wdiff draft-ietf-fax-implementers-guide-07.txt draft-ietf-fax-implementers-guide-08.txt

IETF Fax Working Group Vivian Cancio
Internet Draft RedCreek Communications,Inc.
Category: Work-in-progress Mike Moldovan
Intended Category: Informational G3Nova Technology, Inc.
Hiroshi Tamura
Ricoh Company, LTD.
Dan Wing
Cisco Systems

4 April 2001
Expires: October 2001A new Request for Comments is now available in online RFC libraries.

RFC 3249

Title: Implementers Guide for Facsimile Using Internet
Mail
<draft-ietf-fax-implementers-guide-07.txt>

Status of this memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

[[INTENDED STATUS: This memo provides information for the Internet
community. It does not specify an Internet standard of any kind.
Distribution of this memo is unlimited.]]

Abstract
Author(s): V. Cancio, M. Moldovan, H. Tamura, D. Wing
Status: Informational
Date: September 2002
Mailbox: vcancio@pacbell.net, mmoldovan@g3nova.com,
tamura@toda.ricoh.co.jp, dwing@cisco.com
Pages: 21
Characters: 40413
Updates/Obsoletes/SeeAlso: None

I-D Tag: draft-ietf-fax-implementers-guide-08.txt

URL: ftp://ftp.rfc-editor.org/in-notes/rfc3249.txt

This document is intended for the implementers of software which uses that use
email to send to facsimiles using RFC 2305 and 2532. This is an
informational document and its guidelines do not supersede the
referenced documents.

Table of contents

1. Introduction
1.1 Organization of this document
1.2 Discussion of this document
2. Terminology
3. Implementation Issues Specific to Simple Mode
3.1 Simple Mode Fax Senders
3.1.1 Multipart-alternative
3.2 Simple Mode Fax Receivers
3.2.1 Multipart-alternative and Storage Capacity
4. Implementation Issues Specific to Extended Mode
4.1 Multipart-alternative
4.2 Correlation of MDN with Original Message
4.3 Correlation of DSN with Original Message
4.4 Extended Mode Receivers
4.4.1 Confirmation of receipt and processing from User Agents
4.4.1.1 Discrepancies in MDN [9] Interpretation
4.4.1.2 Disposition-Type and body of message in MDN
4.4.2 "Subject" of MDN and DSN in Success and Failure Cases
4.4.3 Extended Mode Receivers that are MTAs (or ESMTP servers)
4.4.3.1 Success Case Example
4.4.3.2 Failure Case Example 1
4.4.3.3 Failure Case Example 2
4.4.4 Extended Mode Receivers that are POP3/IMAP4
4.4.4.1 Success Case Example
4.4.4.2 Failure Case Example
4.4.5 Receiving Multiple TIFF-FX Attachments
5. Implementation Issues Specific to the File Format
5.1 IFD Placement in TIFF file & Profile-S Constraints
5.2 Precautions for implementers of RFC 2301 [4]
5.2.1 Errors encountered during interoperability testing
5.2.2 Color Gamut Considerations
5.2.3 File format Considerations
5.2.3.1 Considerations for greater reader flexibility
5.2.3.2 Error considerations
6. Implementation Issues for Internet Fax Addressing
7. Security considerations
8. Acknowledgements
9. References
10. Authors' addresses
Full copyright statement
Revision history

1. Introduction

This document clarifies published RFCs which standardize facsimile
communications using Internet Email. The intent is to prevent
implementations that deviate in such a way as to cause
interoperability problems.

1.1 Organization of this document

This document contains four sections that clarify, in order, the
handling of simple mode fax messages, extended mode fax messages, the
file format, and the internet addressing of fax recipients.

See Section 2 for terminology.

1.2 Discussion of this document

Discussion product of this document should take place on the Internet fax
mailing list hosted by the Internet Mail Consortium (IMC). Please
send comments regarding this document to:

ietf-fax@imc.org

To subscribe to this list, send a message with the body 'subscribe'
to "ietf-fax-request@imc.org".

