| Rfc | 8010 |
|---|
| Title | Internet Printing Protocol/1.1: Encoding and Transport |
|---|
| Author | M. Sweet, I.
McDonald |
|---|
| Date | January 2017 |
|---|
| Format: | TXT, HTML |
|---|
| Obsoletes | RFC2910,
RFC3382 |
|---|
| Also | STD0092 |
|---|
| Status: | INTERNET STANDARD |
|---|
|
Internet Engineering Task Force (IETF) M. Sweet
Request for Comments: 8010 Apple Inc.
Obsoletes: 2910, 3382 I. McDonald
Category: Standards Track High North, Inc.
ISSN: 2070-1721 January 2017
Internet Printing Protocol/1.1: Encoding and Transport
Abstract
The Internet Printing Protocol (IPP) is an application-level protocol
for distributed printing using Internet tools and technologies. This
document defines the rules for encoding IPP operations, attributes,
and values into the Internet MIME media type called
"application/ipp". It also defines the rules for transporting a
message body whose Content-Type is "application/ipp" over HTTP and/or
HTTPS. The IPP data model and operation semantics are described in
"Internet Printing Protocol/1.1: Model and Semantics" (RFC 8011).
This document obsoletes RFCs 2910 and 3382.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8010.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2.2. Printing Terminology . . . . . . . . . . . . . . . . . . 5
2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6
3. Encoding of the Operation Layer . . . . . . . . . . . . . . . 6
3.1. Picture of the Encoding . . . . . . . . . . . . . . . . . 8
3.1.1. Request and Response . . . . . . . . . . . . . . . . 8
3.1.2. Attribute Group . . . . . . . . . . . . . . . . . . . 9
3.1.3. Attribute . . . . . . . . . . . . . . . . . . . . . . 9
3.1.4. Attribute-with-one-value . . . . . . . . . . . . . . 10
3.1.5. Additional-value . . . . . . . . . . . . . . . . . . 11
3.1.6. Collection Attribute . . . . . . . . . . . . . . . . 12
3.1.7. Member Attributes . . . . . . . . . . . . . . . . . . 13
3.1.8. Alternative Picture of the Encoding of a Request or a
Response . . . . . . . . . . . . . . . . . . . . . . 14
3.2. Syntax of Encoding . . . . . . . . . . . . . . . . . . . 15
3.3. Attribute-group . . . . . . . . . . . . . . . . . . . . . 16
3.4. Required Parameters . . . . . . . . . . . . . . . . . . . 18
3.4.1. "version-number" . . . . . . . . . . . . . . . . . . 18
3.4.2. "operation-id" . . . . . . . . . . . . . . . . . . . 18
3.4.3. "status-code" . . . . . . . . . . . . . . . . . . . . 19
3.4.4. "request-id" . . . . . . . . . . . . . . . . . . . . 19
3.5. Tags . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.5.1. "delimiter-tag" Values . . . . . . . . . . . . . . . 19
3.5.2. "value-tag" Values . . . . . . . . . . . . . . . . . 20
3.6. "name-length" . . . . . . . . . . . . . . . . . . . . . . 23
3.7. (Attribute) "name" . . . . . . . . . . . . . . . . . . . 23
3.8. "value-length" . . . . . . . . . . . . . . . . . . . . . 23
3.9. (Attribute) "value" . . . . . . . . . . . . . . . . . . . 24
3.10. Data . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4. Encoding of Transport Layer . . . . . . . . . . . . . . . . . 26
4.1. Printer URI, Job URI, and Job ID . . . . . . . . . . . . 26
5. IPP URI Schemes . . . . . . . . . . . . . . . . . . . . . . . 28
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
7. Internationalization Considerations . . . . . . . . . . . . . 31
8. Security Considerations . . . . . . . . . . . . . . . . . . . 31
8.1. Security Conformance Requirements . . . . . . . . . . . . 31
8.1.1. Digest Authentication . . . . . . . . . . . . . . . . 32
8.1.2. Transport Layer Security (TLS) . . . . . . . . . . . 32
8.2. Using IPP with TLS . . . . . . . . . . . . . . . . . . . 33
9. Interoperability with Other IPP Versions . . . . . . . . . . 33
9.1. The "version-number" Parameter . . . . . . . . . . . . . 34
9.2. Security and URI Schemes . . . . . . . . . . . . . . . . 34
10. Changes since RFC 2910 . . . . . . . . . . . . . . . . . . . 35
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1. Normative References . . . . . . . . . . . . . . . . . . 36
11.2. Informative References . . . . . . . . . . . . . . . . . 38
Appendix A. Protocol Examples . . . . . . . . . . . . . . . . . 40
A.1. Print-Job Request . . . . . . . . . . . . . . . . . . . . 40
A.2. Print-Job Response (Successful) . . . . . . . . . . . . . 41
A.3. Print-Job Response (Failure) . . . . . . . . . . . . . . 42
A.4. Print-Job Response (Success with Attributes Ignored) . . 43
A.5. Print-URI Request . . . . . . . . . . . . . . . . . . . . 45
A.6. Create-Job Request . . . . . . . . . . . . . . . . . . . 46
A.7. Create-Job Request with Collection Attributes . . . . . . 46
A.8. Get-Jobs Request . . . . . . . . . . . . . . . . . . . . 48
A.9. Get-Jobs Response . . . . . . . . . . . . . . . . . . . . 49
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
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 request and response. All
IPP implementations support HTTP/1.1, the relevant parts of which are
described in the following RFCs:
o Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
[RFC7230]
o Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
[RFC7231]
o Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
[RFC7232]
o Hypertext Transfer Protocol (HTTP/1.1): Caching [RFC7234]
o Hypertext Transfer Protocol (HTTP/1.1): Authentication [RFC7235]
o The 'Basic' HTTP Authentication Scheme [RFC7617]
o HTTP Digest Access Authentication [RFC7616]
IPP implementations can support HTTP/2, which is described in the
following RFCs:
o Hypertext Transfer Protocol Version 2 (HTTP/2) [RFC7540]
o HPACK - Header Compression for HTTP/2 [RFC7541]
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 "Internet Printing Protocol/1.1: Model and Semantics"
document [RFC8011] and subsequent extensions (collectively known as
the IPP Model) define the semantics of such a message body and the
supported values. This document specifies the encoding of an IPP
request and response message.
2. Conventions Used in This Document
2.1. Requirements Language
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 [RFC2119].
2.2. Printing Terminology
Client: Initiator of outgoing IPP session requests and sender of
outgoing IPP operation requests (Hypertext Transfer Protocol --
HTTP/1.1 [RFC7230] User Agent).
Document: An object created and managed by a Printer that contains
description, processing, and status information. A Document object
may have attached data and is bound to a single Job.
'ipp' URI: An IPP URI as defined in [RFC3510].
'ipps' URI: An IPPS URI as defined in [RFC7472].
