Asynchronous Management Protocol
draft-birrane-dtn-amp-04
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draft-birrane-dtn-amp-04
Delay-Tolerant Networking E. Birrane
Internet-Draft Johns Hopkins Applied Physics Laboratory
Intended status: Standards Track June 4, 2018
Expires: December 6, 2018
Asynchronous Management Protocol
draft-birrane-dtn-amp-04
Abstract
This document describes a concise binary encoding of components of
the Asynchronous Management Model (AMM) and a binary protocol for the
exchange of these items over a nertwork. The intent of this protocol
is to provide an efficient exchange of management encoding that
conserves computing resources for embedded devices and energy
necessary for transmission of protocol data units. AMP is designed
to reduce the number of transmitted bytes, operates without sessions
or (concurrent) two-way links, and functions autnomously when there
is no timely contact with a network operator.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 6, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Protocol Scope . . . . . . . . . . . . . . . . . . . . . 3
3.2. Specification Scope . . . . . . . . . . . . . . . . . . . 4
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Constraints and Assumptions . . . . . . . . . . . . . . . . . 4
6. Technical Notes . . . . . . . . . . . . . . . . . . . . . . . 5
7. AMP-Specific Concepts . . . . . . . . . . . . . . . . . . . . 6
7.1. Nicknames (NN) . . . . . . . . . . . . . . . . . . . . . 6
7.1.1. Motivation for AId Compression . . . . . . . . . . . 7
7.1.2. ADM Enumeration . . . . . . . . . . . . . . . . . . . 7
7.1.3. ADM Template Area Enumeration . . . . . . . . . . . . 7
7.1.4. Nickname Definition . . . . . . . . . . . . . . . . . 8
7.1.5. ADM Enumeration Considerations . . . . . . . . . . . 9
8. Encodings . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. CBOR Considerations . . . . . . . . . . . . . . . . . . . 9
8.2. AMM Models . . . . . . . . . . . . . . . . . . . . . . . 10
8.2.1. Primitive and Derived Types . . . . . . . . . . . . . 10
8.2.2. Derived Types . . . . . . . . . . . . . . . . . . . . 12
8.2.3. Type-Name-Value (TNV) . . . . . . . . . . . . . . . . 12
8.2.4. ADM Identifier (AId) . . . . . . . . . . . . . . . . 13
8.3. Collections . . . . . . . . . . . . . . . . . . . . . . . 17
8.3.1. TNV Collection . . . . . . . . . . . . . . . . . . . 17
8.3.2. Types Then Value Collection (TTVC) . . . . . . . . . 18
8.3.3. AId Collections (AC) . . . . . . . . . . . . . . . . 19
8.3.4. Expressions (EXPR) . . . . . . . . . . . . . . . . . 20
8.3.5. Predicate (PRED) . . . . . . . . . . . . . . . . . . 20
8.4. ADM Object Definition Encodings . . . . . . . . . . . . . 20
8.4.1. Externally Defined Data (EDD) . . . . . . . . . . . . 21
8.4.2. Constants (CONST) . . . . . . . . . . . . . . . . . . 21
8.4.3. Controls (CTRL) . . . . . . . . . . . . . . . . . . . 22
8.4.4. Macros (MAC) . . . . . . . . . . . . . . . . . . . . 22
8.4.5. Operators (OP) . . . . . . . . . . . . . . . . . . . 23
8.4.6. Report Templates (RPTT) . . . . . . . . . . . . . . . 24
8.4.7. Report (RPT) . . . . . . . . . . . . . . . . . . . . 24
8.4.8. State-Based Rules (SRL) . . . . . . . . . . . . . . . 25
8.4.9. Table Templates (TBLT) . . . . . . . . . . . . . . . 27
8.4.10. Tables (TBL) . . . . . . . . . . . . . . . . . . . . 28
8.4.11. Time-Based Rules (TRL) . . . . . . . . . . . . . . . 29
8.4.12. Variables (VAR) . . . . . . . . . . . . . . . . . . . 30
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9. Functional Specification . . . . . . . . . . . . . . . . . . 31
9.1. AMP Message Summary . . . . . . . . . . . . . . . . . . . 31
9.2. Message Group Format . . . . . . . . . . . . . . . . . . 32
9.3. Message Format . . . . . . . . . . . . . . . . . . . . . 33
9.4. Register Agent . . . . . . . . . . . . . . . . . . . . . 34
9.5. Report Set . . . . . . . . . . . . . . . . . . . . . . . 35
9.6. Perform Control . . . . . . . . . . . . . . . . . . . . . 35
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
11. Security Considerations . . . . . . . . . . . . . . . . . . . 36
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
12.1. Informative References . . . . . . . . . . . . . . . . . 36
12.2. Normative References . . . . . . . . . . . . . . . . . . 36
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 37
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction
Network management in challenged and resource constrained networks
must be accommplished differently than the network management methods
in high-rate, high-availability networks. The Asynchronous
Management Architecture (AMA) [I-D.birrane-dtn-ama] provides an
overview and justification of an alternative to "synchronous"
management services such as those provided by NETCONF. In
particular, the AMA defines the need for a flexible, robust, and
efficient autonomy engine to handle decisions when operators cannot
be active in the network. The logical description of that autonomous
model and its major components is given in the AMA Data Model (ADM)
[I-D.birrane-dtn-adm].
