INTERNET-DRAFT
Robert Herriot (editor)
Sun Microsystems
Sylvan Butler
Hewlett-Packard
Paul Moore
Microsoft.
Randy Turner
Sharp Labs
October 23, 1997
Internet Printing Protocol/1.0: Protocol Specification
draft-ietf-ipp-protocol-02.txt
Status of this Memo
This document is an Internet-Draft. 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
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or to cite them other than as "work in progress".
To learn the current status of any Internet-Draft, please check the
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ftp.isi.edu (US West Coast).
Abstract
This document is one of a set of documents, which together describe all
aspects of a new Internet Printing Protocol (IPP). IPP is an
application level protocol that can be used for distributed printing
using Internet tools and technology. The protocol is heavily influenced
by the printing model introduced in the Document Printing Application
(ISO/IEC 10175 DPA) standard [dpa]. Although DPA specifies both end
user and administrative features, IPP version 1.0 is focused only on end
user functionality.
The full set of IPP documents includes:
Internet Printing Protocol: Requirements
Internet Printing Protocol/1.0: Model and Semantics
Internet Printing Protocol/1.0: Protocol Specification
The requirements document takes a broad look at distributed printing
functionality, and it enumerates real-life scenarios that help to
clarify the features that need to be included in a printing protocol for
the Internet. It identifies requirements for three types of users: end
users, operators, and administrators. The requirements document calls
out a subset of end user requirements that MUST be satisfied in the
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first version of IPP. Operator and administrator requirements are out
of scope for v1.0. The model and semantics document describes a
simplified model with abstract objects, their attributes, and their
operations. The model introduces a Printer object and a Job object. The
Job object supports multiple documents per job. The protocol
specification is formal document which incorporates the ideas in all the
other documents into a concrete mapping using clearly defined data
representations and transport protocol mappings that real implementers
can use to develop interoperable client and printer (server) side
components.
This document is the ''Internet Printing Protocol/1.0: Protocol
Specification'' document.
Notice
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary rights
which may cover technology that may be required to practice this
standard. Please address the information to the IETF Executive
Director.
Copyright c The Internet Society (date). All Rights Reserved.
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provided that the above copyright notice and this paragraph are included
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LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
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Table of Contents
1. Introduction........................................................4
2. Conformance Terminology.............................................4
3. Encoding of the Operation Layer....................................4
3.1 Picture of the Encoding.........................................5
3.2 Syntax of Encoding..............................................6
3.3 Version.........................................................8
3.4 Mapping of Operations...........................................8
3.5 Mapping of Status-code..........................................8
3.6 Tags............................................................. 8
3.6.1 Delimiter Tags.............................................8
3.6.2 Value Tags.................................................9
3.7 Name-Lengths...................................................11
3.8 Mapping of Attribute Names....................................11
3.9 Value Lengths..................................................12
3.10 Mapping of Attribute Values...................................13
3.11 Data............................................................ 15
4. Encoding of Transport Layer........................................15
4.1 General Headers................................................16
4.2 Request Headers...............................................17
4.3 Response Headers...............................................18
4.4 Entity Headers................................................18
5. Security Considerations............................................19
6. References.........................................................20
7. Author's Address...................................................21
8. Other Participants:................................................22
9. Appendix A: Protocol Examples......................................22
9.1 Print-Job Request..............................................22
9.2 Print-Job Response (successful)................................23
9.3 Print-Job Response (failure)...................................24
9.4 Print-URI Request..............................................25
9.5 Create-Job Request.............................................26
9.6 Get-Jobs Request...............................................26
9.7 Get-Jobs Response..............................................27
10. Appendix B: Mapping of Each Operation in the Encoding.............28
11. Appendix C: Hints to implementors using IPP with SSL3.............32
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1. Introduction
This document contains the rules for encoding IPP operations and
describes two layers: the transport layer and the operation layer.
The transport layer consists of an HTTP/1.1 request or response. RFC
2068 [r2068] describes HTTP/1.1. This document specifies the HTTP
headers that an IPP implementation supports.
The operation layer consists of a message body in an HTTP request or
response. The document "Internet Printing Protocol/1.0: Model and
Semantics" [ipp-m] defines the semantics of such a message body and the
supported values. This document specifies the encoding of an IPP
operation. The aforementioned document [ipp-m] is henceforth referred to
as the "IPP model document"
2. Conformance Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [r2119].
3. Encoding of the Operation Layer
The operation layer SHALL contain a single operation request or
operation response.
The encoding consists of octets as the most primitive type. There are
several types built from octets, but two important types are integers
and characters, on which most other data types are built. Every
character in this encoding SHALL be a member of the UCS-2 coded
character set and SHALL be encoded using UTF-8 which uses 1 to 3 octets
per character. Every integer in this encoding SHALL be encoded as a
signed integer using two's-complement binary encoding with big-endian
format (also known as "network order" and "most significant byte
first"). The number of octets for an integer SHALL be 1, 2 or 4,
depending on usage in the protocol. Such one-octet integers, henceforth
called SIGNED-BYTE, are used for the version and tag fields. Such two-
byte integers, henceforth called SIGNED-SHORT are used for the
operation, status-code and length fields. Four byte integers, henceforth
called SIGNED-INTEGER, are used for values fields.
The following two sections present the operation layer in two ways
. informally through pictures and description
. formally through Augmented Backus-Naur Form (ABNF), as specified by
draft-ietf-drums-abnf-02.txt [abnf]
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3.1 Picture of the Encoding
The encoding for an operation request or response consists of:
-----------------------------------------------
| version | 2 bytes - required
-----------------------------------------------
|operation (request) or status-code (response)| 2 bytes - required
-----------------------------------------------------------
| xxx-attributes-tag | 1 byte |
----------------------------------------------- |-0 or more
| xxx-attribute-sequence | n bytes |
-----------------------------------------------------------
| data-tag | 1 byte - required
-----------------------------------------------
| data | q bytes - optional
-----------------------------------------------
The xxx-attributes-tag and xxx-attribute-sequence represents four
different values of "xxx", namely, operation, job, printer and
unsupported-job. The xxx-attributes-tag and xxx-attribute-sequence may
be omitted if the operation has no attributes or it may be repeated with
the same or different values of "xxx" in ways that are specific to each
operation. The data is omitted from some operations, but the data-tag is
present even when the data is omitted. Note, the xxx-attributestags and
data-tag are called `delimiter-tags'.
