Network Working Group R. Herriot, Ed.
Request for Comments: 2565 Xerox Corporation
Category: EXPerimental S. Butler
Hewlett-Packard
P. Moore
Microsoft
R. Turner
Sharp Labs
April 1999
Internet Printing Protocol/1.0: Encoding and Transport
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
IESG Note
This document defines an Experimental protocol for the Internet
community. The IESG expects that a revised version of this protocol
will be published as Proposed Standard protocol. The Proposed
Standard, when published, is expected to change from the protocol
defined in this memo. In particular, it is expected that the
standards-track version of the protocol will incorporate strong
authentication and privacy features, and that an "ipp:" URL type will
be defined which supports those security measures. Other changes to
the protocol are also possible. Implementors are warned that future
versions of this protocol may not interoperate with the version of
IPP defined in this document, or if they do interoperate, that some
protocol features may not be available.
The IESG encourages experimentation with this protocol, especially in
combination with Transport Layer Security (TLS) [RFC2246], to help
determine how TLS may effectively be used as a security layer for
IPP.
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 technologies. This document defines the
rules for encoding IPP operations and IPP attributes into a new
Internet mime media type called "application/ipp". This document
also defines the rules for transporting over HTTP a message body
whose Content-Type is "application/ipp".
The full set of IPP documents includes:
Design Goals for an Internet Printing Protocol [RFC2567]
Rationale for the StrUCture and Model and Protocol for the
Internet Printing Protocol [RFC2568]
Internet Printing Protocol/1.0: Model and Semantics [RFC2566]
Internet Printing Protocol/1.0: Encoding and Transport (this
document)
Internet Printing Protocol/1.0: Implementer"s Guide [ipp-iig]
Mapping between LPD and IPP Protocols [RFC2569]
The document, "Design Goals for an Internet Printing Protocol", 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. It calls out a subset of end user requirements that
are satisfied in IPP/1.0. Operator and administrator requirements are
out of scope for version 1.0.
The document, "Rationale for the Structure and Model and Protocol for
the Internet Printing Protocol", describes IPP from a high level
view, defines a roadmap for the various documents that form the suite
of IPP specifications, and gives background and rationale for the
IETF working group"s major decisions.
The document, "Internet Printing Protocol/1.0: Model and Semantics",
describes a simplified model with abstract objects, their attributes,
and their operations that are independent of encoding and transport.
It introduces a Printer and a Job object. The Job object optionally
supports multiple documents per Job. It also addresses security,
internationalization, and Directory issues.
This document "Internet Printing Protocol/1.0: Implementer"s Guide",
gives advice to implementers of IPP clients and IPP objects.
The document "Mapping between LPD and IPP Protocols" gives some
advice to implementers of gateways between IPP and LPD (Line Printer
Daemon) implementations.
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..........................................7
3.3 Version-number..............................................9
3.4 Operation-id................................................9
3.5 Status-code.................................................9
3.6 Request-id..................................................9
3.7 Tags.......................................................10
3.7.1 Delimiter Tags.........................................10
3.7.2 Value Tags.............................................11
3.8 Name-Length................................................13
3.9 (Attribute) Name...........................................13
3.10 Value Length...............................................16
3.11 (Attribute) Value..........................................16
3.12 Data.......................................................18
4. Encoding of Transport Layer.....................................18
5. Security Considerations.........................................19
5.1 Using IPP with SSL3........................................19
6. References......................................................20
7. Authors" Addresses..............................................22
8. Other Participants:.............................................24
9. Appendix A: Protocol Examples...................................25
9.1 Print-Job Request..........................................25
9.2 Print-Job Response (successful)............................26
9.3 Print-Job Response (failure)...............................27
9.4 Print-Job Response (success with attributes ignored).......28
9.5 Print-URI Request..........................................30
9.6 Create-Job Request.........................................31
9.7 Get-Jobs Request...........................................31
9.8 Get-Jobs Response..........................................32
10. Appendix C: Registration of MIME Media Type Information for
"application/ipp"..............................................35
11. Full Copyright Statement.......................................37
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 [RFC2068] 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" [RFC2566] defines the semantics of such a message body and
the supported values. This document specifies the encoding of an IPP
operation. The aforementioned document [RFC2566] is henceforth
referred to as the "IPP model document"
2. Conformance Terminology
The key Words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC2119 [RFC2119].
