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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 RFC 7472

Network Working Group                                       Ira McDonald
INTERNET-DRAFT                                            High North Inc
Updates: 2910, 2911 (if approved)                          Michael Sweet
Intended Status: Standards Track                               Apple Inc
Expires: 18 June 2015                                   18 December 2014


         IPP over HTTPS Transport Binding and 'ipps' URI Scheme
                 draft-mcdonald-ipps-uri-scheme-18.txt


Abstract

   This document defines the Internet Printing Protocol (IPP) over HTTPS
   transport binding and the corresponding 'ipps' URI scheme, that is
   used to designate the access to the network location of a secure IPP
   print service or a network resource managed by such a service.

   This document defines an alternate IPP transport binding to that
   defined in the original IPP URL Scheme (RFC 3510), but this document
   does not update or obsolete RFC 3510.

   This document updates RFC 2910 and RFC 2911.


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), its areas,
   and its working groups.  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on 18 June 2015.


Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.


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   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
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
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   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.






























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                           Table of Contents

1.  Introduction ...............................................       4
  1.1.  Structure of this Document .............................       4
  1.2.  Rationale for this Document ............................       5
2.  Conventions Used in this Document ..........................       5
  2.1.  Printing Terminology ...................................       5
3.  IPP over HTTPS Transport Binding ...........................       6
4.  Definition of 'ipps' URI Scheme ............................       7
  4.1.  Applicability of 'ipps' URI Scheme .....................       7
  4.2.  Syntax of 'ipps' URI Scheme ............................       7
  4.3.  Associated Port for 'ipps' URI Scheme ..................       9
  4.4.  Character Encoding of 'ipps' URI Scheme ................       9
  4.5.  Examples of 'ipps' URI .................................       9
  4.6.  Comparisons of 'ipps' URI ..............................      10
5.  IANA Considerations ........................................      10
6.  Security Considerations ....................................      12
  6.1.  Problem Statement ......................................      12
    6.1.1.  Targets of Attacks .................................      12
    6.1.2.  Layers of Attacks ..................................      12
  6.2.  Attacks and Defenses ...................................      13
    6.2.1.  Faked 'ipps' URI ...................................      13
    6.2.2.  Unauthorized Access by IPP Client ..................      13
    6.2.3.  Compromise at Application Layer Gateway ............      14
    6.2.4.  No Client Authentication for 'ipps' URI ............      14
  6.3.  TLS Version Requirements ...............................      14
7.  Acknowledgments ............................................      14
8.  References .................................................      15
  8.1.  Normative References ...................................      15
  8.2.  Informative References .................................      16
9.  Appendix A - Abbreviations .................................      17
10.  Authors' Addresses ........................................      18




















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1.  Introduction

   This document defines the Internet Printing Protocol (IPP) over HTTPS
   transport binding and the corresponding 'ipps' URI scheme, that is
   used to designate the access to the network location of a secure IPP
   print service or a network resource managed by such a service.

   This document has been submitted to the IETF by the Internet Printing
   Protocol Working Group of the IEEE-ISTO Printer Working Group, as
   part of their PWG IPP Everywhere (PWG 5100.14) project for secure
   mobile printing with vendor-neutral Client software.

   This document defines an alternate IPP transport binding to that
   defined in the original IPP URL Scheme [RFC3510], but this document
   does not update or obsolete [RFC3510].

   This document updates:
   a) IPP/1.1 Encoding and Transport [RFC2910], by extending section 4
      'Encoding of the Transport Layer', section 5 'IPP URL Scheme', and
      section 8.2 'Using IPP with TLS' to add the new standard URI
      scheme of 'ipps' for IPP Printers; and
   b) IPP/1.1 Model and Semantics [RFC2911], by extending section 4.1.6
      'uriScheme' and section 4.4.1 'printer-uri-supported' to add the
      new standard URI scheme of 'ipps' for IPP Printers.

