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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'CRC' ** Obsolete normative reference: RFC 7049 (Obsoleted by RFC 8949) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Delay-Tolerant Networking Working Group S. Burleigh 2 Internet Draft JPL, Calif. Inst. Of Technology 3 Intended status: Standards Track K. Fall 4 Expires: February 2018 Nefeli Networks, Inc. 5 E. Birrane 6 APL, Johns Hopkins University 7 August 8, 2017 9 Bundle Protocol 10 draft-ietf-dtn-bpbis-08.txt 12 Status of this Memo 14 This Internet-Draft is submitted in full conformance with the 15 provisions of BCP 78 and BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six 23 months and may be updated, replaced, or obsoleted by other documents 24 at any time. It is inappropriate to use Internet-Drafts as 25 reference material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html 33 This Internet-Draft will expire on February 9, 2018. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with 45 respect to this document. Code Components extracted from this 46 document must include Simplified BSD License text as described in 47 Section 4.e of the Trust Legal Provisions and are provided without 48 warranty as described in the Simplified BSD License. 50 Abstract 52 This Internet Draft presents a specification for Bundle Protocol, 53 adapted from the experimental Bundle Protocol specification 54 developed by the Delay-Tolerant Networking Research group of the 55 Internet Research Task Force and documented in RFC 5050. 57 Table of Contents 59 1. Introduction...................................................3 60 2. Conventions used in this document..............................5 61 3. Service Description............................................5 62 3.1. Definitions...............................................5 63 3.2. Discussion of BP concepts.................................9 64 3.3. Services Offered by Bundle Protocol Agents...............11 65 4. Bundle Format.................................................12 66 4.1. BP Fundamental Data Structures...........................12 67 4.1.1. CRC Type............................................12 68 4.1.2. CRC.................................................13 69 4.1.3. Bundle Processing Control Flags.....................13 70 4.1.4. Block Processing Control Flags......................14 71 4.1.5. Identifiers.........................................15 72 4.1.5.1. Endpoint ID....................................15 73 4.1.5.2. Node ID........................................16 74 4.1.6. DTN Time............................................17 75 4.1.7. Creation Timestamp..................................17 76 4.1.8. Block-type-specific Data............................17 77 4.2. Bundle Representation....................................17 78 4.2.1. Bundle..............................................17 79 4.2.2. Primary Bundle Block................................18 80 4.2.3. Canonical Bundle Block Format.......................19 81 4.3. Extension Blocks.........................................20 82 4.3.1. Previous Node.......................................21 83 4.3.2. Bundle Age..........................................21 84 4.3.3. Hop Count...........................................22 85 5. Bundle Processing.............................................22 86 5.1. Generation of Administrative Records.....................23 87 5.2. Bundle Transmission......................................23 88 5.3. Bundle Dispatching.......................................24 89 5.4. Bundle Forwarding........................................24 90 5.4.1. Forwarding Contraindicated..........................26 91 5.4.2. Forwarding Failed...................................26 92 5.5. Bundle Expiration........................................26 93 5.6. Bundle Reception.........................................27 94 5.7. Local Bundle Delivery....................................27 95 5.8. Bundle Fragmentation.....................................28 96 5.9. Application Data Unit Reassembly.........................30 97 5.10. Bundle Deletion.........................................30 98 5.11. Discarding a Bundle.....................................30 99 5.12. Canceling a Transmission................................30 100 6. Administrative Record Processing..............................31 101 6.1. Administrative Records...................................31 102 6.1.1. Bundle Status Reports...............................32 103 6.2. Generation of Administrative Records.....................34 104 7. Services Required of the Convergence Layer....................34 105 7.1. The Convergence Layer....................................34 106 7.2. Summary of Convergence Layer Services....................35 107 8. Implementation Status.........................................35 108 9. Security Considerations.......................................36 109 10. IANA Considerations..........................................38 110 11. References...................................................39 111 11.1. Normative References....................................39 112 11.2. Informative References..................................39 113 12. Acknowledgments..............................................40 114 13. Significant Changes from RFC 5050............................40 115 Appendix A. For More Information.................................41 116 Appendix B. CDDL expression......................................42 118 1. Introduction 120 Since the publication of the Bundle Protocol Specification 121 (Experimental RFC 5050) in 2007, the Delay-Tolerant Networking 122 Bundle Protocol has been implemented in multiple programming 123 languages and deployed to a wide variety of computing platforms. 124 This implementation and deployment experience has identified 125 opportunities for making the protocol simpler, more capable, and 126 easier to use. The present document, standardizing the Bundle 127 Protocol (BP), is adapted from RFC 5050 in that context. 129 This document describes version 7 of BP. 131 Delay Tolerant Networking is a network architecture providing 132 communications in and/or through highly stressed environments. 133 Stressed networking environments include those with intermittent 134 connectivity, large and/or variable delays, and high bit error 135 rates. To provide its services, BP may be viewed as sitting at the 136 application layer of some number of constituent networks, forming a 137 store-carry-forward overlay network. Key capabilities of BP 138 include: 140 . Ability to use physical motility for the movement of data 141 . Ability to move the responsibility for error control from one 142 node to another 143 . Ability to cope with intermittent connectivity, including cases 144 where the sender and receiver are not concurrently present in 145 the network 146 . Ability to take advantage of scheduled, predicted, and 147 opportunistic connectivity, whether bidirectional or 148 unidirectional, in addition to continuous connectivity 149 . Late binding of overlay network endpoint identifiers to 150 underlying constituent network addresses 152 For descriptions of these capabilities and the rationale for the DTN 153 architecture, see [ARCH] and [SIGC]. 155 BP's location within the standard protocol stack is as shown in 156 Figure 1. BP uses underlying "native" transport and/or network 157 protocols for communications within a given constituent network. 159 The interface between the bundle protocol and a specific underlying 160 protocol is termed a "convergence layer adapter". 162 Figure 1 shows three distinct transport and network protocols 163 (denoted T1/N1, T2/N2, and T3/N3). 165 +-----------+ +-----------+ 166 | BP app | | BP app | 167 +---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+ 168 | BP v | | ^ BP v | | ^ BP v | | ^ BP | 169 +---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+ 170 | T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 | 171 +---------v-+ +-^---------v-+ +-^---------v + +-^---------+ 172 | N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 | 173 +---------v-+ +-^---------v + +-^---------v-+ +-^---------+ 174 | >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ | 175 +-----------+ +-------------+ +-------------+ +-----------+ 176 | | | | 177 |<---- A network ---->| |<---- A network ---->| 178 | | | | 180 Figure 1: The Bundle Protocol in the Protocol Stack Model 182 This document describes the format of the protocol data units 183 (called "bundles") passed between entities participating in BP 184 communications. 186 The entities are referred to as "bundle nodes". This document does 187 not address: 189 . Operations in the convergence layer adapters that bundle nodes 190 use to transport data through specific types of internets. 191 (However, the document does discuss the services that must be 192 provided by each adapter at the convergence layer.) 193 . The bundle route computation algorithm. 194 . Mechanisms for populating the routing or forwarding information 195 bases of bundle nodes. 196 . The mechanisms for securing bundles en route. 197 . The mechanisms for managing bundle nodes. 199 Note that implementations of the specification presented in this 200 document will not be interoperable with implementations of RFC 5050. 202 2. Conventions used in this document 204 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 205 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 206 document are to be interpreted as described in RFC-2119 [RFC2119]. 208 In this document, these words will appear with that interpretation 209 only when in ALL CAPS. Lower case uses of these words are not to be 210 interpreted as carrying RFC-2119 significance. 212 3. Service Description 214 3.1. Definitions 216 Bundle - A bundle is a protocol data unit of BP, so named because 217 negotiation of the parameters of a data exchange may be impractical 218 in a delay-tolerant network: it is often better practice to "bundle" 219 with a unit of data all metadata that might be needed in order to 220 make the data immediately usable when delivered to applications. 221 Each bundle comprises a sequence of two or more "blocks" of protocol 222 data, which serve various purposes. 224 Block - A bundle protocol block is one of the protocol data 225 structures that together constitute a well-formed bundle. 227 Bundle payload - A bundle payload (or simply "payload") is the 228 application data whose conveyance to the bundle's destination is the 229 purpose for the transmission of a given bundle; it is the content of 230 the bundle's payload block. The terms "bundle content", "bundle 231 payload", and "payload" are used interchangeably in this document. 233 Partial payload - A partial payload is a payload that comprises 234 either the first N bytes or the last N bytes of some other payload 235 of length M, such that 0 < N < M. Note that every partial payload 236 is a payload and therefore can be further subdivided into partial 237 payloads. 239 Fragment - A fragment is a bundle whose payload block contains a 240 partial payload. 242 Bundle node - A bundle node (or, in the context of this document, 243 simply a "node") is any entity that can send and/or receive bundles. 244 Each bundle node has three conceptual components, defined below, as 245 shown in Figure 2: a "bundle protocol agent", a set of zero or more 246 "convergence layer adapters", and an "application agent". 