Note: the xxx-attribute-sequence, shown above may consist of 0 bytes,
according to the rule below.
An xxx-attributes-sequence consists of zero or more compound-attributes.
-----------------------------------------------
| compound-attribute | s bytes - 0 or more
-----------------------------------------------
A compound-attribute consists an attribute with a single value followed
by zero or more additional values.
Note: a `compound-attribute' represents a single attribute in the model
document. The `additional value' syntax is for attributes with 2 or
more values.
Each attribute consists of:
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-----------------------------------------------
| value-tag | 1 byte
-----------------------------------------------
| name-length (value is u) | 2 bytes
-----------------------------------------------
| name | u bytes
-----------------------------------------------
| value-length (value is v) | 2 bytes
-----------------------------------------------
| value | v bytes
-----------------------------------------------
An additional value consists of:
-----------------------------------------------------------
| value-tag | 1 byte |
----------------------------------------------- |
| name-length (value is 0x0000) | 2 bytes |
----------------------------------------------- |-0 or more
| value-length (value is w) | 2 bytes |
----------------------------------------------- |
| value | w bytes |
-----------------------------------------------------------
Note: an additional value is like an attribute whose name-length is 0.
From the standpoint of a parsing loop, the encoding consists of:
-----------------------------------------------
| version | 2 bytes - required
-----------------------------------------------
|operation (request) or status-code (response)| 2 bytes - required
-----------------------------------------------------------
| tag (delimiter-tag or value-tag) | 1 byte |
----------------------------------------------- |-0 or more
| empty or rest of attribute | x bytes |
-----------------------------------------------------------
| data-tag | 2 bytes - required
-----------------------------------------------
| data | y bytes - optional
-----------------------------------------------
The value of the tag determines whether the bytes following the tag are:
. attributes
. data
. the remainder of a single attribute where the tag specifies the
type of the value.
3.2 Syntax of Encoding
The syntax below is ABNF [abnf] except `strings of literals' SHALL be
case sensitive. For example `a' means lower case `a' and not upper case
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`A'. In addition, SIGNED-BYTE and SIGNED-SHORT fields are represented
as `%x' values which show their range of values.
ipp-message = ipp-request / ipp-response
ipp-request = version operation
*(xxx-attributes-tag xxx-attribute-sequence) data-tag data
ipp-response = version status-code
*(xxx-attributes-tag xxx-attribute-sequence) data-tag data
xxx-attribute-sequence = *compound-attribute
; where "xxx" in the three rules above stands for any of the
following
; values: "operation", "job", "printer" or "unsupported-job".
version = major-version minor-version
major-version = SIGNED-BYTE ; initially %d1
minor-version = SIGNED-BYTE ; initially %d0
operation = SIGNED-SHORT ; mapping from model defined below
status-code = SIGNED-SHORT ; mapping from model defined below
compound-attribute = attribute *additional-values
attribute = value-tag name-length name value-length value
additional-values = value-tag zero-name-length value-length value
name-length = SIGNED-SHORT ; number of octets of `name'
name = LALPHA *( LALPHA / DIGIT / "-" / "_" / "." )
value-length = SIGNED-SHORT ; number of octets of `value'
value = OCTET-STRING
data = OCTET-STRING
zero-name-length = %x00.00 ; name-length of 0
operation-attributes-tag= %x01 ; tag of 1
job-attributes-tag = %x02 ; tag of 2
printer-attributes-tag = %x04 ; tag of 4
unsupported-job-attributes-tag = %x05 ; tag of 5
data-tag = %x03 ; tag of
3
value-tag = %x10-FF
SIGNED-BYTE = BYTE
SIGNED-SHORT = 2BYTE
DIGIT = %x30-39 ; "0" to "9"
LALPHA = %x61-7A ; "a" to "z"
BYTE = %x00-FF
OCTET-STRING = *BYTE
The syntax allows an xxx-attributestag to be present when the xxx-
attribute-sequence that follows is empty. The syntax is defined this way
to allow for the response of Get-Jobs where no attributes are returned
for some job-objects. Although it is RECOMMENDED that the sender not
send an xxx-attributestag if there are no attributes (except in the Get-
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Jobs response just mentioned), the receiver MUST be able to decode such
syntax.
3.3 Version
The version SHALL consist of a major and minor version, each of which
SHALL be represented by a SIGNED-BYTE. The protocol described in this
document SHALL have a major version of 1 (0x01) and a minor version of
0 (0x00). The ABNF for these two bytes SHALL be %x01.00.
3.4 Mapping of Operations
Operations are defined as enums in the model document. An operations
enum value SHALL be encoded as a SIGNED-SHORT
Note: the values 0x4000 to 0xFFFF are reserved for private extensions.
3.5 Mapping of Status-code
Status-codes are defined as enums in the model document. A status-code
enum value SHALL be encoded as a SIGNED-SHORT
If an IPP status-code is returned, then the HTTP Status-Code MUST be 200
(OK). With any other HTTP Status-Code value, the HTTP response SHALL NOT
contain an IPP message-body, and thus no IPP status-code is returned.
3.6 Tags
There are two kinds of tags:
. delimiter tags: delimit major sections of the protocol, namely
attributes and data
. value tags: specify the type of each attribute value
3.6.1 Delimiter Tags
The following table specifies the values for the delimiter tags:
Tag Value (Hex) Delimiter
0x00 reserved
0x01 operation-attributes-tag
0x02 job-attributes-tag
0x03 data-tag
0x04 printer-attributes-tag
0x05 unsupported-job-attributes-tag
0x06-0x0F reserved for future delimiters
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When an xxx-attributes-tag occurs in the protocol, it SHALL mean that
the zero or more following attributes up to the next delimiter tag are
xxx attributes as defined in the model document, where xxx is operation,
job, printer, unsupported-job.