3. Encoding of the Operation Layer
The operation layer MUST contain a single operation request or
operation response. Each request or response consists of a sequence
of values and attribute groups. Attribute groups consist of a
sequence of attributes each of which is a name and value. Names and
values are ultimately sequences of octets
The encoding consists of octets as the most primitive type. There are
several types built from octets, but three important types are
integers, character strings and octet strings, on which most other
data types are built. Every character string in this encoding MUST be
a sequence of characters where the characters are associated with
some charset and some natural language. A character string MUST be in
"reading order" with the first character in the value (according to
reading order) being the first character in the encoding. A character
string whose associated charset is US-ASCII whose associated natural
language is US English is henceforth called a US-ASCII-STRING. A
character string whose associated charset and natural language are
specified in a request or response as described in the model document
is henceforth called a LOCALIZED-STRING. An octet string MUST be in
"IPP model document order" with the first octet in the value
(according to the IPP model document order) being the first octet in
the encoding Every integer in this encoding MUST 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 MUST be 1, 2 or 4,
depending on usage in the protocol. Such one-octet integers,
henceforth called SIGNED-BYTE, are used for the version-number and
tag fields. Such two-byte integers, henceforth called SIGNED-SHORT
are used for the operation-id, status-code and length fields. Four
byte integers, henceforth called SIGNED-INTEGER, are used for values
fields and the sequence number.
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 RFC2234 [RFC2234]
3.1 Picture of the Encoding
The encoding for an operation request or response consists of:
-----------------------------------------------
version-number 2 bytes - required
-----------------------------------------------
operation-id (request)
or 2 bytes - required
status-code (response)
-----------------------------------------------
request-id 4 bytes - required
-----------------------------------------------------------
xxx-attributes-tag 1 byte
----------------------------------------------- -0 or more
xxx-attribute-sequence n bytes
-----------------------------------------------------------
end-of-attributes-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. The xxx-attributes-tag and an xxx-attribute-sequence
represent attribute groups in the model document. The xxx-
attributes-tag identifies the attribute group and the xxx-attribute-
sequence contains the attributes.
The expected sequence of xxx-attributes-tag and xxx-attribute-
sequence is specified in the IPP model document for each operation
request and operation response.
A request or response SHOULD contain each xxx-attributes-tag defined
for that request or response even if there are no attributes except
for the unsupported-attributes-tag which SHOULD be present only if
the unsupported-attribute-sequence is non-empty. A receiver of a
request MUST be able to process as equivalent empty attribute groups:
a) an xxx-attributes-tag with an empty xxx-attribute-sequence,
b) an expected but missing xxx-attributes-tag.
The data is omitted from some operations, but the end-of-attributes-
tag is present even when the data is omitted. Note, the xxx-
attributes-tags and end-of-attributes-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 of 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:
-----------------------------------------------
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-number 2 bytes - required
-----------------------------------------------
operation-id (request)
or 2 bytes - required
status-code (response)
-----------------------------------------------
request-id 4 bytes - required
-----------------------------------------------------------
tag (delimiter-tag or value-tag) 1 byte
----------------------------------------------- -0 or more
empty or rest of attribute x bytes
-----------------------------------------------------------
end-of-attributes-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 [RFC2234] except "strings of literals" MUST
be case sensitive. For example "a" means lower case "a" and not
upper case "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-number operation-id request-id
*(xxx-attributes-tag xxx-attribute-sequence)
end-of-attributes-tag data
ipp-response = version-number status-code request-id
*(xxx-attributes-tag xxx-attribute-sequence)
end-of-attributes-tag data
xxx-attribute-sequence = *compound-attribute
xxx-attributes-tag = operation-attributes-tag / job-attributes-tag /
printer-attributes-tag / unsupported-attributes-tag
version-number = major-version-number minor-version-number
major-version-number = SIGNED-BYTE ; initially %d1
minor-version-number = SIGNED-BYTE ; initially %d0
operation-id = SIGNED-SHORT ; mapping from model defined below
status-code = SIGNED-SHORT ; mapping from model defined below
request-id = SIGNED-INTEGER ; whose value is > 0
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-attributes-tag = %x05 ; tag of 5
end-of-attributes-tag = %x03 ; tag of 3
value-tag = %x10-FF
SIGNED-BYTE = BYTE
SIGNED-SHORT = 2BYTE
SIGNED-INTEGER = 4BYTE
DIGIT = %x30-39 ; "0" to "9"
LALPHA = %x61-7A ; "a" to "z"
BYTE = %x00-FF
OCTET-STRING = *BYTE
The syntax allows an xxx-attributes-tag 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-attributes-tag if there are no attributes
(except in the Get-Jobs response just mentioned), the receiver MUST
be able to decode such syntax.
3.3 Version-number
The version-number MUST consist of a major and minor version-number,
each of which MUST be represented by a SIGNED-BYTE. The protocol
described in this document MUST have a major version-number of 1
(0x01) and a minor version-number of 0 (0x00). The ABNF for these
two bytes MUST be %x01.00.
3.4 Operation-id
Operation-ids are defined as enums in the model document. An
operation-ids enum value MUST be encoded as a SIGNED-SHORT.
Note: the values 0x4000 to 0xFFFF are reserved for private
extensions.
3.5 Status-code
Status-codes are defined as enums in the model document. A status-
code enum value MUST be encoded as a SIGNED-SHORT.
The status-code is an operation attribute in the model document. In
the protocol, the status-code is in a special position, outside of
the operation attributes.
