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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'CRC16' ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) ** Obsolete normative reference: RFC 7049 (Obsoleted by RFC 8949) -- Possible downref: Non-RFC (?) normative reference: ref. 'SBAR' -- Possible downref: Non-RFC (?) normative reference: ref. 'UTC' Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 4 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: August 10, 2020 Roland Computing Services 5 E. Birrane 6 APL, Johns Hopkins University 7 February 7, 2020 9 Bundle Protocol Version 7 10 draft-ietf-dtn-bpbis-23.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 August 10, 2020. 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.................................................12 67 4.1. BP Fundamental Data Structures...........................13 68 4.1.1. CRC Type............................................13 69 4.1.2. CRC.................................................14 70 4.1.3. Bundle Processing Control Flags.....................14 71 4.1.4. Block Processing Control Flags......................15 72 4.1.5. Identifiers.........................................16 73 4.1.5.1. Endpoint ID....................................16 74 4.1.5.2. Node ID........................................18 75 4.1.6. DTN Time............................................18 76 4.1.7. Creation Timestamp..................................18 77 4.1.8. Block-type-specific Data............................19 78 4.2. Bundle Representation....................................19 79 4.2.1. Bundle..............................................19 80 4.2.2. Primary Bundle Block................................19 81 4.2.3. Canonical Bundle Block Format.......................22 82 4.3. Extension Blocks.........................................23 83 4.3.1. Previous Node.......................................23 84 4.3.2. Bundle Age..........................................23 85 4.3.3. Hop Count...........................................24 86 5. Bundle Processing.............................................24 87 5.1. Generation of Administrative Records.....................25 88 5.2. Bundle Transmission......................................25 89 5.3. Bundle Dispatching.......................................26 90 5.4. Bundle Forwarding........................................26 91 5.4.1. Forwarding Contraindicated..........................28 92 5.4.2. Forwarding Failed...................................29 94 5.5. Bundle Expiration........................................29 95 5.6. Bundle Reception.........................................29 96 5.7. Local Bundle Delivery....................................30 97 5.8. Bundle Fragmentation.....................................31 98 5.9. Application Data Unit Reassembly.........................32 99 5.10. Bundle Deletion.........................................33 100 5.11. Discarding a Bundle.....................................33 101 5.12. Canceling a Transmission................................33 102 6. Administrative Record Processing..............................33 103 6.1. Administrative Records...................................33 104 6.1.1. Bundle Status Reports...............................34 105 6.2. Generation of Administrative Records.....................37 106 7. Services Required of the Convergence Layer....................38 107 7.1. The Convergence Layer....................................38 108 7.2. Summary of Convergence Layer Services....................38 109 8. Implementation Status.........................................39 110 9. Security Considerations.......................................40 111 10. IANA Considerations..........................................41 112 10.1. Bundle Block Types......................................41 113 10.2. Primary Bundle Protocol Version.........................42 114 10.3. Bundle Processing Control Flags.........................43 115 10.4. Block Processing Control Flags..........................45 116 10.5. Bundle Status Report Reason Codes.......................46 117 10.6. Bundle Protocol URI scheme types........................48 118 10.7. URI scheme "dtn"........................................49 119 10.8. URI scheme "ipn"........................................50 120 11. References...................................................52 121 11.1. Normative References....................................52 122 11.2. Informative References..................................53 123 12. Acknowledgments..............................................54 124 13. Significant Changes from RFC 5050............................54 125 Appendix A. For More Information.................................56 126 Appendix B. CDDL expression......................................57 128 1. Introduction 130 Since the publication of the Bundle Protocol Specification 131 (Experimental RFC 5050 [RFC5050]) in 2007, the Delay-Tolerant 132 Networking (DTN) Bundle Protocol has been implemented in multiple 133 programming languages and deployed to a wide variety of computing 134 platforms. This implementation and deployment experience has 135 identified opportunities for making the protocol simpler, more 136 capable, and easier to use. The present document, standardizing the 137 Bundle Protocol (BP), is adapted from RFC 5050 in that context, 138 reflecting lessons learned. Significant changes from the Bundle 139 Protocol specification defined in RFC 5050 are listed in section 13. 141 This document describes version 7 of BP. 143 Delay Tolerant Networking is a network architecture providing 144 communications in and/or through highly stressed environments. 145 Stressed networking environments include those with intermittent 146 connectivity, large and/or variable delays, and high bit error 147 rates. To provide its services, BP may be viewed as sitting at the 148 application layer of some number of constituent networks, forming a 149 store-carry-forward overlay network. Key capabilities of BP 150 include: 152 . Ability to use physical motility for the movement of data 153 . Ability to move the responsibility for error control from one 154 node to another 155 . Ability to cope with intermittent connectivity, including cases 156 where the sender and receiver are not concurrently present in 157 the network 158 . Ability to take advantage of scheduled, predicted, and 159 opportunistic connectivity, whether bidirectional or 160 unidirectional, in addition to continuous connectivity 161 . Late binding of overlay network endpoint identifiers to 162 underlying constituent network addresses 164 For descriptions of these capabilities and the rationale for the DTN 165 architecture, see [ARCH] and [SIGC]. 167 BP's location within the standard protocol stack is as shown in Figure 168 1. BP uses underlying "native" transport and/or network protocols for 169 communications within a given constituent network. The layer at which 170 those underlying protocols are located is here termed the "convergence 171 layer" and the interface between the bundle protocol and a specific 172 underlying protocol is termed a "convergence layer adapter". 174 Figure 1 shows three distinct transport and network protocols 175 (denoted T1/N1, T2/N2, and T3/N3). 177 +-----------+ +-----------+ 178 | BP app | | BP app | 179 +---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+ 180 | BP v | | ^ BP v | | ^ BP v | | ^ BP | 181 +---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+ 182 | T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 | 183 +---------v-+ +-^---------v-+ +-^---------v + +-^---------+ 184 | N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 | 185 +---------v-+ +-^---------v + +-^---------v-+ +-^---------+ 186 | >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ | 187 +-----------+ +-------------+ +-------------+ +-----------+ 188 | | | | 189 |<---- A network ---->| |<---- A network ---->| 190 | | | | 192 Figure 1: The Bundle Protocol in the Protocol Stack Model 194 This document describes the format of the protocol data units 195 (called "bundles") passed between entities participating in BP 196 communications. 198 The entities are referred to as "bundle nodes". This document does 199 not address: 201 . Operations in the convergence layer adapters that bundle nodes 202 use to transport data through specific types of internets. 203 (However, the document does discuss the services that must be 204 provided by each adapter at the convergence layer.) 205 . The bundle route computation algorithm. 206 . Mechanisms for populating the routing or forwarding information 207 bases of bundle nodes. 208 . The mechanisms for securing bundles en route. 209 . The mechanisms for managing bundle nodes. 211 Note that implementations of the specification presented in this 212 document will not be interoperable with implementations of RFC 5050. 214 2. Conventions used in this document 216 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 217 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 218 "OPTIONAL" in this document are to be interpreted as described in 219 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 220 capitals, as shown here. 222 3. Service Description 224 3.1. Definitions 226 Bundle - A bundle is a protocol data unit of BP, so named because 227 negotiation of the parameters of a data exchange may be impractical 228 in a delay-tolerant network: it is often better practice to "bundle" 229 with a unit of application data all metadata that might be needed in 230 order to make the data immediately usable when delivered to the 231 application. Each bundle comprises a sequence of two or more 232 "blocks" of protocol data, which serve various purposes. 234 Block - A bundle protocol block is one of the protocol data 235 structures that together constitute a well-formed bundle. 237 Application Data Unit (ADU) - An application data unit is the unit 238 of data whose conveyance to the bundle's destination is the purpose 239 for the transmission of some bundle that is not a fragment (as 240 defined below). 242 Bundle payload - A bundle payload (or simply "payload") is the 243 content of the bundle's payload block. The terms "bundle content", 244 "bundle payload", and "payload" are used interchangeably in this 245 document. For a bundle that is not a fragment (as defined below), 246 the payload is an application data unit. 248 Partial payload - A partial payload is a payload that comprises 249 either the first N bytes or the last N bytes of some other payload 250 of length M, such that 0 < N < M. Note that every partial payload 251 is a payload and therefore can be further subdivided into partial 252 payloads. 254 Fragment - A fragment is a bundle whose payload block contains a 255 partial payload. 257 Bundle node - A bundle node (or, in the context of this document, 258 simply a "node") is any entity that can send and/or receive bundles. 259 Each bundle node has three conceptual components, defined below, as 260 shown in Figure 2: a "bundle protocol agent", a set of zero or more 261 "convergence layer adapters", and an "application agent". ("CL1 262 PDUs" are the PDUs of the convergence-layer protocol used in network 263 1.) 265 +-----------------------------------------------------------+ 266 |Node | 267 | | 268 | +-------------------------------------------------------+ | 269 | |Application Agent | | 270 | | | | 271 | | +--------------------------+ +----------------------+ | | 272 | | |Administrative element | |Application-specific | | | 273 | | | | |element | | | 274 | | | | | | | | 275 | | +--------------------------+ +----------------------+ | | 276 | | ^ ^ | | 277 | | Admin|records Application|data | | 278 | | | | | | 279 | +----------------v--------------------------v-----------+ | 280 | ^ | 281 | | ADUs | 282 | | | 283 | +-----------------------------v-------------------------+ | 284 | |Bundle Protocol Agent | | 285 | | | | 286 | | | | 287 | +-------------------------------------------------------+ | 288 | ^ ^ ^ | 289 | | Bundles | Bundles Bundles | | 290 | | | | | 291 | +------v-----+ +-----v------+ +-----v-----+ | 292 | |CLA 1 | |CLA 2 | |CLA n | | 293 | | | | | . . . | | | 294 | | | | | | | | 295 +-+------------+-----+------------+-----------+-----------+-+ 296 ^ ^ ^ 297 CL1|PDUs CL2|PDUs CLn|PDUs 298 | | | 299 +------v-----+ +-----v------+ +-----v-----+ 300 Network 1 Network 2 Network n 302 Figure 2: Components of a Bundle Node 304 Bundle protocol agent - The bundle protocol agent (BPA) of a node is 305 the node component that offers the BP services and executes the 306 procedures of the bundle protocol. 308 Convergence layer adapter - A convergence layer adapter (CLA) is a 309 node component that sends and receives bundles on behalf of the BPA, 310 utilizing the services of some 'native' protocol stack that is 311 supported in one of the networks within which the node is 312 functionally located. 314 Application agent - The application agent (AA) of a node is the node 315 component that utilizes the BP services to effect communication for 316 some user purpose. The application agent in turn has two elements, 317 an administrative element and an application-specific element. 319 Application-specific element - The application-specific element of 320 an AA is the node component that constructs, requests transmission 321 of, accepts delivery of, and processes units of user application 322 data. 324 Administrative element - The administrative element of an AA is the 325 node component that constructs and requests transmission of 326 administrative records (defined below), including status reports, 327 and accepts delivery of and processes any administrative records 328 that the node receives. 330 Administrative record - A BP administrative record is an application 331 data unit that is exchanged between the administrative elements of 332 nodes' application agents for some BP administrative purpose. The 333 only administrative record defined in this specification is the 334 status report, discussed later. 336 Bundle endpoint - A bundle endpoint (or simply "endpoint") is a set 337 of zero or more bundle nodes that all identify themselves for BP 338 purposes by some common identifier, called a "bundle endpoint ID" 339 (or, in this document, simply "endpoint ID"; endpoint IDs are 340 described in detail in Section 4.5.5.1 below). Note that any bundle 341 node may be a member of multiple endpoints. 343 Singleton endpoint - A singleton endpoint is an endpoint that always 344 contains exactly one member. 346 Registration - A registration is the state machine characterizing a 347 given node's membership in a given endpoint. Any single 348 registration has an associated delivery failure action as defined 349 below and must at any time be in one of two states: Active or 350 Passive. 