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Is this intentional? 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. 'CRC16' ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) -- Possible downref: Non-RFC (?) normative reference: ref. 'SABR' Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 3 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: June 13, 2021 Roland Computing Services 5 E. Birrane 6 APL, Johns Hopkins University 7 December 10, 2020 9 Bundle Protocol Version 7 10 draft-ietf-dtn-bpbis-30.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 June 13, 2021. 35 Copyright Notice 37 Copyright (c) 2020 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 the Bundle 53 Protocol, adapted from the experimental Bundle Protocol 54 specification developed by the Delay-Tolerant Networking Research 55 group of the Internet Research Task Force and documented in RFC 56 5050. 58 Table of Contents 60 1. Introduction...................................................3 61 2. Conventions used in this document..............................5 62 3. Service Description............................................5 63 3.1. Definitions...............................................5 64 3.2. Discussion of BP concepts.................................9 65 3.3. Services Offered by Bundle Protocol Agents...............12 66 4. Bundle Format.................................................13 67 4.1. Bundle Structure.........................................13 68 4.2. BP Fundamental Data Structures...........................14 69 4.2.1. CRC Type............................................14 70 4.2.2. CRC.................................................14 71 4.2.3. Bundle Processing Control Flags.....................15 72 4.2.4. Block Processing Control Flags......................16 73 4.2.5. Identifiers.........................................17 74 4.2.5.1. Endpoint ID....................................17 75 4.2.5.1.1. The "dtn" URI scheme......................18 76 4.2.5.1.2. The "ipn" URI scheme......................20 77 4.2.5.2. Node ID........................................22 78 4.2.6. DTN Time............................................22 79 4.2.7. Creation Timestamp..................................22 80 4.2.8. Block-type-specific Data............................23 81 4.3. Block Structures.........................................23 82 4.3.1. Primary Bundle Block................................23 83 4.3.2. Canonical Bundle Block Format.......................26 84 4.4. Extension Blocks.........................................27 85 4.4.1. Previous Node.......................................27 86 4.4.2. Bundle Age..........................................28 87 4.4.3. Hop Count...........................................28 88 5. Bundle Processing.............................................29 89 5.1. Generation of Administrative Records.....................29 90 5.2. Bundle Transmission......................................30 91 5.3. Bundle Dispatching.......................................30 92 5.4. Bundle Forwarding........................................30 93 5.4.1. Forwarding Contraindicated..........................33 94 5.4.2. Forwarding Failed...................................33 95 5.5. Bundle Expiration........................................33 96 5.6. Bundle Reception.........................................34 97 5.7. Local Bundle Delivery....................................35 98 5.8. Bundle Fragmentation.....................................36 99 5.9. Application Data Unit Reassembly.........................37 100 5.10. Bundle Deletion.........................................38 101 5.11. Discarding a Bundle.....................................38 102 5.12. Canceling a Transmission................................38 103 6. Administrative Record Processing..............................38 104 6.1. Administrative Records...................................38 105 6.1.1. Bundle Status Reports...............................39 106 6.2. Generation of Administrative Records.....................42 107 7. Services Required of the Convergence Layer....................42 108 7.1. The Convergence Layer....................................42 109 7.2. Summary of Convergence Layer Services....................43 110 8. Implementation Status.........................................43 111 9. Security Considerations.......................................45 112 10. IANA Considerations..........................................47 113 10.1. Bundle Block Types......................................47 114 10.2. Primary Bundle Protocol Version.........................48 115 10.3. Bundle Processing Control Flags.........................48 116 10.4. Block Processing Control Flags..........................50 117 10.5. Bundle Status Report Reason Codes.......................51 118 10.6. Bundle Protocol URI scheme types........................53 119 10.7. URI scheme "dtn"........................................54 120 10.8. URI scheme "ipn"........................................55 121 11. References...................................................55 122 11.1. Normative References....................................55 123 11.2. Informative References..................................56 124 12. Acknowledgments..............................................57 125 13. Significant Changes from RFC 5050............................57 126 Appendix A. For More Information.................................59 127 Appendix B. CDDL expression......................................60 129 1. Introduction 131 Since the publication of the Bundle Protocol Specification 132 (Experimental RFC 5050 [RFC5050]) in 2007, the Delay-Tolerant 133 Networking (DTN) Bundle Protocol has been implemented in multiple 134 programming languages and deployed to a wide variety of computing 135 platforms. This implementation and deployment experience has 136 identified opportunities for making the protocol simpler, more 137 capable, and easier to use. The present document, standardizing the 138 Bundle Protocol (BP), is adapted from RFC 5050 in that context, 139 reflecting lessons learned. Significant changes from the Bundle 140 Protocol specification defined in RFC 5050 are listed in section 13. 142 This document describes version 7 of BP. 144 Delay Tolerant Networking is a network architecture providing 145 communications in and/or through highly stressed environments. 146 Stressed networking environments include those with intermittent 147 connectivity, large and/or variable delays, and high bit error 148 rates. To provide its services, BP may be viewed as sitting at the 149 application layer of some number of constituent networks, forming a 150 store-carry-forward overlay network. Key capabilities of BP 151 include: 153 . Ability to use physical motility for the movement of data 154 . Ability to move the responsibility for error control from one 155 node to another 156 . Ability to cope with intermittent connectivity, including cases 157 where the sender and receiver are not concurrently present in 158 the network 159 . Ability to take advantage of scheduled, predicted, and 160 opportunistic connectivity, whether bidirectional or 161 unidirectional, in addition to continuous connectivity 162 . Late binding of overlay network endpoint identifiers to 163 underlying constituent network addresses 165 For descriptions of these capabilities and the rationale for the DTN 166 architecture, see [ARCH] and [SIGC]. 168 BP's location within the standard protocol stack is as shown in 169 Figure 1. BP uses underlying "native" transport and/or network 170 protocols for communications within a given constituent network. 171 The layer at which those underlying protocols are located is here 172 termed the "convergence layer" and the interface between the bundle 173 protocol and a specific underlying protocol is termed a "convergence 174 layer adapter". 176 Figure 1 shows three distinct transport and network protocols 177 (denoted T1/N1, T2/N2, and T3/N3). 179 +-----------+ +-----------+ 180 | BP app | | BP app | 181 +---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+ 182 | BP v | | ^ BP v | | ^ BP v | | ^ BP | 183 +---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+ 184 | T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 | 185 +---------v-+ +-^---------v-+ +-^---------v + +-^---------+ 186 | N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 | 187 +---------v-+ +-^---------v + +-^---------v-+ +-^---------+ 188 | >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ | 189 +-----------+ +-------------+ +-------------+ +-----------+ 190 | | | | 191 |<---- A network ---->| |<---- A network ---->| 192 | | | | 194 Figure 1: The Bundle Protocol in the Protocol Stack Model 196 This document describes the format of the protocol data units 197 (called "bundles") passed between entities participating in BP 198 communications. 200 The entities are referred to as "bundle nodes". This document does 201 not address: 203 . Operations in the convergence layer adapters that bundle nodes 204 use to transport data through specific types of internets. 205 (However, the document does discuss the services that must be 206 provided by each adapter at the convergence layer.) 207 . The bundle route computation algorithm. 208 . Mechanisms for populating the routing or forwarding information 209 bases of bundle nodes. 210 . The mechanisms for securing bundles en route. 211 . The mechanisms for managing bundle nodes. 213 Note that implementations of the specification presented in this 214 document will not be interoperable with implementations of RFC 5050. 216 2. Conventions used in this document 218 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 219 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 220 "OPTIONAL" in this document are to be interpreted as described in 221 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 222 capitals, as shown here. 224 3. Service Description 226 3.1. Definitions 228 Bundle - A bundle is a protocol data unit of BP, so named because 229 negotiation of the parameters of a data exchange may be impractical 230 in a delay-tolerant network: it is often better practice to "bundle" 231 with a unit of application data all metadata that might be needed in 232 order to make the data immediately usable when delivered to the 233 application. Each bundle comprises a sequence of two or more 234 "blocks" of protocol data, which serve various purposes. 236 Block - A bundle protocol block is one of the protocol data 237 structures that together constitute a well-formed bundle. 239 Application Data Unit (ADU) - An application data unit is the unit 240 of data whose conveyance to the bundle's destination is the purpose 241 for the transmission of some bundle that is not a fragment (as 242 defined below). 244 Bundle payload - A bundle payload (or simply "payload") is the 245 content of the bundle's payload block. The terms "bundle content", 246 "bundle payload", and "payload" are used interchangeably in this 247 document. For a bundle that is not a fragment (as defined below), 248 the payload is an application data unit. 250 Partial payload - A partial payload is a payload that comprises 251 either the first N bytes or the last N bytes of some other payload 252 of length M, such that 0 < N < M. Note that every partial payload 253 is a payload and therefore can be further subdivided into partial 254 payloads. 256 Fragment - A fragment, a.k.a. "fragmentary bundle", is a bundle 257 whose payload block contains a partial payload. 259 Bundle node - A bundle node (or, in the context of this document, 260 simply a "node") is any entity that can send and/or receive bundles. 261 Each bundle node has three conceptual components, defined below, as 262 shown in Figure 2: a "bundle protocol agent", a set of zero or more 263 "convergence layer adapters", and an "application agent". ("CL1 264 PDUs" are the PDUs of the convergence-layer protocol used in network 265 1.) 267 +-----------------------------------------------------------+ 268 |Node | 269 | | 270 | +-------------------------------------------------------+ | 271 | |Application Agent | | 272 | | | | 273 | | +--------------------------+ +----------------------+ | | 274 | | |Administrative element | |Application-specific | | | 275 | | | | |element | | | 276 | | | | | | | | 277 | | +--------------------------+ +----------------------+ | | 278 | | ^ ^ | | 279 | | Admin|records Application|data | | 280 | | | | | | 281 | +----------------v--------------------------v-----------+ | 282 | ^ | 283 | | ADUs | 284 | | | 285 | +-----------------------------v-------------------------+ | 286 | |Bundle Protocol Agent | | 287 | | | | 288 | | | | 289 | +-------------------------------------------------------+ | 290 | ^ ^ ^ | 291 | | Bundles | Bundles Bundles | | 292 | | | | | 293 | +------v-----+ +-----v------+ +-----v-----+ | 294 | |CLA 1 | |CLA 2 | |CLA n | | 295 | | | | | . . . | | | 296 | | | | | | | | 297 +-+------------+-----+------------+-----------+-----------+-+ 298 ^ ^ ^ 299 CL1|PDUs CL2|PDUs CLn|PDUs 300 | | | 301 +------v-----+ +-----v------+ +-----v-----+ 302 Network 1 Network 2 Network n 304 Figure 2: Components of a Bundle Node 306 Bundle protocol agent - The bundle protocol agent (BPA) of a node is 307 the node component that offers the BP services and executes the 308 procedures of the bundle protocol. 310 Convergence layer adapter - A convergence layer adapter (CLA) is a 311 node component that sends and receives bundles on behalf of the BPA, 312 utilizing the services of some 'native' protocol stack that is 313 supported in one of the networks within which the node is 314 functionally located. 316 Application agent - The application agent (AA) of a node is the node 317 component that utilizes the BP services to effect communication for 318 some user purpose. The application agent in turn has two elements, 319 an administrative element and an application-specific element. 321 Application-specific element - The application-specific element of 322 an AA is the node component that constructs, requests transmission 323 of, accepts delivery of, and processes units of user application 324 data. 326 Administrative element - The administrative element of an AA is the 327 node component that constructs and requests transmission of 328 administrative records (defined below), including status reports, 329 and accepts delivery of and processes any administrative records 330 that the node receives. 332 Administrative record - A BP administrative record is an application 333 data unit that is exchanged between the administrative elements of 334 nodes' application agents for some BP administrative purpose. The 335 only administrative record defined in this specification is the 336 status report, discussed later. 338 Bundle endpoint - A bundle endpoint (or simply "endpoint") is a set 339 of zero or more bundle nodes that all identify themselves for BP 340 purposes by some common identifier, called a "bundle endpoint ID" 341 (or, in this document, simply "endpoint ID"; endpoint IDs are 342 described in detail in Section 4.5.5.1 below. 344 Singleton endpoint - A singleton endpoint is an endpoint that always 345 contains exactly one member. 347 Registration - A registration is the state machine characterizing a 348 given node's membership in a given endpoint. Any single 349 registration has an associated delivery failure action as defined 350 below and must at any time be in one of two states: Active or 351 Passive. Registrations are local; information about a node's 352 registrations is not expected to be available at other nodes, and 353 the Bundle Protocol does not include a mechanism for distributing 354 information about registrations. 