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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 6259

DTN Research Group                                          S. Symington
Internet-Draft                                     The MITRE Corporation
Intended status: Experimental                             March 24, 2009
Expires: September 25, 2009


         Delay-Tolerant Networking Previous Hop Insertion Block
             draft-irtf-dtnrg-bundle-previous-hop-block-06

Status of this Memo

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   This Internet-Draft will expire on September 25, 2009.

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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 Previous Hop Insertion
   Block is designed to be inserted by a forwarding node to provide its
   endpoint ID (EID) to the next-hop receiving node.  Knowledge of the
   EID of a previous-hop node may be required in some circumstances to
   support certain routing protocols (e.g., flood routing).  The
   Previous Hop Insertion block is always removed from the bundle by the
   receiving node so that it's duration within the bundle lasts for
   exactly one hop.  This document defines the format and processing of
   this Previous Hop Insertion Block.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Previous Hop Insertion Block Format  . . . . . . . . . . . . .  5
   3.  Previous Hop Insertion Block Processing  . . . . . . . . . . .  7
     3.1.  Bundle Transmission  . . . . . . . . . . . . . . . . . . .  7
     3.2.  Bundle Forwarding  . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Bundle Reception . . . . . . . . . . . . . . . . . . . . .  7
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11






















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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 an optional bundle block
   called a Previous Hop Insertion Block.  This Previous Hop Insertion
   Block is designed to be inserted by a forwarding node to provide its
   endpoint ID (EID) to the next-hop receiving node.  This previous-hop
   EID information may be required in some circumstances to support
   various routing protocols (e.g., flood routing).  Although there may
   be some situations in which a node that receives a bundle may be able
   to infer the EID of the node that forwarded the bundle to it, there
   are other situations in which the EID of the forwarding node will not
   be able to be inferred by the receiving node.  In these situations,
   if there is a requirement that the receiving node be able to
   determine the EID of the forwarding node, the forwarding node must
   provide this information in the bundle.  This specification defines a
   mechanism, i.e. the Previous Hop Insertion Block, whereby a node can
   insert its EID into a bundle before forwarding it.  If the EID of the
   inserting node is already in the dictionary field of the bundle's
   Primary Bundle Block, the Previous Hop Block MAY identify this EID
   using its Block EID reference count and EID references field.
   Otherwise, the Previous Hop Block MUST identify this EID by providing
   it in its block-type-specific data field.

   The lifetime of the Previous Hop Insertion Block is always exactly
   one hop in the DTN.  If a bundle containing a Previous Hop Insertion
   Block is received, the receiving node is assured that this block was
   inserted by the previous node, assuming all nodes are operating
   correctly; likewise, this block is not retained with the bundle when
   the bundle is forwarded.  If the bundle is forwarded with a Previous
   Hop Insertion Block, this block must identify the EID of the new
   forwarding node.

   This document defines the format and processing of the Previous Hop
   Insertion Block.  The capabilities described in this document are
   OPTIONAL for deployment with the Bundle Protocol.  Bundle Protocol
   implementations claiming to support Previous Hop Insertion Blocks
   MUST be capable of:

      -Generating a Previous Hop Insertion Block and inserting it into a
      bundle,





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      -Receiving bundles containing a Previous Hop Insertion Block and
      making the information contained in this Previous Hop Insertion
      Block available for use, e.g., in forwarding decisions.

      -Deleting a Previous Hop Insertion Block from a bundle

   as defined in this document.












































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2.  Previous Hop Insertion Block Format

   The Previous Hop Insertion 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 (one 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 Previous Hop Insertion
      Block is 0x05.

      -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).  The following block processing
      control flag MUST be set:

         -Discard block if it can't be processed.

      -Block EID reference count and EID references (optional) -
      composite field defined in [refs.DTNBP] containing a count of EID
      references (expressed as an SDNV) followed by an EID reference
      (expressed as a pair of SDNVs).  Whether or not this field may be
      present in the block is determined by whether or not the EID of
      the node inserting the block is already in the Dictionary Field of
      the Primary Bundle Block (e.g., whether this EID is the EID of the
      bundle's source, current custodian, or report-to endpoint, or of
      some other endpoint in the dictionary that is referenced by
      another block in the bundle).  If the EID of the inserting node is
      already in the dictionary, this field MAY be present in the block.
      If this field is present in the block, the value of the EID
      reference count MUST be one, meaning that the field contains
      exactly one EID reference, which MUST be a reference to the
      inserting node's EID.  Presence of this field is indicated by a
      set "block contains an EID reference field" flag in the block
      processing control flags.  If the EID of the inserting node is not
      already in the dictionary, this field MUST NOT be present in the
      block, which MUST be indicated by an unset "block contains an EID
      reference field" flag in the block processing control flags

      -Block data length (SDNV) - defined as in all bundle protocol
      blocks except the primary bundle block.  SDNV encoding is
      described in the Bundle Protocol.  If this value is zero, there
      are no block-type-specific data fields.  In this case, the
      inserting node's EID must have already been in the dictionary and
      it MUST be referenced in the Block EID reference count and EID
      references field as described above.





