Network Working Group R. Herriot, Editor Request for Comments: 2910 Xerox Corporation Obsoletes: 2565 S. Butler Category: Standards Track Hewlett-Packard P. Moore Peerless Systems Networking R. Turner 2wire.com J. Wenn Xerox Corporation September 2000 Internet Printing Protocol/1.1: Encoding and Transport Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved.
AbstractThis 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 Hypertext Transfer Protocol (HTTP) a message body whose Content-Type is "application/ipp". This document defines a new scheme named 'ipp' for identifying IPP printers and jobs.
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/1.1: Model and Semantics [RFC2911] Internet Printing Protocol/1.1: Encoding and Transport (this document) Internet Printing Protocol/1.1: 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/1.1. A few OPTIONAL operator operations have been added to IPP/1.1. 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 specification documents, and gives background and rationale for the IETF working group's major decisions. The document, "Internet Printing Protocol/1.1: 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. The document "Internet Printing Protocol/1.1: 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.
1. Introduction ...................................................4 2. Conformance Terminology ........................................4 3. Encoding of the Operation Layer ...............................4 3.1 Picture of the Encoding ...................................6 3.1.1 Request and Response...................................6 3.1.2 Attribute Group........................................6 3.1.3 Attribute..............................................7 3.1.4 Picture of the Encoding of an Attribute-with-one-value.7 3.1.5 Additional-value.......................................8 3.1.6 Alternative Picture of the Encoding of a Request Or a Response...............................................9 3.2 Syntax of Encoding ........................................9 3.3 Attribute-group ..........................................11 3.4 Required Parameters ......................................12 3.4.1 Version-number........................................12 3.4.2 Operation-id..........................................12 3.4.3 Status-code...........................................12 3.4.4 Request-id............................................13 3.5 Tags .....................................................13 3.5.1 Delimiter Tags........................................13 3.5.2 Value Tags............................................14 3.6 Name-Length ..............................................16 3.7 (Attribute) Name .........................................16 3.8 Value Length .............................................16 3.9 (Attribute) Value ........................................17 3.10 Data .....................................................18 4. Encoding of Transport Layer ...................................18 4.1 Printer-uri and job-uri ..................................19 5. IPP URL Scheme ................................................20 6. IANA Considerations ...........................................22 7. Internationalization Considerations ...........................23 8. Security Considerations .......................................23 8.1 Security Conformance Requirements ........................23 8.1.1 Digest Authentication.................................23 8.1.2 Transport Layer Security (TLS)........................24 8.2 Using IPP with TLS .......................................25 9. Interoperability with IPP/1.0 Implementations .................25 9.1 The "version-number" Parameter ...........................25 9.2 Security and URL Schemes .................................26 10. References ...................................................27 11. Authors' Addresses ...........................................29 12. Other Participants: ..........................................31 13. Appendix A: Protocol Examples ................................33 13.1 Print-Job Request ........................................33 13.2 Print-Job Response (successful) ..........................34 13.3 Print-Job Response (failure) .............................35
13.4 Print-Job Response (success with attributes ignored) .....36 13.5 Print-URI Request ........................................38 13.6 Create-Job Request .......................................39 13.7 Get-Jobs Request .........................................40 13.8 Get-Jobs Response ........................................41 14. Appendix B: Registration of MIME Media Type Information for "application/ipp".............................................42 15. Appendix C: Changes from IPP/1.0 .............................44 16. Full Copyright Statement .....................................45 RFC2616] 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/1.1: Model and Semantics" [RFC2911] defines the semantics of such a message body and the supported values. This document specifies the encoding of an IPP operation. The aforementioned document [RFC2911] is henceforth referred to as the "IPP model document" or simply "model document". Note: the version number of IPP (1.1) and HTTP (1.1) are not linked. They both just happen to be 1.1. RFC2119].
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 value fields and the request-id. The following two sections present the encoding of the operation layer in two ways: - informally through pictures and description - formally through Augmented Backus-Naur Form (ABNF), as specified by RFC 2234 [RFC2234] An operation request or response MUST use the encoding described in these two sections.
section 3.1.1 of the Model document. 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 document). The IPP model document 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 document specifies for each operation request and response whether the "data" field is present or absent.
The "begin-attribute-group-tag" field marks the beginning of an "attribute-group" field and its value identifies the type of attribute group, e.g. Operations Attributes group versus a Job Attributes group. The "begin-attribute-group-tag" field also marks the end of the previous attribute group except for the "begin- attribute-group-tag" field in the first "attribute-group" field of a request or response. The "begin-attribute-group-tag" field acts as an "attribute-group" terminator because an "attribute-group" field cannot nest inside another "attribute-group" field. An "attribute-group" field contains zero or more "attribute" fields. Note, the values of the "begin-attribute-group-tag" field and the "end-of-attributes-tag" field are called "delimiter-tags".