356 Delivery - A bundle is considered to have been delivered at a node 357 subject to a registration as soon as the application data unit that 358 is the payload of the bundle, together with any relevant metadata 359 (an implementation matter), has been presented to the node's 360 application agent in a manner consistent with the state of that 361 registration. 363 Deliverability - A bundle is considered "deliverable" subject to a 364 registration if and only if (a) the bundle's destination endpoint is 365 the endpoint with which the registration is associated, (b) the 366 bundle has not yet been delivered subject to this registration, and 367 (c) the bundle has not yet been "abandoned" (as defined below) 368 subject to this registration. 370 Abandonment - To abandon a bundle subject to some registration is to 371 assert that the bundle is not deliverable subject to that 372 registration. 374 Delivery failure action - The delivery failure action of a 375 registration is the action that is to be taken when a bundle that is 376 "deliverable" subject to that registration is received at a time 377 when the registration is in the Passive state. 379 Destination - The destination of a bundle is the endpoint comprising 380 the node(s) at which the bundle is to be delivered (as defined 381 above). 383 Transmission - A transmission is an attempt by a node's BPA to cause 384 copies of a bundle to be delivered to one or more of the nodes that 385 are members of some endpoint (the bundle's destination) in response 386 to a transmission request issued by the node's application agent. 388 Forwarding - To forward a bundle to a node is to invoke the services 389 of one or more CLAs in a sustained effort to cause a copy of the 390 bundle to be received by that node. 392 Discarding - To discard a bundle is to cease all operations on the 393 bundle and functionally erase all references to it. The specific 394 procedures by which this is accomplished are an implementation 395 matter. 397 Retention constraint - A retention constraint is an element of the 398 state of a bundle that prevents the bundle from being discarded. 399 That is, a bundle cannot be discarded while it has any retention 400 constraints. 402 Deletion - To delete a bundle is to remove unconditionally all of 403 the bundle's retention constraints, enabling the bundle to be 404 discarded. 406 3.2. Discussion of BP concepts 408 Multiple instances of the same bundle (the same unit of DTN protocol 409 data) might exist concurrently in different parts of a network -- 410 possibly differing in some blocks -- in the memory local to one or 411 more bundle nodes and/or in transit between nodes. In the context of 412 the operation of a bundle node, a bundle is an instance (copy), in 413 that node's local memory, of some bundle that is in the network. 415 The payload for a bundle forwarded in response to a bundle 416 transmission request is the application data unit whose location is 417 provided as a parameter to that request. The payload for a bundle 418 forwarded in response to reception of a bundle is the payload of the 419 received bundle. 421 In the most familiar case, a bundle node is instantiated as a single 422 process running on a general-purpose computer, but in general the 423 definition is meant to be broader: a bundle node might alternatively 424 be a thread, an object in an object-oriented operating system, a 425 special-purpose hardware device, etc. 427 The manner in which the functions of the BPA are performed is wholly 428 an implementation matter. For example, BPA functionality might be 429 coded into each node individually; it might be implemented as a 430 shared library that is used in common by any number of bundle nodes 431 on a single computer; it might be implemented as a daemon whose 432 services are invoked via inter-process or network communication by 433 any number of bundle nodes on one or more computers; it might be 434 implemented in hardware. 436 Every CLA implements its own thin layer of protocol, interposed 437 between BP and the (usually "top") protocol(s) of the underlying 438 native protocol stack; this "CL protocol" may only serve to 439 multiplex and de-multiplex bundles to and from the underlying native 440 protocol, or it may offer additional CL-specific functionality. The 441 manner in which a CLA sends and receives bundles, as well as the 442 definitions of CLAs and CL protocols, are beyond the scope of this 443 specification. 445 Note that the administrative element of a node's application agent 446 may itself, in some cases, function as a convergence-layer adapter. 447 That is, outgoing bundles may be "tunneled" through encapsulating 448 bundles: 450 . An outgoing bundle constitutes a byte array. This byte array 451 may, like any other, be presented to the bundle protocol agent 452 as an application data unit that is to be transmitted to some 453 endpoint. 454 . The original bundle thus forms the payload of an encapsulating 455 bundle that is forwarded using some other convergence-layer 456 protocol(s). 457 . When the encapsulating bundle is received, its payload is 458 delivered to the peer application agent administrative element, 459 which then instructs the bundle protocol agent to dispatch that 460 original bundle in the usual way. 462 The purposes for which this technique may be useful (such as cross- 463 domain security) are beyond the scope of this specification. 465 The only interface between the BPA and the application-specific 466 element of the AA is the BP service interface. But between the BPA 467 and the administrative element of the AA there is a (conceptual) 468 private control interface in addition to the BP service interface. 469 This private control interface enables the BPA and the 470 administrative element of the AA to direct each other to take action 471 under specific circumstances. 473 In the case of a node that serves simply as a BP "router", the AA 474 may have no application-specific element at all. The application- 475 specific elements of other nodes' AAs may perform arbitrarily 476 complex application functions, perhaps even offering multiplexed DTN 477 communication services to a number of other applications. As with 478 the BPA, the manner in which the AA performs its functions is wholly 479 an implementation matter. 481 Singletons are the most familiar sort of endpoint, but in general 482 the endpoint notion is meant to be broader. For example, the nodes 483 in a sensor network might constitute a set of bundle nodes that are 484 all registered in a single common endpoint and will all receive any 485 data delivered at that endpoint. *Note* too that any given bundle 486 node might be registered in multiple bundle endpoints and receive 487 all data delivered at each of those endpoints. 489 Recall that every node, by definition, includes an application agent 490 which in turn includes an administrative element, which exchanges 491 administrative records with the administrative elements of other 492 nodes. As such, every node is permanently, structurally registered 493 in the singleton endpoint at which administrative records received 494 from other nodes are delivered. Registration in no other endpoint 495 can ever be assumed to be permanent. This endpoint, termed the 496 node's "administrative endpoint", is therefore uniquely and 497 permanently associated with the node, and for this reason the ID of 498 a node's administrative endpoint additionally serves as the "node 499 ID" (see 4.1.5.2 below) of the node. 501 The destination of every bundle is an endpoint, which may or may not 502 be singleton. The source of every bundle is a node, identified by 503 node ID. Note, though, that the source node ID asserted in a given 504 bundle may be the null endpoint ID (as described later) rather than 505 the ID of the source node; bundles for which the asserted source 506 node ID is the null endpoint ID are termed "anonymous" bundles. 508 Any number of transmissions may be concurrently undertaken by the 509 bundle protocol agent of a given node. 511 When the bundle protocol agent of a node determines that a bundle 512 must be forwarded to a node (either to a node that is a member of 513 the bundle's destination endpoint or to some intermediate forwarding 514 node) in the course of completing the successful transmission of 515 that bundle, the bundle protocol agent invokes the services of one 516 or more CLAs in a sustained effort to cause a copy of the bundle to 517 be received by that node. 519 Upon reception, the processing of a bundle that has been received by 520 a given node depends on whether or not the receiving node is 521 registered in the bundle's destination endpoint. If it is, and if 522 the payload of the bundle is non-fragmentary (possibly as a result 523 of successful payload reassembly from fragmentary payloads, 524 including the original payload of the newly received bundle), then 525 the bundle is normally delivered to the node's application agent 526 subject to the registration characterizing the node's membership in 527 the destination endpoint. 529 The bundle protocol does not natively ensure delivery of a bundle to 530 its destination. Data loss along the path to the destination node 531 can be minimized by utilizing reliable convergence-layer protocols 532 between neighbors on all segments of the end-to-end path, but for 533 end-to-end bundle delivery assurance it will be necessary to develop 534 extensions to the bundle protocol and/or application-layer 535 mechanisms. 537 The bundle protocol is designed for extensibility. Bundle protocol 538 extensions, documented elsewhere, may extend this specification by: 540 . defining additional blocks; 541 . defining additional administrative records; 542 . defining additional bundle processing flags; 543 . defining additional block processing flags; 544 . defining additional types of bundle status reports; 545 . defining additional bundle status report reason codes; 546 . defining additional mandates and constraints on processing 547 that conformant bundle protocol agents must perform at 548 specified points in the inbound and outbound bundle processing 549 cycles. 551 3.3. Services Offered by Bundle Protocol Agents 553 The BPA of each node is expected to provide the following services 554 to the node's application agent: 556 . commencing a registration (registering the node in an 557 endpoint); 558 . terminating a registration; 559 . switching a registration between Active and Passive states; 560 . transmitting a bundle to an identified bundle endpoint; 561 . canceling a transmission; 562 . polling a registration that is in the Passive state; 563 . delivering a received bundle. 565 Note that the details of registration functionality are an 566 implementation matter and are beyond the scope of this 567 specification. 569 4. Bundle Format 571 4.1. Bundle Structure 573 The format of bundles SHALL conform to the Concise Binary Object 574 Representation (CBOR [RFC8949]). 576 Cryptographic verification of a block is possible only if the 577 sequence of octets on which the verifying node computes its hash - 578 the canonicalized representation of the block - is identical to the 579 sequence of octets on which the hash declared for that block was 580 computed. To ensure that blocks are always in canonical 581 representation when they are transmitted and received, the CBOR 582 representations of the values of all fields in all blocks must 583 conform to the rules for Canonical CBOR as specified in [RFC8949]. 585 Each bundle SHALL be a concatenated sequence of at least two blocks, 586 represented as a CBOR indefinite-length array. The first block in 587 the sequence (the first item of the array) MUST be a primary bundle 588 block in CBOR representation as described below; the bundle MUST 589 have exactly one primary bundle block. The primary block MUST be 590 followed by one or more canonical bundle blocks (additional array 591 items) in CBOR representation as described in 4.3.2 below. Every 592 block following the primary block SHALL be the CBOR representation 593 of a canonical block. The last such block MUST be a payload block; 594 the bundle MUST have exactly one payload block. The payload block 595 SHALL be followed by a CBOR "break" stop code, terminating the 596 array. 598 (Note that, while CBOR permits considerable flexibility in the 599 encoding of bundles, this flexibility must not be interpreted as 600 inviting increased complexity in protocol data unit structure.) 602 Associated with each block of a bundle is a block number. The block 603 number uniquely identifies the block within the bundle, enabling 604 blocks (notably bundle security protocol blocks) to reference other 605 blocks in the same bundle without ambiguity. The block number of 606 the primary block is implicitly zero; the block numbers of all other 607 blocks are explicitly stated in block headers as noted below. Block 608 numbering is unrelated to the order in which blocks are sequenced in 609 the bundle. The block number of the payload block is always 1. 611 An implementation of the Bundle Protocol MAY discard any sequence of 612 bytes that does not conform to the Bundle Protocol specification. 614 An implementation of the Bundle Protocol MAY accept a sequence of 615 bytes that does not conform to the Bundle Protocol specification 616 (e.g., one that represents data elements in fixed-length arrays 617 rather than indefinite-length arrays) and transform it into 618 conformant BP structure before processing it. Procedures for 619 accomplishing such a transformation are beyond the scope of this 620 specification. 622 4.2. BP Fundamental Data Structures 624 4.2.1. CRC Type 626 CRC type is an unsigned integer type code for which the following 627 values (and no others) are valid: 629 . 0 indicates "no CRC is present." 630 . 1 indicates "a standard X-25 CRC-16 is present." [CRC16] 631 . 2 indicates "a standard CRC32C (Castagnoli) CRC-32 is present." 632 [RFC4960] 634 CRC type SHALL be represented as a CBOR unsigned integer. 636 For examples of CRC32C CRCs, see Appendix A.4 of [RFC7143]. 638 Note that more robust protection of BP data integrity, as needed, 639 may be provided by means of Block Integrity Blocks as defined in the 640 Bundle Security Protocol [BPSEC]). 642 4.2.2. CRC 644 CRC SHALL be omitted from a block if and only if the block's CRC 645 type code is zero. 647 When not omitted, the CRC SHALL be represented as a CBOR byte string 648 of two bytes (that is, CBOR additional information 2, if CRC type is 649 1) or of four bytes (that is, CBOR additional information 4, if CRC 650 type is 2); in each case the sequence of bytes SHALL constitute an 651 unsigned integer value (of 16 or 32 bits, respectively) in network 652 byte order. 654 4.2.3. Bundle Processing Control Flags 656 Bundle processing control flags assert properties of the bundle as a 657 whole rather than of any particular block of the bundle. They are 658 conveyed in the primary block of the bundle. 660 The following properties are asserted by the bundle processing 661 control flags: 663 . The bundle is a fragment. (Boolean) 665 . The bundle's payload is an administrative record. (Boolean) 667 . The bundle must not be fragmented. (Boolean) 669 . Acknowledgment by the user application is requested. (Boolean) 671 . Status time is requested in all status reports. (Boolean) 673 . Flags requesting types of status reports (all Boolean): 675 o Request reporting of bundle reception. 677 o Request reporting of bundle forwarding. 679 o Request reporting of bundle delivery. 681 o Request reporting of bundle deletion. 