If an IPP status-code is returned, then the HTTP Status-Code MUST be
200 (successful-ok). With any other HTTP Status-Code value, the HTTP
response MUST NOT contain an IPP message-body, and thus no IPP
status-code is returned.
3.6 Request-id
The request-id allows a client to match a response with a request.
This mechanism is unnecessary in HTTP, but may be useful when
application/ipp entity bodies are used in another context.
The request-id in a response MUST be the value of the request-id
received in the corresponding request. A client can set the
request-id in each request to a unique value or a constant value,
such as 1, depending on what the client does with the request-id
returned in the response. The value of the request-id MUST be greater
than zero.
3.7 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
3.7.1 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 end-of-attributes-tag
0x04 printer-attributes-tag
0x05 unsupported-attributes-tag
0x06-0x0e reserved for future delimiters
0x0F reserved for future chunking-end-of-attributes-
tag
When an xxx-attributes-tag occurs in the protocol, it MUST mean that
zero or more following attributes up to the next delimiter tag are
attributes belonging to group xxx as defined in the model document,
where xxx is operation, job, printer, unsupported.
Doing substitution for xxx in the above paragraph, this means the
following. When an operation-attributes-tag occurs in the protocol,
it MUST 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 MUST
mean that the zero or more following attributes up to the next
delimiter tag are job attributes or job template attributes as
defined in the model document. When a printer-attributes-tag occurs
in the protocol, it MUST 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-attributes-tag
occurs in the protocol, it MUST mean that the zero or more following
attributes up to the next delimiter tag are unsupported attributes as
defined in the model document.
The operation-attributes-tag and end-of-attributes-tag MUST each
occur exactly once in an operation. The operation-attributes-tag MUST
be the first tag delimiter, and the end-of-attributes-tag MUST be the
last tag delimiter. If the operation has a document-content group,
the document data in that group MUST follow the end-of-attributes-
tag.
Each of the other three xxx-attributes-tags defined above is
OPTIONAL in an operation and each MUST 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 order and presence of delimiter tags for each operation request
and each operation response MUST be that defined in the model
document. For further details, see section 3.9 "(Attribute) Name" and
section 9 "Appendix A: Protocol Examples".
A Printer MUST treat the reserved delimiter tags differently from
reserved value tags so that the Printer knows that there is an entire
attribute group that it doesn"t understand as opposed to a single
value that it doesn"t understand.
3.7.2 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 following table specifies the "out-of-
band" values for the value-tag.
Tag Value (Hex) Meaning
0x10 unsupported
0x11 reserved for future "default"
0x12 unknown
0x13 no-value
Tag Value (Hex) Meaning
0x14-0x1F reserved for future "out-of-band" values.
The "unsupported" value MUST 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 "unknown" value is used for
the value of a supported attribute when its value is temporarily
unknown. The "no-value" value is used for a supported attribute to
which
no value has been assigned, e.g. "job-k-octets-supported" has no
value if an implementation supports this attribute, but an
administrator has not configured the printer to have a limit.
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 it 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 collection (in the future)
0x35 textWithLanguage
0x36 nameWithLanguage
0x37-0x3F reserved for future octetString types
The following table specifies the character-string values for the
value-tag:
Tag Value (Hex) Meaning
0x40 reserved
0x41 textWithoutLanguage
0x42 nameWithoutLanguage
0x43 reserved
0x44 keyword
0x45 uri
0x46 uriScheme
0x47 charset
0x48 naturalLanguage
Tag Value (Hex) Meaning
0x49 mimeMediaType
0x4A-0x5F reserved for future character string types
NOTE: 0x40 is reserved for "generic character-string" if it should
ever be needed.
NOTE: an attribute value always has a type, which is explicitly
specified by its tag; one such tag value is "nameWithoutLanguage".
An attribute"s name has an implicit type, which is keyword.
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 registration process [RFC2566].
The tag 0x7F is reserved for extending types beyond the 255 values
available with a single byte. A tag value of 0x7F MUST signify that
the first 4 bytes of the value field are interpreted as the tag
value. Note, this future extension doesn"t affect parsers that are
unaware of this special tag. The tag is like any other unknown tag,
and the value length specifies the length of a value which contains a
value that the parser treats atomically. All these 4 byte tag values
are currently unallocated except that the values 0x40000000-
0x7FFFFFFF are reserved for experimental use.
3.8 Name-Length
The name-length field MUST consist of a SIGNED-SHORT. This field MUST
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
MUST be empty, and the following value MUST be treated as an
additional value for the preceding attribute. Within an attribute-
sequence, if two attributes have the same name, the first occurrence
MUST be ignored. The zero-length name is the only mechanism for
multi-valued attributes.
3.9 (Attribute) Name
Some operation elements are called parameters in the model document
[RFC2566]. They MUST be encoded in a special position and they MUST
NOT appear as an operation attributes. These parameters are:
- "version-number": The parameter named "version-number" in the
IPP model document MUST become the "version-number" field in the
operation layer request or response.
- "operation-id": The parameter named "operation-id" in the IPP
model document MUST become the "operation-id" field in the
operation layer request.