   The following versions of IPP are currently defined:
   a) 1.0 in [RFC2566] (obsolete);
   b) 1.1 in [RFC2911];
   c) 2.0 in [PWG5100.12];
   d) 2.1 in [PWG5100.12]; and
   e) 2.2 in [PWG5100.12].

   Overview information about IPP is available in section 1 of RFC 2911
   [RFC2911], section 1 of RFC 3196 [RFC3196], and section 1 of PWG IPP
   Version 2.0 Second Edition [PWG5100.12].



1.1.  Structure of this Document

   This document contains the following sections:

   Section 2 defines the conventions and terms used throughout the
   document.

   Section 3 defines the IPP over HTTPS transport binding.

   Section 4 defines the 'ipps' URI scheme.


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   Sections 5 and 6 contain IANA and security considerations,
   respectively.

   Section 7 contains acknowledgments.

   Section 8 contains references.



1.2.  Rationale for this Document

   The 'ipps' URI scheme was defined for the following reasons:

   1) Some existing IPP Client and IPP Printer implementations of
      Upgrading to TLS Within HTTP/1.1 [RFC2817] are flawed and
      unreliable, although this is not due to specification defects in
      [RFC2817] itself.

   2) Some existing IPP Client and IPP Printer implementations of HTTP
      Upgrade [RFC2817] do not perform upgrade at the beginning of every
      HTTP [RFC7230] connection, but instead only shift to secure IPP
      for selected IPP operations (inherently dangerous behavior on the
      same underlying TCP [TCPROAD] connection).

   3) IPP Printer server-mandated HTTP Upgrade [RFC2817] can still lead
      to exposure of IPP Client data if the Expect request header is not
      used - basically the IPP Client can send its whole Print-Job
      request before the IPP Printer has a chance to respond and say,
      "Wait!  You need to encrypt first!"



2.  Conventions Used in this Document

   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 [RFC2119].


2.1.  Printing Terminology

   The reader of this document needs to be familiar with the printing
   terms defined in IPP/1.1 Model and Semantics [RFC2911] as well as the
   following:

   IPP Client:  The software (on some hardware platform) that submits
   IPP Job creation and IPP Printer and IPP Job management operations
   via the IPP over HTTP transport binding defined in the IPP/1.1
   Encoding and Transport [RFC2910] and/or the IPP over HTTPS transport
   binding defined in section 3 of this specification to an IPP Printer

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   (print spooler, print gateway, or physical printing device).

   IPP Job:  The set of attributes and documents for one print job
   instantiated in an IPP Printer.

   IPP Job object:  Synonym for IPP Job.

   IPP Printer:  The software (on some hardware platform) that receives
   IPP Job creation and IPP Printer and IPP Job management operations
   via the IPP over HTTP transport binding defined in the IPP/1.1
   Encoding and Transport [RFC2910] and/or the IPP over HTTPS transport
   binding defined in section 3 of this specification from an IPP
   Client.

   IPP Printer object:  Synonym for IPP Printer.

   'ipps' URI:  A URI using the 'ipps' URI scheme defined in section 4
   of this specification.




3.  IPP over HTTPS Transport Binding

   This document defines the following alternate IPP over HTTPS
   transport binding for the abstract protocol defined in IPP/1.1 Model
   and Semantics [RFC2911] and IEEE-ISTO PWG IPP Version 2.0 Second
   Edition [PWG5100.12].

   When using an 'ipps' URI, an IPP Client MUST establish an IPP
   application layer connection according to the following sequence:

   1) The IPP Client selects an 'ipps' URI value from
      "printer-uri-supported" Printer attribute [RFC2911], a directory
      entry, discovery info, a web page, etc.;

   2) The IPP Client converts the 'ipps' URI to an 'https' URI [RFC7230]
      (replacing 'ipps' with 'https' and inserting the port number from
      the URI or port 631 if the URI doesn't include an explicit port
      number);

   3) The IPP Client establishes an HTTPS [RFC7230] secure session layer
      connection to the target endpoint; and

   4) The IPP Client sends requests to and receives responses from the
      target IPP application layer resource over the HTTPS [RFC7230]
      secure session layer connection using the POST method defined in
      [RFC7231].