683 If the bundle processing control flags indicate that the bundle's 684 application data unit is an administrative record, then all status 685 report request flag values MUST be zero. 687 If the bundle's source node is omitted (i.e., the source node ID is 688 the ID of the null endpoint, which has no members as discussed 689 below; this option enables anonymous bundle transmission), then the 690 bundle is not uniquely identifiable and all bundle protocol features 691 that rely on bundle identity must therefore be disabled: the "Bundle 692 must not be fragmented" flag value MUST be 1 and all status report 693 request flag values MUST be zero. 695 Bundle processing control flags that are unrecognized MUST be 696 ignored, as future definitions of additional flags might not be 697 integrated simultaneously into the Bundle Protocol implementations 698 operating at all nodes. 700 The bundle processing control flags SHALL be represented as a CBOR 701 unsigned integer item, the value of which SHALL be processed as a 702 bit field indicating the control flag values as follows (note that 703 bit numbering in this instance is reversed from the usual practice, 704 beginning with the low-order bit instead of the high-order bit, in 705 recognition of the potential definition of additional control flag 706 values in the future): 708 . Bit 0 (the low-order bit, 0x000001): bundle is a fragment. 709 . Bit 1 (0x000002): payload is an administrative record. 710 . Bit 2 (0x000004): bundle must not be fragmented. 711 . Bit 3 (0x000008): reserved. 712 . Bit 4 (0x000010): reserved. 713 . Bit 5 (0x000020): user application acknowledgement is 714 requested. 715 . Bit 6 (0x000040): status time is requested in all status 716 reports. 717 . Bit 7 (0x000080): reserved. 718 . Bit 8 (0x000100): reserved. 719 . Bit 9 (0x000200): reserved. 720 . Bit 10(0x000400): reserved. 721 . Bit 11(0x000800): reserved. 722 . Bit 12(0x001000): reserved. 723 . Bit 13(0x002000): reserved. 724 . Bit 14(0x004000): bundle reception status reports are 725 requested. 726 . Bit 15(0x008000): reserved. 727 . Bit 16(0x010000): bundle forwarding status reports are 728 requested. 729 . Bit 17(0x020000): bundle delivery status reports are requested. 730 . Bit 18(0x040000): bundle deletion status reports are requested. 731 . Bits 19-20 are reserved. 732 . Bits 21-63 are unassigned. 734 4.2.4. Block Processing Control Flags 736 The block processing control flags assert properties of canonical 737 bundle blocks. They are conveyed in the header of the block to 738 which they pertain. 740 Block processing control flags that are unrecognized MUST be 741 ignored, as future definitions of additional flags might not be 742 integrated simultaneously into the Bundle Protocol implementations 743 operating at all nodes. 745 The block processing control flags SHALL be represented as a CBOR 746 unsigned integer item, the value of which SHALL be processed as a 747 bit field indicating the control flag values as follows (note that 748 bit numbering in this instance is reversed from the usual practice, 749 beginning with the low-order bit instead of the high-order bit, for 750 agreement with the bit numbering of the bundle processing control 751 flags): 753 . Bit 0(the low-order bit, 0x01): block must be replicated in 754 every fragment. 755 . Bit 1(0x02): transmission of a status report is requested if 756 block can't be processed. 757 . Bit 2(0x04): bundle must be deleted if block can't be 758 processed. 759 . Bit 3(0x08): reserved. 760 . Bit 4(0x10): block must be removed from bundle if it can't be 761 processed. 762 . Bit 5(0x20): reserved. 763 . Bit 6 (0x40): reserved. 764 . Bits 7-63 are unassigned. 766 For each bundle whose bundle processing control flags indicate that 767 the bundle's application data unit is an administrative record, or 768 whose source node ID is the null endpoint ID as defined below, the 769 value of the "Transmit status report if block can't be processed" 770 flag in every canonical block of the bundle MUST be zero. 772 4.2.5. Identifiers 774 4.2.5.1. Endpoint ID 776 The destinations of bundles are bundle endpoints, identified by text 777 strings termed "endpoint IDs" (see Section 3.1). Each endpoint ID 778 (EID) is a Uniform Resource Identifier (URI; [URI]). As such, each 779 endpoint ID can be characterized as having this general structure: 781 < scheme name > : < scheme-specific part, or "SSP" > 783 The scheme identified by the < scheme name > in an endpoint ID is a 784 set of syntactic and semantic rules that fully explain how to parse 785 and interpret the SSP. Each scheme that may be used to form a BP 786 endpoint ID must be added to the registry of URI scheme code numbers 787 for Bundle Protocol maintained by IANA as described in Section 10; 788 association of a unique URI scheme code number with each scheme name 789 in this registry helps to enable compact representation of endpoint 790 IDs in bundle blocks. Note that the set of allowable schemes is 791 effectively unlimited. Any scheme conforming to [URIREG] may be 792 added to the URI scheme code number registry and thereupon used in a 793 bundle protocol endpoint ID. 795 Each entry in the URI scheme code number registry MUST contain a 796 reference to a scheme code number definition document, which defines 797 the manner in which the scheme-specific part of any URI formed in 798 that scheme is parsed and interpreted and MUST be encoded, in CBOR 799 representation, for transmission as a BP endpoint ID. The scheme 800 code number definition document may also contain information as to 801 (a) which convergence-layer protocol(s) may be used to forward a 802 bundle to a BP destination endpoint identified by such an ID, and 803 (b) how the ID of the convergence-layer protocol endpoint to use for 804 that purpose can be inferred from that destination endpoint ID. 806 Note that, although endpoint IDs are URIs, implementations of the BP 807 service interface may support expression of endpoint IDs in some 808 internationalized manner (e.g., Internationalized Resource 809 Identifiers (IRIs); see [RFC3987]). 811 Each BP endpoint ID (EID) SHALL be represented as a CBOR array 812 comprising two items. 814 The first item of the array SHALL be the code number identifying the 815 endpoint ID's URI scheme, as defined in the registry of URI scheme 816 code numbers for Bundle Protocol. Each URI scheme code number SHALL 817 be represented as a CBOR unsigned integer. 819 The second item of the array SHALL be the applicable CBOR 820 representation of the scheme-specific part (SSP) of the EID, defined 821 as noted in the references(s) for the URI scheme code number 822 registry entry for the EID's URI scheme. 824 4.2.5.1.1. The "dtn" URI scheme 826 The "dtn" scheme supports the identification of BP endpoints by 827 arbitrarily expressive character strings. It is specified as 828 follows: 830 Scheme syntax: This specification uses the Augmented Backus-Naur 831 Form (ABNF) notation of [RFC5234]. 833 dtn-uri = "dtn:" ("none" / dtn-hier-part) 835 dtn-hier-part = "//" node-name name-delim demux ; a path-rootless 837 node-name = 1*(ALPHA/DIGIT/"-"/"."/"_") reg-name 839 name-delim = "/" 841 demux = *VCHAR 842 Scheme semantics: URIs of the dtn scheme are used as endpoint 843 identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol 844 (BP) as described in the present document. 846 The endpoint ID "dtn:none" identifies the "null endpoint", the 847 endpoint that by definition never has any members. 849 All BP endpoints identified by all other dtn-scheme endpoint IDs for 850 which the first character of demux is a character other than '~' 851 (tilde) are singleton endpoints. All BP endpoints identified by dtn- 852 scheme endpoint IDs for which the first character *is* '~' (tilde) 853 are *not* singleton endpoints. 855 A dtn-scheme endpoint ID for which the demux is of length zero MAY 856 identify the administrative endpoint for the node identified by 857 node-name, and as such may serve as a node ID. No dtn-scheme 858 endpoint ID for which the demux is of non-zero length may do so. 860 Note that these syntactic rules impose constraints on dtn-scheme 861 endpoint IDs that were not imposed by the original specification of 862 the dtn scheme as provided in [RFC5050]. It is believed that the 863 dtn-scheme endpoint IDs employed by BP applications conforming to 864 [RFC5050] are in most cases unlikely to be in violation of these 865 rules, but the developers of such applications are advised of the 866 potential for compromised interoperation. 868 Encoding considerations: For transmission as a BP endpoint ID, the 869 scheme-specific part of a URI of the dtn scheme SHALL be represented 870 as a CBOR text string unless the EID's SSP is "none", in which case 871 the SSP SHALL be represented as a CBOR unsigned integer with the 872 value zero. For all other purposes, URIs of the dtn scheme are 873 encoded exclusively in US-ASCII characters. 875 Interoperability considerations: none. 877 Security considerations: 879 . Reliability and consistency: none of the BP endpoints 880 identified by the URIs of the dtn scheme are guaranteed to be 881 reachable at any time, and the identity of the processing 882 entities operating on those endpoints is never guaranteed by 883 the Bundle Protocol itself. Bundle authentication as defined by 884 the Bundle Security Protocol is required for this purpose. 885 . Malicious construction: malicious construction of a conformant 886 dtn-scheme URI is limited to the malicious selection of node 887 names and the malicious selection of demux strings. That is, a 888 maliciously constructed dtn-scheme URI could be used to direct 889 a bundle to an endpoint that might be damaged by the arrival of 890 that bundle or, alternatively, to declare a false source for a 891 bundle and thereby cause incorrect processing at a node that 892 receives the bundle. In both cases (and indeed in all bundle 893 processing), the node that receives a bundle should verify its 894 authenticity and validity before operating on it in any way. 895 . Back-end transcoding: the limited expressiveness of URIs of the 896 dtn scheme effectively eliminates the possibility of threat due 897 to errors in back-end transcoding. 898 . Rare IP address formats: not relevant, as IP addresses do not 899 appear anywhere in conformant dtn-scheme URIs. 900 . Sensitive information: because dtn-scheme URIs are used only to 901 represent the identities of Bundle Protocol endpoints, the risk 902 of disclosure of sensitive information due to interception of 903 these URIs is minimal. Examination of dtn-scheme URIs could be 904 used to support traffic analysis; where traffic analysis is a 905 plausible danger, bundles should be conveyed by secure 906 convergence-layer protocols that do not expose endpoint IDs. 907 . Semantic attacks: the simplicity of dtn-scheme URI syntax 908 minimizes the possibility of misinterpretation of a URI by a 909 human user. 911 4.2.5.1.2. The "ipn" URI scheme 913 The "ipn" scheme supports the identification of BP endpoints by 914 pairs of unsigned integers, for compact representation in bundle 915 blocks. It is specified as follows: 917 Scheme syntax: This specification uses the Augmented Backus-Naur 918 Form (ABNF) notation of [RFC5234], including the core ABNF syntax 919 rule for DIGIT defined by that specification. 921 ipn-uri = "ipn:" ipn-hier-part 923 ipn-hier-part = node-nbr nbr-delim service-nbr ; a path-rootless 925 node-nbr = 1*DIGIT 927 nbr-delim = "." 929 service-nbr = 1*DIGIT 931 Scheme semantics: URIs of the ipn scheme are used as endpoint 932 identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol 933 (BP) as described in the present document. 935 All BP endpoints identified by ipn-scheme endpoint IDs are singleton 936 endpoints. 938 An ipn-scheme endpoint ID for which service-nbr is zero MAY identify 939 the administrative endpoint for the node identified by node-nbr, and 940 as such may serve as a node ID. No ipn-scheme endpoint ID for which 941 service-nbr is non-zero may do so. 943 Encoding considerations: For transmission as a BP endpoint ID, the 944 scheme-specific part of a URI of the ipn scheme the SSP SHALL be 945 represented as a CBOR array comprising two items. The first item of 946 this array SHALL be the EID's node number (a number that identifies 947 the node) represented as a CBOR unsigned integer. The second item 948 of this array SHALL be the EID's service number (a number that 949 identifies some application service) represented as a CBOR unsigned 950 integer. For all other purposes, URIs of the ipn scheme are encoded 951 exclusively in US-ASCII characters. 953 Interoperability considerations: none. 955 Security considerations: 957 . Reliability and consistency: none of the BP endpoints 958 identified by the URIs of the ipn scheme are guaranteed to be 959 reachable at any time, and the identity of the processing 960 entities operating on those endpoints is never guaranteed by 961 the Bundle Protocol itself. Bundle authentication as defined by 962 the Bundle Security Protocol [BPSEC] is required for this 963 purpose. 964 . Malicious construction: malicious construction of a conformant 965 ipn-scheme URI is limited to the malicious selection of node 966 numbers and the malicious selection of service numbers. That 967 is, a maliciously constructed ipn-scheme URI could be used to 968 direct a bundle to an endpoint that might be damaged by the 969 arrival of that bundle or, alternatively, to declare a false 970 source for a bundle and thereby cause incorrect processing at a 971 node that receives the bundle. In both cases (and indeed in 972 all bundle processing), the node that receives a bundle should 973 verify its authenticity and validity before operating on it in 974 any way. 975 . Back-end transcoding: the limited expressiveness of URIs of the 976 ipn scheme effectively eliminates the possibility of threat due 977 to errors in back-end transcoding. 978 . Rare IP address formats: not relevant, as IP addresses do not 979 appear anywhere in conformant ipn-scheme URIs. 980 . Sensitive information: because ipn-scheme URIs are used only to 981 represent the identities of Bundle Protocol endpoints, the risk 982 of disclosure of sensitive information due to interception of 983 these URIs is minimal. Examination of ipn-scheme URIs could be 984 used to support traffic analysis; where traffic analysis is a 985 plausible danger, bundles should be conveyed by secure 986 convergence-layer protocols that do not expose endpoint IDs. 987 . Semantic attacks: the simplicity of ipn-scheme URI syntax 988 minimizes the possibility of misinterpretation of a URI by a 989 human user. 991 4.2.5.2. Node ID 993 For many purposes of the Bundle Protocol it is important to identify 994 the node that is operative in some context. 996 As discussed in 3.1 above, nodes are distinct from endpoints; 997 specifically, an endpoint is a set of zero or more nodes. But 998 rather than define a separate namespace for node identifiers, we 999 instead use endpoint identifiers to identify nodes as discussed in 1000 3.2 above. Formally: 1002 . Every node is, by definition, permanently registered in the 1003 singleton endpoint at which administrative records are 1004 delivered to its application agent's administrative element, 1005 termed the node's "administrative endpoint". 1006 . As such, the EID of a node's administrative endpoint SHALL 1007 uniquely identify that node. 1008 . A "node ID" is an EID that identifies the administrative 1009 endpoint of a node. 1011 4.2.6. DTN Time 1013 A DTN time is an unsigned integer indicating the number of 1014 milliseconds that have elapsed since the DTN Epoch, 2000-01-01 1015 00:00:00 +0000 (UTC). DTN time is not affected by leap seconds. 1017 Each DTN time SHALL be represented as a CBOR unsigned integer item. 1018 Implementers need to be aware that DTN time values conveyed in CBOR 1019 representation in bundles will nearly always exceed (2**32 - 1); the 1020 manner in which a DTN time value is represented in memory is an 1021 implementation matter. The DTN time value zero indicates that the 1022 time is unknown. 