Cloud Data Management Interface (CDMI) Media Types
RFC 6208

Internet Engineering Task Force (IETF)                    K. Sankar, Ed.
Request for Comments: 6208                                         Cisco
Category: Informational                                         A. Jones
ISSN: 2070-1721                                                     SNIA
                                                              April 2011

           Cloud Data Management Interface (CDMI) Media Types

Abstract

   This document describes several Internet media types defined for the
   Cloud Data Management Interface (CDMI) by the Storage Networking
   Industry Association (SNIA).  The media types are:

   o  application/cdmi-object

   o  application/cdmi-container

   o  application/cdmi-domain

   o  application/cdmi-capability

   o  application/cdmi-queue

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6208.

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Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
      1.1. Requirements Language ......................................3
   2. Cloud Data Management Domain and Its Relevance ..................3
   3. Processing Guidelines ...........................................4
      3.1. Media Type: application/cdmi-object ........................4
      3.2. Media Type: application/cdmi-container .....................4
      3.3. Media Type: application/cdmi-domain ........................5
      3.4. Media Type: application/cdmi-capability ....................5
      3.5. Media Type: application/cdmi-queue .........................5
   4. Transport Considerations ........................................6
   5. IANA Considerations .............................................6
      5.1. Media Type: application/cdmi-object ........................6
      5.2. Media Type: application/cdmi-container .....................7
      5.3. Media Type: application/cdmi-domain ........................8
      5.4. Media Type: application/cdmi-capability ....................9
      5.5. Media Type: application/cdmi-queue ........................10
   6. Security Considerations ........................................11
      6.1. Confidentiality and Integrity .............................11
      6.2. Access Control ............................................11
      6.3. Audit .....................................................12
      6.4. JSON Security Considerations ..............................12
      6.5. Executable/Active Content .................................12
   7. Acknowledgements ...............................................12
   8. References .....................................................12
      8.1. Normative References ......................................12
      8.2. Informative References ....................................13

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1.  Introduction

   The Cloud Data Management Interface (CDMI) [CDMI-1], developed by the
   Storage Networking Industry Association (SNIA), is the functional
   interface that applications will use to create, retrieve, update, and
   delete data elements from the cloud.  As part of this interface, the
   client will be able to discover the capabilities of the cloud storage
   offering and use this interface to manage containers and the data
   that is placed in them.  In addition, metadata can be set on
   containers and their contained data elements through this interface.

1.1.  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 RFC 2119 [RFC2119].

2.  Cloud Data Management Domain and Its Relevance

   A storage cloud is a storage service hosted either on premise or off
   premise, across a network.  An important part of the cloud model, in
   general, is the concept of a pool of resources that are drawn from,
   on demand, in small increments (smaller than what one would typically
   purchase by buying equipment).  By abstracting data storage behind a
   set of service interfaces and delivering it on demand, a wide range
   of actual offerings and implementations are possible.  The only type
   of storage that is excluded from this definition is that which is
   delivered based on fixed capacity increments rather than on demand.

   The CDMI defines a set of functional interfaces (data paths) and
   management interfaces (control paths) to create, retrieve, update,
   and delete data elements from a storage cloud.  Another important
   concept in this standard is that of metadata.  When managing large
   amounts of data with differing requirements, metadata is a convenient
   mechanism to express those requirements in such a way that underlying
   data services can differentiate their treatment of the data to meet
   those requirements.  CDMI also defines an extensible metadata system
   for storage clouds.

   As part of the CDMI interface, the client will be able to discover
   the capabilities of the cloud storage offering and to use this
   interface to manage containers and the data that is placed in them.
   In addition, system metadata can be added to containers and their
   contained data elements through this interface.

