INTERNET-DRAFT Robert Herriot (editor) Sun Microsystems Sylvan Butler Hewlett-Packard Paul Moore Microsoft. Randy Turner Sharp Labs July 14, 1997 Internet Printing Protocol/1.0: Protocol Specification draft-ietf-ipp-protocol-00.txt Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months 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". To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract This document is one of a set of documents, which together describe all aspects of a new Internet Printing Protocol (IPP). IPP is an application level protocol that can be used for distributed printing using Internet tools and technology. The protocol is heavily influenced by the printing model introduced in the Document Printing Application (ISO/IEC 10175 DPA) standard. Although DPA specifies both end user and administrative features, IPP version 1.0 is focused only on end user functionality. The full set of IPP documents includes: Internet Printing Protocol: Requirements Internet Printing Protocol/1.0: Model and Semantics Internet Printing Protocol/1.0: Security Internet Printing Protocol/1.0: Protocol Specification Internet Printing Protocol/1.0: Directory Schema The requirements document takes a broad look at distributed printing functionality, and it enumerates real-life scenarios that help to clarify the features that need to be included in a printing protocol for Herriot, Butler, July 14, 1997, [Page 1] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 the Internet. It identifies requirements for three types of users: end users, operators, and administrators. The requirements document calls out a subset of end user requirements that MUST be satisfied in the first version of IPP. Operator and administrator requirements are out of scope for v1.0. The model and semantics document describes a simplified model with abstract objects, their attributes, and their operations. The model introduces a Printer object and a Job object. The Job object supports multiple documents per job. The security document covers potential threats and proposed counters to those threats. The protocol specification is formal document which incorporates the ideas in all the other documents into a concrete mapping using clearly defined data representations and transport protocol mappings that real implementers can use to develop interoperable client and server side components. Finally, the directory schema document shows a generic schema for directory service entries that represent instances of IPP Printers. This document is the "Internet Printing Protocol/1.0: Protocol Specification" document. Herriot, Butler, July 14, 1997, [Page 2] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Table of Contents 1. Introduction........................................................4 2. Conformance Terminology.............................................4 3. Encoding of the Operation Layer....................................4 3.1 Picture of the Encoding.........................................4 3.2 Syntax of Encoding..............................................7 3.3 Version.........................................................8 3.4 Mapping of Operations...........................................8 3.5 Mapping of Status-code..........................................8 3.6 Tags............................................................9 3.7 Name-Lengths...................................................11 3.8 Mapping of Parameter Names.....................................11 3.9 Value Lengths..................................................12 3.10 Mapping of Attribute and Parameter Values.....................13 3.11 Data..........................................................14 4. Encoding of Transport Layer........................................14 4.1 General Headers................................................15 4.2 Request Headers...............................................16 4.3 Response Headers...............................................17 4.4 Entity Headers................................................17 5. Security Considerations............................................18 6. Appendix A: Protocol Examples......................................18 6.1 Print-Job Request..............................................18 6.2 Print-Job Response (successful)................................19 6.3 Print-Job Response (failure)...................................19 6.4 Print-URI Request..............................................20 6.5 Create-Job Request.............................................20 6.6 Get-Jobs Request...............................................21 6.7 Get-Jobs Response..............................................21 7. Appendix B: Requirements without HTTP/1.1 as a Transport Layer.....22 7.1 Additional Parameter-group for HTTP header information.........22 7.2 Chunking of Data...............................................23 7.3 Revised Picture for the Operation Layer........................24 7.4 Revised Syntax for the Operation Layer.........................24 8. Appendix C: Mapping of Each Operation in the Encoding..............25 9. References.........................................................27 10. Author's Address..................................................28 11. Other Participants:...............................................29 Herriot, Butler, July 14, 1997, [Page 3] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 1. Introduction This document contains the rules for encoding IPP operations and describes two layers: the transport layer and the operation layer. The transport layer consists of an HTTP/1.1 request or response. RFC 2068 [27] describes HTTP/1.1. This document specifies the HTTP headers that an IPP implementation supports. The operation layer consists of a message body in an HTTP request or response. The document "Internet Printing Protocol/1.0: Model and Semantics" [21] defines the semantics of such a message body and the supported values. This document specifies the encoding of an IPP operation. The aforementioned document [21] is henceforth referred to as the "IPP model document" 2. Conformance Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [25]. 