To see what has gone on before you subscribed, please see the mailing
list archive at:

http://www.imc.org/ietf-fax/

2. Terminology

The following terms are used throughout this document:

DSN - RFC 1894, "An Extensible Message Format for
Delivery Status Notifications" [7]
Extended Mode - RFC 2532, "Extended Facsimile Using
Internet Mail" [3]
MDN - RFC 2298, "An Extensible Message Format for
Message Disposition Notifications" [9]
Simple Mode - RFC 2305, "A Simple Mode of Facsimile
Using Internet Mail" [2]
TIFF-FX - RFC 2301, "File Format for Internet Fax" [4]

In examples, "C:" is used to indicate lines sent by the client, and
"S:" to indicate those sent by the server.

3. Implementation Issues Specific to Simple Mode

Issues specific to Simple Mode [2] are described below:

3.1 Simple Mode Fax Senders

3.1.1 Multipart/alternative

Although a requirement of MIME compliance (16, Section 5.1.4), some
email client implementations are not capable of correctly processing
messages with a MIME Content-Type of "multipart/alternative". If a
sender is unsure if the recipient is able to correctly process a
message with a Content-Type of "multipart/alternative", the sender
should assume the worst and not use this MIME Content-Type.

3.2 Simple Mode Fax Receivers

3.2.1 Multipart/alternative and Storage Capacity

Devices with little storage capacity are unable to cache previous
parts of a multipart/alternative message. In order for such devices
to correctly process only one part of a multipart/alternative
message, such devices may simply use the first part of a
multipart/alternative message it is capable of processing.

This behavior means that even if subsequent, higher-fidelity parts
could have been processed they will not be used.

This behavior can cause user dissatisfaction because when two high-
fidelity but low-memory devices are used with each other, the
lowest-fidelity part of the multipart/alternative will be processed.

The solution to this problem is for the sender to determine the
capability of the recipient and send only high fidelity. However a
mechanism to determine the recipient capabilities prior to an initial
message sent to the recipient doesn't yet exist on the Internet.

After an initial message is sent, the Extended Mode mechanism
described in RFC 2532 [3], Section 3.3 enables a recipient to include
its capabilities in a delivery and/or a disposition notification: in
a DSN if the recipient device is an RFC 2532/ESMTP [3] compliant
server or in an MDN if the recipient is a User Agent.

4. Implementation Issues Specific to Extended Mode

Issues specific to Extended Mode [3] fax are described below. Note
that any Extended Mode device also needs to consider issues specific
to Simple Mode (Section 3 of this document).

4.1 Multipart/Alternative

Sections 3.1.1 and 3.2.1 are also applicable to this mode.

4.2. Correlation of MDN with Original Message

To re-iterate a paragraph from section 2.1, RFC 2298 [9]:

A message that contains a Disposition-Notification-To header
SHOULD also contain a Message-ID header as specified in RFC 822
[10]. This will permit automatic correlation of MDNs with original
messages by user agents.

4.3 Correlation Working Group of DSN with Original Message

Similar to the requirement to correlate an MDN, above, DSNs also need
to be correlated.
IETF.

This is best done using the ENVID parameter in the
"MAIL" command. See Sections 3 and 5.4 of RFC 1891 [5] memo provides information for details.

4.4 Extended Mode Receivers

Confirmation that the facsimile image (TIFF-FX attachment) was
delivered and successfully processed is an important aspect of the
extended mode of facsimile using Internet mail. This section
describes implementation issues with several types of confirmations.

4.4.1 Confirmation of receipt and processing from User Agents

When a message is received with the "Disposition-Notification-To"
header and the receiver has determined if the message can be
processed, it may generate a:

a) Negative MDN in case of error, or
b) Positive MDN in case of success

The purpose of receiving a requested MDN acknowledgement from an
Extended Mode recipient is the indication of success or failure to
process the TIFF-FX file attachment that was sent. The attachment,
not the body, constitutes the facsimile message. Therefore an
Extended Mode sender would expect, and it is recommended that the
Extended Mode receiver send (with an MDN), an acknowledgement of the
success or failure to decode and process the TIFF file attachment.

Implementers of the Extended Mode [3] should be consistent in the
feedback provided to senders in the form of error codes and/or
failure/successful messages.

4.4.1.1 Discrepancies in MDN [9] Interpretation

An Extended Mode sender must be aware that RFC 2298 [9] community. It does
not
distinguish between the success or failure to decode the body-content
part of the message and the success or failure to decode a file
attachment. Consequently MDNs may be received which do not reflect
the success or failure to decode the attached TIFF-FX file, but
rather to decode the body-content part of the message.