1024 4.2.7. Creation Timestamp 1026 Each bundle's creation timestamp SHALL be represented as a CBOR 1027 array comprising two items. 1029 The first item of the array, termed "bundle creation time", SHALL be 1030 the DTN time at which the transmission request was received that 1031 resulted in the creation of the bundle, represented as a CBOR 1032 unsigned integer. 1034 The second item of the array, termed the creation timestamp's 1035 "sequence number", SHALL be the latest value (as of the time at 1036 which the transmission request was received) of a monotonically 1037 increasing positive integer counter managed by the source node's 1038 bundle protocol agent, represented as a CBOR unsigned integer. The 1039 sequence counter MAY be reset to zero whenever the current time 1040 advances by one millisecond. 1042 For nodes that lack accurate clocks, it is recommended that bundle 1043 creation time be set to zero and that the counter used as the source 1044 of the bundle sequence count never be reset to zero. 1046 Note that, in general, the creation of two distinct bundles with the 1047 same source node ID and bundle creation timestamp may result in 1048 unexpected network behavior and/or suboptimal performance. The 1049 combination of source node ID and bundle creation timestamp serves 1050 to identify a single transmission request, enabling it to be 1051 acknowledged by the receiving application (provided the source node 1052 ID is not the null endpoint ID). 1054 4.2.8. Block-type-specific Data 1056 Block-type-specific data in each block (other than the primary 1057 block) SHALL be the applicable CBOR representation of the content of 1058 the block. Details of this representation are included in the 1059 specification defining the block type. 1061 4.3. Block Structures 1063 This section describes the primary block in detail and non-primary 1064 blocks in general. Rules for processing these blocks appear in 1065 Section 5 of this document. 1067 Note that supplementary DTN protocol specifications (including, but 1068 not restricted to, the Bundle Security Protocol [BPSEC]) may require 1069 that BP implementations conforming to those protocols construct and 1070 process additional blocks. 1072 4.3.1. Primary Bundle Block 1074 The primary bundle block contains the basic information needed to 1075 forward bundles to their destinations. 1077 Each primary block SHALL be represented as a CBOR array; the number 1078 of elements in the array SHALL be 8 (if the bundle is not a fragment 1079 and the block has no CRC), 9 (if the block has a CRC and the bundle 1080 is not a fragment), 10 (if the bundle is a fragment and the block 1081 has no CRC), or 11 (if the bundle is a fragment and the block has a 1082 CRC). 1084 The primary block of each bundle SHALL be immutable. The CBOR- 1085 encoded values of all fields in the primary block MUST remain 1086 unchanged from the time the block is created to the time it is 1087 delivered. 1089 The fields of the primary bundle block SHALL be as follows, listed 1090 in the order in which they MUST appear: 1092 Version: An unsigned integer value indicating the version of the 1093 bundle protocol that constructed this block. The present document 1094 describes version 7 of the bundle protocol. Version number SHALL be 1095 represented as a CBOR unsigned integer item. 1097 Bundle Processing Control Flags: The Bundle Processing Control Flags 1098 are discussed in Section 4.2.3. above. 1100 CRC Type: CRC Type codes are discussed in Section 4.2.1. above. The 1101 CRC Type code for the primary block MAY be zero if the bundle 1102 contains a BPsec [BPSEC] Block Integrity Block whose target is the 1103 primary block; otherwise the CRC Type code for the primary block 1104 MUST be non-zero. 1106 Destination EID: The Destination EID field identifies the bundle 1107 endpoint that is the bundle's destination, i.e., the endpoint that 1108 contains the node(s) at which the bundle is to be delivered. 1110 Source node ID: The Source node ID field identifies the bundle node 1111 at which the bundle was initially transmitted, except that Source 1112 node ID may be the null endpoint ID in the event that the bundle's 1113 source chooses to remain anonymous. 1115 Report-to EID: The Report-to EID field identifies the bundle 1116 endpoint to which status reports pertaining to the forwarding and 1117 delivery of this bundle are to be transmitted. 1119 Creation Timestamp: The creation timestamp comprises two unsigned 1120 integers that, together with the source node ID and (if the bundle 1121 is a fragment) the fragment offset and payload length, serve to 1122 identify the bundle. See 4.2.7 above for the definition of this 1123 field. 1125 Lifetime: The lifetime field is an unsigned integer that indicates 1126 the time at which the bundle's payload will no longer be useful, 1127 encoded as a number of milliseconds past the creation time. (For 1128 high-rate deployments with very brief disruptions, fine-grained 1129 expression of bundle lifetime may be useful.) When a bundle's age 1130 exceeds its lifetime, bundle nodes need no longer retain or forward 1131 the bundle; the bundle SHOULD be deleted from the network. 1133 If the asserted lifetime for a received bundle is so lengthy that 1134 retention of the bundle until its expiration time might degrade 1135 operation of the node at which the bundle is received, or if the 1136 bundle protocol agent of that node determines that the bundle must 1137 be deleted in order to prevent network performance degradation 1138 (e.g., the bundle appears to be part of a denial-of-service attack), 1139 then that bundle protocol agent MAY impose a temporary overriding 1140 lifetime of shorter duration; such overriding lifetime SHALL NOT 1141 replace the lifetime asserted in the bundle but SHALL serve as the 1142 bundle's effective lifetime while the bundle resides at that node. 1143 Procedures for imposing lifetime overrides are beyond the scope of 1144 this specification. 1146 For bundles originating at nodes that lack accurate clocks, it is 1147 recommended that bundle age be obtained from the Bundle Age 1148 extension block (see 4.4.2 below) rather than from the difference 1149 between current time and bundle creation time. Bundle lifetime 1150 SHALL be represented as a CBOR unsigned integer item. 1152 Fragment offset: If and only if the Bundle Processing Control Flags 1153 of this Primary block indicate that the bundle is a fragment, 1154 fragment offset SHALL be present in the primary block. Fragment 1155 offset SHALL be represented as a CBOR unsigned integer indicating 1156 the offset from the start of the original application data unit at 1157 which the bytes comprising the payload of this bundle were located. 1159 Total Application Data Unit Length: If and only if the Bundle 1160 Processing Control Flags of this Primary block indicate that the 1161 bundle is a fragment, total application data unit length SHALL be 1162 present in the primary block. Total application data unit length 1163 SHALL be represented as a CBOR unsigned integer indicating the total 1164 length of the original application data unit of which this bundle's 1165 payload is a part. 1167 CRC: A CRC SHALL be present in the primary block unless the bundle 1168 includes a BPsec [BPSEC] Block Integrity Block whose target is the 1169 primary block, in which case a CRC MAY be present in the primary 1170 block. The length and nature of the CRC SHALL be as indicated by 1171 the CRC type. The CRC SHALL be computed over the concatenation of 1172 all bytes (including CBOR "break" characters) of the primary block 1173 including the CRC field itself, which for this purpose SHALL be 1174 temporarily populated with all bytes set to zero. 1176 4.3.2. Canonical Bundle Block Format 1178 Every block other than the primary block (all such blocks are termed 1179 "canonical" blocks) SHALL be represented as a CBOR array; the number 1180 of elements in the array SHALL be 5 (if CRC type is zero) or 6 1181 (otherwise). 1183 The fields of every canonical block SHALL be as follows, listed in 1184 the order in which they MUST appear: 1186 . Block type code, an unsigned integer. Bundle block type code 1 1187 indicates that the block is a bundle payload block. Block type 1188 codes 2 through 9 are explicitly reserved as noted later in 1189 this specification. Block type codes 192 through 255 are not 1190 reserved and are available for private and/or experimental use. 1191 All other block type code values are reserved for future use. 1192 . Block number, an unsigned integer as discussed in 4.1 above. 1193 Block number SHALL be represented as a CBOR unsigned integer. 1194 . Block processing control flags as discussed in Section 4.2.4 1195 above. 1196 . CRC type as discussed in Section 4.2.1 above. 1197 . Block-type-specific data represented as a single definite- 1198 length CBOR byte string, i.e., a CBOR byte string that is not 1199 of indefinite length. For each type of block, the block-type- 1200 specific data byte string is the serialization, in a block- 1201 type-specific manner, of the data conveyed by that type of 1202 block; definitions of blocks are required to define the manner 1203 in which block-type-specific data are serialized within the 1204 block-type-specific data field. For the Payload Block in 1205 particular (block type 1), the block-type-specific data field, 1206 termed the "payload", SHALL be an application data unit, or 1207 some contiguous extent thereof, represented as a definite- 1208 length CBOR byte string. 1209 . If and only if the value of the CRC type field of this block is 1210 non-zero, a CRC. If present, the length and nature of the CRC 1211 SHALL be as indicated by the CRC type and the CRC SHALL be 1212 computed over the concatenation of all bytes of the block 1213 (including CBOR "break" characters) including the CRC field 1214 itself, which for this purpose SHALL be temporarily populated 1215 with all bytes set to zero. 1217 4.4. Extension Blocks 1219 "Extension blocks" are all blocks other than the primary and payload 1220 blocks. Three types of extension blocks are defined below. All 1221 implementations of the Bundle Protocol specification (the present 1222 document) MUST include procedures for recognizing, parsing, and 1223 acting on, but not necessarily producing, these types of extension 1224 blocks. 1226 The specifications for additional types of extension blocks must 1227 indicate whether or not BP implementations conforming to those 1228 specifications must recognize, parse, act on, and/or produce blocks 1229 of those types. As not all nodes will necessarily instantiate BP 1230 implementations that conform to those additional specifications, it 1231 is possible for a node to receive a bundle that includes extension 1232 blocks that the node cannot process. The values of the block 1233 processing control flags indicate the action to be taken by the 1234 bundle protocol agent when this is the case. 1236 No mandated procedure in this specification is unconditionally 1237 dependent on the absence or presence of any extension block. 1238 Therefore any bundle protocol agent MAY insert or remove any 1239 extension block in any bundle, subject to all mandates in the Bundle 1240 Protocol specification and all extension block specifications to 1241 which the node's BP implementation conforms. Note that removal of 1242 an extension block will probably disable one or more elements of 1243 bundle processing that were intended by the BPA that inserted that 1244 block. In particular, note that removal of an extension block that 1245 is one of the targets of a BPsec security block may render the 1246 bundle unverifiable. 1248 The following extension blocks are defined in the current document. 1250 4.4.1. Previous Node 1252 The Previous Node block, block type 6, identifies the node that 1253 forwarded this bundle to the local node (i.e., to the node at which 1254 the bundle currently resides); its block-type-specific data is the 1255 node ID of that forwarder node which SHALL take the form of a node 1256 ID represented as described in Section 4.2.5.2. above. If the local 1257 node is the source of the bundle, then the bundle MUST NOT contain 1258 any Previous Node block. Otherwise the bundle SHOULD contain one 1259 (1) occurrence of this type of block and MUST NOT contain more than 1260 one. 1262 4.4.2. Bundle Age 1264 The Bundle Age block, block type 7, contains the number of 1265 milliseconds that have elapsed between the time the bundle was 1266 created and time at which it was most recently forwarded. It is 1267 intended for use by nodes lacking access to an accurate clock, to 1268 aid in determining the time at which a bundle's lifetime expires. 1269 The block-type-specific data of this block is an unsigned integer 1270 containing the age of the bundle in milliseconds, which SHALL be 1271 represented as a CBOR unsigned integer item. (The age of the bundle 1272 is the sum of all known intervals of the bundle's residence at 1273 forwarding nodes, up to the time at which the bundle was most 1274 recently forwarded, plus the summation of signal propagation time 1275 over all episodes of transmission between forwarding nodes. 1276 Determination of these values is an implementation matter.) If the 1277 bundle's creation time is zero, then the bundle MUST contain exactly 1278 one (1) occurrence of this type of block; otherwise, the bundle MAY 1279 contain at most one (1) occurrence of this type of block. A bundle 1280 MUST NOT contain multiple occurrences of the bundle age block, as 1281 this could result in processing anomalies. 1283 4.4.3. Hop Count 1285 The Hop Count block, block type 10, contains two unsigned integers, 1286 hop limit and hop count. A "hop" is here defined as an occasion on 1287 which a bundle was forwarded from one node to another node. Hop 1288 limit MUST be in the range 1 through 255. The hop limit value SHOULD 1289 NOT be changed at any time after creation of the Hop Count block; 1290 the hop count value SHOULD initially be zero and SHOULD be increased 1291 by 1 on each hop. 1293 The hop count block is mainly intended as a safety mechanism, a 1294 means of identifying bundles for removal from the network that can 1295 never be delivered due to a persistent forwarding error. Hop count 1296 is particularly valuable as a defense against routing anomalies that 1297 might cause a bundle to be forwarded in a cyclical "ping-pong" 1298 fashion between two nodes. When a bundle's hop count exceeds its 1299 hop limit, the bundle SHOULD be deleted for the reason "hop limit 1300 exceeded", following the bundle deletion procedure defined in 1301 Section 5.10. 1303 Procedures for determining the appropriate hop limit for a bundle 1304 are beyond the scope of this specification. 1306 The block-type-specific data in a hop count block SHALL be 1307 represented as a CBOR array comprising two items. The first item of 1308 this array SHALL be the bundle's hop limit, represented as a CBOR 1309 unsigned integer. The second item of this array SHALL be the 1310 bundle's hop count, represented as a CBOR unsigned integer. A bundle 1311 MAY contain one occurrence of this type of block but MUST NOT 1312 contain more than one. 1314 5. Bundle Processing 1316 The bundle processing procedures mandated in this section and in 1317 Section 6 govern the operation of the Bundle Protocol Agent and the 1318 Application Agent administrative element of each bundle node. They 1319 are neither exhaustive nor exclusive. Supplementary DTN protocol 1320 specifications (including, but not restricted to, the Bundle 1321 Security Protocol [BPSEC]) may augment, override, or supersede the 1322 mandates of this document. 