248 +-----------------------------------------------------------+ 249 |Node | 250 | | 251 | +-------------------------------------------------------+ | 252 | |Application Agent | | 253 | | | | 254 | | +--------------------------+ +----------------------+ | | 255 | | |Administrative element | |Application-specific | | | 256 | | | | |element | | | 257 | | | | | | | | 258 | | +--------------------------+ +----------------------+ | | 259 | | ^ ^ | | 260 | | Admin|records Application|data | | 261 | | | | | | 262 | +----------------v--------------------------v-----------+ | 263 | ^ | 264 | | ADUs | 265 | | | 266 | +-----------------------------v-------------------------+ | 267 | |Bundle Protocol Agent | | 268 | | | | 269 | | | | 270 | +-------------------------------------------------------+ | 271 | ^ ^ ^ | 272 | | Bundles | Bundles Bundles | | 273 | | | | | 274 | +------v-----+ +-----v------+ +-----v-----+ | 275 | |CLA 1 | |CLA 2 | |CLA n | | 276 | | | | | . . . | | | 277 | | | | | | | | 278 +-+------------+-----+------------+-----------+-----------+-+ 279 ^ ^ ^ 281 CL1|PDUs CL2|PDUs CLn|PDUs 282 | | | 283 +------v-----+ +-----v------+ +-----v-----+ 284 Network 1 Network 2 Network n 286 Figure 2: Components of a BP Node 288 Bundle protocol agent - The bundle protocol agent (BPA) of a node is 289 the node component that offers the BP services and executes the 290 procedures of the bundle protocol. 292 Convergence layer adapter - A convergence layer adapter (CLA) is a 293 node component that sends and receives bundles on behalf of the BPA, 294 utilizing the services of some 'native' protocol stack that is 295 supported in one of the networks within which the node is 296 functionally located. 298 Application agent - The application agent (AA) of a node is the node 299 component that utilizes the BP services to effect communication for 300 some user purpose. The application agent in turn has two elements, 301 an administrative element and an application-specific element. 303 Application-specific element - The application-specific element of 304 an AA is the node component that constructs, requests transmission 305 of, accepts delivery of, and processes units of user application 306 data. 308 Administrative element - The administrative element of an AA is the 309 node component that constructs and requests transmission of 310 administrative records (defined below), including status reports, 311 and accepts delivery of and processes any administrative records 312 that the node receives. 314 Administrative record - A BP administrative record is an application 315 data unit that is exchanged between the administrative elements of 316 nodes' application agents for some BP administrative purpose. The 317 only administrative record defined in this specification is the 318 status report, discussed later. 320 Bundle endpoint - A bundle endpoint (or simply "endpoint") is a set 321 of zero or more bundle nodes that all identify themselves for BP 322 purposes by some common identifier, called a "bundle endpoint ID" 323 (or, in this document, simply "endpoint ID"; endpoint IDs are 324 described in detail in Section 4.4.1 below). 326 Singleton endpoint - A singleton endpoint is an endpoint that always 327 contains exactly one member. 329 Registration - A registration is the state machine characterizing a 330 given node's membership in a given endpoint. Any single 331 registration has an associated delivery failure action as defined 332 below and must at any time be in one of two states: Active or 333 Passive. 335 Delivery - A bundle is considered to have been delivered at a node 336 subject to a registration as soon as the application data unit that 337 is the payload of the bundle, together with any relevant metadata 338 (an implementation matter), has been presented to the node's 339 application agent in a manner consistent with the state of that 340 registration. 342 Deliverability - A bundle is considered "deliverable" subject to a 343 registration if and only if (a) the bundle's destination endpoint is 344 the endpoint with which the registration is associated, (b) the 345 bundle has not yet been delivered subject to this registration, and 346 (c) the bundle has not yet been "abandoned" (as defined below) 347 subject to this registration. 349 Abandonment - To abandon a bundle subject to some registration is to 350 assert that the bundle is not deliverable subject to that 351 registration. 353 Delivery failure action - The delivery failure action of a 354 registration is the action that is to be taken when a bundle that is 355 "deliverable" subject to that registration is received at a time 356 when the registration is in the Passive state. 358 Destination - The destination of a bundle is the endpoint comprising 359 the node(s) at which the bundle is to be delivered (as defined 360 below). 362 Transmission - A transmission is an attempt by a node's BPA to cause 363 copies of a bundle to be delivered to one or more of the nodes that 364 are members of some endpoint (the bundle's destination) in response 365 to a transmission request issued by the node's application agent. 367 Forwarding - To forward a bundle to a node is to invoke the services 368 of one or more CLAs in a sustained effort to cause a copy of the 369 bundle to be received by that node. 371 Discarding - To discard a bundle is to cease all operations on the 372 bundle and functionally erase all references to it. The specific 373 procedures by which this is accomplished are an implementation 374 matter. 376 Retention constraint - A retention constraint is an element of the 377 state of a bundle that prevents the bundle from being discarded. 378 That is, a bundle cannot be discarded while it has any retention 379 constraints. 381 Deletion - To delete a bundle is to remove unconditionally all of 382 the bundle's retention constraints, enabling the bundle to be 383 discarded. 385 3.2. Discussion of BP concepts 387 Multiple instances of the same bundle (the same unit of DTN protocol 388 data) might exist concurrently in different parts of a network -- 389 possibly differing in some blocks -- in the memory local to one or 390 more bundle nodes and/or in transit between nodes. In the context of 391 the operation of a bundle node, a bundle is an instance (copy), in 392 that node's local memory, of some bundle that is in the network. 394 The payload for a bundle forwarded in response to a bundle 395 transmission request is the application data unit whose location is 396 provided as a parameter to that request. The payload for a bundle 397 forwarded in response to reception of a bundle is the payload of the 398 received bundle. 400 In the most familiar case, a bundle node is instantiated as a single 401 process running on a general-purpose computer, but in general the 402 definition is meant to be broader: a bundle node might alternatively 403 be a thread, an object in an object-oriented operating system, a 404 special-purpose hardware device, etc. 406 The manner in which the functions of the BPA are performed is wholly 407 an implementation matter. For example, BPA functionality might be 408 coded into each node individually; it might be implemented as a 409 shared library that is used in common by any number of bundle nodes 410 on a single computer; it might be implemented as a daemon whose 411 services are invoked via inter-process or network communication by 412 any number of bundle nodes on one or more computers; it might be 413 implemented in hardware. 415 Every CLA implements its own thin layer of protocol, interposed 416 between BP and the (usually "top") protocol(s) of the underlying 417 native protocol stack; this "CL protocol" may only serve to 418 multiplex and de-multiplex bundles to and from the underlying native 419 protocol, or it may offer additional CL-specific functionality. The 420 manner in which a CLA sends and receives bundles, as well as the 421 definitions of CLAs and CL protocols, are beyond the scope of this 422 specification. 424 Note that the administrative element of a node's application agent 425 may itself, in some cases, function as a convergence-layer adapter. 426 That is, outgoing bundles may be "tunneled" through encapsulating 427 bundles: 429 . An outgoing bundle constitutes a byte array. This byte array 430 may, like any other, be presented to the bundle protocol agent 431 as an application data unit that is to be transmitted to some 432 endpoint. 433 . The original bundle thus forms the payload of an encapsulating 434 bundle that is forwarded using some other convergence-layer 435 protocol(s). 436 . When the encapsulating bundle is received, its payload is 437 delivered to the peer application agent administrative element, 438 which then instructs the bundle protocol agent to dispatch that 439 original bundle in the usual way. 441 The purposes for which this technique may be useful (such as cross- 442 domain security) are beyond the scope of this specification. 444 The only interface between the BPA and the application-specific 445 element of the AA is the BP service interface. But between the BPA 446 and the administrative element of the AA there is a (conceptual) 447 private control interface in addition to the BP service interface. 448 This private control interface enables the BPA and the 449 administrative element of the AA to direct each other to take action 450 under specific circumstances. 452 In the case of a node that serves simply as a BP "router", the AA 453 may have no application-specific element at all. The application- 454 specific elements of other nodes' AAs may perform arbitrarily 455 complex application functions, perhaps even offering multiplexed DTN 456 communication services to a number of other applications. As with 457 the BPA, the manner in which the AA performs its functions is wholly 458 an implementation matter. 460 Singletons are the most familiar sort of endpoint, but in general 461 the endpoint notion is meant to be broader. For example, the nodes 462 in a sensor network might constitute a set of bundle nodes that 463 identify themselves by a single common endpoint ID and thus form a 464 single bundle endpoint. *Note* too that a given bundle node might 465 identify itself by multiple endpoint IDs and thus be a member of 466 multiple bundle endpoints. 468 The destination of every bundle is an endpoint, which may or may not 469 be singleton. The source of every bundle is a node, identified by 470 the endpoint ID for some singleton endpoint that contains that node. 472 Any number of transmissions may be concurrently undertaken by the 473 bundle protocol agent of a given node. 475 When the bundle protocol agent of a node determines that a bundle 476 must be forwarded to a node (either to a node that is a member of 477 the bundle's destination endpoint or to some intermediate forwarding 478 node) in the course of completing the successful transmission of 479 that bundle, it invokes the services of one or more CLAs in a 480 sustained effort to cause a copy of the bundle to be received by 481 that node. 483 Upon reception, the processing of a bundle that has been received by 484 a given node depends on whether or not the receiving node is 485 registered in the bundle's destination endpoint. If it is, and if 486 the payload of the bundle is non-fragmentary (possibly as a result 487 of successful payload reassembly from fragmentary payloads, 488 including the original payload of the newly received bundle), then 489 the bundle is normally delivered to the node's application agent 490 subject to the registration characterizing the node's membership in 491 the destination endpoint. 