J. Ruhl
Cisco Systems
101 Cooper St.
Santa Cruz, CA 95060
Phone: +1-831-457-5423
Fax: +1-831-457-5208
mruhl@cisco.com