4.4.1.2 Disposition-Type and body of message in MDN

If the receiver of an MDN request is specify an RFC 2532 compliant device
that automatically prints the received Internet mail messages and
attachments, or forwards the attachment via GSTN fax, it should, in
the case of success:

a) Use a "disposition-type" of "dispatched" (with no "disposition-
modifier") in the MDN, and
b) Use text similar to the following in the body of the message:

"This is a Return Receipt for the mail that you sent to [above, or
below, or this address, etc]. The message and attached files[s] may
have been printed, faxed or saved. This is no guarantee that the
message has been read or understood".

and in the case of failure:

a) Use a "disposition-type" of "processed" and disposition-modifier standard of "error", and
b) Use text similar to the following in the body any kind. Distribution of the message:

"This is a Return Receipt for the mail that you sent to [above, or
below, or this address, etc]. An error occurred while attempting to
decode the attached file[s]".

This recommendation adheres to the definition in RFC 2298 [9] and
helps to distinguish the returned MDNs for proper handling.

Implementers may wish to consider sending messages in the language of
the sender (by utilizing a header field from the original message) or
including multiple languages by using multipart/alternative for the
text portion of the MDN.

4.4.2 "Subject" of MDN and DSN in Success and Failure Cases

Because legacy e-mail applications do not parse the machine-readable
headers, e- mail users depend on the human-readable parts of the MDN
to recognize the type of acknowledgement that is received.

Examples:

MDN:
Subject: Your message was processed successfully. (MDN)
Subject: Your message has been rejected. (MDN)

DSN:
Subject: Your message was delivered successfully. (DSN)
Subject: Your message could not be delivered. (DSN)
Subject: Your message
memo is delayed. (DSN)

4.4.3 Extended Mode Receivers that are MTAs (or ESMTP servers)

SMTP server-based implementations are strongly encouraged to
implement the "SMTP Service Extension for Returning Enhanced Error
Codes" [8]. unlimited.

This standard announcement is easy to implement and it allows detailed
standardized success and error indications to be returned to the
sender by the submitting MTA.

The following examples are provided as illustration only. They should
not be interpreted as limiting the protocol or the DSN form. If the
examples conflict with the definitions in the standards (RFC
1891[5]/1893[6]/1894[7]/2034[8]), the standards take precedence.

4.4.3.1 Success Case Example

In the following example the sender <jean@water.line.com> sends a
message sent to the receiver <ifax@copper.point.com> which is an ESMTP
server IETF list and the receiver successfully decodes the message.

SMTP Sequence:

S: 220 copper.point.com SMTP service ready
C: EHLO foo.com
S: 250-copper.point.com
S: 250-DSN
S: 250 ENHANCEDSTATUSCODES
C: MAIL FROM:<jean@water.line.com> RET=HDRS ENVID=MM123456
S: 250 2.1.0 Originator <jean@water.line.com> ok
C: RCPT TO:<ifax@copper.point.com> NOTIFY=SUCCESS,FAILURE \
ORCPT=rfc822;ifax@copper.point.com
S: 250 2.1.5 Recipient <ifax@copper.point.com> ok
C: DATA
S: 354 Send message, ending in <CRLF>.<CRLF>
C:
C: [Message goes here.]
C:
C: .
S: 250 2.0.0 Message accepted
C: QUIT
S: 221 2.0.0 Goodbye

DSN (to jean@water.line.com):

Date: Mon, 12 Dec 1999 19:01:57 +0900
From: postmaster@copper.point.com
Message-ID: <19991212190157.01234@copper.point.com>
To: jean@water.line.com
Subject: Your message was delivered successfully. (DSN)
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary=JUK199912121854870001

--JUK199912121854870001
Content-type: text/plain

Your message (id MM123456) was successfully delivered
to ifax@copper.point.com.

--JUK199912121854870001
Content-type: message/delivery-status

Reporting-MTA: dns; copper.point.com
Original-Envelope-ID: MM123456
Final-Recipient: rfc822;ifax@copper.point.com
Action: delivered
Status: 2.1.5 (Destination address valid)
Diagnostic-Code: smtp; 250 2.1.5
Recipient <ifax@copper.point.com> ok

--JUK199912121854870001
Content-type: message/rfc822

[headers of returned message go here.]

