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DTN Research Group                                          S. Symington
Internet-Draft                                     The MITRE Corporation
Intended status: Experimental                            October 8, 2009
Expires: April 11, 2010


           Delay-Tolerant Networking Metadata Extension Block
               draft-irtf-dtnrg-bundle-metadata-block-04

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on April 11, 2010.

Copyright Notice

   Copyright (c) 2009 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
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Abstract

   This document defines an extension block that may be used with the
   Bundle Protocol [refs.DTNBP] within the context of a Delay-Tolerant
   Network architecture [refs.DTNarch].  This Metadata Extension Block
   is designed to be used to carry application-level information that
   DTN nodes can use to make DTN-level processing decisions regarding
   bundles, such as deciding whether to store a bundle or determining to
   which nodes to forward a bundle.  The actual metadata that is carried
   in a metadata block must be formatted according to the metadata type
   that is identified in the block's metadata type field.  One specific
   metadata type, for encoding metadata as URIs, is defined in this
   document.  Other metadata types may be defined in separate documents.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Metadata Block Format  . . . . . . . . . . . . . . . . . . . .  5
   3.  Metadata Block Processing  . . . . . . . . . . . . . . . . . .  7
     3.1.  Bundle Transmission  . . . . . . . . . . . . . . . . . . .  7
     3.2.  Bundle Forwarding  . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Bundle Reception . . . . . . . . . . . . . . . . . . . . .  7
   4.  Predefined Metadata Types  . . . . . . . . . . . . . . . . . .  8
     4.1.  URI Metadata Type  . . . . . . . . . . . . . . . . . . . .  8
     4.2.  Private Metadata Types . . . . . . . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12



















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1.  Introduction

   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
   [refs.RFC2119].

   The DTN bundle protocol [refs.DTNBP] defines the bundle as its
   protocol data unit.  This document defines a bundle block called a
   Metadata Block.  This block is designed to be used to carry metadata
   related to application-level information, but that is intended to be
   used by DTN nodes as they process the bundle at the DTN network-
   level.

   The metadata block has been deliberately defined to be flexible
   enough that it would be capable of supporting a variety of metadata
   types and formats.  However, as mentioned, it is the intention that
   the actual metadata that is carried in this block be application-
   level information.  For example, the metadata might be information
   that is associated with the payload of a bundle.  So, although the
   metadata block may be general enough that it could be used to carry
   DTN network-level information, such as the endpoint ID of the
   previous hop node, hop counts, QOS information, priority information,
   timestamps, record route-type information, the endpoint ID of a node
   that the bundle should be forwarded through, the endpoint ID of a
   node that should take custody of the bundle, network transmission
   cost information, or network debugging information, it is not our
   intent that the metadata block be used to carry such network-level
   information that is unrelated to application-level information.
   Additional extension blocks could be (and have been) defined for
   carrying such network-level information.

   While the bundle payload is processed opaquely by DTN nodes, metadata
   is intended to serve as a mechanism for providing DTN nodes with
   access to application-level information that they can use to process
   the bundle.  Examples of such application-level information include
   keywords found in the payload, payload provenance information, GPS
   coordinates (if the payload is a map, for instance), message IDs, and
   artist, album and track name (if the payload is a song).  Even though
   the metadata is application-level information, its purpose is to be
   used by DTN nodes to make network-level decisions regarding how to
   process bundles, such as whether or not a bundle should be stored or
   to which nodes a bundle should be forwarded.  If metadata is about
   application-level information that is carried as bundle payload, for
   example, it might serve as a content-based index of bundles that are
   stored in a DTN cache.  So, in response to a request for bundles
   related to a certain subject or related to specific GPS coordinates,
   for example, the metadata of stored bundles could be searched and all



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   bundles with metadata matching the search criteria could be retrieved
   and returned to the requestor.

   This document defines the general format of and the processing
   required to support the Metadata Block.  The actual metadata to be
   inserted into a metadata block MUST be formatted according to the
   metadata type that is identified in the block's metadata type field.
   One specific metadata type, for encoding metadata as Uniform Resource
   Identifiers (URIs) [refs.URI], is defined in this document.  Other
   metadata types may be defined in separate documents, along with the
   steps required to process records of that type, if necessary.  If
   such other metadata types are defined, they should be registered to
   ensure global uniqueness (see the IANA Considerations section).

   A bundle may contain multiple metadata extension blocks.  In some
   cases, multiple metadata blocks may be carried in the bundle,
   possibly with each being encrypted separately from each other and
   from the payload.  Such separate encryption of metadata from payload
   would enable bundle nodes to perform content-based searching and
   routing on bundle metadata that they are able to decrypt, even if
   they are not able to decrypt the bundle payload.