Doing substitution for xxx in the above paragraph, this means the
following. When an operation-attributes-tag occurs in the protocol, it
SHALL mean that the zero or more following attributes up to the next
delimiter tag are operation attributes as defined in the model document.
When an job-attributes-tag occurs in the protocol, it SHALL mean that
the zero or more following attributes up to the next delimiter tag are
job attributes as defined in the model document. When an printer-
attributes-tag occurs in the protocol, it SHALL mean that the zero or
more following attributes up to the next delimiter tag are printer
attributes as defined in the model document. When an unsupported-job-
attributes-tag occurs in the protocol, it SHALL mean that the zero or
more following attributes up to the next delimiter tag are unsupported-
job attributes as defined in the model document.
Each of the four xxx-attributes-tags defined above is OPTIONAL in an
operation and each SHALL occur at most once in an operation, except for
job-attributes-tag in a Get-Jobs response which may occur zero or more
times. The data-tag SHALL occur exactly once in an operation.
If an operation contains an operations-attribute-tag, it SHALL be the
first tag delimiter. The data-tag SHALL be the last tag delimiter.
The order and presence of delimiter tags for each operation request and
each operation response SHALL be that defined in the model document. For
further details, see Section 3.8 Mapping of Attribute Names and
Appendix B: Mapping of Each Operation in the Encoding.
3.6.2 Value Tags
The remaining tables show values for the value-tag, which is the first
octet of an attribute. The value-tag specifies the type of the value of
the attribute. The value of the value-tag of an attribute SHALL either
be a type value specified in the model document or an "out-of-band"
value, such as "unsupported" or "default". If the value of value-tag
for an attribute is not "out-of-band" and differs from the value type
specified by the model document, then a printer receiving such a request
MAY reject the attribute or just the value. A client receiving such a
response MAY ignore the attribute or just the value.
If ipp-attribute-fidelity is true and a printer rejects a value, it is
the same as rejecting the attribute. If ipp-attribute-fidelity is false
and a printer rejects a value, or it a client rejects a value, then it
is as if the attribute didn't have that value. If after rejecting
values, the attribute no longer has any values the attribute is
rejected.
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Note: the intent of the above rule is for servers to be able to
understand text and name values when they don't support the
naturalLanguage override for the value.
The following table specifies the "out-of-band" values for the value-
tag.
Tag Value (Hex) Meaning
0x10 unsupported
0x11 default
0x12 no-value
0x13 compoundValue
0x14-0x1F reserved for future "out-of-band" values.
The "unsupported" value SHALL be used in the attribute-sequence of an
error response for those attributes which the printer does not support.
The "default" value is reserved for future use of setting value back to
their default value. The "no-value" value is used for the "no-value"
value in model, e.g. when a document-attribute is returned as a set of
values and an attribute has no specified value for one or more of the
documents. The "compoundValue" SHALL be used to form a single value
from a collection of values, and its value is the number of members
forming the compound value, excluding the compoundValue. For example, a
text value with a naturalLanguage override consists of 3 "values": a
compoundValue with value 2, a naturalLanguage value and a text value.
The following table specifies the integer values for the value-tag
Tag Value (Hex) Meaning
0x20 reserved
0x21 integer
0x22 boolean
0x23 enum
0x24-0x2F reserved for future integer types
NOTE: 0x20 is reserved for "generic integer" if should ever be needed.
The following table specifies the octetString values for the value-tag
Tag Value (Hex) Meaning
0x30 octetString with an unspecified format
0x31 dateTime
0x32 resolution
0x33 rangeOfInteger
0x34 reserved for dictionary (in the future)
0x35-0x3F reserved for future octetString types
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The following table specifies the character-string values for the value-
tag
Tag Value (Hex) Meaning
0x40 reserved
0x41 text
0x42 name
0x43 reserved
0x44 keyword
0x45 uri
0x46 uriScheme
0x47 charSet
0x48 naturalLanguage
0x49 mediaType
0x4A-0x5F reserved for future character string types
NOTE: 0x40 is reserved for "generic character-string" if should ever be
needed.
The values 0x60-0xFF are reserved for future types. There are no values
allocated for private extensions. A new type must be registered via the
type 2 process.
3.7 Name-Lengths
The name-length field SHALL consist of a SIGNED-SHORT. This field SHALL
specify the number of octets in the name field which follows the name-
length field, excluding the two bytes of the name-length field.
If a name-length field has a value of zero, the following name field
SHALL be empty, and the following value SHALL be treated as an
additional value for the preceding attribute. Within an attribute-
sequence, if two attributes have the same name, the first occurrence
SHALL be ignored. The zero-length name is the only mechanism for multi-
valued attributes.
3.8 Mapping of Attribute Names
Some attributes are encoded in a special position. These attribute are:
. "printer-uri": The target printer-uri of each operation in the IPP
model document SHALL be specified outside of the operation layer
as the request-URI on the Request-Line at the HTTP level.
. "job-uri": The target job-uri of each operation in the IPP model
document SHALL be specified outside of the operation layer as the
request-URI on the Request-Line at the HTTP level.
. "document-content": The attribute named "document-content" in the
IPP model document SHALL become the "data" in the operation layer.
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. "status-code": The attribute named "status-code" in the IPP model
document SHALL become the "status-code" field in the operation
layer response.