Job: An object created and managed by a Printer that contains
description, processing, and status information. The Job also
contains zero or more Document objects.
Logical Device: A print server, software service, or gateway that
processes Jobs and either forwards or stores the processed Job or
uses one or more Physical Devices to render output.
Model: The semantics of operations, attributes, values, and status-
codes used in the Internet Printing Protocol as defined in the
Internet Printing Protocol/1.1: Model and Semantics document
[RFC8011] and subsequent extensions.
Output Device: A single Logical or Physical Device.
Physical Device: A hardware implementation of an endpoint device,
e.g., a marking engine, a fax modem, etc.
Printer: Listener for incoming IPP session requests and receiver of
incoming IPP operation requests (Hypertext Transfer Protocol --
HTTP/1.1 [RFC7230] Server) that represents one or more Physical
Devices or a Logical Device.
2.3. Abbreviations
ABNF: Augmented Backus-Naur Form [RFC5234]
ASCII: American Standard Code for Information Interchange [RFC20]
HTTP: Hypertext Transfer Protocol [RFC7230]
HTTPS: HTTP over TLS [RFC2818]
IANA: Internet Assigned Numbers Authority
IEEE: Institute of Electrical and Electronics Engineers
IESG: Internet Engineering Steering Group
IPP: Internet Printing Protocol (this document and [PWG5100.12])
ISTO: IEEE Industry Standards and Technology Organization
LPD: Line Printer Daemon Protocol [RFC1179]
PWG: IEEE-ISTO Printer Working Group
RFC: Request for Comments
TCP: Transmission Control Protocol [RFC793]
TLS: Transport Layer Security [RFC5246]
URI: Uniform Resource Identifier [RFC3986]
URL: Uniform Resource Locator [RFC3986]
UTF-8: Unicode Transformation Format - 8-bit [RFC3629]
3. Encoding of the Operation Layer
The operation layer is the message body part of the HTTP request or
response and it MUST contain a single IPP operation request or IPP
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 [RFC2978] 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
and 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 is henceforth called a LOCALIZED-STRING.
An octet string MUST be in "Model order" with the first octet in the
value (according to the Model 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. A one-octet integer, henceforth called a
SIGNED-BYTE, is used for the version-number and tag fields. A two-
byte integer, henceforth called a SIGNED-SHORT, is used for the
operation-id, status-code, and length fields. A four-byte integer,
henceforth called a SIGNED-INTEGER, is used for value fields and the
request-id.
The following two sections present the encoding of the operation
layer in two ways:
o informally through pictures and description
o formally through Augmented Backus-Naur Form (ABNF), as specified
by RFC 5234 [RFC5234]
An operation request or response MUST use the encoding described in
these two sections.
3.1. Picture of the Encoding
3.1.1. Request and Response
An operation request or response is encoded as follows:
-----------------------------------------------
| version-number | 2 bytes - required
-----------------------------------------------
| operation-id (request) |
| or | 2 bytes - required
| status-code (response) |
-----------------------------------------------
| request-id | 4 bytes - required
-----------------------------------------------
| attribute-group | n bytes - 0 or more
-----------------------------------------------
| end-of-attributes-tag | 1 byte - required
-----------------------------------------------
| data | q bytes - optional
-----------------------------------------------
Figure 1: IPP Message Format
The first three fields in the above diagram contain the value of
attributes described in Section 4.1.1 of the Model and Semantics
document [RFC8011].
The fourth field is the "attribute-group" field, and it occurs 0 or
more times. Each "attribute-group" field represents a single group
of attributes, such as an Operation Attributes group or a Job
Attributes group (see the Model). The Model specifies the required
attribute groups and their order for each operation request and
response.
The "end-of-attributes-tag" field is always present, even when the
"data" is not present. The Model specifies whether the "data" field
is present for each operation request and response.
3.1.2. Attribute Group
Each "attribute-group" field is encoded as follows:
-----------------------------------------------
| begin-attribute-group-tag | 1 byte
----------------------------------------------------------
| attribute | p bytes |- 0 or more
----------------------------------------------------------
Figure 2: Attribute Group Encoding
An "attribute-group" field contains zero or more "attribute" fields.
Note that the values of the "begin-attribute-group-tag" field and the
"end-of-attributes-tag" field are called "delimiter-tags".
3.1.3. Attribute
An "attribute" field is encoded as follows:
-----------------------------------------------
| attribute-with-one-value | q bytes
----------------------------------------------------------
| additional-value | r bytes |- 0 or more
----------------------------------------------------------
Figure 3: Attribute Encoding
When an attribute is single valued (e.g., "copies" with a value of
10) or multi-valued with one value (e.g., "sides-supported" with just
the value 'one-sided'), it is encoded with just an "attribute-with-
one-value" field. When an attribute is multi-valued with n values
(e.g., "sides-supported" with the values 'one-sided' and 'two-sided-
long-edge'), it is encoded with an "attribute-with-one-value" field
followed by n-1 "additional-value" fields.
3.1.4. Attribute-with-one-value
Each "attribute-with-one-value" field is encoded as follows:
-----------------------------------------------
| value-tag | 1 byte
-----------------------------------------------
| name-length (value is u) | 2 bytes
-----------------------------------------------
| name | u bytes
-----------------------------------------------
| value-length (value is v) | 2 bytes
-----------------------------------------------
| value | v bytes
-----------------------------------------------
Figure 4: Single Value Attribute Encoding
An "attribute-with-one-value" field is encoded with five subfields:
o The "value-tag" field specifies the attribute syntax, e.g., 0x44
for the attribute syntax 'keyword'.
o The "name-length" field specifies the length of the "name" field
in bytes, e.g., u in the above diagram or 15 for the name "sides-
supported".
o The "name" field contains the textual name of the attribute, e.g.,
"sides-supported".
o The "value-length" field specifies the length of the "value" field
in bytes, e.g., v in the above diagram or 9 for the (keyword)
value 'one-sided'.
o The "value" field contains the value of the attribute, e.g., the
textual value 'one-sided'.
3.1.5. Additional-value
Each "additional-value" field is encoded as follows:
-----------------------------------------------
| value-tag | 1 byte
-----------------------------------------------
| name-length (value is 0x0000) | 2 bytes
-----------------------------------------------
| value-length (value is w) | 2 bytes
-----------------------------------------------
| value | w bytes
-----------------------------------------------
Figure 5: Additional Attribute Value Encoding
An "additional-value" is encoded with four subfields:
o The "value-tag" field specifies the attribute syntax, e.g., 0x44
for the attribute syntax 'keyword'.
o The "name-length" field has the value of 0 in order to signify
that it is an "additional-value". The value of the "name-length"
field distinguishes an "additional-value" field ("name-length" is
0) from an "attribute-with-one-value" field ("name-length" is not
0).
o The "value-length" field specifies the length of the "value" field
in bytes, e.g., w in the above diagram or 19 for the (keyword)
value 'two-sided-long-edge'.
o The "value" field contains the value of the attribute, e.g., the
textual value 'two-sided-long-edge'.