3. Encoding of the Operation Layer The operation layer SHALL contain a single operation request or operation response. The encoding consists of two primitive types. integers and characters, on which all other data types are built. Every character in this encoding SHALL be a member of the UCS-2 coded character set and SHALL be encoded using UTF-8 Every integer in this encoding SHALL be encoded in binary as a signed integer with big-endian format (also known as "network order" and "most significant byte first"). The number of bytes for an integer SHALL be a power of 2, that is, 1, 2 and 4. The following two sections present the operation layer in two ways . informally through pictures and description . formally through Augmented Backus-Naur Form (ABNF), as specified by draft-ietf-drums-abnf-02.txt [29] 3.1 Picture of the Encoding The encoding for an operation request or response consists of: Herriot, Butler, July 14, 1997, [Page 4] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 ----------------------------------------------- | version | 2 bytes - required ----------------------------------------------- |operation (request) or status-code (response)| 2 bytes - required ----------------------------------------------------------- | parameter-tag | 1 byte | ----------------------------------------------- |- optional | parameter-sequence | m bytes | ----------------------------------------------------------- | attribute-tag | 1 byte | ----------------------------------------------- |-0 or more | attribute-sequence | n bytes | ----------------------------------------------------------- | data-tag | 1 byte - required ----------------------------------------------- | data | q bytes - optional ----------------------------------------------- The parameter-tag and parameter-sequence may be omitted if the operation has no parameters. The attribute-tag and attribute-sequence may be omitted if the operation has no attributes or it may be replicated for an operation that contains attributes for multiple objects. The data is omitted from some operations, but the data-tag is present even when the data is omitted. Note, the parameter-tag, attribute-tag and data-tag are called `delimiter-tags'. A parameter-sequence consists of a sequence of zero or more compound- parameters. ----------------------------------------------- | compound-parameter | r bytes - 0 or more ----------------------------------------------- An attributes-sequence consists of zero or more compound-attributes. ----------------------------------------------- | compound-attribute | s bytes - 0 or more ----------------------------------------------- A compound-parameter consists of a parameter with a single value optionally followed by zero or more additional values. A compound- attribute consists an attribute with a single value followed by zero or more additional values. Each parameter or attribute consists of: Herriot, Butler, July 14, 1997, [Page 5] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 ----------------------------------------------- | value-tag | 1 byte ----------------------------------------------- | name-length (value is u) | 2 bytes ----------------------------------------------- | name | u bytes ----------------------------------------------- | value-length (value is v) | 2 bytes ----------------------------------------------- | value | v bytes ----------------------------------------------- An additional value consists of: ----------------------------------------------------------- | value-tag | 1 byte | ----------------------------------------------- | | name-length (value is 0x0000) | 2 bytes | ----------------------------------------------- |-0 or more | value-length (value is w) | 2 bytes | ----------------------------------------------- | | value | w bytes | ----------------------------------------------------------- Note: an additional value is like a parameter or attribute whose name- length is 0. From the standpoint of a parsing loop, the encoding consists of: ----------------------------------------------- | version | 2 bytes - required ----------------------------------------------- |operation (request) or status-code (response)| 2 bytes - required ----------------------------------------------------------- | tag (delimiter-tag or value-tag) | 1 byte | ----------------------------------------------- |-0 or more | empty or rest of parameter/attribute | x bytes | ----------------------------------------------------------- | data-tag | 2 bytes - required ----------------------------------------------- | data | y bytes - optional ----------------------------------------------- The value of the tag determines whether the bytes following the tag are: . parameters . attributes . data . the remainder of a single parameter or attribute where the tag specifies the type of the value. Herriot, Butler, July 14, 1997, [Page 6] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 3.2 Syntax of Encoding The syntax below is ABNF except `strings of literals' SHALL be case sensitive. For example `a' means lower case `a' and not upper case `A'. In addition, two-byte binary signed integer fields are represented as `%x' values which show their range of values. ipp-message = ipp-request / ipp-response ipp-request = version operation [parameter-tag parameter-sequence ] *(attribute-tag attribute-sequence) data-tag data ipp-response = version status-code [parameter-tag parameter-sequence ] *(attribute-tag attribute-sequence) data-tag data version = major-version minor-version major-version = SIGNED-BYTE ; initially %d1 minor-version = SIGNED-BYTE ; initially %d0 operation = SIGNED-SHORT ; mapping from model defined below status-code = SIGNED-SHORT ; mapping from model defined below parameter-sequence = *compound-parameter attribute-sequence = *compound-attribute compound-parameter = parameter *additional-values compound-attribute = attribute *additional-values parameter = value-tag name-length name value-length value attribute = value-tag name-length name value-length value additional-values = value-tag zero-name-length value-length value name-length = SIGNED-SHORT ; number of octets of `name' name = LALPHA *( LALPHA / DIGIT / "-" / "_" ) value-length = SIGNED-SHORT ; number of octets of `value' value = OCTET-STRING data = OCTET-STRING zero-name-length = %x00.00 ; name-length of 0 parameter-tag = %x01 ; tag of 1 attribute-tag = %x02 ; tag of 2 data-tag = %x03 ; tag of 3 value-tag = %x10..%xFF SIGNED-BYTE = %x00..%xFF SIGNED-SHORT = %x00..%xFF %x00..%xFF DIGIT = "0".."9" LALPHA = "a".."z" BYTE = %x00..