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      -Block-type-specific data fields (optional) as follows:

         -Inserting Node's EID Scheme Name - A null-terminated array of
         bytes that comprises the scheme name of the EID of the node
         inserting this Previous Hop Insertion Block.

         -Inserting Node's EID SSP - A null-terminated array of bytes
         that comprises the scheme-specific part (SSP) of the EID of the
         node inserting this Previous Hop Insertion Block.

      If the Block EID reference count and EID references field is not
      present in the block, the above two EID scheme name and SSP data
      fields MUST BE present.  Otherwise, these fields MAY be present.

   The Structure of a Previous Hop Insertion Block is as follows:

   Previous Hop Insertion Block Format:
   +----+------------+--------------------------------- -+-------------+
   |type|flags (SDNV)|EID ref count and list (comp) (opt)|length (SDNV)|
   +----+------------+-----------------------------------+-------------+
   | Inserting Node EID Scheme Name (opt)| Inserting Node EID SSP (opt)|
   +-------------------------------------------------------------------+

                                 Figure 1



























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3.  Previous Hop Insertion Block Processing

   The following are the processing steps that a bundle node must take
   relative to generation, reception, and processing of Previous Hop
   Insertion 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)
   include a Previous Hop Insertion Block (as defined in this
   specification).

3.2.  Bundle Forwarding

   Before forwarding a bundle, the node SHALL delete the Previous Hop
   Insertion Block that was in the bundle when it was received (if any).
   As described in the Bundle Protocol, the node MAY delete all strings
   (scheme names and scheme-specific parts--SSPs) in the bundle's
   dictionary to which no endpoint ID references in the bundle currently
   refer (if any).

   The node MAY insert a Previous Hop Insertion Block into the bundle
   before forwarding it, as dictated by local policy.  If there are
   already strings (scheme names and SSPs) in the bundle's dictionary
   that denote the inserting node's EID, the Previous Hop Insertion
   Block MAY reference these strings and, if it does, it need not
   include any block-type-specific data fields.  Otherwise, the
   inserting node MUST include its EID's scheme name and SSP as the
   block's block-type-specific data fields.  The inserting node MUST NOT
   insert strings into the bundle's dictionary in order that they may be
   referenced by only the Previous Hop Insertion Block.

3.3.  Bundle Reception

   If the bundle includes a Previous Hop Insertion Block, the EID
   identified in these blocks SHALL be made available for use at this
   node (e.g., in forwarding decisions).  If the EID is identified both
   by a reference in the block's Block EID reference count and EID
   references field and by a scheme name and SSP in the block-type-
   specific fields, the receiving node may use either mechanism to
   determine the EID being identified.









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4.  Security Considerations

   The DTN Bundle Security Protocol [refs.DTNBPsec] defines security-
   related blocks to provide hop-by-hop authentication, end-to-end
   authentication, and end-to-end confidentiality of bundles or parts of
   bundles, as well as a set of 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
   Previous Hop Insertion Block and would include that block in the
   calculation of their security result.  In particular, bundles
   including the optional Previous Hop Insertion 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 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 PSH-RSA-SHA256 ciphersuite and most end-to-end
   authentication ciphersuites) will (correctly) omit the Previous Hop
   Insertion Block from their calculation.  The fact that several
   different instantiations of this block may be added to and deleted
   from the bundle as the bundle transits the network will not interfere
   with end-to-end security protection when using ciphersuites that use
   mutable canonicalisation.  Lastly, the Previous Hop Insertion Block
   will not be encrypted by the CH-RSA-AES-PAYLOAD-PSH end-to-end
   confidentiality ciphersuite, which only allows for payload and PSH
   encryption.  If encryption of this block is desired, the Extension
   Security Block (ESB) could be used for this purpose.

   Nodes receiving bundles with Previous Hop Insertion Blocks should be
   aware that forwarding nodes that insert Previous Hop Insertion Blocks
   might lie about their EIDs.  Lying in this way could provide a
   mechanism for subverting routing strategies that base routing
   decisions on EID information in the Previous Hop Insertion Block.

   Note that if some Bundle Protocol implementation does not support the
   Previous Hop Insertion Block but does not properly implement the
   "Discard block if it can't be processed" flag, then a Previous Hop
   Insertion Block may unexpectedly persist for longer than a single
   hop.









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5.  IANA Considerations

   If the bundle protocol becomes a standards track protocol, then we
   may want to consider having IANA establish a register of block types,
   of which the Previous Hop Insertion Block would be one.














































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6.  References

6.1.  Normative References

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

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

   [refs.DTNBPsec]
              Symington, S., Farrell, S., Weiss, H., and P. Lovell,
              "Bundle Security Protocol Specification",
              draft-irtf-dtnrg-bundle-security-09.txt, work-in-progress,
              March 2008.

6.2.  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.



























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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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