Internet DRAFT - draft-ietf-dtn-bpbis
draft-ietf-dtn-bpbis
Delay-Tolerant Networking Working Group S. Burleigh
Internet Draft JPL, Calif. Inst. Of Technology
Intended status: Standards Track K. Fall
Expires: July 29, 2021 Roland Computing Services
E. Birrane
APL, Johns Hopkins University
January 25, 2021
Bundle Protocol Version 7
draft-ietf-dtn-bpbis-31.txt
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Abstract
This Internet Draft presents a specification for the Bundle
Protocol, adapted from the experimental Bundle Protocol
specification developed by the Delay-Tolerant Networking Research
group of the Internet Research Task Force and documented in RFC
5050.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................5
3. Service Description............................................5
3.1. Definitions...............................................5
3.2. Discussion of BP concepts.................................9
3.3. Services Offered by Bundle Protocol Agents...............12
4. Bundle Format.................................................13
4.1. Bundle Structure.........................................13
4.2. BP Fundamental Data Structures...........................14
4.2.1. CRC Type............................................14
4.2.2. CRC.................................................14
4.2.3. Bundle Processing Control Flags.....................15
4.2.4. Block Processing Control Flags......................16
4.2.5. Identifiers.........................................17
4.2.5.1. Endpoint ID....................................17
4.2.5.1.1. The "dtn" URI scheme......................18
4.2.5.1.2. The "ipn" URI scheme......................20
4.2.5.2. Node ID........................................22
4.2.6. DTN Time............................................22
4.2.7. Creation Timestamp..................................22
4.2.8. Block-type-specific Data............................23
4.3. Block Structures.........................................23
4.3.1. Primary Bundle Block................................23
4.3.2. Canonical Bundle Block Format.......................26
4.4. Extension Blocks.........................................27
4.4.1. Previous Node.......................................27
4.4.2. Bundle Age..........................................28
4.4.3. Hop Count...........................................28
5. Bundle Processing.............................................29
5.1. Generation of Administrative Records.....................29
5.2. Bundle Transmission......................................30
5.3. Bundle Dispatching.......................................30
5.4. Bundle Forwarding........................................30
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5.4.1. Forwarding Contraindicated..........................33
5.4.2. Forwarding Failed...................................33
5.5. Bundle Expiration........................................33
5.6. Bundle Reception.........................................34
5.7. Local Bundle Delivery....................................35
5.8. Bundle Fragmentation.....................................36
5.9. Application Data Unit Reassembly.........................37
5.10. Bundle Deletion.........................................38
5.11. Discarding a Bundle.....................................38
5.12. Canceling a Transmission................................38
6. Administrative Record Processing..............................38
6.1. Administrative Records...................................38
6.1.1. Bundle Status Reports...............................39
6.2. Generation of Administrative Records.....................42
7. Services Required of the Convergence Layer....................43
7.1. The Convergence Layer....................................43
7.2. Summary of Convergence Layer Services....................43
8. Implementation Status.........................................44
9. Security Considerations.......................................45
10. IANA Considerations..........................................47
10.1. Bundle Block Types......................................47
10.2. Primary Bundle Protocol Version.........................48
10.3. Bundle Processing Control Flags.........................49
10.4. Block Processing Control Flags..........................51
10.5. Bundle Status Report Reason Codes.......................52
10.6. Bundle Protocol URI scheme types........................53
10.7. URI scheme "dtn"........................................54
10.8. URI scheme "ipn"........................................55
11. References...................................................56
11.1. Normative References....................................56
11.2. Informative References..................................56
12. Acknowledgments..............................................57
13. Significant Changes from RFC 5050............................58
Appendix A. For More Information.................................59
Appendix B. CDDL expression......................................60
1. Introduction
Since the publication of the Bundle Protocol Specification
(Experimental RFC 5050 [RFC5050]) in 2007, the Delay-Tolerant
Networking (DTN) Bundle Protocol has been implemented in multiple
programming languages and deployed to a wide variety of computing
platforms. This implementation and deployment experience has
identified opportunities for making the protocol simpler, more
capable, and easier to use. The present document, standardizing the
Bundle Protocol (BP), is adapted from RFC 5050 in that context,
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reflecting lessons learned. Significant changes from the Bundle
Protocol specification defined in RFC 5050 are listed in section 13.
This document describes version 7 of BP.
Delay Tolerant Networking is a network architecture providing
communications in and/or through highly stressed environments.
Stressed networking environments include those with intermittent
connectivity, large and/or variable delays, and high bit error
rates. To provide its services, BP may be viewed as sitting at the
application layer of some number of constituent networks, forming a
store-carry-forward overlay network. Key capabilities of BP
include:
. Ability to use physical motility for the movement of data
. Ability to move the responsibility for error control from one
node to another
. Ability to cope with intermittent connectivity, including cases
where the sender and receiver are not concurrently present in
the network
. Ability to take advantage of scheduled, predicted, and
opportunistic connectivity, whether bidirectional or
unidirectional, in addition to continuous connectivity
. Late binding of overlay network endpoint identifiers to
underlying constituent network addresses
For descriptions of these capabilities and the rationale for the DTN
architecture, see [ARCH] and [SIGC].
BP's location within the standard protocol stack is as shown in
Figure 1. BP uses underlying "native" transport and/or network
protocols for communications within a given constituent network.
The layer at which those underlying protocols are located is here
termed the "convergence layer" and the interface between the bundle
protocol and a specific underlying protocol is termed a "convergence
layer adapter".
Figure 1 shows three distinct transport and network protocols
(denoted T1/N1, T2/N2, and T3/N3).
+-----------+ +-----------+
| BP app | | BP app |
+---------v-| +->>>>>>>>>>v-+ +->>>>>>>>>>v-+ +-^---------+
| BP v | | ^ BP v | | ^ BP v | | ^ BP |
+---------v-+ +-^---------v-+ +-^---------v-+ +-^---------+
| T1 v | + ^ T1/T2 v | + ^ T2/T3 v | | ^ T3 |
+---------v-+ +-^---------v-+ +-^---------v + +-^---------+
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| N1 v | | ^ N1/N2 v | | ^ N2/N3 v | | ^ N3 |
+---------v-+ +-^---------v + +-^---------v-+ +-^---------+
| >>>>>>>>^ >>>>>>>>>>^ >>>>>>>>^ |
+-----------+ +-------------+ +-------------+ +-----------+
| | | |
|<---- A network ---->| |<---- A network ---->|
| | | |
Figure 1: The Bundle Protocol in the Protocol Stack Model
This document describes the format of the protocol data units
(called "bundles") passed between entities participating in BP
communications.
The entities are referred to as "bundle nodes". This document does
not address:
. Operations in the convergence layer adapters that bundle nodes
use to transport data through specific types of internets.
(However, the document does discuss the services that must be
provided by each adapter at the convergence layer.)
. The bundle route computation algorithm.
. Mechanisms for populating the routing or forwarding information
bases of bundle nodes.
. The mechanisms for securing bundles en route.
. The mechanisms for managing bundle nodes.
Note that implementations of the specification presented in this
document will not be interoperable with implementations of RFC 5050.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Service Description
3.1. Definitions
Bundle - A bundle is a protocol data unit of BP, so named because
negotiation of the parameters of a data exchange may be impractical
in a delay-tolerant network: it is often better practice to "bundle"
with a unit of application data all metadata that might be needed in
order to make the data immediately usable when delivered to the
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application. Each bundle comprises a sequence of two or more
"blocks" of protocol data, which serve various purposes.
Block - A bundle protocol block is one of the protocol data
structures that together constitute a well-formed bundle.
Application Data Unit (ADU) - An application data unit is the unit
of data whose conveyance to the bundle's destination is the purpose
for the transmission of some bundle that is not a fragment (as
defined below).
Bundle payload - A bundle payload (or simply "payload") is the
content of the bundle's payload block. The terms "bundle content",
"bundle payload", and "payload" are used interchangeably in this
document. For a bundle that is not a fragment (as defined below),
the payload is an application data unit.
Partial payload - A partial payload is a payload that comprises
either the first N bytes or the last N bytes of some other payload
of length M, such that 0 < N < M. Note that every partial payload
is a payload and therefore can be further subdivided into partial
payloads.
Fragment - A fragment, a.k.a. "fragmentary bundle", is a bundle
whose payload block contains a partial payload.
Bundle node - A bundle node (or, in the context of this document,
simply a "node") is any entity that can send and/or receive bundles.
Each bundle node has three conceptual components, defined below, as
shown in Figure 2: a "bundle protocol agent", a set of zero or more
"convergence layer adapters", and an "application agent". ("CL1
PDUs" are the PDUs of the convergence-layer protocol used in network
1.)
+-----------------------------------------------------------+
|Node |
| |
| +-------------------------------------------------------+ |
| |Application Agent | |
| | | |
| | +--------------------------+ +----------------------+ | |
| | |Administrative element | |Application-specific | | |
| | | | |element | | |
| | | | | | | |
| | +--------------------------+ +----------------------+ | |
| | ^ ^ | |
| | Admin|records Application|data | |
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| | | | | |
| +----------------v--------------------------v-----------+ |
| ^ |
| | ADUs |
| | |
| +-----------------------------v-------------------------+ |
| |Bundle Protocol Agent | |
| | | |
| | | |
| +-------------------------------------------------------+ |
| ^ ^ ^ |
| | Bundles | Bundles Bundles | |
| | | | |
| +------v-----+ +-----v------+ +-----v-----+ |
| |CLA 1 | |CLA 2 | |CLA n | |
| | | | | . . . | | |
| | | | | | | |
+-+------------+-----+------------+-----------+-----------+-+
^ ^ ^
CL1|PDUs CL2|PDUs CLn|PDUs
| | |
+------v-----+ +-----v------+ +-----v-----+
Network 1 Network 2 Network n
Figure 2: Components of a Bundle Node
Bundle protocol agent - The bundle protocol agent (BPA) of a node is
the node component that offers the BP services and executes the
procedures of the bundle protocol.
Convergence layer adapter - A convergence layer adapter (CLA) is a
node component that sends and receives bundles on behalf of the BPA,
utilizing the services of some 'native' protocol stack that is
supported in one of the networks within which the node is
functionally located.
Application agent - The application agent (AA) of a node is the node
component that utilizes the BP services to effect communication for
some user purpose. The application agent in turn has two elements,
an administrative element and an application-specific element.
Application-specific element - The application-specific element of
an AA is the node component that constructs, requests transmission
of, accepts delivery of, and processes units of user application
data.
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Administrative element - The administrative element of an AA is the
node component that constructs and requests transmission of
administrative records (defined below), including status reports,
and accepts delivery of and processes any administrative records
that the node receives.
Administrative record - A BP administrative record is an application
data unit that is exchanged between the administrative elements of
nodes' application agents for some BP administrative purpose. The
only administrative record defined in this specification is the
status report, discussed later.
Bundle endpoint - A bundle endpoint (or simply "endpoint") is a set
of zero or more bundle nodes that all identify themselves for BP
purposes by some common identifier, called a "bundle endpoint ID"
(or, in this document, simply "endpoint ID"; endpoint IDs are
described in detail in Section 4.5.5.1 below.
Singleton endpoint - A singleton endpoint is an endpoint that always
contains exactly one member.
Registration - A registration is the state machine characterizing a
given node's membership in a given endpoint. Any single
registration has an associated delivery failure action as defined
below and must at any time be in one of two states: Active or
Passive. Registrations are local; information about a node's
registrations is not expected to be available at other nodes, and
the Bundle Protocol does not include a mechanism for distributing
information about registrations.
Delivery - A bundle is considered to have been delivered at a node
subject to a registration as soon as the application data unit that
is the payload of the bundle, together with any relevant metadata
(an implementation matter), has been presented to the node's
application agent in a manner consistent with the state of that
registration.
Deliverability - A bundle is considered "deliverable" subject to a
registration if and only if (a) the bundle's destination endpoint is
the endpoint with which the registration is associated, (b) the
bundle has not yet been delivered subject to this registration, and
(c) the bundle has not yet been "abandoned" (as defined below)
subject to this registration.
Abandonment - To abandon a bundle subject to some registration is to
assert that the bundle is not deliverable subject to that
registration.
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Delivery failure action - The delivery failure action of a
registration is the action that is to be taken when a bundle that is
"deliverable" subject to that registration is received at a time
when the registration is in the Passive state.
Destination - The destination of a bundle is the endpoint comprising
the node(s) at which the bundle is to be delivered (as defined
above).