%xFF OCTET-STRING = *BYTE The syntax allows a parameter-tag to be present when the parameter- sequence that follows is empty. The same is true for the attribute-tag Herriot, Butler, July 14, 1997, [Page 7] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 and the attribute-sequence that follows. The syntax is defined this way to allow for the response of Get-Jobs where no attributes are returned for some job-objects. Although it is RECOMMENDED that the sender not send a parameter-tag if there are no parameters and not send an attribute-tag if there are no attributes (except in the Get-Jobs response just mentioned), the receiver MUST be able to decode such syntax. 3.3 Version The version SHALL consist of a major and minor version, each of which SHALL be represented by a one byte signed integer. The protocol described in this document SHALL have a major version of 1 (0x01) and a minor version of 0 (0x00). The ABNF for these two bytes SHALL be %x01.00. 3.4 Mapping of Operations The following SHALL be the mapping of operations names to integer values which are encoded as two byte binary signed integers. The operations are defined in the IPP model document The table below includes a range of values for future extensions to the protocol and a separate range for private extensions. It is RECOMMENDED that the private extension values be used for temporary experimental implementations and not for deployed products. Encoding (hex) Operation 0x0 reserved (not used) 0x1 Get-Operations 0x2 Print-Job 0x3 Print-URI 0x4 Validate-Job 0x5 Create-Job 0x6 Send-Document 0x7 Send-URI 0x8 Cancel-Job 0x9 Get-Attributes 0xA Get-Jobs 0xB-0x3FFF reserved for future operations 0x4000-0xFFFF reserved for private extensions 3.5 Mapping of Status-code The following SHALL be the mapping of status-code names to integer values which are encoded as two byte binary signed integers. The status- code names are defined in the IPP model document. Herriot, Butler, July 14, 1997, [Page 8] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 If an IPP status-code is returned, then the HTTP Status-Code MUST be 200 (OK). With any other HTTP Status-Code value, the HTTP response SHALL NOT contain an IPP message-body, and thus no IPP status-code is returned. Note: the integer encodings below were chosen to be similar to corresponding Status-Code values in HTTP. The IPP client and server errors have the same relative offset to their base as corresponding HTTP errors, but the IPP base is a multiple of 0x100 whereas the HTTP base is a multiple of 100. Despite this similarity, the Status-Code returned at the HTTP level will always be different except in the case where `OK' is returned at both levels, 200 (OK) in HTTP and 0 (successful-OK) in IPP. Note: some status-code values, such as client-error-unauthorized, may be returned at the transport (HTTP) level rather than the operation level. ISSUE: as implementations proceed, we will learn what error code need to be supported at the IPP level. Encoding (hex) Status-Code Name 0 successful-OK 0x400 client-error-bad-request 0x401 client-error-unauthorized 0x403 client-error-forbidden 0x404 client-error-not-found 0x405 client-error-method-not-allowed 0x408 client-error-timeout 0x40A client-error-gone 0x40D client-error-request-entity-too-large 0x40E client-error-request-URI-too-long 0x40F client-error-unsupported-document-format 0x410 client-error-attribute-not-supported 0x500 server-error-internal-server-error 0x501 server-error-operation-not-implemented 0x503 server-error-service-unavailable 0x504 server-error-timeout 0x505 server-error-version-not-supported 0x506 server-error-printer-error 0x507 server-error-temporary-error 3.6 Tags There are two kinds of tags: . delimiter tags: delimit major sections of the protocol, namely parameters, attributes and data . value tags: specify the type of each parameter or attribute value The following table specifies the values for the delimiter tags: Herriot, Butler, July 14, 1997, [Page 9] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Tag Value (Hex) Delimiter 0x00 reserved 0x01 parameter-tag 0x02 attribute-tag 0x03 data-tag 0x04-0x0F reserved for future delimiters The remaining tables show values for the value-tag, which is the first octet of a parameter or attribute. The value-tag specifies the type of the value of the parameter or attribute. The value of the value-tag of a parameter or attribute SHALL either be a type value specified in the model document or an "out-of-band" value, such as "unsupported" or "default". If the value of value-tag for a attribute or parameter is not "out-of-band" and differs from the value type specified by the model document, then a server receiving such a request MAY reject it, and a client receiving such a response MAY ignore the attribute or parameter. The following table specifies the "out-of-band" values for the value- tag. Tag Value (Hex) Meaning 0x10 unsupported 0x11 default 0x12-0x1F reserved for future "out-of-band" values. The "unsupported" value SHALL be used in the attribute-sequence of an error response for those attributes which the server does not support. The "default" value is reserved for future use of setting value back to their default value. The following table specifies the integer values for the value-tag Tag Value (Hex) Meaning 0x20 reserved 0x21 integer (up to 4 bytes) 0x22 boolean 0x23 seconds 0x24 milliseconds 0x25 enum 0x26-0x3F reserved for future integer types NOTE: 0x20 is reserved for "generic integer" if should ever be needed. The following table specifies the character-string values for the value- tag Herriot, Butler, July 14, 1997, [Page 10] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Tag Value (Hex) Meaning 0x40 reserved 0x41 text 0x42 name 0x43 filename 0x44 keyword 0x45 uri 0x46 uriScheme 0x47 dateTime 0x48-0x7F reserved for future character string types NOTE: 0x40 is reserved for "generic character-string" if should ever be needed. The values 0x80-0xFF are reserved for future types. 3.7 Name-Lengths The name-length field SHALL consist of a two byte binary signed integer in big endian order. This field SHALL specify the number of octets in the name field which follows the name-length field, excluding the two bytes of the name-length field. If a name-length field has a value of zero, the following name field SHALL be empty, and the following value SHALL be treated as an additional value for the preceding parameter. Within a parameter- sequence, if two parameters have the same name, the first occurrence SHALL be ignored. Within an attribute-sequence, if two attributes have the same name, the first occurrence SHALL be ignored. The zero-length name is the only mechanism for multi-valued parameters and attributes. 