352 Delivery - A bundle is considered to have been delivered at a node 353 subject to a registration as soon as the application data unit that 354 is the payload of the bundle, together with any relevant metadata 355 (an implementation matter), has been presented to the node's 356 application agent in a manner consistent with the state of that 357 registration. 359 Deliverability - A bundle is considered "deliverable" subject to a 360 registration if and only if (a) the bundle's destination endpoint is 361 the endpoint with which the registration is associated, (b) the 362 bundle has not yet been delivered subject to this registration, and 363 (c) the bundle has not yet been "abandoned" (as defined below) 364 subject to this registration. 366 Abandonment - To abandon a bundle subject to some registration is to 367 assert that the bundle is not deliverable subject to that 368 registration. 370 Delivery failure action - The delivery failure action of a 371 registration is the action that is to be taken when a bundle that is 372 "deliverable" subject to that registration is received at a time 373 when the registration is in the Passive state. 375 Destination - The destination of a bundle is the endpoint comprising 376 the node(s) at which the bundle is to be delivered (as defined 377 above). 379 Transmission - A transmission is an attempt by a node's BPA to cause 380 copies of a bundle to be delivered to one or more of the nodes that 381 are members of some endpoint (the bundle's destination) in response 382 to a transmission request issued by the node's application agent. 384 Forwarding - To forward a bundle to a node is to invoke the services 385 of one or more CLAs in a sustained effort to cause a copy of the 386 bundle to be received by that node. 388 Discarding - To discard a bundle is to cease all operations on the 389 bundle and functionally erase all references to it. The specific 390 procedures by which this is accomplished are an implementation 391 matter. 393 Retention constraint - A retention constraint is an element of the 394 state of a bundle that prevents the bundle from being discarded. 395 That is, a bundle cannot be discarded while it has any retention 396 constraints. 398 Deletion - To delete a bundle is to remove unconditionally all of 399 the bundle's retention constraints, enabling the bundle to be 400 discarded. 402 3.2. Discussion of BP concepts 404 Multiple instances of the same bundle (the same unit of DTN protocol 405 data) might exist concurrently in different parts of a network -- 406 possibly differing in some blocks -- in the memory local to one or 407 more bundle nodes and/or in transit between nodes. In the context of 408 the operation of a bundle node, a bundle is an instance (copy), in 409 that node's local memory, of some bundle that is in the network. 411 The payload for a bundle forwarded in response to a bundle 412 transmission request is the application data unit whose location is 413 provided as a parameter to that request. The payload for a bundle 414 forwarded in response to reception of a bundle is the payload of the 415 received bundle. 417 In the most familiar case, a bundle node is instantiated as a single 418 process running on a general-purpose computer, but in general the 419 definition is meant to be broader: a bundle node might alternatively 420 be a thread, an object in an object-oriented operating system, a 421 special-purpose hardware device, etc. 423 The manner in which the functions of the BPA are performed is wholly 424 an implementation matter. For example, BPA functionality might be 425 coded into each node individually; it might be implemented as a 426 shared library that is used in common by any number of bundle nodes 427 on a single computer; it might be implemented as a daemon whose 428 services are invoked via inter-process or network communication by 429 any number of bundle nodes on one or more computers; it might be 430 implemented in hardware. 432 Every CLA implements its own thin layer of protocol, interposed 433 between BP and the (usually "top") protocol(s) of the underlying 434 native protocol stack; this "CL protocol" may only serve to 435 multiplex and de-multiplex bundles to and from the underlying native 436 protocol, or it may offer additional CL-specific functionality. The 437 manner in which a CLA sends and receives bundles, as well as the 438 definitions of CLAs and CL protocols, are beyond the scope of this 439 specification. 441 Note that the administrative element of a node's application agent 442 may itself, in some cases, function as a convergence-layer adapter. 443 That is, outgoing bundles may be "tunneled" through encapsulating 444 bundles: 446 . An outgoing bundle constitutes a byte array. This byte array 447 may, like any other, be presented to the bundle protocol agent 448 as an application data unit that is to be transmitted to some 449 endpoint. 450 . The original bundle thus forms the payload of an encapsulating 451 bundle that is forwarded using some other convergence-layer 452 protocol(s). 453 . When the encapsulating bundle is received, its payload is 454 delivered to the peer application agent administrative element, 455 which then instructs the bundle protocol agent to dispatch that 456 original bundle in the usual way. 458 The purposes for which this technique may be useful (such as cross- 459 domain security) are beyond the scope of this specification. 461 The only interface between the BPA and the application-specific 462 element of the AA is the BP service interface. But between the BPA 463 and the administrative element of the AA there is a (conceptual) 464 private control interface in addition to the BP service interface. 465 This private control interface enables the BPA and the 466 administrative element of the AA to direct each other to take action 467 under specific circumstances. 469 In the case of a node that serves simply as a BP "router", the AA 470 may have no application-specific element at all. The application- 471 specific elements of other nodes' AAs may perform arbitrarily 472 complex application functions, perhaps even offering multiplexed DTN 473 communication services to a number of other applications. As with 474 the BPA, the manner in which the AA performs its functions is wholly 475 an implementation matter. 477 Singletons are the most familiar sort of endpoint, but in general 478 the endpoint notion is meant to be broader. For example, the nodes 479 in a sensor network might constitute a set of bundle nodes that 480 identify themselves by a single common endpoint ID and thus form a 481 single bundle endpoint. *Note* too that a given bundle node might 482 identify itself by multiple endpoint IDs and thus be a member of 483 multiple bundle endpoints. 485 The destination of every bundle is an endpoint, which may or may not 486 be singleton. The source of every bundle is a node, identified by 487 the endpoint ID for some singleton endpoint that contains that node. 488 Note, though, that the source node ID asserted in a given bundle may 489 be the null endpoint ID (as described later) rather than the 490 endpoint ID of the actual source node; bundles for which the 491 asserted source node ID is the null endpoint ID are termed 492 "anonymous" bundles. 494 Any number of transmissions may be concurrently undertaken by the 495 bundle protocol agent of a given node. 497 When the bundle protocol agent of a node determines that a bundle 498 must be forwarded to a node (either to a node that is a member of 499 the bundle's destination endpoint or to some intermediate forwarding 500 node) in the course of completing the successful transmission of 501 that bundle, the bundle protocol agent invokes the services of one 502 or more CLAs in a sustained effort to cause a copy of the bundle to 503 be received by that node. 505 Upon reception, the processing of a bundle that has been received by 506 a given node depends on whether or not the receiving node is 507 registered in the bundle's destination endpoint. If it is, and if 508 the payload of the bundle is non-fragmentary (possibly as a result 509 of successful payload reassembly from fragmentary payloads, 510 including the original payload of the newly received bundle), then 511 the bundle is normally delivered to the node's application agent 512 subject to the registration characterizing the node's membership in 513 the destination endpoint. 515 The bundle protocol does not natively ensure delivery of a bundle to 516 its destination. Data loss along the path to the destination node 517 can be minimized by utilizing reliable convergence-layer protocols 518 between neighbors on all segments of the end-to-end path, but for 519 end-to-end bundle delivery assurance it will be necessary to develop 520 extensions to the bundle protocol and/or application-layer 521 mechanisms. 523 The bundle protocol is designed for extensibility. Bundle protocol 524 extensions, documented elsewhere, may extend this specification by: 526 . defining additional blocks; 527 . defining additional administrative records; 528 . defining additional bundle processing flags; 529 . defining additional block processing flags; 530 . defining additional types of bundle status reports; 531 . defining additional bundle status report reason codes; 532 . defining additional mandates and constraints on processing 533 that conformant bundle protocol agents must perform at 534 specified points in the inbound and outbound bundle processing 535 cycles. 537 3.3. Services Offered by Bundle Protocol Agents 539 The BPA of each node is expected to provide the following services 540 to the node's application agent: 542 . commencing a registration (registering the node in an 543 endpoint); 544 . terminating a registration; 545 . switching a registration between Active and Passive states; 546 . transmitting a bundle to an identified bundle endpoint; 547 . canceling a transmission; 548 . polling a registration that is in the Passive state; 549 . delivering a received bundle. 551 Note that the details of registration functionality are an 552 implementation matter and are beyond the scope of this 553 specification. 555 4. Bundle Format 557 The format of bundles SHALL conform to the Concise Binary Object 558 Representation (CBOR [RFC7049]). 560 Each bundle SHALL be a concatenated sequence of at least two blocks, 561 represented as a CBOR indefinite-length array. The first block in 562 the sequence (the first item of the array) MUST be a primary bundle 563 block in CBOR representation as described below; the bundle MUST 564 have exactly one primary bundle block. The primary block MUST be 565 followed by one or more canonical bundle blocks (additional array 566 items) in CBOR representation as described in 4.2.3 below. The last 567 such block MUST be a payload block; the bundle MUST have exactly one 568 payload block. The payload block SHALL be followed by a CBOR 569 "break" stop code, terminating the array. 571 (Note that, while CBOR permits considerable flexibility in the 572 encoding of bundles, this flexibility must not be interpreted as 573 inviting increased complexity in protocol data unit structure.) 575 An implementation of the Bundle Protocol MAY discard any sequence of 576 bytes that does not conform to the Bundle Protocol specification. 578 An implementation of the Bundle Protocol MAY accept a sequence of 579 bytes that does not conform to the Bundle Protocol specification 580 (e.g., one that represents data elements in fixed-length arrays 581 rather than indefinite-length arrays) and transform it into 582 conformant BP structure before processing it. Procedures for 583 accomplishing such a transformation are beyond the scope of this 584 specification. 586 4.1. BP Fundamental Data Structures 588 4.1.1. CRC Type 590 CRC type is an unsigned integer type code for which the following 591 values (and no others) are valid: 593 . 0 indicates "no CRC is present." 594 . 1 indicates "a standard X-25 CRC-16 is present." [CRC16] 595 . 2 indicates "a standard CRC32C (Castagnoli) CRC-32 is present." 596 [RFC4960] 598 CRC type SHALL be represented as a CBOR unsigned integer. 600 For examples of CRC32C CRCs, see Appendix A.4 of [RFC7143]. 602 Note that more robust protection of BP data integrity, as needed, 603 may be provided by means of Block Integrity Blocks as defined in the 604 Bundle Security Protocol [BPSEC]). 606 4.1.2. CRC 608 CRC SHALL be omitted from a block if and only if the block's CRC 609 type code is zero. 611 When not omitted, the CRC SHALL be represented as a CBOR byte string 612 of two bytes (that is, CBOR additional information 2, if CRC type is 613 1) or of four bytes (that is, CBOR additional information 4, if CRC 614 type is 2); in each case the sequence of bytes SHALL constitute an 615 unsigned integer value (of 16 or 32 bits, respectively) in network 616 byte order. 618 4.1.3. Bundle Processing Control Flags 620 Bundle processing control flags assert properties of the bundle as a 621 whole rather than of any particular block of the bundle. They are 622 conveyed in the primary block of the bundle. 624 The following properties are asserted by the bundle processing 625 control flags: 627 . The bundle is a fragment. (Boolean) 629 . The bundle's payload is an administrative record. (Boolean) 631 . The bundle must not be fragmented. (Boolean) 633 . Acknowledgment by the user application is requested. (Boolean) 635 . Status time is requested in all status reports. (Boolean) 637 . Flags requesting types of status reports (all Boolean): 639 o Request reporting of bundle reception. 641 o Request reporting of bundle forwarding. 643 o Request reporting of bundle delivery. 645 o Request reporting of bundle deletion. 647 If the bundle processing control flags indicate that the bundle's 648 application data unit is an administrative record, then all status 649 report request flag values MUST be zero. 651 If the bundle's source node is omitted (i.e., the source node ID is 652 the ID of the null endpoint, which has no members as discussed 653 below; this option enables anonymous bundle transmission), then the 654 bundle is not uniquely identifiable and all bundle protocol features 655 that rely on bundle identity must therefore be disabled: the "Bundle 656 must not be fragmented" flag value MUST be 1 and all status report 657 request flag values MUST be zero. 659 The bundle processing control flags SHALL be represented as a CBOR 660 unsigned integer item, the value of which SHALL be processed as a 661 bit field indicating the control flag values as follows (note that 662 bit numbering in this instance is reversed from the usual practice, 663 beginning with the low-order bit instead of the high-order bit, in 664 recognition of the potential definition of additional control flag 665 values in the future): 667 . Bit 0 (the low-order bit, 0x000001): bundle is a fragment. 