DTN Research Group S. Symington Internet-Draft The MITRE Corporation Intended status: Experimental February 17, 2009 Expires: August 21, 2009 Delay-Tolerant Networking Previous Hop Insertion Block draft-irtf-dtnrg-bundle-previous-hop-block-05 Status of this Memo This Internet-Draft is submitted to IETF 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 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 21, 2009. 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 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. Symington Expires August 21, 2009 [Page 1] Internet-Draft DTN Previous Hop Insertion Block February 2009 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 information to its next-hop receiving node. This block is always removed from the bundle by the receiving node so that it's duration within the bundle lasts for exactly one hop. It provides a general insertion capability to enable any node that forwards a bundle to insert an arbitrary record (or records) of information into the bundle. While this block is defined to provide an arbitrary insertion capability, this specification also defines two specific, mandatory, information record formats for the information that may be carried in the Previous Hop Insertion block. Using these mandatory information record formats, an insertion block may be used to indicate the inserting/forwarding node's endpoint ID (EID), which may be required in some circumstances to support certain routing protocols (e.g., flood routing). This document defines the format and processing of this Previous Hop Insertion Block. Symington Expires August 21, 2009 [Page 2] Internet-Draft DTN Previous Hop Insertion Block February 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Previous Hop Insertion Block Format . . . . . . . . . . . . . 6 3. Previous Hop Insertion Block Processing . . . . . . . . . . . 8 3.1. Bundle Transmission . . . . . . . . . . . . . . . . . . . 8 3.2. Bundle Forwarding . . . . . . . . . . . . . . . . . . . . 8 3.3. Bundle Reception . . . . . . . . . . . . . . . . . . . . . 8 4. Mandatory Information Record Formats . . . . . . . . . . . . . 9 4.1. EID-only . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2. EID-with-Timestamp . . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 Symington Expires August 21, 2009 [Page 3] Internet-Draft DTN Previous Hop Insertion Block February 2009 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. A bundle consists of a primary bundle block, which is defined in the Bundle Protocol, followed by at least one other type of bundle block. The Bundle Protocol defines a single other type of bundle block, called a Bundle Payload block. This document defines an additional, optional, bundle block called a Previous Hop Insertion Block. This block is designed to be used by a forwarding node to insert information into a bundle before forwarding that bundle. The intent of this Previous Hop Insertion Block is to provide a general insertion mechanism such that an arbitrary record of information may be inserted into the bundle by a forwarding node for consumption by the next-hop receiving node. The lifetime of the Previous Hop Insertion Block is always exactly one hop in the DTN, so if a bundle containing a Previous Hop Insertion Block is received, the receiving node is assured that the information in this block was inserted by the previous node; likewise, the information in this block is not retained with the bundle when the bundle is forwarded. The information record(s) to be inserted into the block may have any content and format, providing the content and format have been defined and documented in order to enable the information to be understood. In this specification we define two specific information record formats for use in the insertion block that MUST be supported. Each of these formats includes a reference to the endpoint ID information of the inserting node in the bundle's dictionary. Insertion of a node's EID strings into the bundle dictionary (if not already there) and insertion of a reference to those strings in a bundle's Previous Hop Insertion Block enables the inserting/ forwarding node to provide its EID to its 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, used in conjunction with either an EID-only or an EID-with-timestamp information record format, whereby a node can Symington Expires August 21, 2009 [Page 4] Internet-Draft DTN Previous Hop Insertion Block February 2009 insert its EID (and possibly other information) into a bundle before forwarding it. Using the information record formats that are defined in this document, the information that is provided in the insertion blocks at each node may include not only the EID of the inserting/forwarding node, but also a time stamp. This information may be further expanded or altered through the future definition of additional information record formats to provide an arbitrary information record insertion capability. This document defines the format and processing of the Previous Hop Insertion Block. It also defines two mandatory information record formats. 