The model document arranges the remaining attributes into groups for
each operation request and response. Each such group SHALL be
represented in the protocol by an xxx-attribute-sequence preceded by the
appropriate xxx-attributes-tag (See the table below and Appendix B:
Mapping of Each Operation in the Encoding). In addition, the order of
these xxx-attributes-tags and xxx-attribute-sequences in the protocol
SHALL be the same as in the model document, but the order of attributes
within each xxx-attribute-sequence SHALL be unspecified. The table below
maps the model document group name to xxx-attributes-sequence
Model Document Group xxx-attributes-sequence
Operation Attributes operations-attributes-sequence
Job Template Attributes job-attributes-sequence
Job Object Attributes job-attributes-sequence
Unsupported Attributes unsupported-job-attributes-sequence
Requested Attributes (Get- job-attributes-sequence
Attributes of job object)
Requested Attributes (Get- printer-attributes-sequence
Attributes of printer object)
Document Content in a special position as described above
ISSUE: coordinate this with the model document.
If an operation contains attributes from more than one job object (e.g.
Get-Jobs response), the attributes from each job object SHALL be in a
separate job-attribute-sequence, such that the attributes from the ith
job object are in the ith job-attribute-sequence. See Section 10
"Appendix B: Mapping of Each Operation in the Encoding" for table
showing the application of the rules above.
3.9 Value Lengths
Each attribute value SHALL be preceded by a SIGNED-SHORT which SHALL
specify the number of octets in the value which follows this length,
exclusive of the two bytes specifying the length.
For any of the types represented by binary signed integers, the sender
MUST encode the value in exactly four octets..
For any of the types represented by character-strings, the sender MUST
encode the value with all the characters of the string and without any
padding characters.
If a value-tag contains an "out-of-band" value, such as "unsupported",
the value-length SHALL be 0 and the value empty " the value has no
meaning when the value-tag has an "out-of-band" value. If a printer or
client receives an operation with a nonzero value-length in this case,
it SHALL ignore the value field.
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3.10 Mapping of Attribute Values
The following SHALL be the mapping of attribute values to their IPP
encoding in the value field. The syntax types are defined in the IPP
model document.
Syntax of Encoding
Attribute Value
text an octet string whose charset and language is
that specified within the operation request or
response.
The attributes-charset attribute with a value of
type `charset' MUST be in the operations-
attribute sequence unless the request or response
contains no attributes. It specifies the charset
for all text and name values of attributes.
The attributes-natural-language attribute with a
value of type `naturalLanguage' MUST be in the
operations-attribute sequence unless the request
or response contains no attributes. It specifies
the language for all text and name values of
attributes unless overridden. The language can
be overridden on a per-object or a per-value
basis.
The language can be overridden on a per-object
basis only for a job-sequence within a Get-Jobs
response. If the attributes-natural-language
attribute is present within such a context, it
must have a value of type `naturalLanguage' and
it overrides the language for all text and name
attributes within the job-attributes sequence
containing it, but not for attributes in any
other xxx-attribute-sequence.
The language can be overridden on a per-value
basis by syntactically preceding the text or name
value by two values: a value of type
compoundValue whose value is 2 and a value of
type naturalLanguage whose value is the language
override. From a protocol syntax view, the
compoundValue, the naturalLanguage value and the
text or name value appear as three separate
values of a single attribute, but from a semantic
view, the Printer treats them as a single value
where the naturalLanguage value overrides the
language of the immediately following text or
name value in the attribute. Any text or name
values in the same or other attributes are not
affected by the override. If an attribute
consists of a single text or name value, the
language value turns it into an attribute with
two values from a syntactic view.
The text is encoded in "network byte order" with
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Syntax of Encoding
Attribute Value
the first character in the text (according to
reading order) being the first character in the
encoding.
name same as text
charset an octet string of US-ASCII encoded characters
specified in RFC 2046 [r2046] and contained in
the IANA character-set Registry [iana] according
to the IANA procedures [char].
naturalLanguage an octet string of US-ASCII encoded characters
and with a syntax specified by RFC 1766 [r1766]
mediaType an octet string of US-ASCII encoded characters
defined by RFC 2046 [r2046] and registered
according to the procedures of RFC 2048 [r2048]
for identifying a document format. The value MAY
include a charset parameter, depending on the
specification of the Media Type in the IANA
Registry [iana]. Examples:
keyword an octet string of US-ASCII encoded characters. .
Allowed values are defined in the IPP model
document
uri as specified by RFC 1630 [r1630]
uriScheme same as keyword
boolean one binary octet where 0x00 is `false' and 0x01
is `true'
integer a SIGNED-INTEGER, defined previously as a signed
integer using two's-complement binary encoding in
four octets with big-endian format (also known as
"network order" and "most significant byte
first").
enum same as integer. Allowed integer values are
defined in the IPP model document
compoundValue has the same representation as an integer, but
with a different meaning. If the value of a
compoundValue is n, then the n following values
of the attribute form a single value. For
example, if an attribute has 3 successive values:
compoundValue of 2, naturalLanuage of `fr-CA' and
name of `bete', then these three "values" form a
single value which is a name of `bete' in
Canadian French.
dateTime eleven octets whose contents are defined by
"DateAndTime" in RFC 1903 [r1903]. Although RFC
1903 also defines an eight octet format which
omits the time zone, a value of this type in the
IPP protocol MUST use the eleven octet format.
resolution nine octets consisting of 2 SIGNED-INTEGERs
followed by a SIGNED-BYTE. The values are the
same as those specified in RFC 1759 (Printer MIB)
[r1759]. The first SIGNED-INTEGER contains the
value of prtMarkerAddressabilityXFeedDir. The
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Syntax of Encoding
Attribute Value
second SIGNED-INTEGER contains the value of
prtMarkerAddressabilityFeedDir. The SIGNED-BYTE
contains the value of
prtMarkerAddressabilityUnit. Note: the latter
value is either 3 (tenThousandsOfInches) or 4
(micrometers) and the addressability is in 10,000
units of measure. Thus the SIGNED-INTEGERS
represent integral values in either dots-per-inch
or dots-per-centimeter.
rangeOf integer Eight octets consisting of 2 SIGNED-INTEGERs. The
first SIGNED-INTEGERs contains the lowest value
of the range and the second SIGNED-INTEGERs
contains the highest value of the range
1setOf X encoding according to the rules for an attribute
with more than more value. Each value X is
encoded according to the rules for encoding its
type.