--JUK199912121854870001--

4.4.3.2 Failure Case Example 1

In this example the receiver determines it is unable to decode the
TIFF file AFTER it has received the SMTP message. The receiver then
sends a 'failure' DSN.

SMTP Sequence:

This is the same as the case a). After the sequence, a decode
error occurs at the receiver, so instead of a 'success' DSN, a
'failure' DSN is sent.

DSN (to jean@water.line.com):

Date: Mon, 12 Dec 1999 19:31:20 +0900
From: postmaster@copper.point.com
Message-ID: <19991212193120.87652@copper.point.com>
To: jean@water.line.com
Subject: Your message could not be delivered. (DSN)
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary=JUK199912121934240002

--JUK199912121934240002
Content-type: text/plain

Your message (id MM123456) to ifax@copper.point.com resulted
in an error while attempting to decode the attached file.

--JUK199912121934240002
Content-type: message/delivery-status

Reporting-MTA: dns; copper.point.com
Original-Envelope-ID: MM123456
Final-Recipient: rfc822;ifax@copper.point.com
Action: Failed
Status: 5.6.1 (Media not supported)
Diagnostic-Code: smtp; 554 5.6.1 Decode error

--JUK199912121934240002
Content-type: message/rfc822

[headers of returned message go here.]

--JUK199912121934240002--

4.4.3.3 Failure Case Example 2

In this example the receiver determines it is unable to decode the
attached TIFF file BEFORE it accepts the SMTP transmission.

SMTP sequence:

S: 220 copper.point.com SMTP service ready
C: EHLO foo.com
S: 250-copper.point.com
S: 250-DSN
S: 250 ENHANCEDSTATUSCODES
C: MAIL FROM:<jean@water.line.com> RET=HDRS ENVID=MM123456
S: 250 2.1.0 Originator <jean@water.line.com> ok
C: RCPT TO:<ifax@copper.point.com> NOTIFY=SUCCESS,FAILURE \
ORCPT=rfc822;ifax@copper.point.com
S: 250 2.1.5 Recipient <ifax@copper.point.com> ok
C: DATA
S: 354 Send message, ending in <CRLF>.<CRLF>
C:
C: [Message goes here.]
C:
C: .
S: 554 5.6.1 Media not supported
C: QUIT
S: 221 2.0.0 Goodbye

DSN:

Note: In this case, the previous MTA generates the DSN that is
forwarded RFC-DIST list.
Requests to the original sender. The receiving MTA has not
accepted delivery and therefore can not generate a DSN.

4.4.4 Extended Mode Receivers that are POP3/IMAP4

NOTE: This document does not define new disposition-types or
disposition-modifiers. Those used below are defined in RFC
2298[9]. This section provides examples on how POP3/IMAP4 devices
may use the already defined values.

These examples are provided as illustration only. They should not be
interpreted as limiting the protocol or the MDN form. If the examples
conflict with the MDN [9] standard, the standard takes precedence.

4.4.4.1 Success Case Example

If the original sender receives an MDN which has "displayed",
"dispatched" or "processed" disposition-type without disposition-
modifier, the receiver may have received or decoded the attached
TIFF-FX file that it sent. The MDN does not guarantee that the
receiver displays, prints or saves the attached TIFF-FX file. See
Section 4.4.1.1, Discrepancies in MDN Interpretation.

NOTE: This example does not include the third component of the
MDN.

Date: 14 Dec 1999 17:48:44 +0900
From: ken_recipient@bronze.dot.com
Message-ID: <19991214174844.98765@silver.dot.com>
Subject: Your message was processed successfully. (MDN)
To: mary@silver.dot.com
Mime-Version: 1.0
Content-Type: multipart/report;
report-type=disposition-notification; boundary="61FD1001_IFAX"

--61FD1001_IFAX
Content-Type: text/plain

This is a Return Receipt for the mail that you sent to
"ken_recipient@bronze.dot.com". The message and attached files may
have been printed, faxed or saved. This is no guarantee that the
message has been read or understood.