3.1.6. Collection Attribute
Collection attributes create a named group containing related
"member" attributes. The "attribute-with-one-value" field for a
collection attribute is encoded as follows:
-----------------------------------------------
| value-tag (value is 0x34) | 1 byte
-----------------------------------------------
| name-length (value is u) | 2 bytes
-----------------------------------------------
| name | u bytes
-----------------------------------------------
| value-length (value is 0x0000) | 2 bytes
-----------------------------------------------------------
| member-attribute | q bytes |-0 or more
-----------------------------------------------------------
| end-value-tag (value is 0x37) | 1 byte
-----------------------------------------------
| end-name-length (value is 0x0000) | 2 bytes
-----------------------------------------------
| end-value-length (value is 0x0000) | 2 bytes
-----------------------------------------------
Figure 6: Collection Attribute Encoding
Collection attribute is encoded with eight subfields:
o The "value-tag" field specifies the start attribute syntax: 0x34
for the attribute syntax 'begCollection'.
o The "name-length" field specifies the length of the "name" field
in bytes, e.g., u in the above diagram or 9 for the name "media-
col". Additional collection attribute values use a name length of
0x0000.
o The "name" field contains the textual name of the attribute, e.g.,
"media-col".
o The "value-length" field specifies a length of 0x0000.
o The "member-attribute" field contains member attributes encoded as
defined in Section 3.1.7.
o The "end-value-tag" field specifies the end attribute syntax: 0x37
for the attribute syntax 'endCollection'.
o The "end-name-length" field specifies a length of 0x0000.
o The "end-value-length" field specifies a length of 0x0000.
3.1.7. Member Attributes
Each "member-attribute" field is encoded as follows:
-----------------------------------------------
| value-tag (value is 0x4a) | 1 byte
-----------------------------------------------
| name-length (value is 0x0000) | 2 bytes
-----------------------------------------------
| value-length (value is w) | 2 bytes
-----------------------------------------------
| value (member-name) | w bytes
-----------------------------------------------
| member-value-tag | 1 byte
-----------------------------------------------
| name-length (value is 0x0000) | 2 bytes
-----------------------------------------------
| member-value-length (value is x) | 2 bytes
-----------------------------------------------
| member-value | x bytes
-----------------------------------------------
Figure 7: Member Attribute Encoding
A "member-attribute" is encoded with eight subfields:
o The "value-tag" field specifies 0x4a for the attribute syntax
'memberAttrName'.
o The "name-length" field has the value of 0 in order to signify
that it is a "member-attribute" contained in the collection.
o The "value-length" field specifies the length of the "value" field
in bytes, e.g., w in the above diagram or 10 for the member
attribute name 'media-type'. Additional member attribute values
are specified using a value length of 0.
o The "value" field contains the name of the member attribute, e.g.,
the textual value 'media-type'.
o The "member-value-tag" field specifies the attribute syntax for
the member attribute, e.g., 0x44 for the attribute syntax
'keyword'.
o The second "name-length" field has the value of 0 in order to
signify that it is a "member-attribute" contained in the
collection.
o The "member-value-length" field specifies the length of the member
attribute value, e.g., x in the above diagram or 10 for the value
'stationery'.
o The "member-value" field contains the value of the attribute,
e.g., the textual value 'stationery'.
3.1.8. Alternative Picture of the Encoding of a Request or a Response
From the standpoint of a parser that performs an action based on a
"tag" value, 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 | 1 byte - required
-----------------------------------------------
| data | y bytes - optional
-----------------------------------------------
Figure 8: Encoding Based on Value Tags
The following shows what fields the parser would expect after each
type of "tag":
o "begin-attribute-group-tag": expect zero or more "attribute"
fields
o "value-tag": expect the remainder of an "attribute-with-one-value"
or an "additional-value"
o "end-of-attributes-tag": expect that "attribute" fields are
complete and there is optional "data"
3.2. Syntax of Encoding
The ABNF [RFC5234] syntax for an IPP message is shown in Figure 9.
ipp-message = ipp-request / ipp-response
ipp-request = version-number operation-id request-id
*attribute-group end-of-attributes-tag data
ipp-response = version-number status-code request-id
*attribute-group end-of-attributes-tag data
version-number = major-version-number minor-version-number
major-version-number = SIGNED-BYTE
minor-version-number = SIGNED-BYTE
operation-id = SIGNED-SHORT ; mapping from model
status-code = SIGNED-SHORT ; mapping from model
request-id = SIGNED-INTEGER ; whose value is > 0
attribute-group = begin-attribute-group-tag *attribute
attribute = attribute-with-one-value *additional-value
attribute-with-one-value = value-tag name-length name
value-length value
additional-value = 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
value-tag = %x10-ff ; see Section 3.5.2
begin-attribute-group-tag = %x00-02 / %x04-0f ; see Section 3.5.1
end-of-attributes-tag = %x03 ; tag of 3
; see Section 3.5.1
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
Figure 9: ABNF of IPP Message Format
Figure 10 defines additional terms that are referenced in this
document and provides an alternate grouping of the delimiter tags.
delimiter-tag = begin-attribute-group-tag / ; see Section 3.5.1
end-of-attributes-tag
begin-attribute-group-tag = %x00 / operation-attributes-tag /
job-attributes-tag / printer-attributes-tag /
unsupported-attributes-tag / future-group-tags
operation-attributes-tag = %x01 ; tag of 1
job-attributes-tag = %x02 ; tag of 2
end-of-attributes-tag = %x03 ; tag of 3
printer-attributes-tag = %x04 ; tag of 4
unsupported-attributes-tag = %x05 ; tag of 5
future-group-tags = %x06-0f ; future extensions
Figure 10: ABNF for Attribute Group Tags
3.3. Attribute-group
Each "attribute-group" field MUST be encoded with the "begin-
attribute-group-tag" field followed by zero or more "attribute" sub-
fields.
Table 1 maps the Model group name to value of the "begin-attribute-
group-tag" field:
+----------------+--------------------------------------------------+
| Model Document | "begin-attribute-group-tag" field values |
| Group | |
+----------------+--------------------------------------------------+
| Operation | "operations-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Job Template | "job-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Job Object | "job-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Unsupported | "unsupported-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Requested | (Get-Job-Attributes) "job-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Requested | (Get-Printer-Attributes)"printer-attributes-tag" |
| Attributes | |
+----------------+--------------------------------------------------+
| Document | in a special position at the end of the message |
| Content | as described in Section 3.1.1. |
+----------------+--------------------------------------------------+
Table 1: Group Values
For each operation request and response, the Model prescribes the
required and optional attribute groups, along with their order.
Within each attribute group, the Model prescribes the required and
optional attributes, along with their order.