3.8 Mapping of Parameter Names Some parameters are encoded in a special position. These parameters are: . "request-URI": The request-URI of each operation in the IPP model document SHALL be specified outside of the operation layer as the request-URI on the Request-Line at the HTTP level, and SHALL not be specified within the operation layer. . "document-content": The parameter named "document-content" in the IPP model document SHALL become the "data" in the operation layer. . "status-code": The parameter named "status-code" in the IPP model document SHALL become the "status-code" field in the operation layer response. ISSUE: Should the request-URI that is the target object of the operation be outside the operation layer, or should it be inside as a parameter and a separate print server URI outside in the HTTP Request-Line? Herriot, Butler, July 14, 1997, [Page 11] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 The remaining parameters are encoded in the parameter-sequence or the attribute-sequence. The parameter-sequence is for actual operation parameters and the attribute-sequence is for object attributes. Of the parameters defined in the IPP model document, some represent an actual operation parameters and others represent a collection of object attributes. A parameter in the IPP model document SHALL represent a collection of object attributes if its name contains the word "attributes" immediately preceded by a space; otherwise it SHALL represent an actual operation parameter. Note, some actual operation parameters contain the word "attributes" preceded by a hyphen ("-"). They are not a collection of attributes. If a parameter in IPP model document represents an actual operation parameter and is not in a special position, it SHALL be encoded in the parameter-sequence using the text name of the parameter specified in the IPP model document. If a parameter in IPP model document represents a collection of object attributes, the attributes SHALL be encoded in the attribute-sequence using the text names of the attributes specified in the IPP model document. The IPP model document specifies the members of such attribute collections, but does not require that all members of a collection be present in an operation. If an operation contain attributes from exactly one object, there SHALL be exactly one attribute-sequence. If an operation contains attributes from more than one object (e.g. Get-Jobs response), the attributes from each object SHALL be in a separate attribute-sequence, such that the attributes from the ith object are in the ith attribute-sequence. See Section 8 "Appendix C: Mapping of Each Operation in the Encoding" for table showing the application of the rules above. 3.9 Value Lengths Each parameter value SHALL be preceded by a two byte binary signed integer in big endian order which SHALL specify the number of octets in the value which follows this length, exclusive of the two bytes specifying the length. For any of the types represented by binary signed integers, the sender MAY encode the value in fewer than the maximum 4 bytes, but the number of bytes for the encoding MUST be a power of two, i.e. 1, 2 or 4, and representation MUST be as a signed integer in the fewer bytes. ISSUE: allowing 4 byte integers to be transmitted in 1 or 2 bytes, at client discretion, may be more trouble than the saved bytes are worth. Do we really want this? Herriot, Butler, July 14, 1997, [Page 12] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 For any of the types represented by character-strings, the sender MUST encode the value with all the characters of the string and without any padding characters. If a value-tag contains an "out-of-band" value, such as "unsupported", the value-length SHALL be 0 and the value empty -- the value has no meaning when the value-tag has an "out-of-band" value. If a server or client receives an operation with a nonzero value-length in this case, it SHALL ignore the value field. 3.10 Mapping of Attribute and Parameter Values The following SHALL be the mapping of attribute and parameter values to their IPP encoding in the value field. The syntax types are defined in the IPP model document. Syntax of Attribute Value Encoding text an octet string where each character is a member of the UCS-2 coded character set and is encoded using UTF-8. The text is encoded in "network byte order" with the first character in the text (according to reading order) being the first character in the encoding. name same as text fileName same as text keyword same as text. Allowed text values are defined in the IPP model document uri same as text uriScheme same as text boolean one binary octet where 0x00 is `false' and 0x01 is `true' integer number of octets is a power of 2 (i.e. 1, 2 or 4). These octets represent a binary signed integer in big endian order (also known as "network byte order" and MSB first). enum same as integer. Allowed integer values are defined in the IPP model document dateTime same as text. Syntax of data and time is defined by ISO 8601 ISSUE: should ISO 8601 be called out in the IPP model document? seconds same as integer milliseconds same as integer 1setOf X encoding according to the rules for a parameter with more than more value. Each value X is encoded according to the rules for encoding its type. rangeOf X same 1setOf X where the number of Herriot, Butler, July 14, 1997, [Page 13] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Syntax of Attribute Value Encoding values is 2. The type of the value in the model document determines the encoding in the value and the value of the value-tag. 3.11 Data The data part SHALL include any data required by the operation 4. Encoding of Transport Layer HTTP/1.1 shall be the transport layer for this protocol. The operation layer has been designed with the assumption that the transport layer contains the following information: . the URI of the target job or printer operation . the total length of the data in the operation layer, either as a single length or as a sequence of chunks each with a length. . the client's language, the character-set and the transport encoding. Each HTTP operation shall use the POST method where the request-URI is the object target of the operation, and where the "Content-Type" of the message-body in