--61FD1001_IFAX
Content-Type: message/disposition-notification

Reporting-UA: ken-ifax.bronze.dot.com; barmail 1999.10
Original-Recipient: rfc822;ken_recipient@bronze.dot.com
Final-Recipient: rfc822;ken_recipient@bronze.dot.com
Original-Message-ID: <19991214174010O.mary@silver.dot.com>
Disposition: automatic-action/MDN-send-automatically; dispatched

--61FD1001_IFAX--

4.4.4.2 Failure Case Example

If the original sender receives an MDN with an "error" or "warning"
disposition-modifier, it is possible that the receiver could not
receive or decode the attached TIFF-FX file. Currently there is no
mechanism added to associate the disposition-type with the handling of the
main content body of the message or the attached TIFF-FX file.

Date: 14 Dec 1999 19:48:44 +0900
From: ken_recipient@bronze.dot.com
Message-ID: <19991214194844.67325@silver.dot.com>
Subject: Your message has been rejected. (MDN)
To: mary@silver.dot.com
Mime-Version: 1.0
Content-Type: multipart/report;
report-type=disposition-notification; boundary="84FD1011_IFAX"

--84FD1011_IFAX
Content-Type: text/plain

This is a Return Receipt for the mail that you sent to
"ken_recipient@bronze.dot.com". An error occurred
while attempting to decode the attached file[s]".

--84FD1011_IFAX
Content-Type: message/disposition-notification

Reporting-UA: ken-ifax.bronze.dot.com; barmail 1999.10
Original-Recipient: rfc822;ken_recipient@bronze.dot.com
Final-Recipient: rfc822;ken_recipient@bronze.dot.com
Original-Message-ID: <199912141823123.mary@silver.dot.com>
Disposition: automatic-action/MDN-send-automatically;
processed/error

--84FD1011_IFAX
Content-Type: message/rfc822

[original message goes here]

--84FD1011_IFAX--

4.4.5 Receiving Multiple TIFF-FX Attachments

A received email message could contain multiple TIFF-FX attachments
and each distinct TIFF-FX file may use different encoding and/or
resolution. A received email message could include TIFF-FX attachment
and non-TIFF-FX attachments.

There is currently no mechanism to identify, in a returned MDN, the
attachments that were successfully decoded deleted from those that could not
be decoded.

If the Extended Mode recipient is unable to decode any of the
attached files, it is recommended that the Extended Mode recipient
return a decoding error for the entire message.

5. Implementation Issues Specific to the File Format

5.1 IFD Placement in TIFF file & Profile-S Constraints

a) An IFD is required, by TIFF 6.0, to begin on a word boundary,
however, there is ambiguity with regard to the defined size of
a word. A word should be interpreted as a 2-byte quantity. This
recommendation is based on examination of Figure 1 and the
definition of IFD Entry, Bytes 8-11, found in Section 2 of
TIFF 6.0.

b) Low memory devices, which support resolutions greater than the
required Profile-S, may be memory-constrained such that those
devices cannot properly handle arbitrary placement of TIFF IFDs
within a TIFF file.

To interoperate with a receiver that is constrained, it is
strongly recommended that senders always place the IFD at the
beginning of the TIFF-FX file when using any of the Profiles
defined in RFC 2301.

5.2 Precautions for implementers of RFC 2301 [4]

5.2.1 Errors encountered during interoperability testing
The TIFF/RFC 2301 [4] errors listed below were encountered during
interoperability testing and are provided so that implementers of
TIFF readers and writers can take precautionary measures.

a) Although Profile S of TIFF-FX [4] specifies that files should
be in little-endian order, during testing it was found that
some common TIFF writers create big-endian files. If possible,
the TIFF reader should be coded to handle big-endian files.
TIFF writers IETF distribution list
should always create little-endian files to be
compliant with the standard and sent to allow interoperation with
memory-constrained devices.

b) Bytes 0-1 of the Image File Header are supposed IETF-REQUEST@IETF.ORG. Requests to be set to "II"
(4949h) or "MM" (4d4dh) to indicate the byte order. During
testing, other values were encountered. Readers should handle
cases where the byte order field contain values other than "II"
or "MM", and writers should ensure the correct value is used.

5.2.2 Color Gamut Considerations

The ITULAB encoding (PhotometricInterpretation = 10) allows choosing
a gamut range for L*a*b* (see the TIFF field Decode), which in turn
provides a way to place finer granularity on the integer values
represented in this colorspace. But consequently, an inadequate
gamut choice may cause a loss in the preservation of colors that
don't fall within the space of colors bounded by the gamut. As such,
it is worth commenting on this.

