IPP WG M. Sweet Internet-Draft Apple Inc. Obsoletes: 2910,3382 (if approved) I. McDonald Intended status: Standards Track High North, Inc. Expires: November 28, 2015 May 27, 2015 Internet Printing Protocol/1.1: Encoding and Transport draft-sweet-rfc2910bis-03 Abstract This document is one of a set of documents, which together describe all aspects of a new Internet Printing Protocol (IPP). IPP is an application level protocol that can be used for distributed printing using Internet tools and technologies. This document defines the rules for encoding IPP operations and IPP attributes into a new Internet mime media type called "application/ipp". This document also defines the rules for transporting over HTTP a message body whose Content-Type is "application/ipp". This document defines a new scheme named 'ipp' for identifying IPP printers and jobs. Editor's Note This draft is being submitted in preparation for a so-called "fast track" IETF IPP WG, with drafts being reviewed and edited by the IEEE-ISTO's Printer Working Group IPP WG, in order to correct known editorial issues and advance IPP/1.1 to IETF Internet Standard. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on November 28, 2015. Sweet & McDonald Expires November 28, 2015 [Page 1] Internet-Draft IPP/1.1: Encoding and Transport May 2015 Copyright Notice Copyright (c) 2015 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 2.1. Requirements Language . . . . . . . . . . . . . . . . . . . 4 2.2. Printing Terminology . . . . . . . . . . . . . . . . . . . 4 2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . 5 3. Encoding of the Operation Layer . . . . . . . . . . . . . . . 6 3.1. Picture of the Encoding . . . . . . . . . . . . . . . . . . 7 3.1.1. Request and Response . . . . . . . . . . . . . . . . . . 7 3.1.2. Attribute Group . . . . . . . . . . . . . . . . . . . . . 8 3.1.3. Attribute . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.4. Attribute-with-one-value . . . . . . . . . . . . . . . . 8 3.1.5. Additional-value . . . . . . . . . . . . . . . . . . . . 9 3.1.6. Collection Attribute . . . . . . . . . . . . . . . . . . 10 3.1.7. Member Attributes . . . . . . . . . . . . . . . . . . . . 11 3.1.8. Alternative Picture of the Encoding of a Request Or a Response . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2. Syntax of Encoding . . . . . . . . . . . . . . . . . . . . 13 3.3. Attribute-group . . . . . . . . . . . . . . . . . . . . . . 15 3.4. Required Parameters . . . . . . . . . . . . . . . . . . . . 17 3.4.1. Version-number . . . . . . . . . . . . . . . . . . . . . 17 3.4.2. Operation-id . . . . . . . . . . . . . . . . . . . . . . 17 3.4.3. Status-code . . . . . . . . . . . . . . . . . . . . . . . 17 3.4.4. Request-id . . . . . . . . . . . . . . . . . . . . . . . 18 3.5. Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.5.1. Delimiter Tags . . . . . . . . . . . . . . . . . . . . . 18 3.5.2. Value Tags . . . . . . . . . . . . . . . . . . . . . . . 19 3.6. Name-Length . . . . . . . . . . . . . . . . . . . . . . . . 22 3.7. (Attribute) Name . . . . . . . . . . . . . . . . . . . . . 22 3.8. Value Length . . . . . . . . . . . . . . . . . . . . . . . 22 3.9. (Attribute) Value . . . . . . . . . . . . . . . . . . . . . 23 3.10. Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 4. Encoding of Transport Layer . . . . . . . . . . . . . . . . . 24 4.1. Printer-uri and job-uri . . . . . . . . . . . . . . . . . . 25 5. IPP URI Schemes . . . . . . . . . . . . . . . . . . . . . . . 26 Sweet & McDonald Expires November 28, 2015 [Page 2] Internet-Draft IPP/1.1: Encoding and Transport May 2015 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 7. Internationalization Considerations . . . . . . . . . . . . . 29 8. Security Considerations . . . . . . . . . . . . . . . . . . . 29 8.1. Security Conformance Requirements . . . . . . . . . . . . . 29 8.1.1. Digest Authentication . . . . . . . . . . . . . . . . . . 29 8.1.2. Transport Layer Security (TLS) . . . . . . . . . . . . . 30 8.2. Using IPP with TLS . . . . . . . . . . . . . . . . . . . . 30 9. Interoperability with Other IPP Versions . . . . . . . . . . 31 9.1. The "version-number" Parameter . . . . . . . . . . . . . . 31 9.2. Security and URI Schemes . . . . . . . . . . . . . . . . . 32 10. Changes Since RFC 2910 . . . . . . . . . . . . . . . . . . . 32 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 11.1. Normative References . . . . . . . . . . . . . . . . . . . 33 11.2. Informative References . . . . . . . . . . . . . . . . . . 34 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Appendix A. Protocol Examples . . . . . . . . . . . . . . . . . 35 A.1. Print-Job Request . . . . . . . . . . . . . . . . . . . . . 35 A.2. Print-Job Response (successful) . . . . . . . . . . . . . . 36 A.3. Print-Job Response (failure) . . . . . . . . . . . . . . . 38 A.4. Print-Job Response (success with attributes ignored) . . . 