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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'CRC' ** Obsolete normative reference: RFC 7049 (Obsoleted by RFC 8949) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Delay-Tolerant Networking Working Group S. Burleigh 2 Internet Draft JPL, Calif. Inst. Of Technology 3 Intended status: Standards Track K. Fall 4 Expires: February 2018 Nefeli Networks, Inc. 5 E. Birrane 6 APL, Johns Hopkins University 7 November 27, 2017 9 Bundle Protocol Version 7 10 draft-ietf-dtn-bpbis-10.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 May 31, 2018. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with 45 respect to this document. Code Components extracted from this 46 document must include Simplified BSD License text as described in 47 Section 4.e of the Trust Legal Provisions and are provided without 48 warranty as described in the Simplified BSD License. 50 Abstract 52 This Internet Draft presents a specification for Bundle Protocol, 53 adapted from the experimental Bundle Protocol specification 54 developed by the Delay-Tolerant Networking Research group of the 55 Internet Research Task Force and documented in RFC 5050. 57 Table of Contents 59 1. Introduction...................................................3 60 2. Conventions used in this document..............................5 61 3. Service Description............................................5 62 3.1. Definitions...............................................5 63 3.2. Discussion of BP concepts.................................9 64 3.3. Services Offered by Bundle Protocol Agents...............12 65 4. Bundle Format.................................................12 66 4.1. BP Fundamental Data Structures...........................13 67 4.1.1. CRC Type............................................13 68 4.1.2. CRC.................................................13 69 4.1.3. Bundle Processing Control Flags.....................13 70 4.1.4. Block Processing Control Flags......................14 71 4.1.5. Identifiers.........................................15 72 4.1.5.1. Endpoint ID....................................15 73 4.1.5.2. Node ID........................................16 74 4.1.6. DTN Time............................................17 75 4.1.7. Creation Timestamp..................................17 76 4.1.8. Block-type-specific Data............................17 77 4.2. Bundle Representation....................................17 78 4.2.1. Bundle..............................................18 79 4.2.2. Primary Bundle Block................................18 80 4.2.3. Canonical Bundle Block Format.......................20 81 4.3. Extension Blocks.........................................21 82 4.3.1. Previous Node.......................................21 83 4.3.2. Bundle Age..........................................22 84 4.3.3. Hop Count...........................................22 85 5. Bundle Processing.............................................23 86 5.1. Generation of Administrative Records.....................23 87 5.2. Bundle Transmission......................................24 88 5.3. Bundle Dispatching.......................................24 89 5.4. Bundle Forwarding........................................24 90 5.4.1. Forwarding Contraindicated..........................26 91 5.4.2. Forwarding Failed...................................26 92 5.5. Bundle Expiration........................................27 93 5.6. Bundle Reception.........................................27 94 5.7. Local Bundle Delivery....................................28 95 5.8. Bundle Fragmentation.....................................29 96 5.9. Application Data Unit Reassembly.........................30 97 5.10. Bundle Deletion.........................................30 98 5.11. Discarding a Bundle.....................................31 99 5.12. Canceling a Transmission................................31 100 6. Administrative Record Processing..............................31 101 6.1. Administrative Records...................................31 102 6.1.1. Bundle Status Reports...............................32 103 6.2. Generation of Administrative Records.....................34 104 7. Services Required of the Convergence Layer....................35 105 7.1. The Convergence Layer....................................35 106 7.2. Summary of Convergence Layer Services....................35 107 8. Implementation Status.........................................35 108 9. Security Considerations.......................................37 109 10. IANA Considerations..........................................38 110 11. References...................................................39 111 11.1. Normative References....................................39 112 11.2. Informative References..................................40 113 12. Acknowledgments..............................................40 114 13. Significant Changes from RFC 5050............................40 115 Appendix A. For More Information.................................42 116 Appendix B. CDDL expression......................................43 118 1. Introduction 120 Since the publication of the Bundle Protocol Specification 121 (Experimental RFC 5050) in 2007, the Delay-Tolerant Networking (DTN) 122 Bundle Protocol has been implemented in multiple programming 123 languages and deployed to a wide variety of computing platforms. 124 This implementation and deployment experience has identified 125 opportunities for making the protocol simpler, more capable, and 126 easier to use. The present document, standardizing the Bundle 127 Protocol (BP), is adapted from RFC 5050 in that context. 129 This document describes version 7 of BP. 131 Delay Tolerant Networking is a network architecture providing 132 communications in and/or through highly stressed environments. 133 Stressed networking environments include those with intermittent 134 connectivity, large and/or variable delays, and high bit error 135 rates. To provide its services, BP may be viewed as sitting at the 136 application layer of some number of constituent networks, forming a 137 store-carry-forward overlay network. Key capabilities of BP 138 include: 140 . Ability to use physical motility for the movement of data 141 . Ability to move the responsibility for error control from one 142 node to another 143 . Ability to cope with intermittent connectivity, including cases 144 where the sender and receiver are not concurrently present in 145 the network 146 . Ability to take advantage of scheduled, predicted, and 147 opportunistic connectivity, whether bidirectional or 148 unidirectional, in addition to continuous connectivity 149 . Late binding of overlay network endpoint identifiers to 150 underlying constituent network addresses 152 For descriptions of these capabilities and the rationale for the DTN 153 architecture, see [ARCH] and [SIGC]. 155 BP's location within the standard protocol stack is as shown in 156 Figure 1. BP uses underlying "native" transport and/or network 157 protocols for communications within a given constituent network. 159 The interface between the bundle protocol and a specific underlying 160 protocol is termed a "convergence layer adapter". 162 Figure 1 shows three distinct transport and network protocols 163 (denoted T1/N1, T2/N2, and T3/N3). 165 +-----------+ +-----------+ 166 | BP app | | BP app | 167 +---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+ 168 | BP v | | ^ BP v | | ^ BP v | | ^ BP | 169 +---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+ 170 | T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 | 171 +---------v-+ +-^---------v-+ +-^---------v + +-^---------+ 172 | N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 | 173 +---------v-+ +-^---------v + +-^---------v-+ +-^---------+ 174 | >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ | 175 +-----------+ +-------------+ +-------------+ +-----------+ 176 | | | | 177 |<---- A network ---->| |<---- A network ---->| 178 | | | | 180 Figure 1: The Bundle Protocol in the Protocol Stack Model 182 This document describes the format of the protocol data units 183 (called "bundles") passed between entities participating in BP 184 communications. 186 The entities are referred to as "bundle nodes". This document does 187 not address: 189 . Operations in the convergence layer adapters that bundle nodes 190 use to transport data through specific types of internets. 191 (However, the document does discuss the services that must be 192 provided by each adapter at the convergence layer.) 193 . The bundle route computation algorithm. 194 . Mechanisms for populating the routing or forwarding information 195 bases of bundle nodes. 196 . The mechanisms for securing bundles en route. 197 . The mechanisms for managing bundle nodes. 199 Note that implementations of the specification presented in this 200 document will not be interoperable with implementations of RFC 5050. 202 2. Conventions used in this document 204 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 205 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 206 document are to be interpreted as described in RFC-2119 [RFC2119]. 208 In this document, these words will appear with that interpretation 209 only when in ALL CAPS. Lower case uses of these words are not to be 210 interpreted as carrying RFC-2119 significance. 212 3. Service Description 214 3.1. Definitions 216 Bundle - A bundle is a protocol data unit of BP, so named because 217 negotiation of the parameters of a data exchange may be impractical 218 in a delay-tolerant network: it is often better practice to "bundle" 219 with a unit of data all metadata that might be needed in order to 220 make the data immediately usable when delivered to applications. 221 Each bundle comprises a sequence of two or more "blocks" of protocol 222 data, which serve various purposes. 224 Block - A bundle protocol block is one of the protocol data 225 structures that together constitute a well-formed bundle. 227 Bundle payload - A bundle payload (or simply "payload") is the 228 application data whose conveyance to the bundle's destination is the 229 purpose for the transmission of a given bundle; it is the content of 230 the bundle's payload block. The terms "bundle content", "bundle 231 payload", and "payload" are used interchangeably in this document. 233 Partial payload - A partial payload is a payload that comprises 234 either the first N bytes or the last N bytes of some other payload 235 of length M, such that 0 < N < M. Note that every partial payload 236 is a payload and therefore can be further subdivided into partial 237 payloads. 239 Fragment - A fragment is a bundle whose payload block contains a 240 partial payload. 242 Bundle node - A bundle node (or, in the context of this document, 243 simply a "node") is any entity that can send and/or receive bundles. 244 Each bundle node has three conceptual components, defined below, as 245 shown in Figure 2: a "bundle protocol agent", a set of zero or more 246 "convergence layer adapters", and an "application agent". 