The ITULAB default gamut, L [0,100] a [-85,85] b [-75,125], was
chosen to accommodate most scan devices, which typically acquire from
a hardcopy source. It wasn't chosen
added to deal with the range of color
from camera input or sRGB monitor data. In fact, when dealing with
images from the web and other display oriented sources, the color
range for scanned hardcopy may likely be inadequate. It is important
to use a gamut that matches the source of the image data.

The following guidelines are recommended:
1. When acquiring input deleted from a printed hardcopy source, without
modification, the ITU-T Recommendation T.42 default ITULAB gamut RFC-DIST distribution list should
be appropriate.
2. For an sRGB source the ITU-T Recommendation T.42 default ITULAB
gamut is not appropriate. A more appropriate gamut to consider is:
L [0,100], a [-88,99] and b [-108.8,95.2]. These may be
realized by using the following Decode values for 8-bit data:
(0/1, 100/1, -22440/255, 25245/255, -27744/255, 24276/255).
3. If the range of L*a*b* value can be precomputed efficiently before
converting to ITULAB, then you may get the best result by picking
a gamut that is custom to this range.

5.2.3 File format Considerations

TIFF-FX implementers should make sure of the contents in the
following two sections.

5.2.3.1 Considerations for greater reader flexibility

a) Readers are able to handle cases where IFD offsets point beyond
the end of the TIFF-FX file, while writers ensure the IFD offset
does not point beyond the end of the file.

b) Readers are able sent to handle the first IFD offset being on a
non-word boundary, while writers ensure that the first IFD offset
is RFC-DIST-REQUEST@RFC-EDITOR.ORG.

Details on a word boundary.

c) Readers are flexible and able to accommodate: IFDs that are not
presented in ascending page order; IFDs that are not placed at a
location that precedes the image which the IFD describes; next IFD
offsets that precede the current IFD, the current IFDs' field
data, obtaining RFCs via FTP or the current IFDs' image data. Writers on the other hand
should generate files with IFDs presented in ascending page order;
IFDs placed at a location that precedes the image which the IFD
describes; the next IFD should always follow the current IFD and
all of its data.

d) Writers generate tags with the appropriate type of data (for
example RATIONAL instead of SRATIONAL). Readers are flexible
with those types of misrepresentations that may be readily
accommodated (for example SHORT instead of LONG) and lead to
enhanced robustness.

e) The appropriate count is associated with the tags (it is not 0
and matches the tag requirement) while readers are flexible with
these types of misrepresentations, which EMAIL may be readily
accommodated and lead to enhanced robustness.

f) Tags appear in the correct order in the IFD and readers are
flexible with these types of misrepresentations.

5.2.3.2 Error considerations

a) Readers only accept files with bytes 2-3 of the Image File Header
equal to 42 (2Ah), the "magic number", as being valid TIFF-FX
files, while writers only generate files with the appropriate
magic number.

b) Files are not generated with missing field entries, and readers
reject any such files.

c) The PageNumber value is based on the order within the Primary IFD
chain. The ImageLayer values are based on the layer order and
the image order within the layer respectively. Readers may reject
the pages where the PageNumber or ImageLayer values are not
consistent with the number of Primary IFDs, number of layers or
number of images within the layers.

d) Tags are unique within obtained by sending
an IFD and readers may reject pages where
this is not the case.

e) Strip data does not overlap other file data and the reader may
error appropriately.

f) The strip offset does not point outside the file, under these
conditions readers may reject the page where this is the case.

g) The strip offset + StripByteCounts does not point outside the
file, under these conditions the reader may error appropriately.

h) Only one endian order is used within the file otherwise the
rendered file will be corrupted.

i) Tag values are consistent with the data contained within the
image strip. For example, a bi-level black mark on white
background image strip EMAIL message to rfc-info@RFC-EDITOR.ORG with PhotometricInterpretation tag value
of "1" (bit value of "0" means black) will result in rendering of the image as white marks on a black background (reverse video).

j) message body
help: ways_to_get_rfcs. For the special color spaces (ITULAB, YCBCR, CMYK), the parameters
used example:

To: rfc-info@RFC-EDITOR.ORG
Subject: getting rfcs

help: ways_to_get_rfcs

Requests for transformations are correct and compliant with the
specification.

k) The XPosition and YPosition values are consistent with the
horizontal and vertical offsets of the top-left of the IFD from
the top-left of the Primary IFD, in units of the resolution. To do
otherwise results in misplacement of the rendered image.

l) All combinations of tag values are correct, with special attention
being given to the sets: XResolution, YResolution and
ImageWidth; PhotometricInterpretation, SamplesPerPixel, and
BitsPerSample. Any appropriate combinations will likely result in
image distortion or an inability to render the image.

m) The appropriate Compression types are used for the image layers
within a Profile M file, such as a bi-level coder for the mask
layers (i.e. odd numbered layers) and multi-level (color) coders
for the background and foreground layers. Readers distribution should reject
files where this is not true.

6. Implementation Issues for Internet Fax Addressing

The "+" and "=" characters are valid within message headers, but must
be encoded within some ESMTP commands, most notably ORCPT [5].
Implementations must take special care that ORCPT (and other ESMTP
values) are properly encoded.

For example, the following header is valid as-is:

To: Home Fax <FAX=+390408565@faxmail.com>

but when used with ORCPT, the "=" and "+" must be encoded like this:

RCPT TO:<FAX=+390408565@faxmail.com> \
ORCPT=FAX+3D+2B390408565@faxmail.com

Note the "=" and "+" are valid inside the forward-path, but must be
encoded when used within the esmtp value.

See [5] for details on this encoding.

7. Security considerations

With regards addressed to this document, Sections 5 in RFC 2305 [2] and Section
4 in RFC 2532 [3] apply.

8. Acknowledgements

The authors gratefully acknowledge either the following persons who
contributed or made comments on earlier versions of this memo:
Claudio Allocchio, Richard Coles, Ryuji Iwazaki, Graham Klyne, James
Rafferty, Kensuke Yamada, Jutta Degener and Lloyd McIntyre.

9. References

[1] RFC 2542, "Terminology and Goals for Internet Fax",
Masinter, L.,
March 1999.

[2] RFC 2305, "A Simple Mode
author of Facsimile Using Internet Mail",
Toyoda, K., Ohno, H., Murai, J. and Wing, D.,
March 1998.

[3] RFC 2532, "Extended Facsimile Using Internet Mail",
Masinter, L. and Wing, D.
March 1999.

[4] RFC 2301 "File Format for Internet Fax",
McIntyre, L., Zilles, S., Buckley, R., Venable, D., Parsons, G.
and J. Rafferty,
March 1998.

[5] RFC 1891 "SMTP Service Extension for Delivery Status
Notification",
Moore, K.,
January 1996.

[6] RFC 1893 "Enhanced Mail System Status Codes",
Vaudreuil, G.,
January 1996.

[7] RFC 1894 "An Extensible Message Format for Delivery Status
Notifications",
Moore, K., Vaudreuil, G.,
January 1996.

[8] RFC 2034 "SMTP Service Extension for Returning Enhanced Error
Codes",
Freed, N.,
October 1996.

[9] RFC 2298 "An Extensible Message Format for Message Disposition
Notifications",
Fajman, R.
March 1998.

[10] RFC 822 "Standard for the Format of ARPA Internet Text
Messages",
Crocker. D.,
August 1982.

[11] RFC 821 "A Simple Mail Transfer Protocol",
Postel, D.,
August 1982.

[12] RFC 2303 "Minimal PSTN address format in Internet Mail",
Allocchio, C.
March 1998

[13] RFC 2304 "Minimal FAX address format in Internet Mail",
Allocchio, C.
March 1998

[14] RFC 2846 "GSTN Address Element Extensions in E-mail Services",
Allocchio, C.
June 2000

[15] RFC 1869 "SMTP Service Extensions",
Klensin, J., Freed, N., Rose, M., Stefferud, E., Crocker, D.
November 1995

[16] RFC 2046 "Multipurpose Internet Mail Extensions (MIME) Part Two:
Media Types",
Freed, N., Borenstein, N.
November 1996