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, -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 -Adding strings to a bundle's dictionary, and references to those strings to the bundle's Previous Hop Insertion Block. as defined in this document. Symington Expires August 21, 2009 [Page 5] Internet-Draft DTN Previous Hop Insertion Block February 2009 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 reference (optional) - composite field defined in [refs.DTNBP] containing a count of EID references (expressed as an SDNV) followed by one or more EID references (each of which is expressed as a pair of SDNVs). Whether or not this field must be present in the block is determined by the information record format (see Section 4) being used by the block. Presence of this field is indicated by the setting of the "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. -Block-type-specific data field as follows: -Information Record Format ID (SDNV) - Its value identifies the format of the information record that comes later in the block. Some mandatory information record formats are specified in Section 4. Additional information record formats MAY be defined in separate specifications. -Information Record (optional) - Contains the data being inserted by the forwarding node, formatted as identified by the value of the Information Record Format ID field. Whether or not this field must be present in the block is determined by the information record format (see Section 4) being used by the block. The Structure of a Previous Hop Insertion Block is as follows: Symington Expires August 21, 2009 [Page 6] Internet-Draft DTN Previous Hop Insertion Block February 2009 Previous Hop Insertion Block Format: +------+--------------+------------------------------+--------------+ |type |flags (SDNV) |EID ref count and list (comp) |length (SDNV) | +------+--------------+------------------------------+--------------+ | Information Record Format ID (SDNV)| Information Record (optional)| +-------------------------------------------------------------------+ Figure 1 Symington Expires August 21, 2009 [Page 7] Internet-Draft DTN Previous Hop Insertion Block February 2009 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 one or more Previous Hop Insertion Blocks (as defined in this specification). 3.2. Bundle Forwarding Before forwarding a bundle, the node SHALL delete all of the Previous Hop Insertion Blocks that were in the bundle when it was received. 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 one or more Previous Hop Insertion Blocks into the bundle before forwarding it, as dictated by local policy. The node MAY insert strings into the bundle's dictionary (if needed) that are referenced by the Previous Hop Insertion Block. 3.3. Bundle Reception If the bundle includes one or more Previous Hop Insertion Blocks, the information records in these blocks SHALL be made available for use at this node (e.g., in forwarding decisions). Symington Expires August 21, 2009 [Page 8] Internet-Draft DTN Previous Hop Insertion Block February 2009 4. Mandatory Information Record Formats This section defines the mandatory information record formats for this specification. Additional formats may be defined elsewhere. 4.1. EID-only The EID-only record format has information record-format ID 0x00000001. When the EID-only record format is being used, the "Block contains an EID-reference field" block processing control flag MUST be set, indicating that the Block EID reference count and EID references field is present in the block. The count of EID references in this field MUST have a value of 1, and this count MUST be followed by a single EID reference (expressed as a pair of SDNVs). This EID reference must be that of the node that is forwarding the bundle. The EID-only record format does not contain an information record field. 4.2. EID-with-Timestamp The EID-with-Timestamp record format has record-format ID 0x00000002. When the EID-with-Timestamp record format is being used, the "Block contains an EID-reference field" block processing control flag MUST be set, indicating that the Block EID reference count and EID references field is present in the block. The count of EID references in this field MUST have a value of 1, and this count MUST be followed by a single EID reference (expressed as a pair of SDNVs). This EID reference must be that of the node that is forwarding the bundle. The EID-with-Timestamp record format information record field consists of a single "Elapsed Time" field, which is expressed as an SDNV. The value in the elapsed time field indicates the time at which the bundle is being processed by the forwarding node, encoded as a number of seconds past the bundle's creation time. Symington Expires August 21, 2009 [Page 9] Internet-Draft DTN Previous Hop Insertion Block February 2009 5. Security Considerations The DTN Bundle Security Protocol [refs.DTNBPsec] and the DTN Security Overview [refs.DTNsecOver] define three 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 mandatory 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 mandatory 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 (correctly) omit the Previous Hop Insertion Block from their calculation. The fact that several different instantiations of this block may be present in 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 mandatory 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, a ciphersuite would need to be defined for this purpose. Symington Expires August 21, 2009 [Page 10] Internet-Draft DTN Previous Hop Insertion Block February 2009 6. 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. In addition, we may want IANA to establish a separate register of information record formats specific to the Previous Hop Insertion Block. Symington Expires August 21, 2009 [Page 11] Internet-Draft DTN Previous Hop Insertion Block February 2009 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.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-06.txt, work-in-progress, November 2008. 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., Weiss, H., and P. Lovell, "Delay-Tolerant Network Security Overview", draft-irtf-dtnrg-sec-overview-05.txt, work-in-progress, November 2008. Symington Expires August 21, 2009 [Page 12] Internet-Draft DTN Previous Hop Insertion Block February 2009 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/ Symington Expires August 21, 2009 [Page 13]