The type of the value in the model document determines the encoding in
the value and the value of the value-tag.
3.11 Data
The data part SHALL include any data required by the operation
4. Encoding of Transport Layer
HTTP/1.1 shall be the transport layer for this protocol.
The operation layer has been designed with the assumption that the
transport layer contains the following information:
. the URI of the target job or printer operation
. the total length of the data in the operation layer, either as a
single length or as a sequence of chunks each with a length.
It is REQUIRED that a printer support HTTP over port 80, though a
printer may support HTTP over port 516 or some other port. In addition,
a printer may have to support another port for secure connections.
Note: Consistent with RFC 2068 (HTTP/1.1), HTTP URI's for IPP implicitly
reference port 80. If a URI references some other port, the port number
must be explicitly specified in the URI.
Each HTTP operation shall use the POST method where the request-URI is
the object target of the operation, and where the "Content-Type" of the
message-body in each request and response shall be "application/ipp".
The message-body shall contain the operation layer and shall have the
syntax described in section 3.2 "Syntax of Encoding". A client
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implementation SHALL adhere to the rules for a client described in RFC
2068 [r2068]. A printer (server) implementation SHALL adhere the rules
for an origin server described in RFC 2068.In the following sections,
there are a tables of all HTTP headers which describe their use in an
IPP client or server. The following is an explanation of each column in
these tables.
. the "header" column contains the name of a header
. the "request/client" column indicates whether a client sends the
header.
. the "request/ server" column indicates whether a server supports
the header when received.
. the "response/ server" column indicates whether a server sends the
header.
. the "response /client" column indicates whether a client supports
the header when received.
. the "values and conditions" column specifies the allowed header
values and the conditions for the header to be present in a
request/response.
The table for "request headers" does not have columns for responses, and
the table for "response headers" does not have columns for requests.
The following is an explanation of the values in the "request/client"
and "response/ server" columns.
. must: the client or server MUST send the header,
. must-if: the client or server MUST send the header when the
condition described in the "values and conditions" column is met,
. may: the client or server MAY send the header
. not: the client or server SHOULD NOT send the header. It is not
relevant to an IPP implementation.
The following is an explanation of the values in the "response/client"
and "request/ server" columns.
. must: the client or server MUST support the header,
. may: the client or server MAY support the header
. not: the client or server SHOULD NOT support the header. It is not
relevant to an IPP implementation.
4.1 General Headers
The following is a table for the general headers.
ISSUE: an HTTP expert should review these tables for accuracy.
General- Request Response Values and Conditions
Header
Client Server Server Client
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General- Request Response Values and Conditions
Header
Client Server Server Client
Cache- must not must not "no-cache" only
Control
Connection must-if must must- must "close" only. Both
if client and server
SHOULD keep a
connection for the
duration of a sequence
of operations. The
client and server MUST
include this header
for the last operation
in such a sequence.
Date may may must may per RFC 1123 [r1123]
Pragma` must not must not "no-cache" only
Transfer- must-if must must- must "chunked" only .
Encoding if Header MUST be present
if Content-Length is
absent.
Upgrade not not not not
Via not not not not
4.2 Request Headers
The following is a table for the request headers.
Request-Header Client Server Request Values and Conditions
Accept may must "application/ipp" only. This
value is the default if the
client omits it
Accept-Charset not not Charset information is within
the application/ipp entity
Accept-Encoding may must empty and per RFC 2068 [r2068]
and IANA registry for content-
codings
Accept-Language not not . language information is within
the application/ipp entity
Authorization must-if must per RFC 2068. A client MUST send
this header when it receives a
401 "Unauthorized" response and
does not receive a "Proxy-
Authenticate" header.
From not not per RFC 2068. Because RFC
recommends sending this header
only with the user's approval, it
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Request-Header Client Server Request Values and Conditions
is not very useful
Host must must per RFC 2068
If-Match not not
If-Modified- not not
Since
If-None-Match not not
If-Range not not
If-Unmodified- not not
Since
Max-Forwards not not
Proxy- must-if not per RFC 2068. A client MUST send
Authorization this header when it receives a
401 "Unauthorized" response and a
"Proxy-Authenticate" header.
Range not not
Referer not not
User-Agent not not
4.3 Response Headers
The following is a table for the request headers.
Response- Server Client Response Values and Conditions
Header
Accept-Ranges not not
Age not not
Location must-if may per RFC 2068. When URI needs
redirection.
Proxy- not must per RFC 2068
Authenticate
Public may may per RFC 2068
Retry-After may may per RFC 2068
Server not not
Vary not not
Warning may may per RFC 2068
WWW- must-if must per RFC 2068. When a server needs to
Authenticate authenticate a client.
4.4 Entity Headers
The following is a table for the entity headers.
Entity-Header Request Response Values and Conditions
Client Server Server Client
Allow not not not not
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Entity-Header Request Response Values and Conditions
Client Server Server Client
Content-Base not not not not
Content- may must must must per RFC 2068 and IANA
Encoding registry for content
codings.
Content- not not not not Application/ipp
Language handles language
Content- must-if must must-if must the length of the
Length message-body per RFC
2068. Header MUST be
present if Transfer-
Encoding is absent..
Content- not not not not
Location
Content-MD5 may may may may per RFC 2068
Content-Range not not not not
Content-Type must must must must "application/ipp"
only
ETag not not not not
Expires not not not not
Last-Modified not not not not
5. Security Considerations
When utilizing HTTP 1.1 as a transport of IPP, the security
considerations outlined in RFC 2068 [r2068] apply. Specifically, IPP
servers can generate a 401 "Unauthorized" response code to request
client authentication and IPP clients should correctly respond with the
proper "Authorization" header. Both Basic Authentication (RFC 2068) and
Digest Authentication (RFC 2069) [r2069] flavors of authentication SHALL
be supported. The server chooses which type(s) of authentication to
accept. Digest Authentication is a more secure method, and is always
preferred to Basic Authentication.