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4.  Definition of 'ipps' URI Scheme



4.1.  Applicability of 'ipps' URI Scheme

   Per PWG IPP Everywhere [PWG5100.14], in IPP protocol exchanges, the
   'ipps' URI scheme MUST only be used:
   a) To specify absolute URI for IPP secure print services and their
      their associated network resources;
   b) To specify the use of the abstract protocol defined in IPP/1.1
      Model and Semantics [RFC2911] and IEEE-ISTO PWG IPP Version 2.0
      Second Edition [PWG5100.12]; and
   c) To specify the use of the transport binding defined in this
      document.

   The 'ipps' URI scheme allows an IPP Client to choose an appropriate
   IPP secure print service (for example, from a directory).  The IPP
   Client can establish an HTTPS connection to the specified IPP secure
   print service.  The IPP Client can send IPP protocol requests (for
   example, 'Print-Job' requests) and receive IPP protocol responses
   over that HTTPS connection.

   See:  Section 4.2 (syntax) of this document.

   See:  Section 4.4.1 'printer-uri-supported' in IPP/1.1 Model and
   Semantics [RFC2911].

   See:  Section 5 'IPP URL Scheme' in IPP/1.1 Encoding and Transport
   [RFC2910].

   See:  Section 4 'IPP Standards' of IEEE-ISTO PWG IPP Version 2.0
   Second Edition [PWG5100.12].



4.2.  Syntax of 'ipps' URI Scheme

   The abstract protocol defined in IPP/1.1 Model and Semantics
   [RFC2911] places a limit of 1023 octets (NOT characters) on the
   length of a URI.

   See:  URI Generic Syntax [STD66].

   Per PWG IPP Everywhere [PWG5100.14], for compatibility with existing
   IPP implementations, IPP Printers SHOULD NOT generate 'ipp' [RFC3510]
   or 'ipps' URI (or allow administrators to configure) lengths above
   255 octets, because many older IPP Client implementations do not
   properly support these lengths.

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   Per PWG IPP Everywhere [PWG5100.14], in IPP protocol exchanges,
   'ipps' URI MUST be represented in absolute form.  Absolute URI always
   begin with a scheme name followed by a colon.  For definitive
   information on URI syntax and semantics, see "Uniform Resource
   Identifiers (URI) Generic Syntax and Semantics" [STD66].  This
   specification adopts the definitions of "host", "port", and "query"
   from [STD66].  This specification adopts the definition of
   "absolute-path" from [RFC7230].

   The 'ipps' URI scheme syntax in ABNF [STD68] is defined as follows:

   ipps-uri =
       "ipps:" "//" host [ ":" port ] [ absolute-path [ "?" query ]]

   Per IPP/1.1 Encoding and Transport [RFC2910], if the port is empty or
   not given, then port 631 MUST be used.

   See:  Section 4.3 (port) in this document.

   The semantics are that the identified resource (see [RFC7230]) is
   located at the IPP secure print service listening for HTTPS
   connections on that port of that host; and the Request-URI for the
   identified resource is 'absolute-path'.

   Note:  The higher-level "authority" production is not imported from
   [STD66], because it includes an optional "userinfo" component which
   cannot be used in 'ipps' URI.

   Note:  The "query" production does not have defined semantics in IPP
   and was never used in examples in IPP/1.1 Encoding and Transport
   [RFC2910] or the original IPP URL Scheme [RFC3510].  The "query" is
   retained here for consistency, but IPP Clients SHOULD avoid its use
   (because the semantics would be implementation-defined).

