Delay-Tolerant Networking Working Group S. Burleigh Internet Draft JPL, Calif. Inst. Of Technology Intended status: Standards Track June 22, 2017 Expires: December 2017 Bundle-in-Bundle Encapsulation draft-burleigh-dtn-bibect-00.txt 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 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." 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Burleigh Expires December 2017 [Page 1] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 Abstract This document describes Bundle-in-Bundle Encapsulation (BIBE), a Delay-Tolerant Networking (DTN) Bundle Protocol (BP) "convergence layer" protocol that tunnels BP "bundles" through encapsulating bundles. The services provided by the BIBE convergence-layer protocol adapter encapsulate an outbound BP "bundle" in a BIBE convergence-layer protocol data unit for transmission as the payload of a bundle. Security measures applied to the encapsulating bundle may augment those applied to the encapsulated bundle. The protocol includes a mechanism for recovery from loss of an encapsulating bundle, called "custody transfer". This mechanism is adapted from the custody transfer procedures described in the experimental Bundle Protocol specification developed by the Delay-Tolerant Networking Research group of the Internet Research Task Force and documented in RFC 5050. Table of Contents 1. Introduction...................................................2 2. Conventions used in this document..............................4 3. BIBE Design Elements...........................................4 3.1. BIBE Endpoints............................................4 3.2. BIBE Protocol Data Units..................................4 3.3. Custody Signals...........................................5 3.4. Custody Transfer Status Reports...........................7 4. BIBE Procedures................................................7 4.1. BPDU Transmission.........................................7 4.2. BPDU Reception............................................8 4.3. Retransmission Timer Expiration...........................9 4.4. Custody Signal Reception.................................10 5. Security Considerations.......................................10 6. IANA Considerations...........................................10 7. Acknowledgments.....................Error! Bookmark not defined. 8. References....................................................10 8.1. Normative References.....................................10 8.2. Informative References...................................11 9. Acknowledgments...............................................11 Appendix A. For More Information.................................12 Appendix B. CDDL expression......................................13 1. Introduction This document describes Bundle-in-Bundle Encapsulation (BIBE), a Delay-Tolerant Networking (DTN) Bundle Protocol (BP) [RFC5050] Burleigh Expires December 2017 [Page 2] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 "convergence layer" protocol that tunnels BP "bundles" through encapsulating bundles. Conformance to the bundle-in-bundle encapsulation (BIBE) specification is OPTIONAL for BP nodes. Each BP node that conforms to the BIBE specification provides a BIBE convergence-layer adapter (CLA) that is implemented within the administrative element of the BP node's application agent. Like any convergence-layer adapter, the BIBE CLA provides: . A transmission service that sends an outbound bundle (from the bundle protocol agent) to a peer CLA. In the case of BIBE, the sending CLA and receiving peer CLA are both BP nodes. . A reception service that delivers to the bundle protocol agent an inbound bundle that was sent by a peer CLA (itself a BP node) via the BIBE convergence layer protocol. The BIBE CLA performs these services by: . Encapsulating outbound bundles in BIBE protocol data units, which take the form of Bundle Protocol administrative records as described later. . Requesting that the bundle protocol agent transmit bundles whose payloads are BIBE protocol data units. . Taking delivery of BIBE protocol data units that are the payloads of bundles received by the bundle protocol agent. . Delivering to the bundle protocol agent the bundles that are encapsulated in delivered BIBE protocol data units. Bundle-in-bundle encapsulation may have broad utility, but the principal motivating use case is the deployment of "cross domain solutions" in secure communications. Under some circumstances a bundle may arrive at a node that is on the frontier of a region of network topology in which augmented security is required, from which the bundle must egress at some other designated node. In that case, the bundle may be encapsulated within a bundle to which the requisite additional BP Security (BPSEC) [bpsec] extension block(s) can be attached, whose source is the point of entry into the insecure region (the "security source") and whose destination is the point of egress from the insecure region (the "security destination"). Note that: . If the payload of the encapsulating bundle is protected by a Bundle Confidentiality Block (BCB), then the source and Burleigh Expires December 2017 [Page 3] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 destination of the encapsulated bundle are encrypted, providing defense against traffic analysis that BPSEC alone cannot offer. . Bundles whose payloads are BIBE protocol data units may themselves be forwarded via a BIBE convergence-layer adapter, enabling nested bundle encapsulation to arbitrary depth as required by security policy. . Moreover, in the event that no single point of egress from an insecure region of network topology can be determined at the moment a bundle is to be encapsulated, multiple copies of the bundle may be encapsulated individually and forwarded to all candidate points of egress. The protocol includes a mechanism for recovery from loss of an encapsulating bundle, called "custody transfer". This mechanism is adapted from the custody transfer procedures described in the experimental Bundle Protocol specification developed by the Delay- Tolerant Networking Research group of the Internet Research Task Force and documented in RFC 5050. Custody transfer is a convention by which the loss or corruption of BIBE encapsulating bundles can be mitigated by the exchange of other bundles, which are termed "custody signals". 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]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. 3. BIBE Design Elements 3.1. BIBE Endpoints BIBE convergence-layer protocol endpoints, also known as BIBE convergence-layer adapters (BCLAs), are the Administrative Elements of Bundle Protocol nodes that conform to the BIBE protocol specification. The node of which a given BCLA is one component is termed the BCLA's "local node". 3.2. BIBE Protocol Data Units A BIBE protocol data unit (BPDU) is defined as a Bundle Protocol administrative record whose record type code is 7 (i.e., bit pattern 0111) constructed as follows. Burleigh Expires December 2017 [Page 4] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 Each BPDU SHALL be represented as a CBOR array. The number of elements in the array SHALL be 2. The first item of the BPDU array SHALL be a flag indicating whether or not Custody Transfer is requested for this BPDU, represented as a CBOR Boolean value. The second item of the content array SHALL be a single BP bundle, termed the "encapsulated bundle", represented as a CBOR byte string. 3.3. Custody Signals A "custody signal" is defined as a Bundle Protocol administrative record whose record type code is 2 (i.e., bit pattern 0010) constructed as follows. Each custody signal SHALL be represented as a CBOR array. The number of elements in the array SHALL be 6 (if the bundle to which the custody signal refers is a fragment) or 4 (otherwise). The first item of the custody signal array SHALL be a signal type code represented as a CBOR unsigned integer. Valid custody signal types are defined as follows: +---------+--------------------------------------------+ | Value | Meaning | +=========+============================================+ | 0 | Custody acceptance. The reporting node | | | accepted custody of the bundle. | +---------+--------------------------------------------+ | 1 | Custody refusal. The reporting node | | | refused custody of the bundle. | +---------+--------------------------------------------+ | (other) | Reserved for future use. | +---------+--------------------------------------------+ Figure 1: Custody Signal Type Codes Burleigh Expires December 2017 [Page 5] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 The second item of the custody signal array SHALL be a custody signal reason code, represented as a CBOR unsigned integer. Valid custody signal reason codes are defined as follows: +---------+--------------------------------------------+ | Value | Meaning | +=========+============================================+ | 0 | No additional information. | +---------+--------------------------------------------+ | 1 | Reserved for future use. | +---------+--------------------------------------------+ | 2 | Reserved for future use. | +---------+--------------------------------------------+ | 3 | Redundant (reception by a node that | | | already has a copy of this bundle). | +---------+--------------------------------------------+ | 4 | Depleted storage. | +---------+--------------------------------------------+ | 5 | Destination endpoint ID unintelligible. | +---------+--------------------------------------------+ | 6 | No known route destination from here. | +---------+--------------------------------------------+ | 7 | No timely contact with next node on route. | +---------+--------------------------------------------+ | 8 | Block unintelligible. | +---------+--------------------------------------------+ Burleigh Expires December 2017 [Page 6] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 | (other) | Reserved for future use. | +---------+--------------------------------------------+ Figure 2: Custody Signal Reason Codes The third item of the custody signal array SHALL be the node ID identifying the source of the encapsulated bundle to which the custody signal pertains, termed the "subject bundle", represented as described in the Bundle Protocol specification, a work in progress. The fourth item of the custody signal array SHALL be the creation timestamp of the subject bundle, represented as described in BPpbis]. The fifth item of the custody signal array SHALL be present if and only if the subject bundle is a fragment. If present, it SHALL be the subject bundle's fragment offset represented as a CBOR unsigned integer. The sixth item of the custody signal array SHALL be present if and only if the subject bundle is a fragment. If present, it SHALL be the length of the subject bundle's payload represented as a CBOR unsigned integer. 