668 . Bit 1 (0x000002): payload is an administrative record. 669 . Bit 2 (0x000004): bundle must not be fragmented. 670 . Bit 3 (0x000008): reserved. 671 . Bit 4 (0x000010): reserved. 672 . Bit 5 (0x000020): user application acknowledgement is 673 requested. 674 . Bit 6 (0x000040): status time is requested in all status 675 reports. 676 . Bit 7 (0x000080): reserved. 677 . Bit 8 (0x000100): reserved. 678 . Bit 9 (0x000200): reserved. 679 . Bit 10(0x000400): reserved. 680 . Bit 11(0x000800): reserved. 681 . Bit 12(0x001000): reserved. 682 . Bit 13(0x002000): reserved. 683 . Bit 14(0x004000): bundle reception status reports are 684 requested. 685 . Bit 15(0x008000): reserved. 686 . Bit 16(0x010000): bundle forwarding status reports are 687 requested. 688 . Bit 17(0x020000): bundle delivery status reports are requested. 689 . Bit 18(0x040000): bundle deletion status reports are requested. 690 . Bits 19-20 are reserved. 691 . Bits 21-63 are unassigned. 693 4.1.4. Block Processing Control Flags 695 The block processing control flags assert properties of canonical 696 bundle blocks. They are conveyed in the header of the block to 697 which they pertain. 699 The block processing control flags SHALL be represented as a CBOR 700 unsigned integer item, the value of which SHALL be processed as a 701 bit field indicating the control flag values as follows (note that 702 bit numbering in this instance is reversed from the usual practice, 703 beginning with the low-order bit instead of the high-order bit, for 704 agreement with the bit numbering of the bundle processing control 705 flags): 707 . Bit 0(the low-order bit, 0x01): block must be replicated in 708 every fragment. 709 . Bit 1(0x02): transmission of a status report is requested if 710 block can't be processed. 711 . Bit 2(0x04): bundle must be deleted if block can't be 712 processed. 713 . Bit 3(0x08): reserved. 714 . Bit 4(0x10): block must be removed from bundle if it can't be 715 processed. 716 . Bit 5(0x20): reserved. 717 . Bit 6 (0x40): reserved. 718 . Bits 7-63 are unassigned. 720 For each bundle whose bundle processing control flags indicate that 721 the bundle's application data unit is an administrative record, or 722 whose source node ID is the null endpoint ID as defined below, the 723 value of the "Transmit status report if block can't be processed" 724 flag in every canonical block of the bundle MUST be zero. 726 4.1.5. Identifiers 728 4.1.5.1. Endpoint ID 730 The destinations of bundles are bundle endpoints, identified by text 731 strings termed "endpoint IDs" (see Section 3.1). Each endpoint ID 732 (EID) is a Uniform Resource Identifier (URI; [URI]). As such, each 733 endpoint ID can be characterized as having this general structure: 735 < scheme name > : < scheme-specific part, or "SSP" > 737 The scheme identified by the < scheme name > in an endpoint ID is a 738 set of syntactic and semantic rules that fully explain how to parse 739 and interpret the SSP. Each scheme that may be used to form a BP 740 endpoint ID must be added to the registry of URI scheme code numbers 741 for Bundle Protocol maintained by IANA as described in Section 10; 742 association of a unique URI scheme code number with each scheme name 743 in this registry helps to enable compact representation of endpoint 744 IDs in bundle blocks. Note that the set of allowable schemes is 745 effectively unlimited. Any scheme conforming to [URIREG] may be 746 added to the URI scheme code number registry and thereupon used in a 747 bundle protocol endpoint ID. 749 Each entry in the URI scheme code number registry MUST contain a 750 reference to a scheme code number definition document, which defines 751 the manner in which the scheme-specific part of any URI formed in 752 that scheme is parsed and interpreted and MUST be encoded, in CBOR 753 representation, for transmission as a BP endpoint ID. The scheme 754 code number definition document may also contain information as to 755 (a) which convergence-layer protocol(s) may be used to forward a 756 bundle to a BP destination endpoint identified by such an ID, and 757 (b) how the ID of the convergence-layer protocol endpoint to use for 758 that purpose can be inferred from that destination endpoint ID. 760 Note that, although endpoint IDs are URIs, implementations of the BP 761 service interface may support expression of endpoint IDs in some 762 internationalized manner (e.g., Internationalized Resource 763 Identifiers (IRIs); see [RFC3987]). 765 The endpoint ID "dtn:none" identifies the "null endpoint", the 766 endpoint that by definition never has any members. 768 Each BP endpoint ID (EID) SHALL be represented as a CBOR array 769 comprising two items. 771 The first item of the array SHALL be the code number identifying the 772 endpoint's URI scheme, as defined in the registry of URI scheme code 773 numbers for Bundle Protocol. Each URI scheme code number SHALL be 774 represented as a CBOR unsigned integer. 776 The second item of the array SHALL be the applicable CBOR 777 representation of the scheme-specific part (SSP) of the EID, defined 778 as follows: 780 . If the EID's URI scheme is "dtn" then the SSP SHALL be 781 represented as a CBOR text string unless the EID's SSP is 782 "none", in which case the SSP SHALL be represented as a CBOR 783 unsigned integer with the value zero. 784 . If the EID's URI scheme is "ipn" then the SSP SHALL be 785 represented as a CBOR array comprising two items. The first 786 item of this array SHALL be the EID's node number (a number 787 that identifies the node) represented as a CBOR unsigned 788 integer. The second item of this array SHALL be the EID's 789 service number (a number that identifies some application 790 service) represented as a CBOR unsigned integer. 792 . Definitions of the CBOR representations of the SSPs of EIDs 793 encoded in other URI schemes are included in the scheme code 794 number definition documents for those schemes. 796 4.1.5.2. Node ID 798 For many purposes of the Bundle Protocol it is important to identify 799 the node that is operative in some context. 801 As discussed in 3.1 above, nodes are distinct from endpoints; 802 specifically, an endpoint is a set of zero or more nodes. But 803 rather than define a separate namespace for node identifiers, we 804 instead use endpoint identifiers to identify nodes, subject to the 805 following restrictions: 807 . Every node MUST be a member of at least one singleton endpoint. 808 . The EID of any singleton endpoint of which a node is a member 809 MAY be used to identify that node. A "node ID" is an EID that 810 is used in this way. 811 . A node's membership in a given singleton endpoint MUST be 812 sustained at least until the nominal operation of the Bundle 813 Protocol no longer depends on the identification of that node 814 using that endpoint's ID. 816 4.1.6. DTN Time 818 A DTN time is an unsigned integer indicating the number of seconds 819 that have elapsed since the start of the year 2000 on the 820 Coordinated Universal Time (UTC) scale [UTC]. Each DTN time SHALL 821 be represented as a CBOR unsigned integer item. 823 Implementers need to be aware that DTN time values conveyed in CBOR 824 representation in bundles can conceivably exceed (2**32 - 1). 826 4.1.7. Creation Timestamp 828 Each creation timestamp SHALL be represented as a CBOR array item 829 comprising a 2-tuple. 831 The first item of the array SHALL be a DTN time. 833 The second item of the array SHALL be the creation timestamp's 834 sequence number, represented as a CBOR unsigned integer. 836 4.1.8. Block-type-specific Data 838 Block-type-specific data in each block (other than the primary 839 block) SHALL be the applicable CBOR representation of the content of 840 the block. Details of this representation are included in the 841 specification defining the block type. 843 4.2. Bundle Representation 845 This section describes the primary block in detail and non-primary 846 blocks in general. Rules for processing these blocks appear in 847 Section 5 of this document. 849 Note that supplementary DTN protocol specifications (including, but 850 not restricted to, the Bundle Security Protocol [BPSEC]) may require 851 that BP implementations conforming to those protocols construct and 852 process additional blocks. 854 4.2.1. Bundle 856 Each bundle SHALL be represented as a CBOR indefinite-length array. 857 The first item of this array SHALL be the CBOR representation of a 858 Primary Block. Every other item of the array SHALL be the CBOR 859 representation of a Canonical Block. The last block of the bundle 860 SHALL be followed by a CBOR "break" stop code, terminating the 861 array. 863 Associated with each block of a bundle is a block number. The block 864 number uniquely identifies the block within the bundle, enabling 865 blocks (notably bundle security protocol blocks) to reference other 866 blocks in the same bundle without ambiguity. The block number of 867 the primary block is implicitly zero; the block numbers of all other 868 blocks are explicitly stated in block headers as noted below. Block 869 numbering is unrelated to the order in which blocks are sequenced in 870 the bundle. The block number of the payload block is always 1. 872 4.2.2. Primary Bundle Block 874 The primary bundle block contains the basic information needed to 875 forward bundles to their destinations. 877 Each primary block SHALL be represented as a CBOR array; the number 878 of elements in the array SHALL be 8 (if the bundle is not a fragment 879 and the block has no CRC), 9 (if the block has a CRC and the bundle 880 is not a fragment), 10 (if the bundle is a fragment and the block 881 has no CRC), or 11 (if the bundle is a fragment and the block has a 882 CRC). 884 The primary block of each bundle SHALL be immutable. The values of 885 all fields in the primary block must remain unchanged from the time 886 the block is created to the time it is delivered. 888 The fields of the primary bundle block SHALL be as follows, listed 889 in the order in which they MUST appear: 891 Version: An unsigned integer value indicating the version of the 892 bundle protocol that constructed this block. The present document 893 describes version 7 of the bundle protocol. Version number SHALL be 894 represented as a CBOR unsigned integer item. 896 Bundle Processing Control Flags: The Bundle Processing Control Flags 897 are discussed in Section 4.1.3. above. 899 CRC Type: CRC Type codes are discussed in Section 4.1.1. above. The 900 CRC Type code for the primary block MAY be zero if the bundle 901 contains a BPsec [BPSEC] Block Integrity Block whose target is the 902 primary block; otherwise the CRC Type code for the primary block 903 MUST be non-zero. 905 Destination EID: The Destination EID field identifies the bundle 906 endpoint that is the bundle's destination, i.e., the endpoint that 907 contains the node(s) at which the bundle is to be delivered. 909 Source node ID: The Source node ID field identifies the bundle node 910 at which the bundle was initially transmitted, except that Source 911 node ID may be the null endpoint ID in the event that the bundle's 912 source chooses to remain anonymous. 914 Report-to EID: The Report-to EID field identifies the bundle 915 endpoint to which status reports pertaining to the forwarding and 916 delivery of this bundle are to be transmitted. 918 Creation Timestamp: The creation timestamp (discussed in 4.1.7 919 above) comprises two unsigned integers that, together with the 920 source node ID and (if the bundle is a fragment) the fragment offset 921 and payload length, serve to identify the bundle. The first of these 922 integers is the bundle's creation time, while the second is the 923 bundle's creation timestamp sequence number. Bundle creation time 924 SHALL be the DTN time at which the transmission request was received 925 that resulted in the creation of the bundle. Sequence count SHALL be 926 the latest value (as of the time at which that transmission request 927 was received) of a monotonically increasing positive integer counter 928 managed by the source node's bundle protocol agent that MAY be reset 929 to zero whenever the current time advances by one second. For nodes 930 that lack accurate clocks, it is recommended that bundle creation 931 time be set to zero and that the counter used as the source of the 932 bundle sequence count never be reset to zero. Note that, in general, 933 the creation of two distinct bundles with the same source node ID 934 and bundle creation timestamp may result in unexpected network 935 behavior and/or suboptimal performance. The combination of source 936 node ID and bundle creation timestamp serves to identify a single 937 transmission request, enabling it to be acknowledged by the 938 receiving application (provided the source node ID is not the null 939 endpoint ID). 941 Lifetime: The lifetime field is an unsigned integer that indicates 942 the time at which the bundle's payload will no longer be useful, 943 encoded as a number of microseconds past the creation time. (For 944 high-rate deployments with very brief disruptions, fine-grained 945 expression of bundle lifetime may be useful.) When a bundle's age 946 exceeds its lifetime, bundle nodes need no longer retain or forward 947 the bundle; the bundle SHOULD be deleted from the network. 949 If the asserted lifetime for a received bundle is so lengthy that 950 retention of the bundle until its expiration time might degrade 951 operation of the node, the bundle protocol agent of the node at 952 which the bundle is received MAY impose a temporary overriding 953 lifetime of shorter duration; such override lifetime SHALL NOT 954 replace the lifetime asserted in the bundle but SHALL serve as the 955 bundle's effective lifetime while the bundle resides at that node. 956 Procedures for imposing lifetime overrides are beyond the scope of 957 this specification. 959 For bundles originating at nodes that lack accurate clocks, it is 960 recommended that bundle age be obtained from the Bundle Age 961 extension block (see 4.3.2 below) rather than from the difference 962 between current time and bundle creation time. Bundle lifetime 963 SHALL be represented as a CBOR unsigned integer item. 965 Fragment offset: If and only if the Bundle Processing Control Flags 966 of this Primary block indicate that the bundle is a fragment, 967 fragment offset SHALL be present in the primary block. Fragment 968 offset SHALL be represented as a CBOR unsigned integer indicating 969 the offset from the start of the original application data unit at 970 which the bytes comprising the payload of this bundle were located. 