   Note:  Per PWG IPP Everywhere [PWG5100.14], literal IPv4 or IPv6
   addresses SHOULD NOT be used in 'ipps' URI, because:
   a) IP addresses are often changed after network device installation
      (for example, based on DHCP reassignment after a power cycle);
   b) IP addresses often don't map simply to security domains;
   c) IP addresses are difficult to validate with X.509 server
      certificates (because they do not map to common name or alternate
      name attributes); and
   d) IP link local addresses are not "portable" due to link identity

   Per IPP/1.1 Encoding and Transport [RFC2910], if the 'absolute-path'
   is not present in an IPP URI, it MUST be given as "/" when used as a
   Request-URI for a resource (see [RFC7230]).  An 'ipps' URI is
   transformed into an 'https' URI by replacing "ipps:" with "https:"
   and inserting port 631 (if an explicit 'port' is not present in the
   original 'ipps' URI).

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   See:  Section 4.3 (port) in this document.



4.3.  Associated Port for 'ipps' URI Scheme

   Per IPP/1.1 Encoding and Transport [RFC2910], all 'ipps' URI which do
   NOT explicitly specify a port MUST be resolved to IANA-assigned
   well-known port 631, already registered in [PORTREG] by [RFC2910].

   Note:  Per direction of the IESG, as described in [RFC2910], port 631
   is used for all IPP protocol connections (with or without TLS
   [RFC5246]).  Port 631 is therefore used for both 'ipp' [RFC3510] and
   'ipps' URI, which both refer to an IPP Printer or a network resource
   managed by an IPP Printer.  IPP Printer implementors can refer to the
   CUPS [CUPS] source code for an example of incoming connection
   handling for the dual use of port 631.

   See:  IANA Port Numbers Registry [PORTREG].

   See:  IPP/1.1 Encoding and Transport [RFC2910].



4.4.  Character Encoding of 'ipps' URI Scheme

   Per PWG IPP Everywhere [PWG5100.14], 'ipps' URI MUST:
   a) Use the UTF-8 [STD63] charset for all components; and
   b) Use [STD66] rules for percent encoding data octets outside the
      US-ASCII coded character set [ASCII].



4.5.  Examples of 'ipps' URI

   The following are examples of well-formed 'ipps' URI for IPP Printers
   (for example, to be used as protocol elements in 'printer-uri'
   operation attributes of 'Print-Job' request messages):

       ipps://example.com/
       ipps://example.com/ipp
       ipps://example.com/ipp/faxout
       ipps://example.com/ipp/print
       ipps://example.com/ipp/scan
       ipps://example.com/ipp/print/bob
       ipps://example.com/ipp/print/ira

   Note:  The use of an explicit 'ipp' path component followed by
   explicit 'print', 'faxout', 'scan', or other standard or vendor
   service component is best practice per [PWG5100.14], [PWG5100.15],

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   and [PWG5100.17].

   Each of the above URI is a well-formed URI for an IPP Printer and
   each would reference a logically different IPP Printer, even though
   some of those IPP Printers might share the same host system.  Note
   that 'print' might represent some grouping of IPP Printers (for
   example, a load-balancing spooler), while the 'bob' or 'ira' last
   path components might represent two different physical printer
   devices, Or 'bob' and 'ira' might represent separate human recipients
   on the same physical printer device (for example, a physical printer
   supporting two job queues).  In either case, both 'bob' and 'ira'
   would behave as different and independent IPP Printers.

   The following are examples of well-formed 'ipps' URI for IPP Printers
   with (optional) ports and paths:

       ipps://example.com/
       ipps://example.com/ipp/print
       ipps://example.com:631/ipp/print

   The first and second 'ipps' URI above will be resolved to port 631
   (IANA assigned well-known port for IPP).  The second and third 'ipps'
   URI above are equivalent (see section 4.6).

   See:  Section 4.2 (syntax) and section 4.3 (port) in this document.



4.6.  Comparisons of 'ipps' URI

   Per PWG IPP Everywhere [PWG5100.14], when comparing two 'ipps' URI to
   decide if they match or not, an IPP Client MUST use the same rules as
   those defined for 'http' and 'https' URI comparisons in [RFC7230],
   with the single following exception:

   - A port that is empty or not given MUST be treated as equivalent to
     the well-known port for that 'ipps' URI (port 631).