3.4. Custody Transfer Status Reports A "custody transfer status report" is a bundle status report with the "reporting node attempted custody transfer" flag set to 1. 4. BIBE Procedures 4.1. BPDU Transmission When a BCLA is requested by the bundle protocol agent to send a bundle to the peer BCLA(s) included in the BP endpoint identified by a specified BP endpoint ID: . The BCLA SHALL generate, as defined in Section 6.2 of the Bundle Protocol specification (a work in progress), a BPDU for which the second item of the content array is the bundle that is to be transmitted. Note that any transmission request presented to a BCLA MAY request that the transmission be subject to Custody Transfer; if and only if Custody Transfer is requested, the first item of the BPDU's content array SHALL be the Boolean value True. The destination of the bundle whose payload is the BPDU (termed the "encapsulating bundle") SHALL Burleigh Expires December 2017 [Page 7] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 be the specified BP endpoint. Selection of the values of the parameters governing the forwarding of the encapsulating bundle, other than the destination endpoint ID, is an implementation matter. The parameter values governing the forwarding of the BPDU's encapsulated bundle MAY be consulted for this purpose. . If and only if Custody Transfer is requested: o The bundle protocol agent MUST add the retention constraint "Custody accepted" to the encapsulated bundle. o The BCLA MAY establish a retransmission countdown timer for the encapsulated bundle. Note that the custody transfer retransmission timer mechanism provides a means of recovering from loss of an encapsulating bundle as indicated by non-arrival of a responding custody signal. Computation of the timeout interval for an encapsulating bundle's retransmission timer (i.e., determination of the moment at which a responding custody signal is expected) is an implementation matter and may be dynamically responsive to changes in connectivity. 4.2. BPDU Reception When a BCLA receives a BPDU from the bundle protocol agent (that is, upon delivery of the payload of an encapsulating bundle): . If and only if Custody Transfer was requested for this BPDU: o If the encapsulated bundle has the same source node ID, creation timestamp, and (if that bundle is a fragment) fragment offset and payload length as another bundle that is currently retained at the BCLA's local node, then custody transfer redundancy MUST be handled as follows: . The BCLA SHALL generate a custody signal of type 1 (custody refusal) referencing the encapsulated bundle, destined for the node that was the source of the encapsulating bundle. The reason code for the custody signal SHALL be "Redundant reception". . If the "request reporting of custody transfer attempted" flag in the encapsulating bundle's status report request field is set to 1, and status reporting is enabled, a custody transfer status report with the same reason code SHOULD be generated, destined for the report-to endpoint of the encapsulating bundle. o Otherwise, if the BCLA determines that its local node can neither deliver nor forward the encapsulated bundle for any of the reasons listed in Figure 2, then custody Burleigh Expires December 2017 [Page 8] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 transfer has failed. Custody transfer failure SHALL be handled as follows: . The BCLA SHALL generate a custody signal of type 1 (custody refusal) referencing the encapsulated bundle, destined for the node that was the source of the encapsulating bundle. The reason code for the custody signal SHALL be the reason code from Figure 2 that indicates the reason for the custody transfer failure. . If the "request reporting of custody transfer attempted" flag in the encapsulating bundle's status report request field is set to 1, and status reporting is enabled, a custody transfer status report with the same reason code SHOULD be generated, destined for the report-to endpoint of the encapsulating bundle. . Otherwise: o The encapsulated bundle SHALL be delivered from the convergence layer adapter to the bundle protocol agent, whereupon bundle reception SHALL be performed as defined in section 5.6 of the Bundle Protocol specification (a work in progress) as usual: the encapsulated bundle may be forwarded, delivered, etc. o If and only if Custody Transfer was requested for this BPDU: . The BCLA SHALL generate a custody signal of type 0 (custody acceptance) referencing the encapsulated bundle, destined for the node that was the source of the encapsulating bundle. . If the "request reporting of custody transfer attempted" flag in the bundle's status report request field is set to 1, and status reporting is enabled, a custody transfer status report with reason code 0 SHOULD be generated, destined for the report-to endpoint of the encapsulating bundle. 