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   The hierarchy that CDMI defines is as follows:

   o  The basic element of storage is an object.

   o  Objects are stored in a container hierarchy.

   o  CDMI also defines an object, called a queue, which has special
      properties for in-order, first-in, first-out creation and fetching
      of queue objects, similar to a container of data objects.

   o  A cloud offering can also support domains, which allow
      administrative ownership to be associated with stored objects.
      Domains can also be hierarchical, allowing for corporate domains
      with multiple children domains for departments or individuals.
      The domain concept is also used to map Access Control Lists (ACLs)
      to principals as well as to aggregate usage data that is used to
      bill, meter, and monitor cloud usage.  (Note: The CDMI "domain"
      defined here is not a DNS domain name as specified in [RFC1076]
      and [RFC1024]).

   o  Finally, a capabilities resource and associated URI [RFC3986]
      allows a client to discover the capabilities of the offering and
      its implementation of CDMI.

3.  Processing Guidelines

   This section summarizes the processing of each media type.  This
   document provides only the essential information.  The CDMI
   specification [CDMI-1], which has more details and appropriate
   examples, is the final authority on the processing aspects.

3.1.  Media Type: application/cdmi-object

   A CDMI object is the basic storage element in a CDMI system and is
   analogous to a file within a filesystem.  The object is represented
   in the CDMI interface in JavaScript Object Notation (JSON) format
   [RFC4627].  (See the JSON web site at [JSON-1] for general
   information about JSON).  Each data object has a set of well-defined
   fields that includes a single value and optional metadata.  The
   implementations are free to store the data in any form they choose,
   but the application/cdmi-object SHOULD be represented in the CDMI
   interface as defined in Section 8 of the CDMI specification [CDMI-1].

3.2.  Media Type: application/cdmi-container

   A container object is the fundamental grouping of stored data within
   CDMI and is analogous to a directory within a filesystem.  Each
   container has zero or more child objects and a set of well-defined

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   fields that includes standardized and custom metadata.  A container
   can include other containers similar to sub-directories in a
   filesystem.  The implementations are free to represent the container
   in any form they choose, but the application/cdmi-container SHOULD be
   represented in the CDMI interface as defined in Section 9 of the CDMI
   specification [CDMI-1].

3.3.  Media Type: application/cdmi-domain

   Domain objects represent the concept of administrative ownership of
   stored data within a CDMI storage system.  A CDMI offering may
   include a hierarchy of domains that provide access to domain-related
   information within a CDMI context.  This domain hierarchy is a series
   of CDMI objects that correspond to parent and child domains, with
   each domain corresponding to logical groupings of objects that are to
   be managed together.  Section 10 of the CDMI specification [CDMI-1]
   details the information content, representation, and processing of
   domain objects.

3.4.  Media Type: application/cdmi-capability

   Capability objects form a special class of container objects that
   allows a CDMI client to discover what subset of the CDMI standard is
   implemented by a CDMI provider.  For each URI in a CDMI system, the
   set of interactions that the system is capable of performing against
   that URI is described by the presence of named "capabilities".  Each
   capability present for a given URI indicates what functionality the
   cloud storage system will allow against that URI.  Capabilities are
   always static.  Section 12 of the CDMI specification [CDMI-1] details
   the representation and processing of capability objects.

3.5.  Media Type: application/cdmi-queue

   Queues are a special class of container object and are used to
   provide first-in, first-out access when storing and retrieving data.
   A queue writer PUTs objects in the queue, and a queue reader GETs
   objects from the queue, acknowledging the receipt of the last object
   that it received.  Queuing provides a simple mechanism for one or
   more writers to send data to a single reader in a reliable way.  If
   queues are supported by the cloud storage system, cloud clients
   create the queue objects by using the same mechanism used to create
   data objects.  Section 11 of the CDMI specification [CDMI-1] details
   the operations and processing of queue objects.

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4.  Transport Considerations

   The CDMI operates over HTTP [RFC2616] and does not make sense outside
   the HTTP realm.  We do not expect the CDMI to operate over other
   protocols nor to use a transport protocol, such as TCP [RFC793],
   directly.