   See:  Section 4.3 (port) in this document.

   See:  Section 2.7.3 'http and https URI Normalization and Comparison'
   in [RFC7230].



5.  IANA Considerations

   [RFC Editor:  Replace 'xxxx' with assigned RFC number before
   publication]

   IANA is asked to register the new keyword value 'ipps' for the IPP

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   Printer "printer-uri-supported" attribute in the IANA IPP Registry
   [IPPREG], per section 6.2 Attribute Extensibility of IPP/1.1
   [RFC2911] as follows:



   IANA is asked to register the 'ipps' URI scheme using the following
   template, which conforms to [BCP35].

   URI scheme name:  ipps

   Status:  Permanent

   URI scheme syntax:  See section 4.2 of RFC xxxx.

   URI scheme semantics:  The 'ipps' URI scheme is used to designate
   secure IPP Printer objects (print spoolers, print gateways, print
   devices, etc.) on Internet hosts accessible using the IPP protocol
   enhanced to support guaranteed data integrity and negotiable data
   privacy using TLS [RFC5246] as specified in HTTP/1.1 [RFC7230].

   Encoding Considerations:  See section 4.4 of RFC xxxx.

   Applications/protocols that use this URI scheme name:

   The 'ipps' URI scheme is intended to be used by applications that
   need to access secure IPP Printers using the IPP protocol enhanced to
   support guaranteed data integrity and negotiable data privacy using
   TLS [RFC5246] as specified in HTTP/1.1 [RFC7230].  Such applications
   may include (but are not limited to) IPP-capable web browsers, IPP
   Clients that wish to print a file, and servers (for example, print
   spoolers) wishing to forward a Job for processing.

   Interoperability Considerations:  The widely deployed, open source
   IPP print service CUPS [CUPS] (on most UNIX, Linux, and Apple OS X
   systems) has supported 'ipps' URI for several years before the
   publication of this document.  PWG IPP Everywhere [PWG5100.14] (IPP
   secure, mobile printing extensions) requires the use of 'ipps' URI
   for mandatory data integrity and negotiable data confidentiality.

   Security Considerations:  See section 6 of RFC xxxx.

   Contact:

   Ira McDonald <blueroofmusic@gmail.com>

   Michael Sweet <msweet@apple.com>

   Author/Change controller:

   IESG

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   References:  RFC 2910, RFC 2911, RFC xxxx, and IEEE-ISTO PWG 5100.12.



6.  Security Considerations



6.1.  Problem Statement

   Powerful mobile devices (laptops, tablets, smartphones, etc.) are now
   commonly used to access enterprise and Cloud print services across
   the public Internet.  This is the primary use case for PWG IPP
   Everywhere [PWG5100.14], which has already been adopted by operating
   system and printer vendors and several other public standards bodies.
   End user and enterprise documents and user privacy-sensitive
   information are at greater risk than ever before.  This IPP over
   HTTPS transport binding and 'ipps' URI scheme specification was
   defined to enable high availability combined with secure operation in
   this dynamic environment (for example, wireless hotspots in hotels,
   airports, and restaurants).

   See:  Section 1 Introduction of [PWG5100.14].

   See:  Section 3.1 Rationale of [PWG5100.14].



6.1.1.  Targets of Attacks

   A network print spooler (logical printer) or print device (physical
   printer) is potentially subject to attacks, which may target:
   a) The network (to compromise the routing infrastructure, for
      example, by creating congestion);
   b) The Internet Printing Protocol (IPP) [RFC2911] (for example, to
      compromise the normal behavior of IPP);
   c) The print job metadata (for example, to extract privacy-sensitive
      information from the job submission request or via query of the
      job on the IPP Printer); or
   d) The print document content itself (for example, to steal the data
      or to corrupt the documents being transferred).