39 A.5. Print-URI Request . . . . . . . . . . . . . . . . . . . . . 41 A.6. Create-Job Request . . . . . . . . . . . . . . . . . . . . 43 A.7. Create-Job Request with Collection Attributes . . . . . . . 43 A.8. Get-Jobs Request . . . . . . . . . . . . . . . . . . . . . 45 A.9. Get-Jobs Response . . . . . . . . . . . . . . . . . . . . . 47 Appendix B. Registration of MIME Media Type Information for "application/ipp" . . . . . . . . . . . . . . . . . 48 Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 49 Appendix D. Change History . . . . . . . . . . . . . . . . . . . 50 D.1. Changes In -03 . . . . . . . . . . . . . . . . . . . . . . 50 D.2. Changes In -02 . . . . . . . . . . . . . . . . . . . . . . 50 D.3. Changes In -01 . . . . . . . . . . . . . . . . . . . . . . 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 MUST 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] Sweet & McDonald Expires November 28, 2015 [Page 3] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 HTTP Authentication: Basic and Digest Access Authentication [RFC2617] IPP implementations MAY 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 document "Internet Printing Protocol/1.1: Model and Semantics" [RFC2911bis] defines the semantics of such a message body and the supported values. This document specifies the encoding of an IPP operation. The aforementioned document [RFC2911bis] is henceforth referred to as the "IPP model document" or simply "model document." 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 the 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]. Sweet & McDonald Expires November 28, 2015 [Page 4] Internet-Draft IPP/1.1: Encoding and Transport May 2015 'ipps' URI: An IPP 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. 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 [ASCII] 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 [1] RFC: Request for Comments TCP: Transmission Control Protocol [RFC793] Sweet & McDonald Expires November 28, 2015 [Page 5] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 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: o informally through pictures and description Sweet & McDonald Expires November 28, 2015 [Page 6] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 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. Sweet & McDonald Expires November 28, 2015 [Page 7] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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, 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 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: Sweet & McDonald Expires November 28, 2015 [Page 8] Internet-Draft IPP/1.1: Encoding and Transport May 2015 ----------------------------------------------- | 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 Sweet & McDonald Expires November 28, 2015 [Page 9] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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'. Sweet & McDonald Expires November 28, 2015 [Page 10] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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'. Sweet & McDonald Expires November 28, 2015 [Page 11] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 specifies 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: Sweet & McDonald Expires November 28, 2015 [Page 12] Internet-Draft IPP/1.1: Encoding and Transport May 2015 ----------------------------------------------- | 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 show 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 syntax below is ABNF [RFC5234] 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. Sweet & McDonald Expires November 28, 2015 [Page 13] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 3.7.2 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 Figure 9: ABNF of IPP Message Format The syntax below defines additional terms that are referenced in this document. This syntax provides an alternate grouping of the delimiter tags. Sweet & McDonald Expires November 28, 2015 [Page 14] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 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. The table below maps the model document group name to value of the "begin-attribute-group-tag" field: Sweet & McDonald Expires November 28, 2015 [Page 15] Internet-Draft IPP/1.1: Encoding and Transport May 2015 +----------------+--------------------------------------------------+ | 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 as described above | | Content | | +----------------+--------------------------------------------------+ Table 1: Group Values For each operation request and response, the model document prescribes the required and optional attribute groups, along with their order. Within each attribute group, the model document prescribes the required and optional attributes, along with their order. When the Model document 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 document, 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: Sweet & McDonald Expires November 28, 2015 [Page 16] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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. 