each request and response shall be "application/ipp". The message-body shall contain the operation layer and shall have the syntax described in section 3.2 "Syntax of Encoding". A client implementation SHALL adhere to the rules for a client described in RFC 2068. A server implementation SHALL adhere the rules for an origin server described in RFC 2068. In the following sections, there are a tables of all HTTP headers which describe their use in an IPP client or server. The following is an explanation of each column in these tables. . the "header" column contains the name of a header . the "request/client" column indicates whether a client sends the header. . the "request/server" column indicates whether a server supports the header when received. . the "response/server" column indicates whether a server sends the header. . the "response /client" column indicates whether a client supports the header when received. . the "values and conditions" column specifies the allowed header values and the conditions for the header to be present in a request/response. Herriot, Butler, July 14, 1997, [Page 14] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 The table for "request headers" does not have columns for responses, and the table for "response headers" does not have columns for requests. The following is an explanation of the values in the "request/client" and "response/server" columns. . must: the client or server MUST send the header, . must-if: the client or server MUST send the header when the condition described in the "values and conditions" column is met, . may: the client or server MAY send the header . not: the client or server SHOULD NOT send the header. It is not relevant to an IPP implementation. The following is an explanation of the values in the "response/client" and "request/server" columns. . must: the client or server MUST support the header, . may: the client or server MAY support the header . not: the client or server SHOULD NOT support the header. It is not relevant to an IPP implementation. 4.1 General Headers The following is a table for the general headers. ISSUE: an HTTP expert should review these tables for accuracy. General- Request Response Values and Conditions Header Client Server Server Client Cache- must not must not "no-cache" only Control Connection must-if must must-if must "close" only. Both client and server SHOULD keep a connection for the duration of a sequence of operations. The client and server MUST include this header for the last operation in such a sequence. Date may may must may per RFC 1123 [9] Pragma` must not must not "no-cache" only Transfer- must-if must must-if must "chunked" only . Encoding Header MUST be present if Content-Length is absent. Upgrade not not not not Herriot, Butler, July 14, 1997, [Page 15] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 General- Request Response Values and Conditions Header Client Server Server Client Via not not not not 4.2 Request Headers The following is a table for the request headers. Request-Header Client Server Request Values and Conditions Accept may must "application/ipp" only. This value is the default if the client omits it Accept-Charset may must per IANA Character Set registry. ISSUE: is this useful for IPP? Accept- may must empty and per RFC 2068 [27] and IANA Encoding registry for content-codings Accept- may must see RFC 1766 [26]. A server SHOULD Language honor language requested by returning the values status-message, job-state- message and printer-state-reason in one of requested languages. Authorization must- must per RFC 2068. A client MUST send this if header when it receives a 401 "Unauthorized" response and does not receive a "Proxy-Authenticate" header. From not not per RFC 2068. Because RFC recommends sending this header only with the user's approval, it is not very useful Host must must per RFC 2068 If-Match not not If-Modified- not not Since If-None-Match not not If-Range not not If-Unmodified- not not Since Max-Forwards not not Proxy- must- not per RFC 2068. A client MUST send this Authorization if header when it receives a 401 "Unauthorized" response and a "Proxy- Authenticate" header. Range not not Referer not not User-Agent not not Herriot, Butler, July 14, 1997, [Page 16] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 4.3 Response Headers The following is a table for the request headers. Response- Server Client Response Values and Conditions Header Accept-Ranges not not Age not not Location must-if may per RFC 2068. When URI needs redirection. Proxy- not must per RFC 2068 Authenticate Public may may per RFC 2068 Retry-After may may per RFC 2068 Server not not Vary not not Warning may may per RFC 2068 WWW- must-if must per RFC 2068. When a server needs Authenticate to authenticate a client. 4.4 Entity Headers The following is a table for the entity headers. Entity-Header Request Response Values and Conditions Client Server Server Client Allow not not not not Content-Base not not not not Content- may must must must per RFC 2068 and IANA Encoding registry for content codings. Content- may must must must see RFC 1766 [26]. Language Content- must-if must must-if must the length of the Length message-body per RFC 2068. Header MUST be present if Transfer- Encoding is absent.. Content- not not not not Location Content-MD5 may may may may per RFC 2068 Content-Range not not not not Content-Type must must must must "application/ipp" only ETag not not not not Expires not not not not Last-Modified not not not not Herriot, Butler, July 14, 1997, [Page 17] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 5. Security Considerations When utilizing HTTP 1.1 as a transport of IPP, the security considerations outlined in RFC 2068 apply. Specifically, IPP servers can generate a 401 "Unauthorized" response code to request client authentication and IPP clients should correctly respond with the proper "Authorization" header. Both Basic Authentication (RFC 2068) and Digest Authentication (RFC 2069) flavors of authentication should be supported. The server chooses which type(s) of authentication to accept. Digest Authentication is a more secure method, and is always preferred to Basic Authentication. For secure communication (privacy in particular), IPP should be run using a secure communications channel. Both Transport Layer Security - TLS (draft-ietf-tls-protocol-03) and IPSec (RFC 1825) provide necessary features for security. It is possible to combine the two techniques, HTTP 1.1 client authentication (either basic or digest) with secure communications channel (either TLS or IPSec). Together the two are more secure than client authentication and they perform user authentication. Complete discussion of IPP security considerations can be found in the IPP Security document 6. Appendix A: Protocol Examples 6.1 Print-Job Request The following is an example of a Print-Job request with job-name, copies, and sides specified. Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0002 PrintJob operation 0x02 start attributes attribute tag 0x42 name type value-tag 0x0008 name-length job-name job-name name 0x0006 value-length foobar foobar value 0x21 integer type value-tag 0x0005 name-length copies copies name 0x0001 value-length 0x14 20 value 0x44 keyword type value-tag 0x0005 name-length copies sides name 0x0001 value-length two-sided-long-edge two-sided-long-edge value Herriot, Butler, July 14, 1997, [Page 18] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Octets Symbolic Value Protocol field 0x03 start-data data-tag %!PS... data 6.2 Print-Job Response (successful) Here is an example of a Print-Job response which is successful: Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0000 OK (successful) status-code 0x01 start parameters parameter tag 0x41 text type value-tag 0x000E name-length status-message status-message name 0x0002 value-length OK OK value 0x45 uri type value-tag 0x0008 name-length job-uri job-uri name 0x000E value-length http://foo/123 http://foo/123 value 0x02 start attributes attribute tag 0x25 name type value-tag 0x0008 name-length job-state job-state name 0x0001 value-length 0x03 pending value 0x03 start-data data-tag 6.3 Print-Job Response (failure) Here is an example of a Print-Job response which fails because the printer does not support sides and because the value 20 for copies is not supported: Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0400 client-error-bad-request status-code 0x01 start parameters parameter tag 0x41 text type value-tag 0x000E name-length status-message status-message name 0x000D value-length bad-request bad-request value 0x02 start attributes attribute tag 0x21 integer type value-tag Herriot, Butler, July 14, 1997, [Page 19] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Octets Symbolic Value Protocol field 0x0005 name-length copies copies name 0x0001 value-length 0x14 20 value 0x10 unsupported (type) value-tag 0x0005 name-length sides sides name 0x0000 value-length 0x03 start-data data-tag 6.4 Print-URI Request The following is an example of Print-URI request with copies and job- name parameters. Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0003 Print-URI operation 0x01 start-parameters parameter tag 0x45 uri type value-tag 0x000A name-length document-uri document-uri name 0x11 value-length ftp://foo.com/foo ftp://foo.com/foo value 0x02 start-attributes attribute tag 0x42 name type value-tag 0x0008 name-length job-name job-name name 0x0006 value-length foobar foobar value 0x21 integer type value-tag 0x0005 name-length copies copies name 0x0001 value-length 0x01 1 value 0x03 start-data data-tag %!PS... data 6.5 Create-Job Request The following is an example of Create-Job request with no parameters and no attributes Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0005 Create-Job operation 0x03 start-data data-tag Herriot, Butler, July 14, 1997, [Page 20] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 6.6 Get-Jobs Request The following is an example of Get-Jobs request with parameters but no attributes. Octets Symbolic Value Protocol field 0x0100 1.0 version 0x000A Get-Jobs operation 0x01 start-parameters parameter-tag 0x21 integer type value-tag 0x0005 name-length limit limit name 0x0001 value-length 0x32 50 value 0x44 keyword type value-tag 0x0014 name-length requested-attributes requested-attributes name 0x0007 value-length job-uri job-uri value 0x44 keyword type value-tag 0x0000 additional value name-length 0x0008 value-length job-name job-name value 0x03 start-data data-tag 6.7 Get-Jobs Response The following is an of Get-Jobs response from previous request with 3 jobs. The Printer returns no information about the second job. Octets Symbolic Value Protocol field 0x0100 1.0 version 0x0000 OK (successful) status-code 0x01 start-parameters parameter-tag 0x41 text type value-tag 0x000E name-length status-message status-message name 0x0002 value-length OK OK value 0x02 start-attributes (1st object) attribute-tag 0x45 uri type value-tag 0x0007 name-length job-uri job-uri name 0x000E value-length http://foo/123 http://foo/123 value 0x42 name type value-tag 0x0008 name-length job-name job-name name 0x0003 name-length foo foo name 0x02 start-attributes (2nd object) attribute-tag 0x02 start-attributes (3rd object) attribute-tag 0x45 uri type value-tag Herriot, Butler, July 14, 1997, [Page 21] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Octets Symbolic Value Protocol field 0x0007 name-length job-uri job-uri name 0x000E value-length http://foo/124 http://foo/124 value 0x42 name type value-tag 0x0008 name-length job-name job-name name 0x0003 name-length bar bar name 0x03 start-data data-tag 7. Appendix B: Requirements without HTTP/1.1 as a Transport Layer The operation layer defined above assumed certain services would be provided by the HTTP transport layer. Without that layer, information, such as length, request-URI and Content-Encoding are absent. This section specifies the modifications to the operation-layer encoding for raw TCP/IP. The following changes would have to made. All of these changes are upward compatible with the encoding defined in section 3 "Encoding of the Operation Layer". 