248 +-----------------------------------------------------------+ 249 |Node | 250 | | 251 | +-------------------------------------------------------+ | 252 | |Application Agent | | 253 | | | | 254 | | +--------------------------+ +----------------------+ | | 255 | | |Administrative element | |Application-specific | | | 256 | | | | |element | | | 257 | | | | | | | | 258 | | +--------------------------+ +----------------------+ | | 259 | | ^ ^ | | 260 | | Admin|records Application|data | | 261 | | | | | | 262 | +----------------v--------------------------v-----------+ | 263 | ^ | 264 | | ADUs | 265 | | | 266 | +-----------------------------v-------------------------+ | 267 | |Bundle Protocol Agent | | 268 | | | | 269 | | | | 270 | +-------------------------------------------------------+ | 271 | ^ ^ ^ | 272 | | Bundles | Bundles Bundles | | 273 | | | | | 274 | +------v-----+ +-----v------+ +-----v-----+ | 275 | |CLA 1 | |CLA 2 | |CLA n | | 276 | | | | | . . . | | | 277 | | | | | | | | 278 +-+------------+-----+------------+-----------+-----------+-+ 279 ^ ^ ^ 281 CL1|PDUs CL2|PDUs CLn|PDUs 282 | | | 283 +------v-----+ +-----v------+ +-----v-----+ 284 Network 1 Network 2 Network n 286 Figure 2: Components of a BP Node 288 Bundle protocol agent - The bundle protocol agent (BPA) of a node is 289 the node component that offers the BP services and executes the 290 procedures of the bundle protocol. 292 Convergence layer adapter - A convergence layer adapter (CLA) is a 293 node component that sends and receives bundles on behalf of the BPA, 294 utilizing the services of some 'native' protocol stack that is 295 supported in one of the networks within which the node is 296 functionally located. 298 Application agent - The application agent (AA) of a node is the node 299 component that utilizes the BP services to effect communication for 300 some user purpose. The application agent in turn has two elements, 301 an administrative element and an application-specific element. 303 Application-specific element - The application-specific element of 304 an AA is the node component that constructs, requests transmission 305 of, accepts delivery of, and processes units of user application 306 data. 308 Administrative element - The administrative element of an AA is the 309 node component that constructs and requests transmission of 310 administrative records (defined below), including status reports, 311 and accepts delivery of and processes any administrative records 312 that the node receives. 314 Administrative record - A BP administrative record is an application 315 data unit that is exchanged between the administrative elements of 316 nodes' application agents for some BP administrative purpose. The 317 only administrative record defined in this specification is the 318 status report, discussed later. 320 Bundle endpoint - A bundle endpoint (or simply "endpoint") is a set 321 of zero or more bundle nodes that all identify themselves for BP 322 purposes by some common identifier, called a "bundle endpoint ID" 323 (or, in this document, simply "endpoint ID"; endpoint IDs are 324 described in detail in Section 4.4.1 below). 326 Singleton endpoint - A singleton endpoint is an endpoint that always 327 contains exactly one member. 329 Registration - A registration is the state machine characterizing a 330 given node's membership in a given endpoint. Any single 331 registration has an associated delivery failure action as defined 332 below and must at any time be in one of two states: Active or 333 Passive. 335 Delivery - A bundle is considered to have been delivered at a node 336 subject to a registration as soon as the application data unit that 337 is the payload of the bundle, together with any relevant metadata 338 (an implementation matter), has been presented to the node's 339 application agent in a manner consistent with the state of that 340 registration. 342 Deliverability - A bundle is considered "deliverable" subject to a 343 registration if and only if (a) the bundle's destination endpoint is 344 the endpoint with which the registration is associated, (b) the 345 bundle has not yet been delivered subject to this registration, and 346 (c) the bundle has not yet been "abandoned" (as defined below) 347 subject to this registration. 349 Abandonment - To abandon a bundle subject to some registration is to 350 assert that the bundle is not deliverable subject to that 351 registration. 353 Delivery failure action - The delivery failure action of a 354 registration is the action that is to be taken when a bundle that is 355 "deliverable" subject to that registration is received at a time 356 when the registration is in the Passive state. 358 Destination - The destination of a bundle is the endpoint comprising 359 the node(s) at which the bundle is to be delivered (as defined 360 below). 362 Transmission - A transmission is an attempt by a node's BPA to cause 363 copies of a bundle to be delivered to one or more of the nodes that 364 are members of some endpoint (the bundle's destination) in response 365 to a transmission request issued by the node's application agent. 367 Forwarding - To forward a bundle to a node is to invoke the services 368 of one or more CLAs in a sustained effort to cause a copy of the 369 bundle to be received by that node. 371 Discarding - To discard a bundle is to cease all operations on the 372 bundle and functionally erase all references to it. The specific 373 procedures by which this is accomplished are an implementation 374 matter. 376 Retention constraint - A retention constraint is an element of the 377 state of a bundle that prevents the bundle from being discarded. 378 That is, a bundle cannot be discarded while it has any retention 379 constraints. 381 Deletion - To delete a bundle is to remove unconditionally all of 382 the bundle's retention constraints, enabling the bundle to be 383 discarded. 385 3.2. Discussion of BP concepts 387 Multiple instances of the same bundle (the same unit of DTN protocol 388 data) might exist concurrently in different parts of a network -- 389 possibly differing in some blocks -- in the memory local to one or 390 more bundle nodes and/or in transit between nodes. In the context of 391 the operation of a bundle node, a bundle is an instance (copy), in 392 that node's local memory, of some bundle that is in the network. 394 The payload for a bundle forwarded in response to a bundle 395 transmission request is the application data unit whose location is 396 provided as a parameter to that request. The payload for a bundle 397 forwarded in response to reception of a bundle is the payload of the 398 received bundle. 400 In the most familiar case, a bundle node is instantiated as a single 401 process running on a general-purpose computer, but in general the 402 definition is meant to be broader: a bundle node might alternatively 403 be a thread, an object in an object-oriented operating system, a 404 special-purpose hardware device, etc. 406 The manner in which the functions of the BPA are performed is wholly 407 an implementation matter. For example, BPA functionality might be 408 coded into each node individually; it might be implemented as a 409 shared library that is used in common by any number of bundle nodes 410 on a single computer; it might be implemented as a daemon whose 411 services are invoked via inter-process or network communication by 412 any number of bundle nodes on one or more computers; it might be 413 implemented in hardware. 415 Every CLA implements its own thin layer of protocol, interposed 416 between BP and the (usually "top") protocol(s) of the underlying 417 native protocol stack; this "CL protocol" may only serve to 418 multiplex and de-multiplex bundles to and from the underlying native 419 protocol, or it may offer additional CL-specific functionality. The 420 manner in which a CLA sends and receives bundles, as well as the 421 definitions of CLAs and CL protocols, are beyond the scope of this 422 specification. 424 Note that the administrative element of a node's application agent 425 may itself, in some cases, function as a convergence-layer adapter. 426 That is, outgoing bundles may be "tunneled" through encapsulating 427 bundles: 429 . An outgoing bundle constitutes a byte array. This byte array 430 may, like any other, be presented to the bundle protocol agent 431 as an application data unit that is to be transmitted to some 432 endpoint. 433 . The original bundle thus forms the payload of an encapsulating 434 bundle that is forwarded using some other convergence-layer 435 protocol(s). 436 . When the encapsulating bundle is received, its payload is 437 delivered to the peer application agent administrative element, 438 which then instructs the bundle protocol agent to dispatch that 439 original bundle in the usual way. 441 The purposes for which this technique may be useful (such as cross- 442 domain security) are beyond the scope of this specification. 444 The only interface between the BPA and the application-specific 445 element of the AA is the BP service interface. But between the BPA 446 and the administrative element of the AA there is a (conceptual) 447 private control interface in addition to the BP service interface. 448 This private control interface enables the BPA and the 449 administrative element of the AA to direct each other to take action 450 under specific circumstances. 452 In the case of a node that serves simply as a BP "router", the AA 453 may have no application-specific element at all. The application- 454 specific elements of other nodes' AAs may perform arbitrarily 455 complex application functions, perhaps even offering multiplexed DTN 456 communication services to a number of other applications. As with 457 the BPA, the manner in which the AA performs its functions is wholly 458 an implementation matter. 460 Singletons are the most familiar sort of endpoint, but in general 461 the endpoint notion is meant to be broader. For example, the nodes 462 in a sensor network might constitute a set of bundle nodes that 463 identify themselves by a single common endpoint ID and thus form a 464 single bundle endpoint. *Note* too that a given bundle node might 465 identify itself by multiple endpoint IDs and thus be a member of 466 multiple bundle endpoints. 468 The destination of every bundle is an endpoint, which may or may not 469 be singleton. The source of every bundle is a node, identified by 470 the endpoint ID for some singleton endpoint that contains that node. 472 Note, though, that the source node ID asserted in a given bundle may 473 be the null endpoint ID (as described later) rather than the 474 endpoint ID of the actual source node; bundles for which the 475 asserted source node ID is the null endpoint ID are termed 476 "anonymous" bundles. 478 Any number of transmissions may be concurrently undertaken by the 479 bundle protocol agent of a given node. 481 When the bundle protocol agent of a node determines that a bundle 482 must be forwarded to a node (either to a node that is a member of 483 the bundle's destination endpoint or to some intermediate forwarding 484 node) in the course of completing the successful transmission of 485 that bundle, it invokes the services of one or more CLAs in a 486 sustained effort to cause a copy of the bundle to be received by 487 that node. 489 Upon reception, the processing of a bundle that has been received by 490 a given node depends on whether or not the receiving node is 491 registered in the bundle's destination endpoint. If it is, and if 492 the payload of the bundle is non-fragmentary (possibly as a result 493 of successful payload reassembly from fragmentary payloads, 494 including the original payload of the newly received bundle), then 495 the bundle is normally delivered to the node's application agent 496 subject to the registration characterizing the node's membership in 497 the destination endpoint. 