1324 5.1. Generation of Administrative Records 1326 All transmission of bundles is in response to bundle transmission 1327 requests presented by nodes' application agents. When required to 1328 "generate" an administrative record (such as a bundle status 1329 report), the bundle protocol agent itself is responsible for causing 1330 a new bundle to be transmitted, conveying that record. In concept, 1331 the bundle protocol agent discharges this responsibility by 1332 directing the administrative element of the node's application agent 1333 to construct the record and request its transmission as detailed in 1334 Section 6 below. In practice, the manner in which administrative 1335 record generation is accomplished is an implementation matter, 1336 provided the constraints noted in Section 6 are observed. 1338 Status reports are relatively small bundles. Moreover, even when 1339 the generation of status reports is enabled the decision on whether 1340 or not to generate a requested status report is left to the 1341 discretion of the bundle protocol agent. Nonetheless, note that 1342 requesting status reports for any single bundle might easily result 1343 in the generation of (1 + (2 *(N-1))) status report bundles, where N 1344 is the number of nodes on the path from the bundle's source to its 1345 destination, inclusive. That is, the requesting of status reports 1346 for large numbers of bundles could result in an unacceptable 1347 increase in the bundle traffic in the network. For this reason, the 1348 generation of status reports MUST be disabled by default and enabled 1349 only when the risk of excessive network traffic is deemed 1350 acceptable. Mechanisms that could assist in assessing and 1351 mitigating this risk, such as pre-placed agreements authorizing the 1352 generation of status reports under specified circumstances, are 1353 beyond the scope of this specification. 1355 Notes on administrative record terminology: 1357 . A "bundle reception status report" is a bundle status report 1358 with the "reporting node received bundle" flag set to 1. 1359 . A "bundle forwarding status report" is a bundle status report 1360 with the "reporting node forwarded the bundle" flag set to 1. 1361 . A "bundle delivery status report" is a bundle status report 1362 with the "reporting node delivered the bundle" flag set to 1. 1363 . A "bundle deletion status report" is a bundle status report 1364 with the "reporting node deleted the bundle" flag set to 1. 1366 5.2. Bundle Transmission 1368 The steps in processing a bundle transmission request are: 1370 Step 1: Transmission of the bundle is initiated. An outbound bundle 1371 MUST be created per the parameters of the bundle transmission 1372 request, with the retention constraint "Dispatch pending". The 1373 source node ID of the bundle MUST be either the null endpoint ID, 1374 indicating that the source of the bundle is anonymous, or else the 1375 EID of a singleton endpoint whose only member is the node of which 1376 the BPA is a component. 1378 Step 2: Processing proceeds from Step 1 of Section 5.4. 1380 5.3. Bundle Dispatching 1382 (Note that this procedure is initiated only following completion of 1383 Step 4 of Section 5.6.) 1385 The steps in dispatching a bundle are: 1387 Step 1: If the bundle's destination endpoint is an endpoint of which 1388 the node is a member, the bundle delivery procedure defined in 1389 Section 5.7 MUST be followed and for the purposes of all subsequent 1390 processing of this bundle at this node the node's membership in the 1391 bundle's destination endpoint SHALL be disavowed; specifically, even 1392 though the node is a member of the bundle's destination endpoint, 1393 the node SHALL NOT undertake to forward the bundle to itself in the 1394 course of performing the procedure described in Section 5.4. 1396 Step 2: Processing proceeds from Step 1 of Section 5.4. 1398 5.4. Bundle Forwarding 1400 The steps in forwarding a bundle are: 1402 Step 1: The retention constraint "Forward pending" MUST be added to 1403 the bundle, and the bundle's "Dispatch pending" retention constraint 1404 MUST be removed. 1406 Step 2: The bundle protocol agent MUST determine whether or not 1407 forwarding is contraindicated (that is, rendered inadvisable) for 1408 any of the reasons listed in the IANA registry of Bundle Status 1409 Report Reason Codes (see section 10.5 below), whose initial contents 1410 are listed in Figure 4. In particular: 1412 . The bundle protocol agent MAY choose either to forward the 1413 bundle directly to its destination node(s) (if possible) or to 1414 forward the bundle to some other node(s) for further 1415 forwarding. The manner in which this decision is made may 1416 depend on the scheme name in the destination endpoint ID and/or 1417 on other state but in any case is beyond the scope of this 1418 document; one possible mechanism is described in [SABR]. If the 1419 BPA elects to forward the bundle to some other node(s) for 1420 further forwarding but finds it impossible to select any 1421 node(s) to forward the bundle to, then forwarding is 1422 contraindicated. 1423 . Provided the bundle protocol agent succeeded in selecting the 1424 node(s) to forward the bundle to, the bundle protocol agent 1425 MUST subsequently select the convergence layer adapter(s) whose 1426 services will enable the node to send the bundle to those 1427 nodes. The manner in which specific appropriate convergence 1428 layer adapters are selected is beyond the scope of this 1429 document; the TCP convergence-layer adapter [TCPCL] MUST be 1430 implemented when some or all of the bundles forwarded by the 1431 bundle protocol agent must be forwarded via the Internet but 1432 may not be appropriate for the forwarding of any particular 1433 bundle. If the agent finds it impossible to select any 1434 appropriate convergence layer adapter(s) to use in forwarding 1435 this bundle, then forwarding is contraindicated. 1437 Step 3: If forwarding of the bundle is determined to be 1438 contraindicated for any of the reasons listed in the IANA registry 1439 of Bundle Status Report Reason Codes (see section 10.5 below), then 1440 the Forwarding Contraindicated procedure defined in Section 5.4.1 1441 MUST be followed; the remaining steps of Section 5.4 are skipped at 1442 this time. 1444 Step 4: For each node selected for forwarding, the bundle protocol 1445 agent MUST invoke the services of the selected convergence layer 1446 adapter(s) in order to effect the sending of the bundle to that 1447 node. Determining the time at which the bundle protocol agent 1448 invokes convergence layer adapter services is a BPA implementation 1449 matter. Determining the time at which each convergence layer 1450 adapter subsequently responds to this service invocation by sending 1451 the bundle is a convergence-layer adapter implementation matter. 1452 Note that: 1454 . If the bundle has a Previous Node block, as defined in 4.4.1 1455 above, then that block MUST be removed from the bundle before 1456 the bundle is forwarded. 1457 . If the bundle protocol agent is configured to attach Previous 1458 Node blocks to forwarded bundles, then a Previous Node block 1459 containing the node ID of the forwarding node MUST be inserted 1460 into the bundle before the bundle is forwarded. 1461 . If the bundle has a bundle age block, as defined in 4.4.2. 1462 above, then at the last possible moment before the CLA 1463 initiates conveyance of the bundle via the CL protocol the 1464 bundle age value MUST be increased by the difference between 1465 the current time and the time at which the bundle was received 1466 (or, if the local node is the source of the bundle, created). 1468 Step 5: When all selected convergence layer adapters have informed 1469 the bundle protocol agent that they have concluded their data 1470 sending procedures with regard to this bundle, processing may depend 1471 on the results of those procedures. 1473 If completion of the data sending procedures by all selected 1474 convergence layer adapters has not resulted in successful forwarding 1475 of the bundle (an implementation-specific determination that is 1476 beyond the scope of this specification), then the bundle protocol 1477 agent MAY choose (in an implementation-specific manner, again beyond 1478 the scope of this specification) to initiate another attempt to 1479 forward the bundle. In that event, processing proceeds from Step 4. 1480 The minimum number of times a given node will initiate another 1481 forwarding attempt for any single bundle in this event (a number 1482 which may be zero) is a node configuration parameter that must be 1483 exposed to other nodes in the network to the extent that this is 1484 required by the operating environment. 1486 If completion of the data sending procedures by all selected 1487 convergence layer adapters HAS resulted in successful forwarding of 1488 the bundle, or if it has not but the bundle protocol agent does not 1489 choose to initiate another attempt to forward the bundle, then: 1491 . If the "request reporting of bundle forwarding" flag in the 1492 bundle's status report request field is set to 1, and status 1493 reporting is enabled, then a bundle forwarding status report 1494 SHOULD be generated, destined for the bundle's report-to 1495 endpoint ID. The reason code on this bundle forwarding status 1496 report MUST be "no additional information". 1497 . If any applicable bundle protocol extensions mandate generation 1498 of status reports upon conclusion of convergence-layer data 1499 sending procedures, all such status reports SHOULD be generated 1500 with extension-mandated reason codes. 1501 . The bundle's "Forward pending" retention constraint MUST be 1502 removed. 1504 5.4.1. Forwarding Contraindicated 1506 The steps in responding to contraindication of forwarding are: 1508 Step 1: The bundle protocol agent MUST determine whether or not to 1509 declare failure in forwarding the bundle. Note: this decision is 1510 likely to be influenced by the reason for which forwarding is 1511 contraindicated. 1513 Step 2: If forwarding failure is declared, then the Forwarding 1514 Failed procedure defined in Section 5.4.2 MUST be followed. 1516 Otherwise, when - at some future time - the forwarding of this 1517 bundle ceases to be contraindicated, processing proceeds from Step 4 1518 of Section 5.4. 1520 5.4.2. Forwarding Failed 1522 The steps in responding to a declaration of forwarding failure are: 1524 Step 1: The bundle protocol agent MAY forward the bundle back to the 1525 node that sent it, as identified by the Previous Node block, if 1526 present. This forwarding, if performed, SHALL be accomplished by 1527 performing Step 4 and Step 5 of section 5.4 where the sole node 1528 selected for forwarding SHALL be the node that sent the bundle. 1530 Step 2: If the bundle's destination endpoint is an endpoint of which 1531 the node is a member, then the bundle's "Forward pending" retention 1532 constraint MUST be removed. Otherwise, the bundle MUST be deleted: 1533 the bundle deletion procedure defined in Section 5.10 MUST be 1534 followed, citing the reason for which forwarding was determined to 1535 be contraindicated. 1537 5.5. Bundle Expiration 1539 A bundle expires when the bundle's age exceeds its lifetime as 1540 specified in the primary bundle block or as overridden by the bundle 1541 protocol agent. Bundle age MAY be determined by subtracting the 1542 bundle's creation timestamp time from the current time if (a) that 1543 timestamp time is not zero and (b) the local node's clock is known 1544 to be accurate; otherwise bundle age MUST be obtained from the 1545 Bundle Age extension block. Bundle expiration MAY occur at any 1546 point in the processing of a bundle. When a bundle expires, the 1547 bundle protocol agent MUST delete the bundle for the reason 1548 "lifetime expired" (when the expired lifetime is the lifetime as 1549 specified in the primary block) or "traffic pared" (when the expired 1550 lifetime is a lifetime override as imposed by the bundle protocol 1551 agent): the bundle deletion procedure defined in Section 5.10 MUST 1552 be followed. 1554 5.6. Bundle Reception 1556 The steps in processing a bundle that has been received from another 1557 node are: 1559 Step 1: The retention constraint "Dispatch pending" MUST be added to 1560 the bundle. 1562 Step 2: If the "request reporting of bundle reception" flag in the 1563 bundle's status report request field is set to 1, and status 1564 reporting is enabled, then a bundle reception status report with 1565 reason code "No additional information" SHOULD be generated, 1566 destined for the bundle's report-to endpoint ID. 1568 Step 3: CRCs SHOULD be computed for every block of the bundle that 1569 has an attached CRC. If any block of the bundle is malformed 1570 according to this specification (including syntactically invalid 1571 CBOR), or if any block has an attached CRC and the CRC computed for 1572 this block upon reception differs from that attached CRC, then the 1573 bundle protocol agent MUST delete the bundle for the reason "Block 1574 unintelligible". The bundle deletion procedure defined in Section 1575 5.10 MUST be followed and all remaining steps of the bundle 1576 reception procedure MUST be skipped. 1578 Step 4: For each block in the bundle that is an extension block that 1579 the bundle protocol agent cannot process: 1581 . If the block processing flags in that block indicate that a 1582 status report is requested in this event, and status reporting 1583 is enabled, then a bundle reception status report with reason 1584 code "Block unsupported" SHOULD be generated, destined for the 1585 bundle's report-to endpoint ID. 1586 . If the block processing flags in that block indicate that the 1587 bundle must be deleted in this event, then the bundle protocol 1588 agent MUST delete the bundle for the reason "Block 1589 unsupported"; the bundle deletion procedure defined in Section 1590 5.10 MUST be followed and all remaining steps of the bundle 1591 reception procedure MUST be skipped. 1592 . If the block processing flags in that block do NOT indicate 1593 that the bundle must be deleted in this event but do indicate 1594 that the block must be discarded, then the bundle protocol 1595 agent MUST remove this block from the bundle. 1596 . If the block processing flags in that block indicate neither 1597 that the bundle must be deleted nor that that the block must be 1598 discarded, then processing continues with the next extension 1599 block that the bundle protocol agent cannot process, if any; 1600 otherwise, processing proceeds from step 5. 1602 Step 5: Processing proceeds from Step 1 of Section 5.3. 1604 5.7. Local Bundle Delivery 1606 The steps in processing a bundle that is destined for an endpoint of 1607 which this node is a member are: 1609 Step 1: If the received bundle is a fragment, the application data 1610 unit reassembly procedure described in Section 5.9 MUST be followed. 1611 If this procedure results in reassembly of the entire original 1612 application data unit, processing of the fragmentary bundle whose 1613 payload has been replaced by the reassembled application data unit 1614 (whether this bundle or a previously received fragment) proceeds 1615 from Step 2; otherwise, the retention constraint "Reassembly 1616 pending" MUST be added to the bundle and all remaining steps of this 1617 procedure MUST be skipped. 1619 Step 2: Delivery depends on the state of the registration whose 1620 endpoint ID matches that of the destination of the bundle: 1622 . An additional implementation-specific delivery deferral 1623 procedure MAY optionally be associated with the registration. 