When the Model requires an attribute group in a request or response
and the attribute group contains zero attributes, a request or
response SHOULD encode the attribute group with the "begin-attribute-
group-tag" field followed by zero "attribute" fields. For example,
if the Client requests a single unsupported attribute with the Get-
Printer-Attributes operation, the Printer MUST return no "attribute"
fields, and it SHOULD return a "begin-attribute-group-tag" field for
the Printer Attributes group. The Unsupported Attributes group is
not such an example. According to the Model, the Unsupported
Attributes group SHOULD be present only if the Unsupported Attributes
group contains at least one attribute.
A receiver of a request MUST be able to process the following as
equivalent empty attribute groups:
a. A "begin-attribute-group-tag" field with zero following
"attribute" fields.
b. A missing, but expected, "begin-attribute-group-tag" field.
When the Model requires a sequence of an unknown number of attribute
groups, each of the same type, the encoding MUST contain one "begin-
attribute-group-tag" field for each attribute group, even when an
"attribute-group" field contains zero "attribute" sub-fields. For
example, the Get-Jobs operation may return zero attributes for some
Jobs and not others. The "begin-attribute-group-tag" field followed
by zero "attribute" fields tells the recipient that there is a Job in
queue for which no information is available except that it is in the
queue.
3.4. Required Parameters
Some operation elements are called parameters in the Model. They
MUST be encoded in a special position and they MUST NOT appear as
operation attributes. These parameters are described in the
subsections below.
3.4.1. "version-number"
The "version-number" field consists of a major and minor version-
number, each of which is represented by a SIGNED-BYTE. The major
version-number is the first byte of the encoding and the minor
version-number is the second byte of the encoding. The protocol
described in [RFC8011] has a major version-number of 1 (0x01) and a
minor version-number of 1 (0x01). The ABNF for these two bytes is
%x01.01.
Note: See Section 9 for more information on the "version-number"
field and IPP version numbers.
3.4.2. "operation-id"
The "operation-id" field contains an operation-id value as defined in
the Model. The value is encoded as a SIGNED-SHORT and is located in
the third and fourth bytes of the encoding of an operation request.
3.4.3. "status-code"
The "status-code" field contains a status-code value as defined in
the Model. The value is encoded as a SIGNED-SHORT and is located in
the third and fourth bytes of the encoding of an operation response.
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
MUST NOT contain an IPP message body, and thus no IPP status-code is
returned.
3.4.4. "request-id"
The "request-id" field contains the request-id value as defined in
the Model. The value is encoded as a SIGNED-INTEGER and is located
in the fifth through eighth bytes of the encoding.
3.5. Tags
There are two kinds of tags:
o delimiter tags: delimit major sections of the protocol, namely
attribute groups and data
o value tags: specify the type of each attribute value
Tags are part of the IANA IPP registry [IANA-IPP]
3.5.1. "delimiter-tag" Values
Table 2 specifies the values for the delimiter tags defined in this
document. These tags are registered, along with tags defined in
other documents, in the "Attribute Group Tags" registry.
+-----------------+------------------------------+
| Tag Value (Hex) | Meaning |
+-----------------+------------------------------+
| 0x00 | Reserved |
| 0x01 | "operation-attributes-tag" |
| 0x02 | "job-attributes-tag" |
| 0x03 | "end-of-attributes-tag" |
| 0x04 | "printer-attributes-tag" |
| 0x05 | "unsupported-attributes-tag" |
+-----------------+------------------------------+
Table 2: "delimiter-tag" Values
When a "begin-attribute-group-tag" field occurs in the protocol, it
means that zero or more following attributes up to the next group tag
are attributes belonging to the attribute group specified by the
value of the "begin-attribute-group-tag". For example, if the value
of "begin-attribute-group-tag" is 0x01, the following attributes are
members of the Operations Attributes group.
The "end-of-attributes-tag" (value 0x03) MUST occur exactly once in
an operation and MUST be the last "delimiter-tag". If the operation
has a document-data group, the Document data in that group follows
the "end-of-attributes-tag".
The order and presence of "attribute-group" fields (whose beginning
is marked by the "begin-attribute-group-tag" subfield) for each
operation request and each operation response MUST be that defined in
the Model.
A Printer MUST treat a "delimiter-tag" (values from 0x00 through
0x0f) differently from a "value-tag" (values from 0x10 through 0xff)
so that the Printer knows there is an entire attribute group as
opposed to a single value.
3.5.2. "value-tag" Values
The remaining tables show values for the "value-tag" field, which is
the first octet of an attribute. The "value-tag" field specifies the
type of the value of the attribute.
Table 3 specifies the "out-of-band" values for the "value-tag" field
defined in this document. These tags are registered, along with tags
defined in other documents, in the "Out-of-Band Attribute Value Tags"
registry.
+-----------------+-------------+
| Tag Value (Hex) | Meaning |
+-----------------+-------------+
| 0x10 | unsupported |
| 0x12 | unknown |
| 0x13 | no-value |
+-----------------+-------------+
Table 3: Out-of-Band Values
Table 4 specifies the integer values defined in this document for the
"value-tag" field; they are registered in the "Attribute Syntaxes"
registry.
+----------------+--------------------------------------------------+
| Tag Value | Meaning |
| (Hex) | |
+----------------+--------------------------------------------------+
| 0x20 | Unassigned integer data type (see IANA IPP |
| | registry) |
| 0x21 | integer |
| 0x22 | boolean |
| 0x23 | enum |
| 0x24-0x2f | Unassigned integer data types (see IANA IPP |
| | registry) |
+----------------+--------------------------------------------------+
Table 4: Integer Tags
Table 5 specifies the octetString values defined in this document for
the "value-tag" field; they are registered in the "Attribute
Syntaxes" registry.
+---------------+---------------------------------------------------+
| Tag Value | Meaning |
| (Hex) | |
+---------------+---------------------------------------------------+
| 0x30 | octetString with an unspecified format |
| 0x31 | dateTime |
| 0x32 | resolution |
| 0x33 | rangeOfInteger |
| 0x34 | begCollection |
| 0x35 | textWithLanguage |
| 0x36 | nameWithLanguage |
| 0x37 | endCollection |
| 0x38-0x3f | Unassigned octetString data types (see IANA IPP |
| | registry) |
+---------------+---------------------------------------------------+
Table 5: octetString Tags
Table 6 specifies the character-string values defined in this
document for the "value-tag" field; they are registered in the
"Attribute Syntaxes" registry.
+---------------+---------------------------------------------------+
| Tag Value | Meaning |
| (Hex) | |
+---------------+---------------------------------------------------+
| 0x40 | Unassigned character-string data type (see IANA |
| | IPP registry) |
| 0x41 | textWithoutLanguage |
| 0x42 | nameWithoutLanguage |
| 0x43 | Unassigned character-string data type (see IANA |
| | IPP registry) |
| 0x44 | keyword |
| 0x45 | uri |
| 0x46 | uriScheme |
| 0x47 | charset |
| 0x48 | naturalLanguage |
| 0x49 | mimeMediaType |
| 0x4a | memberAttrName |
| 0x4b-0x5f | Unassigned character-string data types (see IANA |
| | IPP registry) |
+---------------+---------------------------------------------------+
Table 6: String Tags
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 type definitions in
Standards Track documents.