972 Total Application Data Unit Length: If and only if the Bundle 973 Processing Control Flags of this Primary block indicate that the 974 bundle is a fragment, total application data unit length SHALL be 975 present in the primary block. Total application data unit length 976 SHALL be represented as a CBOR unsigned integer indicating the total 977 length of the original application data unit of which this bundle's 978 payload is a part. 980 CRC: A CRC SHALL be present in the primary block unless the bundle 981 includes a BPsec [BPSEC] Block Integrity Block whose target is the 982 primary block, in which case a CRC MAY be present in the primary 983 block. The length and nature of the CRC SHALL be as indicated by 984 the CRC type. The CRC SHALL be computed over the concatenation of 985 all bytes (including CBOR "break" characters) of the primary block 986 including the CRC field itself, which for this purpose SHALL be 987 temporarily populated with all bytes set to zero. 989 4.2.3. Canonical Bundle Block Format 991 Every block other than the primary block (all such blocks are termed 992 "canonical" blocks) SHALL be represented as a CBOR array; the number 993 of elements in the array SHALL be 5 (if CRC type is zero) or 6 994 (otherwise). 996 The fields of every canonical block SHALL be as follows, listed in 997 the order in which they MUST appear: 999 . Block type code, an unsigned integer. Bundle block type code 1 1000 indicates that the block is a bundle payload block. Block type 1001 codes 2 through 9 are explicitly reserved as noted later in 1002 this specification. Block type codes 192 through 255 are not 1003 reserved and are available for private and/or experimental use. 1004 All other block type code values are reserved for future use. 1005 . Block number, an unsigned integer as discussed in 4.2.1 above. 1006 Block number SHALL be represented as a CBOR unsigned integer. 1007 . Block processing control flags as discussed in Section 4.1.4 1008 above. 1009 . CRC type as discussed in Section 4.1.1 above. 1010 . Block-type-specific data represented as a single definite- 1011 length CBOR byte string, i.e., a CBOR byte string that is not 1012 of indefinite length. For each type of block, the block-type- 1013 specific data byte string is the serialization, in a block- 1014 type-specific manner, of the data conveyed by that type of 1015 block; definitions of blocks are required to define the manner 1016 in which block-type-specific data are serialized within the 1017 block-type-specific data field. For the Payload Block in 1018 particular (block type 1), the block-type-specific data field, 1019 termed the "payload", SHALL be an application data unit, or 1020 some contiguous extent thereof, represented as a definite- 1021 length CBOR byte string. 1022 . If and only if the value of the CRC type field of this block is 1023 non-zero, a CRC. If present, the length and nature of the CRC 1024 SHALL be as indicated by the CRC type and the CRC SHALL be 1025 computed over the concatenation of all bytes of the block 1026 (including CBOR "break" characters) including the CRC field 1027 itself, which for this purpose SHALL be temporarily populated 1028 with all bytes set to zero. 1030 4.3. Extension Blocks 1032 "Extension blocks" are all blocks other than the primary and payload 1033 blocks. Because not all extension blocks are defined in the Bundle 1034 Protocol specification (the present document), not all nodes 1035 conforming to this specification will necessarily instantiate Bundle 1036 Protocol implementations that include procedures for processing 1037 (that is, recognizing, parsing, acting on, and/or producing) all 1038 extension blocks. It is therefore possible for a node to receive a 1039 bundle that includes extension blocks that the node cannot process. 1040 The values of the block processing control flags indicate the action 1041 to be taken by the bundle protocol agent when this is the case. 1043 The following extension blocks are defined in the current document. 1045 4.3.1. Previous Node 1047 The Previous Node block, block type 6, identifies the node that 1048 forwarded this bundle to the local node (i.e., to the node at which 1049 the bundle currently resides); its block-type-specific data is the 1050 node ID of that forwarder node which SHALL take the form of a node 1051 ID represented as described in Section 4.1.5.2. above. If the local 1052 node is the source of the bundle, then the bundle MUST NOT contain 1053 any Previous Node block. Otherwise the bundle SHOULD contain one 1054 (1) occurrence of this type of block and MUST NOT contain more than 1055 one. 1057 4.3.2. Bundle Age 1059 The Bundle Age block, block type 7, contains the number of 1060 microseconds that have elapsed between the time the bundle was 1061 created and time at which it was most recently forwarded. It is 1062 intended for use by nodes lacking access to an accurate clock, to 1063 aid in determining the time at which a bundle's lifetime expires. 1064 The block-type-specific data of this block is an unsigned integer 1065 containing the age of the bundle in microseconds, which SHALL be 1066 represented as a CBOR unsigned integer item. (The age of the bundle 1067 is the sum of all known intervals of the bundle's residence at 1068 forwarding nodes, up to the time at which the bundle was most 1069 recently forwarded, plus the summation of signal propagation time 1070 over all episodes of transmission between forwarding nodes. 1072 Determination of these values is an implementation matter.) If the 1073 bundle's creation time is zero, then the bundle MUST contain exactly 1074 one (1) occurrence of this type of block; otherwise, the bundle MAY 1075 contain at most one (1) occurrence of this type of block. A bundle 1076 MUST NOT contain multiple occurrences of the bundle age block, as 1077 this could result in processing anomalies. 1079 4.3.3. Hop Count 1081 The Hop Count block, block type 10, contains two unsigned integers, 1082 hop limit and hop count. A "hop" is here defined as an occasion on 1083 which a bundle was forwarded from one node to another node. Hop 1084 limit MUST be in the range 1 through 255. The hop limit value SHOULD 1085 NOT be changed at any time after creation of the Hop Count block; 1086 the hop count value SHOULD initially be zero and SHOULD be increased 1087 by 1 on each hop. 1089 The hop count block is mainly intended as a safety mechanism, a 1090 means of identifying bundles for removal from the network that can 1091 never be delivered due to a persistent forwarding error. Hop count 1092 is particularly valuable as a defense against routing anomalies that 1093 might cause a bundle to be forwarded in a cyclical "ping-pong" 1094 fashion between two nodes. When a bundle's hop count exceeds its 1095 hop limit, the bundle SHOULD be deleted for the reason "hop limit 1096 exceeded", following the bundle deletion procedure defined in 1097 Section 5.10. 1099 Procedures for determining the appropriate hop limit for a bundle 1100 are beyond the scope of this specification. 1102 The block-type-specific data in a hop count block SHALL be 1103 represented as a CBOR array comprising a 2-tuple. The first item of 1104 this array SHALL be the bundle's hop limit, represented as a CBOR 1105 unsigned integer. The second item of this array SHALL be the 1106 bundle's hop count, represented as a CBOR unsigned integer. A bundle 1107 MAY contain one occurrence of this type of block but MUST NOT 1108 contain more than one. 1110 5. Bundle Processing 1112 The bundle processing procedures mandated in this section and in 1113 Section 6 govern the operation of the Bundle Protocol Agent and the 1114 Application Agent administrative element of each bundle node. They 1115 are neither exhaustive nor exclusive. Supplementary DTN protocol 1116 specifications (including, but not restricted to, the Bundle 1117 Security Protocol [BPSEC]) may augment, override, or supersede the 1118 mandates of this document. 1120 5.1. Generation of Administrative Records 1122 All transmission of bundles is in response to bundle transmission 1123 requests presented by nodes' application agents. When required to 1124 "generate" an administrative record (such as a bundle status 1125 report), the bundle protocol agent itself is responsible for causing 1126 a new bundle to be transmitted, conveying that record. In concept, 1127 the bundle protocol agent discharges this responsibility by 1128 directing the administrative element of the node's application agent 1129 to construct the record and request its transmission as detailed in 1130 Section 6 below. In practice, the manner in which administrative 1131 record generation is accomplished is an implementation matter, 1132 provided the constraints noted in Section 6 are observed. 1134 Status reports are relatively small bundles. Moreover, even when 1135 the generation of status reports is enabled the decision on whether 1136 or not to generate a requested status report is left to the 1137 discretion of the bundle protocol agent. Nonetheless, note that 1138 requesting status reports for any single bundle might easily result 1139 in the generation of (1 + (2 *(N-1))) status report bundles, where N 1140 is the number of nodes on the path from the bundle's source to its 1141 destination, inclusive. That is, the requesting of status reports 1142 for large numbers of bundles could result in an unacceptable 1143 increase in the bundle traffic in the network. For this reason, the 1144 generation of status reports MUST be disabled by default and enabled 1145 only when the risk of excessive network traffic is deemed 1146 acceptable. Mechanisms that could assist in assessing and 1147 mitigating this risk, such as pre-placed agreements authorizing the 1148 generation of status reports under specified circumstances, are 1149 beyond the scope of this specification. 1151 Notes on administrative record terminology: 1153 . A "bundle reception status report" is a bundle status report 1154 with the "reporting node received bundle" flag set to 1. 1155 . A "bundle forwarding status report" is a bundle status report 1156 with the "reporting node forwarded the bundle" flag set to 1. 1157 . A "bundle delivery status report" is a bundle status report 1158 with the "reporting node delivered the bundle" flag set to 1. 1159 . A "bundle deletion status report" is a bundle status report 1160 with the "reporting node deleted the bundle" flag set to 1. 1162 5.2. Bundle Transmission 1164 The steps in processing a bundle transmission request are: 1166 Step 1: Transmission of the bundle is initiated. An outbound bundle 1167 MUST be created per the parameters of the bundle transmission 1168 request, with the retention constraint "Dispatch pending". The 1169 source node ID of the bundle MUST be either the null endpoint ID, 1170 indicating that the source of the bundle is anonymous, or else the 1171 EID of a singleton endpoint whose only member is the node of which 1172 the BPA is a component. 1174 Step 2: Processing proceeds from Step 1 of Section 5.4. 1176 5.3. Bundle Dispatching 1178 The steps in dispatching a bundle are: 1180 Step 1: If the bundle's destination endpoint is an endpoint of which 1181 the node is a member, the bundle delivery procedure defined in 1182 Section 5.7 MUST be followed and for the purposes of all subsequent 1183 processing of this bundle at this node the node's membership in the 1184 bundle's destination endpoint SHALL be disavowed; specifically, even 1185 though the node is a member of the bundle's destination endpoint, 1186 the node SHALL NOT undertake to forward the bundle to itself in the 1187 course of performing the procedure described in Section 5.4. 1189 Step 2: Processing proceeds from Step 1 of Section 5.4. 1191 5.4. Bundle Forwarding 1193 The steps in forwarding a bundle are: 1195 Step 1: The retention constraint "Forward pending" MUST be added to 1196 the bundle, and the bundle's "Dispatch pending" retention constraint 1197 MUST be removed. 1199 Step 2: The bundle protocol agent MUST determine whether or not 1200 forwarding is contraindicated (that is, rendered inadvisable) for 1201 any of the reasons listed in the IANA registry of Bundle Status 1202 Report Reason Codes (see section 10.5 below), whose initial contents 1203 are listed in Figure 4. In particular: 1205 . The bundle protocol agent MAY choose either to forward the 1206 bundle directly to its destination node(s) (if possible) or to 1207 forward the bundle to some other node(s) for further 1208 forwarding. The manner in which this decision is made may 1209 depend on the scheme name in the destination endpoint ID and/or 1210 on other state but in any case is beyond the scope of this 1211 document; one possible mechanism is described in [SBAR]. If the 1212 BPA elects to forward the bundle to some other node(s) for 1213 further forwarding but finds it impossible to select any 1214 node(s) to forward the bundle to, then forwarding is 1215 contraindicated. 1216 . Provided the bundle protocol agent succeeded in selecting the 1217 node(s) to forward the bundle to, the bundle protocol agent 1218 MUST subsequently select the convergence layer adapter(s) whose 1219 services will enable the node to send the bundle to those 1220 nodes. The manner in which specific appropriate convergence 1221 layer adapters are selected is beyond the scope of this 1222 document; the TCP convergence-layer adapter [TCPCL] MUST be 1223 implemented but may not be appropriate for the forwarding of 1224 any particular bundle. If the agent finds it impossible to 1225 select any appropriate convergence layer adapter(s) to use in 1226 forwarding this bundle, then forwarding is contraindicated. 1228 Step 3: If forwarding of the bundle is determined to be 1229 contraindicated for any of the reasons listed in the IANA registry 1230 of Bundle Status Report Reason Codes (see section 10.5 below), then 1231 the Forwarding Contraindicated procedure defined in Section 5.4.1 1232 MUST be followed; the remaining steps of Section 5.4 are skipped at 1233 this time. 1235 Step 4: For each node selected for forwarding, the bundle protocol 1236 agent MUST invoke the services of the selected convergence layer 1237 adapter(s) in order to effect the sending of the bundle to that 1238 node. Determining the time at which the bundle protocol agent 1239 invokes convergence layer adapter services is a BPA implementation 1240 matter. Determining the time at which each convergence layer 1241 adapter subsequently responds to this service invocation by sending 1242 the bundle is a convergence-layer adapter implementation matter. 