1624 . If the registration is in the Active state, then the bundle 1625 MUST be delivered automatically as soon as it is the next 1626 bundle that is due for delivery according to the BPA's bundle 1627 delivery scheduling policy, an implementation matter. 1628 . If the registration is in the Passive state, or if delivery of 1629 the bundle fails for some implementation-specific reason, then 1630 the registration's delivery failure action MUST be taken. 1631 Delivery failure action MUST be one of the following: 1633 o defer delivery of the bundle subject to this registration 1634 until (a) this bundle is the least recently received of 1635 all bundles currently deliverable subject to this 1636 registration and (b) either the registration is polled or 1637 else the registration is in the Active state, and also 1638 perform any additional delivery deferral procedure 1639 associated with the registration; or 1641 o abandon delivery of the bundle subject to this registration 1642 (as defined in 3.1. ). 1644 Step 3: As soon as the bundle has been delivered, if the "request 1645 reporting of bundle delivery" flag in the bundle's status report 1646 request field is set to 1 and bundle status reporting is enabled, 1647 then a bundle delivery status report SHOULD be generated, destined 1648 for the bundle's report-to endpoint ID. Note that this status report 1649 only states that the payload has been delivered to the application 1650 agent, not that the application agent has processed that payload. 1652 5.8. Bundle Fragmentation 1654 It may at times be advantageous for bundle protocol agents to reduce 1655 the sizes of bundles in order to forward them. This might be the 1656 case, for example, if a node to which a bundle is to be forwarded is 1657 accessible only via intermittent contacts and no upcoming contact is 1658 long enough to enable the forwarding of the entire bundle. 1660 The size of a bundle can be reduced by "fragmenting" the bundle. To 1661 fragment a bundle whose payload is of size M is to replace it with 1662 two "fragments" - new bundles with the same source node ID and 1663 creation timestamp as the original bundle - whose payloads MUST be 1664 the first N and the last (M - N) bytes of the original bundle's 1665 payload, where 0 < N < M. 1667 Note that fragments are bundles and therefore may themselves be 1668 fragmented, so multiple episodes of fragmentation may in effect 1669 replace the original bundle with more than two fragments. (However, 1670 there is only one 'level' of fragmentation, as in IP fragmentation.) 1672 Any bundle whose primary block's bundle processing flags do NOT 1673 indicate that it must not be fragmented MAY be fragmented at any 1674 time, for any purpose, at the discretion of the bundle protocol 1675 agent. NOTE, however, that some combinations of bundle 1676 fragmentation, replication, and routing might result in unexpected 1677 traffic patterns. 1679 Fragmentation SHALL be constrained as follows: 1681 . The concatenation of the payloads of all fragments produced by 1682 fragmentation MUST always be identical to the payload of the 1683 fragmented bundle (that is, the bundle that is being 1684 fragmented). Note that the payloads of fragments resulting from 1685 different fragmentation episodes, in different parts of the 1686 network, may be overlapping subsets of the fragmented bundle's 1687 payload. 1688 . The primary block of each fragment MUST differ from that of the 1689 fragmented bundle, in that the bundle processing flags of the 1690 fragment MUST indicate that the bundle is a fragment and both 1691 fragment offset and total application data unit length must be 1692 provided. Additionally, the CRC of the primary block of the 1693 fragmented bundle, if any, MUST be replaced in each fragment by 1694 a new CRC computed for the primary block of that fragment. 1695 . The payload blocks of fragments will differ from that of the 1696 fragmented bundle as noted above. 1697 . If the fragmented bundle is not a fragment or is the fragment 1698 with offset zero, then all extension blocks of the fragmented 1699 bundle MUST be replicated in the fragment whose offset is zero. 1700 . Each of the fragmented bundle's extension blocks whose "Block 1701 must be replicated in every fragment" flag is set to 1 MUST be 1702 replicated in every fragment. 1703 . Beyond these rules, rules for the replication of extension 1704 blocks in the fragments must be defined in the specifications 1705 for those extension block types. 1707 5.9. Application Data Unit Reassembly 1709 Note that the bundle fragmentation procedure described in 5.8 above 1710 may result in the replacement of a single original bundle with an 1711 arbitrarily large number of fragmentary bundles. In order to be 1712 delivered at a destination node, the original bundle's payload must 1713 be reassembled from the payloads of those fragments. 1715 The "material extents" of a received fragment's payload are all 1716 continuous sequences of bytes in that payload that do not overlap 1717 with the material extents of the payloads of any previously received 1718 fragments with the same source node ID and creation timestamp. If 1719 the concatenation - as informed by fragment offsets and payload 1720 lengths - of the material extents of the payloads of this fragment 1721 and all previously received fragments with the same source node ID 1722 and creation timestamp as this fragment forms a continuous byte 1723 array whose length is equal to the total application data unit 1724 length noted in the fragment's primary block, then: 1726 . This byte array -- the reassembled application data unit -- 1727 MUST replace the payload of that fragment whose material 1728 extents include the extent at offset zero. Note that this will 1729 enable delivery of the reconstituted original bundle as 1730 described in Step 1 of 5.7. 1731 . The "Reassembly pending" retention constraint MUST be removed 1732 from every other fragment with the same source node ID and 1733 creation timestamp as this fragment. 1735 Note: reassembly of application data units from fragments occurs at 1736 the nodes that are members of destination endpoints as necessary; an 1737 application data unit MAY also be reassembled at some other node on 1738 the path to the destination. 1740 5.10. Bundle Deletion 1742 The steps in deleting a bundle are: 1744 Step 1: If the "request reporting of bundle deletion" flag in the 1745 bundle's status report request field is set to 1, and if status 1746 reporting is enabled, then a bundle deletion status report citing 1747 the reason for deletion SHOULD be generated, destined for the 1748 bundle's report-to endpoint ID. 1750 Step 2: All of the bundle's retention constraints MUST be removed. 1752 5.11. Discarding a Bundle 1754 As soon as a bundle has no remaining retention constraints it MAY be 1755 discarded, thereby releasing any persistent storage that may have 1756 been allocated to it. 1758 5.12. Canceling a Transmission 1760 When requested to cancel a specified transmission, where the bundle 1761 created upon initiation of the indicated transmission has not yet 1762 been discarded, the bundle protocol agent MUST delete that bundle 1763 for the reason "transmission cancelled". For this purpose, the 1764 procedure defined in Section 5.10 MUST be followed. 1766 6. Administrative Record Processing 1768 6.1. Administrative Records 1770 Administrative records are standard application data units that are 1771 used in providing some of the features of the Bundle Protocol. One 1772 type of administrative record has been defined to date: bundle 1773 status reports. Note that additional types of administrative 1774 records may be defined by supplementary DTN protocol specification 1775 documents. 1777 Every administrative record consists of: 1779 . Record type code (an unsigned integer for which valid values 1780 are as defined below). 1781 . Record content in type-specific format. 1783 Valid administrative record type codes are defined as follows: 1785 +---------+--------------------------------------------+ 1787 | Value | Meaning | 1789 +=========+============================================+ 1791 | 1 | Bundle status report. | 1793 +---------+--------------------------------------------+ 1795 | (other) | Reserved for future use. | 1797 +---------+--------------------------------------------+ 1799 Figure 3: Administrative Record Type Codes 1801 Each BP administrative record SHALL be represented as a CBOR array 1802 comprising two items. 1804 The first item of the array SHALL be a record type code, which SHALL 1805 be represented as a CBOR unsigned integer. 1807 The second element of this array SHALL be the applicable CBOR 1808 representation of the content of the record. Details of the CBOR 1809 representation of administrative record type 1 are provided below. 1810 Details of the CBOR representation of other types of administrative 1811 record type are included in the specifications defining those 1812 records. 1814 6.1.1. Bundle Status Reports 1816 The transmission of "bundle status reports" under specified 1817 conditions is an option that can be invoked when transmission of a 1818 bundle is requested. These reports are intended to provide 1819 information about how bundles are progressing through the system, 1820 including notices of receipt, forwarding, final delivery, and 1821 deletion. They are transmitted to the Report-to endpoints of 1822 bundles. 1824 Each bundle status report SHALL be represented as a CBOR array. The 1825 number of elements in the array SHALL be either 6 (if the subject 1826 bundle is a fragment) or 4 (otherwise). 1828 The first item of the bundle status report array SHALL be bundle 1829 status information represented as a CBOR array of at least 4 1830 elements. The first four items of the bundle status information 1831 array shall provide information on the following four status 1832 assertions, in this order: 1834 . Reporting node received bundle. 1835 . Reporting node forwarded the bundle. 1836 . Reporting node delivered the bundle. 1837 . Reporting node deleted the bundle. 1839 Each item of the bundle status information array SHALL be a bundle 1840 status item represented as a CBOR array; the number of elements in 1841 each such array SHALL be either 2 (if the value of the first item of 1842 this bundle status item is 1 AND the "Report status time" flag was 1843 set to 1 in the bundle processing flags of the bundle whose status 1844 is being reported) or 1 (otherwise). The first item of the bundle 1845 status item array SHALL be a status indicator, a Boolean value 1846 indicating whether or not the corresponding bundle status is 1847 asserted, represented as a CBOR Boolean value. The second item of 1848 the bundle status item array, if present, SHALL indicate the time 1849 (as reported by the local system clock, an implementation matter) at 1850 which the indicated status was asserted for this bundle, represented 1851 as a DTN time as described in Section 4.2.6. above. 1853 The second item of the bundle status report array SHALL be the 1854 bundle status report reason code explaining the value of the status 1855 indicator, represented as a CBOR unsigned integer. Valid status 1856 report reason codes are registered in the IANA Bundle Status Report 1857 Reason Codes registry in the Bundle Protocol Namespace (see 10.5 1858 below). The initial contents of that registry are listed in Figure 1859 4 below but the list of status report reason codes provided here is 1860 neither exhaustive nor exclusive; supplementary DTN protocol 1861 specifications (including, but not restricted to, the Bundle 1862 Security Protocol [BPSEC]) may define additional reason codes. 1864 +---------+--------------------------------------------+ 1866 | Value | Meaning | 1868 +=========+============================================+ 1870 | 0 | No additional information. | 1871 +---------+--------------------------------------------+ 1873 | 1 | Lifetime expired. | 1875 +---------+--------------------------------------------+ 1877 | 2 | Forwarded over unidirectional link. | 1879 +---------+--------------------------------------------+ 1881 | 3 | Transmission canceled. | 1883 +---------+--------------------------------------------+ 1885 | 4 | Depleted storage. | 1887 +---------+--------------------------------------------+ 1889 | 5 | Destination endpoint ID unavailable. | 1891 +---------+--------------------------------------------+ 1893 | 6 | No known route to destination from here. | 1895 +---------+--------------------------------------------+ 1897 | 7 | No timely contact with next node on route. | 1899 +---------+--------------------------------------------+ 1901 | 8 | Block unintelligible. | 1903 +---------+--------------------------------------------+ 1905 | 9 | Hop limit exceeded. | 1907 +---------+--------------------------------------------+ 1909 | 10 | Traffic pared (e.g., status reports). | 1911 +---------+--------------------------------------------+ 1913 | (other) | Reserved for future use. | 1915 +---------+--------------------------------------------+ 1917 Figure 4: Status Report Reason Codes 1919 The third item of the bundle status report array SHALL be the source 1920 node ID identifying the source of the bundle whose status is being 1921 reported, represented as described in Section 4.2.5.1.1. above. 1923 The fourth item of the bundle status report array SHALL be the 1924 creation timestamp of the bundle whose status is being reported, 1925 represented as described in Section 4.2.7. above. 1927 The fifth item of the bundle status report array SHALL be present if 1928 and only if the bundle whose status is being reported contained a 1929 fragment offset. If present, it SHALL be the subject bundle's 1930 fragment offset represented as a CBOR unsigned integer item. 1932 The sixth item of the bundle status report array SHALL be present if 1933 and only if the bundle whose status is being reported contained a 1934 fragment offset. If present, it SHALL be the length of the subject 1935 bundle's payload represented as a CBOR unsigned integer item. 1937 Note that the forwarding parameters (such as lifetime, applicable 1938 security measures, etc.) of the bundle whose status is being 1939 reported MAY be reflected in the parameters governing the forwarding 1940 of the bundle that conveys a status report, but this is an 1941 implementation matter. Bundle protocol deployment experience to 1942 date has not been sufficient to suggest any clear guidance on this 1943 topic. 1945 6.2. Generation of Administrative Records 1947 Whenever the application agent's administrative element is directed 1948 by the bundle protocol agent to generate an administrative record, 1949 the following procedure must be followed: 1951 Step 1: The administrative record must be constructed. If the 1952 administrative record references a bundle and the referenced bundle 1953 is a fragment, the administrative record MUST contain the fragment 1954 offset and fragment length. 1956 Step 2: A request for transmission of a bundle whose payload is this 1957 administrative record MUST be presented to the bundle protocol 1958 agent. 1960 7. Services Required of the Convergence Layer 1962 7.1. The Convergence Layer 1964 The successful operation of the end-to-end bundle protocol depends 1965 on the operation of underlying protocols at what is termed the 1966 "convergence layer"; these protocols accomplish communication 1967 between nodes. A wide variety of protocols may serve this purpose, 1968 so long as each convergence layer protocol adapter provides a 1969 defined minimal set of services to the bundle protocol agent. This 1970 convergence layer service specification enumerates those services. 