493 The bundle protocol does not natively ensure delivery of a bundle to 494 its destination. Data loss along the path to the destination node 495 can be minimized by utilizing reliable convergence-layer protocols 496 between neighbors on all segments of the end-to-end path, but for 497 end-to-end bundle delivery assurance it will be necessary to develop 498 extensions to the bundle protocol and/or application-layer 499 mechanisms. 501 The bundle protocol is designed for extensibility. Bundle protocol 502 extensions, documented elsewhere, may extend this specification by: 504 . defining additional blocks; 505 . defining additional administrative records; 506 . defining additional bundle processing flags; 507 . defining additional block processing flags; 508 . defining additional types of bundle status reports; 509 . defining additional bundle status report reason codes; 510 . defining additional mandates and constraints on processing 511 that conformant bundle protocol agents must perform at 512 specified points in the inbound and outbound bundle processing 513 cycles. 515 3.3. Services Offered by Bundle Protocol Agents 517 The BPA of each node is expected to provide the following services 518 to the node's application agent: 520 . commencing a registration (registering the node in an 521 endpoint); 522 . terminating a registration; 523 . switching a registration between Active and Passive states; 524 . transmitting a bundle to an identified bundle endpoint; 525 . canceling a transmission; 526 . polling a registration that is in the Passive state; 527 . delivering a received bundle. 529 4. Bundle Format 531 The format of bundles SHALL conform to the Concise Binary Object 532 Representation (CBOR [RFC7049]). 534 Each bundle SHALL be a concatenated sequence of at least two blocks, 535 represented as a CBOR indefinite-length array. The first block in 536 the sequence (the first item of the array) MUST be a primary bundle 537 block in CBOR representation as described below; the bundle MUST 538 have exactly one primary bundle block. The primary block MUST be 539 followed by one or more canonical bundle blocks (additional array 540 items) in CBOR representation as described below. The last such 541 block MUST be a payload block; the bundle MUST have exactly one 542 payload block. The last item of the array, immediately following 543 the payload block, SHALL be a CBOR "break" stop code. 545 An implementation of the Bundle Protocol MAY discard any sequence of 546 bytes that does not conform to the Bundle Protocol specification. 548 An implementation of the Bundle Protocol MAY accept a sequence of 549 bytes that does not conform to the Bundle Protocol specification 550 (e.g., one that represents data elements in fixed-length arrays 551 rather than indefinite-length arrays) and transform it into 552 conformant BP structure before processing it. Procedures for 553 accomplishing such a transformation are beyond the scope of this 554 specification. 556 4.1. BP Fundamental Data Structures 558 4.1.1. CRC Type 560 CRC type is an unsigned integer type code for which the following 561 values (and no others) are valid: 563 . 0 indicates "no CRC is present." 564 . 1 indicates "a standard X-25 CRC-16 is present." [CRC] 565 . 2 indicates "a standard PKZIP CRC-32 is present." [CRC] 567 CRC type SHALL be represented as a CBOR unsigned integer. 569 4.1.2. CRC 571 CRC SHALL be omitted from a block if and only if the block's CRC 572 type code is zero. 574 When not omitted, the CRC SHALL be represented as sequence of two 575 bytes (if CRC type is 1) or as a sequence of four bytes (if CRC type 576 is 2). 578 4.1.3. Bundle Processing Control Flags 580 Bundle processing control flags assert properties of the bundle as a 581 whole rather than of any particular block of the bundle. They are 582 conveyed in the primary block of the bundle. 584 The following properties are asserted by the bundle processing 585 control flags: 587 . The bundle is a fragment. (Boolean) 589 . The bundle's payload is an administrative record. (Boolean) 591 . The bundle must not be fragmented. (Boolean) 593 . The bundle's destination endpoint is a singleton. (Boolean) 595 . Acknowledgment by the user application is requested. (Boolean) 597 . Status time is requested in all status reports. (Boolean) 599 . The bundle contains a "manifest" extension block. (Boolean) 601 . Flags requesting types of status reports (all Boolean): 603 o Request reporting of bundle reception. 605 o Request reporting of bundle forwarding. 607 o Request reporting of bundle delivery. 609 o Request reporting of bundle deletion. 611 If the bundle processing control flags indicate that the bundle's 612 application data unit is an administrative record, then all status 613 report request flag values must be zero. 615 If the bundle's source node is omitted (i.e., the source node ID is 616 the ID of the null endpoint, which has no members as discussed 617 below; this option enables anonymous bundle transmission), then the 618 bundle is not uniquely identifiable and all bundle protocol features 619 that rely on bundle identity must therefore be disabled: the "Bundle 620 must not be fragmented" flag value must be 1 and all status report 621 request flag values must be zero. 623 The bundle processing control flags SHALL be represented as a CBOR 624 unsigned integer item containing a bit field of 16 bits indicating 625 the control flag values as follows: 627 . Bit 0 (the high-order bit, 0x8000): reserved. 628 . Bit 1 (0x4000): reserved. 629 . Bit 2 (0x2000): reserved. 630 . Bit 3(0x1000): bundle deletion status reports are requested. 631 . Bit 4(0x0800): bundle delivery status reports are requested. 632 . Bit 5(0x0400): bundle forwarding status reports are requested. 633 . Bit 6(0x0200): reserved. 634 . Bit 7(0x0100): bundle reception status reports are requested. 635 . Bit 8(0x0080): bundle contains a Manifest block. 636 . Bit 9(0x0040): status time is requested in all status reports. 637 . Bit 10(0x0020): user application acknowledgement is requested. 638 . Bit 11(0x0010): destination is a singleton endpoint. 639 . Bit 12(0x0008): reserved. 640 . Bit 13(0x0004): bundle must not be fragmented. 641 . Bit 14(0x0002): payload is an administrative record. 642 . Bit 15 (the low-order bit, 0x0001: bundle is a fragment. 644 4.1.4. Block Processing Control Flags 646 The block processing control flags assert properties of canonical 647 bundle blocks. They are conveyed in the header of the block to 648 which they pertain. 650 The following properties are asserted by the block processing 651 control flags: 653 . This block must be replicated in every fragment. (Boolean) 655 . Transmission of a status report is requested if this block 656 can't be processed. (Boolean) 658 . Block must be removed from the bundle if it can't be processed. 659 (Boolean) 661 . Bundle must be deleted if this block can't be processed. 662 (Boolean) 664 For each bundle whose bundle processing control flags indicate that 665 the bundle's application data unit is an administrative record, or 666 whose source node ID is the null endpoint ID as defined below, the 667 value of the "Transmit status report if block can't be processed" 668 flag in every canonical block of the bundle must be zero. 670 The block processing control flags SHALL be represented as a CBOR 671 unsigned integer item containing a bit field of 8 bits indicating 672 the control flag values as follows: 674 . Bit 0 (the high-order bit, 0x80): reserved. 675 . Bit 1 (0x40): reserved. 676 . Bit 2(0x20): reserved. 677 . Bit 3(0x10): reserved. 678 . Bit 4(0x08): bundle must be deleted if block can't be 679 processed. 680 . Bit 5(0x04): transmission of a status report is requested if 681 block can't be processed. 682 . Bit 6(0x02): block must be removed from bundle if it can't be 683 processed. 684 . Bit 7(the low-order bit, 0x01): block must be replicated in 685 every fragment. 687 4.1.5. Identifiers 689 4.1.5.1. Endpoint ID 691 The destinations of bundles are bundle endpoints, identified by text 692 strings termed "endpoint IDs" (see Section 3.1). Each endpoint ID 693 (EID) is a Uniform Resource Identifier (URI; [URI]). As such, each 694 endpoint ID can be characterized as having this general structure: 696 < scheme name > : < scheme-specific part, or "SSP" > 698 The scheme identified by the < scheme name > in an endpoint ID is a 699 set of syntactic and semantic rules that fully explain how to parse 700 and interpret the SSP. The set of allowable schemes is effectively 701 unlimited. Any scheme conforming to [URIREG] may be used in a bundle 702 protocol endpoint ID. 704 Note that, although endpoint IDs are URIs, implementations of the BP 705 service interface may support expression of endpoint IDs in some 706 internationalized manner (e.g., Internationalized Resource 707 Identifiers (IRIs); see [RFC3987]). 709 The endpoint ID "dtn:none" identifies the "null endpoint", the 710 endpoint that by definition never has any members. 712 Each BP endpoint ID (EID) SHALL be represented as a CBOR array 713 comprising a 2-tuple. 715 The first item of the array SHALL be the code number identifying the 716 endpoint's URI scheme [URI], as defined in the registry of URI 717 scheme code numbers for Bundle Protocol maintained by IANA as 718 described in Section 10. [URIREG]. Each URI scheme code number 719 SHALL be represented as a CBOR unsigned integer. 721 The second item of the array SHALL be the applicable CBOR 722 representation of the scheme-specific part (SSP) of the EID, defined 723 as follows: 725 . If the EID's URI scheme is "dtn" then the SSP SHALL be 726 represented as a CBOR text string unless the EID's SSP is 727 "none", in which case the SSP SHALL be represented as a CBOR 728 unsigned integer with the value zero. 729 . If the EID's URI scheme is "ipn" then the SSP SHALL be 730 represented as a CBOR array comprising a 2-tuple. The first 731 item of this array SHALL be the EID's node number represented 732 as a CBOR unsigned integer. The second item of this array 733 SHALL be the EID's service number represented as a CBOR 734 unsigned integer. 735 . Definitions of the CBOR representations of the SSPs of EIDs 736 encoded in other URI schemes are included in the specifications 737 defining those schemes. 739 4.1.5.2. Node ID 741 For many purposes of the Bundle Protocol it is important to identify 742 the node that is operative in some context. 744 As discussed in 3.1 above, nodes are distinct from endpoints; 745 specifically, an endpoint is a set of zero or more nodes. But 746 rather than define a separate namespace for node identifiers, we 747 instead use endpoint identifiers to identify nodes, subject to the 748 following restrictions: 750 . Every node MUST be a member of at least one singleton endpoint. 751 . The EID of any singleton endpoint of which a node is a member 752 MAY be used to identify that node. A "node ID" is an EID that 753 is used in this way. 754 . A node's membership in a given singleton endpoint MUST be 755 sustained at least until the nominal operation of the Bundle 756 Protocol no longer depends on the identification of that node 757 using that endpoint's ID. 759 4.1.6. DTN Time 761 A DTN time is an unsigned integer indicating a count of seconds 762 since the start of the year 2000 on the Coordinated Universal Time 763 (UTC) scale [UTC]. Each DTN time SHALL be represented as a CBOR 764 unsigned integer item. 766 4.1.7. Creation Timestamp 768 Each creation timestamp SHALL be represented as a CBOR array item 769 comprising a 2-tuple. 