499 The bundle protocol does not natively ensure delivery of a bundle to 500 its destination. Data loss along the path to the destination node 501 can be minimized by utilizing reliable convergence-layer protocols 502 between neighbors on all segments of the end-to-end path, but for 503 end-to-end bundle delivery assurance it will be necessary to develop 504 extensions to the bundle protocol and/or application-layer 505 mechanisms. 507 The bundle protocol is designed for extensibility. Bundle protocol 508 extensions, documented elsewhere, may extend this specification by: 510 . defining additional blocks; 511 . defining additional administrative records; 512 . defining additional bundle processing flags; 513 . defining additional block processing flags; 514 . defining additional types of bundle status reports; 515 . defining additional bundle status report reason codes; 516 . defining additional mandates and constraints on processing 517 that conformant bundle protocol agents must perform at 518 specified points in the inbound and outbound bundle processing 519 cycles. 521 3.3. Services Offered by Bundle Protocol Agents 523 The BPA of each node is expected to provide the following services 524 to the node's application agent: 526 . commencing a registration (registering the node in an 527 endpoint); 528 . terminating a registration; 529 . switching a registration between Active and Passive states; 530 . transmitting a bundle to an identified bundle endpoint; 531 . canceling a transmission; 532 . polling a registration that is in the Passive state; 533 . delivering a received bundle. 535 4. Bundle Format 537 The format of bundles SHALL conform to the Concise Binary Object 538 Representation (CBOR [RFC7049]). 540 Each bundle SHALL be a concatenated sequence of at least two blocks, 541 represented as a CBOR indefinite-length array. The first block in 542 the sequence (the first item of the array) MUST be a primary bundle 543 block in CBOR representation as described below; the bundle MUST 544 have exactly one primary bundle block. The primary block MUST be 545 followed by one or more canonical bundle blocks (additional array 546 items) in CBOR representation as described below. The last such 547 block MUST be a payload block; the bundle MUST have exactly one 548 payload block. The last item of the array, immediately following 549 the payload block, SHALL be a CBOR "break" stop code. 551 (Note that, while CBOR permits considerable flexibility in the 552 encoding of bundles, this flexibility must not be interpreted as 553 inviting increased complexity in protocol data unit structure.) 555 An implementation of the Bundle Protocol MAY discard any sequence of 556 bytes that does not conform to the Bundle Protocol specification. 558 An implementation of the Bundle Protocol MAY accept a sequence of 559 bytes that does not conform to the Bundle Protocol specification 560 (e.g., one that represents data elements in fixed-length arrays 561 rather than indefinite-length arrays) and transform it into 562 conformant BP structure before processing it. Procedures for 563 accomplishing such a transformation are beyond the scope of this 564 specification. 566 4.1. BP Fundamental Data Structures 568 4.1.1. CRC Type 570 CRC type is an unsigned integer type code for which the following 571 values (and no others) are valid: 573 . 0 indicates "no CRC is present." 574 . 1 indicates "a standard X-25 CRC-16 is present." [CRC] 575 . 2 indicates "a standard PKZIP CRC-32 is present." [CRC] 577 CRC type SHALL be represented as a CBOR unsigned integer. 579 4.1.2. CRC 581 CRC SHALL be omitted from a block if and only if the block's CRC 582 type code is zero. 584 When not omitted, the CRC SHALL be represented as sequence of two 585 bytes (if CRC type is 1) or as a sequence of four bytes (if CRC type 586 is 2). 588 4.1.3. Bundle Processing Control Flags 590 Bundle processing control flags assert properties of the bundle as a 591 whole rather than of any particular block of the bundle. They are 592 conveyed in the primary block of the bundle. 594 The following properties are asserted by the bundle processing 595 control flags: 597 . The bundle is a fragment. (Boolean) 599 . The bundle's payload is an administrative record. (Boolean) 601 . The bundle must not be fragmented. (Boolean) 603 . Acknowledgment by the user application is requested. (Boolean) 605 . Status time is requested in all status reports. (Boolean) 607 . The bundle contains a "manifest" extension block. (Boolean) 609 . Flags requesting types of status reports (all Boolean): 611 o Request reporting of bundle reception. 613 o Request reporting of bundle forwarding. 615 o Request reporting of bundle delivery. 617 o Request reporting of bundle deletion. 619 If the bundle processing control flags indicate that the bundle's 620 application data unit is an administrative record, then all status 621 report request flag values must be zero. 623 If the bundle's source node is omitted (i.e., the source node ID is 624 the ID of the null endpoint, which has no members as discussed 625 below; this option enables anonymous bundle transmission), then the 626 bundle is not uniquely identifiable and all bundle protocol features 627 that rely on bundle identity must therefore be disabled: the "Bundle 628 must not be fragmented" flag value must be 1 and all status report 629 request flag values must be zero. 631 The bundle processing control flags SHALL be represented as a CBOR 632 unsigned integer item containing a bit field of 16 bits indicating 633 the control flag values as follows: 635 . Bit 0 (the high-order bit, 0x8000): reserved. 636 . Bit 1 (0x4000): reserved. 637 . Bit 2 (0x2000): reserved. 638 . Bit 3(0x1000): bundle deletion status reports are requested. 639 . Bit 4(0x0800): bundle delivery status reports are requested. 640 . Bit 5(0x0400): bundle forwarding status reports are requested. 641 . Bit 6(0x0200): reserved. 642 . Bit 7(0x0100): bundle reception status reports are requested. 643 . Bit 8(0x0080): bundle contains a Manifest block. 644 . Bit 9(0x0040): status time is requested in all status reports. 645 . Bit 10(0x0020): user application acknowledgement is requested. 646 . Bit 11(0x0010): reserved. 647 . Bit 12(0x0008): reserved. 648 . Bit 13(0x0004): bundle must not be fragmented. 649 . Bit 14(0x0002): payload is an administrative record. 650 . Bit 15 (the low-order bit, 0x0001: bundle is a fragment. 652 4.1.4. Block Processing Control Flags 654 The block processing control flags assert properties of canonical 655 bundle blocks. They are conveyed in the header of the block to 656 which they pertain. 658 The following properties are asserted by the block processing 659 control flags: 661 . This block must be replicated in every fragment. (Boolean) 663 . Transmission of a status report is requested if this block 664 can't be processed. (Boolean) 666 . Block must be removed from the bundle if it can't be processed. 667 (Boolean) 669 . Bundle must be deleted if this block can't be processed. 670 (Boolean) 672 For each bundle whose bundle processing control flags indicate that 673 the bundle's application data unit is an administrative record, or 674 whose source node ID is the null endpoint ID as defined below, the 675 value of the "Transmit status report if block can't be processed" 676 flag in every canonical block of the bundle must be zero. 678 The block processing control flags SHALL be represented as a CBOR 679 unsigned integer item containing a bit field of 8 bits indicating 680 the control flag values as follows: 682 . Bit 0 (the high-order bit, 0x80): reserved. 683 . Bit 1 (0x40): reserved. 684 . Bit 2(0x20): reserved. 685 . Bit 3(0x10): reserved. 686 . Bit 4(0x08): bundle must be deleted if block can't be 687 processed. 688 . Bit 5(0x04): transmission of a status report is requested if 689 block can't be processed. 690 . Bit 6(0x02): block must be removed from bundle if it can't be 691 processed. 692 . Bit 7(the low-order bit, 0x01): block must be replicated in 693 every fragment. 695 4.1.5. Identifiers 697 4.1.5.1. Endpoint ID 699 The destinations of bundles are bundle endpoints, identified by text 700 strings termed "endpoint IDs" (see Section 3.1). Each endpoint ID 701 (EID) is a Uniform Resource Identifier (URI; [URI]). As such, each 702 endpoint ID can be characterized as having this general structure: 704 < scheme name > : < scheme-specific part, or "SSP" > 706 The scheme identified by the < scheme name > in an endpoint ID is a 707 set of syntactic and semantic rules that fully explain how to parse 708 and interpret the SSP. The set of allowable schemes is effectively 709 unlimited. Any scheme conforming to [URIREG] may be used in a bundle 710 protocol endpoint ID. 712 Note that, although endpoint IDs are URIs, implementations of the BP 713 service interface may support expression of endpoint IDs in some 714 internationalized manner (e.g., Internationalized Resource 715 Identifiers (IRIs); see [RFC3987]). 717 The endpoint ID "dtn:none" identifies the "null endpoint", the 718 endpoint that by definition never has any members. 720 Each BP endpoint ID (EID) SHALL be represented as a CBOR array 721 comprising a 2-tuple. 723 The first item of the array SHALL be the code number identifying the 724 endpoint's URI scheme [URI], as defined in the registry of URI 725 scheme code numbers for Bundle Protocol maintained by IANA as 726 described in Section 10. [URIREG]. Each URI scheme code number 727 SHALL be represented as a CBOR unsigned integer. 729 The second item of the array SHALL be the applicable CBOR 730 representation of the scheme-specific part (SSP) of the EID, defined 731 as follows: 733 . If the EID's URI scheme is "dtn" then the SSP SHALL be 734 represented as a CBOR text string unless the EID's SSP is 735 "none", in which case the SSP SHALL be represented as a CBOR 736 unsigned integer with the value zero. 737 . If the EID's URI scheme is "ipn" then the SSP SHALL be 738 represented as a CBOR array comprising a 2-tuple. The first 739 item of this array SHALL be the EID's node number represented 740 as a CBOR unsigned integer. The second item of this array 741 SHALL be the EID's service number represented as a CBOR 742 unsigned integer. 743 . Definitions of the CBOR representations of the SSPs of EIDs 744 encoded in other URI schemes are included in the specifications 745 defining those schemes. 747 4.1.5.2. Node ID 749 For many purposes of the Bundle Protocol it is important to identify 750 the node that is operative in some context. 752 As discussed in 3.1 above, nodes are distinct from endpoints; 753 specifically, an endpoint is a set of zero or more nodes. But 754 rather than define a separate namespace for node identifiers, we 755 instead use endpoint identifiers to identify nodes, subject to the 756 following restrictions: 758 . Every node MUST be a member of at least one singleton endpoint. 759 . The EID of any singleton endpoint of which a node is a member 760 MAY be used to identify that node. A "node ID" is an EID that 761 is used in this way. 762 . A node's membership in a given singleton endpoint MUST be 763 sustained at least until the nominal operation of the Bundle 764 Protocol no longer depends on the identification of that node 765 using that endpoint's ID. 767 4.1.6. DTN Time 769 A DTN time is an unsigned integer indicating a count of seconds 770 since the start of the year 2000 on the Coordinated Universal Time 771 (UTC) scale [UTC]. Each DTN time SHALL be represented as a CBOR 772 unsigned integer item. 774 4.1.7. Creation Timestamp 776 Each creation timestamp SHALL be represented as a CBOR array item 777 comprising a 2-tuple. 