An "attribute-with-one-value" field is encoded with five subfields: The "value-tag" field specifies the attribute syntax, e.g. 0x44 for the attribute syntax 'keyword'. 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". The "name" field contains the textual name of the attribute, e.g. "sides-supported". 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'. The "value" field contains the value of the attribute, e.g. the textual value 'one-sided'.
The "value" field contains the value of the attribute, e.g. the textual value 'two-sided-long-edge'. 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 *attribute-group end-of-attributes-tag data ipp-response = version-number status-code request-id *attribute-group end-of-attributes-tag data
attribute-group = begin-attribute-group-tag *attribute 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 defined below status-code = SIGNED-SHORT ; mapping from model defined below request-id = SIGNED-INTEGER ; whose value is > 0 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 3.7.2 begin-attribute-group-tag = %x00-02 / %04-0F ; see section 3.7.1 end-of-attributes-tag = %x03 ; tag of 3 ; see section 3.7.1 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 The syntax below defines additional terms that are referenced in this document. This syntax provides an alternate grouping of the delimiter tags. delimiter-tag = begin-attribute-group-tag / ; see section 3.7.1 end-of-attributes-tag delimiter-tag = %x00-0F ; see section 3.7.1 begin-attribute-group-tag = %x00 / operation-attributes-tag / job-attributes-tag / printer-attributes-tag / unsupported-attributes-tag / %x06-0F 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
a) A "begin-attribute-group-tag" field with zero following "attribute" fields. b) An expected but missing "begin-attribute-group-tag" field. When the Model document 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, for 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. RFC2911]. They MUST be encoded in a special position and they MUST NOT appear as operation attributes. These parameters are described in the subsections below.
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.
The "end-of-attributes-tag" (value 0x03) MUST occur exactly once in an operation. It MUST be the last "delimiter-tag". If the operation has a document-content group, the document data in that group MUST follow 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 document. For further details, see section 3.7 "(Attribute) Name" and 13 "Appendix A: Protocol Examples". 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 that there is an entire attribute group that it doesn't understand as opposed to a single value that it doesn't understand.
NOTE: 0x20 is reserved for "generic integer" if it should ever be needed. The following table specifies the octetString values for the "value- tag" field: Tag Value (Hex) Meaning 0x30 octetString with an unspecified format 0x31 dateTime 0x32 resolution 0x33 rangeOfInteger 0x34 reserved for definition in a future IETF standards track document 0x35 textWithLanguage 0x36 nameWithLanguage 0x37-0x3F reserved for octetString type definitions in future IETF standards track documents The following table specifies the character-string values for the "value-tag" field: Tag Value (Hex) Meaning 0x40 reserved for definition in a future IETF standards track document 0x41 textWithoutLanguage 0x42 nameWithoutLanguage 0x43 reserved for definition in a future IETF standards track document 0x44 keyword 0x45 uri 0x46 uriScheme 0x47 charset 0x48 naturalLanguage 0x49 mimeMediaType 0x4A-0x5F reserved for character string type definitions in future IETF standards track documents 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 type definitions in IETF 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 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. Values from 0x00 to 0x37777777 are reserved for definition in future IETF standard track documents. The values 0x40000000 to 0x7FFFFFFF are reserved for vendor extensions. RFC2911] section 3.1.3). The zero-length name is the only mechanism for multi-valued attributes. RFC2911] specifies such names.