771 The first item of the array SHALL be a DTN time. 773 The second item of the array SHALL be the creation timestamp's 774 sequence number, represented as a CBOR unsigned integer. 776 4.1.8. Block-type-specific Data 778 Block-type-specific data in each block (other than the primary 779 block) SHALL be the applicable CBOR representation of the content of 780 the block. Details of this representation are included in the 781 specification defining the block type. 783 4.2. Bundle Representation 785 This section describes the primary block in detail and non-primary 786 blocks in general. Rules for processing these blocks appear in 787 Section 5 of this document. 789 Note that supplementary DTN protocol specifications (including, but 790 not restricted to, the Bundle Security Protocol [BPSEC]) may require 791 that BP implementations conforming to those protocols construct and 792 process additional blocks. 794 4.2.1. Bundle 796 Each bundle SHALL be represented as a CBOR indefinite-length array. 797 The first item of this array SHALL be the CBOR representation of a 798 Primary Block. Every other item of the array except the last SHALL 799 be the CBOR representation of a Canonical Block. The last item of 800 the array SHALL be a CBOR "break" stop code. 802 4.2.2. Primary Bundle Block 804 The primary bundle block contains the basic information needed to 805 forward bundles to their destinations. 807 Each primary block SHALL be represented as a CBOR array; the number 808 of elements in the array SHALL be 8 (if the bundle is not a fragment 809 and CRC type is zero) or 9 (if the bundle is not a fragment and CRC 810 type is non-zero) or 10 (if the bundle is a fragment and CRC type is 811 zero) or 11 (if the bundle is a fragment and CRC-type is non-zero). 813 The fields of the primary bundle block SHALL be as follows, listed 814 in the order in which they MUST appear: 816 Version: An unsigned integer value indicating the version of the 817 bundle protocol that constructed this block. The present document 818 describes version 7 of the bundle protocol. Version number SHALL be 819 represented as a CBOR unsigned integer item. 821 Bundle Processing Control Flags: The Bundle Processing Control Flags 822 are discussed in Section 4.1.3. above. 824 CRC Type: CRC Type codes are discussed in Section 4.1.1. above. 826 Destination EID: The Destination EID field identifies the bundle 827 endpoint that is the bundle's destination, i.e., the endpoint that 828 contains the node(s) at which the bundle is to be delivered. 830 Source node ID: The Source node ID field identifies the bundle node 831 at which the bundle was initially transmitted, except that Source 832 node ID may be the null endpoint ID in the event that the bundle's 833 source chooses to remain anonymous. 835 Report-to EID: The Report-to EID field identifies the bundle 836 endpoint to which status reports pertaining to the forwarding and 837 delivery of this bundle are to be transmitted. 839 Creation Timestamp: The creation timestamp is a pair of unsigned 840 integers that, together with the source node ID and (if the bundle 841 is a fragment) the fragment offset and payload length, serve to 842 identify the bundle. The first of these integers is the bundle's 843 creation time, while the second is the bundle's creation timestamp 844 sequence number. Bundle creation time shall be the time - expressed 845 in seconds since the start of the year 2000, on the Coordinated 846 Universal Time (UTC) scale [UTC] - at which the transmission request 847 was received that resulted in the creation of the bundle. Sequence 848 count shall be the latest value (as of the time at which that 849 transmission request was received) of a monotonically increasing 850 positive integer counter managed by the source node's bundle 851 protocol agent that may be reset to zero whenever the current time 852 advances by one second. For nodes that lack accurate clocks, it is 853 recommended that bundle creation time be set to zero and that the 854 counter used as the source of the bundle sequence count never be 855 reset to zero. Note that, in general, the creation of two distinct 856 bundles with the same source node ID and bundle creation timestamp 857 may result in unexpected network behavior and/or suboptimal 858 performance. The combination of source node ID and bundle creation 859 timestamp serves to identify a single transmission request, enabling 860 it to be acknowledged by the receiving application (provided the 861 source node ID is not the null endpoint ID). 863 Lifetime: The lifetime field is an unsigned integer that indicates 864 the time at which the bundle's payload will no longer be useful, 865 encoded as a number of microseconds past the creation time. (For 866 high-rate deployments with very brief disruptions, fine-grained 867 expression of bundle lifetime may be useful.) When a bundle's age 868 exceeds its lifetime, bundle nodes need no longer retain or forward 869 the bundle; the bundle SHOULD be deleted from the network. Bundle 870 lifetime SHALL be represented as a CBOR unsigned integer item. 872 Fragment offset: If and only if the Bundle Processing Control Flags 873 of this Primary block indicate that the bundle is a fragment, 874 fragment offset SHALL be present in the primary block. Fragment 875 offset SHALL be represented as a CBOR unsigned integer indicating 876 the offset from the start of the original application data unit at 877 which the bytes comprising the payload of this bundle were located. 879 CRC: If and only if the value of the CRC type field of this Primary 880 block is non-zero, a CRC SHALL be present in the primary block. The 881 length and nature of the CRC SHALL be as indicated by the CRC type. 882 The CRC SHALL be computed over the concatenation of all bytes 883 (including CBOR "break" characters) of the primary block including 884 the CRC field itself, which for this purpose SHALL be temporarily 885 populated with the value zero. 887 4.2.3. Canonical Bundle Block Format 889 Every block other than the primary block (which blocks are termed 890 "canonical" blocks) SHALL be represented as a CBOR array; the number 891 of elements in the array SHALL be 6 (if CRC type is zero) or 7 892 (otherwise). 894 The fields of every canonical block SHALL be as follows, listed in 895 the order in which they MUST appear: 897 . Block type code, an unsigned integer. Bundle block type code 1 898 indicates that the block is a bundle payload block. Block type 899 codes 2 through 9 are explicitly reserved as noted later in 900 this specification. Block type codes 192 through 255 are not 901 reserved and are available for private and/or experimental use. 902 All other block type code values are reserved for future use. 903 . Block number, an unsigned integer. The block number uniquely 904 identifies the block within the bundle, enabling blocks 905 (notably bundle security protocol blocks) to explicitly 906 reference other blocks in the same bundle. Block numbers need 907 not be in continuous sequence, and blocks need not appear in 908 block number sequence in the bundle. The block number of the 909 payload block is always zero. 910 . Block processing control flags as discussed in Section 4.1.4 911 above. 912 . CRC type as discussed in Section 4.1.1 above. 913 . Block data length, an unsigned integer. The block data length 914 field SHALL contain the aggregate length of all remaining 915 fields of the block, i.e., the block-type-specific data fields. 916 Block data length SHALL be represented as a CBOR unsigned 917 integer item. 918 . Block-type-specific data fields, whose nature and order are 919 type-specific and whose aggregate length in octets is the value 920 of the block data length field. For the Payload Block in 921 particular (block type 1), there SHALL be exactly one block- 922 type-specific data field, termed the "payload", which SHALL be 923 an application data unit, or some contiguous extent thereof, 924 represented as a CBOR byte string. 925 . If and only if the value of the CRC type field of this block is 926 non-zero, a CRC. If present, the length and nature of the CRC 927 SHALL be as indicated by the CRC type and the CRC SHALL be 928 computed over the concatenation of all bytes of the block 929 (including CBOR "break" characters) including the CRC field 930 itself, which for this purpose SHALL be temporarily populated 931 with the value zero. 933 4.3. Extension Blocks 935 "Extension blocks" are all blocks other than the primary and payload 936 blocks. Because not all extension blocks are defined in the Bundle 937 Protocol specification (the present document), not all nodes 938 conforming to this specification will necessarily instantiate Bundle 939 Protocol implementations that include procedures for processing 940 (that is, recognizing, parsing, acting on, and/or producing) all 941 extension blocks. It is therefore possible for a node to receive a 942 bundle that includes extension blocks that the node cannot process. 944 The values of the block processing control flags indicate the action 945 to be taken by the bundle protocol agent when this is the case. 947 (Note that, while CBOR permits considerable flexibility in the 948 encoding of bundles, this flexibility must not be interpreted as 949 inviting increased complexity in protocol data unit structure.) 951 The following extension blocks are defined in other DTN protocol 952 specification documents as noted: 954 . Block Integrity Block (block type 2) and Block Confidentiality 955 Block (block type 3) are defined in the Bundle Security 956 Protocol specification (work in progress). 957 . Manifest Block (block type 4) is defined in the Manifest 958 Extension Block specification (work in progress). The manifest 959 block identifies the blocks that were present in the bundle at 960 the time it was created. The bundle MUST contain one (1) 961 occurrence of this type of block if the value of the "manifest" 962 flag in the bundle processing control flags is 1; otherwise the 963 bundle MUST NOT contain any Manifest block. 964 . The Flow Label Block (block type 6) is defined in the Flow 965 Label Extension Block specification (work in progress). The 966 flow label block is intended to govern transmission of the 967 bundle by convergence-layer adapters. 969 The following extension blocks are defined in the current document. 971 4.3.1. Previous Node 973 The Previous Node block, block type 7, identifies the node that 974 forwarded this bundle to the local node (i.e., to the node at which 975 the bundle currently resides); its block-type-specific data is the 976 node ID of that forwarder node which SHALL take the form of a node 977 ID represented as described in Section 4.1.5.2. above. If the local 978 node is the source of the bundle, then the bundle MUST NOT contain 979 any previous node block. Otherwise the bundle SHOULD contain one 980 (1) occurrence of this type of block. 