| Internet-Draft | ipn-update | February 2024 |
| Taylor & Birrane | Expires 24 August 2024 | [Page] |
This document updates both the specification of the ipn URI scheme previously defined in RFC 7116 and the rules for encoding of these URIs when used as an Endpoint Identifier (EID) in Bundle Protocol Version 7 (BPv7) as defined in RFC 9171. These updates clarify the structure and behavior of the ipn URI scheme, define encodings of ipn scheme URIs, and establish the registries necessary to manage this scheme.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://ricktaylor.github.io/ipn2/draft-taylor-dtn-ipn-update.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-dtn-ipn-update/.¶
Discussion of this document takes place on the Delay/Disruption Tolerant Networking Working Group mailing list (mailto:dtn@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/dtn/. Subscribe at https://www.ietf.org/mailman/listinfo/dtn/.¶
Source for this draft and an issue tracker can be found at https://github.com/ricktaylor/ipn2.¶
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Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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This Internet-Draft will expire on 24 August 2024.¶
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The ipn URI scheme was originally defined in [RFC7116] as a way to identify network nodes and node services using concisely-encoded integers that can be processed faster and with fewer resources than other verbose identifier schemes. The scheme was designed for use with the experimental Bundle Protocol version 6 (BPv6, [RFC5050]) and IPN was defined as an acronym for the term "InterPlanetary Network" in reference to its intended use for deep-space networking. Since then, the efficiency benefit of integer identifiers makes ipn scheme URIs useful for any networks operating with limited power, bandwidth, and/or compute budget. Therefore, the term IPN is now used as a non-acronymous name.¶
Similar to the experimental BPv6, the standardized Bundle Protocol version 7 (BPv7, [RFC9171]) codifies support for the use of the ipn URI scheme for the specification of bundle Endpoint Identifiers (EIDs). The publication of BPv7 has resulted in operational deployments of BPv7 nodes for both terrestrial and non-terrestrial use cases. This includes BPv7 networks operating over the terrestrial Internet and BPv7 networks operating in self-contained environments behind a shared administrative domain. The growth in the number and scale of deployments of BPv7 DTNs has been accompanied by a growth in the usage of the ipn URI scheme which has highlighted areas to improve the structure, moderation, and management of this scheme.¶
By updating [RFC7116] and [RFC9171], this document updates the specification of the ipn URI scheme, in a backwards-compatible way, to provide needed improvements both in the scheme itself and its usage to specify EIDs with BPv7. Specifically, this document introduces a hierarchical structure for the assignment of ipn scheme URIs, clarifies the behavior and interpretation of ipn scheme URIs, defines efficient encodings of ipn scheme URIs, and updates/defines the registries associated for this scheme.¶
Although originally developed by the deep space community for use with Bundle Protocol, the ipn URI scheme is sufficiently generic to be used in other environments where a concise unique representation of a resource on a particular node is required.¶
It is important to remember that, like most other URI schemes, the ipn URI scheme defines a unique identifier of a resource, and does not include any topological information describing how to route messages to that resource.¶
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.¶
For the remainder of this document, the term "ipn URI" is used to refer to a URI that uses the ipn scheme.¶
Every ipn URI, no matter whether it is expressed with the textual representation or a binary encoding, MUST be considered as a tuple of the following three components:¶
The Allocator Identifier indicates the entity responsible for assigning Node Numbers to individual resource nodes, maintaining uniqueness whilst avoiding the need for a single registry for all assigned Node Numbers. See Allocator Identifiers (Section 3.2).¶
The Node Number is a shared identifier assigned to all ipn URIs for resources co-located on a single node. See Node Numbers (Section 3.3).¶
The Service Number is an identifier to distinguish between resources on a given node. See Service Numbers (Section 3.5).¶
The combination of these three components guarantees that every correctly constructed ipn URI uniquely identifies a single resource. Additionally, the combination of the Allocator Identifier and the Node Number provides a mechanism to uniquely identify the node on which a particular resource is expected to exist. See Fully-qualified Node Number (Section 3.3.1).¶