For "out-of-band" "value-tag" fields 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. 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
Syntax of Attribute Encoding Value 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 1903 [RFC1903]. 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 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 attribute syntax type of the value determines its encoding and the value of its "value-tag". RFC2616] 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. 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 [RFC2616]. A printer (server) implementation MUST adhere the rules for an origin server described for HTTP1.1 [RFC2616]. 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 [RFC2616]. An HTTP server MUST support chunking for IPP requests, and an IPP client MUST support chunking for IPP responses according to HTTP/1.1 [RFC2616]. Note: this rule causes a conflict with non-compliant implementations of HTTP/1.1 that don't support chunking for POST methods, and this rule may cause a conflict with non-compliant implementations of HTTP/1.1 that don't support chunking for CGI scripts. RFC2396] so that they can be persistently and unambiguously referenced. 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 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 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. However, a Printer NEED NOT verify that the two URLs reference the same IPP object, and NEED NOT take any action if it determines the two URLs to be different. 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. RFC2616][RFC2617] rules for constructing a Request-Line and HTTP headers. The mapping is simple because the 'ipp' scheme implies all of the same protocol semantics as that of the 'http' scheme
[RFC2616], except that it represents a print service and the implicit (default) port number that clients use to connect to a server is port 631. In the remainder of this section the term 'ipp-URL' means a URL whose scheme is 'ipp' and whose implicit (default) port is 631. The term 'http-URL' means a URL whose scheme is 'http', and the term 'https- URL' means a URL whose scheme is 'https', A client and an IPP object (i.e. the server) MUST support the ipp-URL value in the following IPP attributes. job attributes: job-uri job-printer-uri printer attributes: printer-uri-supported operation attributes: job-uri printer-uri Each of the above attributes identifies a printer or job object. The ipp-URL is intended as the value of the attributes in this list, and for no other attributes. 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 URL with a directory service, the printer MUST register an ipp-URL. User interfaces are beyond the scope of this document. But if software exposes the ipp-URL values of any of the above five attributes to a human user, it is REQUIRED that the human see the ipp-URL as is. When a client sends a request, it MUST convert a target ipp-URL to a target http-URL for the HTTP layer according to the following rules: 1. change the 'ipp' scheme to 'http' 2. add an explicit port 631 if the URL does not contain an explicit port. Note: port 631 is the IANA assigned Well Known Port for the 'ipp' scheme. The client MUST use the target http-URL in both the HTTP Request- Line and HTTP headers, as specified by HTTP [RFC2616] [RFC2617] . However, the client MUST use the target ipp-URL 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-URL
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-URL "ipp://myhost.com/myprinter/myqueue", it opens a TCP connection to port 631 (the ipp implicit port) on the host "myhost.com" and sends the following data: POST /myprinter/myqueue HTTP/1.1 Host: myhost.com:631 Content-type: application/ipp Transfer-Encoding: chunked ... "printer-uri" "ipp://myhost.com/myprinter/myqueue" (encoded in application/ipp message body) ... As another example, when an IPP client sends the same request as above via a proxy "myproxy.com", it opens a TCP connection to the proxy port 8080 on the proxy host "myproxy.com" and sends the following data: POST http://myhost.com:631/myprinter/myqueue HTTP/1.1 Host: myhost.com:631 Content-type: application/ipp Transfer-Encoding: chunked ... "printer-uri" "ipp://myhost.com/myprinter/myqueue" (encoded in application/ipp message body) ... The proxy then connects to the IPP origin server with headers that are the same as the "no-proxy" example above. RFC2911] section 6.3 2. attribute groups - see [RFC2911] section 6.5 3. out-of-band attribute values - see [RFC2911] section 6.7
These extensions follow the "type2" registration procedures defined in [RFC2911] section 6. Extensions registered for use with IPP/1.1 are OPTIONAL for client and IPP object conformance to the IPP/1.1 Encoding and Transport document. These extension procedures are aligned with the guidelines as set forth by the IESG [IANA-CON]. The [RFC2911] Section 11 describes how to propose new registrations for consideration. IANA will reject registration proposals that leave out required information or do not follow the appropriate format described in [RFC2911] Section 11. The IPP/1.1 Encoding and Transport document may also be extended by an appropriate RFC that specifies any of the above extensions. RFC2911] for information on internationalization. This document adds no additional issues. RFC2911] 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. RFC2617]. MD5 and MD5-sess MUST be implemented and supported. The Message Integrity feature NEED NOT be used.
IPP Printers SHOULD support: Digest Authentication [RFC2617]. MD5 and MD5-sess MUST be implemented and supported. The Message Integrity feature NEED NOT be used. The reasons that IPP Printers SHOULD (rather than MUST) support Digest Authentication are: 1. While Client Authentication is important, there is a certain class of printer 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 and could potentially stall the adoption of the standard. 2. Print devices that have high-volume throughput and have available ROM space have a compelling argument to provide support for Client Authentication that safeguards the device from unauthorized access. These devices are prone to a high loss of consumables and paper if unauthorized access should occur. RFC2246] for Server Authentication and Operation Privacy. IPP Printers MAY also support TLS for Client Authentication. If an IPP Printer supports TLS, it MUST support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite as mandated by RFC 2246 [RFC2246]. All other cipher suites are OPTIONAL. An IPP Printer MAY support Basic Authentication (described in HTTP/1.1 [RFC2617]) for Client Authentication if the channel is secure. TLS with the above mandated cipher suite can provide such a secure channel. If a IPP client supports TLS, it MUST support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite as mandated by RFC 2246 [RFC2246]. All other cipher suites are OPTIONAL.