The ADM presents an efficient and expressive autonomy model for the
asynchronous management of a network node, but does not specify any
particular encoding. This document, the Asynchronous Management
Protocol (AMP), provides a compact, binary encoding of ADM objects
and specifies a protocol for the exchange of these encoded objects.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Scope
3.1. Protocol Scope
The AMP provides data monitoring, administration, and configuration
for applications operating above the data link layer of the OSI
networking model. While the AMP may be configured to support the
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management of network layer protocols, it also uses these protocol
stacks to encapsulate and communicate its own messages.
It is assumed that the protocols used to carry AMP messages provide
addressing, confidentiality, integrity, security, fragmentation, and
other network/session layer functions. Therefore, these items are
outside of the scope of this document.
3.2. Specification Scope
This document describes the format of messages used to exchange data
models between managing and managed devices in a network. The
rationale for this type of exchange is outside of the scope of this
document as it is covered in [I-D.birrane-dtn-ama]. The description
and explanation of the data models exchanged is also outside of the
scope of this document as it is covered in [I-D.birrane-dtn-adm].
This document does not address specific data configurations of AMP-
enabled devices, nor does it discuss the interface between AMP and
other management protocols.
4. Terminology
Note: The terms "Actor", "Agent", "Application Data Model",
"Externally Defined Data", "Variable", "Control", "Literal", "Macro",
"Manager", "Report Template", "Report Entry", "Table", "Constant",
"Operator", "Time-Based Rule" and "State-Based Rule" are used without
modification from the definitions provided in [I-D.birrane-dtn-adm].
5. Constraints and Assumptions
The desirable properties of an asynchronous management protocol, as
specified in the AMA, are summarized here to represent design
constraints on the AMP specification.
o Intelligent Push of Information - Nodes in a challenged network
cannot guarantee concurrent, bi-directional communications. Some
links between nodes may be strictly uni-directional. AMP should
"push" data to nodes rather than "pull" data from nodes.
o Small Message Sizes - Smaller messages require smaller periods of
viable transmission for communication, incur less retransmission
cost, and consume fewer resources when persistently stored enroute
in the network. AMP should minimize message size wherever
practical, to include binary data representations and assuming
pre-defined data definitions and schemas.
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o Absolute and Custom Data Identification - All data in the system
must be uniquely addressable, to include operator-specified
information. AMP should provide an efficient mechanism for
encoding these unique identifiers.
o Autonomous, Stateless Operation - There is no reliable concept of
session establishment or round-trip data exchange in asynchronous
networks. AMP should be stateless. Where helpful, AMP should
provide a mechanism for transactional ordering of commands within
a single AMP protocol data unit. AMP should degrade gracefully
when nodes in the network fail to converge on common definitions.
o Compatibility with Low-Latency Network Management Protocols - AMP
encoding should be compatible with identifiers and encodings used
by synchronous network management protocols. While this
compatibility does not need to be embedded in the AMP encoding
itself, a deterministic, mechanical translation to and from other
encodings should be supported.
6. Technical Notes
o Unless otherwise specified, multi-byte values in this
specification are expected to be transmitted in network byte order
(Big Endian).
o Character encodings for all text-based data types will use UTF-8
encodings.
o All encodings and AMP-specific types defined by the AMP are self-
terminating. This means that, given an indefinite-length octet
stream, each encoding can be unambiguously decoded from the stream
without requiring additional information such as a length field
separate from the data type definition.
o Bit-fields in this document are specified with bit position 0
holding the least-significant bit (LSB). When illustrated in this
document, the LSB appears on the right.
o In order to describe the encoding of data models specified in
[I-D.birrane-dtn-adm], this specification must refer to both the
data object being encoded and to the encoding of that data object.
When discussing the encoded version of a data object, this
specification uses the notation "E(data_object)" where E() refers
to a conceptual encoding function. This notation is only provided
as a means of clarifying the text and imposes no changes to the
actual wire coding. For example, this specification will refer to
the "macro" data object as "Macro" and to the encoding of a Macro
as "E(Macro)".