- "status-code": The parameter named "status-code" in the IPP
model document MUST become the "status-code" field in the
operation layer response.
- "request-id": The parameter named "request-id" in the IPP model
document MUST become the "request-id" field in the operation
layer request or response.
All Printer and Job objects are identified by a Uniform Resource
Identifier (URI) [RFC2396] so that they can be persistently and
unambiguously referenced. The notion of a URI is a useful concept,
however, until the notion of URI is more stable (i.e., defined more
completely and deployed more widely), it is expected that the URIs
used for IPP objects will actually be URLs [RFC1738] [RFC1808].
Since every URL is a specialized form of a URI, even though the more
generic term URI is used throughout the rest of this document, its
usage is intended to cover the more specific notion of URL as well.
Some operation elements are encoded twice, once as the request-URI on
the HTTP Request-Line and a second time as a REQUIRED operation
attribute in the application/ipp entity. These attributes are the
target URI for the operation:
- "printer-uri": When the target is a printer and the transport is
HTTP or HTTPS (for SSL3 [ssl]), the target printer-uri defined
in each operation in the IPP model document MUST be an operation
attribute called "printer-uri" and it MUST also be specified
outside of the operation layer as the request-URI on the
Request-Line at the HTTP level.
- "job-uri": When the target is a job and the transport is HTTP or
HTTPS (for SSL3), the target job-uri of each operation in the
IPP model document MUST be an operation attribute called "job-
uri" and it MUST also be specified outside of the operation
layer as the request-URI on the Request-Line at the HTTP level.
Note: The target URI is included twice in an operation referencing
the same IPP object, but the two URIs NEED NOT be literally
identical. One can be a relative URI and the other can be an absolute
URI. HTTP/1.1 allows clients to generate and send a relative URI
rather than an absolute URI. A relative URI identifies a resource
with the scope of the HTTP server, but does not include scheme, host
or port. The following statements characterize how URLs should be
used in the mapping of IPP onto HTTP/1.1:
1. Although potentially redundant, a client MUST supply the target
of the operation both as an operation attribute and as a URI at
the HTTP layer. The rationale for this decision is to maintain
a consistent set of rules for mapping application/ipp to
possibly many communication layers, even where URLs are not
used as the addressing mechanism in the transport layer.
2. Even though these two URLs might not be literally identical
(one being relative and the other being absolute), they MUST
both reference the same IPP object.
3. The URI in the HTTP layer is either relative or absolute and is
used by the HTTP server to route the HTTP request to the
correct resource relative to that HTTP server. The HTTP server
need not be aware of the URI within the operation request.
4. Once the HTTP server resource begins to process the HTTP
request, it might get the reference to the appropriate IPP
Printer object from either the HTTP URI (using to the context
of the HTTP server for relative URLs) or from the URI within
the operation request; the choice is up to the implementation.
5. HTTP URIs can be relative or absolute, but the target URI in
the operation MUST be an absolute URI.
The model document arranges the remaining attributes into groups for
each operation request and response. Each such group MUST be
represented in the protocol by an xxx-attribute-sequence preceded by
the appropriate xxx-attributes-tag (See the table below and section 9
"Appendix A: Protocol Examples"). In addition, the order of these
xxx-attributes-tags and xxx-attribute-sequences in the protocol MUST
be the same as in the model document, but the order of attributes
within each xxx-attribute-sequence MUST 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-attributes-sequence
Requested Attributes job-attributes-sequence
Get-Job-Attributes)
Requested Attributes printer-attributes-sequence
Get-Printer-Attributes)
Document Content in a special position as described
above
If an operation contains attributes from more than one job object
(e.g. Get-Jobs response), the attributes from each job object MUST
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 9 "Appendix A: Protocol Examples" for table showing the
application of the rules above.
3.10 Value Length
Each attribute value MUST be preceded by a SIGNED-SHORT, which MUST
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 MUST be 0 and the value empty. The
value has no meaning when the value-tag has an "out-of-band" value.
If a client receives a response with a nonzero value-length in this
case, it MUST ignore the value field. If a printer receives a request
with a nonzero value-length in this case, it MUST reject the request.
3.11 (Attribute) Value
The syntax types and most of the details of their representation are
defined in the IPP model document. The table below augments the
information in the model document, and defines the syntax types from
the model document in terms of the 5 basic types defined in section 3
"Encoding of the Operation Layer". The 5 types are US-ASCII-STRING,
LOCALIZED-STRING, SIGNED-INTEGER, SIGNED-SHORT, SIGNED-BYTE, and
OCTET-STRING.
Syntax of Attribute Encoding
Value
textWithoutLanguage, LOCALIZED-STRING.
nameWithoutLanguage
textWithLanguage OCTET_STRING consisting of 4 fields:
a) a SIGNED-SHORT which is the number of octets
in the following field
b) a value of type natural-language,
c) a SIGNED-SHORT which is the number of octets
in the following field,
d) a value of type textWithoutLanguage.