6.1.2.  Layers of Attacks

   Attacks against print services can be launched:
   a) Against the network infrastructure (for example, TCP [TCPROAD]
      congestion control);


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   b) Against the IPP data flow itself (for example, by sending forged
      packets or forcing TLS [RFC5246] version downgrade); or
   c) Against the IPP operation parameters (for example, by corrupting
      requested document processing attributes).



6.2.  Attacks and Defenses

   This 'ipps' URI Scheme specification adds the following additional
   security considerations to those described in [RFC7230], [RFC2910],
   [RFC2911], [RFC5246], [RFC7230], [PWG5100.12], and [STD66].

   See:  Section 8 'Security Considerations' in [RFC2910].

   See:  Section 8 'Security Considerations' in [RFC2911].

   See:  Appendix D 'Implementation Notes', Appendix E 'Backward
   Compatibility', and Appendix F 'Security Analysis' of [RFC5246].

   See:  Section 10 'Security Considerations' in [PWG5100.12].

   See:  Section 7 'Security Considerations' in [STD66].



6.2.1.  Faked 'ipps' URI

   An 'ipps' URI might be faked to point to a rogue IPP secure print
   service, thus collecting confidential job metadata or document
   contents from IPP Clients.

   Due to administrator reconfiguration or physical relocation of an IPP
   Printer, a former literal IPv4 or IPv6 address might no longer be
   valid - see section 4.2 for the recommendation against the use of
   literal IP addresses in 'ipps' URI.

   Server authentication mechanisms and security mechanisms specified in
   IPP/1.1 Encoding and Transport [RFC2910], HTTP/1.1 [RFC7230], and
   TLS/1.2 [RFC5246] can be used to address this threat.



6.2.2.  Unauthorized Access by IPP Client

   An 'ipps' URI might be used to access an IPP secure print service by
   an unauthorized IPP Client, for example, extracting privacy-sensitive
   information such as "job-originating-user-name" job metadata defined
   in IPP/1.1 Model and Semantics [RFC2911].

   Client authentication mechanisms and security mechanisms specified in

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   IPP/1.1 Encoding and Transport [RFC2910], HTTP/1.1 [RFC7230], and
   TLS/1.2 [RFC5246] can be used to address this threat.



6.2.3.  Compromise at Application Layer Gateway

   An 'ipps' URI might be used to access an IPP secure print service at
   a print protocol application layer gateway (for example, an IPP to
   LPD [RFC1179] gateway [RFC2569]), potentially causing silent
   compromise of IPP security mechanisms.

   There is no general defense against this threat by an IPP Client.
   System administrators SHOULD avoid such configurations.



6.2.4.  No Client Authentication for 'ipps' URI

   An 'ipps' URI does not define parameters to specify the required IPP
   Client authentication mechanism (for example, 'certificate' as
   defined in section 4.4.2 'uri-authentication-supported' of IPP Model
   [RFC2911]).

   An IPP Client SHOULD first use service discovery or directory
   protocols (e.g., the LDAP Printer Schema [RFC3712]) or directly send
   an IPP Get-Printer-Attributes operation to the target IPP Printer to
   read "printer-uri-supported", "uri-authentication-supported", and
   "uri-security-supported" attributes to discover the required IPP
   Client authentication and security mechanisms for each supported URI.



6.3.  TLS Version Requirements

   Per PWG IPP Everywhere [PWG5100.14] (and in accordance with security
   best practices and all existing deployments of the 'ipps' URI
   scheme), IPP Clients and IPP Printers that support this specification
   MUST use TLS/1.2 [RFC5246] or higher version, for all 'ipps' secure
   transport layer connections.

   Implementors will find useful advice in Recommendations for Secure
   Use of TLS and DTLS [TLSBCP].



7.  Acknowledgments

   This document has been submitted to the IETF by the Internet Printing
   Protocol Working Group of the IEEE-ISTO Printer Working Group, as
   part of their PWG IPP Everywhere [PWG5100.14] project for secure

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   mobile printing with vendor-neutral Client software.