It has been found that there is value in defining a unique 'null' ipn URI to indicate "nowhere". This ipn URI is termed the "Null ipn URI", and has all three components: Allocator Identifier, Node Number, and Service Number, set to the value zero (0). No resource identified by Null ipn URI exists, and any such resource is therefore by definition unreachable.¶
An Allocator is any organization that wishes to assign Node Numbers for use with the ipn URI scheme, and has the facilities and governance to manage a public registry of assigned Node Numbers. The authorization to assign these numbers is provided through the assignment of an Allocator Identifier by IANA. Regardless of other attributes of an Allocator, such as a name, point of contact, or other identifying information, Allocators are identified by Allocator Identifiers: a unique, unsigned integer.¶
The Allocator Identifier MUST be the sole mechanism used to identify the Allocator that has assigned the Node Number in an ipn URI. An Allocator may have multiple assigned Allocator Identifiers, but a given Allocator Identifier MUST only be associated with a single Allocator.¶
A new IANA "'ipn' Scheme URI Allocator Identifiers" registry is defined for the registration of Allocator Identifiers, see 'ipn' Scheme URI Allocator Identifiers registry (Section 9.1). Although the uniqueness of Allocator Identifiers is required to enforce uniqueness of ipn URIs, some identifiers are explicitly reserved for experimentation or future use.¶
Each Allocator assigns Node Numbers according to its own policies, without risk of creating an identical ipn URI, as permitted by the rules in the Node Numbers (Section 3.3) section of this document. Other than ensuring that any Node Numbers it allocates are unique amongst all Node Numbers it assigns, an Allocator does not need to coordinate its allocations with other Allocators.¶
If a system does not require interoperable deployment of ipn scheme URIs, then the Private Use Node Number range, reserved by the Default Allocator (Section 3.2.2) for this purpose SHOULD be used.¶
Some organizations with internal hierarchies may wish to delegate the allocation of Node Numbers to one or more of their sub-organizations. Rather than assigning unique Allocator Identifiers to each sub-organization on a first-come first-served basis, there are operational benefits in assigning Allocator Identifiers to such an organization in a structured way so that an external observer can detect that a group of Allocator Identifiers are organizationally associated.¶
An Allocator Identifier range is a set of consecutive Allocator Identifiers associated with the same Allocator. Each individual Allocator Identifier in a given range SHOULD be assigned to a distinct sub-organization of the Allocator. Assigning identifiers in this way allows external observers both to associate individual Allocator Identifiers with a single organization and to usefully differentiate amongst sub-organizations.¶
The practice of associating a consecutive range of numbers with a single organization is inspired by the Classless Inter-domain Routing assignment of Internet Addresses described in [RFC4632]. In that assignment scheme, an organization (such as an Internet Service Provider) is assigned a network prefix such that all addresses sharing that same prefix are considered to be associated with that organization.¶
Each Allocator Identifier range is identified by the first Allocator Identifier in the range and the number of consecutive identifiers in the range.¶
Allocator Identifier ranges differ from CIDR addresses in two important ways.¶
Allocator Identifiers are used to identify organizations and are not, themselves, addresses.¶
Allocator Identifiers may be less than 32 bits in length.¶
In order to differentiate between Allocator Identifier ranges using efficient bitwise operations, all ranges MUST be of a size S that is a power of 2, and for a given range of length N bits, with S = 2^N, the least-significant N bits of the first Allocator Identifier MUST be all 0.¶
An example of the use of Allocator Identifier ranges for four organizations (A, B, C, and D) is as follows:¶
| Organization | Range (dec) | Range (hex) | Range Length (Bits) |
|---|---|---|---|
| Org A | 974848 .. 974975 | 0xEE000 .. 0xEE07F | 7 bits |
| Org B | 974976 .. 974991 | 0xEE080 .. 0xEE08F | 4 bits |
| Org C | 974992 .. 974993 | 0xEE090 .. 0xEE091 | 1 bit |
| Org D | 974994 | 0xEE092 | 0 bits |
With these assignments, any Allocator Identifier whose most-significant 25 bits match 0xEE000 belong to organization A. Similarly, any Allocator Identifier whose most-significant 28 bits match 0xEE080 belong to organization B, and any Allocator Identifier whose most-significant 31 bits are 0xEE090 belong to organization C. Organisation D has a single Allocator Identifier, and hence a range of bit-length 0.¶