1243 Note that: 1245 . If the bundle has a Previous Node block, as defined in 4.3.1 1246 above, then that block MUST be removed from the bundle before 1247 the bundle is forwarded. 1248 . If the bundle protocol agent is configured to attach Previous 1249 Node blocks to forwarded bundles, then a Previous Node block 1250 containing the node ID of the forwarding node MUST be inserted 1251 into the bundle before the bundle is forwarded. 1252 . If the bundle has a bundle age block, as defined in 4.3.2. 1253 above, then at the last possible moment before the CLA 1254 initiates conveyance of the bundle via the CL protocol the 1255 bundle age value MUST be increased by the difference between 1256 the current time and the time at which the bundle was received 1257 (or, if the local node is the source of the bundle, created). 1259 Step 5: When all selected convergence layer adapters have informed 1260 the bundle protocol agent that they have concluded their data 1261 sending procedures with regard to this bundle, processing may depend 1262 on the results of those procedures. If completion of the data 1263 sending procedures by all selected convergence layer adapters has 1264 not resulted in successful forwarding of the bundle (an 1265 implementation-specific determination that is beyond the scope of 1266 this specification), then the bundle protocol agent MAY choose (in 1267 an implementation-specific manner, again beyond the scope of this 1268 specification) to initiate another attempt to forward the bundle. 1269 In that event, processing proceeds from Step 4 of Section 5.4. 1271 If completion of the data sending procedures by all selected 1272 convergence layer adapters HAS resulted in successful forwarding of 1273 the bundle, or if it has not but the bundle protocol agent does not 1274 choose to initiate another attempt to forward the bundle, then: 1276 . If the "request reporting of bundle forwarding" flag in the 1277 bundle's status report request field is set to 1, and status 1278 reporting is enabled, then a bundle forwarding status report 1279 SHOULD be generated, destined for the bundle's report-to 1280 endpoint ID. The reason code on this bundle forwarding status 1281 report MUST be "no additional information". 1282 . If any applicable bundle protocol extensions mandate generation 1283 of status reports upon conclusion of convergence-layer data 1284 sending procedures, all such status reports SHOULD be generated 1285 with extension-mandated reason codes. 1286 . The bundle's "Forward pending" retention constraint MUST be 1287 removed. 1289 5.4.1. Forwarding Contraindicated 1291 The steps in responding to contraindication of forwarding are: 1293 Step 1: The bundle protocol agent MUST determine whether or not to 1294 declare failure in forwarding the bundle. Note: this decision is 1295 likely to be influenced by the reason for which forwarding is 1296 contraindicated. 1298 Step 2: If forwarding failure is declared, then the Forwarding 1299 Failed procedure defined in Section 5.4.2 MUST be followed. 1301 Otherwise, when - at some future time - the forwarding of this 1302 bundle ceases to be contraindicated, processing proceeds from Step 4 1303 of Section 5.4. 1305 5.4.2. Forwarding Failed 1307 The steps in responding to a declaration of forwarding failure are: 1309 Step 1: The bundle protocol agent MAY forward the bundle back to the 1310 node that sent it, as identified by the Previous Node block, if 1311 present. This forwarding, if performed, SHALL be accomplished by 1312 performing Step 4 and Step 5 of section 5.4 where the sole node 1313 selected for forwarding SHALL be the node that sent the bundle. 1315 Step 2: If the bundle's destination endpoint is an endpoint of which 1316 the node is a member, then the bundle's "Forward pending" retention 1317 constraint MUST be removed. Otherwise, the bundle MUST be deleted: 1318 the bundle deletion procedure defined in Section 5.10 MUST be 1319 followed, citing the reason for which forwarding was determined to 1320 be contraindicated. 1322 5.5. Bundle Expiration 1324 A bundle expires when the bundle's age exceeds its lifetime as 1325 specified in the primary bundle block. Bundle age MAY be determined 1326 by subtracting the bundle's creation timestamp time from the current 1327 time if (a) that timestamp time is not zero and (b) the local node's 1328 clock is known to be accurate; otherwise bundle age MUST be obtained 1329 from the Bundle Age extension block. Bundle expiration MAY occur at 1330 any point in the processing of a bundle. When a bundle expires, the 1331 bundle protocol agent MUST delete the bundle for the reason 1332 "lifetime expired": the bundle deletion procedure defined in Section 1333 5.10 MUST be followed. 1335 5.6. Bundle Reception 1337 The steps in processing a bundle that has been received from another 1338 node are: 1340 Step 1: The retention constraint "Dispatch pending" MUST be added to 1341 the bundle. 1343 Step 2: If the "request reporting of bundle reception" flag in the 1344 bundle's status report request field is set to 1, and status 1345 reporting is enabled, then a bundle reception status report with 1346 reason code "No additional information" SHOULD be generated, 1347 destined for the bundle's report-to endpoint ID. 1349 Step 3: CRCs SHOULD be computed for every block of the bundle that 1350 has an attached CRC. If any block of the bundle is malformed 1351 according to this specification (including syntactically invalid 1352 CBOR), or if any block has an attached CRC and the CRC computed for 1353 this block upon reception differs from that attached CRC, then the 1354 bundle protocol agent MUST delete the bundle for the reason "Block 1355 unintelligible". The bundle deletion procedure defined in Section 1356 5.10 MUST be followed and all remaining steps of the bundle 1357 reception procedure MUST be skipped. 1359 Step 4: For each block in the bundle that is an extension block that 1360 the bundle protocol agent cannot process: 1362 . If the block processing flags in that block indicate that a 1363 status report is requested in this event, and status reporting 1364 is enabled, then a bundle reception status report with reason 1365 code "Block unintelligible" SHOULD be generated, destined for 1366 the bundle's report-to endpoint ID. 1367 . If the block processing flags in that block indicate that the 1368 bundle must be deleted in this event, then the bundle protocol 1369 agent MUST delete the bundle for the reason "Block 1370 unintelligible"; the bundle deletion procedure defined in 1371 Section 5.10 MUST be followed and all remaining steps of the 1372 bundle reception procedure MUST be skipped. 1373 . If the block processing flags in that block do NOT indicate 1374 that the bundle must be deleted in this event but do indicate 1375 that the block must be discarded, then the bundle protocol 1376 agent MUST remove this block from the bundle. 1377 . If the block processing flags in that block indicate neither 1378 that the bundle must be deleted nor that that the block must be 1379 discarded, then processing continues with the next extension 1380 block that the bundle protocol agent cannot process, if any; 1381 otherwise, processing proceeds from step 5. 1383 Step 5: Processing proceeds from Step 1 of Section 5.3. 1385 5.7. Local Bundle Delivery 1387 The steps in processing a bundle that is destined for an endpoint of 1388 which this node is a member are: 1390 Step 1: If the received bundle is a fragment, the application data 1391 unit reassembly procedure described in Section 5.9 MUST be followed. 1392 If this procedure results in reassembly of the entire original 1393 application data unit, processing of this bundle (whose fragmentary 1394 payload has been replaced by the reassembled application data unit) 1395 proceeds from Step 2; otherwise, the retention constraint 1396 "Reassembly pending" MUST be added to the bundle and all remaining 1397 steps of this procedure MUST be skipped. 1399 Step 2: Delivery depends on the state of the registration whose 1400 endpoint ID matches that of the destination of the bundle: 1402 . An additional implementation-specific delivery deferral 1403 procedure MAY optionally be associated with the registration. 1404 . If the registration is in the Active state, then the bundle 1405 MUST be delivered automatically as soon as it is the next 1406 bundle that is due for delivery according to the BPA's bundle 1407 delivery scheduling policy, an implementation matter. 1408 . If the registration is in the Passive state, or if delivery of 1409 the bundle fails for some implementation-specific reason, then 1410 the registration's delivery failure action MUST be taken. 1411 Delivery failure action MUST be one of the following: 1413 o defer delivery of the bundle subject to this registration 1414 until (a) this bundle is the least recently received of 1415 all bundles currently deliverable subject to this 1416 registration and (b) either the registration is polled or 1417 else the registration is in the Active state, and also 1418 perform any additional delivery deferral procedure 1419 associated with the registration; or 1421 o abandon delivery of the bundle subject to this registration 1422 (as defined in 3.1. ). 1424 Step 3: As soon as the bundle has been delivered, if the "request 1425 reporting of bundle delivery" flag in the bundle's status report 1426 request field is set to 1 and bundle status reporting is enabled, 1427 then a bundle delivery status report SHOULD be generated, destined 1428 for the bundle's report-to endpoint ID. Note that this status report 1429 only states that the payload has been delivered to the application 1430 agent, not that the application agent has processed that payload. 1432 5.8. Bundle Fragmentation 1434 It may at times be advantageous for bundle protocol agents to reduce 1435 the sizes of bundles in order to forward them. This might be the 1436 case, for example, if a node to which a bundle is to be forwarded is 1437 accessible only via intermittent contacts and no upcoming contact is 1438 long enough to enable the forwarding of the entire bundle. 1440 The size of a bundle can be reduced by "fragmenting" the bundle. To 1441 fragment a bundle whose payload is of size M is to replace it with 1442 two "fragments" -- new bundles with the same source node ID and 1443 creation timestamp as the original bundle -- whose payloads are the 1444 first N and the last (M - N) bytes of the original bundle's payload, 1445 where 0 < N < M. 1447 Note that fragments are bundles and therefore may themselves be 1448 fragmented, so multiple episodes of fragmentation may in effect 1449 replace the original bundle with more than two fragments. (However, 1450 there is only one 'level' of fragmentation, as in IP fragmentation.) 1452 Any bundle whose primary block's bundle processing flags do NOT 1453 indicate that it must not be fragmented MAY be fragmented at any 1454 time, for any purpose, at the discretion of the bundle protocol 1455 agent. NOTE, however, that some combinations of bundle 1456 fragmentation, replication, and routing might result in unexpected 1457 traffic patterns. 1459 Fragmentation SHALL be constrained as follows: 1461 . The concatenation of the payloads of all fragments produced by 1462 fragmentation MUST always be identical to the payload of the 1463 fragmented bundle (that is, the bundle that is being 1464 fragmented). Note that the payloads of fragments resulting from 1465 different fragmentation episodes, in different parts of the 1466 network, may be overlapping subsets of the fragmented bundle's 1467 payload. 1468 . The primary block of each fragment MUST differ from that of the 1469 fragmented bundle, in that the bundle processing flags of the 1470 fragment MUST indicate that the bundle is a fragment and both 1471 fragment offset and total application data unit length must be 1472 provided. Additionally, the CRC of the primary block of the 1473 fragmented bundle, if any, MUST be replaced in each fragment by 1474 a new CRC computed for the primary block of that fragment. 1475 . The payload blocks of fragments will differ from that of the 1476 fragmented bundle as noted above. 1477 . If the fragmented bundle is not a fragment or is the fragment 1478 with offset zero, then all extension blocks of the fragmented 1479 bundle MUST be replicated in the fragment whose offset is zero. 1480 . Each of the fragmented bundle's extension blocks whose "Block 1481 must be replicated in every fragment" flag is set to 1 MUST be 1482 replicated in every fragment. 1483 . Beyond these rules, replication of extension blocks in the 1484 fragments is an implementation matter. 1486 5.9. Application Data Unit Reassembly 1488 If the concatenation -- as informed by fragment offsets and payload 1489 lengths -- of the non-overlapping portions of the payloads of all 1490 previously received fragments with the same source node ID and 1491 creation timestamp as this fragment, together with the non- 1492 overlapping portion of the payload of this fragment, forms a byte 1493 array whose length is equal to the total application data unit 1494 length in the fragment's primary block, then: 1496 . This byte array -- the reassembled application data unit -- 1497 MUST replace the payload of this fragment. 1498 . The "Reassembly pending" retention constraint MUST be removed 1499 from every other fragment whose payload is a subset of the 1500 reassembled application data unit. 1502 Note: reassembly of application data units from fragments occurs at 1503 the nodes that are members of destination endpoints as necessary; an 1504 application data unit MAY also be reassembled at some other node on 1505 the path to the destination. 1507 5.10. Bundle Deletion 1509 The steps in deleting a bundle are: 1511 Step 1: If the "request reporting of bundle deletion" flag in the 1512 bundle's status report request field is set to 1, and if status 1513 reporting is enabled, then a bundle deletion status report citing 1514 the reason for deletion SHOULD be generated, destined for the 1515 bundle's report-to endpoint ID. 1517 Step 2: All of the bundle's retention constraints MUST be removed. 1519 5.11. Discarding a Bundle 1521 As soon as a bundle has no remaining retention constraints it MAY be 1522 discarded, thereby releasing any persistent storage that may have 1523 been allocated to it. 1525 5.12. Canceling a Transmission 1527 When requested to cancel a specified transmission, where the bundle 1528 created upon initiation of the indicated transmission has not yet 1529 been discarded, the bundle protocol agent MUST delete that bundle 1530 for the reason "transmission cancelled". For this purpose, the 1531 procedure defined in Section 5.10 MUST be followed. 