The length of a textWithLanguage value MUST be 4
+ the value of field a + the value of field c.
nameWithLanguage OCTET_STRING consisting of 4 fields:
a) a SIGNED-SHORT which is the number of octets
in the following field
b) a value of type natural-language,
c) a SIGNED-SHORT which is the number of octets
in the following field
d) a value of type nameWithoutLanguage.
The length of a nameWithLanguage value MUST be 4
+ the value of field a + the value of field c.
charset, US-ASCII-STRING.
naturalLanguage,
mimeMediaType,
keyword, uri, and
uriScheme
boolean SIGNED-BYTE where 0x00 is "false" and 0x01 is
"true".
Syntax of Attribute Encoding
Value
integer and enum a SIGNED-INTEGER.
dateTime OCTET-STRING consisting of eleven octets whose
contents are defined by "DateAndTime" in RFC
2579 [RFC2579].
resolution OCTET_STRING consisting of nine octets of 2
SIGNED-INTEGERs followed by a SIGNED-BYTE. The
first SIGNED-INTEGER contains the value of cross
feed direction resolution. The second SIGNED-
INTEGER contains the value of feed direction
resolution. The SIGNED-BYTE contains the units
value.
rangeOfInteger Eight octets consisting of 2 SIGNED-INTEGERs.
The first SIGNED-INTEGER contains the lower
bound and the second SIGNED-INTEGER contains the
upper bound.
1setOf X Encoding according to the rules for an attribute
with more than 1 value. Each value X is encoded
according to the rules for encoding its type.
octetString OCTET-STRING
The type of the value in the model document determines the encoding
in the value and the value of the value-tag.
3.12 Data
The data part MUST include any data required by the operation
4. Encoding of Transport Layer
HTTP/1.1 [RFC2068] is 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 implementation support HTTP over the
IANA assigned Well Known Port 631 (the IPP default port), though a
printer implementation may support HTTP over some other port as well.
In addition, a printer may have to support another port for privacy
(See Section 5 "Security Considerations").
Note: even though port 631 is the IPP default, port 80 remains the
default for an HTTP URI. Thus a URI for a printer using port 631
MUST contain an explicit port, e.g. "http://forest:631/pinetree". An
HTTP URI for IPP with no explicit port implicitly reference port 80,
which is consistent with the rules for HTTP/1.1. Each HTTP operation
MUST 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 MUST be "application/ipp". The message-body
MUST contain the operation layer and MUST have the syntax described
in section 3.2 "Syntax of Encoding". A client implementation MUST
adhere to the rules for a client described for HTTP1.1 [RFC2068]. A
printer (server) implementation MUST adhere the rules for an origin
server described for HTTP1.1 [RFC2068].
An IPP server sends a response for each request that it receives. If
an IPP server detects an error, it MAY send a response before it has
read the entire request. If the HTTP layer of the IPP server
completes processing the HTTP headers successfully, it MAY send an
intermediate response, such as "100 Continue", with no IPP data
before sending the IPP response. A client MUST expect such a variety
of responses from an IPP server. For further information on HTTP/1.1,
consult the HTTP documents [RFC2068].
5. Security Considerations
The IPP Model document defines an IPP implementation with "privacy"
as one that implements Secure Socket Layer Version 3 (SSL3). Note:
SSL3 is not an IETF standards track specification. SSL3 meets the
requirements for IPP security with regards to features such as mutual
authentication and privacy (via encryption). The IPP Model document
also outlines IPP-specific security considerations and should be the
primary reference for security implications with regards to the IPP
protocol itself.
The IPP Model document defines an IPP implementation with
"authentication" as one that implements the standard way for
transporting IPP messages within HTTP 1.1. These include the security
considerations outlined in the HTTP 1.1 standard document [RFC2068]
and Digest Access Authentication extension [RFC2069].
The current HTTP infrastructure supports HTTP over TCP port 80. IPP
server implementations MUST offer IPP services using HTTP over the
IANA assigned Well Known Port 631 (the IPP default port). IPP server
implementations may support other ports, in addition to this port.
See further discussion of IPP security concepts in the model document
[RFC2566].
5.1 Using IPP with SSL3
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 implementers, and need not be specified at this time.
6. References
[RFC2278] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC2278, January 1998.
[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-iig] Hastings, Tom, et al., "Internet Printing Protocol/1.0:
Implementer"s Guide", Work in Progress.
[RFC2569] Herriot, R., Hastings, T., Jacobs, N. and J. Martin,
"Mapping between LPD and IPP Protocols", RFC2569, April
1999.
[RFC2566] deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P.
Powell, "Internet Printing Protocol/1.0: Model and
Semantics", RFC2566, April 1999.
[RFC2565] Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet
Printing Protocol/1.0: Encoding and Transport", RFC2565,
April 1999.
[RFC2568] Zilles, S., "Rationale for the Structure and Model and
Protocol for the Internet Printing Protocol", RFC2568,
April 1999.