779 The first item of the array SHALL be a DTN time. 781 The second item of the array SHALL be the creation timestamp's 782 sequence number, represented as a CBOR unsigned integer. 784 4.1.8. Block-type-specific Data 786 Block-type-specific data in each block (other than the primary 787 block) SHALL be the applicable CBOR representation of the content of 788 the block. Details of this representation are included in the 789 specification defining the block type. 791 4.2. Bundle Representation 793 This section describes the primary block in detail and non-primary 794 blocks in general. Rules for processing these blocks appear in 795 Section 5 of this document. 797 Note that supplementary DTN protocol specifications (including, but 798 not restricted to, the Bundle Security Protocol [BPSEC]) may require 799 that BP implementations conforming to those protocols construct and 800 process additional blocks. 802 4.2.1. Bundle 804 Each bundle SHALL be represented as a CBOR indefinite-length array. 805 The first item of this array SHALL be the CBOR representation of a 806 Primary Block. Every other item of the array except the last SHALL 807 be the CBOR representation of a Canonical Block. The last item of 808 the array SHALL be a CBOR "break" stop code. 810 4.2.2. Primary Bundle Block 812 The primary bundle block contains the basic information needed to 813 forward bundles to their destinations. 815 Each primary block SHALL be represented as a CBOR array; the number 816 of elements in the array SHALL be 8 (if the bundle is not a fragment 817 and CRC type is zero) or 9 (if the bundle is not a fragment and CRC 818 type is non-zero) or 10 (if the bundle is a fragment and CRC type is 819 zero) or 11 (if the bundle is a fragment and CRC-type is non-zero). 821 The fields of the primary bundle block SHALL be as follows, listed 822 in the order in which they MUST appear: 824 Version: An unsigned integer value indicating the version of the 825 bundle protocol that constructed this block. The present document 826 describes version 7 of the bundle protocol. Version number SHALL be 827 represented as a CBOR unsigned integer item. 829 Bundle Processing Control Flags: The Bundle Processing Control Flags 830 are discussed in Section 4.1.3. above. 832 CRC Type: CRC Type codes are discussed in Section 4.1.1. above. 834 Destination EID: The Destination EID field identifies the bundle 835 endpoint that is the bundle's destination, i.e., the endpoint that 836 contains the node(s) at which the bundle is to be delivered. 838 Source node ID: The Source node ID field identifies the bundle node 839 at which the bundle was initially transmitted, except that Source 840 node ID may be the null endpoint ID in the event that the bundle's 841 source chooses to remain anonymous. 843 Report-to EID: The Report-to EID field identifies the bundle 844 endpoint to which status reports pertaining to the forwarding and 845 delivery of this bundle are to be transmitted. 847 Creation Timestamp: The creation timestamp is a pair of unsigned 848 integers that, together with the source node ID and (if the bundle 849 is a fragment) the fragment offset and payload length, serve to 850 identify the bundle. The first of these integers is the bundle's 851 creation time, while the second is the bundle's creation timestamp 852 sequence number. Bundle creation time shall be the time - expressed 853 in seconds since the start of the year 2000, on the Coordinated 854 Universal Time (UTC) scale [UTC] - at which the transmission request 855 was received that resulted in the creation of the bundle. Sequence 856 count shall be the latest value (as of the time at which that 857 transmission request was received) of a monotonically increasing 858 positive integer counter managed by the source node's bundle 859 protocol agent that may be reset to zero whenever the current time 860 advances by one second. For nodes that lack accurate clocks, it is 861 recommended that bundle creation time be set to zero and that the 862 counter used as the source of the bundle sequence count never be 863 reset to zero. Note that, in general, the creation of two distinct 864 bundles with the same source node ID and bundle creation timestamp 865 may result in unexpected network behavior and/or suboptimal 866 performance. The combination of source node ID and bundle creation 867 timestamp serves to identify a single transmission request, enabling 868 it to be acknowledged by the receiving application (provided the 869 source node ID is not the null endpoint ID). 871 Lifetime: The lifetime field is an unsigned integer that indicates 872 the time at which the bundle's payload will no longer be useful, 873 encoded as a number of microseconds past the creation time. (For 874 high-rate deployments with very brief disruptions, fine-grained 875 expression of bundle lifetime may be useful.) When a bundle's age 876 exceeds its lifetime, bundle nodes need no longer retain or forward 877 the bundle; the bundle SHOULD be deleted from the network. Bundle 878 lifetime SHALL be represented as a CBOR unsigned integer item. 880 Fragment offset: If and only if the Bundle Processing Control Flags 881 of this Primary block indicate that the bundle is a fragment, 882 fragment offset SHALL be present in the primary block. Fragment 883 offset SHALL be represented as a CBOR unsigned integer indicating 884 the offset from the start of the original application data unit at 885 which the bytes comprising the payload of this bundle were located. 887 CRC: If and only if the value of the CRC type field of this Primary 888 block is non-zero, a CRC SHALL be present in the primary block. The 889 length and nature of the CRC SHALL be as indicated by the CRC type. 890 The CRC SHALL be computed over the concatenation of all bytes 891 (including CBOR "break" characters) of the primary block including 892 the CRC field itself, which for this purpose SHALL be temporarily 893 populated with the value zero. 895 4.2.3. Canonical Bundle Block Format 897 Every block other than the primary block (all such blocks are termed 898 "canonical" blocks) SHALL be represented as a CBOR array; the number 899 of elements in the array SHALL be 6 (if CRC type is zero) or 7 900 (otherwise). 902 The fields of every canonical block SHALL be as follows, listed in 903 the order in which they MUST appear: 905 . Block type code, an unsigned integer. Bundle block type code 1 906 indicates that the block is a bundle payload block. Block type 907 codes 2 through 9 are explicitly reserved as noted later in 908 this specification. Block type codes 192 through 255 are not 909 reserved and are available for private and/or experimental use. 910 All other block type code values are reserved for future use. 911 . Block number, an unsigned integer. The block number uniquely 912 identifies the block within the bundle, enabling blocks 913 (notably bundle security protocol blocks) to explicitly 914 reference other blocks in the same bundle. Block numbers need 915 not be in continuous sequence, and blocks need not appear in 916 block number sequence in the bundle. The block number of the 917 payload block is always zero. 918 . Block processing control flags as discussed in Section 4.1.4 919 above. 920 . CRC type as discussed in Section 4.1.1 above. 921 . Block data length, an unsigned integer. The block data length 922 field SHALL contain the aggregate length of all remaining 923 fields of the block, i.e., the block-type-specific data fields. 924 Block data length SHALL be represented as a CBOR unsigned 925 integer item. 926 . Block-type-specific data fields, whose nature and order are 927 type-specific and whose aggregate length in octets is the value 928 of the block data length field. For the Payload Block in 929 particular (block type 1), there SHALL be exactly one block- 930 type-specific data field, termed the "payload", which SHALL be 931 an application data unit, or some contiguous extent thereof, 932 represented as a CBOR byte string. 933 . If and only if the value of the CRC type field of this block is 934 non-zero, a CRC. If present, the length and nature of the CRC 935 SHALL be as indicated by the CRC type and the CRC SHALL be 936 computed over the concatenation of all bytes of the block 937 (including CBOR "break" characters) including the CRC field 938 itself, which for this purpose SHALL be temporarily populated 939 with the value zero. 941 4.3. Extension Blocks 943 "Extension blocks" are all blocks other than the primary and payload 944 blocks. Because not all extension blocks are defined in the Bundle 945 Protocol specification (the present document), not all nodes 946 conforming to this specification will necessarily instantiate Bundle 947 Protocol implementations that include procedures for processing 948 (that is, recognizing, parsing, acting on, and/or producing) all 949 extension blocks. It is therefore possible for a node to receive a 950 bundle that includes extension blocks that the node cannot process. 951 The values of the block processing control flags indicate the action 952 to be taken by the bundle protocol agent when this is the case. 954 The following extension blocks are defined in other DTN protocol 955 specification documents as noted: 957 . Block Integrity Block (block type 2) and Block Confidentiality 958 Block (block type 3) are defined in the Bundle Security 959 Protocol specification (work in progress). 960 . Manifest Block (block type 4) is defined in the Manifest 961 Extension Block specification (work in progress). The manifest 962 block identifies the blocks that were present in the bundle at 963 the time it was created. The bundle MUST contain one (1) 964 occurrence of this type of block if the value of the "manifest" 965 flag in the bundle processing control flags is 1; otherwise the 966 bundle MUST NOT contain any Manifest block. 967 . The Flow Label Block (block type 6) is defined in the Flow 968 Label Extension Block specification (work in progress). The 969 flow label block is intended to govern transmission of the 970 bundle by convergence-layer adapters. 972 The following extension blocks are defined in the current document. 974 4.3.1. Previous Node 976 The Previous Node block, block type 7, identifies the node that 977 forwarded this bundle to the local node (i.e., to the node at which 978 the bundle currently resides); its block-type-specific data is the 979 node ID of that forwarder node which SHALL take the form of a node 980 ID represented as described in Section 4.1.5.2. above. If the local 981 node is the source of the bundle, then the bundle MUST NOT contain 982 any previous node block. Otherwise the bundle SHOULD contain one 983 (1) occurrence of this type of block. 985 4.3.2. Bundle Age 987 The Bundle Age block, block type 8, contains the number of seconds 988 that have elapsed between the time the bundle was created and time 989 at which it was most recently forwarded. It is intended for use by 990 nodes lacking access to an accurate clock, to aid in determining the 991 time at which a bundle's lifetime expires. The block-type-specific 992 data of this block is an unsigned integer containing the age of the 993 bundle in seconds, which SHALL be represented as a CBOR unsigned 994 integer item. (The age of the bundle is the sum of all known 995 intervals of the bundle's residence at forwarding nodes, up to the 996 time at which the bundle was most recently forwarded, plus the 997 summation of signal propagation time over all episodes of 998 transmission between forwarding nodes. Determination of these 999 values is an implementation matter.) If the bundle's creation time 1000 is zero, then the bundle MUST contain exactly one (1) occurrence of 1001 this type of block; otherwise, the bundle MAY contain at most one 1002 (1) occurrence of this type of block. A bundle MUST NOT contain 1003 multiple occurrences of the bundle age block, as this could result 1004 in processing anomalies. 