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 four 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. Values from 0x00000000 to
0x3fffffff are reserved for definition in future Standards Track
documents. The values 0x40000000 to 0x7fffffff are reserved for
vendor extensions.
3.6. "name-length"
The "name-length" field consists of a SIGNED-SHORT and specifies the
number of octets in the immediately following "name" field. The
value of this field excludes the two bytes of the "name-length"
field. For example, if the "name" field contains 'sides', the value
of this field is 5.
If a "name-length" field has a value of zero, the following "name"
field is empty and the following value is treated as an additional
value for the attribute encoded in the nearest preceding "attribute-
with-one-value" field. Within an attribute group, if two or more
attributes have the same name, the attribute group is malformed (see
[RFC8011]). The zero-length name is the only mechanism for multi-
valued attributes.
3.7. (Attribute) "name"
The "name" field contains the name of an attribute. The Model
specifies such names.
3.8. "value-length"
The "value-length" field consists of a SIGNED-SHORT, which specifies
the number of octets in the immediately following "value" field. The
value of this field excludes the two bytes of the "value-length"
field. For example, if the "value" field contains the keyword
(string) value 'one-sided', the value of this field is 9.
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 binary signed bytes, e.g., the
boolean type, the sender MUST encode the value in exactly one octet.
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.
For "out-of-band" values for the "value-tag" field defined in this
document, such as 'unsupported', the "value-length" MUST be 0 and the
"value" empty; the "value" has no meaning when the "value-tag" has
one of these "out-of-band" values. For future "out-of-band" "value-
tag" fields, the same rule holds unless the definition explicitly
states that the "value-length" MAY be non-zero and the "value" non-
empty
3.9. (Attribute) "value"
The syntax types (specified by the "value-tag" field) and most of the
details of the representation of attribute values are defined in the
Model. Table 7 augments the information in the Model and defines the
syntax types from the Model in terms of the five basic types defined
in Section 3. The five 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 four fields: a |
| | SIGNED-SHORT, which is the number of |
| | octets in the following field; a value of |
| | type natural-language; a SIGNED-SHORT, |
| | which is the number of octets in the |
| | following field; and 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 four fields: a |
| | SIGNED-SHORT, which is the number of |
| | octets in the following field; a value of |
| | type natural-language; a SIGNED-SHORT, |
| | which is the number of octets in the |
| | following field; and 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' |
+----------------------+--------------------------------------------+
| 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 |
| | two 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 two 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 one value. Each |
| | value X is encoded according to the rules |
| | for encoding its type. |
+----------------------+--------------------------------------------+
| octetString | OCTET-STRING |
+----------------------+--------------------------------------------+
| collection | Encoding as defined in Section 3.1.6. |
+----------------------+--------------------------------------------+
Table 7: Attribute Value Encoding
The attribute syntax type of the value determines its encoding and
the value of its "value-tag".
3.10. Data
The "data" field MUST include any data required by the operation.
4. Encoding of Transport Layer
HTTP/1.1 [RFC7230] is the REQUIRED transport layer for this protocol.
HTTP/2 [RFC7540] is an OPTIONAL transport layer for this protocol.
The operation layer has been designed with the assumption that the
transport layer contains the following information:
o the target URI for the operation; and
o 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.
Printer implementations MUST support HTTP over the IANA-assigned
well-known port 631 (the IPP default port), although a Printer
implementation can support HTTP over some other port as well.
Each HTTP operation MUST use the POST method where the request-target
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 HTTP [RFC7230]. A Printer (server) implementation MUST adhere to
the rules for an origin server described for HTTP [RFC7230].
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,
consult the HTTP documents [RFC7230].
An HTTP/1.1 server MUST support chunking for IPP requests, and an IPP
Client MUST support chunking for IPP responses according to HTTP/1.1
[RFC7230].
4.1. Printer URI, Job URI, and Job ID
All Printer and Job objects are identified by a Uniform Resource
Identifier (URI) [RFC3986] so that they can be persistently and
unambiguously referenced. Jobs can also be identified by a
combination of Printer URI and Job ID.
Some operation elements are encoded twice, once as the request-target
on the HTTP request-line and a second time as a REQUIRED operation
attribute in the application/ipp entity. These attributes are the
target for the operation and are called "printer-uri" and "job-uri".
Note: The target URI is included twice in an operation referencing
the same IPP object, but the two URIs can be different. For example,
the HTTP request-target can be relative while the IPP request URI is
absolute.
HTTP 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 URIs are used in the mapping of
IPP onto HTTP:
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 URIs are not used as the
addressing mechanism in the transport layer.
2. Even though these two URIs 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.
4. Once the HTTP server resource begins to process the HTTP request,
it can get the reference to the appropriate IPP Printer object
from either the HTTP URI (using to the context of the HTTP server
for relative URIs) 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
IPP operation attribute MUST be an absolute URI.
5. IPP URI Schemes
The IPP URI schemes are 'ipp' [RFC3510] and 'ipps' [RFC7472].
Clients and Printers MUST support the ipp-URI value in the following
IPP attributes:
o Job attributes:
* job-uri
* job-printer-uri
o Printer attributes:
* printer-uri-supported
o Operation attributes:
* job-uri
* printer-uri
Each of the above attributes identifies a Printer or Job. The
ipp-URI and ipps-URI are intended as the value of the attributes in
this list. All of these attributes have a syntax type of 'uri', but
there are attributes with a syntax type of 'uri' that do not use the
'ipp' scheme, e.g., "job-more-info".
If a Printer registers its URI with a directory service, the Printer
MUST register an ipp-URI or ipps-URI.
When a Client sends a request, it MUST convert a target ipp-URI to a
target http-URL (or ipps-URI to a target https-URI) for the HTTP
layer according to the following steps:
1. change the 'ipp' scheme to 'http' or 'ipps' scheme to 'https';
and
2. add an explicit port 631 if the ipp-URL or ipps-URL does not
contain an explicit port. Note that port 631 is the IANA-
assigned well-known port for the 'ipp' and 'ipps' schemes.
The Client MUST use the target http-URL or https-URL in both the HTTP
request-line and HTTP headers, as specified by HTTP [RFC7230].
However, the Client MUST use the target ipp-URI or ipps-URI for the
value of the "printer-uri" or "job-uri" operation attribute within
the application/ipp body of the request. The server MUST use the
ipp-URI or ipps-URI for the value of the "printer-uri", "job-uri", or
"printer-uri-supported" attributes within the application/ipp body of
the response.