1972 7.2. Summary of Convergence Layer Services 1974 Each convergence layer protocol adapter is expected to provide the 1975 following services to the bundle protocol agent: 1977 . sending a bundle to a bundle node that is reachable via the 1978 convergence layer protocol; 1979 . notifying the bundle protocol agent of the disposition of its 1980 data sending procedures with regard to a bundle, upon 1981 concluding those procedures; 1982 . delivering to the bundle protocol agent a bundle that was sent 1983 by a bundle node via the convergence layer protocol. 1985 The convergence layer service interface specified here is neither 1986 exhaustive nor exclusive. That is, supplementary DTN protocol 1987 specifications (including, but not restricted to, the Bundle 1988 Security Protocol [BPSEC]) may expect convergence layer adapters 1989 that serve BP implementations conforming to those protocols to 1990 provide additional services such as reporting on the transmission 1991 and/or reception progress of individual bundles (at completion 1992 and/or incrementally), retransmitting data that were lost in 1993 transit, discarding bundle-conveying data units that the convergence 1994 layer protocol determines are corrupt or inauthentic, or reporting 1995 on the integrity and/or authenticity of delivered bundles. 1997 In addition, bundle protocol relies on the capabilities of protocols 1998 at the convergence layer to minimize congestion in the store-carry- 1999 forward overlay network. The potentially long round-trip times 2000 characterizing delay-tolerant networks are incompatible with end-to- 2001 end reactive congestion control mechanisms, so convergence-layer 2002 protocols MUST provide rate limiting or congestion control. 2004 8. Implementation Status 2006 [NOTE to the RFC Editor: please remove this section before 2007 publication, as well as the reference to RFC 7942.] 2009 This section records the status of known implementations of the 2010 protocol defined by this specification at the time of posting of 2011 this Internet-Draft, and is based on a proposal described in RFC 2012 7942. The description of implementations in this section is 2013 intended to assist the IETF in its decision processes in progressing 2014 drafts to RFCs. Please note that the listing of any individual 2015 implementation here does not imply endorsement by the IETF. 2016 Furthermore, no effort has been spent to verify the information 2017 presented here that was supplied by IETF contributors. This is not 2018 intended as, and must not be construed to be, a catalog of available 2019 implementations or their features. Readers are advised to note that 2020 other implementations may exist. 2022 According to RFC 7942, "this will allow reviewers and working groups 2023 to assign due consideration to documents that have the benefit of 2024 running code, which may serve as evidence of valuable 2025 experimentation and feedback that have made the implemented 2026 protocols more mature. It is up to the individual working groups to 2027 use this information as they see fit". 2029 At the time of this writing, there are six known implementations of 2030 the current document. 2032 The first known implementation is microPCN (https://upcn.eu/). 2033 According to the developers: 2035 The Micro Planetary Communication Network (uPCN) is a free 2036 software project intended to offer an implementation of Delay- 2037 tolerant Networking protocols for POSIX operating systems (well, 2038 and for Linux) plus for the ARM Cortex STM32F4 microcontroller 2039 series. More precisely it currently provides an implementation of 2041 . the Bundle Protocol (BP, RFC 5050), 2042 . version 6 of the Bundle Protocol version 7 specification 2043 draft, 2044 . the DTN IP Neighbor Discovery (IPND) protocol, and 2045 . a routing approach optimized for message-ferry micro LEO 2046 satellites. 2048 uPCN is written in C and is built upon the real-time operating 2049 system FreeRTOS. The source code of uPCN is released under the 2050 "BSD 3-Clause License". 2052 The project depends on an execution environment offering link 2053 layer protocols such as AX.25. The source code uses the USB 2054 subsystem to interact with the environment. 2056 The second known implementation is PyDTN, developed by X-works, 2057 s.r.o (https://x-works.sk/). The final third of the implementation 2058 was developed during the IETF 101 Hackathon. According to the 2059 developers, PyDTN implements bundle coding/decoding and neighbor 2060 discovery. PyDTN is written in Python and has been shown to be 2061 interoperable with uPCN. 2063 The third known implementation is "Terra" 2064 (https://github.com/RightMesh/Terra/), a Java implementation 2065 developed in the context of terrestrial DTN. It includes an 2066 implementation of a "minimal TCP" convergence layer adapter. 2068 The fourth and fifth known implementations are products of 2069 cooperating groups at two German universities: 2071 . An implementation written in Go, licensed under GPLv3, is 2072 focused on being easily extensible suitable for research. It 2073 is maintained at the University of Marburg and can be accessed 2074 from https://github.com/dtn7/dtn7-go. 2075 . An implementation written in Rust, licensed under the 2076 MIT/Apache license, is intended for environments with limited 2077 resources or demanding safety and/or performance requirements. 2078 It is maintained at the Technical University of Darmstadt and 2079 can be accessed at https://github.com/dtn7/dtn7-rs/. 2081 The sixth known implementation is the "bpv7" module in version 4.0.0 2082 of the Interplanetary Overlay Network (ION) software maintained at 2083 the Jet Propulsion Laboratory, California Institute of Technology, 2084 for the U.S. National Aeronautics and Space Administration (NASA). 2086 9. Security Considerations 2088 The bundle protocol security architecture and the available security 2089 services are specified in an accompanying document, the Bundle 2090 Security Protocol (BPsec) specification [BPSEC]. Whenever Bundle 2091 Protocol security services (as opposed to the security services 2092 provided by overlying application protocols or underlying 2093 convergence-layer protocols) are required, those services SHALL be 2094 provided by BPsec rather than by some other mechanism with the same 2095 or similar scope. 2097 A Bundle Protocol Agent (BPA) which sources, cryptographically 2098 verifies, and/or accepts a bundle MUST implement support for BPsec. 2099 Use of BPsec for a particular Bundle Protocol session is optional. 2101 The BPsec extensions to Bundle Protocol enable each block of a 2102 bundle (other than a BPsec extension block) to be individually 2103 authenticated by a signature block (Block Integrity Block, or BIB) 2104 and also enable each block of a bundle other than the primary block 2105 (and the BPsec extension blocks themselves) to be individually 2106 encrypted by a Block Confidentiality Block (BCB). 2108 Because the security mechanisms are extension blocks that are 2109 themselves inserted into the bundle, the protections they afford 2110 apply while the bundle is at rest, awaiting transmission at the next 2111 forwarding opportunity, as well as in transit. 2113 Additionally, convergence-layer protocols that ensure authenticity 2114 of communication between adjacent nodes in BP network topology 2115 SHOULD be used where available, to minimize the ability of 2116 unauthenticated nodes to introduce inauthentic traffic into the 2117 network. Convergence-layer protocols that ensure confidentiality of 2118 communication between adjacent nodes in BP network topology SHOULD 2119 also be used where available, to minimize exposure of the bundle's 2120 primary block and other clear-text blocks, thereby offering some 2121 defense against traffic analysis. 2123 In order to provide authenticity and/or confidentiality of 2124 communication between BP nodes, the convergence-layer protocol 2125 requires as input the name(s) of the expected communication peer(s). 2126 These must be supplied by the convergence-layer adapter. Details of 2127 the means by which the CLA determines which CL endpoint name(s) must 2128 be provided to the CL protocol are out of scope for this 2129 specification. Note, though, that when the CL endpoint names are a 2130 function of BP endpoint IDs, the correctness and authenticity of 2131 that mapping will be vital to the overall security properties that 2132 the CL provides to the system. 2134 Note that, while the primary block must remain in the clear for 2135 routing purposes, the Bundle Protocol could be protected against 2136 traffic analysis to some extent by using bundle-in-bundle 2137 encapsulation [BIBE] to tunnel bundles to a safe forward 2138 distribution point: the encapsulated bundle could form the payload 2139 of an encapsulating bundle, and that payload block could be 2140 encrypted by a BCB. 2142 Note that the generation of bundle status reports is disabled by 2143 default because malicious initiation of bundle status reporting 2144 could result in the transmission of extremely large numbers of 2145 bundles, effecting a denial of service attack. Imposing bundle 2146 lifetime overrides would constitute one defense against such an 2147 attack. 2149 Note also that the reception of large numbers of fragmentary bundles 2150 with very long lifetimes could constitute a denial of service 2151 attack, occupying storage while pending reassembly that will never 2152 occur. Imposing bundle lifetime overrides would, again, constitute 2153 one defense against such an attack. 2155 This protocol makes use of absolute timestamps for several purposes. 2156 Provisions are included for nodes without accurate clocks to retain 2157 most of the protocol functionality, but nodes that are unaware that 2158 their clock is inaccurate may exhibit unexpected behavior. 2160 10. IANA Considerations 2162 The Bundle Protocol includes fields requiring registries managed by 2163 IANA. 2165 10.1. Bundle Block Types 2167 The current Bundle Block Types registry in the Bundle Protocol 2168 Namespace is augmented by adding a column identifying the version of 2169 the Bundle protocol (Bundle Protocol Version) that applies to the 2170 new values. IANA is requested to add the following values, as 2171 described in section 4.3.1, to the Bundle Block Types registry. The 2172 current values in the Bundle Block Types registry should have the 2173 Bundle Protocol Version set to the value "6", as shown below. 2175 +----------+-------+-----------------------------+---------------+ 2177 | Bundle | Value | Description | Reference | 2179 | Protocol | | | | 2181 | Version | | | | 2183 +----------+-------+-----------------------------+---------------+ 2185 | none | 0 | Reserved | [RFC6255] | 2187 | 6,7 | 1 | Bundle Payload Block | [RFC5050] | 2189 | | | | RFC-to-be | 2191 | 6 | 2 | Bundle Authentication Block | [RFC6257] | 2193 | 6 | 3 | Payload Integrity Block | [RFC6257] | 2195 | 6 | 4 | Payload Confidentiality | [RFC6257] | 2197 | | | Block | | 2199 | 6 | 5 | Previous-Hop Insertion Block| [RFC6259] | 2201 | 7 | 6 | Previous node (proximate | RFC-to-be | 2202 | | | sender) | | 2204 | 7 | 7 | Bundle age (in milliseconds)| RFC-to-be | 2206 | 6 | 8 | Metadata Extension Block | [RFC6258] | 2208 | 6 | 9 | Extension Security Block | [RFC6257] | 2210 | 7 | 10 | Hop count (#prior xmit | RFC-to-be | 2212 | | | attempts) | | 2214 | 7 | 11-191| Unassigned | | 2216 | 6,7 |192-255| Reserved for Private and/or | [RFC5050], | 2218 | | | Experimental Use | RFC-to-be | 2220 +----------+-------+-----------------------------+---------------+ 2222 10.2. Primary Bundle Protocol Version 2224 IANA is requested to add the following value to the Primary Bundle 2225 Protocol Version registry in the Bundle Protocol Namespace. 2227 +-------+-------------+---------------+ 2229 | Value | Description | Reference | 2231 +-------+-------------+---------------+ 2233 | 7 | Assigned | RFC-to-be | 2235 +-------+-------------+---------------+ 2237 Values 8-255 (rather than 7-255) are now Unassigned. 2239 10.3. Bundle Processing Control Flags 2241 The current Bundle Processing Control Flags registry in the Bundle 2242 Protocol Namespace is augmented by adding a column identifying the 2243 version of the Bundle protocol (Bundle Protocol Version) that 2244 applies to the new values. IANA is requested to add the following 2245 values, as described in section 4.1.3, to the Bundle Processing 2246 Control Flags registry. The current values in the Bundle Processing 2247 Control Flags registry should have the Bundle Protocol Version set 2248 to the value 6 or "6, 7", as shown below. 2250 Bundle Processing Control Flags Registry 2252 +--------------------+----------------------------------+----------+ 2254 | Bundle | Bit | Description | Reference| 2256 | Protocol| Position | | | 2258 | Version | (right | | | 2260 | | to left) | | | 2262 +--------------------+----------------------------------+----------+ 2264 | 6,7 | 0 | Bundle is a fragment |[RFC5050],| 2266 | | | |RFC-to-be | 2268 | 6,7 | 1 | Application data unit is an |[RFC5050],| 2270 | | | administrative record |RFC-to-be | 2272 | 6,7 | 2 | Bundle must not be fragmented |[RFC5050],| 2274 | | | |RFC-to-be | 2276 | 6 | 3 | Custody transfer is requested |[RFC5050] | 2278 | 6 | 4 | Destination endpoint is singleton|[RFC5050] | 2280 | 6,7 | 5 | Acknowledgement by application |[RFC5050],| 2282 | | | is requested |RFC-to-be | 2284 | 7 | 6 | Status time requested in reports |RFC-to-be | 2286 | 6 | 7 | Class of service, priority |[RFC5050] | 2288 | 6 | 8 | Class of service, priority |[RFC5050] | 2290 | 6 | 9 | Class of service, reserved |[RFC5050] | 2292 | 6 | 10 | Class of service, reserved |[RFC5050] | 2294 | 6 | 11 | Class of service, reserved |[RFC5050] | 2296 | 6 | 12 | Class of service, reserved |[RFC5050] | 2297 | 6 | 13 | Class of service, reserved |[RFC5050] | 2299 | 6,7 | 14 | Request reporting of bundle |[RFC5050],| 2301 | | | reception |RFC-to-be | 2303 | 6,7 | 16 | Request reporting of bundle |[RFC5050],| 2305 | | | forwarding |RFC-to-be | 2307 | 6,7 | 17 | Request reporting of bundle |[RFC5050],| 2309 | | | delivery |RFC-to-be | 2311 | 6,7 | 18 | Request reporting of bundle |[RFC5050],| 2313 | | | deletion |RFC-to-be | 2315 | 6,7 | 19 | Reserved |[RFC5050],| 2317 | | | |RFC-to-be | 2319 | 6,7 | 20 | Reserved |[RFC5050],| 2321 | | | |RFC-to-be | 2323 | | 21-63 | Unassigned | | 2325 +--------------------+----------------------------------+----------+ 2327 10.4. Block Processing Control Flags 2329 The current Block Processing Control Flags registry in the Bundle 2330 Protocol Namespace is augmented by adding a column identifying the 2331 version of the Bundle protocol (Bundle Protocol Version) that 2332 applies to the related BP version. The current values in the Block 2333 Processing Control Flags registry should have the Bundle Protocol 2334 Version set to the value 6 or "6, 7", as shown below. 2336 Block Processing Control Flags Registry 2338 +--------------------+----------------------------------+----------+ 2340 | Bundle | Bit | Description | Reference| 2342 | Protocol| Position | | | 2343 | Version | (right | | | 2345 | | to left) | | | 2347 +--------------------+----------------------------------+----------+ 2349 | 6,7 | 0 | Block must be replicated in |[RFC5050],| 2351 | | | every fragment |RFC-to-be | 2353 | 6,7 | 1 | Transmit status report if block |[RFC5050],| 2355 | | | can't be processed |RFC-to-be | 2357 | 6,7 | 2 | Delete bundle if block can't be |[RFC5050],| 2359 | | | processed |RFC-to-be | 2361 | 6 | 3 | Last block |[RFC5050] | 2363 | 6,7 | 4 | Discard block if it can't be |[RFC5050],| 2365 | | | processed |RFC-to-be | 2367 | 6 | 5 | Block was forwarded without |[RFC5050] | 2369 | | | being processed | | 2371 | 6 | 6 | Block contains an EID reference |[RFC5050] | 2373 | | | field | | 2375 | | 7-63 | Unassigned | | 2377 +--------------------+----------------------------------+----------+ 2379 10.5. Bundle Status Report Reason Codes 2381 The current Bundle Status Report Reason Codes registry in the Bundle 2382 Protocol Namespace is augmented by adding a column identifying the 2383 version of the Bundle protocol (Bundle Protocol Version) that 2384 applies to the new values. IANA is requested to add the following 2385 values, as described in section 6.1.1, to the Bundle Status Report 2386 Reason Codes registry. The current values in the Bundle Status 2387 Report Reason Codes registry should have the Bundle Protocol Version 2388 set to the value 6 or 7 or "6, 7", as shown below. 