7.1 Additional Parameter-group for HTTP header information There is an additional header-sequence which is like a parameter- sequence. The header-sequence SHALL appear the before the parameter- sequence, and it SHALL contain the "request-URI" along with relevant HTTP header information, including those shown below. This header- sequence SHALL be preceded by a header-tag to mark that a header- sequence follows. The following table shows the mapping of HTTP headers to parameters in the operation layer. HTTP header or other IPP header name Syntax Type of header concept URI request-URI uri Connection Close-Connection Boolean Accept-Charset Accept-Charset keyword Accept-Encoding Accept-Encoding keyword Accept-Language Accept-Language keyword Content-Encoding Content-Encoding keyword Content-Language Content-Language keyword charset parameter Content-Charset keyword miscellaneous security if needed at this level The first parameter in the header-sequence for a request SHALL be the attribute "request-URI" which is the target object of the operation. Herriot, Butler, July 14, 1997, [Page 22] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Except for Content-Encoding, the headers SHALL take effect at the beginning of the parameter-sequence and apply to the rest of the operation. If a header is Content-Encoding, then the encoding SHALL apply only to the `full-data' or `data-segment's as defined by the syntax below and the resulting decoded data SHALL have the syntax of all octets that follow a header-sequence. The syntax in a section below defines the syntax following a header-sequence to be: [ parameter-tag parameter-sequence ] *(attribute-tag attribute-sequence) data From a decoding point of view, if Content-Encoding is specified, the operation's data is decoded using the algorithm specified by Content- Encoding. The resulting octet stream is parsed as if it were the octets following a header-sequence. NOTE: This rule for Content-Encoding allows a client or server to encode the parameter-sequence and attribute-sequences or to transmit them un- encoded. ISSUE: should the status-message be in the header-sequence instead of the parameter-group for responses? 7.2 Chunking of Data There is a new delimiter-tag called `chunked-data-tag' which denotes that the following data is chunked. Chunked data consists of a sequence of data-segment-lengths and data-segments. A data-segment-length of 0 denotes the end of the data. The following is the informal picture of chunked-data: ----------------------------------------------------------- | data-segment-length | 2 bytes | ----------------------------------------------- |-0 or more | data-segment | n bytes | ----------------------------------------------------------- | 0x0000 (end-of-data) | 2 bytes - required ----------------------------------------------- The syntax for the chunked-data using ABNF is: chunked-data = *data-chunk end-of-data data-chunk = data-segment-length data-segment data-segment-length = SIGNED-SHORT ; number of octets ; of the data in binary data-segment = OCTET-STRING end-of-data = %x00.00 Herriot, Butler, July 14, 1997, [Page 23] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 A data-segment contains fragments of the data. When all the data- segments are concatenated together, they form the complete data. 7.3 Revised Picture for the Operation Layer The encoding for an operation request or response consists of: ----------------------------------------------- | version | 2 bytes - required ----------------------------------------------- |operation (request) or status-code (response)| 2 bytes - required ----------------------------------------------------------- | header-tag | 1 byte | ----------------------------------------------- |- optional | header-sequence | k bytes | ----------------------------------------------------------- | parameter-tag | 1 byte | ----------------------------------------------- |- optional | parameter-sequence | m bytes | ----------------------------------------------------------- | attribute-tag | 1 byte | ----------------------------------------------- |-0 or more | attribute-sequence | n bytes | ----------------------------------------------------------- | data-tag | 1 byte - required ----------------------------------------------- | data | q bytes - optional ----------------------------------------------- The definition of all fields above is the same as defined in section 3.1 "Picture of the Encoding" except . `data' which either has the form defined in the preceding section (7.3 "Revised Picture for the Operation Layer") or the form described in section 3.1 "Picture of the Encoding". . `header-tag' which is new and defined like parameter-tag. . `header-sequence' which is new and defined like parameter-sequence. 7.4 Revised Syntax for the Operation Layer The following is the revised syntax for the operation layer. ipp-message = ipp-request / ipp-response ipp-request = version operation [ header-tag header-sequence ] [ parameter-tag parameter-sequence ] *(attribute-tag attribute-sequence) data ipp-response = version status-code [ header-tag header-sequence ] [ parameter-tag parameter-sequence ] *(attribute-tag attribute-sequence) data Herriot, Butler, July 14, 1997, [Page 24] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 version = major-version minor-version major-version = SIGNED-BYTE ; initially %d1 minor-version = SIGNED-BYTE ; initially %d0 operation = SIGNED-SHORT ; mapping from model defined below status-code = SIGNED-SHORT ; mapping from model defined below header-sequence = *compound-header parameter-sequence = *compound-parameter attribute-sequence = *compound-attribute compound-header = header *(additional-values) compound-parameter = parameter *(additional-values) compound-attribute = attribute *(additional -values) header = value-tag name-length name value-length value parameter = value-tag name-length name value-length value attribute = value-tag name-length name value-length value additional-values = value-tag zero-name-length value-length value name-length = SIGNED-SHORT ; number of octets of `name' name = LALPHA *( LALPHA / DIGIT / "-" / "_" ) value-length = SIGNED-SHORT ; number of octets of `value' value = OCTET-STRING data = (data-tag full-data ) / (chunked-data-tag chunked-data ) full-data = OCTET-STRING chunked-data = *data-chunk END-OF-DATA data-chunk = data-segment-length data-segment data-segment-length = SIGNED-SHORT ; number of octets of the data in binary data-segment = OCTET-STRING zero-name-length = %x00.00 ; name-length of 0 parameter-tag = %x01 ; tag of 1 attribute-tag = %x02 ; tag of 2 data-tag = %x03 ; tag of 3 chunked-data-tag = %x04 ; tag of 4 header-tag = %x05 ; tag of 5 value-tag = %x10..%xFF end-of-data = %x00.00 SIGNED-BYTE = %x00..%xFF SIGNED-SHORT = %x00..%xFF %x00..%xFF DIGIT = "0".."9" LALPHA = "a".."z" BYTE = %x00..