1533 6. Administrative Record Processing 1535 6.1. Administrative Records 1537 Administrative records are standard application data units that are 1538 used in providing some of the features of the Bundle Protocol. One 1539 type of administrative record has been defined to date: bundle 1540 status reports. Note that additional types of administrative 1541 records may be defined by supplementary DTN protocol specification 1542 documents. 1544 Every administrative record consists of: 1546 . Record type code (an unsigned integer for which valid values 1547 are as defined below). 1548 . Record content in type-specific format. 1550 Valid administrative record type codes are defined as follows: 1552 +---------+--------------------------------------------+ 1554 | Value | Meaning | 1556 +=========+============================================+ 1558 | 1 | Bundle status report. | 1560 +---------+--------------------------------------------+ 1562 | (other) | Reserved for future use. | 1564 +---------+--------------------------------------------+ 1566 Figure 3: Administrative Record Type Codes 1568 Each BP administrative record SHALL be represented as a CBOR array 1569 comprising a 2-tuple. 1571 The first item of the array SHALL be a record type code, which SHALL 1572 be represented as a CBOR unsigned integer. 1574 The second element of this array SHALL be the applicable CBOR 1575 representation of the content of the record. Details of the CBOR 1576 representation of administrative record type 1 are provided below. 1577 Details of the CBOR representation of other types of administrative 1578 record type are included in the specifications defining those 1579 records. 1581 6.1.1. Bundle Status Reports 1583 The transmission of "bundle status reports" under specified 1584 conditions is an option that can be invoked when transmission of a 1585 bundle is requested. These reports are intended to provide 1586 information about how bundles are progressing through the system, 1587 including notices of receipt, forwarding, final delivery, and 1588 deletion. They are transmitted to the Report-to endpoints of 1589 bundles. 1591 Each bundle status report SHALL be represented as a CBOR array. The 1592 number of elements in the array SHALL be either 6 (if the subject 1593 bundle is a fragment) or 4 (otherwise). 1595 The first item of the bundle status report array SHALL be bundle 1596 status information represented as a CBOR array of at least 4 1597 elements. The first four items of the bundle status information 1598 array shall provide information on the following four status 1599 assertions, in this order: 1601 . Reporting node received bundle. 1602 . Reporting node forwarded the bundle. 1603 . Reporting node delivered the bundle. 1604 . Reporting node deleted the bundle. 1606 Each item of the bundle status information array SHALL be a bundle 1607 status item represented as a CBOR array; the number of elements in 1608 each such array SHALL be either 2 (if the value of the first item of 1609 this bundle status item is 1 AND the "Report status time" flag was 1610 set to 1 in the bundle processing flags of the bundle whose status 1611 is being reported) or 1 (otherwise). The first item of the bundle 1612 status item array SHALL be a status indicator, a Boolean value 1613 indicating whether or not the corresponding bundle status is 1614 asserted, represented as a CBOR Boolean value. The second item of 1615 the bundle status item array, if present, SHALL indicate the time 1616 (as reported by the local system clock, an implementation matter) at 1617 which the indicated status was asserted for this bundle, represented 1618 as a DTN time as described in Section 4.1.6. above. 1620 The second item of the bundle status report array SHALL be the 1621 bundle status report reason code explaining the value of the status 1622 indicator, represented as a CBOR unsigned integer. Valid status 1623 report reason codes are registered in the IANA Bundle Status Report 1624 Reason Codes registry in the Bundle Protocol Namespace (see 10.5 1625 below). The initial contents of that registry are listed in Figure 1626 4 below but the list of status report reason codes provided here is 1627 neither exhaustive nor exclusive; supplementary DTN protocol 1628 specifications (including, but not restricted to, the Bundle 1629 Security Protocol [BPSEC]) may define additional reason codes. 1631 +---------+--------------------------------------------+ 1633 | Value | Meaning | 1634 +=========+============================================+ 1636 | 0 | No additional information. | 1638 +---------+--------------------------------------------+ 1640 | 1 | Lifetime expired. | 1642 +---------+--------------------------------------------+ 1644 | 2 | Forwarded over unidirectional link. | 1646 +---------+--------------------------------------------+ 1648 | 3 | Transmission canceled. | 1650 +---------+--------------------------------------------+ 1652 | 4 | Depleted storage. | 1654 +---------+--------------------------------------------+ 1656 | 5 | Destination endpoint ID unavailable. | 1658 +---------+--------------------------------------------+ 1660 | 6 | No known route to destination from here. | 1662 +---------+--------------------------------------------+ 1664 | 7 | No timely contact with next node on route. | 1666 +---------+--------------------------------------------+ 1668 | 8 | Block unintelligible. | 1670 +---------+--------------------------------------------+ 1672 | 9 | Hop limit exceeded. | 1674 +---------+--------------------------------------------+ 1676 | 10 | Traffic pared (e.g., status reports). | 1678 +---------+--------------------------------------------+ 1680 | (other) | Reserved for future use. | 1681 +---------+--------------------------------------------+ 1683 Figure 4: Status Report Reason Codes 1685 The third item of the bundle status report array SHALL be the source 1686 node ID identifying the source of the bundle whose status is being 1687 reported, represented as described in Section 4.1.5.2. above. 1689 The fourth item of the bundle status report array SHALL be the 1690 creation timestamp of the bundle whose status is being reported, 1691 represented as described in Section 4.1.7. above. 1693 The fifth item of the bundle status report array SHALL be present if 1694 and only if the bundle whose status is being reported contained a 1695 fragment offset. If present, it SHALL be the subject bundle's 1696 fragment offset represented as a CBOR unsigned integer item. 1698 The sixth item of the bundle status report array SHALL be present if 1699 and only if the bundle whose status is being reported contained a 1700 fragment offset. If present, it SHALL be the length of the subject 1701 bundle's payload represented as a CBOR unsigned integer item. 1703 Note that the forwarding parameters (such as lifetime, applicable 1704 security measures, etc.) of the bundle whose status is being 1705 reported MAY be reflected in the parameters governing the forwarding 1706 of the bundle that conveys a status report, but this is an 1707 implementation matter. Bundle protocol deployment experience to 1708 date has not been sufficient to suggest any clear guidance on this 1709 topic. 1711 6.2. Generation of Administrative Records 1713 Whenever the application agent's administrative element is directed 1714 by the bundle protocol agent to generate an administrative record, 1715 the following procedure must be followed: 1717 Step 1: The administrative record must be constructed. If the 1718 administrative record references a bundle and the referenced bundle 1719 is a fragment, the administrative record MUST contain the fragment 1720 offset and fragment length. 1722 Step 2: A request for transmission of a bundle whose payload is this 1723 administrative record MUST be presented to the bundle protocol 1724 agent. 1726 7. Services Required of the Convergence Layer 1728 7.1. The Convergence Layer 1730 The successful operation of the end-to-end bundle protocol depends 1731 on the operation of underlying protocols at what is termed the 1732 "convergence layer"; these protocols accomplish communication 1733 between nodes. A wide variety of protocols may serve this purpose, 1734 so long as each convergence layer protocol adapter provides a 1735 defined minimal set of services to the bundle protocol agent. This 1736 convergence layer service specification enumerates those services. 1738 7.2. Summary of Convergence Layer Services 1740 Each convergence layer protocol adapter is expected to provide the 1741 following services to the bundle protocol agent: 1743 . sending a bundle to a bundle node that is reachable via the 1744 convergence layer protocol; 1745 . notifying the bundle protocol agent when it has concluded its 1746 data sending procedures with regard to a bundle; 1747 . delivering to the bundle protocol agent a bundle that was sent 1748 by a bundle node via the convergence layer protocol. 1750 The convergence layer service interface specified here is neither 1751 exhaustive nor exclusive. That is, supplementary DTN protocol 1752 specifications (including, but not restricted to, the Bundle 1753 Security Protocol [BPSEC]) may expect convergence layer adapters 1754 that serve BP implementations conforming to those protocols to 1755 provide additional services such as reporting on the transmission 1756 and/or reception progress of individual bundles (at completion 1757 and/or incrementally), retransmitting data that were lost in 1758 transit, discarding bundle-conveying data units that the convergence 1759 layer protocol determines are corrupt or inauthentic, or reporting 1760 on the integrity and/or authenticity of delivered bundles. 1762 In addition, bundle protocol relies on the capabilities of protocols 1763 at the convergence layer to minimize congestion in the store-carry- 1764 forward overlay network. The potentially long round-trip times 1765 characterizing delay-tolerant networks are incompatible with end-to- 1766 end reactive congestion control mechanisms, so convergence-layer 1767 protocols MUST provide rate limiting or congestion control. 1769 Implementation of the TCP convergence-layer adapter [TCPCL] is 1770 mandatory. 1772 8. Implementation Status 1774 [NOTE to the RFC Editor: please remove this section before 1775 publication, as well as the reference to RFC 7942.] 1777 This section records the status of known implementations of the 1778 protocol defined by this specification at the time of posting of 1779 this Internet-Draft, and is based on a proposal described in RFC 1780 7942. The description of implementations in this section is 1781 intended to assist the IETF in its decision processes in progressing 1782 drafts to RFCs. Please note that the listing of any individual 1783 implementation here does not imply endorsement by the IETF. 1784 Furthermore, no effort has been spent to verify the information 1785 presented here that was supplied by IETF contributors. This is not 1786 intended as, and must not be construed to be, a catalog of available 1787 implementations or their features. Readers are advised to note that 1788 other implementations may exist. 1790 According to RFC 7942, "this will allow reviewers and working groups 1791 to assign due consideration to documents that have the benefit of 1792 running code, which may serve as evidence of valuable 1793 experimentation and feedback that have made the implemented 1794 protocols more mature. It is up to the individual working groups to 1795 use this information as they see fit". 1797 At the time of this writing, there are three known implementations 1798 of the current document. 1800 The first known implementation is microPCN (https://upcn.eu/). 1801 According to the developers: 1803 The Micro Planetary Communication Network (uPCN) is a free 1804 software project intended to offer an implementation of Delay- 1805 tolerant Networking protocols for POSIX operating systems (well, 1806 and for Linux) plus for the ARM Cortex STM32F4 microcontroller 1807 series. More precisely it currently provides an implementation of 1809 . the Bundle Protocol (BP, RFC 5050), 1810 . version 6 of the Bundle Protocol version 7 specification 1811 draft, 1812 . the DTN IP Neighbor Discovery (IPND) protocol, and 1813 . a routing approach optimized for message-ferry micro LEO 1814 satellites. 1816 uPCN is written in C and is built upon the real-time operating 1817 system FreeRTOS. The source code of uPCN is released under the 1818 "BSD 3-Clause License". 1820 The project depends on an execution environment offering link 1821 layer protocols such as AX.25. The source code uses the USB 1822 subsystem to interact with the environment. 1824 The second known implementation is PyDTN, developed by X-works, 1825 s.r.o (https://x-works.sk/). The final third of the implementation 1826 was developed during the IETF 101 Hackathon. According to the 1827 developers, PyDTN implements bundle coding/decoding and neighbor 1828 discovery. PyDTN is written in Python and has been shown to be 1829 interoperable with uPCN. 1831 The third known implementation is "Terra" 1832 (https://github.com/RightMesh/Terra/), a Java implementation 1833 developed in the context of terrestrial DTN. It includes an 1834 implementation of a "minimal TCP" convergence layer adapter. 1836 9. Security Considerations 1838 The bundle protocol security architecture and the available security 1839 services are specified in an accompanying document, the Bundle 1840 Security Protocol specification [BPSEC]. 1842 The BPsec extensions to Bundle Protocol enable each block of a 1843 bundle (other than a BPsec extension block) to be individually 1844 authenticated by a signature block (Block Integrity Block, or BIB) 1845 and also enable each block of a bundle other than the primary block 1846 (and the BPsec extension blocks themselves) to be individually 1847 encrypted by a BCB. 1849 Because the security mechanisms are extension blocks that are 1850 themselves inserted into the bundle, the protections they afford 1851 apply while the bundle is at rest, awaiting transmission at the next 1852 forwarding opportunity, as well as in transit. 1854 Additionally, convergence-layer protocols that ensure authenticity 1855 of communication between adjacent nodes in BP network topology 1856 SHOULD be used where available, to minimize the ability of 1857 unauthenticated nodes to introduce inauthentic traffic into the 1858 network. Convergence-layer protocols that ensure confidentiality of 1859 communication between adjacent nodes in BP network topology SHOULD 1860 also be used where available, to minimize exposure of the bundle's 1861 primary block and other clear-text blocks, thereby offering some 1862 defense against traffic analysis. 