2390 Bundle Status Report Reason Codes Registry 2392 +--------------------+----------------------------------+----------+ 2394 | Bundle | Value | Description | Reference| 2396 | Protocol| | | | 2398 | Version | | | | 2400 | | | | | 2402 +--------------------+----------------------------------+----------+ 2404 | 6,7 | 0 | No additional information |[RFC5050],| 2406 | | | |RFC-to-be | 2408 | 6,7 | 1 | Lifetime expired |[RFC5050],| 2410 | | | |RFC-to-be | 2412 | 6,7 | 2 | Forwarded over unidirectional |[RFC5050],| 2414 | | | link |RFC-to-be | 2416 | 6,7 | 3 | Transmission canceled |[RFC5050],| 2418 | | | |RFC-to-be | 2420 | 6,7 | 4 | Depleted storage |[RFC5050],| 2422 | | | |RFC-to-be | 2424 | 6,7 | 5 | Destination endpoint ID |[RFC5050],| 2426 | | | unavailable |RFC-to-be | 2428 | 6,7 | 6 | No known route to destination |[RFC5050],| 2430 | | | from here |RFC-to-be | 2432 | 6,7 | 7 | No timely contact with next node |[RFC5050],| 2434 | | | on route |RFC-to-be | 2436 | 6,7 | 8 | Block unintelligible |[RFC5050],| 2437 | | | |RFC-to-be | 2439 | 7 | 9 | Hop limit exceeded |RFC-to-be | 2441 | 7 | 10 | Traffic pared |RFC-to-be | 2443 | 7 | 11 | Block unsupported |RFC-to-be | 2445 | | 12-254 | Unassigned | | 2447 | 6,7 | 255 | Reserved |[RFC6255],| 2449 | | | |RFC-to-be | 2451 +-------+-----------------------------------------------+----------+ 2453 10.6. Bundle Protocol URI scheme types 2455 The Bundle Protocol has a URI scheme type field - an unsigned 2456 integer of indefinite length - for which IANA is requested to create 2457 and maintain a new "Bundle Protocol URI Scheme Type" registry in the 2458 Bundle Protocol Namespace. The "Bundle Protocol URI Scheme Type" 2459 registry governs an unsigned integer namespace. Initial values for 2460 the Bundle Protocol URI Scheme Type registry are given below. 2462 The registration policy for this registry is: Standards Action. The 2463 allocation should only be granted for a standards-track RFC approved 2464 by the IESG. 2466 The value range is: unsigned integer. 2468 Each assignment consists of a URI scheme type name and its 2469 associated description, a reference to the document that defines the 2470 URI scheme, and a reference to the document that defines the use of 2471 this URI scheme in BP endpoint IDs (including the CBOR 2472 representation of those endpoint IDs in transmitted bundles). 2474 Bundle Protocol URI Scheme Type Registry 2476 +---------+-------------+----------------+------------------+ 2478 | | | BP Utilization | URI Definition | 2480 | Value | Description | Reference | Reference | 2482 +---------+-------------+----------------+------------------+ 2483 | 0 | Reserved | n/a | | 2485 | 1 | dtn | RFC-to-be | RFC-to-be | 2487 | 2 | ipn | RFC-to-be | [RFC6260], | 2489 | | | | RFC-to-be | 2491 | 3-254 | Unassigned | n/a | | 2493 |255-65535| reserved | n/a | | 2495 | >65535 | open for | n/a | | 2497 | | private use | n/a | | 2499 +---------+-------------+----------------+------------------+ 2501 10.7. URI scheme "dtn" 2503 In the Uniform Resource Identifier (URI) Schemes (uri-schemes) 2504 registry, IANA is requested to update the registration of the URI 2505 scheme with the string "dtn" as the scheme name, as follows: 2507 URI scheme name: "dtn" 2509 Status: permanent 2511 Applications and/or protocols that use this URI scheme name: the 2512 Delay-Tolerant Networking (DTN) Bundle Protocol (BP). 2514 Contact: 2516 Scott Burleigh 2518 Jet Propulsion Laboratory, 2520 California Institute of Technology 2522 scott.c.burleigh@jpl.nasa.gov 2524 +1 (800) 393-3353 2526 Change controller: 2528 IETF, iesg@ietf.org 2530 10.8. URI scheme "ipn" 2532 In the Uniform Resource Identifier (URI) Schemes (uri-schemes) 2533 registry, IANA is requested to update the registration of the URI 2534 scheme with the string "ipn" as the scheme name, originally 2535 documented in RFC 6260 [RFC6260], as follows. 2537 URI scheme name: "ipn" 2539 Status: permanent 2541 Applications and/or protocols that use this URI scheme name: the 2542 Delay-Tolerant Networking (DTN) Bundle Protocol (BP). 2544 Contact: 2546 Scott Burleigh 2548 Jet Propulsion Laboratory, 2550 California Institute of Technology 2552 scott.c.burleigh@jpl.nasa.gov 2554 +1 (800) 393-3353 2556 Change controller: 2558 IETF, iesg@ietf.org 2560 11. References 2562 11.1. Normative References 2564 [BPSEC] Birrane, E., "Bundle Security Protocol Specification", 2565 draft-ietf-dtn-bpsec, January 2020. 2567 [CRC16] ITU-T Recommendation X.25, p. 9, section 2.2.7.4, 2568 International Telecommunications Union, October 1996. 2570 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2571 Requirement Levels", BCP 14, RFC 2119, March 1997. 2573 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 2574 4960, September 2007. 2576 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2577 Specifications: ABNF", STD 68, RFC 5234, January 2008. 2579 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2580 2119 Key Words", BCP 14, RFC 8174, May 2017. 2582 [RFC8949] Borman, C. and P. Hoffman, "Concise Binary Object 2583 Representation (CBOR)", RFC 8949, December 2020. 2585 [SABR] "Schedule-Aware Bundle Routing", CCSDS Recommended Standard 2586 734.3-B-1, Consultative Committee for Space Data Systems, July 2019. 2588 [TCPCL] Sipos, B., Demmer, M., Ott, J., and S. Perreault, "Delay- 2589 Tolerant Networking TCP Convergence Layer Protocol Version 4", 2590 draft-ietf-dtn-tcpclv4, January 2020. 2592 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 2593 Resource Identifier (URI): Generic Syntax", RFC 3986, STD 66, 2594 January 2005. 2596 [URIREG] Thaler, D., Hansen, T., and T. Hardie, "Guidelines and 2597 Registration Procedures for URI Schemes", RFC 7595, BCP 35, June 2598 2015. 2600 11.2. Informative References 2602 [ARCH] V. Cerf et al., "Delay-Tolerant Network Architecture", RFC 2603 4838, April 2007. 2605 [BIBE] Burleigh, S., "Bundle-in-Bundle Encapsulation", draft-ietf- 2606 dtn-bibect, August 2019. 2608 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 2609 Identifiers (IRIs)", RFC 3987, January 2005. 2611 [RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol 2612 Specification", RFC 5050, November 2007. 2614 [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol 2615 IANA Registries", RFC 6255, May 2011. 2617 [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, 2618 "Bundle Security Protocol Specification", RFC 6257, May 2011. 2620 [RFC6258] Symington, S., "Delay-Tolerant Networking Metadata 2621 Extension Block", RFC 6258, May 2011. 2623 [RFC6259] Symington, S., "Delay-Tolerant Networking Previous-Hop 2624 Insertion Block", RFC 6259, May 2011. 2626 [RFC6260] Burleigh, S., "Compressed Bundle Header Encoding (CBHE)", 2627 RFC 6260, May 2011. 2629 [RFC7143] Chadalapaka, M., Satran, J., Meth, K., and D. Black, 2630 "Internet Small Computer System Interface (iSCSI) Protocol 2631 (Consolidated)", RFC 7143, April 2014. 2633 [SIGC] Fall, K., "A Delay-Tolerant Network Architecture for 2634 Challenged Internets", SIGCOMM 2003. 2636 12. Acknowledgments 2638 This work is freely adapted from RFC 5050, which was an effort of 2639 the Delay Tolerant Networking Research Group. The following DTNRG 2640 participants contributed significant technical material and/or 2641 inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh, 2642 Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory, 2643 Michael Demmer of the University of California at Berkeley, Robert 2644 Durst, Keith Scott, and Susan Symington of The MITRE Corporation, 2645 Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity 2646 College Dublin, Howard Weiss and Peter Lovell of SPARTA, Inc., and 2647 Manikantan Ramadas of Ohio University. 2649 This document was prepared using 2-Word-v2.0.template.dot. 2651 13. Significant Changes from RFC 5050 2653 Points on which this draft significantly differs from RFC 5050 2654 include the following: 2656 . Clarify the difference between transmission and forwarding. 2657 . Migrate custody transfer to the bundle-in-bundle encapsulation 2658 specification [BIBE]. 2659 . Introduce the concept of "node ID" as functionally distinct 2660 from endpoint ID, while having the same syntax. 2661 . Restructure primary block, making it immutable. Add optional 2662 CRC. 2663 . Add optional CRCs to non-primary blocks. 2664 . Add block ID number to canonical block format (to support 2665 BPsec). 2666 . Add definition of bundle age extension block. 2667 . Add definition of previous node extension block. 2668 . Add definition of hop count extension block. 2669 . Remove Quality of Service markings. 2671 . Change from SDNVs to CBOR representation. 2672 . Add lifetime overrides. 2674 Appendix A. For More Information 2676 Copyright (c) 2020 IETF Trust and the persons identified as authors 2677 of the code. All rights reserved. 2679 Redistribution and use in source and binary forms, with or without 2680 modification, is permitted pursuant to, and subject to the license 2681 terms contained in, the Simplified BSD License set forth in Section 2682 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 2683 (http://trustee.ietf.org/license-info). 2685 Appendix B. CDDL expression 2687 For informational purposes, Carsten Bormann and Brian Sipos have 2688 kindly provided an expression of the Bundle Protocol specification 2689 in the Concise Data Definition Language (CDDL). That CDDL 2690 expression is presented below. Note that wherever the CDDL 2691 expression is in disagreement with the textual representation of the 2692 BP specification presented in the earlier sections of this document, 2693 the textual representation rules. 2695 start = bundle / #6.55799(bundle) 2697 ; Times before 2000 are invalid 2699 dtn-time = uint 2701 ; CRC enumerated type 2703 crc-type = &( 2705 crc-none: 0, 2707 crc-16bit: 1, 2709 crc-32bit: 2 2711 ) 2713 ; Either 16-bit or 32-bit 2715 crc-value = (bstr .size 2) / (bstr .size 4) 2717 creation-timestamp = [ 2719 dtn-time, ; absolute time of creation 2721 sequence: uint ; sequence within the time 2723 ] 2725 eid = $eid .within eid-structure 2727 eid-structure = [ 2729 uri-code: uint, 2730 SSP: any 2732 ] 2734 $eid /= [ 2736 uri-code: 1, 2738 SSP: (tstr / 0) 2740 ] 2742 $eid /= [ 2744 uri-code: 2, 2746 SSP: [ 2748 nodenum: uint, 2750 servicenum: uint 2752 ] 2754 ] 2756 ; The root bundle array 2758 bundle = [primary-block, *extension-block, payload-block] 2760 primary-block = [ 2762 version: 7, 2764 bundle-control-flags, 2766 crc-type, 2768 destination: eid, 2770 source-node: eid, 2772 report-to: eid, 2774 creation-timestamp, 2776 lifetime: uint, 2777 ? ( 2779 fragment-offset: uint, 2781 total-application-data-length: uint 2783 ), 2785 ? crc-value, 2787 ] 2789 bundle-control-flags = uint .bits bundleflagbits 2791 bundleflagbits = &( 2793 reserved: 21, 2795 reserved: 20, 2797 reserved: 19, 2799 bundle-deletion-status-reports-are-requested: 18, 2801 bundle-delivery-status-reports-are-requested: 17, 2803 bundle-forwarding-status-reports-are-requested: 16, 2805 reserved: 15, 2807 bundle-reception-status-reports-are-requested: 14, 2809 reserved: 13, 2811 reserved: 12, 2813 reserved: 11, 2815 reserved: 10, 2817 reserved: 9, 2819 reserved: 8, 2821 reserved: 7, 2822 status-time-is-requested-in-all-status-reports: 6, 2824 user-application-acknowledgement-is-requested: 5, 2826 reserved: 4, 2828 reserved: 3, 2830 bundle-must-not-be-fragmented: 2, 2832 payload-is-an-administrative-record: 1, 2834 bundle-is-a-fragment: 0 2836 ) 2838 ; Abstract shared structure of all non-primary blocks 2840 canonical-block-structure = [ 2842 block-type-code: uint, 2844 block-number: uint, 2846 block-control-flags, 2848 crc-type, 2850 ; Each block type defines the content within the bytestring 2852 block-type-specific-data, 2854 ? crc-value 2856 ] 2858 block-control-flags = uint .bits blockflagbits 2860 blockflagbits = &( 2862 reserved: 7, 2864 reserved: 6, 2866 reserved: 5, 2868 block-must-be-removed-from-bundle-if-it-cannot-be-processed: 4, 2869 reserved: 3, 2871 bundle-must-be-deleted-if-block-cannot-be-processed: 2, 2873 status-report-must-be-transmitted-if-block-cannot-be-processed: 1, 2875 block-must-be-replicated-in-every-fragment: 0 2877 ) 2879 block-type-specific-data = bstr / #6.24(bstr) 2881 ; Actual CBOR data embedded in a bytestring, with optional tag to 2882 indicate so 2884 embedded-cbor = (bstr .cbor Item) / #6.24(bstr .cbor Item) 2886 ; Extension block type, which does not specialize other than the 2887 code/number 2889 extension-block = $extension-block-structure .within canonical- 2890 block-structure 2892 ; Generic shared structure of all non-primary blocks 2894 extension-block-use = [ 2896 block-type-code: CodeValue, 2898 block-number: (uint .gt 1), 2900 block-control-flags, 2902 crc-type, 2904 BlockData, 2906 ? crc-value 2908 ] 2910 ; Payload block type 2912 payload-block = payload-block-structure .within canonical-block- 2913 structure 2914 payload-block-structure = [ 2916 block-type-code: 1, 2918 block-number: 1, 2920 block-control-flags, 2922 crc-type, 2924 $payload-block-data, 2926 ? crc-value 2928 ] 2930 ; Arbitrary payload data, including non-CBOR bytestring 2932 $payload-block-data /= block-type-specific-data 2934 ; Administrative record as a payload data specialization 2936 $payload-block-data /= embedded-cbor 2938 admin-record = $admin-record .within admin-record-structure 2940 admin-record-structure = [ 2942 record-type-code: uint, 2944 record-content: any 2946 ] 2948 ; Only one defined record type 2950 $admin-record /= [1, status-record-content] 2952 status-record-content = [ 2954 bundle-status-information, 2956 status-report-reason-code: uint, 2958 source-node-eid: eid, 2960 subject-creation-timestamp: creation-timestamp, 2961 ? ( 2963 subject-payload-offset: uint, 2965 subject-payload-length: uint 2967 ) 2969 ] 2971 bundle-status-information = [ 2973 reporting-node-received-bundle: status-info-content, 2975 reporting-node-forwarded-bundle: status-info-content, 2977 reporting-node-delivered-bundle: status-info-content, 2979 reporting-node-deleted-bundle: status-info-content 2981 ] 2983 status-info-content = [ 2985 status-indicator: bool, 2987 ? timestamp: dtn-time 2989 ] 2991 ; Previous Node extension block 2993 $extension-block-structure /= 2995 extension-block-use<6, embedded-cbor> 2997 ext-data-previous-node = eid 2999 ; Bundle Age extension block 3001 $extension-block-structure /= 3003 extension-block-use<7, embedded-cbor> 3005 ext-data-bundle-age = uint 3007 ; Hop Count extension block 3008 $extension-block-structure /= 3010 extension-block-use<10, embedded-cbor> 3012 ext-data-hop-count = [ 3014 hop-limit: uint, 3016 hop-count: uint 3018 ] 3020 Authors' Addresses 3022 Scott Burleigh 3023 Jet Propulsion Laboratory, California Institute of Technology 3024 4800 Oak Grove Dr. 3025 Pasadena, CA 91109-8099 3026 US 3027 Phone: +1 818 393 3353 3028 Email: Scott.C.Burleigh@jpl.nasa.gov 3030 Kevin Fall 3031 Roland Computing Services 3032 3871 Piedmont Ave. Suite 8 3033 Oakland, CA 94611 3034 US 3035 Email: kfall+rcs@kfall.com 3037 Edward J. Birrane 3038 Johns Hopkins University Applied Physics Laboratory 3039 11100 Johns Hopkins Rd 3040 Laurel, MD 20723 3041 US 3042 Phone: +1 443 778 7423 3043 Email: Edward.Birrane@jhuapl.edu