1006 4.3.3. Hop Count 1008 The Hop Count block, block type 9, contains two unsigned integers, 1009 hop limit and hop count. A "hop" is here defined as an occasion on 1010 which a bundle was forwarded from one node to another node. The hop 1011 limit value SHOULD NOT be changed at any time after creation of the 1012 Hop Count block; the hop count value SHOULD initially be zero and 1013 SHOULD be increased by 1 on each hop. 1015 The hop count block is mainly intended as a safety mechanism, a 1016 means of identifying bundles for removal from the network that can 1017 never be delivered due to a persistent forwarding error. When a 1018 bundle's hop count exceeds its hop limit, the bundle SHOULD be 1019 deleted for the reason "hop limit exceeded", following the bundle 1020 deletion procedure defined in Section 5.10. . Procedures for 1021 determining the appropriate hop limit for a block are beyond the 1022 scope of this specification. The block-type-specific data in a hop 1023 count block SHALL be represented as a CBOR array comprising a 2- 1024 tuple. The first item of this array SHALL be the bundle's hop 1025 limit, represented as a CBOR unsigned integer. The second item of 1026 this array SHALL be the bundle's hop count, represented as a CBOR 1027 unsigned integer. A bundle MAY contain at most one (1) occurrence of 1028 this type of block. 1030 5. Bundle Processing 1032 The bundle processing procedures mandated in this section and in 1033 Section 6 govern the operation of the Bundle Protocol Agent and the 1034 Application Agent administrative element of each bundle node. They 1035 are neither exhaustive nor exclusive. Supplementary DTN protocol 1036 specifications (including, but not restricted to, the Bundle 1037 Security Protocol [BPSEC]) may augment, override, or supersede the 1038 mandates of this document. 1040 5.1. Generation of Administrative Records 1042 All transmission of bundles is in response to bundle transmission 1043 requests presented by nodes' application agents. When required to 1044 "generate" an administrative record (such as a bundle status 1045 report), the bundle protocol agent itself is responsible for causing 1046 a new bundle to be transmitted, conveying that record. In concept, 1047 the bundle protocol agent discharges this responsibility by 1048 directing the administrative element of the node's application agent 1049 to construct the record and request its transmission as detailed in 1050 Section 6 below. In practice, the manner in which administrative 1051 record generation is accomplished is an implementation matter, 1052 provided the constraints noted in Section 6 are observed. 1054 Under some circumstances, the requesting of status reports could 1055 result in an unacceptable increase in the bundle traffic in the 1056 network. For this reason, the generation of status reports MUST be 1057 disabled by default and enabled only when the risk of excessive 1058 network traffic is deemed acceptable. 1060 When the generation of status reports is enabled, the decision on 1061 whether or not to generate a requested status report is left to the 1062 discretion of the bundle protocol agent. Mechanisms that could 1063 assist in making such decisions, such as pre-placed agreements 1064 authorizing the generation of status reports under specified 1065 circumstances, are beyond the scope of this specification. 1067 Notes on administrative record terminology: 1069 . A "bundle reception status report" is a bundle status report 1070 with the "reporting node received bundle" flag set to 1. 1071 . A "bundle forwarding status report" is a bundle status report 1072 with the "reporting node forwarded the bundle" flag set to 1. 1073 . A "bundle delivery status report" is a bundle status report 1074 with the "reporting node delivered the bundle" flag set to 1. 1075 . A "bundle deletion status report" is a bundle status report 1076 with the "reporting node deleted the bundle" flag set to 1. 1078 5.2. Bundle Transmission 1080 The steps in processing a bundle transmission request are: 1082 Step 1: Transmission of the bundle is initiated. An outbound bundle 1083 MUST be created per the parameters of the bundle transmission 1084 request, with the retention constraint "Dispatch pending". The 1085 source node ID of the bundle MUST be either the null endpoint ID, 1086 indicating that the source of the bundle is anonymous, or else the 1087 EID of a singleton endpoint whose only member is the node of which 1088 the BPA is a component. 1090 Step 2: Processing proceeds from Step 1 of Section 5.4. 1092 5.3. Bundle Dispatching 1094 The steps in dispatching a bundle are: 1096 Step 1: If the bundle's destination endpoint is an endpoint of which 1097 the node is a member, the bundle delivery procedure defined in 1098 Section 5.7 MUST be followed and for the purposes of all subsequent 1099 processing of this bundle at this node the node's membership in the 1100 bundle's destination endpoint SHALL be disavowed. 1102 Step 2: Processing proceeds from Step 1 of Section 5.4. 1104 5.4. Bundle Forwarding 1106 The steps in forwarding a bundle are: 1108 Step 1: The retention constraint "Forward pending" MUST be added to 1109 the bundle, and the bundle's "Dispatch pending" retention constraint 1110 MUST be removed. 1112 Step 2: The bundle protocol agent MUST determine whether or not 1113 forwarding is contraindicated for any of the reasons listed in 1114 Figure 4. In particular: 1116 . The bundle protocol agent MAY choose either to forward the 1117 bundle directly to its destination node(s) (if possible) or to 1118 forward the bundle to some other node(s) for further 1119 forwarding. The manner in which this decision is made may 1120 depend on the scheme name in the destination endpoint ID and/or 1121 on other state but in any case is beyond the scope of this 1122 document. If the BPA elects to forward the bundle to some other 1123 node(s) for further forwarding but finds it impossible to 1124 select any node(s) to forward the bundle to, then forwarding is 1125 contraindicated. 1126 . Provided the bundle protocol agent succeeded in selecting the 1127 node(s) to forward the bundle to, the bundle protocol agent 1128 MUST select the convergence layer adapter(s) whose services 1129 will enable the node to send the bundle to those nodes. The 1130 manner in which specific appropriate convergence layer adapters 1131 are selected is beyond the scope of this document. If the agent 1132 finds it impossible to select any appropriate convergence layer 1133 adapter(s) to use in forwarding this bundle, then forwarding is 1134 contraindicated. 1136 Step 3: If forwarding of the bundle is determined to be 1137 contraindicated for any of the reasons listed in Figure 4, then the 1138 Forwarding Contraindicated procedure defined in Section 5.4.1 MUST 1139 be followed; the remaining steps of Section 5 are skipped at this 1140 time. 1142 Step 4: For each node selected for forwarding, the bundle protocol 1143 agent MUST invoke the services of the selected convergence layer 1144 adapter(s) in order to effect the sending of the bundle to that 1145 node. Determining the time at which the bundle protocol agent 1146 invokes convergence layer adapter services is a BPA implementation 1147 matter. Determining the time at which each convergence layer 1148 adapter subsequently responds to this service invocation by sending 1149 the bundle is a convergence-layer adapter implementation matter. 1150 Note that: 1152 . If the bundle contains a flow label extension block (to be 1153 defined in a future document) then that flow label value MAY 1154 identify procedures for determining the order in which 1155 convergence layer adapters must send bundles, e.g., considering 1156 bundle source when determining the order in which bundles are 1157 sent. The definition of such procedures is beyond the scope of 1158 this specification. 1159 . If the bundle has a bundle age block, as defined in 4.3.2. 1160 above, then at the last possible moment before the CLA 1161 initiates conveyance of the bundle node via the CL protocol the 1162 bundle age value MUST be increased by the difference between 1163 the current time and the time at which the bundle was received 1164 (or, if the local node is the source of the bundle, created). 1166 Step 5: When all selected convergence layer adapters have informed 1167 the bundle protocol agent that they have concluded their data 1168 sending procedures with regard to this bundle: 1170 . If the "request reporting of bundle forwarding" flag in the 1171 bundle's status report request field is set to 1, and status 1172 reporting is enabled, then a bundle forwarding status report 1173 SHOULD be generated, destined for the bundle's report-to 1174 endpoint ID. The reason code on this bundle forwarding status 1175 report MUST be "no additional information". 1176 . If any applicable bundle protocol extensions mandate generation 1177 of status reports upon conclusion of convergence-layer data 1178 sending procedures, all such status reports SHOULD be generated 1179 with extension-mandated reason codes. 1180 . The bundle's "Forward pending" retention constraint MUST be 1181 removed. 1183 5.4.1. Forwarding Contraindicated 1185 The steps in responding to contraindication of forwarding are: 1187 Step 1: The bundle protocol agent MUST determine whether or not to 1188 declare failure in forwarding the bundle. Note: this decision is 1189 likely to be influenced by the reason for which forwarding is 1190 contraindicated. 1192 Step 2: If forwarding failure is declared, then the Forwarding 1193 Failed procedure defined in Section 5.4.2 MUST be followed. 1195 Otherwise, when -- at some future time - the forwarding of this 1196 bundle ceases to be contraindicated, processing proceeds from Step 4 1197 of Section 5.4. 1199 5.4.2. Forwarding Failed 1201 The steps in responding to a declaration of forwarding failure are: 1203 Step 1: The bundle protocol agent MAY forward the bundle back to the 1204 node that sent it, as identified by the Previous Node block, if 1205 present. This forwarding, if performed, SHALL be accomplished by 1206 performing Step 4 and Step 5 of section 5.4 where the sole node 1207 selected for forwarding SHALL be the node that sent the bundle. 1209 Step 2: If the bundle's destination endpoint is an endpoint of which 1210 the node is a member, then the bundle's "Forward pending" retention 1211 constraint MUST be removed. Otherwise, the bundle MUST be deleted: 1212 the bundle deletion procedure defined in Section 5.10 MUST be 1213 followed, citing the reason for which forwarding was determined to 1214 be contraindicated. 1216 5.5. Bundle Expiration 1218 A bundle expires when the bundle's age exceeds its lifetime as 1219 specified in the primary bundle block. Bundle age MAY be determined 1220 by subtracting the bundle's creation timestamp time from the current 1221 time if (a) that timestamp time is not zero and (b) the local node's 1222 clock is known to be accurate; otherwise bundle age MUST be obtained 1223 from the Bundle Age extension block. Bundle expiration MAY occur at 1224 any point in the processing of a bundle. When a bundle expires, the 1225 bundle protocol agent MUST delete the bundle for the reason 1226 "lifetime expired": the bundle deletion procedure defined in Section 1227 5.10 MUST be followed. 