Transmission - A transmission is an attempt by a node's BPA to cause
copies of a bundle to be delivered to one or more of the nodes that
are members of some endpoint (the bundle's destination) in response
to a transmission request issued by the node's application agent.
Forwarding - To forward a bundle to a node is to invoke the services
of one or more CLAs in a sustained effort to cause a copy of the
bundle to be received by that node.
Discarding - To discard a bundle is to cease all operations on the
bundle and functionally erase all references to it. The specific
procedures by which this is accomplished are an implementation
matter.
Retention constraint - A retention constraint is an element of the
state of a bundle that prevents the bundle from being discarded.
That is, a bundle cannot be discarded while it has any retention
constraints.
Deletion - To delete a bundle is to remove unconditionally all of
the bundle's retention constraints, enabling the bundle to be
discarded.
3.2. Discussion of BP concepts
Multiple instances of the same bundle (the same unit of DTN protocol
data) might exist concurrently in different parts of a network --
possibly differing in some blocks -- in the memory local to one or
more bundle nodes and/or in transit between nodes. In the context of
the operation of a bundle node, a bundle is an instance (copy), in
that node's local memory, of some bundle that is in the network.
The payload for a bundle forwarded in response to a bundle
transmission request is the application data unit whose location is
provided as a parameter to that request. The payload for a bundle
forwarded in response to reception of a bundle is the payload of the
received bundle.
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In the most familiar case, a bundle node is instantiated as a single
process running on a general-purpose computer, but in general the
definition is meant to be broader: a bundle node might alternatively
be a thread, an object in an object-oriented operating system, a
special-purpose hardware device, etc.
The manner in which the functions of the BPA are performed is wholly
an implementation matter. For example, BPA functionality might be
coded into each node individually; it might be implemented as a
shared library that is used in common by any number of bundle nodes
on a single computer; it might be implemented as a daemon whose
services are invoked via inter-process or network communication by
any number of bundle nodes on one or more computers; it might be
implemented in hardware.
Every CLA implements its own thin layer of protocol, interposed
between BP and the (usually "top") protocol(s) of the underlying
native protocol stack; this "CL protocol" may only serve to
multiplex and de-multiplex bundles to and from the underlying native
protocol, or it may offer additional CL-specific functionality. The
manner in which a CLA sends and receives bundles, as well as the
definitions of CLAs and CL protocols, are beyond the scope of this
specification.
Note that the administrative element of a node's application agent
may itself, in some cases, function as a convergence-layer adapter.
That is, outgoing bundles may be "tunneled" through encapsulating
bundles:
. An outgoing bundle constitutes a byte array. This byte array
may, like any other, be presented to the bundle protocol agent
as an application data unit that is to be transmitted to some
endpoint.
. The original bundle thus forms the payload of an encapsulating
bundle that is forwarded using some other convergence-layer
protocol(s).
. When the encapsulating bundle is received, its payload is
delivered to the peer application agent administrative element,
which then instructs the bundle protocol agent to dispatch that
original bundle in the usual way.
The purposes for which this technique may be useful (such as cross-
domain security) are beyond the scope of this specification.
The only interface between the BPA and the application-specific
element of the AA is the BP service interface. But between the BPA
and the administrative element of the AA there is a (conceptual)
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private control interface in addition to the BP service interface.
This private control interface enables the BPA and the
administrative element of the AA to direct each other to take action
under specific circumstances.
In the case of a node that serves simply as a BP "router", the AA
may have no application-specific element at all. The application-
specific elements of other nodes' AAs may perform arbitrarily
complex application functions, perhaps even offering multiplexed DTN
communication services to a number of other applications. As with
the BPA, the manner in which the AA performs its functions is wholly
an implementation matter.
Singletons are the most familiar sort of endpoint, but in general
the endpoint notion is meant to be broader. For example, the nodes
in a sensor network might constitute a set of bundle nodes that are
all registered in a single common endpoint and will all receive any
data delivered at that endpoint. *Note* too that any given bundle
node might be registered in multiple bundle endpoints and receive
all data delivered at each of those endpoints.
Recall that every node, by definition, includes an application agent
which in turn includes an administrative element, which exchanges
administrative records with the administrative elements of other
nodes. As such, every node is permanently, structurally registered
in the singleton endpoint at which administrative records received
from other nodes are delivered. Registration in no other endpoint
can ever be assumed to be permanent. This endpoint, termed the
node's "administrative endpoint", is therefore uniquely and
permanently associated with the node, and for this reason the ID of
a node's administrative endpoint additionally serves as the "node
ID" (see 4.1.5.2 below) of the node.
The destination of every bundle is an endpoint, which may or may not
be singleton. The source of every bundle is a node, identified by
node ID. Note, though, that the source node ID asserted in a given
bundle may be the null endpoint ID (as described later) rather than
the ID of the source node; bundles for which the asserted source
node ID is the null endpoint ID are termed "anonymous" bundles.
Any number of transmissions may be concurrently undertaken by the
bundle protocol agent of a given node.
When the bundle protocol agent of a node determines that a bundle
must be forwarded to a node (either to a node that is a member of
the bundle's destination endpoint or to some intermediate forwarding
node) in the course of completing the successful transmission of
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that bundle, the bundle protocol agent invokes the services of one
or more CLAs in a sustained effort to cause a copy of the bundle to
be received by that node.
Upon reception, the processing of a bundle that has been received by
a given node depends on whether or not the receiving node is
registered in the bundle's destination endpoint. If it is, and if
the payload of the bundle is non-fragmentary (possibly as a result
of successful payload reassembly from fragmentary payloads,
including the original payload of the newly received bundle), then
the bundle is normally delivered to the node's application agent
subject to the registration characterizing the node's membership in
the destination endpoint.
The bundle protocol does not natively ensure delivery of a bundle to
its destination. Data loss along the path to the destination node
can be minimized by utilizing reliable convergence-layer protocols
between neighbors on all segments of the end-to-end path, but for
end-to-end bundle delivery assurance it will be necessary to develop
extensions to the bundle protocol and/or application-layer
mechanisms.
The bundle protocol is designed for extensibility. Bundle protocol
extensions, documented elsewhere, may extend this specification by:
. defining additional blocks;
. defining additional administrative records;
. defining additional bundle processing flags;
. defining additional block processing flags;
. defining additional types of bundle status reports;
. defining additional bundle status report reason codes;
. defining additional mandates and constraints on processing
that conformant bundle protocol agents must perform at
specified points in the inbound and outbound bundle processing
cycles.
3.3. Services Offered by Bundle Protocol Agents
The BPA of each node is expected to provide the following services
to the node's application agent:
. commencing a registration (registering the node in an
endpoint);
. terminating a registration;
. switching a registration between Active and Passive states;
. transmitting a bundle to an identified bundle endpoint;
. canceling a transmission;
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. polling a registration that is in the Passive state;
. delivering a received bundle.
Note that the details of registration functionality are an
implementation matter and are beyond the scope of this
specification.
4. Bundle Format
4.1. Bundle Structure
The format of bundles SHALL conform to the Concise Binary Object
Representation (CBOR [RFC8949]).
Cryptographic verification of a block is possible only if the
sequence of octets on which the verifying node computes its hash -
the canonicalized representation of the block - is identical to the
sequence of octets on which the hash declared for that block was
computed. To ensure that blocks are always in canonical
representation when they are transmitted and received, the CBOR
representations of the values of all fields in all blocks must
conform to the rules for Canonical CBOR as specified in [RFC8949].
Each bundle SHALL be a concatenated sequence of at least two blocks,
represented as a CBOR indefinite-length array. The first block in
the sequence (the first item of the array) MUST be a primary bundle
block in CBOR representation as described below; the bundle MUST
have exactly one primary bundle block. The primary block MUST be
followed by one or more canonical bundle blocks (additional array
items) in CBOR representation as described in 4.3.2 below. Every
block following the primary block SHALL be the CBOR representation
of a canonical block. The last such block MUST be a payload block;
the bundle MUST have exactly one payload block. The payload block
SHALL be followed by a CBOR "break" stop code, terminating the
array.
(Note that, while CBOR permits considerable flexibility in the
encoding of bundles, this flexibility must not be interpreted as
inviting increased complexity in protocol data unit structure.)
Associated with each block of a bundle is a block number. The block
number uniquely identifies the block within the bundle, enabling
blocks (notably bundle security protocol blocks) to reference other
blocks in the same bundle without ambiguity. The block number of
the primary block is implicitly zero; the block numbers of all other
blocks are explicitly stated in block headers as noted below. Block
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numbering is unrelated to the order in which blocks are sequenced in
the bundle. The block number of the payload block is always 1.
An implementation of the Bundle Protocol MAY discard any sequence of
bytes that does not conform to the Bundle Protocol specification.
An implementation of the Bundle Protocol MAY accept a sequence of
bytes that does not conform to the Bundle Protocol specification
(e.g., one that represents data elements in fixed-length arrays
rather than indefinite-length arrays) and transform it into
conformant BP structure before processing it. Procedures for
accomplishing such a transformation are beyond the scope of this
specification.
4.2. BP Fundamental Data Structures
4.2.1. CRC Type
CRC type is an unsigned integer type code for which the following
values (and no others) are valid:
. 0 indicates "no CRC is present."
. 1 indicates "a standard X-25 CRC-16 is present." [CRC16]
. 2 indicates "a standard CRC32C (Castagnoli) CRC-32 is present."
[RFC4960]
CRC type SHALL be represented as a CBOR unsigned integer.
For examples of CRC32C CRCs, see Appendix A.4 of [RFC7143].
Note that more robust protection of BP data integrity, as needed,
may be provided by means of Block Integrity Blocks as defined in the
Bundle Security Protocol [BPSEC]).
4.2.2. CRC
CRC SHALL be omitted from a block if and only if the block's CRC
type code is zero.
When not omitted, the CRC SHALL be represented as a CBOR byte string
of two bytes (that is, CBOR additional information 2, if CRC type is
1) or of four bytes (that is, CBOR additional information 4, if CRC
type is 2); in each case the sequence of bytes SHALL constitute an
unsigned integer value (of 16 or 32 bits, respectively) in network
byte order.
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4.2.3. Bundle Processing Control Flags
Bundle processing control flags assert properties of the bundle as a
whole rather than of any particular block of the bundle. They are
conveyed in the primary block of the bundle.
The following properties are asserted by the bundle processing
control flags:
. The bundle is a fragment. (Boolean)
. The bundle's payload is an administrative record. (Boolean)
. The bundle must not be fragmented. (Boolean)
. Acknowledgment by the user application is requested. (Boolean)
. Status time is requested in all status reports. (Boolean)
. Flags requesting types of status reports (all Boolean):
o Request reporting of bundle reception.
o Request reporting of bundle forwarding.
o Request reporting of bundle delivery.
o Request reporting of bundle deletion.
If the bundle processing control flags indicate that the bundle's
application data unit is an administrative record, then all status
report request flag values MUST be zero.
If the bundle's source node is omitted (i.e., the source node ID is
the ID of the null endpoint, which has no members as discussed
below; this option enables anonymous bundle transmission), then the
bundle is not uniquely identifiable and all bundle protocol features
that rely on bundle identity must therefore be disabled: the "Bundle
must not be fragmented" flag value MUST be 1 and all status report
request flag values MUST be zero.
Bundle processing control flags that are unrecognized MUST be
ignored, as future definitions of additional flags might not be
integrated simultaneously into the Bundle Protocol implementations
operating at all nodes.
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The bundle processing control flags SHALL be represented as a CBOR
unsigned integer item, the value of which SHALL be processed as a
bit field indicating the control flag values as follows (note that
bit numbering in this instance is reversed from the usual practice,
beginning with the low-order bit instead of the high-order bit, in
recognition of the potential definition of additional control flag
values in the future):
. Bit 0 (the low-order bit, 0x000001): bundle is a fragment.
. Bit 1 (0x000002): payload is an administrative record.
. Bit 2 (0x000004): bundle must not be fragmented.
. Bit 3 (0x000008): reserved.
. Bit 4 (0x000010): reserved.
. Bit 5 (0x000020): user application acknowledgement is
requested.
. Bit 6 (0x000040): status time is requested in all status
reports.
. Bit 7 (0x000080): reserved.
. Bit 8 (0x000100): reserved.
. Bit 9 (0x000200): reserved.
. Bit 10(0x000400): reserved.
. Bit 11(0x000800): reserved.
. Bit 12(0x001000): reserved.
. Bit 13(0x002000): reserved.
