< draft-ietf-fax-tiff-07.txt		draft-ietf-fax-tiff-08.txt >
	Network Working Group Glenn Parsons		Network Working Group Glenn Parsons
	Internet Draft James Rafferty		Internet Draft James Rafferty
	Expires in six months December 22, 1997		Expires in six months January 2, 1997
	Tag Image File Format (TIFF) - F Profile for Facsimile		Tag Image File Format (TIFF) - F Profile for Facsimile
	<draft-ietf-fax-tiff-07.txt>		<draft-ietf-fax-tiff-08.txt>
	Status of this Memo		Status of this Memo
	This document is an Internet Draft. Internet Drafts are working		This document is an Internet Draft. Internet Drafts are working
	documents of the Internet Engineering Task Force (IETF), its Areas,		documents of the Internet Engineering Task Force (IETF), its Areas,
	and its Working Groups. Note that other groups may also distribute		and its Working Groups. Note that other groups may also distribute
	working documents as Internet Drafts.		working documents as Internet Drafts.
	Internet Drafts are valid for a maximum of six months and may be		Internet Drafts are valid for a maximum of six months and may be
	updated, replaced, or obsoleted by other documents at any time. It		updated, replaced, or obsoleted by other documents at any time. It
	skipping to change at page 5, line 12 ¶		skipping to change at page 5, line 12 ¶
	such as facsimile terminals where a complex file structure is		such as facsimile terminals where a complex file structure is
	difficult to support.		difficult to support.
	3.1.4 Practical Guidelines for Writing/Reading Multi-Page TIFF-F Files		3.1.4 Practical Guidelines for Writing/Reading Multi-Page TIFF-F Files
	Traditionally, historical TIFF-F has required readers and writers		Traditionally, historical TIFF-F has required readers and writers
	to be able to handle multi-page TIFF-F files. Based on the		to be able to handle multi-page TIFF-F files. Based on the
	experience of various TIFF-F implementors, it has been seen that		experience of various TIFF-F implementors, it has been seen that
	the implementation of TIFF-F can be greatly simplified if certain		the implementation of TIFF-F can be greatly simplified if certain
	practical guidelines are followed when writing multi-page TIFF-F		practical guidelines are followed when writing multi-page TIFF-F
	files.		files. However, for interchange robustness, TIFF-F readers SHOULD
			be prepared to read TIFF files whose structure is consistent with
			[TIFF], which supports a more flexible file structure than is
			recommended here.
	The structure for a multi-page TIFF-F file will include one IFD per		The structure for a multi-page TIFF-F file will include one IFD per
	page of the document. Therefore, each IFD will define the		page of the document. Therefore, each IFD will define the
	attributes for a single page. For simplicity, the writer of TIFF-		attributes for a single page. For simplicity, the writer of TIFF-
	F files SHOULD present IFDs in the same order as the actual		F files SHOULD present IFDs in the same order as the actual
	sequence of pages. (The pages are numbered within TIFF-F beginning		sequence of pages. (The pages are numbered within TIFF-F beginning
	with page 0 as the first page and then ascending (i.e. 0, 1, 2,		with page 0 as the first page and then ascending (i.e. 0, 1, 2,...).
	...). However, as noted in section 3.1.3, any field values over 4		However, as noted in section 3.1.3, any field values over 4 bytes
	bytes will be stored separately from the IFD. TIFF-F readers SHOULD		will be stored separately from the IFD. TIFF-F readers SHOULD expect
	expect IFDs to be presented in page order, but be able to handle		IFDs to be presented in page order, but be able to handle exceptions.
	exceptions.
	Per [TIFF], the exact placement of image data is not specified.		Per [TIFF], the exact placement of image data is not specified.
	However, the strip offsets for each strip of image are defined from		However, the strip offsets for each strip of image are defined from
	within each IFD. Where possible, a second simplifying assumption		within each IFD. Where possible, a second simplifying assumption
	for the writing of TIFF-F files is to specify that the image data		for the writing of TIFF-F files is to specify that the image data
	for each page of a multi-page document SHOULD be contained within a		for each page of a multi-page document SHOULD be contained within a
	single strip (i.e. one image strip per fax page). The use of a		single strip (i.e. one image strip per fax page). The use of a
	single image strip per page is very useful for implementations such		single image strip per page is very useful for implementations such
	as store and forward messaging, where the file is usually prepared		as store and forward messaging, where the file is usually prepared
	in advance of the transmission, but other assumptions may apply for		in advance of the transmission, but other assumptions may apply for
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 23 ¶
	ImageLength (257). SHORT or LONG. LONG recommended.		ImageLength (257). SHORT or LONG. LONG recommended.