982 4.3.2. Bundle Age 984 The Bundle Age block, block type 8, contains the number of seconds 985 that have elapsed between the time the bundle was created and time 986 at which it was most recently forwarded. It is intended for use by 987 nodes lacking access to an accurate clock, to aid in determining the 988 time at which a bundle's lifetime expires. The block-type-specific 989 data of this block is an unsigned integer containing the age of the 990 bundle in seconds, which SHALL be represented as a CBOR unsigned 991 integer item. (The age of the bundle is the sum of all known 992 intervals of the bundle's residence at forwarding nodes, up to the 993 time at which the bundle was most recently forwarded, plus the 994 summation of signal propagation time over all episodes of 995 transmission between forwarding nodes. Determination of these 996 values is an implementation matter.) If the bundle's creation time 997 is zero, then the bundle MUST contain exactly one (1) occurrence of 998 this type of block; otherwise, the bundle MAY contain at most one 999 (1) occurrence of this type of block. A bundle MUST NOT contain 1000 multiple occurrences of the bundle age block, as this could result 1001 in processing anomalies. 1003 4.3.3. Hop Count 1005 The Hop Count block, block type 9, contains two unsigned integers, 1006 hop limit and hop count. A "hop" is here defined as an occasion on 1007 which a bundle was forwarded from one node to another node. The hop 1008 limit value SHOULD NOT be changed at any time after creation of the 1009 Hop Count block; the hop count value SHOULD initially be zero and 1010 SHOULD be increased by 1 on each hop. 1012 The hop count block is mainly intended as a safety mechanism, a 1013 means of identifying bundles for removal from the network that can 1014 never be delivered due to a persistent forwarding error. When a 1015 bundle's hop count exceeds its hop limit, the bundle SHOULD be 1016 deleted for the reason "hop limit exceeded", following the bundle 1017 deletion procedure defined in Section 5.10. . Procedures for 1018 determining the appropriate hop limit for a block are beyond the 1019 scope of this specification. The block-type-specific data in a hop 1020 count block SHALL be represented as a CBOR array comprising a 2- 1021 tuple. The first item of this array SHALL be the bundle's hop 1022 limit, represented as a CBOR unsigned integer. The second item of 1023 this array SHALL be the bundle's hop count, represented as a CBOR 1024 unsigned integer. A bundle MAY contain at most one (1) occurrence of 1025 this type of block. 1027 5. Bundle Processing 1029 The bundle processing procedures mandated in this section and in 1030 Section 6 govern the operation of the Bundle Protocol Agent and the 1031 Application Agent administrative element of each bundle node. They 1032 are neither exhaustive nor exclusive. Supplementary DTN protocol 1033 specifications (including, but not restricted to, the Bundle 1034 Security Protocol [BPSEC]) may augment, override, or supersede the 1035 mandates of this document. 1037 5.1. Generation of Administrative Records 1039 All transmission of bundles is in response to bundle transmission 1040 requests presented by nodes' application agents. When required to 1041 "generate" an administrative record (such as a bundle status 1042 report), the bundle protocol agent itself is responsible for causing 1043 a new bundle to be transmitted, conveying that record. In concept, 1044 the bundle protocol agent discharges this responsibility by 1045 directing the administrative element of the node's application agent 1046 to construct the record and request its transmission as detailed in 1047 Section 6 below. In practice, the manner in which administrative 1048 record generation is accomplished is an implementation matter, 1049 provided the constraints noted in Section 6 are observed. 1051 Under some circumstances, the requesting of status reports could 1052 result in an unacceptable increase in the bundle traffic in the 1053 network. For this reason, the generation of status reports MUST be 1054 disabled by default and enabled only when the risk of excessive 1055 network traffic is deemed acceptable. 1057 When the generation of status reports is enabled, the decision on 1058 whether or not to generate a requested status report is left to the 1059 discretion of the bundle protocol agent. Mechanisms that could 1060 assist in making such decisions, such as pre-placed agreements 1061 authorizing the generation of status reports under specified 1062 circumstances, are beyond the scope of this specification. 1064 Notes on administrative record terminology: 1066 . A "bundle reception status report" is a bundle status report 1067 with the "reporting node received bundle" flag set to 1. 1068 . A "bundle forwarding status report" is a bundle status report 1069 with the "reporting node forwarded the bundle" flag set to 1. 1070 . A "bundle delivery status report" is a bundle status report 1071 with the "reporting node delivered the bundle" flag set to 1. 1072 . A "bundle deletion status report" is a bundle status report 1073 with the "reporting node deleted the bundle" flag set to 1. 1075 5.2. Bundle Transmission 1077 The steps in processing a bundle transmission request are: 1079 Step 1: Transmission of the bundle is initiated. An outbound bundle 1080 MUST be created per the parameters of the bundle transmission 1081 request, with the retention constraint "Dispatch pending". The 1082 source node ID of the bundle MUST be either the null endpoint ID, 1083 indicating that the source of the bundle is anonymous, or else the 1084 EID of a singleton endpoint whose only member is the node of which 1085 the BPA is a component. 1087 Step 2: Processing proceeds from Step 1 of Section 5.4. 1089 5.3. Bundle Dispatching 1091 The steps in dispatching a bundle are: 1093 Step 1: If the bundle's destination endpoint is an endpoint of which 1094 the node is a member, the bundle delivery procedure defined in 1095 Section 5.7 MUST be followed. 1097 Step 2: Processing proceeds from Step 1 of Section 5.4. 1099 5.4. Bundle Forwarding 1101 The steps in forwarding a bundle are: 1103 Step 1: The retention constraint "Forward pending" MUST be added to 1104 the bundle, and the bundle's "Dispatch pending" retention constraint 1105 MUST be removed. 1107 Step 2: The bundle protocol agent MUST determine whether or not 1108 forwarding is contraindicated for any of the reasons listed in 1109 Figure 4. In particular: 1111 . The bundle protocol agent MAY choose either to forward the 1112 bundle directly to its destination node(s) (if possible) or to 1113 forward the bundle to some other node(s) for further 1114 forwarding. The manner in which this decision is made may 1115 depend on the scheme name in the destination endpoint ID and/or 1116 on other state but in any case is beyond the scope of this 1117 document. If the BPA elects to forward the bundle to some other 1118 node(s) for further forwarding but finds it impossible to 1119 select any node(s) to forward the bundle to, then forwarding is 1120 contraindicated. 1121 . Provided the bundle protocol agent succeeded in selecting the 1122 node(s) to forward the bundle to, the bundle protocol agent 1123 MUST select the convergence layer adapter(s) whose services 1124 will enable the node to send the bundle to those nodes. The 1125 manner in which specific appropriate convergence layer adapters 1126 are selected is beyond the scope of this document. If the agent 1127 finds it impossible to select any appropriate convergence layer 1128 adapter(s) to use in forwarding this bundle, then forwarding is 1129 contraindicated. 1131 Step 3: If forwarding of the bundle is determined to be 1132 contraindicated for any of the reasons listed in Figure 4, then the 1133 Forwarding Contraindicated procedure defined in Section 5.4.1 MUST 1134 be followed; the remaining steps of Section 5 are skipped at this 1135 time. 1137 Step 4: For each node selected for forwarding, the bundle protocol 1138 agent MUST invoke the services of the selected convergence layer 1139 adapter(s) in order to effect the sending of the bundle to that 1140 node. Determining the time at which the bundle protocol agent 1141 invokes convergence layer adapter services is a BPA implementation 1142 matter. Determining the time at which each convergence layer 1143 adapter subsequently responds to this service invocation by sending 1144 the bundle is a convergence-layer adapter implementation matter. 1145 Note that: 1147 . If the bundle contains a flow label extension block (to be 1148 defined in a future document) then that flow label value MAY 1149 identify procedures for determining the order in which 1150 convergence layer adapters must send bundles, e.g., considering 1151 bundle source when determining the order in which bundles are 1152 sent. The definition of such procedures is beyond the scope of 1153 this specification. 1154 . If the bundle has a bundle age block, as defined in 4.3.2. 1155 above, then at the last possible moment before the CLA 1156 initiates conveyance of the bundle node via the CL protocol the 1157 bundle age value MUST be increased by the difference between 1158 the current time and the time at which the bundle was received 1159 (or, if the local node is the source of the bundle, created). 1161 Step 5: When all selected convergence layer adapters have informed 1162 the bundle protocol agent that they have concluded their data 1163 sending procedures with regard to this bundle: 1165 . If the "request reporting of bundle forwarding" flag in the 1166 bundle's status report request field is set to 1, and status 1167 reporting is enabled, then a bundle forwarding status report 1168 SHOULD be generated, destined for the bundle's report-to 1169 endpoint ID. The reason code on this bundle forwarding status 1170 report MUST be "no additional information". 1171 . If any applicable bundle protocol extensions mandate generation 1172 of status reports upon conclusion of convergence-layer data 1173 sending procedures, all such status reports SHOULD be generated 1174 with extension-mandated reason codes. 1175 . The bundle's "Forward pending" retention constraint MUST be 1176 removed. 1178 5.4.1. Forwarding Contraindicated 1180 The steps in responding to contraindication of forwarding are: 1182 Step 1: The bundle protocol agent MUST determine whether or not to 1183 declare failure in forwarding the bundle. Note: this decision is 1184 likely to be influenced by the reason for which forwarding is 1185 contraindicated. 1187 Step 2: If forwarding failure is declared, then the Forwarding 1188 Failed procedure defined in Section 5.4.2 MUST be followed. 1190 Otherwise, when -- at some future time - the forwarding of this 1191 bundle ceases to be contraindicated, processing proceeds from Step 4 1192 of Section 5.4. 1194 5.4.2. Forwarding Failed 1196 The steps in responding to a declaration of forwarding failure are: 1198 Step 1: The bundle protocol agent MAY forward the bundle back to the 1199 node that sent it, as identified by the Previous Node block, if 1200 present. 1202 Step 2: If the bundle's destination endpoint is an endpoint of which 1203 the node is a member, then the bundle's "Forward pending" retention 1204 constraint MUST be removed. Otherwise, the bundle MUST be deleted: 1205 the bundle deletion procedure defined in Section 5.14 MUST be 1206 followed, citing the reason for which forwarding was determined to 1207 be contraindicated. 1209 5.5. Bundle Expiration 1211 A bundle expires when the bundle's age exceeds its lifetime as 1212 specified in the primary bundle block. Bundle age MAY be determined 1213 by subtracting the bundle's creation timestamp time from the current 1214 time if (a) that timestamp time is not zero and (b) the local node's 1215 clock is known to be accurate (as discussed in section 4.5.1 above); 1216 otherwise bundle age MUST be obtained from the Bundle Age extension 1217 block. Bundle expiration MAY occur at any point in the processing 1218 of a bundle. When a bundle expires, the bundle protocol agent MUST 1219 delete the bundle for the reason "lifetime expired": the bundle 1220 deletion procedure defined in Section 5.14 MUST be followed. 