. Bit 14(0x004000): bundle reception status reports are
requested.
. Bit 15(0x008000): reserved.
. Bit 16(0x010000): bundle forwarding status reports are
requested.
. Bit 17(0x020000): bundle delivery status reports are requested.
. Bit 18(0x040000): bundle deletion status reports are requested.
. Bits 19-20 are reserved.
. Bits 21-63 are unassigned.
4.2.4. Block Processing Control Flags
The block processing control flags assert properties of canonical
bundle blocks. They are conveyed in the header of the block to
which they pertain.
Block processing control flags that are unrecognized MUST be
ignored, as future definitions of additional flags might not be
integrated simultaneously into the Bundle Protocol implementations
operating at all nodes.
The block processing control flags SHALL be represented as a CBOR
unsigned integer item, the value of which SHALL be processed as a
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bit field indicating the control flag values as follows (note that
bit numbering in this instance is reversed from the usual practice,
beginning with the low-order bit instead of the high-order bit, for
agreement with the bit numbering of the bundle processing control
flags):
. Bit 0(the low-order bit, 0x01): block must be replicated in
every fragment.
. Bit 1(0x02): transmission of a status report is requested if
block can't be processed.
. Bit 2(0x04): bundle must be deleted if block can't be
processed.
. Bit 3(0x08): reserved.
. Bit 4(0x10): block must be removed from bundle if it can't be
processed.
. Bit 5(0x20): reserved.
. Bit 6 (0x40): reserved.
. Bits 7-63 are unassigned.
For each bundle whose bundle processing control flags indicate that
the bundle's application data unit is an administrative record, or
whose source node ID is the null endpoint ID as defined below, the
value of the "Transmit status report if block can't be processed"
flag in every canonical block of the bundle MUST be zero.
4.2.5. Identifiers
4.2.5.1. Endpoint ID
The destinations of bundles are bundle endpoints, identified by text
strings termed "endpoint IDs" (see Section 3.1). Each endpoint ID
(EID) is a Uniform Resource Identifier (URI; [URI]). As such, each
endpoint ID can be characterized as having this general structure:
< scheme name > : < scheme-specific part, or "SSP" >
The scheme identified by the < scheme name > in an endpoint ID is a
set of syntactic and semantic rules that fully explain how to parse
and interpret the SSP. Each scheme that may be used to form a BP
endpoint ID must be added to the registry of URI scheme code numbers
for Bundle Protocol maintained by IANA as described in Section 10;
association of a unique URI scheme code number with each scheme name
in this registry helps to enable compact representation of endpoint
IDs in bundle blocks. Note that the set of allowable schemes is
effectively unlimited. Any scheme conforming to [URIREG] may be
added to the URI scheme code number registry and thereupon used in a
bundle protocol endpoint ID.
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Each entry in the URI scheme code number registry MUST contain a
reference to a scheme code number definition document, which defines
the manner in which the scheme-specific part of any URI formed in
that scheme is parsed and interpreted and MUST be encoded, in CBOR
representation, for transmission as a BP endpoint ID. The scheme
code number definition document may also contain information as to
(a) which convergence-layer protocol(s) may be used to forward a
bundle to a BP destination endpoint identified by such an ID, and
(b) how the ID of the convergence-layer protocol endpoint to use for
that purpose can be inferred from that destination endpoint ID.
Note that, although endpoint IDs are URIs, implementations of the BP
service interface may support expression of endpoint IDs in some
internationalized manner (e.g., Internationalized Resource
Identifiers (IRIs); see [RFC3987]).
Each BP endpoint ID (EID) SHALL be represented as a CBOR array
comprising two items.
The first item of the array SHALL be the code number identifying the
endpoint ID's URI scheme, as defined in the registry of URI scheme
code numbers for Bundle Protocol. Each URI scheme code number SHALL
be represented as a CBOR unsigned integer.
The second item of the array SHALL be the applicable CBOR
representation of the scheme-specific part (SSP) of the EID, defined
as noted in the references(s) for the URI scheme code number
registry entry for the EID's URI scheme.
4.2.5.1.1. The "dtn" URI scheme
The "dtn" scheme supports the identification of BP endpoints by
arbitrarily expressive character strings. It is specified as
follows:
Scheme syntax: This specification uses the Augmented Backus-Naur
Form (ABNF) notation of [RFC5234].
dtn-uri = "dtn:" ("none" / dtn-hier-part)
dtn-hier-part = "//" node-name name-delim demux ; a path-rootless
node-name = 1*(ALPHA/DIGIT/"-"/"."/"_") reg-name
name-delim = "/"
demux = *VCHAR
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Scheme semantics: URIs of the dtn scheme are used as endpoint
identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol
(BP) as described in the present document.
The endpoint ID "dtn:none" identifies the "null endpoint", the
endpoint that by definition never has any members.
All BP endpoints identified by all other dtn-scheme endpoint IDs for
which the first character of demux is a character other than '~'
(tilde) are singleton endpoints. All BP endpoints identified by dtn-
scheme endpoint IDs for which the first character *is* '~' (tilde)
are *not* singleton endpoints.
A dtn-scheme endpoint ID for which the demux is of length zero MAY
identify the administrative endpoint for the node identified by
node-name, and as such may serve as a node ID. No dtn-scheme
endpoint ID for which the demux is of non-zero length may do so.
Note that these syntactic rules impose constraints on dtn-scheme
endpoint IDs that were not imposed by the original specification of
the dtn scheme as provided in [RFC5050]. It is believed that the
dtn-scheme endpoint IDs employed by BP applications conforming to
[RFC5050] are in most cases unlikely to be in violation of these
rules, but the developers of such applications are advised of the
potential for compromised interoperation.
Encoding considerations: For transmission as a BP endpoint ID, the
scheme-specific part of a URI of the dtn scheme SHALL be represented
as a CBOR text string unless the EID's SSP is "none", in which case
the SSP SHALL be represented as a CBOR unsigned integer with the
value zero. For all other purposes, URIs of the dtn scheme are
encoded exclusively in US-ASCII characters.
Interoperability considerations: none.
Security considerations:
. Reliability and consistency: none of the BP endpoints
identified by the URIs of the dtn scheme are guaranteed to be
reachable at any time, and the identity of the processing
entities operating on those endpoints is never guaranteed by
the Bundle Protocol itself. Bundle authentication as defined by
the Bundle Security Protocol is required for this purpose.
. Malicious construction: malicious construction of a conformant
dtn-scheme URI is limited to the malicious selection of node
names and the malicious selection of demux strings. That is, a
maliciously constructed dtn-scheme URI could be used to direct
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a bundle to an endpoint that might be damaged by the arrival of
that bundle or, alternatively, to declare a false source for a
bundle and thereby cause incorrect processing at a node that
receives the bundle. In both cases (and indeed in all bundle
processing), the node that receives a bundle should verify its
authenticity and validity before operating on it in any way.
. Back-end transcoding: the limited expressiveness of URIs of the
dtn scheme effectively eliminates the possibility of threat due
to errors in back-end transcoding.
. Rare IP address formats: not relevant, as IP addresses do not
appear anywhere in conformant dtn-scheme URIs.
. Sensitive information: because dtn-scheme URIs are used only to
represent the identities of Bundle Protocol endpoints, the risk
of disclosure of sensitive information due to interception of
these URIs is minimal. Examination of dtn-scheme URIs could be
used to support traffic analysis; where traffic analysis is a
plausible danger, bundles should be conveyed by secure
convergence-layer protocols that do not expose endpoint IDs.
. Semantic attacks: the simplicity of dtn-scheme URI syntax
minimizes the possibility of misinterpretation of a URI by a
human user.
4.2.5.1.2. The "ipn" URI scheme
The "ipn" scheme supports the identification of BP endpoints by
pairs of unsigned integers, for compact representation in bundle
blocks. It is specified as follows:
Scheme syntax: This specification uses the Augmented Backus-Naur
Form (ABNF) notation of [RFC5234], including the core ABNF syntax
rule for DIGIT defined by that specification.
ipn-uri = "ipn:" ipn-hier-part
ipn-hier-part = node-nbr nbr-delim service-nbr ; a path-rootless
node-nbr = 1*DIGIT
nbr-delim = "."
service-nbr = 1*DIGIT
Scheme semantics: URIs of the ipn scheme are used as endpoint
identifiers in the Delay-Tolerant Networking (DTN) Bundle Protocol
(BP) as described in the present document.
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All BP endpoints identified by ipn-scheme endpoint IDs are singleton
endpoints.
An ipn-scheme endpoint ID for which service-nbr is zero MAY identify
the administrative endpoint for the node identified by node-nbr, and
as such may serve as a node ID. No ipn-scheme endpoint ID for which
service-nbr is non-zero may do so.
Encoding considerations: For transmission as a BP endpoint ID, the
scheme-specific part of a URI of the ipn scheme the SSP SHALL be
represented as a CBOR array comprising two items. The first item of
this array SHALL be the EID's node number (a number that identifies
the node) represented as a CBOR unsigned integer. The second item
of this array SHALL be the EID's service number (a number that
identifies some application service) represented as a CBOR unsigned
integer. For all other purposes, URIs of the ipn scheme are encoded
exclusively in US-ASCII characters.
Interoperability considerations: none.
Security considerations:
. Reliability and consistency: none of the BP endpoints
identified by the URIs of the ipn scheme are guaranteed to be
reachable at any time, and the identity of the processing
entities operating on those endpoints is never guaranteed by
the Bundle Protocol itself. Bundle authentication as defined by
the Bundle Security Protocol [BPSEC] is required for this
purpose.
. Malicious construction: malicious construction of a conformant
ipn-scheme URI is limited to the malicious selection of node
numbers and the malicious selection of service numbers. That
is, a maliciously constructed ipn-scheme URI could be used to
direct a bundle to an endpoint that might be damaged by the
arrival of that bundle or, alternatively, to declare a false
source for a bundle and thereby cause incorrect processing at a
node that receives the bundle. In both cases (and indeed in
all bundle processing), the node that receives a bundle should
verify its authenticity and validity before operating on it in
any way.
. Back-end transcoding: the limited expressiveness of URIs of the
ipn scheme effectively eliminates the possibility of threat due
to errors in back-end transcoding.
. Rare IP address formats: not relevant, as IP addresses do not
appear anywhere in conformant ipn-scheme URIs.
. Sensitive information: because ipn-scheme URIs are used only to
represent the identities of Bundle Protocol endpoints, the risk
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of disclosure of sensitive information due to interception of
these URIs is minimal. Examination of ipn-scheme URIs could be
used to support traffic analysis; where traffic analysis is a
plausible danger, bundles should be conveyed by secure
convergence-layer protocols that do not expose endpoint IDs.
. Semantic attacks: the simplicity of ipn-scheme URI syntax
minimizes the possibility of misinterpretation of a URI by a
human user.
4.2.5.2. Node ID
For many purposes of the Bundle Protocol it is important to identify
the node that is operative in some context.
As discussed in 3.1 above, nodes are distinct from endpoints;
specifically, an endpoint is a set of zero or more nodes. But
rather than define a separate namespace for node identifiers, we
instead use endpoint identifiers to identify nodes as discussed in
3.2 above. Formally:
. Every node is, by definition, permanently registered in the
singleton endpoint at which administrative records are
delivered to its application agent's administrative element,
termed the node's "administrative endpoint".
. As such, the EID of a node's administrative endpoint SHALL
uniquely identify that node.
. A "node ID" is an EID that identifies the administrative
endpoint of a node.
4.2.6. DTN Time
A DTN time is an unsigned integer indicating the number of
milliseconds that have elapsed since the DTN Epoch, 2000-01-01
00:00:00 +0000 (UTC). DTN time is not affected by leap seconds.
Each DTN time SHALL be represented as a CBOR unsigned integer item.
Implementers need to be aware that DTN time values conveyed in CBOR
representation in bundles will nearly always exceed (2**32 - 1); the
manner in which a DTN time value is represented in memory is an
implementation matter. The DTN time value zero indicates that the
time is unknown.
4.2.7. Creation Timestamp
Each bundle's creation timestamp SHALL be represented as a CBOR
array comprising two items.
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The first item of the array, termed "bundle creation time", SHALL be
the DTN time at which the transmission request was received that
resulted in the creation of the bundle, represented as a CBOR
unsigned integer.