3.4. Required Parameters Some operation elements are called parameters in the model document [RFC2911bis]. 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 this document 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 document. 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 document. The value is encoded as a SIGNED-SHORT and is located in the third and fourth bytes of the encoding of an operation response. Sweet & McDonald Expires November 28, 2015 [Page 17] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 document. 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 attributes 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 Tags The following table specifies the values for the delimiter tags defined in this document: +---------------+---------------------------------------------------+ | Tag Value | Meaning | | (Hex) | | +---------------+---------------------------------------------------+ | 0x00 | reserved for definition in a future standards | | | track document | | 0x01 | "operation-attributes-tag" | | 0x02 | "job-attributes-tag" | | 0x03 | "end-of-attributes-tag" | | 0x04 | "printer-attributes-tag" | | 0x05 | "unsupported-attributes-tag" | | 0x06-0x0f | reserved for future delimiters in standards track | | | documents | +---------------+---------------------------------------------------+ Table 2: Delimiter Tags When a "begin-attribute-group-tag" field occurs in the protocol, it means that zero or more following attributes up to the next delimiter tag are attributes belonging to the attribute group specified by the value of the "begin-attribute-group-tag". For example, if the value Sweet & McDonald Expires November 28, 2015 [Page 18] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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-content 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 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. 3.5.2. Value Tags 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. The following table specifies the "out-of-band" values for the "value-tag" field defined in this document: +-------------+-----------------------------------------------------+ | Tag Value | Meaning | | (Hex) | | +-------------+-----------------------------------------------------+ | 0x10 | unsupported | | 0x11 | reserved for 'default' for definition in a future | | | standards track document | | 0x12 | unknown | | 0x13 | no-value | | 0x14-0x1F | reserved for "out-of-band" values in future | | | standards track documents. | +-------------+-----------------------------------------------------+ Table 3: Out of Band Values The following table specifies the integer values for the "value-tag" field: Sweet & McDonald Expires November 28, 2015 [Page 19] Internet-Draft IPP/1.1: Encoding and Transport May 2015 +-------------+-----------------------------------------------------+ | Tag Value | Meaning | | (Hex) | | +-------------+-----------------------------------------------------+ | 0x20 | reserved for definition in a future standards track | | | document | | 0x21 | integer | | 0x22 | boolean | | 0x23 | enum | | 0x24-0x2F | reserved for integer types for definition in future | | | standards track documents | +-------------+-----------------------------------------------------+ Table 4: Integer Tags 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 defined in this document: +-------------+-----------------------------------------------------+ | 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 | reserved for octetString type definitions in future | | | standards track documents | +-------------+-----------------------------------------------------+ Table 5: octetString Tags The following table specifies the character-string values for the "value-tag" field defined in this document: Sweet & McDonald Expires November 28, 2015 [Page 20] Internet-Draft IPP/1.1: Encoding and Transport May 2015 +------------+------------------------------------------------------+ | Tag Value | Meaning | | (Hex) | | +------------+------------------------------------------------------+ | 0x40 | reserved for definition in a future standards track | | | document | | 0x41 | textWithoutLanguage | | 0x42 | nameWithoutLanguage | | 0x43 | reserved for definition in a future standards track | | | document | | 0x44 | keyword | | 0x45 | uri | | 0x46 | uriScheme | | 0x47 | charset | | 0x48 | naturalLanguage | | 0x49 | mimeMediaType | | 0x4A | memberAttrName | | 0x4B-0x5F | reserved for character string type definitions in | | | future standards track documents | +------------+------------------------------------------------------+ Table 6: String Tags 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 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 0x00000000 to 0x3FFFFFFF are reserved for definition in future standards track documents. The values 0x40000000 to 0x7FFFFFFF are reserved for vendor extensions. Sweet & McDonald Expires November 28, 2015 [Page 21] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 mal-formed (see Section ?? of [RFC2911bis]). 