5.  IANA Considerations

   IANA has registered the following media types:

   o  application/cdmi-object

   o  application/cdmi-container

   o  application/cdmi-domain

   o  application/cdmi-capability

   o  application/cdmi-queue

5.1.  Media Type: application/cdmi-object

   Type name: application

   Subtype name: cdmi-object

   Required parameters: none

   Optional parameters: none

   Encoding considerations: Assumes that the representation is always
   UTF-8 as defined in [RFC3629] and 8bit as defined in [RFC4288]

   Security considerations: See Section 6 of RFC 6208

   Interoperability considerations: none

   Published specification: RFC 6208

   Applications that use this media type: Implementations of the Cloud
   Data Management Interface (CDMI) defined by the Storage Networking
   Industry Association (SNIA)

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   Additional information:

      Magic number(s): n/a

      File extension(s): .cdmio

      Macintosh file type code(s): TEXT

   Person and email address to contact for further information:
   Arnold Jones, arnold.jones@snia.org

   Intended usage: COMMON

   Restrictions on usage: none

   Author: SNIA Cloud Storage Initiative, cloudtwg@snia.org

   Change controller: SNIA Cloud Storage Initiative, cloudtwg@snia.org

5.2.  Media Type: application/cdmi-container

   Type name: application

   Subtype name: cdmi-container

   Required parameters: none

   Optional parameters: none

   Encoding considerations: Assumes that the representation is always
   UTF-8 as defined in [RFC3629] and 8bit as defined in [RFC4288]

   Security considerations: See Section 6 of RFC 6208

   Interoperability considerations: none

   Published specification: RFC 6208

   Applications that use this media type: Implementations of the Cloud
   Data Management Interface (CDMI) defined by the Storage Networking
   Industry Association (SNIA)

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   Additional information:

      Magic number(s): n/a

      File extension(s): .cdmic

      Macintosh file type code(s): TEXT

   Person and email address to contact for further information:
   Arnold Jones, arnold.jones@snia.org

   Intended usage: COMMON

   Restrictions on usage: none

   Author: SNIA Cloud Storage Initiative, cloudtwg@snia.org

   Change controller: SNIA Cloud Storage Initiative, cloudtwg@snia.org

5.3.  Media Type: application/cdmi-domain

   Type name: application

   Subtype name: cdmi-domain

   Required parameters: none

   Optional parameters: none

   Encoding considerations: Assumes that the representation is always
   UTF-8 as defined in [RFC3629] and 8bit as defined in [RFC4288]

   Security considerations: See Section 6 of RFC 6208

   Interoperability considerations: none

   Published specification: RFC 6208

   Applications that use this media type: Implementations of the Cloud
   Data Management Interface (CDMI) defined by the Storage Networking
   Industry Association (SNIA)

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   Additional information:

      Magic number(s): n/a

      File extension(s): .cdmid

      Macintosh file type code(s): TEXT

   Person and email address to contact for further information:
   Arnold Jones, arnold.jones@snia.org

   Intended usage: COMMON

   Restrictions on usage: none

   Author: SNIA Cloud Storage Initiative, cloudtwg@snia.org

   Change controller: SNIA Cloud Storage Initiative, cloudtwg@snia.org

5.4.  Media Type: application/cdmi-capability

   Type name: application

   Subtype name: cdmi-capability

   Required parameters: none

   Optional parameters: none

   Encoding considerations: Assumes that the representation is always
   UTF-8 as defined in [RFC3629] and 8bit as defined in [RFC4288]

   Security considerations: See Section 6 of RFC 6208

   Interoperability considerations: none

   Published specification: RFC 6208

   Applications that use this media type: Implementations of the Cloud
   Data Management Interface (CDMI) defined by the Storage Networking
   Industry Association (SNIA)

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   Additional information:

      Magic number(s): n/a

      File extension(s): .cdmia

      Macintosh file type code(s): TEXT

   Person and email address to contact for further information:
   Arnold Jones, arnold.jones@snia.org

   Intended usage: COMMON

   Restrictions on usage: none

   Author: SNIA Cloud Storage Initiative, cloudtwg@snia.org

   Change controller: SNIA Cloud Storage Initiative, cloudtwg@snia.org

5.5.  Media Type: application/cdmi-queue

   Type name: application

   Subtype name: cdmi-queue

   Required parameters: none

   Optional parameters: none

   Encoding considerations: Assumes that the representation is always
   UTF-8 as defined in [RFC3629] and 8bit as defined in [RFC4288]