The second item of the array, termed the creation timestamp's
"sequence number", SHALL be the latest value (as of the time at
which the transmission request was received) of a monotonically
increasing positive integer counter managed by the source node's
bundle protocol agent, represented as a CBOR unsigned integer. The
sequence counter MAY be reset to zero whenever the current time
advances by one millisecond.
For nodes that lack accurate clocks, it is recommended that bundle
creation time be set to zero and that the counter used as the source
of the bundle sequence count never be reset to zero.
Note that, in general, the creation of two distinct bundles with the
same source node ID and bundle creation timestamp may result in
unexpected network behavior and/or suboptimal performance. The
combination of source node ID and bundle creation timestamp serves
to identify a single transmission request, enabling it to be
acknowledged by the receiving application (provided the source node
ID is not the null endpoint ID).
4.2.8. Block-type-specific Data
Block-type-specific data in each block (other than the primary
block) SHALL be the applicable CBOR representation of the content of
the block. Details of this representation are included in the
specification defining the block type.
4.3. Block Structures
This section describes the primary block in detail and non-primary
blocks in general. Rules for processing these blocks appear in
Section 5 of this document.
Note that supplementary DTN protocol specifications (including, but
not restricted to, the Bundle Security Protocol [BPSEC]) may require
that BP implementations conforming to those protocols construct and
process additional blocks.
4.3.1. Primary Bundle Block
The primary bundle block contains the basic information needed to
forward bundles to their destinations.
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Each primary block SHALL be represented as a CBOR array; the number
of elements in the array SHALL be 8 (if the bundle is not a fragment
and the block has no CRC), 9 (if the block has a CRC and the bundle
is not a fragment), 10 (if the bundle is a fragment and the block
has no CRC), or 11 (if the bundle is a fragment and the block has a
CRC).
The primary block of each bundle SHALL be immutable. The CBOR-
encoded values of all fields in the primary block MUST remain
unchanged from the time the block is created to the time it is
delivered.
The fields of the primary bundle block SHALL be as follows, listed
in the order in which they MUST appear:
Version: An unsigned integer value indicating the version of the
bundle protocol that constructed this block. The present document
describes version 7 of the bundle protocol. Version number SHALL be
represented as a CBOR unsigned integer item.
Bundle Processing Control Flags: The Bundle Processing Control Flags
are discussed in Section 4.2.3. above.
CRC Type: CRC Type codes are discussed in Section 4.2.1. above. The
CRC Type code for the primary block MAY be zero if the bundle
contains a BPsec [BPSEC] Block Integrity Block whose target is the
primary block; otherwise the CRC Type code for the primary block
MUST be non-zero.
Destination EID: The Destination EID field identifies the bundle
endpoint that is the bundle's destination, i.e., the endpoint that
contains the node(s) at which the bundle is to be delivered.
Source node ID: The Source node ID field identifies the bundle node
at which the bundle was initially transmitted, except that Source
node ID may be the null endpoint ID in the event that the bundle's
source chooses to remain anonymous.
Report-to EID: The Report-to EID field identifies the bundle
endpoint to which status reports pertaining to the forwarding and
delivery of this bundle are to be transmitted.
Creation Timestamp: The creation timestamp comprises two unsigned
integers that, together with the source node ID and (if the bundle
is a fragment) the fragment offset and payload length, serve to
identify the bundle. See 4.2.7 above for the definition of this
field.
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Lifetime: The lifetime field is an unsigned integer that indicates
the time at which the bundle's payload will no longer be useful,
encoded as a number of milliseconds past the creation time. (For
high-rate deployments with very brief disruptions, fine-grained
expression of bundle lifetime may be useful.) When a bundle's age
exceeds its lifetime, bundle nodes need no longer retain or forward
the bundle; the bundle SHOULD be deleted from the network.
If the asserted lifetime for a received bundle is so lengthy that
retention of the bundle until its expiration time might degrade
operation of the node at which the bundle is received, or if the
bundle protocol agent of that node determines that the bundle must
be deleted in order to prevent network performance degradation
(e.g., the bundle appears to be part of a denial-of-service attack),
then that bundle protocol agent MAY impose a temporary overriding
lifetime of shorter duration; such overriding lifetime SHALL NOT
replace the lifetime asserted in the bundle but SHALL serve as the
bundle's effective lifetime while the bundle resides at that node.
Procedures for imposing lifetime overrides are beyond the scope of
this specification.
For bundles originating at nodes that lack accurate clocks, it is
recommended that bundle age be obtained from the Bundle Age
extension block (see 4.4.2 below) rather than from the difference
between current time and bundle creation time. Bundle lifetime
SHALL be represented as a CBOR unsigned integer item.
Fragment offset: If and only if the Bundle Processing Control Flags
of this Primary block indicate that the bundle is a fragment,
fragment offset SHALL be present in the primary block. Fragment
offset SHALL be represented as a CBOR unsigned integer indicating
the offset from the start of the original application data unit at
which the bytes comprising the payload of this bundle were located.
Total Application Data Unit Length: If and only if the Bundle
Processing Control Flags of this Primary block indicate that the
bundle is a fragment, total application data unit length SHALL be
present in the primary block. Total application data unit length
SHALL be represented as a CBOR unsigned integer indicating the total
length of the original application data unit of which this bundle's
payload is a part.
CRC: A CRC SHALL be present in the primary block unless the bundle
includes a BPsec [BPSEC] Block Integrity Block whose target is the
primary block, in which case a CRC MAY be present in the primary
block. The length and nature of the CRC SHALL be as indicated by
the CRC type. The CRC SHALL be computed over the concatenation of
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all bytes (including CBOR "break" characters) of the primary block
including the CRC field itself, which for this purpose SHALL be
temporarily populated with all bytes set to zero.
4.3.2. Canonical Bundle Block Format
Every block other than the primary block (all such blocks are termed
"canonical" blocks) SHALL be represented as a CBOR array; the number
of elements in the array SHALL be 5 (if CRC type is zero) or 6
(otherwise).
The fields of every canonical block SHALL be as follows, listed in
the order in which they MUST appear:
. Block type code, an unsigned integer. Bundle block type code 1
indicates that the block is a bundle payload block. Block type
codes 2 through 9 are explicitly reserved as noted later in
this specification. Block type codes 192 through 255 are not
reserved and are available for private and/or experimental use.
All other block type code values are reserved for future use.
. Block number, an unsigned integer as discussed in 4.1 above.
Block number SHALL be represented as a CBOR unsigned integer.
. Block processing control flags as discussed in Section 4.2.4
above.
. CRC type as discussed in Section 4.2.1 above.
. Block-type-specific data represented as a single definite-
length CBOR byte string, i.e., a CBOR byte string that is not
of indefinite length. For each type of block, the block-type-
specific data byte string is the serialization, in a block-
type-specific manner, of the data conveyed by that type of
block; definitions of blocks are required to define the manner
in which block-type-specific data are serialized within the
block-type-specific data field. For the Payload Block in
particular (block type 1), the block-type-specific data field,
termed the "payload", SHALL be an application data unit, or
some contiguous extent thereof, represented as a definite-
length CBOR byte string.
. If and only if the value of the CRC type field of this block is
non-zero, a CRC. If present, the length and nature of the CRC
SHALL be as indicated by the CRC type and the CRC SHALL be
computed over the concatenation of all bytes of the block
(including CBOR "break" characters) including the CRC field
itself, which for this purpose SHALL be temporarily populated
with all bytes set to zero.
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4.4. Extension Blocks
"Extension blocks" are all blocks other than the primary and payload
blocks. Three types of extension blocks are defined below. All
implementations of the Bundle Protocol specification (the present
document) MUST include procedures for recognizing, parsing, and
acting on, but not necessarily producing, these types of extension
blocks.
The specifications for additional types of extension blocks must
indicate whether or not BP implementations conforming to those
specifications must recognize, parse, act on, and/or produce blocks
of those types. As not all nodes will necessarily instantiate BP
implementations that conform to those additional specifications, it
is possible for a node to receive a bundle that includes extension
blocks that the node cannot process. The values of the block
processing control flags indicate the action to be taken by the
bundle protocol agent when this is the case.
No mandated procedure in this specification is unconditionally
dependent on the absence or presence of any extension block.
Therefore any bundle protocol agent MAY insert or remove any
extension block in any bundle, subject to all mandates in the Bundle
Protocol specification and all extension block specifications to
which the node's BP implementation conforms. Note that removal of
an extension block will probably disable one or more elements of
bundle processing that were intended by the BPA that inserted that
block. In particular, note that removal of an extension block that
is one of the targets of a BPsec security block may render the
bundle unverifiable.
The following extension blocks are defined in the current document.
4.4.1. Previous Node
The Previous Node block, block type 6, identifies the node that
forwarded this bundle to the local node (i.e., to the node at which
the bundle currently resides); its block-type-specific data is the
node ID of that forwarder node which SHALL take the form of a node
ID represented as described in Section 4.2.5.2. above. If the local
node is the source of the bundle, then the bundle MUST NOT contain
any Previous Node block. Otherwise the bundle SHOULD contain one
(1) occurrence of this type of block and MUST NOT contain more than
one.
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4.4.2. Bundle Age
The Bundle Age block, block type 7, contains the number of
milliseconds that have elapsed between the time the bundle was
created and time at which it was most recently forwarded. It is
intended for use by nodes lacking access to an accurate clock, to
aid in determining the time at which a bundle's lifetime expires.
The block-type-specific data of this block is an unsigned integer
containing the age of the bundle in milliseconds, which SHALL be
represented as a CBOR unsigned integer item. (The age of the bundle
is the sum of all known intervals of the bundle's residence at
forwarding nodes, up to the time at which the bundle was most
recently forwarded, plus the summation of signal propagation time
over all episodes of transmission between forwarding nodes.
Determination of these values is an implementation matter.) If the
bundle's creation time is zero, then the bundle MUST contain exactly
one (1) occurrence of this type of block; otherwise, the bundle MAY
contain at most one (1) occurrence of this type of block. A bundle
MUST NOT contain multiple occurrences of the bundle age block, as
this could result in processing anomalies.
4.4.3. Hop Count
The Hop Count block, block type 10, contains two unsigned integers,
hop limit and hop count. A "hop" is here defined as an occasion on
which a bundle was forwarded from one node to another node. Hop
limit MUST be in the range 1 through 255. The hop limit value SHOULD
NOT be changed at any time after creation of the Hop Count block;
the hop count value SHOULD initially be zero and SHOULD be increased
by 1 on each hop.
The hop count block is mainly intended as a safety mechanism, a
means of identifying bundles for removal from the network that can
never be delivered due to a persistent forwarding error. Hop count
is particularly valuable as a defense against routing anomalies that
might cause a bundle to be forwarded in a cyclical "ping-pong"
fashion between two nodes. When a bundle's hop count exceeds its
hop limit, the bundle SHOULD be deleted for the reason "hop limit
exceeded", following the bundle deletion procedure defined in
Section 5.10.
Procedures for determining the appropriate hop limit for a bundle
are beyond the scope of this specification.
The block-type-specific data in a hop count block SHALL be
represented as a CBOR array comprising two items. The first item of
this array SHALL be the bundle's hop limit, represented as a CBOR
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unsigned integer. The second item of this array SHALL be the
bundle's hop count, represented as a CBOR unsigned integer. A bundle
MAY contain one occurrence of this type of block but MUST NOT
contain more than one.
5. Bundle Processing
The bundle processing procedures mandated in this section and in
Section 6 govern the operation of the Bundle Protocol Agent and the
Application Agent administrative element of each bundle node. They
are neither exhaustive nor exclusive. Supplementary DTN protocol
specifications (including, but not restricted to, the Bundle
Security Protocol [BPSEC]) may augment, override, or supersede the
mandates of this document.
5.1. Generation of Administrative Records
All transmission of bundles is in response to bundle transmission
requests presented by nodes' application agents. When required to
"generate" an administrative record (such as a bundle status
report), the bundle protocol agent itself is responsible for causing
a new bundle to be transmitted, conveying that record. In concept,
the bundle protocol agent discharges this responsibility by
directing the administrative element of the node's application agent
to construct the record and request its transmission as detailed in
Section 6 below. In practice, the manner in which administrative
record generation is accomplished is an implementation matter,
provided the constraints noted in Section 6 are observed.