   This document defines an alternate IPP transport binding to that
   defined in the original IPP URL Scheme [RFC3510], but this document
   does not update or obsolete [RFC3510].

   Thanks to Claudio Allochio, Jari Arrko, Spencer Dawkins, Adrian
   Farrel, Tom Hastings, Bjoern Hoerhmann, Smith Kennedy, Graham Klyne,
   Barry Leiba, S. Mooneswamy, Kathleen Moriarty, Sandra Murphy, Tom
   Petch, Pete Resnick, Benson Schliesser, Robert Sparks, Jerry
   Thrasher, Mykyta Yevstifeyev, Pete Zehler, and the members of the
   IEEE-ISTO PWG IPP WG.



8.  References



8.1.  Normative References

   [ASCII]    "American National Standards Institute, Coded Character
              Set -- 7-bit American Standard Code for Information
              Interchange", ANSI X3.4, 1986.

   [PWG5100.12] Bergman, R., Lewis, H., McDonald, I., and M. Sweet,
              "Internet Printing Protocol Version 2.0 Second Edition
              (IPP/2.0 SE)", PWG 5100.12, February 2011.
              <http://www.pwg.org/standards.html>

   [PWG5100.14] McDonald, I. and M. Sweet, "PWG IPP Everywhere", PWG
              5100.14, January 2013.
              <http://www.pwg.org/standards.html>

   [RFC2119]  Bradner, S., Key words for use in RFCs to Indicate
              Requirement Levels, BCP 14, RFC 2119, March 1997.

   [RFC2910]  Herriot, R., Ed., Butler, S., Moore, P., Turner, R., and
              J.  Wenn, "Internet Printing Protocol/1.1:  Encoding and
              Transport", RFC 2910, September 2000.

   [RFC2911]  Hastings, T., Ed., Herriot, R., deBry, R., Isaacson, S.,
              and P. Powell, "Internet Printing Protocol/1.1:  Model and
              Semantics", RFC 2911, September 2000.

   [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.

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   [RFC7231]  Fielding, R., and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1):  Semantics and Content", RFC 7231, June 2014.

   [STD63]    Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [STD66]    Berners-Lee, T., Fielding, R., and L. Masinter, Uniform
              Resource Identifiers (URI) Generic Syntax, STD 66, RFC
              3986, January 2005.

   [STD68]    Crocker, D., Ed., and P. Overell, "Augmented BNF for
              Syntax Specifications:  ABNF", STD 68, RFC 5234, January
              2008.



8.2.  Informative References

   [BCP35]    Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", BCP 35, RFC
              4395, February 2006.

   [CUPS]     Apple, "CUPS standards-based, open source printing system
              for OS X and other UNIX-like operating systems"
              <https://www.cups.org/>

   [IPPREG]   Internet Assigned Numbers Authority (IANA) Registries
              "Internet Printing Protocol"
              <http://www.iana.org/assignments/ipp-registrations/>

   [PORTREG]  Internet Assigned Numbers Authority (IANA) Registries
              "Port Numbers"
              <http://www.iana.org/assignments/port-numbers>

   [PWG5100.15] M. Sweet, "PWG IPP FaxOut Service", PWG 5100.15, June
              2014.
              <http://www.pwg.org/standards.html>

   [PWG5100.17] P. Zehler, "PWG IPP Scan Service", PWG 5100.17,
              September 2014.
              <http://www.pwg.org/standards.html>

   [RFC1179]  McLaughlin, L., "Line Printer Daemon Protocol", RFC 1179,
              August 1990.

   [RFC2566] deBry, R., Hastings, T., Herriot, R., Isaacson, S., and
              P. Powell, "Internet Printing Protocol/1.0:  Model and
              Semantics", RFC 2566, April 1999.