1222 5.6. Bundle Reception 1224 The steps in processing a bundle that has been received from another 1225 node are: 1227 Step 1: The retention constraint "Dispatch pending" MUST be added to 1228 the bundle. 1230 Step 2: If the "request reporting of bundle reception" flag in the 1231 bundle's status report request field is set to 1, and status 1232 reporting is enabled, then a bundle reception status report with 1233 reason code "No additional information" SHOULD be generated, 1234 destined for the bundle's report-to endpoint ID. 1236 Step 3: For each block in the bundle that is an extension block that 1237 the bundle protocol agent cannot process: 1239 . If the block processing flags in that block indicate that a 1240 status report is requested in this event, and status reporting 1241 is enabled, then a bundle reception status report with reason 1242 code "Block unintelligible" SHOULD be generated, destined for 1243 the bundle's report-to endpoint ID. 1244 . If the block processing flags in that block indicate that the 1245 bundle must be deleted in this event, then the bundle protocol 1246 agent MUST delete the bundle for the reason "Block 1247 unintelligible"; the bundle deletion procedure defined in 1248 Section 5.14 MUST be followed and all remaining steps of the 1249 bundle reception procedure MUST be skipped. 1250 . If the block processing flags in that block do NOT indicate 1251 that the bundle must be deleted in this event but do indicate 1252 that the block must be discarded, then the bundle protocol 1253 agent MUST remove this block from the bundle. 1254 . If the block processing flags in that block indicate neither 1255 that the bundle must be deleted nor that that the block must be 1256 discarded, then processing continues with the next extension 1257 block that the bundle protocol agent cannot process, if any; 1258 otherwise, processing proceeds from step 4. 1260 Step 4: Processing proceeds from Step 1 of Section 5.3. 1262 5.7. Local Bundle Delivery 1264 The steps in processing a bundle that is destined for an endpoint of 1265 which this node is a member are: 1267 Step 1: If the received bundle is a fragment, the application data 1268 unit reassembly procedure described in Section 5.9 MUST be followed. 1270 If this procedure results in reassembly of the entire original 1271 application data unit, processing of this bundle (whose fragmentary 1272 payload has been replaced by the reassembled application data unit) 1273 proceeds from Step 2; otherwise, the retention constraint 1274 "Reassembly pending" MUST be added to the bundle and all remaining 1275 steps of this procedure MUST be skipped. 1277 Step 2: Delivery depends on the state of the registration whose 1278 endpoint ID matches that of the destination of the bundle: 1280 . An additional implementation-specific delivery deferral 1281 procedure MAY optionally be associated with the registration. 1282 . If the registration is in the Active state, then the bundle 1283 MUST be delivered automatically as soon as it is the next 1284 bundle that is due for delivery according to the BPA's bundle 1285 delivery scheduling policy, an implementation matter. 1286 . If the registration is in the Passive state, or if delivery of 1287 the bundle fails for some implementation-specific reason, then 1288 the registration's delivery failure action MUST be taken. 1289 Delivery failure action MUST be one of the following: 1291 o defer delivery of the bundle subject to this registration 1292 until (a) this bundle is the least recently received of 1293 all bundles currently deliverable subject to this 1294 registration and (b) either the registration is polled or 1295 else the registration is in the Active state, and also 1296 perform any additional delivery deferral procedure 1297 associated with the registration; or 1299 o abandon delivery of the bundle subject to this registration 1300 (as defined in 3.1. ). 1302 Step 3: As soon as the bundle has been delivered, if the "request 1303 reporting of bundle delivery" flag in the bundle's status report 1304 request field is set to 1 and bundle status reporting is enabled, 1305 then a bundle delivery status report SHOULD be generated, destined 1306 for the bundle's report-to endpoint ID. Note that this status report 1307 only states that the payload has been delivered to the application 1308 agent, not that the application agent has processed that payload. 1310 5.8. Bundle Fragmentation 1312 It may at times be advantageous for bundle protocol agents to reduce 1313 the sizes of bundles in order to forward them. This might be the 1314 case, for example, if a node to which a bundle is to be forwarded is 1315 accessible only via intermittent contacts and no upcoming contact is 1316 long enough to enable the forwarding of the entire bundle. 1318 The size of a bundle can be reduced by "fragmenting" the bundle. To 1319 fragment a bundle whose payload is of size M is to replace it with 1320 two "fragments" -- new bundles with the same source node ID and 1321 creation timestamp as the original bundle -- whose payloads are the 1322 first N and the last (M - N) bytes of the original bundle's payload, 1323 where 0 < N < M. Note that fragments may themselves be fragmented, 1324 so fragmentation may in effect replace the original bundle with more 1325 than two fragments. (However, there is only one 'level' of 1326 fragmentation, as in IP fragmentation.) 1328 Any bundle whose primary block's bundle processing flags do NOT 1329 indicate that it must not be fragmented MAY be fragmented at any 1330 time, for any purpose, at the discretion of the bundle protocol 1331 agent. NOTE, however, that some combinations of bundle 1332 fragmentation, replication, and routing might result in unexpected 1333 traffic patterns. 1335 Fragmentation SHALL be constrained as follows: 1337 . The concatenation of the payloads of all fragments produced by 1338 fragmentation MUST always be identical to the payload of the 1339 fragmented bundle (that is, the bundle that is being 1340 fragmented). Note that the payloads of fragments resulting from 1341 different fragmentation episodes, in different parts of the 1342 network, may be overlapping subsets of the fragmented bundle's 1343 payload. 1344 . The primary block of each fragment MUST differ from that of the 1345 fragmented bundle, in that the bundle processing flags of the 1346 fragment MUST indicate that the bundle is a fragment and both 1347 fragment offset and total application data unit length must be 1348 provided. Additionally, the CRC of the primary block of the 1349 fragmented bundle, if any, MUST be replaced in each fragment by 1350 a new CRC computed for the primary block of that fragment. 1351 . The payload blocks of fragments will differ from that of the 1352 fragmented bundle as noted above. 1353 . If the fragmented bundle is not a fragment or is the fragment 1354 with offset zero, then all extension blocks of the fragmented 1355 bundle MUST be replicated in the fragment whose offset is zero. 1356 . Each of the fragmented bundle's extension blocks whose "Block 1357 must be replicated in every fragment" flag is set to 1 MUST be 1358 replicated in every fragment. 1359 . Beyond these rules, replication of extension blocks in the 1360 fragments is an implementation matter. 1362 5.9. Application Data Unit Reassembly 1364 If the concatenation -- as informed by fragment offsets and payload 1365 lengths -- of the payloads of all previously received fragments with 1366 the same source node ID and creation timestamp as this fragment, 1367 together with the payload of this fragment, forms a byte array whose 1368 length is equal to the total application data unit length in the 1369 fragment's primary block, then: 1371 . This byte array -- the reassembled application data unit -- 1372 MUST replace the payload of this fragment. 1373 . The "Reassembly pending" retention constraint MUST be removed 1374 from every other fragment whose payload is a subset of the 1375 reassembled application data unit. 1377 Note: reassembly of application data units from fragments occurs at 1378 the nodes that are members of destination endpoints as necessary; an 1379 application data unit MAY also be reassembled at some other node on 1380 the path to the destination. 1382 5.10. Bundle Deletion 1384 The steps in deleting a bundle are: 1386 Step 1: If the "request reporting of bundle deletion" flag in the 1387 bundle's status report request field is set to 1, and if status 1388 reporting is enabled, then a bundle deletion status report citing 1389 the reason for deletion SHOULD be generated, destined for the 1390 bundle's report-to endpoint ID. 1392 Step 2: All of the bundle's retention constraints MUST be removed. 1394 5.11. Discarding a Bundle 1396 As soon as a bundle has no remaining retention constraints it MAY be 1397 discarded, thereby releasing any persistent storage that may have 1398 been allocated to it. 1400 5.12. Canceling a Transmission 1402 When requested to cancel a specified transmission, where the bundle 1403 created upon initiation of the indicated transmission has not yet 1404 been discarded, the bundle protocol agent MUST delete that bundle 1405 for the reason "transmission cancelled". For this purpose, the 1406 procedure defined in Section 5.14 MUST be followed. 1408 6. Administrative Record Processing 1410 6.1. Administrative Records 1412 Administrative records are standard application data units that are 1413 used in providing some of the features of the Bundle Protocol. One 1414 type of administrative record has been defined to date: bundle 1415 status reports. Note that additional types of administrative 1416 records may be defined by supplementary DTN protocol specification 1417 documents. 1419 Every administrative record consists of: 1421 . Record type code (an unsigned integer for which valid values 1422 are as defined below). 1423 . Record content in type-specific format. 1425 Valid administrative record type codes are defined as follows: 1427 +---------+--------------------------------------------+ 1429 | Value | Meaning | 1431 +=========+============================================+ 1433 | 1 | Bundle status report. | 1435 +---------+--------------------------------------------+ 1437 | (other) | Reserved for future use. | 1439 +---------+--------------------------------------------+ 1441 Figure 3: Administrative Record Type Codes 1443 Each BP administrative record SHALL be represented as a CBOR array 1444 comprising a 2-tuple. 1446 The first item of the array SHALL be a record type code, which SHALL 1447 be represented as a CBOR unsigned integer. 1449 The second element of this array SHALL be the applicable CBOR 1450 representation of the content of the record. Details of the CBOR 1451 representation of administrative record type 1 are provided below. 1452 Details of the CBOR representation of other types of administrative 1453 record type are included in the specifications defining those 1454 records. 1456 6.1.1. Bundle Status Reports 1458 The transmission of "bundle status reports" under specified 1459 conditions is an option that can be invoked when transmission of a 1460 bundle is requested. These reports are intended to provide 1461 information about how bundles are progressing through the system, 1462 including notices of receipt, forwarding, final delivery, and 1463 deletion. They are transmitted to the Report-to endpoints of 1464 bundles. 