1864 Note that, while the primary block must remain in the clear for 1865 routing purposes, the Bundle Protocol could be protected against 1866 traffic analysis to some extent by using bundle-in-bundle 1867 encapsulation [BIBE] to tunnel bundles to a safe forward 1868 distribution point: the encapsulated bundle could form the payload 1869 of an encapsulating bundle, and that payload block could be 1870 encrypted by a BCB. 1872 Note that the generation of bundle status reports is disabled by 1873 default because malicious initiation of bundle status reporting 1874 could result in the transmission of extremely large numbers of 1875 bundles, effecting a denial of service attack. Imposing bundle 1876 lifetime overrides would constitute one defense against such an 1877 attack. 1879 Note also that the reception of large numbers of fragmentary nodes 1880 with very long lifetimes could constitute a denial of service 1881 attack, occupying storage while pending reassembly that will never 1882 occur. Imposing bundle lifetime overrides would constitute one 1883 defense against such an attack. 1885 10. IANA Considerations 1887 The Bundle Protocol includes fields requiring registries managed by 1888 IANA. 1890 10.1. Bundle Block Types 1892 The current Bundle Block Types registry in the Bundle Protocol 1893 Namespace is augmented by adding a column identifying the version of 1894 the Bundle protocol (Bundle Protocol Version) that applies to the 1895 new values. IANA is requested to add the following values, as 1896 described in section 4.3.1, to the Bundle Block Types registry. The 1897 current values in the Bundle Block Types registry should have the 1898 Bundle Protocol Version set to the value "6", as shown below. 1900 +----------+-------+-----------------------------+---------------+ 1902 | Bundle | Value | Description | Reference | 1904 | Protocol | | | | 1906 | Version | | | | 1908 +----------+-------+-----------------------------+---------------+ 1910 | none | 0 | Reserved | [RFC6255] | 1912 | 6,7 | 1 | Bundle Payload Block | [RFC5050] | 1913 | | | | RFC-to-be | 1915 | 6 | 2 | Bundle Authentication Block | [RFC6257] | 1917 | 6 | 3 | Payload Integrity Block | [RFC6257] | 1919 | 6 | 4 | Payload Confidentiality | [RFC6257] | 1921 | | | Block | RFC-to-be | 1923 | 6 | 5 | Previous-Hop Insertion Block| [RFC6259] | 1925 | 7 | 6 | Previous node (proximate | RFC-to-be | 1927 | | | sender) | | 1929 | 7 | 7 | Bundle age (in seconds) | RFC-to-be | 1931 | 6 | 8 | Metadata Extension Block | [RFC6258] | 1933 | 6 | 9 | Extension Security Block | [RFC6257] | 1935 | 7 | 10 | Hop count (#prior xmit | RFC-to-be | 1937 | | | attempts) | | 1939 | 7 | 11-191| Unassigned | | 1941 | 6 |192-255| Reserved for Private and/or | [RFC5050], | 1943 | | | Experimental Use | RFC-to-be | 1945 +----------+-------+-----------------------------+---------------+ 1947 10.2. Primary Bundle Protocol Version 1949 IANA is requested to add the following value to the Primary Bundle 1950 Protocol Version registry in the Bundle Protocol Namespace. 1952 +-------+-------------+---------------+ 1954 | Value | Description | Reference | 1956 +-------+-------------+---------------+ 1958 | 7 | Assigned | RFC-to-be | 1959 +-------+-------------+---------------+ 1961 10.3. Bundle Processing Control Flags 1963 The current Bundle Processing Control Flags registry in the Bundle 1964 Protocol Namespace is augmented by adding a column identifying the 1965 version of the Bundle protocol (Bundle Protocol Version) that 1966 applies to the new values. IANA is requested to add the following 1967 values, as described in section 4.1.3, to the Bundle Processing 1968 Control Flags registry. The current values in the Bundle Processing 1969 Control Flags registry should have the Bundle Protocol Version set 1970 to the value 6 or "6, 7", as shown below. 1972 Bundle Processing Control Flags Registry 1974 +--------------------+----------------------------------+----------+ 1976 | Bundle | Bit | Description | Reference| 1978 | Protocol| Position | | | 1980 | Version | (right | | | 1982 | | to left) | | | 1984 +--------------------+----------------------------------+----------+ 1986 | 6,7 | 0 | Bundle is a fragment |[RFC5050],| 1988 | | | |RFC-to-be | 1990 | 6,7 | 1 | Application data unit is an |[RFC5050],| 1992 | | | administrative record |RFC-to-be | 1994 | 6,7 | 2 | Bundle must not be fragmented |[RFC5050],| 1996 | | | |RFC-to-be | 1998 | 6 | 3 | Custody transfer is requested |[RFC5050] | 2000 | 6 | 4 | Destination endpoint is singleton|[RFC5050] | 2002 | 6,7 | 5 | Acknowledgement by application |[RFC5050],| 2004 | | | is requested |RFC-to-be | 2005 | 7 | 6 | Status time requested in reports |RFC-to-be | 2007 | 6 | 7 | Class of service, priority |[RFC5050],| 2009 | | | |RFC-to-be | 2011 | 6 | 8 | Class of service, priority |[RFC5050],| 2013 | | | |RFC-to-be | 2015 | 6 | 9 | Class of service, reserved |[RFC5050],| 2017 | | | |RFC-to-be | 2019 | 6 | 10 | Class of service, reserved |[RFC5050],| 2021 | | | |RFC-to-be | 2023 | 6 | 11 | Class of service, reserved |[RFC5050],| 2025 | | | |RFC-to-be | 2027 | 6 | 12 | Class of service, reserved |[RFC5050],| 2029 | | | |RFC-to-be | 2031 | 6 | 13 | Class of service, reserved |[RFC5050],| 2033 | | | |RFC-to-be | 2035 | 6,7 | 14 | Request reporting of bundle |[RFC5050],| 2037 | | | reception |RFC-to-be | 2039 | 6,7 | 16 | Request reporting of bundle |[RFC5050],| 2041 | | | forwarding |RFC-to-be | 2043 | 6,7 | 17 | Request reporting of bundle |[RFC5050],| 2045 | | | delivery |RFC-to-be | 2047 | 6,7 | 18 | Request reporting of bundle |[RFC5050],| 2049 | | | deletion |RFC-to-be | 2051 | 6 | 19 | Reserved |[RFC5050],| 2052 | | | |RFC-to-be | 2054 | 6 | 20 | Reserved |[RFC5050],| 2056 | | | |RFC-to-be | 2058 | | 21-63 | Unassigned | | 2060 +--------------------+----------------------------------+----------+ 2062 The registration policy for this registry is changed to "Standards 2063 Action". Given the limited number of bits available, the allocation 2064 should only be granted for a standards-track RFC approved by the 2065 IESG. 2067 10.4. Block Processing Control Flags 2069 The current Block Processing Control Flags registry in the Bundle 2070 Protocol Namespace is augmented by adding a column identifying the 2071 version of the Bundle protocol (Bundle Protocol Version) that 2072 applies to the related BP version. The current values in the Block 2073 Processing Control Flags registry should have the Bundle Protocol 2074 Version set to the value 6 or "6, 7", as shown below. 2076 Block Processing Control Flags Registry 2078 +--------------------+----------------------------------+----------+ 2080 | Bundle | Bit | Description | Reference| 2082 | Protocol| Position | | | 2084 | Version | (right | | | 2086 | | to left) | | | 2088 +--------------------+----------------------------------+----------+ 2090 | 6,7 | 0 | Block must be replicated in |[RFC5050],| 2092 | | | every fragment |RFC-to-be | 2094 | 6,7 | 1 | Transmit status report if block |[RFC5050],| 2096 | | | can't be processed |RFC-to-be | 2098 | 6,7 | 2 | Delete bundle if block can't be |[RFC5050],| 2099 | | | processed |RFC-to-be | 2101 | 6 | 3 | Last block |[RFC5050] | 2103 | 6,7 | 4 | Discard block if it can't be |[RFC5050],| 2105 | | | processed |RFC-to-be | 2107 | 6 | 5 | Block was forwarded without |[RFC5050] | 2109 | | | being processed | | 2111 | 6 | 6 | Block contains an EID reference |[RFC5050] | 2113 | | | field | | 2115 | | 7-63 | Unassigned | | 2117 +--------------------+----------------------------------+----------+ 2119 The registration policy for this registry is changed to "Standards 2120 Action". Given the limited number of bits available, the allocation 2121 should only be granted for a standards-track RFC approved by the 2122 IESG. 2124 10.5. Bundle Status Report Reason Codes 2126 The current Bundle Status Report Reason Codes registry in the Bundle 2127 Protocol Namespace is augmented by adding a column identifying the 2128 version of the Bundle protocol (Bundle Protocol Version) that 2129 applies to the new values. IANA is requested to add the following 2130 values, as described in section 6.1.1, to the Bundle Status Report 2131 Reason Codes registry. The current values in the Bundle Status 2132 Report Reason Codes registry should have the Bundle Protocol Version 2133 set to the value 6 or 7 or "6, 7", as shown below. 2135 Bundle Status Report Reason Codes Registry 2137 +--------------------+----------------------------------+----------+ 2139 | Bundle | Value | Description | Reference| 2141 | Protocol| | | | 2143 | Version | | | | 2145 | | | | | 2146 +--------------------+----------------------------------+----------+ 2148 | 6,7 | 0 | No additional information |[RFC5050],| 2150 | | | |RFC-to-be | 2152 | 6,7 | 1 | Lifetime expired |[RFC5050],| 2154 | | | |RFC-to-be | 2156 | 6,7 | 2 | Forwarded over unidirectional |[RFC5050],| 2158 | | | link |RFC-to-be | 2160 | 6,7 | 3 | Transmission canceled |[RFC5050],| 2162 | | | |RFC-to-be | 2164 | 6,7 | 4 | Depleted storage |[RFC5050],| 2166 | | | |RFC-to-be | 2168 | 6,7 | 5 | Destination endpoint ID |[RFC5050],| 2170 | | | unavailable |RFC-to-be | 2172 | 6,7 | 6 | No known route to destination |[RFC5050],| 2174 | | | from here |RFC-to-be | 2176 | 6,7 | 7 | No timely contact with next node |[RFC5050],| 2178 | | | on route |RFC-to-be | 2180 | 6,7 | 8 | Block unintelligible |[RFC5050],| 2182 | | | |RFC-to-be | 2184 | 7 | 9 | Hop limit exceeded |RFC-to-be | 2186 | 7 | 10 | Traffic pared |RFC-to-be | 2188 | | 11-254 | Unassigned | | 2190 | 6 | 255 | Reserved |[RFC6255],| 2192 | | | |RFC-to-be | 2193 +-------+-----------------------------------------------+----------+ 2195 10.6. Bundle Protocol URI scheme types 2197 The Bundle Protocol has a URI scheme type field - an unsigned 2198 integer of indefinite length - for which IANA is requested to create 2199 and maintain a new "Bundle Protocol URI Scheme Type" registry in the 2200 Bundle Protocol Namespace. The "Bundle Protocol URI Scheme Type" 2201 registry governs an 8-bit namespace. Initial values for the Bundle 2202 Protocol URI Scheme Type registry are given below. 2204 The registration policy for this registry is: Standards Action. 2205 Given the limited number of bits available, the allocation should 2206 only be granted for a standards-track RFC approved by the IESG. 2208 The value range is: unsigned 8-bit integer. 2210 Each assignment consists of a URI scheme type name and its 2211 associated description, a reference to the document that defines the 2212 URI scheme, and a reference to the document that defines the use of 2213 this URI scheme in BP endpoint IDs (including the CBOR 2214 representation of those endpoint IDs in transmitted bundles). 2216 Bundle Protocol URI Scheme Type Registry 2218 +---------+-------------+----------------+------------------+ 2220 | | | BP Utilization | URI Definition | 2222 | Value | Description | Reference | Reference | 2224 +---------+-------------+----------------+------------------+ 2226 | 0 | Reserved | n/a | | 2228 | 1 | dtn | RFC-to-be | RFC-to-be | 2230 | 2 | ipn | RFC-to-be | [RFC6260], | 2232 | | | | RFC-to-be | 2234 | 3-254 | Unassigned | n/a | | 2236 | 255 | reserved | n/a | | 2238 +---------+-------------+----------------+------------------+ 2240 10.7. URI scheme "dtn" 2242 IANA is requested to update the registration of the URI scheme with 2243 the string "dtn" as the scheme name, as follows: 2245 URI scheme name: "dtn" 2247 Status: permanent 2249 URI scheme syntax: 2251 This specification uses the Augmented Backus-Naur Form (ABNF) 2252 notation of [RFC5234]. 2254 dtn-uri = "dtn:" dtn-hier-part 2256 dtn-hier-part = "//" node-name name-delim demux ; a path-rootless 2258 node-name = 1*VCHAR 2260 name-delim = "/" 2262 demux = *VCHAR 2264 URI scheme semantics: URIs of the DTN scheme are used as endpoint 2265 identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol 2266 (BP) as described in the present document. 2268 Encoding considerations: URIs of the dtn scheme are encoded 2269 exclusively in US-ASCII characters. 2271 Applications and/or protocols that use this URI scheme name: the 2272 Delay-Tolerant Networking (DTN) Bundle Protocol (BP). 2274 Interoperability considerations: as noted above, URIs of the DTN 2275 scheme are encoded exclusively in US-ASCII characters. 2277 Security considerations: 2279 . Reliability and consistency: none of the BP endpoints 2280 identified by the URIs of the DTN scheme are guaranteed to be 2281 reachable at any time, and the identity of the processing 2282 entities operating on those endpoints is never guaranteed by 2283 the Bundle Protocol itself. Bundle authentication as defined by 2284 the Bundle Security Protocol is required for this purpose. 2286 . Malicious construction: malicious construction of a conformant 2287 DTN-scheme URI is limited to the malicious selection of node 2288 names and the malicious selection of demux strings. That is, a 2289 maliciously constructed DTN-scheme URI could be used to direct 2290 a bundle to an endpoint that might be damaged by the arrival of 2291 that bundle or, alternatively, to declare a false source for a 2292 bundle and thereby cause incorrect processing at a node that 2293 receives the bundle. In both cases (and indeed in all bundle 2294 processing), the node that receives a bundle should verify its 2295 authenticity and validity before operating on it in any way. 2296 . Back-end transcoding: the limited expressiveness of URIs of the 2297 DTN scheme effectively eliminates the possibility of threat due 2298 to errors in back-end transcoding. 2299 . Rare IP address formats: not relevant, as IP addresses do not 2300 appear anywhere in conformant DTN-scheme URIs. 2301 . Sensitive information: because DTN-scheme URIs are used only to 2302 represent the identities of Bundle Protocol endpoints, the risk 2303 of disclosure of sensitive information due to interception of 2304 these URIs is minimal. Examination of DTN-scheme URIs could be 2305 used to support traffic analysis; where traffic analysis is a 2306 plausible danger, bundles should be conveyed by secure 2307 convergence-layer protocols that do not expose endpoint IDs. 2308 . Semantic attacks: the simplicity of DTN-scheme URI syntax 2309 minimizes the possibility of misinterpretation of a URI by a 2310 human user. 2312 Contact: 2314 Scott Burleigh 2316 Jet Propulsion Laboratory, 2318 California Institute of Technology 2320 scott.c.burleigh@jpl.nasa.gov 2322 +1 (800) 393-3353 2324 Change controller: 2326 IETF, iesg@ietf.org 2328 10.8. URI scheme "ipn" 2330 IANA is requested to update the registration of the URI scheme with 2331 the string "ipn" as the scheme name, originally documented in RFC 2332 6260 [RFC6260], as follows. 