For example, when an IPP Client sends a request directly, i.e., no
proxy, to an ipp-URI "ipp://printer.example.com/ipp/print/myqueue",
it opens a TCP connection to port 631 (the IPP implicit port) on the
host "printer.example.com" and sends the following data:
POST /ipp/print/myqueue HTTP/1.1
Host: printer.example.com:631
Content-type: application/ipp
Transfer-Encoding: chunked
...
"printer-uri" 'ipp://printer.example.com/ipp/print/myqueue'
(encoded in application/ipp message body)
...
Figure 11: Direct IPP Request
As another example, when an IPP Client sends the same request as
above via a proxy "myproxy.example.com", it opens a TCP connection to
the proxy port 8080 on the proxy host "myproxy.example.com" and sends
the following data:
POST http://printer.example.com:631/ipp/print/myqueue HTTP/1.1
Host: printer.example.com:631
Content-type: application/ipp
Transfer-Encoding: chunked
...
"printer-uri" 'ipp://printer.example.com/ipp/print/myqueue'
(encoded in application/ipp message body)
...
Figure 12: Proxied IPP Request
The proxy then connects to the IPP origin server with headers that
are the same as the "no-proxy" example above.
6. IANA Considerations
The IANA-PRINTER-MIB [RFC3805] has been updated to reference this
document; the current version is available from
<http://www.iana.org>.
See the IANA Considerations in the document "Internet Printing
Protocol/1.1: Model and Semantics" [RFC8011] for information on IANA
considerations for IPP extensions. IANA has updated the existing
'application/ipp' media type registration (whose contents are defined
in Section 3 "Encoding of the Operation Layer") with the following
information.
Type name: application
Subtype name: ipp
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: IPP requests/responses MAY contain long
lines and ALWAYS contain binary data (for example, attribute value
lengths).
Security considerations: IPP requests/responses do not introduce any
security risks not already inherent in the underlying transport
protocols. Protocol mixed-version interworking rules in [RFC8011] as
well as protocol-encoding rules in this document are complete and
unambiguous. See also the security considerations in this document
and [RFC8011].
Interoperability considerations: IPP requests (generated by Clients)
and responses (generated by servers) MUST comply with all conformance
requirements imposed by the normative specifications [RFC8011] and
this document. Protocol-encoding rules specified in RFC 8010 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 attribute values that are a LOCALIZED-STRING are explicit
within IPP requests/responses (without recourse to any external
information in HTTP, SMTP, or other message transport headers).
Published specifications: RFCs 8010 and 8011
Applications that use this media type: Internet Printing Protocol
(IPP) print clients and print servers that communicate using HTTP/
HTTPS or other transport protocols. Messages of type "application/
ipp" are self-contained and transport independent, including
"charset" and "natural-language" context for any LOCALIZED-STRING
value.
Fragment identifier considerations: N/A
Additional information:
Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
Person & email address to contact for further information:
ISTO PWG IPP Workgroup <ipp@pwg.org>
Intended usage: COMMON
Restrictions on usage: N/A
Author: ISTO PWG IPP Workgroup <ipp@pwg.org>
Change controller: ISTO PWG IPP Workgroup <ipp@pwg.org>
Provisional registration? (standards tree only): No
7. Internationalization Considerations
See the section on "Internationalization Considerations" in the
document "Internet Printing Protocol/1.1: Model and Semantics"
[RFC8011] for information on internationalization. This document
adds no additional issues.
8. Security Considerations
The IPP Model and Semantics document [RFC8011] discusses high-level
security requirements (Client Authentication, Server Authentication,
and Operation Privacy). Client Authentication is the mechanism by
which the Client proves its identity to the server in a secure
manner. Server Authentication is the mechanism by which the server
proves its identity to the Client in a secure manner. Operation
Privacy is defined as a mechanism for protecting operations from
eavesdropping.
Message Integrity is addressed in the document "Internet Printing
Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI
Scheme" [RFC7472].
8.1. Security Conformance Requirements
This section defines the security requirements for IPP Clients and
IPP objects.
8.1.1. Digest Authentication
IPP Clients and Printers SHOULD support Digest Authentication
[RFC7616]. Use of the Message Integrity feature (qop="auth-int") is
OPTIONAL.
Note: Previous versions of this specification required support for
the MD5 algorithms; however, [RFC7616] makes SHA2-256 mandatory to
implement and deprecates MD5, only allowing its use for backwards
compatibility reasons. IPP implementations that support Digest
Authentication MUST support SHA2-256 and SHOULD support MD5 for
backwards compatibility.
Note: The reason that IPP Clients and Printers SHOULD (rather than
MUST) support Digest Authentication is that there is a certain class
of Output Devices where it does not make sense. Specifically, a low-
end device with limited ROM space and low paper throughput may not
need Client Authentication. This class of device typically requires
firmware designers to make trade-offs between protocols and
functionality to arrive at the lowest-cost solution possible.
Factored into the designer's decisions is not just the size of the
code, but also the testing, maintenance, usefulness, and time-to-
market impact for each feature delivered to the customer. Forcing
such low-end devices to provide security in order to claim IPP/1.1
conformance would not make business sense. Print devices that have
high-volume throughput and have available ROM space will typically
provide support for Client Authentication that safeguards the device
from unauthorized access because these devices are prone to a high
loss of consumables and paper if unauthorized access occurs.
8.1.2. Transport Layer Security (TLS)
IPP Clients and Printers SHOULD support Transport Layer Security
(TLS) [RFC5246] [RFC7525] for Server Authentication and Operation
Privacy. IPP Printers MAY also support TLS for Client
Authentication. IPP Clients and Printers MAY support Basic
Authentication [RFC7617] for User Authentication if the channel is
secure, e.g., IPP over HTTPS [RFC7472]. IPP Clients and Printers
SHOULD NOT support Basic Authentication over insecure channels.
The IPP Model and Semantics document [RFC8011] defines two Printer
attributes ("uri-authentication-supported" and "uri-security-
supported") that the Client can use to discover the security policy
of a Printer. That document also outlines IPP-specific security
considerations and is the primary reference for security implications
with regard to the IPP itself.
Note: Because previous versions of this specification did not require
TLS support, this version cannot require it for IPP/1.1. However,
since printing often involves a great deal of sensitive or private
information (medical reports, performance reviews, banking
information, etc.) and network monitoring is pervasive ([RFC7258]),
implementors are strongly encouraged to include TLS support.
Note: Because IPP Printers typically use self-signed X.509
certificates, IPP Clients SHOULD support Trust On First Use (defined
in [RFC7435]) in addition to traditional X.509 certificate
validation.
8.2. Using IPP with TLS
IPP uses the "Upgrading to TLS Within HTTP/1.1" mechanism [RFC2817]
for 'ipp' URIs. The Client requests a secure TLS connection by using
the HTTP "Upgrade" header while the server agrees in the HTTP
response. The switch to TLS occurs either because the server grants
the Client's request to upgrade to TLS or a server asks to switch to
TLS in its response. Secure communication begins with a server's
response to switch to TLS.