The IPP Model and Semantics document 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 should be the primary reference for security implications with regard to the IPP protocol itself. For backward compatibility with IPP version 1.0, IPP clients and printers may also support SSL3 [ssl]. This is in addition to the security required in this document. RFC2817]. An initial IPP request never uses TLS. 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. section 3.3): 1. Clients MUST send requests containing a "version-number" parameter with a '1.1' value and SHOULD try supplying alternate version numbers if they receive a 'server-error-version-not- supported' error return in a response.
2. IPP objects 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. It is recommended that IPP objects accept any request with the major version '1' (or reject the request for reasons other than 'server-error-version-not-supported'). See [RFC2911] "versions" sub-section. 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/1.1 conforming Printer object accepts version '1.0' requests and is configured to enforce Digest Authentication, it MUST do the same for a version '1.0' request. RFC2911] "Generic Directory Schema" Appendix), then it also register an http-URL for interoperability with IPP/1.0 clients (see section 9). 4. In any case, security MUST NOT be compromised when a client supplies an 'http' or other non-secure URL scheme in the target "printer-uri" and "job-uri" operation attributes in a request.
[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. [IANA-CON] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [ipp-iig] Hastings, Tom, et al., "Internet Printing Protocol/1.1: Implementer's Guide", Work in Progress. [RFC822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, August 1982. [RFC1123] Braden, S., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October, 1989. [RFC1179] McLaughlin, L. III, (editor), "Line Printer Daemon Protocol", RFC 1179, August 1990. [RFC2223] Postel, J. and J. Reynolds, "Instructions to RFC Authors", RFC 2223, October 1997. [RFC1738] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform Resource Locators (URL)", RFC 1738, December 1994. [RFC1759] Smith, R., Wright, F., Hastings, T., Zilles, S. and J. Gyllenskog, "Printer MIB", RFC 1759, March 1995. [RFC1766] Alvestrand, H., "Tags for the Identification of Languages", RFC 1766, March 1995. [RFC1808] Fielding, R., "Relative Uniform Resource Locators", RFC 1808, June 1995. [RFC1903] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Textual Conventions for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1903, January 1996. [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996.
[RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extension (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2184] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2184, August 1997. [RFC2234] Crocker, D. and P. Overall, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol", RFC 2246. January 1999. [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [RFC2565] Herriot, R., Butler, S., Moore, P. and R. Turner, "Internet Printing Protocol/1.0: Encoding and Transport", RFC 2565, April 1999. [RFC2566] deBry, R., Hastings, T., Herriot, R., Isaacson, S. and P. Powell, "Internet Printing Protocol/1.0: Model and Semantics", RFC 2566, April 1999. [RFC2567] Wright, D., "Design Goals for an Internet Printing Protocol", RFC2567, April 1999. [RFC2568] Zilles, S., "Rationale for the Structure and Model and Protocol for the Internet Printing Protocol", RFC 2568, April 1999. [RFC2569] Herriot, R., Hastings, T., Jacobs, N. and J. Martin, "Mapping between LPD and IPP Protocols", RFC 2569, April 1999. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol - HTTP/1.1", RFC 2616, June 1999. [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A. and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within HTTP/1.1", RFC 2817, May 2000. [RFC2910] Herriot, R., Butler, S., Moore, P., Turner, R. and J. Wenn, "Internet Printing Protocol/1.1: Encoding and Transport", RFC 2910, September 2000. [RFC2911] Hastings, T., Herriot, R., deBry, R., Isaacson, S. and P. Powell, "Internet Printing Protocol/1.1: Model and Semantics", RFC 2911, September 2000. [SSL] Netscape, The SSL Protocol, Version 3, (Text version 3.02), November 1996.