As of the publication of [RFC7116], the only organization permitted to assign Node Numbers was the Internet Assigned Numbers Authority (IANA) which assigned Node Numbers via the IANA "CBHE Node Numbers" registry. This means that all ipn URIs created prior to the addition of Allocator Identifiers are assumed to have Node Number allocations that comply with the IANA "CBHE Node Numbers" registry.¶
The presumption that, unless otherwise specified, Node Numbers are allocated by IANA from a specific registry is formalized in this update to the ipn URI scheme by designating IANA as the Default Allocator, and by assigning the Allocator Identifier zero (0) in the 'ipn' Scheme URI Allocator Identifiers registry (Section 9.1) to the Default Allocator. In any case where an encoded ipn URI does not explicitly include an Allocator Identifier, an implementation MUST assume that the Node Number has been allocated by the Default Allocator.¶
A new IANA "'ipn' Scheme URI Default Allocator Node Numbers" registry is defined to control the allocation of Node Numbers values by the Default Allocator. This new registry inherits behaviours and existing assignments from the IANA "CBHE Node Numbers" registry, and reserves some other values as defined in the Special Node Numbers (Section 3.4) section below.¶
A Node Number identifies a node that hosts a resource in the context of an Allocator. A Node Number is an unsigned integer. A single Node Number assigned by a single Allocator MUST refer to a single node.¶
All Node Number assignments, by all Allocators, MUST be in the range 0 to 2^32-1.¶
It is RECOMMENDED that Node Number zero (0) not be assigned by an Allocator to avoid confusion with the Null ipn URI (Section 3.1).¶
One of the advantages of ipn URIs is the ability to easily split the identity of a particular service from the node upon which the service exists. For example a message received from one particular ipn URI may require a response to be sent to a different service on the same node that sent the original message. Historically the identifier of the sending node has been colloquially referred to as the "node number" or "node identifier".¶
To avoid future confusion, when referring to the identifier of a particular node the term "Fully-qualified Node Number" (FQNN) MUST be used to refer to the combination of the Node Number component and Allocator Identifier component of an ipn URI that uniquely identifies a particular node. In other words, an FQNN is the unique identifier of a particular node that supports services identified by ipn URIs.¶
In the examples in this document, FQNNs are written as (Allocator Identifier, Node Number), e.g., (977000,100) is the FQNN for a node assigned Node Number 100 by an Allocator with Allocator Identifier 977000.¶
Some special-case Node Numbers are defined by the Default Allocator, see 'ipn' Scheme URI Default Allocator Node Numbers registry (Section 9.2).¶
The Default Allocator assigns the use of Node Number zero (0) solely for identifying the Null ipn URI (Section 3.1).¶
This means that any ipn URI with a zero (0) Allocator Identifier and a zero (0) Node Number, but a non-zero Service Number component is invalid. Such ipn URIs MUST NOT be composed, and processors of such ipn URIs MUST consider them as the Null ipn URI.¶
The Default Allocator reserves Node Number 2^32-1 (0xFFFFFFFFF) to specify resources on the local node, rather than on any specific individual node.¶
This means that any ipn URI with a zero (0) Allocator Identifier and a Node Number of 2^32-1 refers to a service on the local bundle node. This form of ipn URI is termed a "LocalNode ipn URI".¶
The Default Allocator provides a range of Node Numbers that are reserved for "Private Use", as defined in [RFC8126].¶
Any ipn URI with a zero (0) Allocator Identifier and a Node Number reserved for "Private Use" is not guaranteed to be unique beyond a single administrative domain. An administrative domain, as used here, is defined as the set of nodes that share a unique allocation of FQNNs from the "Private Use" range. These FQNNs can be considered to be functionally similar to "Private Address Space" IPv4 addresses, as defined in [RFC1918].¶
Because of this lack of uniqueness, any implementation of a protocol using ipn URIs that resides on the border between administrative domains must have suitable mechanisms in place to prevent protocol units using such "Private Use" Node Numbers to cross between different administrative domains.¶
A Service Number is an unsigned integer that identifies a particular service operating on a node. A service in this case is some logical function that requires its own resource identifier to distinguish it from other functions operating on the same node.¶