   The capabilities described in this document are OPTIONAL for
   deployment with the Bundle Protocol.  Bundle Protocol implementations
   claiming to support the Metadata Block MUST be capable of:

      -Generating a Metadata Block and inserting it into a bundle,

      -Receiving bundles containing a Metadata Block and making the
      information contained in this Metadata Block's metadata field
      available for use, e.g., in bundle storage or forwarding
      decisions,

      -Deleting a metadata block from a received bundle before
      forwarding the bundle

   as defined in this document.

   Bundle Protocol implementations claiming to support a specific
   metadata type must both support the metadata block as defined above
   and be capable of parsing and processing the metadata itself
   according to the definition of the metadata type in which the
   metadata is expressed.  This metadata type may be the URI Metadata
   Type (see the URI Metadata Type section), or it may be another
   metadata type defined in a separate document.






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2.  Metadata Block Format

   The Metadata Block uses the Canonical Bundle Block Format as defined
   in the bundle protocol [refs.DTNBP].  That is, it is comprised of the
   following elements:

      -Block-type code (1 byte) - defined as in all bundle protocol
      blocks except the primary bundle block (as described in the Bundle
      Protocol).  The block type code for the Metadata Block is 0x08.

      -Block processing control flags (SDNV) - defined as in all bundle
      protocol blocks except the primary bundle block.  SDNV encoding is
      described in the Bundle Protocol.  There are no constraints on the
      use of the Block Processing Control Flags.  If a bundle node
      receives a bundle with a metadata block and it is capable of
      supporting the metadata block but it is not able to parse and
      process the metadata itself, either because it does not support
      the metadata type being used or because the metadata is not well-
      formed according to the metadata type definition, the bundle node
      must process the bundle as if it cannot process the metadata
      block.  That is, it must operate according to the settings of the
      Block Processing Control Flags, including the "Delete bundle if
      block can't be processed" flag and the "Discard block if it can't
      be processed" flag.

      -EID Reference Count and List (optional) - composite field defined
      in the bundle protocol that is present if and only if the metadata
      block references EID elements in the primary block's dictionary.
      Presence of this field is indicated by the setting of the "Block
      contains an EID-reference field" bit of the block processing
      control flags.  If EIDs are referenced in the metadata block, then
      their interpretation is defined by the particular metadata type
      that is being used in this metadata block, as indicated in the
      metadata type field.

      -Block data length (SDNV) - defined as in all bundle protocol
      blocks except the primary bundle block.  SDNV encoding is
      described in the bundle protocol.

      -Block-type-specific data fields as follows:

         - Metadata Type field (SDNV) - indicates which metadata type is
         to be used to interpret both the metadata in the metadata field
         and the EID references in the optional EID Reference Count and
         List field (if present).  One metadata type is defined in this
         document.  Other metadata types may be defined in separate
         documents.




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         - Metadata field - contains the metadata itself, formatted
         according to the metadata type that has been specified for this
         block.

   The Structure of a Metadata Block is as follows:

   Metadata Block Format:
   +-----+------+--------------------+------+----------+----------|
   |Type |Flags |EID Reference count |Len   | Metadata | Metadata |
   |     |(SDNV)|  and list (opt)    |(SDNV)|   Type   |          |
   +-----+------+--------------------+------+----------+----------+

                                 Figure 1






































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3.  Metadata Block Processing

   The following are the processing steps that a bundle node may take
   relative to generation, reception, and processing of Metadata Blocks.

3.1.  Bundle Transmission

   When an outbound bundle is created per the parameters of the bundle
   transmission request, this bundle MAY (as influenced by local policy
   and the metadata type being used) include one or more metadata blocks
   (as defined in this specification).

3.2.  Bundle Forwarding

   A node MAY insert one or more metadata Blocks into a bundle before
   forwarding it; and a node MAY delete one or more metadata blocks from
   a bundle before forwarding it, as dictated by local policy and the
   metadata type being used.

3.3.  Bundle Reception

   If the bundle includes one or more metadata blocks, the metadata
   information records in these blocks SHALL be made available for use
   at this node (e.g., in bundle storage or forwarding decisions).



























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4.  Predefined Metadata Types

   As mentioned in the previous section, any number of different
   metadata types may be defined to indicate the format of both the
   metadata field and the EID references in the optional EID Reference
   Count and List field (if present) and, if necessary, how metadata of
   this type should be processed.  One metadata type is defined in this
   document, URI Metadata Type (0x01).  In addition, a range of metadata
   type values is reserved for private use.

4.1.  URI Metadata Type

   It is believed that use of URIs will in many cases be adequate for
   encoding metadata, although it is recognized that use of URIs may not
   be the most efficient method for such encoding.  Because of the
   expected utility of using URI encoding for metadata, the metadata
   type value of 0x01 is defined to indicate a metadata type of URI.
   Metadata type values other than 0x01 will be used to indicate
   alternative metadata types.