	The total number of scan lines in the image.		The total number of scan lines in the image.
	Compression (259) = 3,4. SHORT.		Compression (259) = 3,4. SHORT.
	This is a required TIFF-F field. The permitted values for TIFF-		This is a required TIFF-F field. The permitted values for TIFF-
	F purposes are 3 and 4 as shown. The default value per		F purposes are 3 and 4 as shown. The default value per
	Baseline TIFF is 1 (Uncompressed), but this value is invalid		Baseline TIFF is 1 (Uncompressed), but this value is invalid
	for facsimile images. Baseline TIFF also permits use of		for facsimile images. Baseline TIFF also permits use of
	value 2 (Modified Huffman encoding), but the data is presented		value 2 (Modified Huffman encoding), but the data is presented
	in a form which is not byte aligned. Instead, TIFF-F specifies		in a form which does not contain EOLs. Instead, TIFF-F specifies
	the value 3 for encoding one-dimensional T.4 Modified Huffman		the value 3 for encoding one-dimensional T.4 Modified Huffman
	or 2-dimensional Modified READ data. The detailed settings		or 2-dimensional Modified READ data. The detailed settings
	which apply for T.4 encoded data are specified using the		which apply for T.4 encoded data are specified using the
	T4Options field. TIFF-F also permits use of the value 4 for		T4Options field. TIFF-F also permits use of the value 4 for
	the compression field, which indicates that the data is coded		the compression field, which indicates that the data is coded
	using a [T.6] compression method (i.e the Modified Modified		using a [T.6] compression method (i.e the Modified Modified
	READ two-dimensional method). The detailed settings which apply		READ two-dimensional method). The detailed settings which apply
	for T.6 encoded data are specified using the T6Options field.		for T.6 encoded data are specified using the T6Options field.
	Please refer to the definitions of the T4Options and T6Options		Please refer to the definitions of the T4Options and T6Options
	skipping to change at page 18, line 7 ¶		skipping to change at page 18, line 7 ¶
	For Modified READ encoding, each line is terminated by an EOL and a		For Modified READ encoding, each line is terminated by an EOL and a
	one bit tag bit. Per [T.4], the value of the tag bit is 0 if the		one bit tag bit. Per [T.4], the value of the tag bit is 0 if the
	next line contains two dimensional data and 1 if the next line is a		next line contains two dimensional data and 1 if the next line is a
	reference line. To maintain byte alignment, fill bits are added		reference line. To maintain byte alignment, fill bits are added
	before the EOL/tag bit sequence, so that the first bit of data		before the EOL/tag bit sequence, so that the first bit of data
	following an MR tag bit begins on a byte boundary.		following an MR tag bit begins on a byte boundary.
	3.8.4 EOL		3.8.4 EOL
	As illustrated in FIGURE 1/T.4 in [T.4], facsimile documents		As illustrated in FIGURE 1/T.4 in [T.4], facsimile documents encoded
	encoded with Modified Huffman begin with an EOL (which in TIFF-F is		with Modified Huffman begin with an EOL (which in TIFF-F may be
	byte-aligned). The last line of the image is not terminated by an		byte-aligned). The last line of the image is not terminated by an
	EOL. In a similar respect, images encoded with Modified READ two		EOL. In a similar respect, images encoded with Modified READ two
	dimensional encoding begin with an EOL, followed by a tag bit.		dimensional encoding begin with an EOL, followed by a tag bit.