1229 5.6. Bundle Reception 1231 The steps in processing a bundle that has been received from another 1232 node are: 1234 Step 1: The retention constraint "Dispatch pending" MUST be added to 1235 the bundle. 1237 Step 2: If the "request reporting of bundle reception" flag in the 1238 bundle's status report request field is set to 1, and status 1239 reporting is enabled, then a bundle reception status report with 1240 reason code "No additional information" SHOULD be generated, 1241 destined for the bundle's report-to endpoint ID. 1243 Step 3: For each block in the bundle that is an extension block that 1244 the bundle protocol agent cannot process: 1246 . If the block processing flags in that block indicate that a 1247 status report is requested in this event, and status reporting 1248 is enabled, then a bundle reception status report with reason 1249 code "Block unintelligible" SHOULD be generated, destined for 1250 the bundle's report-to endpoint ID. 1251 . If the block processing flags in that block indicate that the 1252 bundle must be deleted in this event, then the bundle protocol 1253 agent MUST delete the bundle for the reason "Block 1254 unintelligible"; the bundle deletion procedure defined in 1255 Section 5.10 MUST be followed and all remaining steps of the 1256 bundle reception procedure MUST be skipped. 1257 . If the block processing flags in that block do NOT indicate 1258 that the bundle must be deleted in this event but do indicate 1259 that the block must be discarded, then the bundle protocol 1260 agent MUST remove this block from the bundle. 1261 . If the block processing flags in that block indicate neither 1262 that the bundle must be deleted nor that that the block must be 1263 discarded, then processing continues with the next extension 1264 block that the bundle protocol agent cannot process, if any; 1265 otherwise, processing proceeds from step 4. 1267 Step 4: Processing proceeds from Step 1 of Section 5.3. 1269 5.7. Local Bundle Delivery 1271 The steps in processing a bundle that is destined for an endpoint of 1272 which this node is a member are: 1274 Step 1: If the received bundle is a fragment, the application data 1275 unit reassembly procedure described in Section 5.9 MUST be followed. 1276 If this procedure results in reassembly of the entire original 1277 application data unit, processing of this bundle (whose fragmentary 1278 payload has been replaced by the reassembled application data unit) 1279 proceeds from Step 2; otherwise, the retention constraint 1280 "Reassembly pending" MUST be added to the bundle and all remaining 1281 steps of this procedure MUST be skipped. 1283 Step 2: Delivery depends on the state of the registration whose 1284 endpoint ID matches that of the destination of the bundle: 1286 . An additional implementation-specific delivery deferral 1287 procedure MAY optionally be associated with the registration. 1288 . If the registration is in the Active state, then the bundle 1289 MUST be delivered automatically as soon as it is the next 1290 bundle that is due for delivery according to the BPA's bundle 1291 delivery scheduling policy, an implementation matter. 1292 . If the registration is in the Passive state, or if delivery of 1293 the bundle fails for some implementation-specific reason, then 1294 the registration's delivery failure action MUST be taken. 1295 Delivery failure action MUST be one of the following: 1297 o defer delivery of the bundle subject to this registration 1298 until (a) this bundle is the least recently received of 1299 all bundles currently deliverable subject to this 1300 registration and (b) either the registration is polled or 1301 else the registration is in the Active state, and also 1302 perform any additional delivery deferral procedure 1303 associated with the registration; or 1305 o abandon delivery of the bundle subject to this registration 1306 (as defined in 3.1. ). 1308 Step 3: As soon as the bundle has been delivered, if the "request 1309 reporting of bundle delivery" flag in the bundle's status report 1310 request field is set to 1 and bundle status reporting is enabled, 1311 then a bundle delivery status report SHOULD be generated, destined 1312 for the bundle's report-to endpoint ID. Note that this status report 1313 only states that the payload has been delivered to the application 1314 agent, not that the application agent has processed that payload. 1316 5.8. Bundle Fragmentation 1318 It may at times be advantageous for bundle protocol agents to reduce 1319 the sizes of bundles in order to forward them. This might be the 1320 case, for example, if a node to which a bundle is to be forwarded is 1321 accessible only via intermittent contacts and no upcoming contact is 1322 long enough to enable the forwarding of the entire bundle. 1324 The size of a bundle can be reduced by "fragmenting" the bundle. To 1325 fragment a bundle whose payload is of size M is to replace it with 1326 two "fragments" -- new bundles with the same source node ID and 1327 creation timestamp as the original bundle -- whose payloads are the 1328 first N and the last (M - N) bytes of the original bundle's payload, 1329 where 0 < N < M. Note that fragments may themselves be fragmented, 1330 so fragmentation may in effect replace the original bundle with more 1331 than two fragments. (However, there is only one 'level' of 1332 fragmentation, as in IP fragmentation.) 1334 Any bundle whose primary block's bundle processing flags do NOT 1335 indicate that it must not be fragmented MAY be fragmented at any 1336 time, for any purpose, at the discretion of the bundle protocol 1337 agent. NOTE, however, that some combinations of bundle 1338 fragmentation, replication, and routing might result in unexpected 1339 traffic patterns. 1341 Fragmentation SHALL be constrained as follows: 1343 . The concatenation of the payloads of all fragments produced by 1344 fragmentation MUST always be identical to the payload of the 1345 fragmented bundle (that is, the bundle that is being 1346 fragmented). Note that the payloads of fragments resulting from 1347 different fragmentation episodes, in different parts of the 1348 network, may be overlapping subsets of the fragmented bundle's 1349 payload. 1350 . The primary block of each fragment MUST differ from that of the 1351 fragmented bundle, in that the bundle processing flags of the 1352 fragment MUST indicate that the bundle is a fragment and both 1353 fragment offset and total application data unit length must be 1354 provided. Additionally, the CRC of the primary block of the 1355 fragmented bundle, if any, MUST be replaced in each fragment by 1356 a new CRC computed for the primary block of that fragment. 1358 . The payload blocks of fragments will differ from that of the 1359 fragmented bundle as noted above. 1360 . If the fragmented bundle is not a fragment or is the fragment 1361 with offset zero, then all extension blocks of the fragmented 1362 bundle MUST be replicated in the fragment whose offset is zero. 1363 . Each of the fragmented bundle's extension blocks whose "Block 1364 must be replicated in every fragment" flag is set to 1 MUST be 1365 replicated in every fragment. 1366 . Beyond these rules, replication of extension blocks in the 1367 fragments is an implementation matter. 1369 5.9. Application Data Unit Reassembly 1371 If the concatenation -- as informed by fragment offsets and payload 1372 lengths -- of the payloads of all previously received fragments with 1373 the same source node ID and creation timestamp as this fragment, 1374 together with the payload of this fragment, forms a byte array whose 1375 length is equal to the total application data unit length in the 1376 fragment's primary block, then: 1378 . This byte array -- the reassembled application data unit -- 1379 MUST replace the payload of this fragment. 1380 . The "Reassembly pending" retention constraint MUST be removed 1381 from every other fragment whose payload is a subset of the 1382 reassembled application data unit. 1384 Note: reassembly of application data units from fragments occurs at 1385 the nodes that are members of destination endpoints as necessary; an 1386 application data unit MAY also be reassembled at some other node on 1387 the path to the destination. 1389 5.10. Bundle Deletion 1391 The steps in deleting a bundle are: 1393 Step 1: If the "request reporting of bundle deletion" flag in the 1394 bundle's status report request field is set to 1, and if status 1395 reporting is enabled, then a bundle deletion status report citing 1396 the reason for deletion SHOULD be generated, destined for the 1397 bundle's report-to endpoint ID. 1399 Step 2: All of the bundle's retention constraints MUST be removed. 1401 5.11. Discarding a Bundle 1403 As soon as a bundle has no remaining retention constraints it MAY be 1404 discarded, thereby releasing any persistent storage that may have 1405 been allocated to it. 1407 5.12. Canceling a Transmission 1409 When requested to cancel a specified transmission, where the bundle 1410 created upon initiation of the indicated transmission has not yet 1411 been discarded, the bundle protocol agent MUST delete that bundle 1412 for the reason "transmission cancelled". For this purpose, the 1413 procedure defined in Section 5.10 MUST be followed. 1415 6. Administrative Record Processing 1417 6.1. Administrative Records 1419 Administrative records are standard application data units that are 1420 used in providing some of the features of the Bundle Protocol. One 1421 type of administrative record has been defined to date: bundle 1422 status reports. Note that additional types of administrative 1423 records may be defined by supplementary DTN protocol specification 1424 documents. 1426 Every administrative record consists of: 1428 . Record type code (an unsigned integer for which valid values 1429 are as defined below). 1430 . Record content in type-specific format. 1432 Valid administrative record type codes are defined as follows: 1434 +---------+--------------------------------------------+ 1436 | Value | Meaning | 1438 +=========+============================================+ 1440 | 1 | Bundle status report. | 1442 +---------+--------------------------------------------+ 1444 | (other) | Reserved for future use. | 1446 +---------+--------------------------------------------+ 1447 Figure 3: Administrative Record Type Codes 1449 Each BP administrative record SHALL be represented as a CBOR array 1450 comprising a 2-tuple. 1452 The first item of the array SHALL be a record type code, which SHALL 1453 be represented as a CBOR unsigned integer. 1455 The second element of this array SHALL be the applicable CBOR 1456 representation of the content of the record. Details of the CBOR 1457 representation of administrative record type 1 are provided below. 1458 Details of the CBOR representation of other types of administrative 1459 record type are included in the specifications defining those 1460 records. 1462 6.1.1. Bundle Status Reports 1464 The transmission of "bundle status reports" under specified 1465 conditions is an option that can be invoked when transmission of a 1466 bundle is requested. These reports are intended to provide 1467 information about how bundles are progressing through the system, 1468 including notices of receipt, forwarding, final delivery, and 1469 deletion. They are transmitted to the Report-to endpoints of 1470 bundles. 