Randy Turner 2Wire, Inc. 694 Tasman Dr. Milpitas, CA 95035 Phone: 408-546-1273 John Wenn Xerox Corporation 737 Hawaii St El Segundo, CA 90245 Phone: 310-333-5764 Fax: 310-333-5514 EMail: email@example.com IPP Web Page: http://www.pwg.org/ipp/ IPP Mailing List: firstname.lastname@example.org To subscribe to the ipp mailing list, send the following email: 1) send it to email@example.com 2) leave the subject line blank 3) put the following two lines in the message body: subscribe ipp end
Bob Setterbo - Adobe Gail Songer - Peerless Hideki Tanaka - Cannon Information Devon Taylor - Novell, Inc. Systems Mike Timperman - Lexmark Atsushi Uchino - Epson Shigeru Ueda - Canon Bob Von Andel - Allegro Software William Wagner - NetSilicon/DPI Jim Walker - DAZEL Chris Wellens - Interworking Labs Trevor Wells - Hewlett Packard Craig Whittle - Sharp Labs Rob Whittle - Novell, Inc. Jasper Wong - Xionics Don Wright - Lexmark Michael Wu - Heidelberg Digital Rick Yardumian - Xerox Michael Yeung - Canon Information Lloyd Young - Lexmark Systems Atsushi Yuki - Kyocera Peter Zehler - Xerox William Zhang - Canon Information Frank Zhao - Panasonic Systems Steve Zilles - Adobe Rob Zirnstein - Canon Information Systems
Octets Symbolic Value Protocol field 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
Octets Symbolic Value Protocol field successful-ok successful-ok value 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 0x0019 value-length ipp://forest/ job 123 on pinetree value pinetree/123 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
Octets Symbolic Value Protocol field 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- status-message name message 0x002F value-length client-error- value attributes- values-not-supported or-values- client-error-attributes-or- 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
Octets Symbolic Value Protocol field 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 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 0x0019 value-length ipp://forest/ job 123 on pinetree value pinetree/123
Octets Symbolic Value Protocol field 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
Octets Symbolic Value Protocol field /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
Octets Symbolic Value Protocol field inetree 0x03 end-of-attributes end-of-attributes-tag
Octets Symbolic Value Protocol field 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
Octets Symbolic Value Protocol field 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 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 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/1.1, whose syntax is described in Section 3 "Encoding of the Operation Layer" of [RFC2910], and whose semantics are described in [RFC2911]. Required parameters: none Optional parameters: none Encoding considerations: IPP/1.1 protocol requests/responses MAY contain long lines and ALWAYS contain binary data (for example attribute value lengths). Security considerations: IPP/1.1 protocol requests/responses do not introduce any security risks not already inherent in the underlying transport protocols. Protocol mixed-version interworking rules in [RFC2911] as well as protocol encoding rules in [RFC2910] are complete and unambiguous. Interoperability considerations: IPP/1.1 requests (generated by clients) and responses (generated by servers) MUST comply with all conformance requirements imposed by the normative specifications [RFC2911] and [RFC2910]. Protocol encoding rules specified in [RFC2910] 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/1.1 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 specifications: [RFC2911] Hastings, T., Herriot, R., deBry, R., Isaacson, S. and P. Powell, "Internet Printing Protocol/1.1: Model and Semantics", RFC 2911, September 2000. [RFC2910] Herriot, R., Butler, S., Moore, P., Turner, R. and J. Wenn, "Internet Printing Protocol/1.1: Encoding and Transport", RFC 2910, September 2000.
Applications which use this media type: Internet Printing Protocol (IPP) print clients and print servers, communicating using HTTP/1.1 (see [RFC2910]), 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: Tom Hastings Xerox Corporation 737 Hawaii St. ESAE-231 El Segundo, CA Phone: 310-333-6413 Fax: 310-333-5514 EMail: firstname.lastname@example.org or Robert Herriot Xerox Corporation 3400 Hillview Ave., Bldg #1 Palo Alto, CA 94304 Phone: 650-813-7696 Fax: 650-813-6860 EMail: email@example.com Intended usage: COMMON RFC2565] with the follow changes: 1. Attributes values that identify a printer or job object use a new 'ipp' scheme. The 'http' and 'https' schemes are supported only for backward compatibility. See section 5. 2. Clients MUST support of Digest Authentication, IPP Printers SHOULD support Digest Authentication. See Section 8.1.1 3. TLS is recommended for channel security. In addition, SSL3 may be supported for backward compatibility. See Section 8.1.2
4. It is recommended that IPP/1.1 objects accept any request with major version number '1'. See section 9.1. 5. IPP objects SHOULD return the URL scheme requested for "job- printer-uri" and "job-uri" Job Attributes, rather than the URL scheme used to create the job. See section 9.2. 6. The IANA and Internationalization sections have been added. The terms "private use" and "experimental" have been changed to "vendor extension". The reserved allocations for attribute group tags, attribute syntax tags, and out-of-band attribute values have been clarified as to which are reserved to future IETF standards track documents and which are reserved to vendor extension. Both kinds of extensions use the type2 registration procedures as defined in [RFC2911]. 7. Clarified that future "out-of-band" value definitions may use the value field if additional information is needed.
Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.