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o Illustrations of fields in this specification consist of the name
of the field, the type of the field between []'s, and if the field
is optional, the text "(opt)".
Field order is deterministic and, therefore, fields MUST be
transmitted in the order in which they are specified. In cases
where an optional field is not present, then the next field will
be considered for transmission.
An example is shown in Figure 1 below. In this illustration two
fields (Field 1 and Field 2) are shown, with Field 1 of Type 1 and
Field 2 of Type 2. Field 2 is also listed as being optional.
Byte fields are shown in order of receipt, from left-to-right.
Therefore, when transmitted on the wire, Field 1 will be received
first, followed by Field 2 (if present).
+----------+----------+
| Field 1 | Field 2 |
| [TYPE 1] | [TYPE 2] |
| | (opt) |
+----------+----------+
Figure 1: Byte Field Formatting Example
When types are documented in this way, the type always refers to
the encoding of that type. The E() notation is not used as it is
to be inferred from the context of the illustration.
7. AMP-Specific Concepts
The AMP specification provides an encoding of items comprising the
asynchronous data model. As such, AMP defines very few structures of
its own. This section identifies those few data structures that are
unique to the AMP and required for it to perform appropriate and
efficient encodings of model elements.
7.1. Nicknames (NN)
In the AMP, a "Nickname" is the compression of a shared portion of an
ADM Identifier (AId). In this case, compression refers to a
structured enumeration of ADMs and types within those ADMs. In this
structured enumeration, each ADM is enumerated and each element in
the standard ADM template is enumerated and the nickname is a number
derived as a function of the two.
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7.1.1. Motivation for AId Compression
AIds uniquely identify data model elements. In cases where the data
model being identified is simple (such as a UINT), the size of the
encoding of the AId will dominate the total size of the encoded data
item. To reduce the overall size of data exchanged over AMP, the
encoding of the AId must be as efficient as possible.
A potentially large source of inefficiency in the AId structure stems
from the fact that data items are grouped by (1) the ADM in which
they are defined and (2) the section within the ADM. In certain
circumstances, groups of model elements will have AIds that have only
minor differences. Consider the following set of AIDs.
DTN:adm1.type1.item_1 DTN:adm1.type1.item_2 ...
DTN:adm1.type1.item_1974
In this example, the encoding of the "DTN:adm1.type1." portion of
each individual AId results in inefficient bandwidth utilization.
7.1.2. ADM Enumeration
An ADM enumeration is an unsigned integer in the range of 0 to
(2^64)/20. This range provides effective support for thousands of
trillions of ADMs.
The formal set of ADMs, similar to SNMP MIBs and NETCONF YANG models,
will be moderated and published. Additionally, a set of informal
ADMs may be developed on a network-by-network or on an organization-
by-organization bases.
Since informal ADMs exist within a predefined context (a network, an
organization, or some other entity) they do not have individual ADM
enumerations. As such, any informal ADM will be given the special
enumeration "0", which will stand for "informal ADM" and will rely on
other context information provided in the AId encoding (see
Section 8.2.4).
Formal ADMs are presumed to be less ephemeral as they involve the
time and effort and cost of moderation, publication, and maintenance.
As such, a nickname will be allocated for each such formally defined
ADM.
7.1.3. ADM Template Area Enumeration
An ADM Template Area Enumeration is an unsigned integer in the range
of 0 - 19. This covers all of the standard areas for the ADM
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Template as defined in [I-D.birrane-dtn-adm]. Each of these types
are enumerated in Table 1.
+------------------+-------------+
| Area | Enumeration |
+------------------+-------------+
| metadata | 0 |
| | |
| edds | 1 |
| | |
| tables | 2 |
| | |
| variables | 3 |
| | |
| report templates | 4 |
| | |
| controls | 5 |
| | |
| macros | 6 |
| | |
| operators | 7 |
| | |
| constants | 8 |
| | |
| reserved | 9-19 |
+------------------+-------------+
Table 1: ADM Type Enumerations
7.1.4. Nickname Definition
As an enumeration, a Nickname is captured as a 64-bit unsigned
integer (UVAST) calculated as a function of the ADM enumeration and
the ADM type enumeration, as follows.
NN = ((ADM Enumeration) * 20) + (ADM Template Area Enumeration)
Considering the example set of AIds from Section 7.1.1, assuming that
adm1 has ADM enumeration 9 and that type1 refers to Macros and, as
such, has ADM Template Area Enumeration 6, the shared nickname for
the 1974 items would be: (6 * 20) + 6 = 126. In this particular
example, each AId can be encoded in no more than 3 bytes: one byte to
hold the nickname and up to two bytes to hold the item number (0 -
1974).