[RFC2567] Wright, D., "Design Goals for an Internet Printing
Protocol", RFC2567, April 1999.
[RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC822, August 1982.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC1123, October 1989.
[RFC1179] McLaughlin, L. III, (editor), "Line Printer Daemon
Protocol" RFC1179, August 1990.
[RFC2223] Postel, J. and J. Reynolds, "Instructions to RFCAuthors",
RFC2223, October 1997.
[RFC1738] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
Resource Locators (URL)", RFC1738, December 1994.
[RFC1759] Smith, R., Wright, F., Hastings, T., Zilles, S. and J.
Gyllenskog, "Printer MIB", RFC1759, March 1995.
[RFC1766] Alvestrand, H., " Tags for the Identification of
Languages", RFC1766, March 1995.
[RFC1808] Fielding, R., "Relative Uniform Resource Locators", RFC
1808, June 1995.
[RFC2579] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Textual
Conventions for SMIv2", STD 58, RFC2579, April 1999.
[RFC2046] Freed, N. and N. Borenstein, Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC2046,
November 1996.
[RFC2048] Freed, N., Klensin J. and J. Postel. Multipurpose Internet
Mail Extension (MIME) Part Four: Registration Procedures",
BCP 13, RFC2048, November 1996.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC
2068, January 1997.
[RFC2069] Franks, J., Hallam-Baker, P., Hostetler, J., Leach, P.,
Luotonen, A., Sink, E. and L. Stewart, "An Extension to
HTTP: Digest Access Authentication", RFC2069, January
1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC2119, March 1997.
[RFC2184] Freed, N. and K. Moore, "MIME Parameter Value and Encoded
Word Extensions: Character Sets, Languages, and
Continuations", RFC2184, August 1997.
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC2234. November 1997.
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC2396,
August 1998.
7. Authors" Addresses
Robert Herriot (Editor)
Xerox Corporation
3400 Hillview Ave., Bldg #1
Palo Alto, CA 94304
Phone: 650-813-7696
Fax: 650-813-6860
EMail: rherriot@pahv.xerox.com
Sylvan Butler
Hewlett-Packard
11311 Chinden Blvd.
Boise, ID 83714
Phone: 208-396-6000
Fax: 208-396-3457
EMail: sbutler@boi.hp.com
Paul Moore
Microsoft
One Microsoft Way
Redmond, WA 98053
Phone: 425-936-0908
Fax: 425-93MS-FAX
EMail: paulmo@microsoft.com
Randy Turner
Sharp Laboratories
5750 NW Pacific Rim Blvd
Camas, WA 98607
Phone: 360-817-8456
Fax: 360-817-8436
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/
8. Other Participants:
Chuck Adams - Tektronix Harry Lewis - IBM
Ron Bergman - Dataproducts 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 Ira McDonald - High North Inc.
Sue Gleeson - Digital Bob Pentecost - Hewlett-Packard
Charles Gordon - Osicom Patrick Powell - Astart
Technologies
Brian Grimshaw - Apple Jeff Rackowitz - Intermec
Jerry Hadsell - IBM Xavier Riley - Xerox
Richard Hart - Digital Gary Roberts - Ricoh
Tom Hastings - Xerox Stuart Rowley - Kyocera
Stephen Holmstead Richard Schneider - Epson
Zhi-Hong Huang - Zenographics Shigern Ueda - Canon
Scott Isaacson - Novell Bob Von Andel - Allegro Software
Rich Lomicka - Digital William Wagner - Digital Products
David Kellerman - Northlake Jasper Wong - Xionics
Software
Robert Kline - TrueSpectra Don Wright - Lexmark
Dave Kuntz - Hewlett-Packard Rick Yardumian - Xerox
Takami Kurono - Brother Lloyd Young - Lexmark
Rich Landau - Digital Peter Zehler - Xerox
Greg LeClair - Epson Frank Zhao - Panasonic
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. The "ipp-attribute-fidelity" attribute
is set to "true" so that the print request will fail if the "copies"
or the "sides" attribute are not supported or their values are not
supported.
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x0002 Print-Job operation-id
0x00000001 1 request-id
0x01 start operation-attributes operation-attributes-tag
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-language name
natural-
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000B name-length
printer-uri printer-uri name
0x001A value-length
http://forest: printer pinetree value
631/pinetree
0x42 nameWithoutLanguage type value-tag
0x0008 name-length
job-name job-name name
0x0006 value-length
Foobar foobar value
0x22 boolean type value-tag
0x16 name-length
ipp-attribute- ipp-attribute-fidelity name
fidelity
0x01 value-length
0x01 true value
0x02 start job-attributes job-attributes-tag
0x21 integer type value-tag
0x0006 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- two-sided-long-edge value
long-edge
0x03 end-of-attributes end-of-attributes-tag
%!PS... <PostScript> data
9.2 Print-Job Response (successful)
Here is an example of a successful Print-Job response to the previous
Print-Job request. The printer supported the "copies" and "sides"
attributes and their supplied values. The status code returned is "
successful-ok".