1466 Each bundle status report SHALL be represented as a CBOR array. The 1467 number of elements in the array SHALL be either 6 (if the subject 1468 bundle is a fragment) or 4 (otherwise). 1470 The first item of the bundle status report array SHALL be bundle 1471 status information represented as a CBOR array of at least 4 1472 elements. The first four items of the bundle status information 1473 array shall provide information on the following four status 1474 assertions, in this order: 1476 . Reporting node received bundle. 1477 . Reporting node forwarded the bundle. 1478 . Reporting node delivered the bundle. 1479 . Reporting node deleted the bundle. 1481 Each item of the bundle status information array SHALL be a bundle 1482 status item represented as a CBOR array; the number of elements in 1483 each such array SHALL be either 2 (if the value of the first item of 1484 this bundle status item is 1 AND the "Report status time" flag was 1485 set to 1 in the bundle processing flags of the bundle whose status 1486 is being reported) or 1 (otherwise). The first item of the bundle 1487 status item array SHALL be a status indicator, a Boolean value 1488 indicating whether or not the corresponding bundle status is 1489 asserted, represented as a CBOR Boolean value. The second item of 1490 the bundle status item array, if present, SHALL indicate the time 1491 (as reported by the local system clock, an implementation matter) at 1492 which the indicated status was asserted for this bundle, represented 1493 as a DTN time as described in Section 4.1.6. above. 1495 The second item of the bundle status report array SHALL be the 1496 bundle status report reason code explaining the value of the status 1497 indicator, represented as a CBOR unsigned integer. Valid status 1498 report reason codes are defined in Figure 4 below but the list of 1499 status report reason codes provided here is neither exhaustive nor 1500 exclusive; supplementary DTN protocol specifications (including, but 1501 not restricted to, the Bundle Security Protocol [BPSEC]) may define 1502 additional reason codes. 1504 +---------+--------------------------------------------+ 1506 | Value | Meaning | 1508 +=========+============================================+ 1510 | 0 | No additional information. | 1512 +---------+--------------------------------------------+ 1514 | 1 | Lifetime expired. | 1516 +---------+--------------------------------------------+ 1518 | 2 | Forwarded over unidirectional link. | 1520 +---------+--------------------------------------------+ 1522 | 3 | Transmission canceled. | 1524 +---------+--------------------------------------------+ 1526 | 4 | Depleted storage. | 1528 +---------+--------------------------------------------+ 1530 | 5 | Destination endpoint ID unintelligible. | 1532 +---------+--------------------------------------------+ 1534 | 6 | No known route to destination from here. | 1536 +---------+--------------------------------------------+ 1538 | 7 | No timely contact with next node on route. | 1540 +---------+--------------------------------------------+ 1542 | 8 | Block unintelligible. | 1544 +---------+--------------------------------------------+ 1546 | 9 | Hop limit exceeded. | 1548 +---------+--------------------------------------------+ 1550 | (other) | Reserved for future use. | 1551 +---------+--------------------------------------------+ 1553 Figure 4: Status Report Reason Codes 1555 The third item of the bundle status report array SHALL be the source 1556 node ID identifying the source of the bundle whose status is being 1557 reported, represented as described in Section 4.1.5.2. above. 1559 The fourth item of the bundle status report array SHALL be the 1560 creation timestamp of the bundle whose status is being reported, 1561 represented as described in Section 4.1.7. above. 1563 The fifth item of the bundle status report array SHALL be present if 1564 and only if the bundle whose status is being reported contained a 1565 fragment offset. If present, it SHALL be the subject bundle's 1566 fragment offset represented as a CBOR unsigned integer item. 1568 The sixth item of the bundle status report array SHALL be present if 1569 and only if the bundle whose status is being reported contained a 1570 fragment offset. If present, it SHALL be the length of the subject 1571 bundle's payload represented as a CBOR unsigned integer item. 1573 6.2. Generation of Administrative Records 1575 Whenever the application agent's administrative element is directed 1576 by the bundle protocol agent to generate an administrative record 1577 with reference to some bundle, the following procedure must be 1578 followed: 1580 Step 1: The administrative record must be constructed. If the 1581 administrative record references a bundle and the referenced bundle 1582 is a fragment, the administrative record MUST contain the fragment 1583 offset and fragment length. 1585 Step 2: A request for transmission of a bundle whose payload is this 1586 administrative record MUST be presented to the bundle protocol 1587 agent. 1589 7. Services Required of the Convergence Layer 1591 7.1. The Convergence Layer 1593 The successful operation of the end-to-end bundle protocol depends 1594 on the operation of underlying protocols at what is termed the 1595 "convergence layer"; these protocols accomplish communication 1596 between nodes. A wide variety of protocols may serve this purpose, 1597 so long as each convergence layer protocol adapter provides a 1598 defined minimal set of services to the bundle protocol agent. This 1599 convergence layer service specification enumerates those services. 1601 7.2. Summary of Convergence Layer Services 1603 Each convergence layer protocol adapter is expected to provide the 1604 following services to the bundle protocol agent: 1606 . sending a bundle to a bundle node that is reachable via the 1607 convergence layer protocol; 1608 . delivering to the bundle protocol agent a bundle that was sent 1609 by a bundle node via the convergence layer protocol. 1611 The convergence layer service interface specified here is neither 1612 exhaustive nor exclusive. That is, supplementary DTN protocol 1613 specifications (including, but not restricted to, the Bundle 1614 Security Protocol [BPSEC]) may expect convergence layer adapters 1615 that serve BP implementations conforming to those protocols to 1616 provide additional services such as reporting on the transmission 1617 and/or reception progress of individual bundles (at completion 1618 and/or incrementally), retransmitting data that were lost in 1619 transit, discarding bundle-conveying data units that the convergence 1620 layer protocol determines are corrupt or inauthentic, or reporting 1621 on the integrity and/or authenticity of delivered bundles. 1623 8. Implementation Status 1625 [NOTE to the RFC Editor: please remove this section before 1626 publication, as well as the reference to RFC 7942.] 1628 This section records the status of known implementations of the 1629 protocol defined by this specification at the time of posting of 1630 this Internet-Draft, and is based on a proposal described in RFC 1631 7942. The description of implementations in this section is 1632 intended to assist the IETF in its decision processes in progressing 1633 drafts to RFCs. Please note that the listing of any individual 1634 implementation here does not imply endorsement by the IETF. 1635 Furthermore, no effort has been spent to verify the information 1636 presented here that was supplied by IETF contributors. This is not 1637 intended as, and must not be construed to be, a catalog of available 1638 implementations or their features. Readers are advised to note that 1639 other implementations may exist. 1641 According to RFC 7942, "this will allow reviewers and working groups 1642 to assign due consideration to documents that have the benefit of 1643 running code, which may serve as evidence of valuable 1644 experimentation and feedback that have made the implemented 1645 protocols more mature. It is up to the individual working groups to 1646 use this information as they see fit". 1648 At the time of this writing, the only known implementation of the 1649 current document is microPCN (https://upcn.eu/). According to the 1650 developers: 1652 The Micro Planetary Communication Network (uPCN) is a free 1653 software project intended to offer an implementation of Delay- 1654 tolerant Networking protocols for POSIX operating systems (well, 1655 and for Linux) plus for the ARM Cortex STM32F4 microcontroller 1656 series. More precisely it currently provides an implementation of 1658 . the Bundle Protocol (BP, RFC 5050), 1659 . the Bundle Protocol version 7 specification draft (version 6), 1660 . the DTN IP Neighbor Discovery (IPND) protocol, and 1661 . a routing approach optimized for message-ferry micro LEO 1662 satellites. 1664 uPCN is written in C and is built upon the real-time operating 1665 system FreeRTOS. The source code of uPCN is released under the 1666 "BSD 3-Clause License". 1668 The project depends on an execution environment offering link 1669 layer protocols such as AX.25. The source code uses the USB 1670 subsystem to interact with the environment. 1672 9. Security Considerations 1674 The bundle protocol security architecture and the available security 1675 services are specified in an accompanying document, the Bundle 1676 Security Protocol specification [BPSEC]. 1678 The bpsec extensions to Bundle Protocol enable each block of a 1679 bundle (other than a bpsec extension block) to be individually 1680 authenticated by a signature block (Block Integrity Block, or BIB) 1681 and also enable each block of a bundle other than the primary block 1682 (and the bpsec extension blocks themselves) to be individually 1683 encrypted by a BCB. 1685 Because the security mechanisms are extension blocks that are 1686 themselves inserted into the bundle, the integrity and 1687 confidentiality of bundle blocks are protected while the bundle is 1688 at rest, awaiting transmission at the next forwarding opportunity, 1689 as well as in transit. 1691 Additionally, convergence-layer protocols that ensure authenticity 1692 of communication between adjacent nodes in BP network topology 1693 SHOULD be used where available, to minimize the ability of 1694 unauthenticated nodes to introduce inauthentic traffic into the 1695 network. 1697 Note that, while the primary block must remain in the clear for 1698 routing purposes, the Bundle Protocol can be protected against 1699 traffic analysis to some extent by using bundle-in-bundle 1700 encapsulation to tunnel bundles to a safe forward distribution 1701 point: the encapsulated bundle forms the payload of an encapsulating 1702 bundle, and that payload block may be encrypted by a BCB. 1704 Note that the generation of bundle status reports is disabled by 1705 default because malicious initiation of bundle status reporting 1706 could result in the transmission of extremely large numbers of 1707 bundle, effecting a denial of service attack. 1709 The bpsec extensions accommodate an open-ended range of 1710 ciphersuites; different ciphersuites may be utilized to protect 1711 different blocks. One possible variation is to sign and/or encrypt 1712 blocks in symmetric keys securely formed by Diffie-Hellman 1713 procedures (such as EKDH) using the public and private keys of the 1714 sending and receiving nodes. For this purpose, the key distribution 1715 problem reduces to the problem of trustworthy delay-tolerant 1716 distribution of public keys, a current research topic. 