For secure communication (privacy in particular), IPP SHOULD be run
using a secure communications channel. For this purpose it is the
intention to define standardization of IPP in combination with Transport
Layer Security (TLS), currently under development in the IETF, when the
TLS specifications are agreed and on the IETF standards track.
As an intercept solution for secure communication, the Secure Socket
Layer 3.0 (SSL3) could be used, but be warned that such implementations
may not be able to interoperate with a future standardized IPP and TLS
solution. Appendix C gives some hints to implementors wanting to use
SSL3 as intercept solution.
It is possible to combine the techniques, HTTP 1.1 client authentication
(either basic or digest) with a secure communications channel. Together
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the two are more secure than client authentication and they perform user
authentication.
See further discussion of IPP security concepts in the model document
[ipp-m].
6. References
[822] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", RFC 822, August 1982.
[r1123] Braden, S., "Requirements for Internet Hosts - Application and
Support", RFC 1123, October, 1989,
[r1179] McLaughlin, L. III, (editor), "Line Printer Daemon Protocol"
RFC 1179, August 1990.
[r1630] T. Berners-Lee, "Universal Resource Identifiers in WWW: A
Unifying Syntax for the Expression of Names and Addresses of
Objects on the Network as used in the Word-Wide Web", RFC 1630,
June 1994.
[r1759] Smith, R., Wright, F., Hastings, T., Zilles, S., and
Gyllenskog, J., "Printer MIB", RFC 1759, March 1995.
[r1738] Berners-Lee, T., Masinter, L., McCahill, M. , "Uniform
Resource Locators (URL)", RFC 1738, December, 1994.
[r1543] Postel, J., "Instructions to RFC Authors", RFC 1543, October
1993.
[r1766] H. Alvestrand, " Tags for the Identification of Languages",
RFC 1766, March 1995.
[r1903} J. Case, et al. "Textual Conventions for Version 2 of the
Simple Network Managment Protocol (SNMPv2)", RFC 1903, January
1996.
[r2046] N. Freed & N. Borenstein, Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types. November 1996. (Obsoletes
RFC1521, RFC1522, RFC1590), RFC 2046.
[r2048] N. Freed, J. Klensin & J. Postel. Multipurpose Internet Mail
Extension (MIME) Part Four: Registration Procedures. November 1996.
(Format: TXT=45033 bytes) (Obsoletes RFC1521, RFC1522, RFC1590)
(Also BCP0013), RFC 2048.
[r2068] R Fielding, et al, "Hypertext Transfer Protocol " HTTP/1.1"
RFC 2068, January 1997
[r2069] J. Franks, et al, "An Extension to HTTP: Digest Access
Authentication" RFC 2069, January 1997
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[r2119] S. Bradner, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119 , March 1997
[r2184] N. Freed, K. Moore, "MIME Parameter Value and Encoded Word
Extensions: Character Sets, Languages, and Continuations", RFC
2184, August 1997,
[abnf] D. Crocker et al., "Augmented BNF for Syntax Specifications:
ABNF", draft-ietf-drums-abnf-04.txt.
[char] N. Freed, J. Postel: IANA CharSet Registration Procedures,
Work in Progress (draft-freed-charset-reg-02.txt).
[dpa] ISO/IEC 10175 Document Printing Application (DPA), June 1996.
[iana] IANA Registry of Coded Character Sets: ftp://ftp.isi.edu/in-
notes/iana/assignments/character-sets
[ipp-r] Wright, F. D., "Requirements for an Internet Printing
Protocol:"
[ipp-m] Isaacson, S, deBry, R, Hasting, T, Herriot, R, Powell, P,
"Internet Printing Protocol/1.0: Model and Semantics"
[ssl] Netscape, The SSL Protocol, Version 3, (Text version 3.02)
November 1996.
7. Author's Address
Robert Herriot (editor) Paul Moore
Sun Microsystems Inc. Microsoft
901 San Antonio.Road, MPK-17 One Microsoft Way
Palo Alto, CA 94303 Redmond, WA 98053
Phone: 650-786-8995 Phone: 425-936-0908
Fax: 650-786-7077 Fax: 425-93MS-FAX
Email: robert.herriot@eng.sun.com Email: paulmo@microsoft.com
Sylvan Butler Randy Turner
Hewlett-Packard Sharp Laboratories
11311 Chinden Blvd. 5750 NW Pacific Rim Blvd
Boise, ID 83714 Camas, WA 98607
Phone: 208-396-6000 Phone: 360-817-8456
Fax: 208-396-3457 Fax: : 360-817-8436
Email: sbutler@boi.hp.com Email: rturner@sharplabs.com
IPP Mailing List: ipp@pwg.org
IPP Mailing List Subscription: ipp-request@pwg.org
IPP Web Page: http://www.pwg.org/ipp/
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8. Other Participants:
Chuck Adams - Tektronix Harry Lewis - IBM
Ron Bergman - Data Products Tony Liao - Vivid Image
Keith Carter - IBM David Manchala - Xerox
Angelo Caruso - Xerox Carl-Uno Manros - Xerox
Jeff Copeland - QMS Jay Martin - Underscore
Roger Debry - IBM Larry Masinter - Xerox
Lee Farrell - Canon Bob Pentecost - Hewlett-Packard
Sue Gleeson - Digital Patrick Powell - SDSU
Charles Gordon - Osicom Jeff Rackowitz - Intermec
Brian Grimshaw - Apple Xavier Riley - Xerox
Jerry Hadsell - IBM Gary Roberts - Ricoh
Richard Hart - Digital Stuart Rowley - Kyocera
Tom Hastings - Xerox Richard Schneider - Epson
Stephen Holmstead Shigern Ueda - Canon
Zhi-Hong Huang - Zenographics Bob Von Andel - Allegro Software
Scott Isaacson - Novell William Wagner - Digital Products
Rich Lomicka - Digital Jasper Wong - Xionics
David Kellerman - Northlake Don Wright - Lexmark
Software
Robert Kline - TrueSpectra Rick Yardumian - Xerox
Dave Kuntz - Hewlett-Packard Lloyd Young - Lexmark
Takami Kurono - Brother Peter Zehler - Xerox
Rich Landau - Digital Frank Zhao - Panasonic
Greg LeClair - Epson Steve Zilles - Adobe
9. Appendix A: Protocol Examples
9.1 Print-Job Request
The following is an example of a Print-Job request with job-name,
copies, and sides specified.