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 document [RFC2911bis] 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 (text) 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, 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" "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 Sweet & McDonald Expires November 28, 2015 [Page 22] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 IPP model document. The table below augments the information in the model document, and defines the syntax types from the model document in terms of the 5 basic types defined in Section 3. 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 | | | 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 4 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 | +----------------------+--------------------------------------------+ Sweet & McDonald Expires November 28, 2015 [Page 23] Internet-Draft IPP/1.1: Encoding and Transport May 2015 | 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 value. | +----------------------+--------------------------------------------+ | rangeOfInteger | Eight octets consisting of 2 SIGNED- | | | INTEGERs. The first SIGNED-INTEGER | | | contains the lower bound and the second | | | SIGNED-INTEGER contains the upper bound. | +----------------------+--------------------------------------------+ | 1setOf X | Encoding according to the rules for an | | | attribute with more than 1 value. Each | | | value X is encoded according to the rules | | | for encoding its type. | +----------------------+--------------------------------------------+ | octetString | OCTET-STRING | +----------------------+--------------------------------------------+ | 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 URI of the target job or printer operation Sweet & McDonald Expires November 28, 2015 [Page 24] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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. 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 [RFC7230]. A printer (server) implementation MUST adhere the rules for an origin server described for HTTP1.1 [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]. 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 4.1. Printer-uri and job-uri All Printer and Job objects are identified by a Uniform Resource Identifier (URI) [RFC3986] so that they can be persistently and unambiguously referenced. 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 allows clients to generate and send a relative URI rather than an absolute URI. A relative URI identifies a Sweet & McDonald Expires November 28, 2015 [Page 25] Internet-Draft IPP/1.1: Encoding and Transport May 2015 resource with the scope of the HTTP server, but does not include scheme, host or port. The following statements characterize how URIs should be 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 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 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 operation MUST be an absolute URI. 5. IPP URI Schemes The IPP URI schemes are 'ipp' [RFC3510] and 'ipps' [RFC7472]. A client and an IPP object (i.e. the server) 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 Sweet & McDonald Expires November 28, 2015 [Page 26] Internet-Draft IPP/1.1: Encoding and Transport May 2015 * printer-uri Each of the above attributes identifies a printer or job object. The ipp-URI 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 URI with a directory service, the printer MUST register an ipp-URI. User interfaces are beyond the scope of this document. But if software exposes the ipp-URI values of any of the above five attributes to a human user, it is REQUIRED that the human see the ipp-URI as is. When a client sends a request, it MUST convert a target ipp-URI to a target http-URL for the HTTP layer according to the following rules: 1. change the 'ipp' scheme to 'http' or 'ipps' scheme to 'https' 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' and 'ipps' schemes. The client MUST use the target http-URL in both the HTTP Request-Line and HTTP headers, as specified by HTTP [RFC7230][RFC2617]. However, the client MUST use the target ipp-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 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 Sweet & McDonald Expires November 28, 2015 [Page 27] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 This section describes the procedures for allocating encoding for the following standards track extensions and vendor extensions to the IPP/1.1 Encoding and Transport