Status reports are relatively small bundles. Moreover, even when
the generation of status reports is enabled the decision on whether
or not to generate a requested status report is left to the
discretion of the bundle protocol agent. Nonetheless, note that
requesting status reports for any single bundle might easily result
in the generation of (1 + (2 *(N-1))) status report bundles, where N
is the number of nodes on the path from the bundle's source to its
destination, inclusive. That is, the requesting of status reports
for large numbers of bundles could result in an unacceptable
increase in the bundle traffic in the network. For this reason, the
generation of status reports MUST be disabled by default and enabled
only when the risk of excessive network traffic is deemed
acceptable. Mechanisms that could assist in assessing and
mitigating this risk, such as pre-placed agreements authorizing the
generation of status reports under specified circumstances, are
beyond the scope of this specification.
Notes on administrative record terminology:
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. A "bundle reception status report" is a bundle status report
with the "reporting node received bundle" flag set to 1.
. A "bundle forwarding status report" is a bundle status report
with the "reporting node forwarded the bundle" flag set to 1.
. A "bundle delivery status report" is a bundle status report
with the "reporting node delivered the bundle" flag set to 1.
. A "bundle deletion status report" is a bundle status report
with the "reporting node deleted the bundle" flag set to 1.
5.2. Bundle Transmission
The steps in processing a bundle transmission request are:
Step 1: Transmission of the bundle is initiated. An outbound bundle
MUST be created per the parameters of the bundle transmission
request, with the retention constraint "Dispatch pending". The
source node ID of the bundle MUST be either the null endpoint ID,
indicating that the source of the bundle is anonymous, or else the
EID of a singleton endpoint whose only member is the node of which
the BPA is a component.
Step 2: Processing proceeds from Step 1 of Section 5.4.
5.3. Bundle Dispatching
(Note that this procedure is initiated only following completion of
Step 4 of Section 5.6.)
The steps in dispatching a bundle are:
Step 1: If the bundle's destination endpoint is an endpoint of which
the node is a member, the bundle delivery procedure defined in
Section 5.7 MUST be followed and for the purposes of all subsequent
processing of this bundle at this node the node's membership in the
bundle's destination endpoint SHALL be disavowed; specifically, even
though the node is a member of the bundle's destination endpoint,
the node SHALL NOT undertake to forward the bundle to itself in the
course of performing the procedure described in Section 5.4.
Step 2: Processing proceeds from Step 1 of Section 5.4.
5.4. Bundle Forwarding
The steps in forwarding a bundle are:
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Step 1: The retention constraint "Forward pending" MUST be added to
the bundle, and the bundle's "Dispatch pending" retention constraint
MUST be removed.
Step 2: The bundle protocol agent MUST determine whether or not
forwarding is contraindicated (that is, rendered inadvisable) for
any of the reasons listed in the IANA registry of Bundle Status
Report Reason Codes (see section 10.5 below), whose initial contents
are listed in Figure 4. In particular:
. The bundle protocol agent MAY choose either to forward the
bundle directly to its destination node(s) (if possible) or to
forward the bundle to some other node(s) for further
forwarding. The manner in which this decision is made may
depend on the scheme name in the destination endpoint ID and/or
on other state but in any case is beyond the scope of this
document; one possible mechanism is described in [SABR]. If the
BPA elects to forward the bundle to some other node(s) for
further forwarding but finds it impossible to select any
node(s) to forward the bundle to, then forwarding is
contraindicated.
. Provided the bundle protocol agent succeeded in selecting the
node(s) to forward the bundle to, the bundle protocol agent
MUST subsequently select the convergence layer adapter(s) whose
services will enable the node to send the bundle to those
nodes. The manner in which specific appropriate convergence
layer adapters are selected is beyond the scope of this
document; the TCP convergence-layer adapter [TCPCL] MUST be
implemented when some or all of the bundles forwarded by the
bundle protocol agent must be forwarded via the Internet but
may not be appropriate for the forwarding of any particular
bundle. If the agent finds it impossible to select any
appropriate convergence layer adapter(s) to use in forwarding
this bundle, then forwarding is contraindicated.
Step 3: If forwarding of the bundle is determined to be
contraindicated for any of the reasons listed in the IANA registry
of Bundle Status Report Reason Codes (see section 10.5 below), then
the Forwarding Contraindicated procedure defined in Section 5.4.1
MUST be followed; the remaining steps of Section 5.4 are skipped at
this time.
Step 4: For each node selected for forwarding, the bundle protocol
agent MUST invoke the services of the selected convergence layer
adapter(s) in order to effect the sending of the bundle to that
node. Determining the time at which the bundle protocol agent
invokes convergence layer adapter services is a BPA implementation
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matter. Determining the time at which each convergence layer
adapter subsequently responds to this service invocation by sending
the bundle is a convergence-layer adapter implementation matter.
Note that:
. If the bundle has a Previous Node block, as defined in 4.4.1
above, then that block MUST be removed from the bundle before
the bundle is forwarded.
. If the bundle protocol agent is configured to attach Previous
Node blocks to forwarded bundles, then a Previous Node block
containing the node ID of the forwarding node MUST be inserted
into the bundle before the bundle is forwarded.
. If the bundle has a bundle age block, as defined in 4.4.2.
above, then at the last possible moment before the CLA
initiates conveyance of the bundle via the CL protocol the
bundle age value MUST be increased by the difference between
the current time and the time at which the bundle was received
(or, if the local node is the source of the bundle, created).
Step 5: When all selected convergence layer adapters have informed
the bundle protocol agent that they have concluded their data
sending procedures with regard to this bundle, processing may depend
on the results of those procedures.
If completion of the data sending procedures by all selected
convergence layer adapters has not resulted in successful forwarding
of the bundle (an implementation-specific determination that is
beyond the scope of this specification), then the bundle protocol
agent MAY choose (in an implementation-specific manner, again beyond
the scope of this specification) to initiate another attempt to
forward the bundle. In that event, processing proceeds from Step 4.
The minimum number of times a given node will initiate another
forwarding attempt for any single bundle in this event (a number
which may be zero) is a node configuration parameter that must be
exposed to other nodes in the network to the extent that this is
required by the operating environment.
If completion of the data sending procedures by all selected
convergence layer adapters HAS resulted in successful forwarding of
the bundle, or if it has not but the bundle protocol agent does not
choose to initiate another attempt to forward the bundle, then:
. If the "request reporting of bundle forwarding" flag in the
bundle's status report request field is set to 1, and status
reporting is enabled, then a bundle forwarding status report
SHOULD be generated, destined for the bundle's report-to
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endpoint ID. The reason code on this bundle forwarding status
report MUST be "no additional information".
. If any applicable bundle protocol extensions mandate generation
of status reports upon conclusion of convergence-layer data
sending procedures, all such status reports SHOULD be generated
with extension-mandated reason codes.
. The bundle's "Forward pending" retention constraint MUST be
removed.
5.4.1. Forwarding Contraindicated
The steps in responding to contraindication of forwarding are:
Step 1: The bundle protocol agent MUST determine whether or not to
declare failure in forwarding the bundle. Note: this decision is
likely to be influenced by the reason for which forwarding is
contraindicated.
Step 2: If forwarding failure is declared, then the Forwarding
Failed procedure defined in Section 5.4.2 MUST be followed.
Otherwise, when - at some future time - the forwarding of this
bundle ceases to be contraindicated, processing proceeds from Step 4
of Section 5.4.
5.4.2. Forwarding Failed
The steps in responding to a declaration of forwarding failure are:
Step 1: The bundle protocol agent MAY forward the bundle back to the
node that sent it, as identified by the Previous Node block, if
present. This forwarding, if performed, SHALL be accomplished by
performing Step 4 and Step 5 of section 5.4 where the sole node
selected for forwarding SHALL be the node that sent the bundle.
Step 2: If the bundle's destination endpoint is an endpoint of which
the node is a member, then the bundle's "Forward pending" retention
constraint MUST be removed. Otherwise, the bundle MUST be deleted:
the bundle deletion procedure defined in Section 5.10 MUST be
followed, citing the reason for which forwarding was determined to
be contraindicated.
5.5. Bundle Expiration
A bundle expires when the bundle's age exceeds its lifetime as
specified in the primary bundle block or as overridden by the bundle
protocol agent. Bundle age MAY be determined by subtracting the
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bundle's creation timestamp time from the current time if (a) that
timestamp time is not zero and (b) the local node's clock is known
to be accurate; otherwise bundle age MUST be obtained from the
Bundle Age extension block. Bundle expiration MAY occur at any
point in the processing of a bundle. When a bundle expires, the
bundle protocol agent MUST delete the bundle for the reason
"lifetime expired" (when the expired lifetime is the lifetime as
specified in the primary block) or "traffic pared" (when the expired
lifetime is a lifetime override as imposed by the bundle protocol
agent): the bundle deletion procedure defined in Section 5.10 MUST
be followed.
5.6. Bundle Reception
The steps in processing a bundle that has been received from another
node are:
Step 1: The retention constraint "Dispatch pending" MUST be added to
the bundle.
Step 2: If the "request reporting of bundle reception" flag in the
bundle's status report request field is set to 1, and status
reporting is enabled, then a bundle reception status report with
reason code "No additional information" SHOULD be generated,
destined for the bundle's report-to endpoint ID.
Step 3: CRCs SHOULD be computed for every block of the bundle that
has an attached CRC. If any block of the bundle is malformed
according to this specification (including syntactically invalid
CBOR), or if any block has an attached CRC and the CRC computed for
this block upon reception differs from that attached CRC, then the
bundle protocol agent MUST delete the bundle for the reason "Block
unintelligible". The bundle deletion procedure defined in Section
5.10 MUST be followed and all remaining steps of the bundle
reception procedure MUST be skipped.
Step 4: For each block in the bundle that is an extension block that
the bundle protocol agent cannot process:
. If the block processing flags in that block indicate that a
status report is requested in this event, and status reporting
is enabled, then a bundle reception status report with reason
code "Block unsupported" SHOULD be generated, destined for the
bundle's report-to endpoint ID.
. If the block processing flags in that block indicate that the
bundle must be deleted in this event, then the bundle protocol
agent MUST delete the bundle for the reason "Block
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unsupported"; the bundle deletion procedure defined in Section
5.10 MUST be followed and all remaining steps of the bundle
reception procedure MUST be skipped.
. If the block processing flags in that block do NOT indicate
that the bundle must be deleted in this event but do indicate
that the block must be discarded, then the bundle protocol
agent MUST remove this block from the bundle.
. If the block processing flags in that block indicate neither
that the bundle must be deleted nor that that the block must be
discarded, then processing continues with the next extension
block that the bundle protocol agent cannot process, if any;
otherwise, processing proceeds from step 5.
Step 5: Processing proceeds from Step 1 of Section 5.3.
5.7. Local Bundle Delivery
The steps in processing a bundle that is destined for an endpoint of
which this node is a member are:
Step 1: If the received bundle is a fragment, the application data
unit reassembly procedure described in Section 5.9 MUST be followed.
If this procedure results in reassembly of the entire original
application data unit, processing of the fragmentary bundle whose
payload has been replaced by the reassembled application data unit
(whether this bundle or a previously received fragment) proceeds
from Step 2; otherwise, the retention constraint "Reassembly
pending" MUST be added to the bundle and all remaining steps of this
procedure MUST be skipped.
Step 2: Delivery depends on the state of the registration whose
endpoint ID matches that of the destination of the bundle:
. An additional implementation-specific delivery deferral
procedure MAY optionally be associated with the registration.
. If the registration is in the Active state, then the bundle
MUST be delivered automatically as soon as it is the next
bundle that is due for delivery according to the BPA's bundle
delivery scheduling policy, an implementation matter.
. If the registration is in the Passive state, or if delivery of
the bundle fails for some implementation-specific reason, then
the registration's delivery failure action MUST be taken.
Delivery failure action MUST be one of the following:
o defer delivery of the bundle subject to this registration
until (a) this bundle is the least recently received of
all bundles currently deliverable subject to this
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registration and (b) either the registration is polled or
else the registration is in the Active state, and also
perform any additional delivery deferral procedure
associated with the registration; or
o abandon delivery of the bundle subject to this registration
(as defined in 3.1. ).
Step 3: As soon as the bundle has been delivered, if the "request
reporting of bundle delivery" flag in the bundle's status report
request field is set to 1 and bundle status reporting is enabled,
then a bundle delivery status report SHOULD be generated, destined
for the bundle's report-to endpoint ID. Note that this status report
only states that the payload has been delivered to the application
agent, not that the application agent has processed that payload.
5.8. Bundle Fragmentation
It may at times be advantageous for bundle protocol agents to reduce
the sizes of bundles in order to forward them. This might be the
case, for example, if a node to which a bundle is to be forwarded is
accessible only via intermittent contacts and no upcoming contact is
long enough to enable the forwarding of the entire bundle.