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x0002 PrintJob operation
0x01 start operation- operation-attributes tag
attributes
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0008 value-length
US-ASCII US-ASCII value
0x48 natural-language value-tag
type
0x001B name-length
attributes-natural- attributes-natural- name
language language
0x0005 value-length
en-US en-US value
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Octets Symbolic Value Protocol field
0x42 name type value-tag
0x0008 name-length
job-name job-name name
0x0006 value-length
foobar foobar value
0x02 start job- job-attributes tag
attributes
0x21 integer type value-tag
0x0005 name-length
copies copies name
0x0004 value-length
0x00000014 20 value
0x44 keyword type value-tag
0x0005 name-length
sides sides name
0x0013 value-length
two-sided-long-edge two-sided-long-edge value
0x03 start-data data-tag
%!PS... <PostScript> data
9.2 Print-Job Response (successful)
Here is an example of a Print-Job response which is successful:
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x0000 OK (successful) status-code
0x01 start operation- operation-attributes tag
attributes
0x47 charset type value-tag
0x0012 name-length
attributes- attributes- name
charset charset
0x0008 value-length
US-ASCII US-ASCII value
0x48 natural-language value-tag
type
0x001B name-length
attributes- attributes- name
natural- natural-language
language
0x0005 value-length
en-US en-US value
0x41 text type value-tag
0x000E name-length
status-message status-message name
0x0002 value-length
OK OK value
0x02 start job- job-attributes tag
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Octets Symbolic Value Protocol field
attributes
0x21 integer value-tag
0x0007 name-length
job-id job-id name
0x0004 value-length
147 147 value
0x45 uri type value-tag
0x0008 name-length
job-uri job-uri name
0x000E value-length
http://foo/123 http://foo/123 value
0x25 name type value-tag
0x0008 name-length
job-state job-state name
0x0001 value-length
0x03 pending value
0x03 start-data data-tag
9.3 Print-Job Response (failure)
Here is an example of a Print-Job response which fails because the
printer does not support sides and because the value 20 for copies is
not supported:
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x0400 client-error-bad-request status-code
0x01 start operation- operation-attribute tag
attribures
0x47 charset type value-tag
0x0012 name-length
attributes- attributes-charset name
charset
0x0008 value-length
US-ASCII US-ASCII value
0x48 natural-language type value-tag
0x001B name-length
attributes- attributes-natural- name
natural- language
language
0x0005 value-length
en-US en-US value
0x41 text type value-tag
0x000E name-length
status-message status-message name
0x000D value-length
bad-request bad-request value
0x04 start unsupported-job- unsupported-job-
attributes attributes tag
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Octets Symbolic Value Protocol field
0x21 integer type value-tag
0x0005 name-length
copies copies name
0x0004 value-length
0x00000014 20 value
0x10 unsupported (type) value-tag
0x0005 name-length
sides sides name
0x0000 value-length
0x03 start-data data-tag
9.4 Print-URI Request
The following is an example of Print-URI request with copies and job-
name parameters.
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x0003 Print-URI operation
0x01 start operation- operation-attributes tag
attributes
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0008 value-length
US-ASCII US-ASCII value
0x48 natural-language value-tag
type
0x001B name-length
attributes-natural- attributes- name
language natural-language
0x0005 value-length
en-US en-US value
0x45 uri type value-tag
0x000A name-length
document-uri document-uri name
0x11 value-length
ftp://foo.com/foo ftp://foo.com/foo value
0x42 name type value-tag
0x0008 name-length
job-name job-name name
0x0006 value-length
foobar foobar value
0x02 start job- job-attributes tag
attributes
0x21 integer type value-tag
0x0005 name-length
copies copies name
0x0004 value-length
0x00000001 1 value
0x03 start-data data-tag
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Octets Symbolic Value Protocol field
%!PS... <PostScript> data
9.5 Create-Job Request
The following is an example of Create-Job request with no parameters and
no attributes
Octets Symbolic Protocol field
Value
0x0100 1.0 version
0x0005 Create-Job operation
0x03 start-data data-tag
9.6 Get-Jobs Request
The following is an example of Get-Jobs request with parameters but no
attributes.
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x000A Get-Jobs operation
0x01 start operation- operation-attributes-
attributes tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0008 value-length
US-ASCII US-ASCII value
0x48 natural-language value-tag
type
0x001B name-length
attributes-natural- attributes-natural- name
language language
0x0005 value-length
en-US en-US value
0x21 integer type value-tag
0x0005 name-length
limit limit name
0x0004 value-length
0x00000032 50 value
0x44 keyword type value-tag
0x0014 name-length
requested-attributes requested-attributes name
0x0006 value-length
job-id job-id value
0x44 keyword type value-tag
0x0000 additional value name-length
0x0008 value-length
job-name job-name value
0x03 start-data data-tag
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9.7 Get-Jobs Response
The following is an of Get-Jobs response from previous request with 3
jobs. The Printer returns no information about the second job.