1718 Bundle security MUST NOT be invalidated by forwarding nodes even 1719 though they themselves might not use the Bundle Security Protocol. 1721 In particular, while blocks MAY be added to bundles transiting 1722 intermediate nodes, removal of blocks with the "Discard block if it 1723 can't be processed" flag set in the block processing control flags 1724 may cause security to fail. 1726 Inclusion of the Bundle Security Protocol in any Bundle Protocol 1727 implementation is RECOMMENDED. Use of the Bundle Security Protocol 1728 in Bundle Protocol operations is OPTIONAL, subject to the following 1729 guidelines: 1731 . Every block (that is not a bpsec extension block) of every 1732 bundle SHOULD be authenticated by a BIB citing the ID of the 1733 node that inserted that block. (Note that a single BIB may 1734 authenticate multiple "target" blocks.) BIB authentication MAY 1735 be omitted on (and only on) any initial end-to-end path 1736 segments on which it would impose unacceptable overhead, 1737 provided that satisfactory authentication is ensured at the 1738 convergence layer and that BIB authentication is asserted on 1739 the first path segment on which the resulting overhead is 1740 acceptable and on all subsequent path segments. 1741 . If any segment of the end-to-end path of a bundle will traverse 1742 the Internet or any other potentially insecure communication 1743 environment, then the payload block SHOULD be encrypted by a 1744 BCB on this path segment and all subsequent segments of the 1745 end-to-end path. 1747 10. IANA Considerations 1749 This document defines the following additional Bundle Protocol block 1750 types, for which values are to be assigned from the Bundle 1751 Administrative Record Types namespace [RFC6255]: 1753 Value Name Meaning Reference 1755 ----- ------------- ----------------------------- ---------- 1757 7 Previous node Identifies sender This document 1759 8 Bundle age Bundle age in seconds This document 1761 9 Hop count #prior transmission attempts This document 1763 This document also defines a new URI scheme type field - an unsigned 1764 integer of undefined length - for which IANA is to create and 1765 maintain a new registry named "URI scheme type values". Initial 1766 values for the Bundle Protocol URI scheme type registry are given 1767 below; future assignments are to be made through Expert Review. 1768 Each assignment consists of a URI scheme type name and its 1769 associated value. 1771 Value URI Scheme Type Name Reference 1773 ----- ------------------------ ------------------------------- 1775 0 Reserved 1777 1 dtn RFC5050, Section 4.4 1779 2 ipn RFC6260, Section 4 1781 3-254 Unassigned 1783 255 Reserved 1785 --------------------------------------------------------------- 1787 11. References 1789 11.1. Normative References 1791 [CRC] International Telecommunication Union, "Error-correcting 1792 procedures for DCEs using asynchronous-to-synchronous conversion", 1793 ITU-T Recommendation V.42, March 2002. 1795 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1796 Requirement Levels", BCP 14, RFC 2119, March 1997. 1798 [RFC7049] Borman, C. and P. Hoffman, "Concise Binary Object 1799 Representation (CBOR)", RFC 7049, October 2013. 1801 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1802 Resource Identifier (URI): Generic Syntax", RFC 3986, STD 66, 1803 January 2005. 1805 [URIREG] Thaler, D., Hansen, T., and T. Hardie, "Guidelines and 1806 Registration Procedures for URI Schemes", RFC 7595, BCP 35, June 1807 2015. 1809 11.2. Informative References 1811 [ARCH] V. Cerf et al., "Delay-Tolerant Network Architecture", RFC 1812 4838, April 2007. 1814 [BPSEC] Birrane, E., "Bundle Security Protocol Specification", Work 1815 In Progress, October 2015. 1817 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1818 Identifiers (IRIs)", RFC 3987, January 2005. 1820 [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol 1821 IANA Registries", RFC 6255, May 2011. 1823 [SIGC] Fall, K., "A Delay-Tolerant Network Architecture for 1824 Challenged Internets", SIGCOMM 2003. 1826 [UTC] Arias, E. and B. Guinot, "Coordinated universal time UTC: 1827 historical background and perspectives" in "Journees systemes de 1828 reference spatio-temporels", 2004. 1830 12. Acknowledgments 1832 This work is freely adapted from RFC 5050, which was an effort of 1833 the Delay Tolerant Networking Research Group. The following DTNRG 1834 participants contributed significant technical material and/or 1835 inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh, 1836 Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory, 1837 Michael Demmer of the University of California at Berkeley, Robert 1838 Durst, Keith Scott, and Susan Symington of The MITRE Corporation, 1839 Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity 1840 College Dublin, Peter Lovell of SPARTA, Inc., Manikantan Ramadas of 1841 Ohio University, and Howard Weiss of SPARTA, Inc. 1843 This document was prepared using 2-Word-v2.0.template.dot. 1845 13. Significant Changes from RFC 5050 1847 Points on which this draft significantly differs from RFC 5050 1848 include the following: 1850 . Clarify the difference between transmission and forwarding. 1851 . Migrate custody transfer to the bundle-in-bundle encapsulation 1852 specification. 1853 . Introduce the concept of "node ID" as functionally distinct 1854 from endpoint ID, while having the same syntax. 1855 . Restructure primary block, making it immutable. Add optional 1856 CRC. 1857 . Add optional CRCs to non-primary blocks. 1858 . Add block ID number to canonical block format (to support 1859 streamlined BSP). 1860 . Add bundle age extension block, defined in this specification. 1861 . Add previous node extension block, defined in this 1862 specification. 1863 . Add flow label extension block, *not* defined in this 1864 specification. 1865 . Add manifest extension block, *not* defined in this 1866 specification. 1867 . Add hop count extension block, defined in this specification. 1868 . Migrate Quality of Service markings to a new QoS extension 1869 block, *not* defined in this specification. 1871 Appendix A. For More Information 1873 Please refer comments to dtn@ietf.org. The Delay Tolerant Networking 1874 Research Group (DTNRG) Web site is located at http://www.dtnrg.org. 1876 Copyright (c) 2017 IETF Trust and the persons identified as authors 1877 of the code. All rights reserved. 1879 Redistribution and use in source and binary forms, with or without 1880 modification, is permitted pursuant to, and subject to the license 1881 terms contained in, the Simplified BSD License set forth in Section 1882 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 1883 (http://trustee.ietf.org/license-info). 1885 Appendix B. CDDL expression 1887 For informational purposes, Carsten Bormann has kindly provided an 1888 expression of the Bundle Protocol specification in the Concise Data 1889 Definition Language (CDDL). That CDDL expression is presented 1890 below, somewhat edited by the authors. Note that wherever the CDDL 1891 expression is in disagreement with the textual representation of the 1892 BP specification presented in the earlier sections of this document, 1893 the textual representation rules. 1895 start = bundle 1897 dtn-time = uint 1899 creation-timestamp = [dtn-time, sequence: uint] 1901 eid-generic = [uri-code, SSP: any] 1903 uri-code = uint 1905 eid = eid-choice .within eid-generic 1907 eid-choice /= [dtn-code, SSP: (text / 0)] 1909 dtn-code = 1 ; TBD 1911 eid-choice /= [ipn-code, SSP: [nodenum: uint, servicenum: uint]] 1913 ipn-code = 2 ; TBD 1915 bundle-control-flags = uint .bits bundleflagbits 1917 bundleflagbits = &( 1919 reserved: 15 1921 reserved: 14 1923 reserved: 13 1925 bundle-deletion-status-reports-are-requested: 12 1927 bundle-delivery-status-reports-are-requested: 11 1929 bundle-forwarding-status-reports-are-requested: 10 1931 reserved: 9 1932 bundle-reception-status-reports-are-requested: 8 1934 bundle-contains-a-Manifest-block: 7 1936 status-time-is-requested-in-all-status-reports: 6 1938 user-application-acknowledgement-is-requested: 5 1940 destination-is-a-singleton-endpoint: 4 1942 reserved: 3 1944 bundle-must-not-be-fragmented: 2 1946 payload-is-an-administrative-record: 1 1948 bundle-is-a-fragment: 0 1950 ) 1952 crc = bytes 1954 block-control-flags = uint .bits blockflagbits 1956 blockflagbits = &( 1958 reserved: 7 1960 reserved: 6 1962 reserved: 5 1964 reserved: 4 1966 bundle-must-be-deleted-if-block-cannot-be-processed: 3 1968 status-report-must-be-transmitted-if-block-cannot-be-processed: 2 1970 block-must-be-removed-from-bundle-if-it-cannot-be-processed: 1 1972 block-must-be-replicated-in-every-fragment: 0 1974 ) 1976 bundle = [primary-block, *extension-block, payload-block] 1978 primary-block = [ 1979 version: 7, 1981 bundle-control-flags, 1983 crc-type: uint, 1985 destination: eid, 1987 source-node: eid, 1989 report-to: eid, 1991 creation-timestamp, 1993 lifetime: uint, 1995 ? fragment-offset: uint, 1997 ? total-application-data-length: uint, 1999 ? crc, 2001 ] 2003 canonical-block-generic = [ 2005 block-type-code: uint, 2007 canonical-block-common, 2009 content: any, 2011 ? crc 2013 ] 2015 canonical-block-common = ( 2017 block-number: uint, 2019 block-control-flags, 2021 crc-type: uint, 2023 block-data-length: uint 2025 ) 2026 canonical-block = canonical-block-choice .within canonical-block- 2027 generic 2029 canonical-block-choice /= payload-block 2031 payload-block = [1, canonical-block-common, adu-extent: payload] 2033 payload = bytes / bytes .cbor admin-record 2035 canonical-block-choice /= extension-block 2037 extension-block = extension-block-choice .within canonical-block 2039 extension-block-choice /= previous-node-block 2041 previous-node-block = [7, canonical-block-common, eid] 2043 extension-block-choice /= bundle-age-block 2045 bundle-age-block = [8, canonical-block-common, bundle-age: uint] 2047 extension-block-choice /= hop-count-block 2049 hop-count-block = [9, canonical-block-common, 2051 [hop-limit: uint, 2053 hop-count: uint] 2055 ] 2057 admin-record-generic = [record-type: uint, any] 2059 admin-record = admin-record-choice .within admin-record-generic 2061 admin-record-choice /= bundle-status-report 2063 bundle-status-report = [1, [bundle-status-information, 2065 bundle-status-reason: uint, 2067 admin-common] 2069 ] 2070 admin-common = ( 2072 source-node: eid, 2074 creation-timestamp, 2076 ? fragment-offset: uint, 2078 ? payload-length: uint 2080 ) 2082 bundle-status-information = [ 2084 reporting-node-received-bundle: bundle-status-item, 2086 reporting-node-forwarded-the-bundle: bundle-status-item, 2088 reporting-node-delivered-the-bundle: bundle-status-item, 2090 reporting-node-deleted-the-bundle: bundle-status-item, 2092 ] 2094 bundle-status-item = [ 2096 asserted: bool, 2098 ? time-of-assertion: dtn-time 2100 ] 2102 Authors' Addresses 2104 Scott Burleigh 2105 Jet Propulsion Laboratory, California Institute of Technology 2106 4800 Oak Grove Dr. 2107 Pasadena, CA 91109-8099 2108 US 2109 Phone: +1 818 393 3353 2110 Email: Scott.Burleigh@jpl.nasa.gov 2111 Kevin Fall 2112 Nefeli Networks, Inc. 2113 2150 Shattuck Ave. 2114 Berkeley, CA 94704 2115 US 2116 Email: kfall@kfall.com 2118 Edward J. Birrane 2119 Johns Hopkins University Applied Physics Laboratory 2120 11100 Johns Hopkins Rd 2121 Laurel, MD 20723 2122 US 2123 Phone: +1 443 778 7423 2124 Email: Edward.Birrane@jhuapl.edu