All ipn scheme URIs comply with [RFC3986], and are therefore represented by scheme identifier, and a scheme-specific part. The scheme identifier is: ipn, and the scheme-specific parts are represented as a sequence of numeric components separated with the '.' character. It is formally defined in Appendix A (Appendix A), and can be informally considered as:¶
ipn:[<allocator-identifier>.]<node-number>.<service-number>¶
To keep the text representation concise, the follow rules apply:¶
All leading 0 characters MUST be omitted. A single '0' is valid.¶
If the Allocator Identifier is zero (0), then the <allocator-identifier> and '.' MUST be omitted.¶
If the Allocator Identifier is zero (0), and the Node Number is 2^32-1, i.e., the URI is a LocalNode ipn URI (Section 3.4.2), then the character '!' MAY be used instead of the digits 4294967295, although both forms are valid encodings.¶
Examples of the textual representation of ipn URIs can be found in Appendix B (Appendix B).¶
From the earliest days of experimentation with the Bundle Protocol there has been a need to identify the source and destination of a bundle. The IRTF BPv6 experimental specification termed the logical source or destination of a bundle as an "Endpoint" identified by an "Endpoint Identifier" (EID). BPv6 EIDs are formatted as URIs. This definition and representation of EIDs was carried forward from the IRTF BPv6 specification to the IETF BPv7 specification. BPv7 additionally defined an IANA registry called the "Bundle Protocol URI Scheme Types" registry which identifies those URI schemes than might be used to represent EIDs. The ipn URI scheme is one such URI scheme.¶
This section identifies the behavior and interpretation of ipn scheme URIs that MUST be followed when using this URI scheme to represent EIDs in BPv7. An ipn URI used as a BPv7 or BPv6 EID is termed an "ipn EID".¶
An ipn EID MUST identify a singleton endpoint. The bundle processing node that is the sole member of that endpoint MUST be the node identified by the Fully-qualified Node Number (Section 3.3.1) of the node.¶
A single bundle processing node MAY have multiple ipn EIDs associated with it. However, all ipn EIDs that share any single FQNN MUST refer to the same bundle processing node.¶
For example, ipn:977000.100.1, ipn:977000.100.2, and ipn:977000.100.3 MUST all refer to services registered on the bundle processing node identified with FQNN (977000,100). None of these EIDs could be registered on any other bundle processing node.¶
Section 3.2 of [RFC9171] defines the concept of the 'null' endpoint, which is an endpoint that has no members and which is identified by a special 'null' EID.¶
Within the ipn URI scheme, the 'null' EID is represented by the Null ipn URI (Section 3.1). This means that the URIs dtn:none (Section 4.2.5.1.1 of [RFC9171]) and ipn:0.0 both refer to the BPv7 'null' endpoint.¶
Section 4.2.5.2 of [RFC9171] introduces the concept of a "Node ID" that has the same format as an EID and that uniquely identifies a bundle processing node.¶
Any ipn EID can serve as a "Node ID" for the bundle processing node identified by its Fully-qualified Node Number (Section 3.3.1). That is, any ipn EID of the form ipn:A.B.C may be used as the Source Node ID of any bundle created by the bundle processing node identified by the FQNN (A,B).¶
When a LocalNode ipn URI (Section 3.4.2) is used as a BPv7 or BPv6 EID, it is termed a "LocalNode ipn EID".¶
Because a LocalNode ipn EID only has meaning on the local bundle node, any such EID MUST be considered 'non-routeable'. This means that any bundle using a LocalNode ipn EID as a bundle source or bundle destination MUST NOT be allowed to leave the local node. Equally, all externally received bundles featuring LocalNode EIDs as a bundle source or bundle destination MUST be discarded as invalid.¶
LocalNode ipn EIDs SHOULD NOT be present in any other part of a bundle that is transmitted off of the local node. For example, a LocalNode ipn EID SHOULD NOT be used as a Bundle Protocol Security [RFC9172] security source EID for a bundle transmitted from the local bundle node, because such a source EID would have no meaning at a downstream bundle node.¶
Bundles destined for EIDs that use an ipn URI with a Fully-qualified Node Number (Section 3.3.1) that is within the "Private Use" range of the Default Allocator (Section 3.2.2) are not universally unique, and therefore are only valid within the scope of the current administrative domain. This means that any bundle using a Private Use ipn EID as a bundle source or bundle destination MUST NOT be allowed to cross administrative domains. All implementations that could be deployed as a gateway between administrative domains MUST be sufficiently configurable to ensure that this is enforced, and operators MUST ensure correct configuration.¶
Private Use ipn EIDs SHOULD NOT be present in any other part of a bundle that is destined for another administrative domain when the lack of uniqueness prevents correct operation. For example, a Private Use ipn EID SHOULD NOT be used as a Bundle Protocol Security [RFC9172] security source EID for a bundle, when the bundle is destined for a different administrative domain.¶