1472 Each bundle status report SHALL be represented as a CBOR array. The 1473 number of elements in the array SHALL be either 6 (if the subject 1474 bundle is a fragment) or 4 (otherwise). 1476 The first item of the bundle status report array SHALL be bundle 1477 status information represented as a CBOR array of at least 4 1478 elements. The first four items of the bundle status information 1479 array shall provide information on the following four status 1480 assertions, in this order: 1482 . Reporting node received bundle. 1483 . Reporting node forwarded the bundle. 1484 . Reporting node delivered the bundle. 1485 . Reporting node deleted the bundle. 1487 Each item of the bundle status information array SHALL be a bundle 1488 status item represented as a CBOR array; the number of elements in 1489 each such array SHALL be either 2 (if the value of the first item of 1490 this bundle status item is 1 AND the "Report status time" flag was 1491 set to 1 in the bundle processing flags of the bundle whose status 1492 is being reported) or 1 (otherwise). The first item of the bundle 1493 status item array SHALL be a status indicator, a Boolean value 1494 indicating whether or not the corresponding bundle status is 1495 asserted, represented as a CBOR Boolean value. The second item of 1496 the bundle status item array, if present, SHALL indicate the time 1497 (as reported by the local system clock, an implementation matter) at 1498 which the indicated status was asserted for this bundle, represented 1499 as a DTN time as described in Section 4.1.6. above. 1501 The second item of the bundle status report array SHALL be the 1502 bundle status report reason code explaining the value of the status 1503 indicator, represented as a CBOR unsigned integer. Valid status 1504 report reason codes are defined in Figure 4 below but the list of 1505 status report reason codes provided here is neither exhaustive nor 1506 exclusive; supplementary DTN protocol specifications (including, but 1507 not restricted to, the Bundle Security Protocol [BPSEC]) may define 1508 additional reason codes. 1510 +---------+--------------------------------------------+ 1512 | Value | Meaning | 1514 +=========+============================================+ 1516 | 0 | No additional information. | 1518 +---------+--------------------------------------------+ 1520 | 1 | Lifetime expired. | 1522 +---------+--------------------------------------------+ 1524 | 2 | Forwarded over unidirectional link. | 1526 +---------+--------------------------------------------+ 1528 | 3 | Transmission canceled. | 1530 +---------+--------------------------------------------+ 1532 | 4 | Depleted storage. | 1534 +---------+--------------------------------------------+ 1536 | 5 | Destination endpoint ID unintelligible. | 1538 +---------+--------------------------------------------+ 1540 | 6 | No known route to destination from here. | 1541 +---------+--------------------------------------------+ 1543 | 7 | No timely contact with next node on route. | 1545 +---------+--------------------------------------------+ 1547 | 8 | Block unintelligible. | 1549 +---------+--------------------------------------------+ 1551 | 9 | Hop limit exceeded. | 1553 +---------+--------------------------------------------+ 1555 | (other) | Reserved for future use. | 1557 +---------+--------------------------------------------+ 1559 Figure 4: Status Report Reason Codes 1561 The third item of the bundle status report array SHALL be the source 1562 node ID identifying the source of the bundle whose status is being 1563 reported, represented as described in Section 4.1.5.2. above. 1565 The fourth item of the bundle status report array SHALL be the 1566 creation timestamp of the bundle whose status is being reported, 1567 represented as described in Section 4.1.7. above. 1569 The fifth item of the bundle status report array SHALL be present if 1570 and only if the bundle whose status is being reported contained a 1571 fragment offset. If present, it SHALL be the subject bundle's 1572 fragment offset represented as a CBOR unsigned integer item. 1574 The sixth item of the bundle status report array SHALL be present if 1575 and only if the bundle whose status is being reported contained a 1576 fragment offset. If present, it SHALL be the length of the subject 1577 bundle's payload represented as a CBOR unsigned integer item. 1579 6.2. Generation of Administrative Records 1581 Whenever the application agent's administrative element is directed 1582 by the bundle protocol agent to generate an administrative record 1583 with reference to some bundle, the following procedure must be 1584 followed: 1586 Step 1: The administrative record must be constructed. If the 1587 administrative record references a bundle and the referenced bundle 1588 is a fragment, the administrative record MUST contain the fragment 1589 offset and fragment length. 1591 Step 2: A request for transmission of a bundle whose payload is this 1592 administrative record MUST be presented to the bundle protocol 1593 agent. 1595 7. Services Required of the Convergence Layer 1597 7.1. The Convergence Layer 1599 The successful operation of the end-to-end bundle protocol depends 1600 on the operation of underlying protocols at what is termed the 1601 "convergence layer"; these protocols accomplish communication 1602 between nodes. A wide variety of protocols may serve this purpose, 1603 so long as each convergence layer protocol adapter provides a 1604 defined minimal set of services to the bundle protocol agent. This 1605 convergence layer service specification enumerates those services. 1607 7.2. Summary of Convergence Layer Services 1609 Each convergence layer protocol adapter is expected to provide the 1610 following services to the bundle protocol agent: 1612 . sending a bundle to a bundle node that is reachable via the 1613 convergence layer protocol; 1614 . delivering to the bundle protocol agent a bundle that was sent 1615 by a bundle node via the convergence layer protocol. 1617 The convergence layer service interface specified here is neither 1618 exhaustive nor exclusive. That is, supplementary DTN protocol 1619 specifications (including, but not restricted to, the Bundle 1620 Security Protocol [BPSEC]) may expect convergence layer adapters 1621 that serve BP implementations conforming to those protocols to 1622 provide additional services such as reporting on the transmission 1623 and/or reception progress of individual bundles (at completion 1624 and/or incrementally), retransmitting data that were lost in 1625 transit, discarding bundle-conveying data units that the convergence 1626 layer protocol determines are corrupt or inauthentic, or reporting 1627 on the integrity and/or authenticity of delivered bundles. 1629 8. Implementation Status 1631 [NOTE to the RFC Editor: please remove this section before 1632 publication, as well as the reference to RFC 7942.] 1633 This section records the status of known implementations of the 1634 protocol defined by this specification at the time of posting of 1635 this Internet-Draft, and is based on a proposal described in RFC 1636 7942. The description of implementations in this section is 1637 intended to assist the IETF in its decision processes in progressing 1638 drafts to RFCs. Please note that the listing of any individual 1639 implementation here does not imply endorsement by the IETF. 1640 Furthermore, no effort has been spent to verify the information 1641 presented here that was supplied by IETF contributors. This is not 1642 intended as, and must not be construed to be, a catalog of available 1643 implementations or their features. Readers are advised to note that 1644 other implementations may exist. 1646 According to RFC 7942, "this will allow reviewers and working groups 1647 to assign due consideration to documents that have the benefit of 1648 running code, which may serve as evidence of valuable 1649 experimentation and feedback that have made the implemented 1650 protocols more mature. It is up to the individual working groups to 1651 use this information as they see fit". 1653 At the time of this writing, the only known implementation of the 1654 current document is microPCN (https://upcn.eu/). According to the 1655 developers: 1657 The Micro Planetary Communication Network (uPCN) is a free 1658 software project intended to offer an implementation of Delay- 1659 tolerant Networking protocols for POSIX operating systems (well, 1660 and for Linux) plus for the ARM Cortex STM32F4 microcontroller 1661 series. More precisely it currently provides an implementation of 1663 . the Bundle Protocol (BP, RFC 5050), 1664 . the Bundle Protocol version 7 specification draft (version 6), 1665 . the DTN IP Neighbor Discovery (IPND) protocol, and 1666 . a routing approach optimized for message-ferry micro LEO 1667 satellites. 1669 uPCN is written in C and is built upon the real-time operating 1670 system FreeRTOS. The source code of uPCN is released under the 1671 "BSD 3-Clause License". 1673 The project depends on an execution environment offering link 1674 layer protocols such as AX.25. The source code uses the USB 1675 subsystem to interact with the environment. 1677 9. Security Considerations 1679 The bundle protocol security architecture and the available security 1680 services are specified in an accompanying document, the Bundle 1681 Security Protocol specification [BPSEC]. 1683 The bpsec extensions to Bundle Protocol enable each block of a 1684 bundle (other than a bpsec extension block) to be individually 1685 authenticated by a signature block (Block Integrity Block, or BIB) 1686 and also enable each block of a bundle other than the primary block 1687 (and the bpsec extension blocks themselves) to be individually 1688 encrypted by a BCB. 1690 Because the security mechanisms are extension blocks that are 1691 themselves inserted into the bundle, the integrity and 1692 confidentiality of bundle blocks are protected while the bundle is 1693 at rest, awaiting transmission at the next forwarding opportunity, 1694 as well as in transit. 1696 Additionally, convergence-layer protocols that ensure authenticity 1697 of communication between adjacent nodes in BP network topology 1698 SHOULD be used where available, to minimize the ability of 1699 unauthenticated nodes to introduce inauthentic traffic into the 1700 network. 1702 Note that, while the primary block must remain in the clear for 1703 routing purposes, the Bundle Protocol can be protected against 1704 traffic analysis to some extent by using bundle-in-bundle 1705 encapsulation to tunnel bundles to a safe forward distribution 1706 point: the encapsulated bundle forms the payload of an encapsulating 1707 bundle, and that payload block may be encrypted by a BCB. 1709 Note that the generation of bundle status reports is disabled by 1710 default because malicious initiation of bundle status reporting 1711 could result in the transmission of extremely large numbers of 1712 bundle, effecting a denial of service attack. 1714 The bpsec extensions accommodate an open-ended range of 1715 ciphersuites; different ciphersuites may be utilized to protect 1716 different blocks. One possible variation is to sign and/or encrypt 1717 blocks in symmetric keys securely formed by Diffie-Hellman 1718 procedures (such as EKDH) using the public and private keys of the 1719 sending and receiving nodes. For this purpose, the key distribution 1720 problem reduces to the problem of trustworthy delay-tolerant 1721 distribution of public keys, a current research topic. 