4.3. Retransmission Timer Expiration Upon expiration of a retransmission countdown timer, the BCLA SHOULD destroy the retransmission timer, request that the BPDU be re- forwarded (possibly on a different route), and possibly establish a new retransmission timer. Burleigh Expires December 2017 [Page 9] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 4.4. Custody Signal Reception When a BCLA receives a custody signal from the bundle protocol agent (that is, upon delivery of the payload of a custody-signal-bearing bundle): . If the custody signal type is 0 (custody acceptance): o Any retransmission timer established for the referenced encapsulated bundle SHOULD be destroyed. o The bundle protocol agent MUST remove the retention constraint "Custody accepted" on the referenced encapsulated bundle. . Otherwise (custody refusal): o Any retransmission timer established for the referenced encapsulated bundle SHOULD be destroyed. o The action taken by the BCLA is implementation-specific and may depend on the reason code cited for the refusal. For example, if the custody signal's reason code was "Depleted storage", the BCLA might choose to request that the BPDU be re-forwarded (possibly on a different route) and possibly establish a new retransmission timer. If the reason code was "Redundant reception", on the other hand, this might cause the BCLA to instruct the bundle protocol agent to remove the retention constraint "Custody accepted" on the referenced encapsulated bundle and to revise its algorithm for computing countdown intervals for retransmission timers. 5. Security Considerations The BIBE specification introduces no new security considerations. 6. IANA Considerations The BIBE specification requires IANA registration of the new BIBE administrative record (type code 7) defined above. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Burleigh Expires December 2017 [Page 10] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 7.2. Informative References [RFC5050] Scott, M. and S. Burleigh, "Bundle Protocol Specification", RFC 5050, November 2007. 8. Acknowledgments This work is freely adapted from [RFC5050], which was an effort of the Delay Tolerant Networking Research Group. The following DTNRG participants contributed significant technical material and/or inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh, Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory, Michael Demmer of the University of California at Berkeley, Robert Durst, Keith Scott, and Susan Symington of The MITRE Corporation, Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity College Dublin, Peter Lovell of SPARTA, Inc., Manikantan Ramadas of Ohio University, and Howard Weiss of SPARTA, Inc. Although the BIBE specification diverges in some ways from the original Bundle-in-Bundle Encapsulation Internet Draft authored by usan Symington, Bob Durst, and Keith Scott of The MITRE Corporation (draft-irtf-dtnrg-bundle-encapsulation-06, 2009), the influence of that earlier document is gratefully acknowledged. This document was prepared using 2-Word-v2.0.template.dot. Burleigh Expires December 2017 [Page 11] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 Appendix A. For More Information Please refer comments to dtn@ietf.org. The Delay Tolerant Networking Research Group (DTNRG) Web site is located at http://www.dtnrg.org. Copyright (c) 2017 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). Burleigh Expires December 2017 [Page 12] Internet-Draft Bundle-in-Bundle Encapsulation June 2017 Appendix B. CDDL expression For informational purposes, Carsten Bormann has kindly provided an expression of the Bundle Protocol specification in the CBOR Data Definition Language (CDDL). Portions of CDDL expression that bear on the custody transfer extension are presented below, somewhat edited by the authors. Note that wherever the CDDL expression is in disagreement with the textual representation of the BP specification presented in the earlier sections of this document, the textual representation rules. bundleflagbits /= &( custody-transfer-status-reports-are-requested: 9 custody-transfer-is-requested: 3) extension-block-choice /= current-custodian-block current-custodian-block = [5, canonical-block-common, eid] admin-record-choice /= custody-signal custody-signal = [2, [custody-signal-type-code: uint, custody-signal-information, admin-common]] custody-signal-information = custody-reason-code: uint / delegation- information delegation-information = ( next-hop-node: eid, seconds-until-forwarding: uint) Authors' Address Scott Burleigh Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr. Pasadena, CA 91109-8099 US Phone: +1 818 393 3353 Email: Scott.Burleigh@jpl.nasa.gov Burleigh Expires December 2017 [Page 13]