It is convenient for BPv7 services that have a public specification and wide adoption to be identified by a pre-agreed default Service Number, so that unless extra configuration is applied, such services can be sensibly assumed to be operating on the well-known Service Number on a particular node.¶
If a different service uses the number, or the service uses a different number, BPv7 will continue to operate, but some configuration may be required to make the individual service operational.¶
A new IANA "'ipn' Scheme URI Well-known Service Numbers for BPv7" registry is defined for the registration of well-known BPv7 Service Numbers, see 'ipn' Scheme URI Well-known Service Numbers for BPv7 registry (Section 9.3). This registry records the assignments of Service Numbers for well-known services, and also explicitly reserves ranges for both experimentation and private use.¶
The service identified by a Service Number of zero (0) MUST be interpreted as the Administrative Endpoint of the node, as defined in Section 3.2 of [RFC9171].¶
Non-zero Service Numbers MUST NOT be used to identify the Administrative Endpoint of a bundle node in an ipn EID.¶
Section 4.2.5.1 of [RFC9171] requires that any URI scheme used to represent BPv7 EIDs MUST define how the scheme-specific part of the URI scheme is encoded with CBOR [RFC8949]. To meet this requirement, this section describes the CBOR encoding and decoding approach for ipn EIDs. The formal definition of these encodings is presented in Appendix C (Appendix C).¶
While there is a single, canonical, textual representation of an ipn URI, there may exist multiple encodings for that URI. For example, Section 2.1 of [RFC3986] defines a percent-encoding mechanism for a URI text string. Alternatively, Section 3.4.5.3 of [RFC8949] allows for the encoding of URIs as CBOR text strings identified with a CBOR tag value of 32.¶
Generic URI approaches to encoding ipn EIDs are unlikely to be efficient because they do not consider the underlying structure of the ipn URI scheme. Since the creation of the ipn URI scheme was motivated by the need for concise identification and rapid processing, the encoding of ipn EIDs maintains these properties.¶
Fundamentally, [RFC9171] ipn EIDs are represented as a sequence of identifiers. In the text syntax, the numbers are separated with the '.' delimiter; in CBOR, this ordered series of numbers can be represented by an array. Therefore, when encoding ipn EIDs for use with BPv7, the scheme-specific part of an ipn URI MUST be represented as a CBOR array of either two (2) or three (3) elements. Each element of the array MUST be encoded as a single CBOR unsigned integer.¶
The structure and mechanisms of the two-element and three-element encodings are described below, and examples of the different encodings are provided in Appendix D (Appendix D).¶
In the two-element scheme-specific encoding of an ipn EID, the first element of the array is an encoding of the Fully-qualified Node Number (Section 3.3.1) and the second element of the array is the ipn EID Service Number.¶
The FQNN encoding MUST be a 64 bit unsigned integer constructed in the following way:¶
The least significant 32 bits MUST represent the Node Number associated with the ipn EID.¶
The most significant 32 bits MUST represent the Allocator Identifier associated with the ipn EID.¶
For example the ipn EID of ipn:977000.100.1 has an FQNN of (977000,100) which would be encoded as 0xEE86800000064. The resulting two-element array [0xEE86800000064, 0x01] would be encoded in CBOR as the 11 octet value 0x821B000EE8680000006401.¶
The two-element scheme-specific encoding provides for backwards compatibility with the encoding provided in Section 4.2.5.1.2 of [RFC9171]. When used in this way, the encoding of the FQNN replaces the use of the "Node Number" that was specified in RFC9171. When the Node Number is allocated by the Default Allocator (Section 3.2.2), the encoding of the FQNN and the RFC9171 encoding of the "Node Number" are identical.¶
This encoding scheme MUST be implemented by any BPv7 bundle processing node that supports ipn URIs for the representation of BPv7 EIDs.¶
In the three-element scheme-specific encoding of an ipn EID, the first element of the array is the Allocator Identifier, the second element of the array is the Node Number, and the third element of the array is the Service Number.¶
For example, the ipn EID of ipn:977000.100.1 would result in the three-element array of [977000,100,1] which would be encoded in CBOR as the 9 octet value 0x831A000EE868186401.¶
The three-element scheme-specific encoding allows for a more efficient representation of ipn EIDs using smaller Allocator Identifiers.¶