The size of a bundle can be reduced by "fragmenting" the bundle. To
fragment a bundle whose payload is of size M is to replace it with
two "fragments" - new bundles with the same source node ID and
creation timestamp as the original bundle - whose payloads MUST be
the first N and the last (M - N) bytes of the original bundle's
payload, where 0 < N < M.
Note that fragments are bundles and therefore may themselves be
fragmented, so multiple episodes of fragmentation may in effect
replace the original bundle with more than two fragments. (However,
there is only one 'level' of fragmentation, as in IP fragmentation.)
Any bundle whose primary block's bundle processing flags do NOT
indicate that it must not be fragmented MAY be fragmented at any
time, for any purpose, at the discretion of the bundle protocol
agent. NOTE, however, that some combinations of bundle
fragmentation, replication, and routing might result in unexpected
traffic patterns.
Fragmentation SHALL be constrained as follows:
. The concatenation of the payloads of all fragments produced by
fragmentation MUST always be identical to the payload of the
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fragmented bundle (that is, the bundle that is being
fragmented). Note that the payloads of fragments resulting from
different fragmentation episodes, in different parts of the
network, may be overlapping subsets of the fragmented bundle's
payload.
. The primary block of each fragment MUST differ from that of the
fragmented bundle, in that the bundle processing flags of the
fragment MUST indicate that the bundle is a fragment and both
fragment offset and total application data unit length must be
provided. Additionally, the CRC of the primary block of the
fragmented bundle, if any, MUST be replaced in each fragment by
a new CRC computed for the primary block of that fragment.
. The payload blocks of fragments will differ from that of the
fragmented bundle as noted above.
. If the fragmented bundle is not a fragment or is the fragment
with offset zero, then all extension blocks of the fragmented
bundle MUST be replicated in the fragment whose offset is zero.
. Each of the fragmented bundle's extension blocks whose "Block
must be replicated in every fragment" flag is set to 1 MUST be
replicated in every fragment.
. Beyond these rules, rules for the replication of extension
blocks in the fragments must be defined in the specifications
for those extension block types.
5.9. Application Data Unit Reassembly
Note that the bundle fragmentation procedure described in 5.8 above
may result in the replacement of a single original bundle with an
arbitrarily large number of fragmentary bundles. In order to be
delivered at a destination node, the original bundle's payload must
be reassembled from the payloads of those fragments.
The "material extents" of a received fragment's payload are all
continuous sequences of bytes in that payload that do not overlap
with the material extents of the payloads of any previously received
fragments with the same source node ID and creation timestamp. If
the concatenation - as informed by fragment offsets and payload
lengths - of the material extents of the payloads of this fragment
and all previously received fragments with the same source node ID
and creation timestamp as this fragment forms a continuous byte
array whose length is equal to the total application data unit
length noted in the fragment's primary block, then:
. This byte array -- the reassembled application data unit --
MUST replace the payload of that fragment whose material
extents include the extent at offset zero. Note that this will
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enable delivery of the reconstituted original bundle as
described in Step 1 of 5.7.
. The "Reassembly pending" retention constraint MUST be removed
from every other fragment with the same source node ID and
creation timestamp as this fragment.
Note: reassembly of application data units from fragments occurs at
the nodes that are members of destination endpoints as necessary; an
application data unit MAY also be reassembled at some other node on
the path to the destination.
5.10. Bundle Deletion
The steps in deleting a bundle are:
Step 1: If the "request reporting of bundle deletion" flag in the
bundle's status report request field is set to 1, and if status
reporting is enabled, then a bundle deletion status report citing
the reason for deletion SHOULD be generated, destined for the
bundle's report-to endpoint ID.
Step 2: All of the bundle's retention constraints MUST be removed.
5.11. Discarding a Bundle
As soon as a bundle has no remaining retention constraints it MAY be
discarded, thereby releasing any persistent storage that may have
been allocated to it.
5.12. Canceling a Transmission
When requested to cancel a specified transmission, where the bundle
created upon initiation of the indicated transmission has not yet
been discarded, the bundle protocol agent MUST delete that bundle
for the reason "transmission cancelled". For this purpose, the
procedure defined in Section 5.10 MUST be followed.
6. Administrative Record Processing
6.1. Administrative Records
Administrative records are standard application data units that are
used in providing some of the features of the Bundle Protocol. One
type of administrative record has been defined to date: bundle
status reports. Note that additional types of administrative
records may be defined by supplementary DTN protocol specification
documents.
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Every administrative record consists of:
. Record type code (an unsigned integer for which valid values
are as defined below).
. Record content in type-specific format.
Valid administrative record type codes are defined as follows:
+---------+--------------------------------------------+
| Value | Meaning |
+=========+============================================+
| 1 | Bundle status report. |
+---------+--------------------------------------------+
| (other) | Reserved for future use. |
+---------+--------------------------------------------+
Figure 3: Administrative Record Type Codes
Each BP administrative record SHALL be represented as a CBOR array
comprising two items.
The first item of the array SHALL be a record type code, which SHALL
be represented as a CBOR unsigned integer.
The second element of this array SHALL be the applicable CBOR
representation of the content of the record. Details of the CBOR
representation of administrative record type 1 are provided below.
Details of the CBOR representation of other types of administrative
record type are included in the specifications defining those
records.
6.1.1. Bundle Status Reports
The transmission of "bundle status reports" under specified
conditions is an option that can be invoked when transmission of a
bundle is requested. These reports are intended to provide
information about how bundles are progressing through the system,
including notices of receipt, forwarding, final delivery, and
deletion. They are transmitted to the Report-to endpoints of
bundles.
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Each bundle status report SHALL be represented as a CBOR array. The
number of elements in the array SHALL be either 6 (if the subject
bundle is a fragment) or 4 (otherwise).
The first item of the bundle status report array SHALL be bundle
status information represented as a CBOR array of at least 4
elements. The first four items of the bundle status information
array shall provide information on the following four status
assertions, in this order:
. Reporting node received bundle.
. Reporting node forwarded the bundle.
. Reporting node delivered the bundle.
. Reporting node deleted the bundle.
Each item of the bundle status information array SHALL be a bundle
status item represented as a CBOR array; the number of elements in
each such array SHALL be either 2 (if the value of the first item of
this bundle status item is 1 AND the "Report status time" flag was
set to 1 in the bundle processing flags of the bundle whose status
is being reported) or 1 (otherwise). The first item of the bundle
status item array SHALL be a status indicator, a Boolean value
indicating whether or not the corresponding bundle status is
asserted, represented as a CBOR Boolean value. The second item of
the bundle status item array, if present, SHALL indicate the time
(as reported by the local system clock, an implementation matter) at
which the indicated status was asserted for this bundle, represented
as a DTN time as described in Section 4.2.6. above.
The second item of the bundle status report array SHALL be the
bundle status report reason code explaining the value of the status
indicator, represented as a CBOR unsigned integer. Valid status
report reason codes are registered in the IANA Bundle Status Report
Reason Codes registry in the Bundle Protocol Namespace (see 10.5
below). The initial contents of that registry are listed in Figure
4 below but the list of status report reason codes provided here is
neither exhaustive nor exclusive; supplementary DTN protocol
specifications (including, but not restricted to, the Bundle
Security Protocol [BPSEC]) may define additional reason codes.
+---------+--------------------------------------------+
| Value | Meaning |
+=========+============================================+
| 0 | No additional information. |
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+---------+--------------------------------------------+
| 1 | Lifetime expired. |
+---------+--------------------------------------------+
| 2 | Forwarded over unidirectional link. |
+---------+--------------------------------------------+
| 3 | Transmission canceled. |
+---------+--------------------------------------------+
| 4 | Depleted storage. |
+---------+--------------------------------------------+
| 5 | Destination endpoint ID unavailable. |
+---------+--------------------------------------------+
| 6 | No known route to destination from here. |
+---------+--------------------------------------------+
| 7 | No timely contact with next node on route. |
+---------+--------------------------------------------+
| 8 | Block unintelligible. |
+---------+--------------------------------------------+
| 9 | Hop limit exceeded. |
+---------+--------------------------------------------+
| 10 | Traffic pared (e.g., status reports). |
+---------+--------------------------------------------+
| 11 | Block unsupported. |
+---------+--------------------------------------------+
| (other) | Reserved for future use. |
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+---------+--------------------------------------------+
Figure 4: Status Report Reason Codes
The third item of the bundle status report array SHALL be the source
node ID identifying the source of the bundle whose status is being
reported, represented as described in Section 4.2.5.1.1. above.
The fourth item of the bundle status report array SHALL be the
creation timestamp of the bundle whose status is being reported,
represented as described in Section 4.2.7. above.
The fifth item of the bundle status report array SHALL be present if
and only if the bundle whose status is being reported contained a
fragment offset. If present, it SHALL be the subject bundle's
fragment offset represented as a CBOR unsigned integer item.
The sixth item of the bundle status report array SHALL be present if
and only if the bundle whose status is being reported contained a
fragment offset. If present, it SHALL be the length of the subject
bundle's payload represented as a CBOR unsigned integer item.
Note that the forwarding parameters (such as lifetime, applicable
security measures, etc.) of the bundle whose status is being
reported MAY be reflected in the parameters governing the forwarding
of the bundle that conveys a status report, but this is an
implementation matter. Bundle protocol deployment experience to
date has not been sufficient to suggest any clear guidance on this
topic.
6.2. Generation of Administrative Records
Whenever the application agent's administrative element is directed
by the bundle protocol agent to generate an administrative record,
the following procedure must be followed:
Step 1: The administrative record must be constructed. If the
administrative record references a bundle and the referenced bundle
is a fragment, the administrative record MUST contain the fragment
offset and fragment length.
Step 2: A request for transmission of a bundle whose payload is this
administrative record MUST be presented to the bundle protocol
agent.
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7. Services Required of the Convergence Layer
7.1. The Convergence Layer
The successful operation of the end-to-end bundle protocol depends
on the operation of underlying protocols at what is termed the
"convergence layer"; these protocols accomplish communication
between nodes. A wide variety of protocols may serve this purpose,
so long as each convergence layer protocol adapter provides a
defined minimal set of services to the bundle protocol agent. This
convergence layer service specification enumerates those services.
7.2. Summary of Convergence Layer Services
Each convergence layer protocol adapter is expected to provide the
following services to the bundle protocol agent:
. sending a bundle to a bundle node that is reachable via the
convergence layer protocol;
. notifying the bundle protocol agent of the disposition of its
data sending procedures with regard to a bundle, upon
concluding those procedures;
. delivering to the bundle protocol agent a bundle that was sent
by a bundle node via the convergence layer protocol.
The convergence layer service interface specified here is neither
exhaustive nor exclusive. That is, supplementary DTN protocol
specifications (including, but not restricted to, the Bundle
Security Protocol [BPSEC]) may expect convergence layer adapters
that serve BP implementations conforming to those protocols to
provide additional services such as reporting on the transmission
and/or reception progress of individual bundles (at completion
and/or incrementally), retransmitting data that were lost in
transit, discarding bundle-conveying data units that the convergence
layer protocol determines are corrupt or inauthentic, or reporting
on the integrity and/or authenticity of delivered bundles.
In addition, bundle protocol relies on the capabilities of protocols
at the convergence layer to minimize congestion in the store-carry-
forward overlay network. The potentially long round-trip times
characterizing delay-tolerant networks are incompatible with end-to-
end reactive congestion control mechanisms, so convergence-layer
protocols MUST provide rate limiting or congestion control.
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8. Implementation Status
[NOTE to the RFC Editor: please remove this section before
publication, as well as the reference to RFC 7942.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of
this Internet-Draft, and is based on a proposal described in RFC
7942. The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
According to RFC 7942, "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable
experimentation and feedback that have made the implemented
protocols more mature. It is up to the individual working groups to
use this information as they see fit".
At the time of this writing, there are six known implementations of
the current document.
The first known implementation is microPCN (https://upcn.eu/).
According to the developers:
The Micro Planetary Communication Network (uPCN) is a free
software project intended to offer an implementation of Delay-
tolerant Networking protocols for POSIX operating systems (well,
and for Linux) plus for the ARM Cortex STM32F4 microcontroller
series. More precisely it currently provides an implementation of
. the Bundle Protocol (BP, RFC 5050),
. version 6 of the Bundle Protocol version 7 specification
draft,
. the DTN IP Neighbor Discovery (IPND) protocol, and
. a routing approach optimized for message-ferry micro LEO
satellites.
uPCN is written in C and is built upon the real-time operating
system FreeRTOS. The source code of uPCN is released under the
"BSD 3-Clause License".