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   [RFC2569]  Herriot, R., Ed., Hastings, T., Jacobs, N., and J.
              Martin, "Mapping between LPD and IPP Protocols", RFC 2569,
              April 1999.

   [RFC2817]  Khare, R.  and S.  Lawrence, "Upgrading to TLS Within
              HTTP/1.1", RFC 2817, May 2000.

   [RFC3196]  Hastings, T., Manros, C., Zehler, P., Kugler, C., and H.
              Holst, "Internet Printing Protocol/1.1:  Implementor's
              Guide", RFC 3196, November 2001.

   [RFC3510]  Herriot, R.  and I.  McDonald, "Internet Printing
              Protocol/1.1:  IPP URL Scheme", RFC 3510, April 2003.

   [RFC3712]  Fleming, P.  and I.  McDonald, "Lightweight Directory
              Access Protocol (LDAP):  Schema for Printer Services", RFC
              3712, February 2004.

   [TCPROAD]  Duke, M., Braden, R., Eddy, W., Blanton, E., and
              A. Zimmerman, "A Roadmap for Transmission Control Protocol
              (TCP) Specification Documents", work in progress,
              <https://datatracker.ietf.org/doc/
              draft-ietf-tcpm-tcp-rfc4614bis/>

   [TLSBCP]   Scheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of TLS and DTLS", work in
              progress.
              <https://datatracker.ietf.org/doc/
              draft-ietf-uta-tls-bcp/>



9.  Appendix A - Abbreviations

   This document makes use of the following abbreviations (given with
   their expanded forms and references for further reading):

   ABNF   - Augmented Backus-Naur Form [STD68]

   ASCII  - American Standard Code for Information Interchange [ASCII]

   HTTP   - HyperText Transfer Protocol [RFC7230]

   HTTPS  - HTTP over TLS [RFC7230]

   IANA   - Internet Assigned Numbers Authority
            <http://www.iana.org>

   IEEE   - Institute of Electrical and Electronics Engineers
            <http://www.ieee.org>


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   IESG   - Internet Engineering Steering Group
            <http://www.ietf.org/iesg/>

   IPP    - Internet Printing Protocol [RFC2911] and [PWG5100.12]
            <http://www.pwg.org/ipp/>

   ISTO   - IEEE Industry Standards and Technology Organization
            <http://www.ieee-isto.org/>

   LPD    - Line Printer Daemon Protocol [RFC1179]

   PWG    - IEEE-ISTO Printer Working Group
            <http://www.pwg.org>

   RFC    - Request for Comments
            <http://www.rfc-editor.org/rfc.html>

   TCP    - Transmission Control Protocol [TCPROAD]

   TLS    - Transport Layer Security [RFC5246]

   URI    - Uniform Resource Identifier [STD66]

   URL    - Uniform Resource Locator [STD66]

   UTF-8  - Unicode Transformation Format - 8-bit [STD63]



10.  Authors' Addresses

   Ira McDonald
   High North Inc
   221 Ridge Ave
   Grand Marais, MI  49839

   Phone: +1 906-494-2434
   Email: blueroofmusic@gmail.com


   Michael Sweet
   Apple Inc
   1 Infinite Loop, M/S 111-HOMC
   Cupertino, CA  95014

   Email: msweet@apple.com


   Usage questions and comments on this 'ipps' URI Scheme can be sent
   directly to the editors at their above addresses and also to the PWG

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   IPP WG mailing list.  Instructions for subscribing to the PWG IPP WG
   mailing list can be found at:

   PWG IPP WG Web Page:      http://www.pwg.org/ipp/
   PWG IPP WG Mailing List:  ipp@pwg.org
   PWG IPP WG Subscription:  http://www.pwg.org/mailhelp.html

   Implementers of this specification are encouraged to join the PWG IPP
   WG Mailing List in order to participate in any discussions of
   clarification issues and comments.  Note that this IEEE-ISTO PWG
   mailing list rejects mail from non-subscribers (in order to reduce
   spam).








































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