When encoding an ipn EID using the Default Allocator (Section 3.2.2) with this encoding scheme, the first element of the array MUST be the value zero (0). In this case using the two-element encoding will result in a more concise CBOR representation, and it is RECOMMENDED that implementations do so.¶
The presence of different scheme-specific encodings does not introduce any decoding ambiguity.¶
An ipn EID CBOR decoder can reconstruct an ipn EID using the following logic. In this description, the term enc_eid refers to the CBOR encoded ipn EID, and the term ipn_eid refers to the decoded ipn EID.¶
if enc_eid.len() == 3
{
ipn_eid.allocator_identifier := enc_eid[0];
ipn_eid.node_number := enc_eid[1];
ipn_eid.service_number := enc_eid[2];
}
else if enc_eid.len() == 2
{
ipn_eid.allocator_identifier := enc_eid[0] >> 32;
ipn_eid.node_number := enc_eid[0] & (2^32-1);
ipn_eid.service_number := enc_eid[1];
}
¶
Regardless of whether the two-element or three-element scheme-specific encoding is used, ipn EID matching MUST be performed on the decoded EID information itself. Different encodings of the same ipn EID MUST be treated as equivalent when performing EID-specific functions.¶
For example, the ipn EID of ipn:977000.100.1 can be represented as either the two-element encoding of 0x821B000EE8680000006401 or the three-element encoding of 0x831A000EE868186401. While message integrity and other syntax-based checks may treat these values differently, any EID-based comparisons MUST treat these values the same - as representing the ipn EID ipn:977000.100.1.¶
The ipn URI scheme provides a compact and hierarchical mechanism for identifying services on network nodes. There is a significant amount of utility in the ipn URI scheme approach to identification. However, implementers should take into consideration the following observations on the use of the ipn URI scheme.¶
The ipn scheme update that has been presented in this document preserves backwards compatibility with any ipn URI scheme going back to the provisional definition of the ipn scheme in the experimental Compressed Bundle Header Encoding [RFC6260] specification in 2011. This means that any ipn URI that was valid prior to the publication of this update remains a valid ipn URI.¶
Similarly, the two-element scheme-specific encoding (Section 6.1.1) is also backwards compatible with the encoding of ipn URIs provided in [RFC9171]. Any existing RFC9171-compliant implementation will produce an ipn URI encoding in compliance with this specification.¶
The introduction of optional non-default Allocator Identifiers and a three-element scheme-specific encoding make this ipn URI scheme update not forwards compatible. Existing software for which support of this update is desired MUST be updated to be able to process non-default Allocator Identifiers and three-element scheme-specific encodings. It is RECOMMENDED that BPv7 implementations upgrade to process these new features to benefit from the scalability provided by Allocator Identifiers and the encoding efficiencies provided by the three-element encoding.¶
[RFC9171] mandates the concept of "late binding" of an EID, whereby the address of the destination of a bundle is resolved from its identifier hop-by-hop as it transits a DTN. This per-hop binding of identifiers to addresses underlines the fact that EIDs are purely names, and should not carry any implicit or explicit information concerning the current location or reachability of an identified node and service. This removes the need to rename a node as its location changes.¶
The concept of "late binding" is preserved in this ipn URI scheme. Elements of an ipn URI SHOULD NOT be regarded as carrying information relating to location, reachability, or other addressing/routing concern.¶
An example of incorrect behaviour would be to assume that a given Allocator assigns Node Numbers derived from link-layer addresses and to interpret the Node Number component of an ipn URI directly as a link-layer address. No matter the mechanism an Allocator uses for the assignment of Node Numbers, they remain just numbers, without additional meaning.¶
This section updates the security considerations from Section 4.2.5.1.2 of [RFC9171] to account for the inclusion of Allocator Identifiers in the ipn URI scheme when used with BPv7.¶
None of the BPv7 endpoints identified by ipn EIDs 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. Verification of the signature provided by the Block Integrity Block targeting the bundle's primary block, as defined by Bundle Protocol Security [RFC9172], is required for this purpose.¶
Malicious construction of a conformant ipn URI is limited to the malicious selection of Allocator Identifiers, Node Numbers, and Service Numbers. That is, a maliciously constructed ipn EID 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.¶
The limited expressiveness of URIs of the ipn scheme effectively eliminates the possibility of threat due to errors in back-end transcoding.¶