document: 1. attribute syntaxes - see Section 6.3 of [RFC2911bis] 2. attribute groups - see Section 6.5 of [RFC2911bis] 3. out-of-band attribute values - see Section 6.7 of [RFC2911bis] These extensions follow the "type2" registration procedures defined in Section ?? of [RFC2911bis]. Extensions registered for use with IPP 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 [RFC2911bis] 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 [RFC2911bis]. The IPP/1.1 Encoding and Transport document may also be extended by an appropriate standards track document that specifies any of the above extensions. Sweet & McDonald Expires November 28, 2015 [Page 28] Internet-Draft IPP/1.1: Encoding and Transport May 2015 7. Internationalization Considerations See the section on "Internationalization Considerations" in the document "Internet Printing Protocol/1.1: Model and Semantics" [RFC2911bis] for information on internationalization. This document adds no additional issues. 8. Security Considerations The IPP Model and Semantics document [RFC2911bis] 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. 8.1. Security Conformance Requirements This section defines the security requirements for IPP clients and IPP objects. 8.1.1. Digest Authentication IPP clients SHOULD support: Digest Authentication [RFC2617]. MD5 and MD5-sess MUST be implemented and supported. Use of the Message Integrity feature is OPTIONAL. IPP Printers SHOULD support: Digest Authentication [RFC2617]. MD5 and MD5-sess MUST be implemented and supported. Use of the Message Integrity feature is OPTIONAL. The reasons that IPP Clients and 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 Sweet & McDonald Expires November 28, 2015 [Page 29] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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. 2. Print devices that have high-volume throughput and have available ROM space are more likely 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. 8.1.2. Transport Layer Security (TLS) IPP Printers SHOULD support Transport Layer Security (TLS) [RFC5246] [RFC7525] for Server Authentication and Operation Privacy. IPP Printers MAY also support TLS for Client Authentication. An IPP Printer MAY support Basic Authentication [RFC2617] for Client Authentication if the channel is secure. The IPP Model and Semantics document [RFC2911bis] 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. 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. Sweet & McDonald Expires November 28, 2015 [Page 30] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 Printer implementations SHOULD: o understand any valid request in the format of IPP/1.0, 1.1, 2.0, 2.1, or 2.2; o respond appropriately with a response containing the same "version-number" parameter value used by the client in the request. IPP Clients SHOULD: o understand any valid response in the format of IPP/1.0, 1.1, 2.0, 2.1, or 2.2. 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. 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 '2' (or reject the request for reasons other than 'server-error-version-not-supported'). See [RFC2911bis] "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. Sweet & McDonald Expires November 28, 2015 [Page 31] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 server 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 server 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. In any case, security MUST NOT be compromised when a client supplies an 'ipp' or other non-secure URL scheme in the target "printer-uri" and "job-uri" operation attributes in a 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 cipher suites. o Updated all references. o Updated document organization to follow current style. o Updated example ipp: URIs to follow RFC 7472 guidelines. Sweet & McDonald Expires November 28, 2015 [Page 32] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 [ASCII] ANSI, "Information Systems - Coded Character Sets - 7-Bit American National Standard Code for Information Interchange (7-Bit ASCII)", June 2007. [PWG5100.12] Sweet, M. and I. McDonald, "IPP/2.0, 2.1, and 2.2", April 2015, . [RFC1903] McCloghrie, K., Case, J., Rose, M., and S. Waldbusser, "Textual Conventions for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1903, January 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2911bis] Sweet, M. and I. McDonald, "Internet Printing Protocol/1.1: Model and Semantics", April 2015, . [RFC3510] Herriot, R. and I. McDonald, "Internet Printing Protocol/1.1: IPP URL Scheme", RFC 3510, April 2003. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. Sweet & McDonald Expires November 28, 2015 [Page 33] Internet-Draft IPP/1.1: Encoding and Transport May 2015 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, June 2014. [RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, June 2014. [RFC7232] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests", RFC 7232, June 2014. [RFC7234] Fielding, R., Nottingham, M., and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Caching", RFC 7234, June 2014. [RFC7235] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, June 2014. [RFC7472] McDonald, I. and M. Sweet, "Internet Printing Protocol (IPP) over HTTPS Transport Binding and the 'ipps' URI Scheme", RFC 7472, March 2015. [RFC7540] Belshe, M., Peon, R., and M. Thompson, "Hypertext Transfer Protocol Version 2 (HTTP/2)", May 2015, . [RFC7541] Peon, R. and H. Ruellan, "HPACK - Header Compression for HTTP/2", May 2015, . [RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. 11.2. Informative References [IANA-CON] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Sweet & McDonald Expires November 28, 2015 [Page 34] Internet-Draft IPP/1.1: Encoding and Transport May 2015 [IANA-IPP] "IANA IPP Registry", . [PWG5100.3] Ocke, K. and T. Hastings, "IPP Production Printing Attributes Set 1", February 2001, . [RFC1179] McLaughlin, L., "Line printer daemon protocol", RFC 1179, August 1990. [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, May 2015. 11.3. URIs [1] http://www.pwg.org/ 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 are 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 0x0008 value-length us-ascii US-ASCII value 0x48 natural-language value-tag type 0x001B name-length attributes-natural-language attributes-natural- name Sweet & McDonald Expires November 28, 2015 [Page 35] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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... 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'. Sweet & McDonald Expires November 28, 2015 [Page 36] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 0x0008 value-length us-ascii US-ASCII 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 123 on value int/pinetree/123 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 Sweet & McDonald Expires November 28, 2015 [Page 37] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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). Sweet & McDonald Expires November 28, 2015 [Page 38] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 0x0008 value-length us-ascii US-ASCII 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 Sweet & McDonald Expires November 28, 2015 [Page 39] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 0x0008 value-length us-ascii US-ASCII 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 Sweet & McDonald Expires November 28, 2015 [Page 40] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 123 on pinetree value ipp/print/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 A.5. Print-URI Request The following is an example of Print-URI request with copies and job- name parameters: Sweet & McDonald Expires November 28, 2015 [Page 41] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 0x0008 value-length us-ascii US-ASCII 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 Sweet & McDonald Expires November 28, 2015 [Page 42] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 0x0008 value-length us-ascii US-ASCII 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 Sweet & McDonald Expires November 28, 2015 [Page 43] Internet-Draft IPP/1.1: Encoding and Transport May 2015 attributes-charset attributes-charset name 0x0008 value-length us-ascii US-ASCII 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 Sweet & McDonald Expires November 28, 2015 [Page 44] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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: Sweet & McDonald Expires November 28, 2015 [Page 45] Internet-Draft IPP/1.1: Encoding and Transport May 2015 Octets Symbolic Value Protocol field 0x0101 1.1 version-number 0x000A Get-Jobs operation-id 0x00000123 0x123 request-id 0x01 start operation- operation- attributes attributes-tag 0x47 charset type value-tag 0x0012 name-length attributes-charset attributes-charset name 0x0008 value-length us-ascii US-ASCII value 0x48 natural-language value-tag type 0x001B name-length attributes-natural-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 Sweet & McDonald Expires November 28, 2015 [Page 46] Internet-Draft IPP/1.1: Encoding and Transport May 2015 A.9. Get-Jobs Response The following is an of Get-Jobs response from previous request with 3 jobs. The Printer returns no information about the second job (because of security reasons): Octets Symbolic Value Protocol field 0x0101 1.1 version-number 0x0000 successful-ok status-code 0x00000123 0x123 request-id (echoed back) 0x01 start operation- operation-attributes- attributes tag 0x47 charset type value-tag 0x0012 name-length attributes-charset attributes-charset name 0x000A value-length ISO-8859-1 ISO-8859-1 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) Sweet & McDonald Expires November 28, 2015 [Page 47] Internet-Draft IPP/1.1: Encoding and Transport May 2015 