1723 Bundle security MUST NOT be invalidated by forwarding nodes even 1724 though they themselves might not use the Bundle Security Protocol. 1726 In particular, while blocks MAY be added to bundles transiting 1727 intermediate nodes, removal of blocks with the "Discard block if it 1728 can't be processed" flag set in the block processing control flags 1729 may cause security to fail. 1731 Inclusion of the Bundle Security Protocol in any Bundle Protocol 1732 implementation is RECOMMENDED. Use of the Bundle Security Protocol 1733 in Bundle Protocol operations is OPTIONAL, subject to the following 1734 guidelines: 1736 . Every block (that is not a bpsec extension block) of every 1737 bundle SHOULD be authenticated by a BIB citing the ID of the 1738 node that inserted that block. (Note that a single BIB may 1739 authenticate multiple "target" blocks.) BIB authentication MAY 1740 be omitted on (and only on) any initial end-to-end path 1741 segments on which it would impose unacceptable overhead, 1742 provided that satisfactory authentication is ensured at the 1743 convergence layer and that BIB authentication is asserted on 1744 the first path segment on which the resulting overhead is 1745 acceptable and on all subsequent path segments. 1746 . If any segment of the end-to-end path of a bundle will traverse 1747 the Internet or any other potentially insecure communication 1748 environment, then the payload block SHOULD be encrypted by a 1749 BCB on this path segment and all subsequent segments of the 1750 end-to-end path. 1752 10. IANA Considerations 1754 This document defines the following additional Bundle Protocol block 1755 types, for which values are to be assigned from the Bundle 1756 Administrative Record Types namespace [RFC6255]: 1758 Value Name Meaning Reference 1760 ----- ------------- ----------------------------- ---------- 1762 7 Previous node Identifies sender This document 1764 8 Bundle age Bundle age in seconds This document 1766 9 Hop count #prior transmission attempts This document 1768 This document also defines a new URI scheme type field - an unsigned 1769 integer of undefined length - for which IANA is to create and 1770 maintain a new registry named "URI scheme type values". Initial 1771 values for the Bundle Protocol URI scheme type registry are given 1772 below; future assignments are to be made through Expert Review. 1773 Each assignment consists of a URI scheme type name and its 1774 associated value. 1776 Value URI Scheme Type Name Reference 1778 ----- ------------------------ ------------------------------- 1780 0 Reserved 1782 1 dtn RFC5050, Section 4.4 1784 2 ipn RFC6260, Section 4 1786 3-254 Unassigned 1788 255 Reserved 1790 --------------------------------------------------------------- 1792 11. References 1794 11.1. Normative References 1796 [CRC] International Telecommunication Union, "Error-correcting 1797 procedures for DCEs using asynchronous-to-synchronous conversion", 1798 ITU-T Recommendation V.42, March 2002. 1800 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1801 Requirement Levels", BCP 14, RFC 2119, March 1997. 1803 [RFC7049] Borman, C. and P. Hoffman, "Concise Binary Object 1804 Representation (CBOR)", RFC 7049, October 2013. 1806 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1807 Resource Identifier (URI): Generic Syntax", RFC 3986, STD 66, 1808 January 2005. 1810 [URIREG] Thaler, D., Hansen, T., and T. Hardie, "Guidelines and 1811 Registration Procedures for URI Schemes", RFC 7595, BCP 35, June 1812 2015. 1814 11.2. Informative References 1816 [ARCH] V. Cerf et al., "Delay-Tolerant Network Architecture", RFC 1817 4838, April 2007. 1819 [BIBE] Burleigh, S., "Bundle-in-Bundle Encapsulation", Work In 1820 Progress, June 2017. 1822 [BPSEC] Birrane, E., "Bundle Security Protocol Specification", Work 1823 In Progress, October 2015. 1825 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource 1826 Identifiers (IRIs)", RFC 3987, January 2005. 1828 [RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol 1829 IANA Registries", RFC 6255, May 2011. 1831 [SIGC] Fall, K., "A Delay-Tolerant Network Architecture for 1832 Challenged Internets", SIGCOMM 2003. 1834 [UTC] Arias, E. and B. Guinot, "Coordinated universal time UTC: 1835 historical background and perspectives" in "Journees systemes de 1836 reference spatio-temporels", 2004. 1838 12. Acknowledgments 1840 This work is freely adapted from RFC 5050, which was an effort of 1841 the Delay Tolerant Networking Research Group. The following DTNRG 1842 participants contributed significant technical material and/or 1843 inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh, 1844 Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory, 1845 Michael Demmer of the University of California at Berkeley, Robert 1846 Durst, Keith Scott, and Susan Symington of The MITRE Corporation, 1847 Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity 1848 College Dublin, Peter Lovell of SPARTA, Inc., Manikantan Ramadas of 1849 Ohio University, and Howard Weiss of SPARTA, Inc. 1851 This document was prepared using 2-Word-v2.0.template.dot. 1853 13. Significant Changes from RFC 5050 1855 Points on which this draft significantly differs from RFC 5050 1856 include the following: 1858 . Clarify the difference between transmission and forwarding. 1859 . Migrate custody transfer to the bundle-in-bundle encapsulation 1860 specification [BIBE]. 1862 . Introduce the concept of "node ID" as functionally distinct 1863 from endpoint ID, while having the same syntax. 1864 . Restructure primary block, making it immutable. Add optional 1865 CRC. 1866 . Add optional CRCs to non-primary blocks. 1867 . Add block ID number to canonical block format (to support 1868 streamlined BSP). 1869 . Add bundle age extension block, defined in this specification. 1870 . Add previous node extension block, defined in this 1871 specification. 1872 . Add flow label extension block, *not* defined in this 1873 specification. 1874 . Add manifest extension block, *not* defined in this 1875 specification. 1876 . Add hop count extension block, defined in this specification. 1877 . Migrate Quality of Service markings to a new QoS extension 1878 block, *not* defined in this specification. 1880 Appendix A. For More Information 1882 Please refer comments to dtn@ietf.org. DTN Working Group documents 1883 are located at https://datatracker.ietf.org/wg/dtn/documents. The 1884 original Delay Tolerant Networking Research Group (DTNRG) Web site 1885 is located at https://irtf.org/concluded/dtnrg. 1887 Copyright (c) 2017 IETF Trust and the persons identified as authors 1888 of the code. All rights reserved. 1890 Redistribution and use in source and binary forms, with or without 1891 modification, is permitted pursuant to, and subject to the license 1892 terms contained in, the Simplified BSD License set forth in Section 1893 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 1894 (http://trustee.ietf.org/license-info). 1896 Appendix B. CDDL expression 1898 For informational purposes, Carsten Bormann has kindly provided an 1899 expression of the Bundle Protocol specification in the Concise Data 1900 Definition Language (CDDL). That CDDL expression is presented 1901 below, somewhat edited by the authors. Note that wherever the CDDL 1902 expression is in disagreement with the textual representation of the 1903 BP specification presented in the earlier sections of this document, 1904 the textual representation rules. 1906 start = bundle 1908 dtn-time = uint 1910 creation-timestamp = [dtn-time, sequence: uint] 1912 eid-generic = [uri-code, SSP: any] 1914 uri-code = uint 1916 eid = eid-choice .within eid-generic 1918 eid-choice /= [dtn-code, SSP: (text / 0)] 1920 dtn-code = 1 ; TBD 1922 eid-choice /= [ipn-code, SSP: [nodenum: uint, servicenum: uint]] 1924 ipn-code = 2 ; TBD 1926 bundle-control-flags = uint .bits bundleflagbits 1928 bundleflagbits = &( 1930 reserved: 15 1932 reserved: 14 1934 reserved: 13 1936 bundle-deletion-status-reports-are-requested: 12 1938 bundle-delivery-status-reports-are-requested: 11 1940 bundle-forwarding-status-reports-are-requested: 10 1942 reserved: 9 1943 bundle-reception-status-reports-are-requested: 8 1945 bundle-contains-a-Manifest-block: 7 1947 status-time-is-requested-in-all-status-reports: 6 1949 user-application-acknowledgement-is-requested: 5 1951 reserved: 4 1953 reserved: 3 1955 bundle-must-not-be-fragmented: 2 1957 payload-is-an-administrative-record: 1 1959 bundle-is-a-fragment: 0 1961 ) 1963 crc = bytes 1965 block-control-flags = uint .bits blockflagbits 1967 blockflagbits = &( 1969 reserved: 7 1971 reserved: 6 1973 reserved: 5 1975 reserved: 4 1977 bundle-must-be-deleted-if-block-cannot-be-processed: 3 1979 status-report-must-be-transmitted-if-block-cannot-be-processed: 2 1981 block-must-be-removed-from-bundle-if-it-cannot-be-processed: 1 1983 block-must-be-replicated-in-every-fragment: 0 1985 ) 1987 bundle = [primary-block, *extension-block, payload-block] 1989 primary-block = [ 1990 version: 7, 1992 bundle-control-flags, 1994 crc-type: uint, 1996 destination: eid, 1998 source-node: eid, 2000 report-to: eid, 2002 creation-timestamp, 2004 lifetime: uint, 2006 ? fragment-offset: uint, 2008 ? total-application-data-length: uint, 2010 ? crc, 2012 ] 2014 canonical-block-generic = [ 2016 block-type-code: uint, 2018 canonical-block-common, 2020 content: any, 2022 ? crc 2024 ] 2026 canonical-block-common = ( 2028 block-number: uint, 2030 block-control-flags, 2032 crc-type: uint, 2034 block-data-length: uint 2036 ) 2037 canonical-block = canonical-block-choice .within canonical-block- 2038 generic 2040 canonical-block-choice /= payload-block 2042 payload-block = [1, canonical-block-common, adu-extent: payload] 2044 payload = bytes / bytes .cbor admin-record 2046 canonical-block-choice /= extension-block 2048 extension-block = extension-block-choice .within canonical-block 2050 extension-block-choice /= previous-node-block 2052 previous-node-block = [7, canonical-block-common, eid] 2054 extension-block-choice /= bundle-age-block 2056 bundle-age-block = [8, canonical-block-common, bundle-age: uint] 2058 extension-block-choice /= hop-count-block 2060 hop-count-block = [9, canonical-block-common, 2062 [hop-limit: uint, 2064 hop-count: uint] 2066 ] 2068 admin-record-generic = [record-type: uint, any] 2070 admin-record = admin-record-choice .within admin-record-generic 2072 admin-record-choice /= bundle-status-report 2074 bundle-status-report = [1, [bundle-status-information, 2076 bundle-status-reason: uint, 2078 admin-common] 2080 ] 2081 admin-common = ( 2083 source-node: eid, 2085 creation-timestamp, 2087 ? fragment-offset: uint, 2089 ? payload-length: uint 2091 ) 2093 bundle-status-information = [ 2095 reporting-node-received-bundle: bundle-status-item, 2097 reporting-node-forwarded-the-bundle: bundle-status-item, 2099 reporting-node-delivered-the-bundle: bundle-status-item, 2101 reporting-node-deleted-the-bundle: bundle-status-item, 2103 ] 2105 bundle-status-item = [ 2107 asserted: bool, 2109 ? time-of-assertion: dtn-time 2111 ] 2113 Authors' Addresses 2115 Scott Burleigh 2116 Jet Propulsion Laboratory, California Institute of Technology 2117 4800 Oak Grove Dr. 2118 Pasadena, CA 91109-8099 2119 US 2120 Phone: +1 818 393 3353 2121 Email: Scott.Burleigh@jpl.nasa.gov 2122 Kevin Fall 2123 Nefeli Networks, Inc. 2124 2150 Shattuck Ave. 2125 Berkeley, CA 94704 2126 US 2127 Email: kfall@kfall.com 2129 Edward J. Birrane 2130 Johns Hopkins University Applied Physics Laboratory 2131 11100 Johns Hopkins Rd 2132 Laurel, MD 20723 2133 US 2134 Phone: +1 443 778 7423 2135 Email: Edward.Birrane@jhuapl.edu