%xFF OCTET-STRING = *BYTE 8. Appendix C: Mapping of Each Operation in the Encoding The next three tables show the results of applying the rules above to the operations defined in the IPP model document. There is no Herriot, Butler, July 14, 1997, [Page 25] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 information in these tables that cannot be derived from the rules presented in Section 3.8 "Mapping of Parameter Names". The following table shows the mapping of all IPP model document request parameters (except request-URI) to a parameter-sequence, attribute- sequence or special position in the protocol. Operation parameter- attribute- special position sequence sequence Get-Operations Print-Job job-template document-content attributes Validate-Job job-template or Create-Job attributes Print-URI document-uri job-template attributes Send-Document last-document document document-content attributes Send-URI last-document document document-uri attributes Cancel-Job message Get-Attributes document-format requested- attributes Get-Jobs limit requested- attributes The following table shows the mapping of all IPP model document response parameters to a parameter-sequence, attribute-sequence or special position in the protocol. Operation parameter-sequence attribute-sequence special position Get-Operations status-message status-code supported- operations Print-Job, status-message job-status status-code Print-URI or job-uri attributes Create-Job Send-Document status-message job-status status-code or Send-URI attributes Validate-Job status-message status-code Herriot, Butler, July 14, 1997, [Page 26] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Operation parameter-sequence attribute-sequence special position Cancel-Job status-message status-code Get-Attributes status-message requested attributes status-code Get-Jobs status-message requested attributes status-code (see the Note below) Note for Get-Jobs: there is a separate attribute-sequence containing requested-attributes for each job object in the response The following table shows the mapping of all IPP model document error response parameters to a parameter-sequence, attribute-sequence or special position in the protocol. Those operations omitted don't have special parameters for an error return. Operation parameter- attribute- special position sequence sequence Print-Job, status-message unsupported status-code Print-URI, attributes Validate-Job, Create-Job, Send-Document or Send-URI 9. References [1] Smith, R., Wright, F., Hastings, T., Zilles, S., and Gyllenskog, J., "Printer MIB", RFC 1759, March 1995. [2] Berners-Lee, T, Fielding, R., and Nielsen, H., "Hypertext Transfer Protocol - HTTP/1.0", RFC 1945, August 1995. [3] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", RFC 822, August 1982. [4] Postel, J., "Instructions to RFC Authors", RFC 1543, October 1993. [5] ISO/IEC 10175 Document Printing Application (DPA), June 1996. [6] Herriot, R. (editor), X/Open A Printing System Interoperability Specification (PSIS), August 1995. [7] Kirk, M. (editor), POSIX System Administration - Part 4: Printing Interfaces, POSIX 1387.4 D8, 1994. Herriot, Butler, July 14, 1997, [Page 27] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 [8] Borenstein, N., and Freed, N., "MIME (Multi-purpose Internet Mail Extensions) Part One: Mechanism for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, September, 1993. [9] Braden, S., "Requirements for Internet Hosts - Application and Support", RFC 1123, October, 1989, [10] McLaughlin, L. III, (editor), "Line Printer Daemon Protocol" RFC 1179, August 1990. [11] Berners-Lee, T., Masinter, L., McCahill, M. , "Uniform Resource Locators (URL)", RFC 1738, December, 1994. [20] Wright, F. D., "Internet Printing Protocol: Requirements" [21] Isaacson, S, deBry, R, Hasting, T, Herriot, R, Powell, P, "Internet Printing Protocol/1.0: Model and Semantics" [22] Internet Printing Protocol/1.0: Security [23] Herriot, R, Butler, S, Moore, P, Turner, R, "Internet Printing Protocol/1.0: Protocol Specification" (This document) [24] Carter, K, Isaacson, S, "Internet Printing Protocol/1.0: Directory Schema" [25] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119 , March 1997 [26] H. Alvestrand, " Tags for the Identification of Languages", RFC 1766, March 1995. [27] R Fielding, et al, "Hypertext Transfer Protocol " HTTP/1.1" RFC 2068, January 1997 [28] Marcus Kuhn, "International Standard Date and Time Notation", ISO 8601, http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html [29] D. Crocker et al., "Augmented BNF for Syntax Specifications: ABNF", draft-ietf-drums-abnf-02.txt. 10. Author's Address Robert Herriot (editor) Sun Microsystems Inc. 901 San Antonio.Road, MPK-17 Palo Alto, CA 94303 Phone: 415-786-8995 Fax: 415-786-7077 Email: robert.herriot@eng.sun.com Herriot, Butler, July 14, 1997, [Page 28] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Sylvan Butler Hewlett-Packard 11311 Chinden Blvd. Boise, ID 83714 Phone: 208-396-6000 Fax: 208-396-3457 Email: sbutler@boi.hp.com Paul Moore Microsoft One Microsoft Way Redmond, WA 98053 Phone: 425-936-0908 Fax: 425-93MS-FAX Email: paulmo@microsoft.com Randy Turner Sharp Laboratories 5750 NW Pacific Rim Blvd Camas, WA 98607 Phone: 360-817-8456 Fax: : 360-817-8436 Email: rturner@sharplabs.com IPP Mailing List: ipp@pwg.org IPP Mailing List Subscription: ipp-request@pwg.org IPP Web Page: http://www.pwg.org/ipp/ 11. Other Participants: Chuck Adams - Tektronix Ron Bergman - Data Products Keith Carter - IBM Angelo Caruso - Xerox Jeff Copeland - QMS Roger Debry - IBM Lee Farrell - Canon Sue Gleeson - Digital Charles Gordon - Osicom Brian Grimshaw - Apple Jerry Hadsell - IBM Richard Hart - Digital Tom Hastings - Xerox Stephen Holmstead Zhi-Hong Huang - Zenographics Scott Isaacson - Novell Rich Lomicka - Digital David Kellerman - Northlake Software Herriot, Butler, July 14, 1997, [Page 29] Moore and Turner Expires January 14, 1998 INTERNET-DRAFT IPP/1.0: Protocol Specification July 14, 1997 Robert Kline - TrueSpectra Dave Kuntz - Hewlett-Packard Takami Kurono - Brother Rich Landau - Digital Greg LeClair - Epson Harry Lewis - IBM Tony Liao - Vivid Image David Manchala - Xerox Carl-Uno Manros - Xerox Jay Martin - Underscore Larry Masinter - Xerox Bob Pentecost - Hewlett-Packard Patrick Powell - SDSU Jeff Rackowitz - Intermec Xavier Riley - Xerox Gary Roberts - Ricoh Stuart Rowley - Kyocera Richard Schneider - Epson Shigern Ueda - Canon Bob Von Andel - Allegro Software William Wagner - Digital Products Jasper Wong - Xionics Don Wright - Lexmark Rick Yardumian - Xerox Lloyd Young - Lexmark Peter Zehler - Xerox Frank Zhao - Panasonic Steve Zilles - Adobe Herriot, Butler, July 14, 1997, [Page 30] Moore and Turner Expires January 14, 1998