Octets Symbolic Value Protocol field
0x0100 1.0 version
0x0000 OK (successful) status-code
0x01 start operation- operation-attribute-tag
attributes
0x47 charset type value-tag
0x0012 name-length
attributes- attributes-charset name
charset
0x0008 value-length
ISO-8859-1 ISO-8859-1 value
0x48 natural-language value-tag
type
0x001B name-length
attributes- attributes-natural- name
natural-language language
0x0005 value-length
en-US en-US value
0x41 text type value-tag
0x000E name-length
status-message status-message name
0x0002 value-length
OK OK value
0x02 start job-attributes job-attributes-tag
(1st object)
0x48 natural-language value-tag
type
0x001B name-length
attributes- attributes-natural- name
natural-language language
0x0005 value-length
fr-CA fr-CA value
0x21 integer type value-tag
0x0006 name-length
job-id job-id name
0x0004 value-length
147 147 value
0x42 name type value-tag
0x0008 name-length
job-name job-name name
0x0003 name-length
fou fou name
0x02 start job-attributes job-attributes-tag
(2nd object)
0x02 start job-attributes job-attributes-tag
(3rd object)
0x21 interger type value-tag
0x0006 name-length
job-id job-id name
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Octets Symbolic Value Protocol field
0x0004 value-length
148 148 value
0x13 compoundValue value-tag
0x0008 name-length
job-name job-name name
0x0004 value-length
0x0002 2 value (number of values)
0x48 naturalLanguage value-tag
0x0000 muli-value marker name-length
0x0005 value-length
de-CH de-CH value
0x42 name type value-tag
0x0000 muli-value marker name-length
0x0003 name-length
bar bar name
0x03 start-data data-tag
10. Appendix B: Mapping of Each Operation in the Encoding
The next three tables show the results of applying the rules above to
the operations defined in the IPP model document. There is no
information in these tables that cannot be derived from the rules
presented in Section 3.8 "Mapping of Attribute Names".
The following table shows the mapping of all IPP model-document request
attributes to an appropriate xxx-attribute-sequence or special position
in the protocol.
The table below shows the attributes for operations sent to a Printer
URI.
Operation operation job attributes special position
attributes
Print-Job attributes- job-template document-content
charset attributes
attributes-
natural-
language
job-name
document-name
ipp-attribute-
fidelity
document-
charset
document-
natural-
language
Create-Job or attributes- job-template
Validate-Job charset attributes
attributes-
natural-
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Operation operation job attributes special position
attributes
language job-
name
ipp-attribute-
fidelity
Print-URI attributes- job-template
charset attributes
attributes-
natural-
language job-
name
ipp-attribute-
fidelity
document-uri
document-
charset
document-
natural-
language
Send-Document attributes-
charset
attributes-
natural-
language job-id
last-document
document-name
document-
charset
document-
natural- document-content
language
Send-URI attributes-
charset
attributes-
natural-
language job-id
last-document
document-name
document-uri
document-
charset
document-
natural-
language
Cancel-Job attributes-
charset
attributes-
natural-
language job-id
message
Get-Attributes attributes-
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Operation operation job attributes special position
attributes
(for a Printer) charset
attributes-
natural-
language
requested-
attributes
document-format
Get-Attributes attributes-
(for a Job) charset
attributes-
natural-
language job-id
requested-
attributes
Get-Jobs attributes-
charset
attributes-
natural-
language limit
requested-
attributes
which-jobs
The table below shows the attributes for operations sent to a Job URI.
Operation operation job attributes special position
attributes
Send-Document attributes- document-content
charset
attributes-
natural-
language last-
document
document-name
document-
charset
document-
natural-
language
Send-URI attributes-
charset
attributes-
natural-
language last-
document
document-name
document-uri
document-
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Operation operation job attributes special position
attributes
charset
document-
natural-
language
Cancel-Job attributes-
charset
attributes-
natural-
language
message
Get-Attributes attributes-
(for a Job) charset
attributes-
natural-
language
requested-
attributes
The following two tables shows the mapping of all IPP model-document
response attributes to an appropriate xxx-attribute-sequence or special
position in the protocol.
Operation operation job- unsupported-job- special
attributes attributes attributes position
Print-Job, attributes- job-id unsupported status-
Print-URI, charset job-uri attributes code
Create-Job, attributes- job-state
Send-Document natural- job-state-
or Send-URI language reasons
status- job-state-
message message
number-of-
intervening
-jobs
Validate-Job attributes- unsupported status-
charset attributes code
attributes-
natural-
language
status-
message
Note: the unsupported-job-attributes are present only if the client
included some job attributes that the Printer doesn't support.
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Note: the job-attributes are present only if the server returns the
status code of successful-ok or successful-ok-ignored-or-substituted-
attributes.
Operation operation job- printer- special
attributes attributes attributes position
Cancel-Job attributes-
charset
attributes-
natural-
language
status- status-code
message
Get-Attributes attributes- requested status-code
(of a job) charset attributes
attributes-
natural-
language
status-
message
Get-Attributes attributes- requested status-code
(of a printer) charset attributes
attributes-
natural-
language
status-
message
Get-Jobs attributes- requested status-code
charset attributes
attributes- (see the
natural- Note below)
language
status-
message
Note for Get-Jobs: there is a separate job-attribute-sequence containing
requested-attributes for each job object in the response
11. Appendix C: Hints to implementors using IPP with SSL3
WARNING: Clients and IPP objects using intermediate secure connection
protocol solutions such as IPP in combination with Secure Socket Layer
Version 3 (SSL3), which are developed in advance of IPP and TLS
standardization, might not be interoperable with IPP and TLS standards-
conforming clients and IPP objects.
Herriot, Butler, October 23, 1997, [Page 32]
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An assumption is that the URI for a secure IPP Printer object has been
found by means outside the IPP printing protocol, via a directory
service, web site or other means.
IPP provides a transparent connection to SSL by calling the
corresponding URL (a https URI connects by default to port 443).
However, the following functions can be provided to ease the integration
of IPP with SSL during implementation.
connect (URI), returns a status.
"connect" makes an https call and returns the immediate status of
the connection as returned by SSL to the user. The status values are
explained in section 5.4.2 of the SSL document [ssl].
A session-id may also be retained to later resume a session. The SSL
handshake protocol may also require the cipher specifications
supported by the client, key length of the ciphers, compression
methods, certificates, etc. These should be sent to the server and
hence should be available to the IPP client (although as part of
administration features).
disconnect (session)
to disconnect a particular session.
The session-id available from the "connect" could be used.
resume (session)
to reconnect using a previous session-id.
The availability of this information as administration features are left
for implementors, and need not be standardized at this time
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