Both LocalNode (Section 3.4.2) and Private Use (Section 3.4.3) ipn URIs present a risk to the stability of deployed BPv7 networks. If either type of ipn URI are allowed to propagate beyond the domain in which they are valid, then the required uniqueness of ipn URIs no longer holds, and this fact can be abused by a malicious node to prevent the correct functioning of the network as a whole.¶
See LocalNode ipn EIDs (Section 5.4) and Private Use ipn EIDs (Section 5.5) for required behaviours to mitigate against this form of abuse.¶
Because ipn URIs are used only to represent the numeric identities of resources, the risk of disclosure of sensitive information due to interception of these URIs is minimal. Examination of ipn 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.¶
The simplicity of ipn URI scheme syntax minimizes the possibility of misinterpretation of a URI by a human user.¶
The following sections detail requests to IANA for the creation of two new registries, and the renaming of an existing registry.¶
IANA is requested to update the reference to the 'ipn' scheme is the "Uniform Resource Identifier (URI) Schemes" registry to this document.¶
IANA is requested to add the new registries, and relocate the existing registries under the "Uniform Resource Identifier (URI) Schemes" protocol registry.¶
IANA is requested to create a new registry entitled "'ipn' Scheme URI Allocator Identifiers". The registration policy for this registry, using terms defined in [RFC8126], is:¶
| Range | Registration Policy |
|---|---|
| 0 .. 2^16-1 | Expert Review, Single Allocator Identifiers only |
| 2^16 .. 2^30-1 | Expert Review |
| 2^30 .. 2^31-1 | Experimental Use |
| 2^31 .. 2^32-1 | Reserved, Future Expansion |
| >= 2^32 | Reserved |
Each entry in this registry associates one or more Allocator Identifiers with a single organization. Within the registry, the organization is identified using the "Name" and "Point of Contact" fields. It is expected that each identified organization publishes some listing of allocated node numbers - the pointer to which is listed in the "Reference" field of the registry.¶
Note that the “Single Allocator Identifiers only” language in Registration Policy for this registry indicates that, within the indicated range, the allocation of a sequence of consecutive Allocator identifiers to a single organization is prohibited. IANA is requested to note this in the registration policy for this registry.¶
The initial values for the registry are:¶
| Name | Range (dec) | Range (hex) | Range Length (Bits) | Reference | Point of Contact |
|---|---|---|---|---|---|
| Default Allocator (Section 3.2.2) | 0 | 0x0 | 0 | This document | IANA |
| Example Range | 974848 .. 978943 | 0xEE000 .. 0xEEFFF | 12 bits | This document | IANA |
The "Example Range" is assigned for use in examples in documentation and sample code.¶
Due to the nature of the CBOR encoding used for Allocator Identifiers with BPv7, Allocator Identifiers with a low value number are encoded more efficiently than larger numbers. This makes low value Allocator Identifiers more desirable than larger Allocator Identifiers, and therefore care must be taken when assigning Allocator Identifier ranges to ensure that a single applicant is not granted a large swathe of highly desirable numbers at the expense of other applicants. To this end, Designated Experts are strongly recommended to familiarize themselves with the CBOR encoding of unsigned integers in [RFC8949].¶
IANA is requested to rename the "CBHE Node Numbers" registry defined in Section 3.2.1 of [RFC7116] to the "'ipn' Scheme URI Default Allocator Node Numbers" registry.¶
The registration policy for this registry, using terms defined in [RFC8126], is updated to be:¶
| Range | Registration Policy |
|---|---|
| 0 | Reserved for the Null ipn URI (Section 3.1) |
| 1 .. 2^14-1 | Private Use |
| 2^14 .. 2^32-2 | Expert Review |
| 2^32-1 | Reserved for LocalNode ipn URIs (Section 3.4.2) |
| >= 2^32 | Invalid |
As IANA is requested to only rename the registry, all existing registrations will remain.¶
IANA is requested to create a new registry entitled "'ipn' Scheme URI Well-known Service Numbers for BPv7" registry. The registration policy for this registry, using terms defined in [RFC8126], is:¶
| Range | Registration Policy |
|---|---|
| 0 | Reserved for the Administrative Endpoint (Section 5.7) |
| 1..127 | Private Use |
| 128..255 | Standards Action |
| 0x0100 .. 0x7FFF | Private Use |
| 0x8000 .. 0xFFFF | Specification Required |
| 2^16 .. 2^32-1 | Private Use |
| >= 2^32 | Reserved for future expansion |
The initial values for the registry are:¶
| Value | Description | Reference |
|---|---|---|
| 0 | The Administrative Endpoint (Section 5.7) | [RFC9171], This document |
| 0xEEE0 .. 0xEEEF | Example Range | This document |