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x0000 successful-ok status-code
0x00000001 1 request-id
0x01 start operation-attributes operation-attributes-tag
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 textWithoutLanguage type value-tag
0x000E name-length
status-message status-message name
0x000D value-length
successful-ok successful-ok value
0x02 start job-attributes job-attributes-tag
0x21 integer value-tag
0x0006 name-length
Octets Symbolic Value Protocol field
job-id job-id name
0x0004 value-length
147 147 value
0x45 uri type value-tag
0x0007 name-length
job-uri job-uri name
0x001E value-length
http://forest:63 job 123 on pinetree value
1/pinetree/123
0x42 nameWithoutLanguage type value-tag
0x0009 name-length
job-state job-state name
0x0004 value-length
0x0003 pending value
0x03 end-of-attributes end-of-attributes-tag
9.3 Print-Job Response (failure)
Here is an example of an unsuccessful Print-Job response to the
previous Print-Job request. It fails because, in this case, the
printer does not support the "sides" attribute and because the value
"20" for the "copies" attribute is not supported. Therefore, no job
is created, and neither a "job-id" nor a "job-uri" operation
attribute is returned. The error code returned is "client-error-
attributes-or-values-not-supported" (0x040B).
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x040B client-error-attributes-or- status-code
values-not-supported
0x00000001 1 request-id
0x01 start operation-attributes operation-attribute tag
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-language name
natural-
language
0x0005 value-length
Octets Symbolic Value Protocol field
en-us en-US value
0x41 textWithoutLanguage type value-tag
0x000E name-length
status- status-message name
message
0x002F value-length
client-error- client-error-attributes-or- value
attributes- values-not-supported
or-values-
not-supported
0x05 start unsupported-attributes unsupported-attributes tag
0x21 integer type value-tag
0x0006 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 end-of-attributes end-of-attributes-tag
9.4 Print-Job Response (success with attributes ignored)
Here is an example of a successful Print-Job response to a Print-Job
request like the previous Print-Job request, except that the value of
"ipp-attribute-fidelity" is false. The print request succeeds, even
though, in this case, the printer supports neither the "sides"
attribute nor the value "20" for the "copies" attribute. Therefore, a
job is created, and both a "job-id" and a "job-uri" operation
attribute are returned. The unsupported attributes are also returned
in an Unsupported Attributes Group. The error code returned is "
successful-ok-ignored-or-substituted-attributes" (0x0001).
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x0001 successful-ok-ignored-or- status-code
substituted-attributes
0x00000001 1 request-id
0x01 start operation-attributes operation-attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes- attributes-charset name
charset
0x0008 value-length
Octets Symbolic Value Protocol field
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 textWithoutLanguage type value-tag
0x000E name-length
status-message status-message name
0x002F value-length
successful-ok- successful-ok-ignored-or- value
ignored-or- substituted-attributes
substituted-
attributes
0x05 start unsupported- unsupported-attributes
attributes tag
0x21 integer type value-tag
0x0006 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
0x02 start job-attributes job-attributes-tag
0x21 integer value-tag
0x0006 name-length
job-id job-id name
0x0004 value-length
147 147 value
0x45 uri type value-tag
0x0007 name-length
job-uri job-uri name
0x001E value-length
http://forest:63 job 123 on pinetree value
1/pinetree/123
0x42 nameWithoutLanguage type value-tag
0x0009 name-length
job-state job-state name
0x0004 value-length
0x0003 pending value
0x03 end-of-attributes end-of-attributes-tag
9.5 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-number
Octets Symbolic Value Protocol field
0x0003 Print-URI operation-id
0x00000001 1 request-id
0x01 start operation-attributes operation-attributes-tag
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-language name
natural-
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000B name-length
printer-uri printer-uri name
0x001A value-length
http://forest printer pinetree value
:631/pinetree
0x45 uri type value-tag
0x000C name-length
document-uri document-uri name
0x11 value-length
ftp://foo.com ftp://foo.com/foo value
/foo
0x42 nameWithoutLanguage type value-tag
0x0008 name-length
job-name job-name name
0x0006 value-length
foobar foobar value
0x02 start job-attributes job-attributes-tag
0x21 integer type value-tag
0x0006 name-length
copies copies name
0x0004 value-length
0x00000001 1 value
0x03 end-of-attributes end-of-attributes-tag
9.6 Create-Job Request
The following is an example of Create-Job request with no parameters
and no attributes:
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x0005 Create-Job operation-id
0x00000001 1 request-id
0x01 start operation-attributes operation-attributes-tag
0x47 charset type value-tag
0x0012 name-length
Octets Symbolic Value Protocol field
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-language name
natural-
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000B name-length
printer-uri printer-uri name