	3.8.5 RTC Exclusion		3.8.5 RTC Exclusion
	Aside from EOLs, TIFF-F files have historically only contained		Aside from EOLs, TIFF-F files have historically only contained
	image data. This means that implementations which wish to maintain		image data. This means that implementations which wish to maintain
	strict conformance with the rules in [TIFF] and compatibility with		strict conformance with the rules in [TIFF] and compatibility with
	historical TIFF-F, SHOULD NOT include the Return To Control		historical TIFF-F, SHOULD NOT include the Return To Control
	skipping to change at page 22, line 28 ¶		skipping to change at page 22, line 28 ¶
	messaging systems can often handle fax store-and-forward		messaging systems can often handle fax store-and-forward
	capabilities in addition to traditional voice message store-and-		capabilities in addition to traditional voice message store-and-
	forward functions. As a result, TIFF-F fax messages can optionally		forward functions. As a result, TIFF-F fax messages can optionally
	be sent between compliant VPIM systems, and may be rejected if the		be sent between compliant VPIM systems, and may be rejected if the
	recipient system cannot deal with fax.		recipient system cannot deal with fax.
	Refer to the VPIM Specification for proper usage of this content.		Refer to the VPIM Specification for proper usage of this content.
	6. Security Considerations		6. Security Considerations
	This document describes the encoding for TIFF-F, which is an		This document describes the encoding for TIFF-F, which is a profile
	application of the TIFF encoding. As such, it does not create any		of the TIFF encoding for facsimile. As such, it does not create any
	security issues not already existing in TIFF (though, none have		security issues not already identified in [TIFFREG], in its use of
	been identified).		fields as defined in [TIFF]. There are also new TIFF fields defined
			within this specification, but they are of a purely descriptive
			nature, so that no new security risks are incurred.
	Further, the encoding specified in this document does not in any		Further, the encoding specified in this document does not in any
	way preclude the use of any Internet security protocol to encrypt,		way preclude the use of any Internet security protocol to encrypt,
	authenticate, or non-repudiate TIFF-F encoded facsimile messages.		authenticate, or non-repudiate TIFF-F encoded facsimile messages.
	7. Authors' Addresses		7. Authors' Addresses
	Glenn W. Parsons		Glenn W. Parsons
	Northern Telecom		Northern Telecom
	P.O. Box 3511, Station C		P.O. Box 3511, Station C
	skipping to change at page 23, line 27 ¶		skipping to change at page 23, line 35 ¶
	Network", June, 1996		Network", June, 1996
	[T.4] ITU-T Recommendation T.4 - "Standardization of Group 3		[T.4] ITU-T Recommendation T.4 - "Standardization of Group 3
	Facsimile Apparatus for Document Transmission", June, 1996		Facsimile Apparatus for Document Transmission", June, 1996
	[T.6] ITU-T Recommendation T.6 - "Facsimile Coding Schemes and		[T.6] ITU-T Recommendation T.6 - "Facsimile Coding Schemes and
	Coding Control Functions for Group 4 Facsimile Apparatus",		Coding Control Functions for Group 4 Facsimile Apparatus",
	March, 1993		March, 1993
	[TIFF] Adobe Developers Association, TIFF (TM) Revision 6.0 -		[TIFF] Adobe Developers Association, TIFF (TM) Revision 6.0 -
	Final, June 3, 1992.		Final, June 3, 1992.
	[TIFFREG] G. Parsons, J. Rafferty and S. Zilles, "Tag Image File		[TIFFREG] G. Parsons, J. Rafferty and S. Zilles, "Tag Image File
	Format (TIFF) - image/tiff: MIME Sub-type Registration ",Work		Format (TIFF) - image/tiff: MIME Sub-type Registration ",Work
	In Progress, <draft-ietf-fax-tiff-reg-03.txt>, December 1997.		In Progress, <draft-ietf-fax-tiff-reg-04.txt>, January 1997.
	[VPIM2] G. Vaudreuil and G. Parsons, "Voice Profile for Internet		[VPIM2] G. Vaudreuil and G. Parsons, "Voice Profile for Internet
	Mail - version 2", Work In Progress, <draft-ema-vpim-06.txt>,		Mail - version 2", Work In Progress, <draft-ema-vpim-06.txt>,
	November 1997.		November 1997.
	9. Full Copyright Statement		9. Full Copyright Statement
	Copyright (C) The Internet Society (1997). All Rights Reserved.		Copyright (C) The Internet Society (1997). All Rights Reserved.
	This document and translations of it may be copied and furnished to		This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain		others, and derivative works that comment on or otherwise explain
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