IPP uses the "HTTPS: HTTP over TLS" mechanism [RFC2818] for 'ipps'
URIs. The Client and server negotiate a secure TLS connection
immediately and unconditionally.
9. Interoperability with Other IPP Versions
It is beyond the scope of this specification to mandate conformance
with versions of IPP other than 1.1. IPP was deliberately designed,
however, to make supporting other versions easy. IPP objects
(Printers, Jobs, etc.) SHOULD:
o understand any valid request whose major "version-number" is
greater than 0; and
o respond appropriately with a response containing the same
"version-number" parameter value used by the Client in the request
(if the Client-supplied "version-number" is supported) or the
highest "version-number" supported by the Printer (if the Client-
supplied "version-number" is not supported).
IPP Clients SHOULD:
o understand any valid response whose major "version-number" is
greater than 0.
9.1. The "version-number" Parameter
The following are rules regarding the "version-number" parameter (see
Section 3.3):
1. Clients MUST send requests containing a "version-number"
parameter with the highest supported value, e.g., '1.1', '2.0',
etc., and SHOULD try supplying alternate version numbers if they
receive a 'server-error-version-not-supported' error return in a
response. For example, if a Client sends an IPP/2.0 request that
is rejected with the 'server-error-version-not-supported' error
and an IPP/1.1 "version-number", it SHOULD retry by sending an
IPP/1.1 request.
2. IPP objects (Printers, Jobs, etc.) MUST accept requests
containing a "version-number" parameter with a '1.1' value (or
reject the request for reasons other than 'server-error-version-
not-supported').
3. IPP objects SHOULD either accept requests whose major version is
greater than 0 or reject such requests with the 'server-error-
version-not-supported' status-code. See Section 4.1.8 of
[RFC8011].
4. In any case, security MUST NOT be compromised when a Client
supplies a lower "version-number" parameter in a request. For
example, if an IPP/2.0 conforming Printer accepts version '1.1'
requests and is configured to enforce Digest Authentication, it
MUST do the same for a version '1.1' request.
9.2. Security and URI Schemes
The following are rules regarding security, the "version-number"
parameter, and the URI scheme supplied in target attributes and
responses:
1. When a Client supplies a request, the "printer-uri" or "job-uri"
target operation attribute MUST have the same scheme as that
indicated in one of the values of the "printer-uri-supported"
Printer attribute.
2. When the Printer returns the "job-printer-uri" or "job-uri" Job
Description attributes, it SHOULD return the same scheme ('ipp',
'ipps', etc.) that the Client supplied in the "printer-uri" or
"job-uri" target operation attributes in the Get-Job-Attributes
or Get-Jobs request, rather than the scheme used when the Job was
created. However, when a Client requests Job attributes using
the Get-Job-Attributes or Get-Jobs operations, the Jobs and Job
attributes that the Printer returns depends on: (1) the security
in effect when the Job was created, (2) the security in effect in
the query request, and (3) the security policy in force.
3. The Printer MUST enforce its security and privacy policies based
on the owner of the IPP object and the URI scheme and/or
credentials supplied by the Client in the current request.
10. Changes since RFC 2910
The following changes have been made since the publication of
RFC 2910:
o Added references to current IPP extension specifications.
o Added optional support for HTTP/2.
o Added collection attribute syntax from RFC 3382.
o Fixed typographical errors.
o Now reference TLS/1.2 and no longer mandate the TLS/1.0 MTI
ciphersuites.
o Updated all references.
o Updated document organization to follow current style.
o Updated example ipp: URIs to follow guidelines in RFC 7472.
o Updated version compatibility for all versions of IPP.
o Updated HTTP Digest Authentication to optional for Clients.
o Removed references to (Experimental) IPP/1.0 and usage of
http:/https: URLs.
11. References
11.1. Normative References
[PWG5100.12]
Sweet, M. and I. McDonald, "IPP Version 2.0, 2.1, and
2.2", October 2015, <http://ftp.pwg.org/pub/pwg/standards/
std-ipp20-20151030-5100.12.pdf>.
[RFC20] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<http://www.rfc-editor.org/info/rfc20>.
[RFC793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2",
STD 58, RFC 2579, DOI 10.17487/RFC2579, April 1999,
<http://www.rfc-editor.org/info/rfc2579>.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, DOI 10.17487/RFC2817, May 2000,
<http://www.rfc-editor.org/info/rfc2817>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>.
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, DOI 10.17487/RFC2978,
October 2000, <http://www.rfc-editor.org/info/rfc2978>.
[RFC3510] Herriot, R. and I. McDonald, "Internet Printing
Protocol/1.1: IPP URL Scheme", RFC 3510,
DOI 10.17487/RFC3510, April 2003,
<http://www.rfc-editor.org/info/rfc3510>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<http://www.rfc-editor.org/info/rfc7232>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
<http://www.rfc-editor.org/info/rfc7234>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<http://www.rfc-editor.org/info/rfc7235>.
[RFC7472] McDonald, I. and M. Sweet, "Internet Printing Protocol
(IPP) over HTTPS Transport Binding and the 'ipps' URI
Scheme", RFC 7472, DOI 10.17487/RFC7472, March 2015,
<http://www.rfc-editor.org/info/rfc7472>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
<http://www.rfc-editor.org/info/rfc7541>.
[RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
Digest Access Authentication", RFC 7616,
DOI 10.17487/RFC7616, September 2015,
<http://www.rfc-editor.org/info/rfc7616>.
[RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme",
RFC 7617, DOI 10.17487/RFC7617, September 2015,
<http://www.rfc-editor.org/info/rfc7617>.
[RFC8011] Sweet, M. and I. McDonald, "Internet Printing
Protocol/1.1: Model and Semantics", RFC 8011,
DOI 10.17487/RFC8011, January 2017,
<http://www.rfc-editor.org/info/rfc8011>.
11.2. Informative References
[IANA-IPP] IANA, "Internet Printing Protocol (IPP) Registry",
<http://www.iana.org/assignments/ipp-registrations/>.
[PWG5100.3]
Ocke, K. and T. Hastings, "Internet Printing Protocol
(IPP): Production Printing Attributes - Set1", Candidate
Standard 5100.3-2001, February 2001,
<http://ftp.pwg.org/pub/pwg/candidates/
cs-ippprodprint10-20010212-5100.3.pdf>.
[RFC1179] McLaughlin, L., "Line printer daemon protocol", RFC 1179,
DOI 10.17487/RFC1179, August 1990,
<http://www.rfc-editor.org/info/rfc1179>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <http://www.rfc-editor.org/info/rfc7258>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <http://www.rfc-editor.org/info/rfc7435>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
Appendix A. Protocol Examples
A.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 is not supported or their values
are not supported.