0x001A value-length
http://forest: printer pinetree value
631/pinetree
0x03 end-of-attributes end-of-attributes-tag
9.7 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-number
0x000A Get-Jobs operation-id
0x00000123 0x123 request-id
0x01 start operation-attributes operation-attributes-tag
0x47 charset type value-tag
Octets Symbolic Value Protocol field
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-language name
natural-
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000B name-length
printer-uri printer-uri name
0x001A value-length
http://forest:6 printer pinetree value
31/pinetree
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- requested-attributes name
attributes
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
0x44 keyword type value-tag
0x0000 additional value name-length
0x000F value-length
document-format document-format value
0x03 end-of-attributes end-of-attributes-tag
9.8 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
(because of security reasons):
Octets Symbolic Value Protocol field
0x0100 1.0 version-number
0x0000 successful-ok status-code
0x00000123 0x123 request-id (echoed
back)
0x01 start operation-attributes operation-attribute-tag
0x47 charset type value-tag
0x0012 name-length
attributes- attributes-charset name
charset
0x000A value-length
ISO-8859-1 ISO-8859-1 value
0x48 natural-language type value-tag
0x001B name-length
attributes- attributes-natural-language name
natural-
language
0x0005 value-length
en-us en-US value
0x41 textWithoutLanguage type value-tag
0x000E name-length
status-message status-message name
0x000D value-length
successful-ok successful-ok value
0x02 start job-attributes (1st job-attributes-tag
object)
0x21 integer type value-tag
0x0006 name-length
job-id job-id name
0x0004 value-length
147 147 value
0x36 nameWithLanguage value-tag
0x0008 name-length
job-name job-name name
0x000C value-length
0x0005 sub-value-length
fr-ca fr-CA value
0x0003 sub-value-length
fou fou name
0x02 start job-attributes (2nd job-attributes-tag
object)
0x02 start job-attributes (3rd job-attributes-tag
object)
0x21 integer type value-tag
0x0006 name-length
job-id job-id name
0x0004 value-length
Octets Symbolic Value Protocol field
148 148 value
0x36 nameWithLanguage value-tag
0x0008 name-length
job-name job-name name
0x0012 value-length
0x0005 sub-value-length
de-CH de-CH value
0x0009 sub-value-length
isch guet isch guet name
0x03 end-of-attributes end-of-attributes-tag
10. Appendix C: Registration of MIME Media Type Information for
"application/ipp"
This appendix contains the information that IANA requires for
registering a MIME media type. The information following this
paragraph will be forwarded to IANA to register application/ipp whose
contents are defined in Section 3 "Encoding of the Operation Layer"
in this document:
MIME type name: application
MIME suBType name: ipp
A Content-Type of "application/ipp" indicates an Internet Printing
Protocol message body (request or response). Currently there is one
version: IPP/1.0, whose syntax is described in Section 3 "Encoding of
the Operation Layer" of [RFC2565], and whose semantics are described
in [RFC2566].
Required parameters: none
Optional parameters: none
Encoding considerations:
IPP/1.0 protocol requests/responses MAY contain long lines and ALWAYS
contain binary data (for example attribute value lengths).
Security considerations:
IPP/1.0 protocol requests/responses do not introduce any security
risks not already inherent in the underlying transport protocols.
Protocol mixed-version interworking rules in [RFC2566] as well as
protocol encoding rules in [RFC2565] are complete and unambiguous.
Interoperability considerations:
IPP/1.0 requests (generated by clients) and responses (generated by
servers) MUST comply with all conformance requirements imposed by the
normative specifications [RFC2566] and [RFC2565]. Protocol encoding
rules specified in [RFC2565] are comprehensive, so that
interoperability between conforming implementations is guaranteed
(although support for specific optional features is not ensured).
Both the "charset" and "natural-language" of all IPP/1.0 attribute
values which are a LOCALIZED-STRING are explicit within IPP protocol
requests/responses (without recourse to any external information in
HTTP, SMTP, or other message transport headers).
Published specification:
[RFC2566] Isaacson, S., deBry, R., Hastings, T., Herriot, R. and P.
Powell, "Internet Printing Protocol/1.0: Model and
Semantics" RFC2566, April 1999.
[RFC2565] Herriot, R., Butler, S., Moore, P., Tuner, R., "Internet
Printing Protocol/1.0: Encoding and Transport", RFC2565,
April 1999.
Applications which use this media type:
Internet Printing Protocol (IPP) print clients and print servers,
communicating using HTTP/1.1 (see [RFC2565]), SMTP/ESMTP, FTP, or
other transport protocol. Messages of type "application/ipp" are
self-contained and transport-independent, including "charset" and
"natural-language" context for any LOCALIZED-STRING value.
Person & email address to contact for further information:
Scott A. Isaacson
Novell, Inc.
122 E 1700 S
Provo, UT 84606
Phone: 801-861-7366
Fax: 801-861-4025
Email: sisaacson@novell.com
or
Robert Herriot (Editor)
Xerox Corporation
3400 Hillview Ave., Bldg #1
Palo Alto, CA 94304
Phone: 650-813-7696
Fax: 650-813-6860
EMail: rherriot@pahv.xerox.com
11. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limit