The "Example Range" is assigned for use in examples in documentation and sample code.¶
This registry is intended to record the default Service Numbers for well-known, interoperable services available and of use to the entire BPv7 community, hence all ranges not marked for Private Use MUST have a corresponding publicly available specification describing how one interfaces with the service.¶
Services that are specific to a particular deployment or co-operation may require a registry to reduce administrative burden, but do not require an entry in this registry.¶
The text syntax of an ipn URI MUST comply with the following ABNF [RFC5234] syntax, and reiterates the core ABNF syntax rule for DIGIT defined by that specification:¶
ipn-uri = "ipn:" ipn-hier-part ipn-hier-part = fqnn "." service-number fqnn = "!" / allocator-part allocator-part = [allocator-identifier "."] node-number allocator-identifier = non-zero-number node-number = number service-number = number number = "0" / non-zero-number non-zero-number = (%x31-39 *DIGIT) DIGIT = %x30-39¶
This section provides some example ipn URIs in their textual representation.¶
Consider the ipn URI identifying Service Number 2 on Node Number 1 allocated by the Default Allocator (Section 3.2.2) (0).¶
The complete seven character representation of this URI would be as follows:¶
ipn:1.2¶
Consider the ipn URI identifying Service Number 3 on Node Number 1 allocated by Allocator 977000.¶
The complete 14 character representation of this URI would be as follows:¶
ipn:977000.1.3¶
The Null ipn URI (Section 3.1) is represented as:¶
ipn:0.0¶
Consider the ipn URI identifying Service Number 7 on the local node.¶
The complete seven character representation of this URI would be as follows:¶
ipn:!.7¶
A BPv7 endpoint identified by an ipn URI, when encoded in Concise Binary Object Representation (CBOR) [RFC8949], MUST comply with the following Concise Data Definition Language (CDDL) [RFC8610] specification:¶
eid = $eid .within eid-structure eid-structure = [ uri-code: uint, SSP: any ] ; ... Syntax for other uri-code values defined in RFC9171 ... $eid /= [ uri-code: 2, SSP: ipn-ssp2 / ipn-ssp3 ] ipn-ssp2 = [ fqnn: uint, ; packed value service-number: uint ] ipn-ssp3 = [ authority-number: uint .lt 4294967296, node-number: uint .lt 4294967296, service-number: uint ]¶
Note: The node-number component will be the numeric representation of the concatenation of the Allocator Identifier and Node Number when the 2-element encoding scheme has been used.¶
This section provides some example CBOR encodings of ipn EIDs.¶
Consider the ipn EID ipn:1.1. This textual representation of an ipn EID identifies Service Number 1 on Node Number 1 allocated by the Default Allocator (Section 3.2.2) (0).¶
The complete five octet encoding of this EID using the two-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
82 # 2 Element ipn EID scheme-specific encoding
01 # Node Number
01 # Service Number
¶
The complete six octet encoding of this EID using the three-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
83 # 3 Element ipn EID scheme-specific encoding
00 # Default Allocator
01 # Node Number
01 # Service Number
¶
Consider the ipn EID ipn:977000.1.1. This textual representation of an ipn EID identifies Service Number 1 on Node Number 1 allocated by Allocator 977000.¶
The complete thirteen octet encoding of this EID using the two-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
82 # 2 Element ipn EID scheme-specific encoding
1B 000EE86800000001 # Fully-qualified Node Number
01 # Service Number
¶
The complete ten octet encoding of this EID using the three-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
83 # 3 Element ipn EID scheme-specific encoding
1A 000EE868 # Allocator Identifier
01 # Node Number
01 # Service Number
¶
The 'null' EID of ipn:0.0 can be encoded in the following ways:¶
The complete five octet encoding of the 'null' ipn EID using the two-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
82 # 2 Element ipn EID scheme-specific encoding
00 # Node Number
00 # Service Number
¶
The complete six octet encoding of the 'null'' ipn EID using the three-element scheme-specific encoding would be as follows:¶
82 # 2-Element Endpoint Encoding
02 # uri-code: 2 (IPN URI scheme)
83 # 3 Element ipn EID scheme-specific encoding
00 # Default Allocator
00 # Node Number
00 # Service Number
¶
The following DTNWG participants contributed technical material, use cases, and critical technical review for this URI scheme update: Scott Burleigh of the IPNGROUP, Keith Scott, Brian Sipos of the Johns Hopkins University Applied Physics Laboratory, Jorge Amodio of LJCV Electronics, and Ran Atkinson.¶
Additionally, the authors wish to thank members of the CCSDS SIS-DTN working group at large who provided useful review and commentary on this document and its implications for the future of networked space exploration.¶