10. Authors' addresses

Vivian Cancio
RedCreek Communications, Inc.
3900 Newpark Mall Road
Newark, CA 94560
Telephone: +1-510-745-3905
Facsimile: +1-510-745-3999
Email: vcancio@redcreek.com

Mike Moldovan
G3 Nova Technology, Inc.
2794 Queens Way
Thousand Oaks, CA 91362 USA
Telephone: +1-805-245-4625
Facsimile: +1-805-245-4214
Email: mmoldovan@g3nova.com

Hiroshi Tamura
Ricoh Company, LTD.
2446 Toda, Atsugi City,
Kanagawa-Pref., 243-0023 Japan
Telephone: +81-46-228-1743
Facsimile: +81-46-228-7500
Email: tamura@toda.ricoh.co.jp

Dan Wing
Cisco Systems, Inc.
170 W. Tasman Drive
San Jose, CA 95134-1706 USA
Telephone: +1-408-525-5314
Facsimile: +1-408-527-8083
Email: dwing@cisco.com

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Revision history

[[[RFC editor:
RFC-EDITOR@RFC-EDITOR.ORG. Please remove this section on publication]]]

Version 2
1) Changed first sentence of 4.4.1.1
2) Added Sections: 4.4.1.2, 4.4.1.3, 4.4.1.4, 4.4.2.1, 4.4.2.2, 4.4.2.3,
4.4.3.1, 4.4.3.2 and 4.4.4
3) Deleted Sections: 6 and 7
4) Changed heading of Section 4.4.1
5) In examples: replaced ifax@water.line.com
with ifax@copper.point.com as well as other editorial changes
in the examples through the document.
6) In examples: changed text in subject field of DSN
7) In examples: changed text in subject field of MDN
8) In examples: changed text in text field of MDN
9) Reworded text through out the document
10) Replaced heading in 5.2.1
[to "TIFF Readers: Be Cautious with Headers"]
11) " " 5.2.2
[to "TIFF Writers: Be Cautious in use of IFD"]

Version 3
1) Section 5.2.1 and 5.2.2 were merged into 5.2; some of the
Paragraphs in Section 5 were reworded for clarity.
2) The consult RFC 821 was added to the Reference section.
3) The Reference section format was modified for consistency.
4) A new Section 6 was added.
5) References [9], [10], [11], [12], [13], [14] & [15] were added
in Section 6.
6) Description of [12], [13], [14] & [15] was added to
the Reference section

Version 4

Examples were improved and some of the text was improved or re-arranged.
Section 6 was revised and simplified.

Version 5

1) Table of contents was changed according to real title
and re-labelling.
2) "e) Open implementation issues" text in section 1.1 was deleted.
The outline of this document are added in section 1.1.
3) Section 3.2.1 was modified for clarification.
4) Sub-Section 4.4 was re-labeled.
5) Duplication description ("Disposition-Notification-To:") is deleted
in section 4.4.1
6) The title of section 4.4.1.2 was changed according to the content.
7) Recommended "Subject" texts were modified in section 4.4.2.
The title of this section was changed.
(*** It is the first main change in this version. ***)
According to this modification, the examples in section 4.4.3.1,
4.4.3.2, 4.4.4.1 and 4.4.4.2 were modified.
8) The mail contents of message in the sequence examples of section
4.4.3.1 and 4.4.3.3 was deleted.
9) TIFF "magic number" description was made simple in section 5.2 c).
(*** It is the second main change in this version. ***)
10) Typos and minor modification for clarification (i.e. editorial) were
corrected in section 4, 4.2, 4.4.1, 4.4.1.2, 4.4.3, 4.4.3.1,
4.4.3.2, 4.4.4, 4.4.4.1, 5.1, 5.2, 5.2.1, 5.2.2, 5.2.3, 5.2.4 and 6.
11) The contact information of one of authors was changed.

Version 6

1) Addition that a "word" in TIFF is a 2-byte in Section 5.1.
2) Section 5.2 was re-assembled and divided into new secion
5.2.1 and 5.2.2.
3) Some unfounded items(Child IFDs and GlobalParametersIFD)
in section 5.2 were deleted, according 2223, Instructions to a suggestion.

Version 7

1) Section 5.2.2 was modified RFC
Authors, for more clarification and re-arragened
as section 5.2.3.
2) Add new section 5.2.2 about Color Gamut Considerations. further information.