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The project depends on an execution environment offering link
layer protocols such as AX.25. The source code uses the USB
subsystem to interact with the environment.
The second known implementation is PyDTN, developed by X-works,
s.r.o (https://x-works.sk/). The final third of the implementation
was developed during the IETF 101 Hackathon. According to the
developers, PyDTN implements bundle coding/decoding and neighbor
discovery. PyDTN is written in Python and has been shown to be
interoperable with uPCN.
The third known implementation is "Terra"
(https://github.com/RightMesh/Terra/), a Java implementation
developed in the context of terrestrial DTN. It includes an
implementation of a "minimal TCP" convergence layer adapter.
The fourth and fifth known implementations are products of
cooperating groups at two German universities:
. An implementation written in Go, licensed under GPLv3, is
focused on being easily extensible suitable for research. It
is maintained at the University of Marburg and can be accessed
from https://github.com/dtn7/dtn7-go.
. An implementation written in Rust, licensed under the
MIT/Apache license, is intended for environments with limited
resources or demanding safety and/or performance requirements.
It is maintained at the Technical University of Darmstadt and
can be accessed at https://github.com/dtn7/dtn7-rs/.
The sixth known implementation is the "bpv7" module in version 4.0.0
of the Interplanetary Overlay Network (ION) software maintained at
the Jet Propulsion Laboratory, California Institute of Technology,
for the U.S. National Aeronautics and Space Administration (NASA).
9. Security Considerations
The bundle protocol security architecture and the available security
services are specified in an accompanying document, the Bundle
Security Protocol (BPsec) specification [BPSEC]. Whenever Bundle
Protocol security services (as opposed to the security services
provided by overlying application protocols or underlying
convergence-layer protocols) are required, those services SHALL be
provided by BPsec rather than by some other mechanism with the same
or similar scope.
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A Bundle Protocol Agent (BPA) which sources, cryptographically
verifies, and/or accepts a bundle MUST implement support for BPsec.
Use of BPsec for a particular Bundle Protocol session is optional.
The BPsec extensions to Bundle Protocol enable each block of a
bundle (other than a BPsec extension block) to be individually
authenticated by a signature block (Block Integrity Block, or BIB)
and also enable each block of a bundle other than the primary block
(and the BPsec extension blocks themselves) to be individually
encrypted by a Block Confidentiality Block (BCB).
Because the security mechanisms are extension blocks that are
themselves inserted into the bundle, the protections they afford
apply while the bundle is at rest, awaiting transmission at the next
forwarding opportunity, as well as in transit.
Additionally, convergence-layer protocols that ensure authenticity
of communication between adjacent nodes in BP network topology
SHOULD be used where available, to minimize the ability of
unauthenticated nodes to introduce inauthentic traffic into the
network. Convergence-layer protocols that ensure confidentiality of
communication between adjacent nodes in BP network topology SHOULD
also be used where available, to minimize exposure of the bundle's
primary block and other clear-text blocks, thereby offering some
defense against traffic analysis.
In order to provide authenticity and/or confidentiality of
communication between BP nodes, the convergence-layer protocol
requires as input the name(s) of the expected communication peer(s).
These must be supplied by the convergence-layer adapter. Details of
the means by which the CLA determines which CL endpoint name(s) must
be provided to the CL protocol are out of scope for this
specification. Note, though, that when the CL endpoint names are a
function of BP endpoint IDs, the correctness and authenticity of
that mapping will be vital to the overall security properties that
the CL provides to the system.
Note that, while the primary block must remain in the clear for
routing purposes, the Bundle Protocol could be protected against
traffic analysis to some extent by using bundle-in-bundle
encapsulation [BIBE] to tunnel bundles to a safe forward
distribution point: the encapsulated bundle could form the payload
of an encapsulating bundle, and that payload block could be
encrypted by a BCB.
Note that the generation of bundle status reports is disabled by
default because malicious initiation of bundle status reporting
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could result in the transmission of extremely large numbers of
bundles, effecting a denial of service attack. Imposing bundle
lifetime overrides would constitute one defense against such an
attack.
Note also that the reception of large numbers of fragmentary bundles
with very long lifetimes could constitute a denial of service
attack, occupying storage while pending reassembly that will never
occur. Imposing bundle lifetime overrides would, again, constitute
one defense against such an attack.
This protocol makes use of absolute timestamps for several purposes.
Provisions are included for nodes without accurate clocks to retain
most of the protocol functionality, but nodes that are unaware that
their clock is inaccurate may exhibit unexpected behavior.
10. IANA Considerations
The Bundle Protocol includes fields requiring registries managed by
IANA.
10.1. Bundle Block Types
The current Bundle Block Types registry in the Bundle Protocol
Namespace is augmented by adding a column identifying the version of
the Bundle protocol (Bundle Protocol Version) that applies to the
new values. IANA is requested to add the following values, as
described in section 4.3.1, to the Bundle Block Types registry. The
current values in the Bundle Block Types registry should have the
Bundle Protocol Version set to the value "6", as shown below.
+----------+-------+-----------------------------+---------------+
| Bundle | Value | Description | Reference |
| Protocol | | | |
| Version | | | |
+----------+-------+-----------------------------+---------------+
| none | 0 | Reserved | [RFC6255] |
| 6,7 | 1 | Bundle Payload Block | [RFC5050] |
| | | | RFC-to-be |
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| 6 | 2 | Bundle Authentication Block | [RFC6257] |
| 6 | 3 | Payload Integrity Block | [RFC6257] |
| 6 | 4 | Payload Confidentiality | [RFC6257] |
| | | Block | |
| 6 | 5 | Previous-Hop Insertion Block| [RFC6259] |
| 7 | 6 | Previous node (proximate | RFC-to-be |
| | | sender) | |
| 7 | 7 | Bundle age (in milliseconds)| RFC-to-be |
| 6 | 8 | Metadata Extension Block | [RFC6258] |
| 6 | 9 | Extension Security Block | [RFC6257] |
| 7 | 10 | Hop count (#prior xmit | RFC-to-be |
| | | attempts) | |
| 7 | 11-191| Unassigned | |
| 6,7 |192-255| Reserved for Private and/or | [RFC5050], |
| | | Experimental Use | RFC-to-be |
+----------+-------+-----------------------------+---------------+
10.2. Primary Bundle Protocol Version
IANA is requested to add the following value to the Primary Bundle
Protocol Version registry in the Bundle Protocol Namespace.
+-------+-------------+---------------+
| Value | Description | Reference |
+-------+-------------+---------------+
| 7 | Assigned | RFC-to-be |
+-------+-------------+---------------+
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Values 8-255 (rather than 7-255) are now Unassigned.
10.3. Bundle Processing Control Flags
The current Bundle Processing Control Flags registry in the Bundle
Protocol Namespace is augmented by adding a column identifying the
version of the Bundle protocol (Bundle Protocol Version) that
applies to the new values. IANA is requested to add the following
values, as described in section 4.1.3, to the Bundle Processing
Control Flags registry. The current values in the Bundle Processing
Control Flags registry should have the Bundle Protocol Version set
to the value 6 or "6, 7", as shown below.
Bundle Processing Control Flags Registry
+--------------------+----------------------------------+----------+
| Bundle | Bit | Description | Reference|
| Protocol| Position | | |
| Version | (right | | |
| | to left) | | |
+--------------------+----------------------------------+----------+
| 6,7 | 0 | Bundle is a fragment |[RFC5050],|
| | | |RFC-to-be |
| 6,7 | 1 | Application data unit is an |[RFC5050],|
| | | administrative record |RFC-to-be |
| 6,7 | 2 | Bundle must not be fragmented |[RFC5050],|
| | | |RFC-to-be |
| 6 | 3 | Custody transfer is requested |[RFC5050] |
| 6 | 4 | Destination endpoint is singleton|[RFC5050] |
| 6,7 | 5 | Acknowledgement by application |[RFC5050],|
| | | is requested |RFC-to-be |
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| 7 | 6 | Status time requested in reports |RFC-to-be |
| 6 | 7 | Class of service, priority |[RFC5050] |
| 6 | 8 | Class of service, priority |[RFC5050] |
| 6 | 9 | Class of service, reserved |[RFC5050] |
| 6 | 10 | Class of service, reserved |[RFC5050] |
| 6 | 11 | Class of service, reserved |[RFC5050] |
| 6 | 12 | Class of service, reserved |[RFC5050] |
| 6 | 13 | Class of service, reserved |[RFC5050] |
| 6,7 | 14 | Request reporting of bundle |[RFC5050],|
| | | reception |RFC-to-be |
| 6 | 15 | Request reporting of custody |[RFC5050] |
| | | acceptance | |
| 6,7 | 16 | Request reporting of bundle |[RFC5050],|
| | | forwarding |RFC-to-be |
| 6,7 | 17 | Request reporting of bundle |[RFC5050],|
| | | delivery |RFC-to-be |
| 6,7 | 18 | Request reporting of bundle |[RFC5050],|
| | | deletion |RFC-to-be |
| 6,7 | 19 | Reserved |[RFC5050],|
| | | |RFC-to-be |
| 6,7 | 20 | Reserved |[RFC5050],|
| | | |RFC-to-be |
| | 21-63 | Unassigned | |
+--------------------+----------------------------------+----------+
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10.4. Block Processing Control Flags
The current Block Processing Control Flags registry in the Bundle
Protocol Namespace is augmented by adding a column identifying the
version of the Bundle protocol (Bundle Protocol Version) that
applies to the related BP version. The current values in the Block
Processing Control Flags registry should have the Bundle Protocol
Version set to the value 6 or "6, 7", as shown below.
Block Processing Control Flags Registry
+--------------------+----------------------------------+----------+
| Bundle | Bit | Description | Reference|
| Protocol| Position | | |
| Version | (right | | |
| | to left) | | |
+--------------------+----------------------------------+----------+
| 6,7 | 0 | Block must be replicated in |[RFC5050],|
| | | every fragment |RFC-to-be |
| 6,7 | 1 | Transmit status report if block |[RFC5050],|
| | | can't be processed |RFC-to-be |
| 6,7 | 2 | Delete bundle if block can't be |[RFC5050],|
| | | processed |RFC-to-be |
| 6 | 3 | Last block |[RFC5050] |
| 6,7 | 4 | Discard block if it can't be |[RFC5050],|
| | | processed |RFC-to-be |
| 6 | 5 | Block was forwarded without |[RFC5050] |
| | | being processed | |
| 6 | 6 | Block contains an EID reference |[RFC5050] |
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| | | field | |
| | 7-63 | Unassigned | |
+--------------------+----------------------------------+----------+
10.5. Bundle Status Report Reason Codes
The current Bundle Status Report Reason Codes registry in the Bundle
Protocol Namespace is augmented by adding a column identifying the
version of the Bundle protocol (Bundle Protocol Version) that
applies to the new values. IANA is requested to add the following
values, as described in section 6.1.1, to the Bundle Status Report
Reason Codes registry. The current values in the Bundle Status
Report Reason Codes registry should have the Bundle Protocol Version
set to the value 6 or 7 or "6, 7", as shown below.
Bundle Status Report Reason Codes Registry
+--------------------+----------------------------------+----------+
| Bundle | Value | Description | Reference|
| Protocol| | | |
| Version | | | |
| | | | |
+--------------------+----------------------------------+----------+
| 6,7 | 0 | No additional information |[RFC5050],|
| | | |RFC-to-be |
| 6,7 | 1 | Lifetime expired |[RFC5050],|
| | | |RFC-to-be |
| 6,7 | 2 | Forwarded over unidirectional |[RFC5050],|
| | | link |RFC-to-be |
| 6,7 | 3 | Transmission canceled |[RFC5050],|
| | | |RFC-to-be |
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| 6,7 | 4 | Depleted storage |[RFC5050],|
| | | |RFC-to-be |
| 6,7 | 5 | Destination endpoint ID |[RFC5050],|
| | | unavailable |RFC-to-be |
| 6,7 | 6 | No known route to destination |[RFC5050],|
| | | from here |RFC-to-be |
| 6,7 | 7 | No timely contact with next node |[RFC5050],|
| | | on route |RFC-to-be |
| 6,7 | 8 | Block unintelligible |[RFC5050],|
| | | |RFC-to-be |
| 7 | 9 | Hop limit exceeded |RFC-to-be |
| 7 | 10 | Traffic pared |RFC-to-be |
| 7 | 11 | Block unsupported |RFC-to-be |
| | 12-254 | Unassigned | |
| 6,7 | 255 | Reserved |[RFC6255],|
| | | |RFC-to-be |
+-------+-----------------------------------------------+----------+
10.6. Bundle Protocol URI scheme types
The Bundle Protocol has a URI scheme type field - an unsigned
integer of indefinite length - for which IANA is requested to create
and maintain a new "Bundle Protocol URI Scheme Type" registry in the
Bundle Protocol Namespace. The "Bundle Protocol URI Scheme Type"
registry governs an unsigned integer namespace. Initial values for
the Bundle Protocol URI Scheme Type registry are given below.