2334 URI scheme name: "ipn" 2336 Status: permanent 2338 URI scheme syntax: 2340 This specification uses the Augmented Backus-Naur Form (ABNF) 2341 notation of [RFC5234], including the core ABNF syntax rule for DIGIT 2342 defined by that specification. 2344 ipn-uri = "ipn:" ipn-hier-part 2346 ipn-hier-part = node-nbr nbr-delim service-nbr ; a path-rootless 2348 node-nbr = 1*DIGIT 2350 nbr-delim = "." 2352 service-nbr = 1*DIGIT 2354 URI scheme semantics: URIs of the ipn scheme are used as endpoint 2355 identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol 2356 (BP) as described in the present document. All BP endpoints 2357 identified by URIs formed in the ipn scheme are singleton endpoints. 2359 Encoding considerations: URIs of the IPN scheme are encoded 2360 exclusively in US-ASCII characters. 2362 Applications and/or protocols that use this URI scheme name: the 2363 Delay-Tolerant Networking (DTN) Bundle Protocol (BP). 2365 Interoperability considerations: as noted above, URIs of the IPN 2366 scheme are encoded exclusively in US-ASCII characters. 2368 Security considerations: 2370 . Reliability and consistency: none of the BP endpoints 2371 identified by the URIs of the IPN scheme are guaranteed to be 2372 reachable at any time, and the identity of the processing 2373 entities operating on those endpoints is never guaranteed by 2374 the Bundle Protocol itself. Bundle authentication as defined by 2375 the Bundle Security Protocol [BPSEC] is required for this 2376 purpose. 2377 . Malicious construction: malicious construction of a conformant 2378 IPN-scheme URI is limited to the malicious selection of node 2379 numbers and the malicious selection of service numbers. That 2380 is, a maliciously constructed IPN-scheme URI could be used to 2381 direct a bundle to an endpoint that might be damaged by the 2382 arrival of that bundle or, alternatively, to declare a false 2383 source for a bundle and thereby cause incorrect processing at a 2384 node that receives the bundle. In both cases (and indeed in 2385 all bundle processing), the node that receives a bundle should 2386 verify its authenticity and validity before operating on it in 2387 any way. 2388 . Back-end transcoding: the limited expressiveness of URIs of the 2389 IPN scheme effectively eliminates the possibility of threat due 2390 to errors in back-end transcoding. 2391 . Rare IP address formats: not relevant, as IP addresses do not 2392 appear anywhere in conformant IPN-scheme URIs. 2393 . Sensitive information: because IPN-scheme URIs are used only to 2394 represent the identities of Bundle Protocol endpoints, the risk 2395 of disclosure of sensitive information due to interception of 2396 these URIs is minimal. Examination of IPN-scheme URIs could be 2397 used to support traffic analysis; where traffic analysis is a 2398 plausible danger, bundles should be conveyed by secure 2399 convergence-layer protocols that do not expose endpoint IDs. 2400 . Semantic attacks: the simplicity of IPN-scheme URI syntax 2401 minimizes the possibility of misinterpretation of a URI by a 2402 human user. 2404 Contact: 2406 Scott Burleigh 2408 Jet Propulsion Laboratory, 2410 California Institute of Technology 2412 scott.c.burleigh@jpl.nasa.gov 2414 +1 (800) 393-3353 2416 Change controller: 2418 IETF, iesg@ietf.org 2420 11. References 2422 11.1. Normative References 2424 [BPSEC] Birrane, E., "Bundle Security Protocol Specification", 2425 draft-ietf-dtn-bpsec, January 2020. 2427 [CRC16] ITU-T Recommendation X.25, p. 9, section 2.2.7.4, 2428 International Telecommunications Union, October 1996. 2430 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2431 Requirement Levels", BCP 14, RFC 2119, March 1997. 2433 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 2434 4960, September 2007. 2436 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 2437 Specifications: ABNF", STD 68, RFC 5234, January 2008. 2439 [RFC7049] Borman, C. and P. Hoffman, "Concise Binary Object 2440 Representation (CBOR)", RFC 7049, October 2013. 2442 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2443 2119 Key Words", BCP 14, RFC 8174, May 2017. 2445 [SBAR] "Schedule-Aware Bundle Routing", CCSDS Recommended Standard 2446 734.3-B-1, Consultative Committee for Space Data Systems, July 2019. 2448 [TCPCL] Sipos, B., Demmer, M., Ott, J., and S. Perreault, "Delay- 2449 Tolerant Networking TCP Convergence Layer Protocol Version 4", 2450 draft-ietf-dtn-tcpclv4, January 2020. 2452 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 2453 Resource Identifier (URI): Generic Syntax", RFC 3986, STD 66, 2454 January 2005. 2456 [URIREG] Thaler, D., Hansen, T., and T. Hardie, "Guidelines and 2457 Registration Procedures for URI Schemes", RFC 7595, BCP 35, June 2458 2015. 2460 [UTC] Arias, E. and B. Guinot, "Coordinated universal time UTC: 2461 historical background and perspectives" in "Journees systemes de 2462 reference spatio-temporels", 2004. 2464 11.2. Informative References 2466 [ARCH] V. Cerf et al., "Delay-Tolerant Network Architecture", RFC 2467 4838, April 2007. 2469 [BIBE] Burleigh, S., "Bundle-in-Bundle Encapsulation", draft-ietf- 2470 dtn-bibect, August 2019. 2472 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 2473 Identifiers (IRIs)", RFC 3987, January 2005. 2475 [RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol 2476 Specification", RFC 5050, November 2007. 2478 [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol 2479 IANA Registries", RFC 6255, May 2011. 2481 [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, 2482 "Bundle Security Protocol Specification", RFC 6257, May 2011. 2484 [RFC6258] Symington, S., "Delay-Tolerant Networking Metadata 2485 Extension Block", RFC 6258, May 2011. 2487 [RFC6259] Symington, S., "Delay-Tolerant Networking Previous-Hop 2488 Insertion Block", RFC 6259, May 2011. 2490 [RFC6260] Burleigh, S., "Compressed Bundle Header Encoding (CBHE)", 2491 RFC 6260, May 2011. 2493 [RFC7143] Chadalapaka, M., Satran, J., Meth, K., and D. Black, 2494 "Internet Small Computer System Interface (iSCSI) Protocol 2495 (Consolidated)", RFC 7143, April 2014. 2497 [SIGC] Fall, K., "A Delay-Tolerant Network Architecture for 2498 Challenged Internets", SIGCOMM 2003. 2500 12. Acknowledgments 2502 This work is freely adapted from RFC 5050, which was an effort of 2503 the Delay Tolerant Networking Research Group. The following DTNRG 2504 participants contributed significant technical material and/or 2505 inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh, 2506 Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory, 2507 Michael Demmer of the University of California at Berkeley, Robert 2508 Durst, Keith Scott, and Susan Symington of The MITRE Corporation, 2509 Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity 2510 College Dublin, Howard Weiss and Peter Lovell of SPARTA, Inc., and 2511 Manikantan Ramadas of Ohio University. 2513 This document was prepared using 2-Word-v2.0.template.dot. 2515 13. Significant Changes from RFC 5050 2517 Points on which this draft significantly differs from RFC 5050 2518 include the following: 2520 . Clarify the difference between transmission and forwarding. 2522 . Migrate custody transfer to the bundle-in-bundle encapsulation 2523 specification [BIBE]. 2524 . Introduce the concept of "node ID" as functionally distinct 2525 from endpoint ID, while having the same syntax. 2526 . Restructure primary block, making it immutable. Add optional 2527 CRC. 2528 . Add optional CRCs to non-primary blocks. 2529 . Add block ID number to canonical block format (to support 2530 BPsec). 2531 . Add definition of bundle age extension block. 2532 . Add definition of previous node extension block. 2533 . Add definition of hop count extension block. 2534 . Remove Quality of Service markings. 2535 . Change from SDNVs to CBOR representation. 2536 . Add lifetime overrides. 2538 Appendix A. For More Information 2540 Copyright (c) 2020 IETF Trust and the persons identified as authors 2541 of the code. All rights reserved. 2543 Redistribution and use in source and binary forms, with or without 2544 modification, is permitted pursuant to, and subject to the license 2545 terms contained in, the Simplified BSD License set forth in Section 2546 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 2547 (http://trustee.ietf.org/license-info). 2549 Appendix B. CDDL expression 2551 For informational purposes, Carsten Bormann and Brian Sipos have 2552 kindly provided an expression of the Bundle Protocol specification 2553 in the Concise Data Definition Language (CDDL). That CDDL 2554 expression is presented below. Note that wherever the CDDL 2555 expression is in disagreement with the textual representation of the 2556 BP specification presented in the earlier sections of this document, 2557 the textual representation rules. 2559 start = bundle / #6.55799(bundle) 2561 ; Times before 2000 are invalid 2563 dtn-time = uint 2565 ; CRC enumerated type 2567 crc-type = &( 2569 crc-none: 0, 2571 crc-16bit: 1, 2573 crc-32bit: 2 2575 ) 2577 ; Either 16-bit or 32-bit 2579 crc-value = (bstr .size 2) / (bstr .size 4) 2581 creation-timestamp = [ 2583 dtn-time, ; absolute time of creation 2585 sequence: uint ; sequence within the time 2587 ] 2589 eid = $eid .within eid-structure 2591 eid-structure = [ 2593 uri-code: uint, 2594 SSP: any 2596 ] 2598 $eid /= [ 2600 uri-code: 1, 2602 SSP: (tstr / 0) 2604 ] 2606 $eid /= [ 2608 uri-code: 2, 2610 SSP: [ 2612 nodenum: uint, 2614 servicenum: uint 2616 ] 2618 ] 2620 ; The root bundle array 2622 bundle = [primary-block, *extension-block, payload-block] 2624 primary-block = [ 2626 version: 7, 2628 bundle-control-flags, 2630 crc-type, 2632 destination: eid, 2634 source-node: eid, 2636 report-to: eid, 2638 creation-timestamp, 2640 lifetime: uint, 2641 ? ( 2643 fragment-offset: uint, 2645 total-application-data-length: uint 2647 ), 2649 ? crc-value, 2651 ] 2653 bundle-control-flags = uint .bits bundleflagbits 2655 bundleflagbits = &( 2657 reserved: 21, 2659 reserved: 20, 2661 reserved: 19, 2663 bundle-deletion-status-reports-are-requested: 18, 2665 bundle-delivery-status-reports-are-requested: 17, 2667 bundle-forwarding-status-reports-are-requested: 16, 2669 reserved: 15, 2671 bundle-reception-status-reports-are-requested: 14, 2673 reserved: 13, 2675 reserved: 12, 2677 reserved: 11, 2679 reserved: 10, 2681 reserved: 9, 2683 reserved: 8, 2685 reserved: 7, 2686 status-time-is-requested-in-all-status-reports: 6, 2688 user-application-acknowledgement-is-requested: 5, 2690 reserved: 4, 2692 reserved: 3, 2694 bundle-must-not-be-fragmented: 2, 2696 payload-is-an-administrative-record: 1, 2698 bundle-is-a-fragment: 0 2700 ) 2702 ; Abstract shared structure of all non-primary blocks 2704 canonical-block-structure = [ 2706 block-type-code: uint, 2708 block-number: uint, 2710 block-control-flags, 2712 crc-type, 2714 ; Each block type defines the content within the bytestring 2716 block-type-specific-data, 2718 ? crc-value 2720 ] 2722 block-control-flags = uint .bits blockflagbits 2724 blockflagbits = &( 2726 reserved: 7, 2728 reserved: 6, 2730 reserved: 5, 2732 block-must-be-removed-from-bundle-if-it-cannot-be-processed: 4, 2733 reserved: 3, 2735 bundle-must-be-deleted-if-block-cannot-be-processed: 2, 2737 status-report-must-be-transmitted-if-block-cannot-be-processed: 1, 2739 block-must-be-replicated-in-every-fragment: 0 2741 ) 2743 block-type-specific-data = bstr / #6.24(bstr) 2745 ; Actual CBOR data embedded in a bytestring, with optional tag to 2746 indicate so 2748 embedded-cbor = (bstr .cbor Item) / #6.24(bstr .cbor Item) 2750 ; Extension block type, which does not specialize other than the 2751 code/number 2753 extension-block = $extension-block-structure .within canonical- 2754 block-structure 2756 ; Generic shared structure of all non-primary blocks 2758 extension-block-use = [ 2760 block-type-code: CodeValue, 2762 block-number: (uint .gt 1), 2764 block-control-flags, 2766 crc-type, 2768 BlockData, 2770 ? crc-value 2772 ] 2774 ; Payload block type 2776 payload-block = payload-block-structure .within canonical-block- 2777 structure 2778 payload-block-structure = [ 2780 block-type-code: 1, 2782 block-number: 1, 2784 block-control-flags, 2786 crc-type, 2788 $payload-block-data, 2790 ? crc-value 2792 ] 2794 ; Arbitrary payload data, including non-CBOR bytestring 2796 $payload-block-data /= block-type-specific-data 2798 ; Administrative record as a payload data specialization 2800 $payload-block-data /= embedded-cbor 2802 admin-record = $admin-record .within admin-record-structure 2804 admin-record-structure = [ 2806 record-type-code: uint, 2808 record-content: any 2810 ] 2812 ; Only one defined record type 2814 $admin-record /= [1, status-record-content] 2816 status-record-content = [ 2818 bundle-status-information, 2820 status-report-reason-code: uint, 2822 source-node-eid: eid, 2824 subject-creation-timestamp: creation-timestamp, 2825 ? ( 2827 subject-payload-offset: uint, 2829 subject-payload-length: uint 2831 ) 2833 ] 2835 bundle-status-information = [ 2837 reporting-node-received-bundle: status-info-content, 2839 reporting-node-forwarded-bundle: status-info-content, 2841 reporting-node-delivered-bundle: status-info-content, 2843 reporting-node-deleted-bundle: status-info-content 2845 ] 2847 status-info-content = [ 2849 status-indicator: bool, 2851 ? timestamp: dtn-time 2853 ] 2855 ; Previous Node extension block 2857 $extension-block-structure /= 2859 extension-block-use<6, embedded-cbor> 2861 ext-data-previous-node = eid 2863 ; Bundle Age extension block 2865 $extension-block-structure /= 2867 extension-block-use<7, embedded-cbor> 2869 ext-data-bundle-age = uint 2871 ; Hop Count extension block 2872 $extension-block-structure /= 2874 extension-block-use<10, embedded-cbor> 2876 ext-data-hop-count = [ 2878 hop-limit: uint, 2880 hop-count: uint 2882 ] 2884 Authors' Addresses 2886 Scott Burleigh 2887 Jet Propulsion Laboratory, California Institute of Technology 2888 4800 Oak Grove Dr. 2889 Pasadena, CA 91109-8099 2890 US 2891 Phone: +1 818 393 3353 2892 Email: Scott.C.Burleigh@jpl.nasa.gov 2894 Kevin Fall 2895 Roland Computing Services 2896 3871 Piedmont Ave. Suite 8 2897 Oakland, CA 94611 2898 US 2899 Email: kfall+rcs@kfall.com 2901 Edward J. Birrane 2902 Johns Hopkins University Applied Physics Laboratory 2903 11100 Johns Hopkins Rd 2904 Laurel, MD 20723 2905 US 2906 Phone: +1 443 778 7423 2907 Email: Edward.Birrane@jhuapl.edu