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 Appendix B. Registration of MIME Media Type Information for "application/ipp" This section is strictly informative. The MIME media type listed in this section should not be re-registered by IANA when this document is published. This appendix contains the information that IANA requires for registering a MIME media type. The information following this paragraph will be forwarded to IANA to register application/ipp whose contents are defined in Section 3 "Encoding of the Operation Layer" in this document: MIME type name: application MIME subtype name: ipp A Content-Type of "application/ipp" indicates an Internet Printing Protocol message body (request or response) whose syntax is described in Section 3 "Encoding of the Operation Layer" of [RFC2910bis], and whose semantics are described in [RFC2911bis]. Required parameters: none Optional parameters: none Encoding considerations: IPP protocol requests/responses MAY contain long lines and ALWAYS contain binary data (for example attribute value lengths). Sweet & McDonald Expires November 28, 2015 [Page 48] Internet-Draft IPP/1.1: Encoding and Transport May 2015 Security considerations: IPP protocol requests/responses do not introduce any security risks not already inherent in the underlying transport protocols. Protocol mixed-version interworking rules in [RFC2911bis] as well as protocol encoding rules in [RFC2910bis] are complete and unambiguous. Interoperability considerations: IPP requests (generated by clients) and responses (generated by servers) MUST comply with all conformance requirements imposed by the normative specifications [RFC2911bis] and [RFC2910bis]. Protocol encoding rules specified in [RFC2910bis] 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 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: [RFC2911bis] Sweet, M., McDonald, I., "Internet Printing Protocol/1.1: Model and Semantics" draft-sweet-rfc2911bis-01.txt, April 26, 2015. [RFC2910bis] Sweet, M., McDonald, I., "Internet Printing Protocol/1.1: Encoding and Transport", draft-sweet-rfc2910bis-01.txt, April 27, 2015. Applications which use this media type: Internet Printing Protocol (IPP) print clients and print servers, communicating using HTTP (see [RFC2910bis]), 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. Appendix C. Acknowledgements The authors would like to acknowledge the following individuals for their contributions to the original IPP/1.1 specification: Robert Herriot (original RFC 2910 editor), Paul Moore, Sylvan Butler, Randy Turner, and John Wenn Sweet & McDonald Expires November 28, 2015 [Page 49] Internet-Draft IPP/1.1: Encoding and Transport May 2015 Appendix D. Change History D.1. Changes In -03 The following changes are in draft-sweet-rfc2910bis-03: o New HTTP/2 RFCs: 7540, 7541 o Added informative reference to UTA BCP (RFC 7525) o Culled list of people in acknowledgements to the original RFC 2910 editors, per IPP F2F. D.2. Changes In -02 The following changes are in draft-sweet-rfc2910bis-02: o Sections 3.1.x: Dropped "Picture of the encoding of" from titles o Section 3.4.1: Added reference to IPP version interoperability section. o Section 3.4.2: Removed paragraph on status-code as operation attribute (already covered in 3.4 intro) and updated HTTP status code 200 name (OK) o Section 3.5: Added reference to IANA IPP registry for tags. o Section 3.8: Mention SIGNED-BYTE is 1 octet. o Section 4.1: Drop mention of URIs not being widely implemented, and that implementations will pass around URLs (not true). Also remove more "need not" text. o Section 6: Fixed references. o Section 8.1.1: Make Digest authentication a SHOULD for clients. o Section 9: Reworked for generic IPP version compatibility. o Section 9.1: Reworked for IPP 2.x compatibility. o Section 9.2: Drop reference to IPP/1.0 and http/https URI schemes. o Appendix A: Updated example URIs to follow IETF and IPP/IPPS URI examples o Global: ipp-URL tp ipp-URI, URL to URI Sweet & McDonald Expires November 28, 2015 [Page 50] Internet-Draft IPP/1.1: Encoding and Transport May 2015 o Global: Don't use conformance language for statements of fact. o Global: Change "NOTE:" to "Note:" for consistency. D.3. Changes In -01 The following changes are in draft-sweet-rfc2910bis-01: o Errata ID 4100: Cleaned up TLS references and recommendations - no longer include cipher suites. o Errata ID 4172: Fixed range of standards-track value tags (to 0x3ffffff not 0x37777777) o Updated RFC references. o Added HTTP/2 references, made it clear that only HTTP/1.1 is required and HTTP/2 is optional. o Added collection attribute encoding from RFC 3382. Authors' Addresses Michael Sweet Apple Inc. 1 Infinite Loop MS 111-HOMC Cupertino, CA 95014 US Email: msweet@apple.com Ira McDonald High North, Inc. PO Box 221 Grand Marais, MI 49839 US Phone: +1 906-494-2434 Email: blueroofmusic@gmail.com Sweet & McDonald Expires November 28, 2015 [Page 51]