   Security considerations: See Section 6 of RFC 6208

   Interoperability considerations: none

   Published specification: RFC 6208

   Applications that use this media type: Implementations of the Cloud
   Data Management Interface (CDMI) defined by the Storage Networking
   Industry Association (SNIA)

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   Additional information:

   Magic number(s): n/a

      File extension(s): .cdmiq

      Macintosh file type code(s): TEXT

   Person and email address to contact for further information:
   Arnold Jones, arnold.jones@snia.org

   Intended usage: COMMON

   Restrictions on usage: none

   Author: SNIA Cloud Storage Initiative, cloudtwg@snia.org

   Change controller: SNIA Cloud Storage Initiative, cloudtwg@snia.org

6.  Security Considerations

   This section was developed with RFC 3552 [RFC3552] as a guide.  CDMI
   is an application interface and the relevant security considerations
   include confidentiality, integrity, access control, and audit.
   Transport and endpoint security artifacts like Distributed Denial of
   Service (DDoS) are orthogonal, and domains like non-repudiation are
   left to the application that employs this interface.

6.1.  Confidentiality and Integrity

   The confidentiality and integrity of the CDMI exchanges are
   determined by the application that uses the interface.  CDMI does not
   contain any specific mechanisms and relies on transport mechanisms
   such as Transport Layer Security (TLS) (see [RFC2818]) for
   confidentiality and integrity of the messages across the network.

6.2.  Access Control

   The access control of the CDMI endpoint URLs are beyond this
   specification.  If required, applications should use appropriate URL
   authentication and authorization techniques, such as URI routers for
   different classes of users and restrict access based on URI origin.

   For fine-grained control of the CDMI objects, the CDMI specification
   [CDMI-1] contains the Access Control Lists (ACLs) and Access Control
   Entries (ACEs).  These are described fully in Section 16.1 of the
   CDMI specification [CDMI-1].

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6.3.  Audit

   The CDMI specification [CDMI-1] has defined a set of metadata fields,
   as explained in Section 16.3, to facilitate the incorporation of
   access and other audit markers.  The CDMI metadata system is
   extensible, and the implementations can add more metadata as required
   by the security posture of the domain.

6.4.  JSON Security Considerations

   JSON-related security considerations, described in RFC 4627
   [RFC4627], apply.

6.5.  Executable/Active Content

   The CDMI interface does not include any directives for active
   content.

7.  Acknowledgements

   The authors wish to acknowledge the guidance and wisdom of Mark
   Carlson and Peter Saint-Andre, comments from Patrick Faltstrom, and
   all the insightful discussions and ideas of the SNIA CDMI Cloud
   Technical Work Group.

8.  References

8.1.  Normative References

   [CDMI-1]   SNIA, "Cloud Data Management Interface Version 1.0", 2010,
              <http://www.snia.org/tech_activities/standards/
              curr_standards/cdmi>.

   [JSON-1]   JSON, "Introducing JSON", 2006, <http://www.json.org>.

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

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

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   [RFC4288]  Freed, N. and J. Klensin, "Media Type Specifications and
              Registration Procedures", BCP 13, RFC 4288, December 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

8.2.  Informative References

   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7, RFC
              793, September 1981.

   [RFC1024]  Partridge, C. and G. Trewitt, "HEMS variable definitions",
              RFC 1024, October 1987.

   [RFC1076]  Trewitt, G. and C. Partridge, "HEMS monitoring and control
              language", RFC 1076, November 1988.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July
              2003.

Authors' Addresses

   Krishna Sankar (editor)
   Cisco
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Phone: (408) 853 8475
   EMail: ksankar@cisco.com

   Arnold Jones
   SNIA
   4410 ArrowsWest Drive
   Colorado Springs, CO  80907
   USA

   Phone: (407) 574 7273
   EMail: arnold.jones@snia.org

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