The registration policy for this registry is: Standards Action. The
allocation should only be granted for a standards-track RFC approved
by the IESG.
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The value range is: unsigned integer.
Each assignment consists of a URI scheme type name and its
associated description, a reference to the document that defines the
URI scheme, and a reference to the document that defines the use of
this URI scheme in BP endpoint IDs (including the CBOR
representation of those endpoint IDs in transmitted bundles).
Bundle Protocol URI Scheme Type Registry
+---------+-------------+----------------+------------------+
| | | BP Utilization | URI Definition |
| Value | Description | Reference | Reference |
+---------+-------------+----------------+------------------+
| 0 | Reserved | n/a | |
| 1 | dtn | RFC-to-be | RFC-to-be |
| 2 | ipn | RFC-to-be | [RFC6260], |
| | | | RFC-to-be |
| 3-254 | Unassigned | n/a | |
|255-65535| reserved | n/a | |
| >65535 | open for | n/a | |
| | private use | n/a | |
+---------+-------------+----------------+------------------+
10.7. URI scheme "dtn"
In the Uniform Resource Identifier (URI) Schemes (uri-schemes)
registry, IANA is requested to update the registration of the URI
scheme with the string "dtn" as the scheme name, as follows:
URI scheme name: "dtn"
Status: permanent
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Applications and/or protocols that use this URI scheme name: the
Delay-Tolerant Networking (DTN) Bundle Protocol (BP).
Contact:
Scott Burleigh
Jet Propulsion Laboratory,
California Institute of Technology
scott.c.burleigh@jpl.nasa.gov
+1 (800) 393-3353
Change controller:
IETF, iesg@ietf.org
10.8. URI scheme "ipn"
In the Uniform Resource Identifier (URI) Schemes (uri-schemes)
registry, IANA is requested to update the registration of the URI
scheme with the string "ipn" as the scheme name, originally
documented in RFC 6260 [RFC6260], as follows.
URI scheme name: "ipn"
Status: permanent
Applications and/or protocols that use this URI scheme name: the
Delay-Tolerant Networking (DTN) Bundle Protocol (BP).
Contact:
Scott Burleigh
Jet Propulsion Laboratory,
California Institute of Technology
scott.c.burleigh@jpl.nasa.gov
+1 (800) 393-3353
Change controller:
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IETF, iesg@ietf.org
11. References
11.1. Normative References
[BPSEC] Birrane, E., "Bundle Security Protocol Specification",
draft-ietf-dtn-bpsec, January 2020.
[CRC16] ITU-T Recommendation X.25, p. 9, section 2.2.7.4,
International Telecommunications Union, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017.
[RFC8949] Borman, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 8949, December 2020.
[SABR] "Schedule-Aware Bundle Routing", CCSDS Recommended Standard
734.3-B-1, Consultative Committee for Space Data Systems, July 2019.
[TCPCL] Sipos, B., Demmer, M., Ott, J., and S. Perreault, "Delay-
Tolerant Networking TCP Convergence Layer Protocol Version 4",
draft-ietf-dtn-tcpclv4, January 2020.
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", RFC 3986, STD 66,
January 2005.
[URIREG] Thaler, D., Hansen, T., and T. Hardie, "Guidelines and
Registration Procedures for URI Schemes", RFC 7595, BCP 35, June
2015.
11.2. Informative References
[ARCH] V. Cerf et al., "Delay-Tolerant Network Architecture", RFC
4838, April 2007.
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[BIBE] Burleigh, S., "Bundle-in-Bundle Encapsulation", draft-ietf-
dtn-bibect, August 2019.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol
Specification", RFC 5050, November 2007.
[RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol
IANA Registries", RFC 6255, May 2011.
[RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell,
"Bundle Security Protocol Specification", RFC 6257, May 2011.
[RFC6258] Symington, S., "Delay-Tolerant Networking Metadata
Extension Block", RFC 6258, May 2011.
[RFC6259] Symington, S., "Delay-Tolerant Networking Previous-Hop
Insertion Block", RFC 6259, May 2011.
[RFC6260] Burleigh, S., "Compressed Bundle Header Encoding (CBHE)",
RFC 6260, May 2011.
[RFC7143] Chadalapaka, M., Satran, J., Meth, K., and D. Black,
"Internet Small Computer System Interface (iSCSI) Protocol
(Consolidated)", RFC 7143, April 2014.
[SIGC] Fall, K., "A Delay-Tolerant Network Architecture for
Challenged Internets", SIGCOMM 2003.
12. Acknowledgments
This work is freely adapted from RFC 5050, which was an effort of
the Delay Tolerant Networking Research Group. The following DTNRG
participants contributed significant technical material and/or
inputs to that document: Dr. Vinton Cerf of Google, Scott Burleigh,
Adrian Hooke, and Leigh Torgerson of the Jet Propulsion Laboratory,
Michael Demmer of the University of California at Berkeley, Robert
Durst, Keith Scott, and Susan Symington of The MITRE Corporation,
Kevin Fall of Carnegie Mellon University, Stephen Farrell of Trinity
College Dublin, Howard Weiss and Peter Lovell of SPARTA, Inc., and
Manikantan Ramadas of Ohio University.
This document was prepared using 2-Word-v2.0.template.dot.
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13. Significant Changes from RFC 5050
Points on which this draft significantly differs from RFC 5050
include the following:
. Clarify the difference between transmission and forwarding.
. Migrate custody transfer to the bundle-in-bundle encapsulation
specification [BIBE].
. Introduce the concept of "node ID" as functionally distinct
from endpoint ID, while having the same syntax.
. Restructure primary block, making it immutable. Add optional
CRC.
. Add optional CRCs to non-primary blocks.
. Add block ID number to canonical block format (to support
BPsec).
. Add definition of bundle age extension block.
. Add definition of previous node extension block.
. Add definition of hop count extension block.
. Remove Quality of Service markings.
. Change from SDNVs to CBOR representation.
. Add lifetime overrides.
. Time values are denominated in milliseconds, not seconds.
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Appendix A. For More Information
Copyright (c) 2021 IETF Trust and the persons identified as authors
of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
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Appendix B. CDDL expression
For informational purposes, Carsten Bormann and Brian Sipos have
kindly provided an expression of the Bundle Protocol specification
in the Concise Data Definition Language (CDDL). That CDDL
expression is presented below. Note that wherever the CDDL
expression is in disagreement with the textual representation of the
BP specification presented in the earlier sections of this document,
the textual representation rules.
bpv7_start = bundle / #6.55799(bundle)
; Times before 2000 are invalid
dtn-time = uint
; CRC enumerated type
crc-type = &(
crc-none: 0,
crc-16bit: 1,
crc-32bit: 2
)
; Either 16-bit or 32-bit
crc-value = (bstr .size 2) / (bstr .size 4)
creation-timestamp = [
dtn-time, ; absolute time of creation
sequence: uint ; sequence within the time
]
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eid = $eid .within eid-structure
eid-structure = [
uri-code: uint,
SSP: any
]
$eid /= [
uri-code: 1,
SSP: (tstr / 0)
]
$eid /= [
uri-code: 2,
SSP: [
nodenum: uint,
servicenum: uint
]
]
; The root bundle array
bundle = [primary-block, *extension-block, payload-block]
primary-block = [
version: 7,
bundle-control-flags,
crc-type,
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destination: eid,
source-node: eid,
report-to: eid,
creation-timestamp,
lifetime: uint,
? (
fragment-offset: uint,
total-application-data-length: uint
),
? crc-value,
]
bundle-control-flags = uint .bits bundleflagbits
bundleflagbits = &(
reserved: 21,
reserved: 20,
reserved: 19,
bundle-deletion-status-reports-are-requested: 18,
bundle-delivery-status-reports-are-requested: 17,
bundle-forwarding-status-reports-are-requested: 16,
reserved: 15,
bundle-reception-status-reports-are-requested: 14,
reserved: 13,
reserved: 12,
reserved: 11,
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reserved: 10,
reserved: 9,
reserved: 8,
reserved: 7,
status-time-is-requested-in-all-status-reports: 6,
user-application-acknowledgement-is-requested: 5,
reserved: 4,
reserved: 3,
bundle-must-not-be-fragmented: 2,
payload-is-an-administrative-record: 1,
bundle-is-a-fragment: 0
)
; Abstract shared structure of all non-primary blocks
canonical-block-structure = [
block-type-code: uint,
block-number: uint,
block-control-flags,
crc-type,
; Each block type defines the content within the bytestring
block-type-specific-data,
? crc-value
]
block-control-flags = uint .bits blockflagbits
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blockflagbits = &(
reserved: 7,
reserved: 6,
reserved: 5,
block-must-be-removed-from-bundle-if-it-cannot-be-processed: 4,
reserved: 3,
bundle-must-be-deleted-if-block-cannot-be-processed: 2,
status-report-must-be-transmitted-if-block-cannot-be-processed: 1,
block-must-be-replicated-in-every-fragment: 0
)
block-type-specific-data = bstr / #6.24(bstr)
; Actual CBOR data embedded in a bytestring, with optional tag to
indicate so.
; Additional plain bstr allows ciphertext data.
embedded-cbor<Item> = (bstr .cbor Item) / #6.24(bstr .cbor Item) /
bstr
; Extension block type, which does not specialize other than the
code/number
extension-block = $extension-block .within canonical-block-structure
; Generic shared structure of all non-primary blocks
extension-block-use<CodeValue, BlockData> = [
block-type-code: CodeValue,
block-number: (uint .gt 1),
block-control-flags,
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crc-type,
BlockData,
? crc-value
]
; Payload block type
payload-block = payload-block-structure .within canonical-block-
structure
payload-block-structure = [
block-type-code: 1,
block-number: 1,
block-control-flags,
crc-type,
$payload-block-data,
? crc-value
]
; Arbitrary payload data, including non-CBOR bytestring
$payload-block-data /= block-type-specific-data
; Administrative record as a payload data specialization
$payload-block-data /= embedded-cbor<admin-record>
admin-record = $admin-record .within admin-record-structure
admin-record-structure = [
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record-type-code: uint,
record-content: any
]
; Only one defined record type
$admin-record /= [1, status-record-content]
status-record-content = [
bundle-status-information,
status-report-reason-code: uint,
source-node-eid: eid,
subject-creation-timestamp: creation-timestamp,
? (
subject-payload-offset: uint,
subject-payload-length: uint
)
]
bundle-status-information = [
reporting-node-received-bundle: status-info-content,
reporting-node-forwarded-bundle: status-info-content,
reporting-node-delivered-bundle: status-info-content,
reporting-node-deleted-bundle: status-info-content
]
status-info-content = [
status-indicator: bool,
? timestamp: dtn-time
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]
; Previous Node extension block
$extension-block /=
extension-block-use<6, embedded-cbor<ext-data-previous-node>>
ext-data-previous-node = eid
; Bundle Age extension block
$extension-block /=
extension-block-use<7, embedded-cbor<ext-data-bundle-age>>
ext-data-bundle-age = uint
; Hop Count extension block
$extension-block /=
extension-block-use<10, embedded-cbor<ext-data-hop-count>>
ext-data-hop-count = [
hop-limit: uint,
hop-count: uint
]
Authors' Addresses
Scott Burleigh
Jet Propulsion Laboratory, California Institute of Technology
4800 Oak Grove Dr.
Pasadena, CA 91109-8099
US
Phone: +1 818 393 3353
Email: Scott.C.Burleigh@jpl.nasa.gov
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Kevin Fall
Roland Computing Services
3871 Piedmont Ave. Suite 8
Oakland, CA 94611
US
Email: kfall+rcs@kfall.com
Edward J. Birrane
Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Rd
Laurel, MD 20723
US
Phone: +1 443 778 7423
Email: Edward.Birrane@jhuapl.edu
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