   The Metadata field for metadata of metadata type URI (0x01) consists
   of an array of bytes formed by concatenating one or more null-
   terminated URIs.  Unless determined by local policy, the specific
   processing steps that must be performed on bundles with metadata
   blocks containing metadata of type URI are expected to be included as
   part of the URI encoding of the metadata.  Metadata blocks containing
   metadata of type URI MUST NOT include an EID references field.  The
   absence of this field MUST be indicated by a value of 0 for the
   "block contains an EID reference field" flag in the block processing
   control flags.  Support for the URI metadata type is OPTIONAL.

4.2.  Private Metadata Types

   Metadata type values 192 through 249 are not defined in this
   specification and are available for private and/or experimental use.
   Such private metadata types and are not required to be registered.
   All other values of the metadata type are reserved for future use
   and, when defined, should be registered to ensure global uniqueness
   (see the IANA Considerations section).  Local policy will define how
   private metadata types are handled.  Support for private metadata
   types is OPTIONAL.










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5.  Security Considerations

   The DTN Bundle Security Protocol [refs.DTNBPsec] defines security-
   related blocks to provide hop-by-hop authentication, end-to-end
   authentication, end-to-end confidentiality of bundles or parts of
   bundles, and an extension security block to provide confidentiality
   and integrity for extension blocks, as well as a set of standard
   ciphersuites that may be used to calculate security results carried
   in these security blocks.  All ciphersuites that use the strict
   canonicalisation algorithm [refs.DTNBPsec] to calculate and verify
   security results (e.g., many hop-by-hop authentication ciphersuites)
   apply to all blocks in the bundle, and so would apply to bundles that
   include an optional Metadata Block and would include that block in
   the calculation of their security result.  In particular, bundles
   including the optional Metadata Block would be protected in their
   entirety for the duration of a single hop, from a forwarding node to
   an adjacent receiving node (but not from source to destination),
   using the standard BAH-HMAC ciphersuite defined in the Bundle
   Security Protocol.  Ciphersuites that use the mutable
   canonicalisation algorithm to calculate and verify security results
   (e.g., the mandatory PSH-RSA-SHA256 ciphersuite and most end-to-end
   authentication ciphersuites) will omit the Metadata Block from their
   calculation.  The fact that metadata in the metadata block may be
   modified or that metadata blocks themselves may be added to or
   deleted from a bundle as it transits the network will not interfere
   with end-to-end security protection when using ciphersuites that use
   mutable canonicalisation.  Lastly, the Metadata Block will not be
   encrypted by the mandatory CH-RSA-AES-PAYLOAD-PSH end-to-end
   confidentiality ciphersuite, which only allows for payload and PSH
   encryption.

   In order to provide the metadata block with end-to-end
   confidentiality and authentication independent of any confidentiality
   or authentication that is provided for the payload or other parts of
   the bundle, the extension security block may be used to encrypt and
   authenticate the metadata block.

   Given that metadata can be modified by forwarding nodes, it may be
   desirable to eventually support the ability to audit changes to the
   metadata at the individual record level.  No such capability has been
   provided in this specification as currently written.










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6.  IANA Considerations

   We may want to consider having IANA establish a register of Bundle
   Protocol header types, with the Metadata Extension Block header
   identified as type 0x08.  In association with the Metadata Extension
   block, we may want IANA to establish a separate register of metadata
   types.












































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7.  References

7.1.  Normative References

   [refs.RFC2119]
              Bradner, S. and J. Reynolds, "Key words for use in RFCs to
              Indicate Requirement Levels", RFC 2119, October 1997.

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

   [refs.DTNBP]
              Scott, K. and S. Burleigh, "Bundle Protocol
              Specification", RFC 5050, November 2007.

   [refs.DTNBPsec]
              Symington, S., Farrell, S., and H. Weiss, "Bundle Security
              Protocol Specification",
              draft-irtf-dtnrg-bundle-security-08.txt, work-in-progress,
              March 2009.

7.2.  Informative References

   [refs.DTNarch]
              Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
              R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
              Network Architecture", RFC 4838, April 2007.

   [refs.DTNsecOver]
              Farrell, S., Symington, S., and H. Weiss, "Delay-Tolerant
              Network Security Overview",
              draft-irtf-dtnrg-sec-overview-06.txt, work-in-progress,
              March 2009.
















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Author's Address

   Susan Flynn Symington
   The MITRE Corporation
   7515 Colshire Drive
   McLean, VA  22102
   US

   Phone: +1 (703) 983-7209
   Email: susan@mitre.org
   URI:   http://mitre.org/








































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