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x0002 Print-Job operation-id
0x00000001 1 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes-natural- name
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000b name-length
printer-uri printer-uri name
0x002c value-length
ipp://printer.example.com/ipp/ printer pinetree value
print/pinetree
0x42 nameWithoutLanguage value-tag
type
0x0008 name-length
job-name job-name name
0x0006 value-length
foobar foobar value
0x22 boolean type value-tag
0x0016 name-length
ipp-attribute-fidelity ipp-attribute- name
fidelity
0x0001 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-long-edge two-sided-long-edge value
0x03 end-of-attributes end-of-
attributes-tag
%!PDF... <PDF Document> data
A.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
0x0101 1.1 version-number
0x0000 successful-ok status-code
0x00000001 1 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes- name
natural-language
0x0005 value-length
en-us en-US value
0x41 textWithoutLanguag value-tag
e type
0x000e name-length
status-message status-message name
0x000d value-length
successful-ok successful-ok value
0x02 start job- job-attributes-
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
0x0030 value-length
ipp://printer.example.com/ipp/pr job 147 on value
int/pinetree/147 pinetree
0x23 enum 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
A.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
0x0101 1.1 version-
number
0x040b client-error-attributes-or- status-code
values-not-supported
0x00000001 1 request-id
0x01 start operation-attributes operation-
attributes
tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language type value-tag
0x001b name-length
attributes-natural-language attributes-natural-language name
0x0005 value-length
en-us en-US value
0x41 textWithoutLanguage type value-tag
0x000e name-length
status-message status-message name
0x002f value-length
client-error-attributes-or- client-error-attributes-or- value
values-not-supported values-not-supported
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
0x03 end-of-attributes end-of-
attributes-
tag
A.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
0x0101 1.1 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-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language type value-tag
0x001b name-length
attributes-natural- attributes-natural-language name
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-ignored-or- successful-ok-ignored-or- value
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
0x0030 value-length
ipp://printer.example.com/ job 147 on pinetree value
ipp/print/pinetree/147
0x23 enum 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
A.5. Print-URI Request
The following is an example of Print-URI request with "copies" and
"job-name" parameters:
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x0003 Print-URI operation-id
0x00000001 1 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes-natural- name
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000b name-length
printer-uri printer-uri name
0x002c value-length
ipp://printer.example.com/ipp/ printer pinetree value
print/pinetree
0x45 uri type value-tag
0x000c name-length
document-uri document-uri name
0x0019 value-length
ftp://foo.example.com/foo ftp://foo.example.co value
m/foo
0x42 nameWithoutLanguage value-tag
type
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
A.6. Create-Job Request
The following is an example of Create-Job request with no parameters
and no attributes:
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x0005 Create-Job operation-id
0x00000001 1 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes-natural- name
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000b name-length
printer-uri printer-uri name
0x002c value-length
ipp://printer.example.com/ipp/ printer pinetree value
print/pinetree
0x03 end-of-attributes end-of-
attributes-tag
A.7. Create-Job Request with Collection Attributes
The following is an example of Create-Job request with the "media-
col" collection attribute [PWG5100.3] with the value "media-
size={x-dimension=21000 y-dimension=29700} media-type='stationery'":
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x0005 Create-Job operation-id
0x00000001 1 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes-natural- name
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000b name-length
printer-uri printer-uri name
0x002c value-length
ipp://printer.example.com/ipp/ printer pinetree value
print/pinetree
0x34 begCollection value-tag
0x0009 9 name-length
media-col media-col name
0x0000 0 value-length
0x4a memberAttrName value-tag
0x0000 0 name-length
0x000a 10 value-length
media-size media-size value (member-
name)
0x34 begCollection member-value-tag
0x0000 0 name-length
0x0000 0 member-value-
length
0x4a memberAttrName value-tag
0x0000 0 name-length
0x000b 11 value-length
x-dimension x-dimension value (member-
name)
0x21 integer member-value-tag
0x0000 0 name-length
0x0004 4 member-value-
length
0x00005208 21000 member-value
0x4a memberAttrName value-tag
0x0000 0 name-length
0x000b 11 value-length
y-dimension y-dimension value (member-
name)
0x21 integer member-value-tag
0x0000 0 name-length
0x0004 4 member-value-
length
0x00007404 29700 member-value
0x37 endCollection end-value-tag
0x0000 0 end-name-length
0x0000 0 end-value-length
0x4a memberAttrName value-tag
0x0000 0 name-length
0x000a 10 value-length
media-type media-type value (member-
name)
0x44 keyword member-value-tag
0x0000 0 name-length
0x000a 10 member-value-
length
stationery stationery member-value
0x37 endCollection end-value-tag
0x0000 0 end-name-length
0x0000 0 end-value-length
0x03 end-of-attributes end-of-
attributes-tag
A.8. Get-Jobs Request
The following is an example of Get-Jobs request with parameters but
no attributes:
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x000a Get-Jobs operation-id
0x0000007b 123 request-id
0x01 start operation- operation-
attributes attributes-tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language value-tag
type
0x001b name-length
attributes-natural-language attributes-natural- name
language
0x0005 value-length
en-us en-US value
0x45 uri type value-tag
0x000b name-length
printer-uri printer-uri name
0x002c value-length
ipp://printer.example.com/ipp/ printer pinetree value
print/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-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
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
A.9. Get-Jobs Response
The following is an example of a Get-Jobs response from a previous
request with three Jobs. The Printer returns no information about
the second Job (because of security reasons):
Octets Symbolic Value Protocol field
0x0101 1.1 version-number
0x0000 successful-ok status-code
0x0000007b 123 request-id (echoed
back)
0x01 start operation- operation-attributes-
attributes tag
0x47 charset type value-tag
0x0012 name-length
attributes-charset attributes-charset name
0x0005 value-length
utf-8 UTF-8 value
0x48 natural-language type value-tag
0x001b name-length
attributes-natural- attributes-natural- name
language language
0x0005 value-length
en-us en-US value
0x41 textWithoutLanguage value-tag
type
0x000e name-length
status-message status-message name
0x000d value-length
successful-ok successful-ok value
0x02 start job-attributes job-attributes-tag
(1st 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 job-attributes-tag
(2nd object)
0x02 start job-attributes job-attributes-tag
(3rd object)
0x21 integer type value-tag
0x0006 name-length
job-id job-id name
0x0004 value-length
148 149 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
Acknowledgements
The authors would like to acknowledge the following individuals for
their contributions to the original IPP/1.1 specifications:
Sylvan Butler, Roger deBry, Tom Hastings, Robert Herriot (the
original editor of RFC 2910), Paul Moore, Kirk Ocke, Randy Turner,
John Wenn, and Peter Zehler.
Authors' Addresses
Michael Sweet
Apple Inc.
1 Infinite Loop
MS 111-HOMC
Cupertino, CA 95014
United States of America
Email: msweet@apple.com
Ira McDonald
High North, Inc.
PO Box 221
Grand Marais, MI 49839
United States of America
Phone: +1 906-494-2434
Email: blueroofmusic@gmail.com