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7.1.5. ADM Enumeration Considerations
The selection of formal ADM enumerations SHOULD take into
consideration the nature of the applications and protocols to which
the ADM applies. Those ADMs that are likely to be used in challenged
networks SHOULD be allocated low enumeration numbers (e.g. those that
will fit into 1-2 bytes) while ADMs that are likely to only be used
in well resourced networks SHOULD be allocated higher enumeration
numbers. It SHOULD NOT be the case that ADM enumerations are
allocated on a first-come, first-served basis. It is recommended
that ADM enumerations should be labeled based on the number of bytes
of the Nickname as a function of the size of the ADM enumeration.
These labels are shown in Table 2.
+-------------+--------+--------------+-----------------------------+
| ADM Enum | NN | Label | Comment |
| | Size | | |
+-------------+--------+--------------+-----------------------------+
| 0x1 - 0xCCC | 1-2 | Challenged | Constraints imposed by |
| | Bytes | Networks | physical layer and power. |
| | | | |
| 0xCCD - | 3-4 | Congested | Constraints imposed by |
| 0xCCCCCCC | Bytes | Networks | network traffic. |
| | | | |
| >=0xCCCCCCD | 5-8 | Resourced | Generally unconstrained |
| | Bytes | Networks | networks. |
+-------------+--------+--------------+-----------------------------+
Table 2: ADM Enumerations Labels
8. Encodings
This section describes the binary encoding of logical data constructs
using the Concise Binary Object Representation (CBOR).
8.1. CBOR Considerations
The following considerations act as guidance for CBOR encoders and
decoders implementing the AMP.
o All AMP encodings are of definite length and, therefore,
indefinite encodings MUST NOT be used.
o AMP encodings MUST NOT use CBOR tags. Identification mechanisms
in the AMP capture structure and other information such that tags
are not necessary.
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o Canonical CBOR MUST be used for all encoding. All AMP CBOR
decoders MUST run in strict mode.
o Encodings MUST result in smallest data representations. There are
several cases where the ADM defines types with less granularity
than CBOR. For example, ADM defines the UINT type to represent
unsigned integers up to 32 bits in length. CBOR supports separate
definitions of unsigned integers of 8, 16, or 32 bits in length.
In cases where an ADM type MAY be encoded in multiple ways in
CBOR, the smallest data representation MUST be used. For example,
UINT values of 0-255 MUST be encoded as a uint8_t, and so on.
8.2. AMM Models
8.2.1. Primitive and Derived Types
The AMP supports types for unsigned bytes, 32/64-bit signed and
unsigned integers, 32/64-bit floating point values, and strings, as
outlined in Table 3.
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+---------+-------------+---------------+---------------------------+
| AMP | CBOR Major | CBOR | Comments |
| Type | Type | Additional | |
| | | Value | |
+---------+-------------+---------------+---------------------------+
| BYTE | 7 | 0-23 or 24 | BYTEs are simple values |
| | (Primitive) | | in CBOR. |
| | | | |
| INT | 0 | 0-23,24,25,26 | INTs are encoded are |
| | (Positive), | | positive or negative |
| | 1 | | integers from (u)int8_t |
| | (Negative) | | up to (u)int32_t. |
| | | | |
| UINT | 0 | 0-23, 24, 25, | UINTs are positive |
| | | 26 | integers from uint8_t up |
| | | | to uint32_t. |
| | | | |
| VAST | 0 | 27 | VASTs are encoding as |
| | (Positive), | | (u)int64_t. |
| | 1(Negative) | | |
| | | | |
| UVAST | 0 | 27 | VASTs are encoding as |
| | | | uint64_t. |
| | | | |
| REAL32 | 7 | 26 | Single-precision, 32-bit |
| | (Primitive) | | floating point value in |
| | | | IEEE-754 format. |
| | | | |
| REAL64 | 7 | 27 | Double-precision, 64-bit |
| | (Primitive) | | floating point value in |
| | | | IEEE-754 format. |
| | | | |
| STR | 3 (Text | Varies | Uses CBOR encoding |
| | String) | | unmodified. |
| | | | |
| BOOL | 7 | 0 or 1 | AV of 0 is considered |
| | (Primitive) | | FALSE. AV of 1 considered |
| | | | TRUE. |
| | | | |
| TS | 0 | Varies | Timestamp in the smallest |
| | (Positive) | | of uint8_t, uint16_t, |
| | | | uint32_t, or uint64_t. |
| | | | |
| BLOB | 2 (Byte | Varies | Uses CBOR encoding |
| | String) | | unmodifed |
+---------+-------------+---------------+---------------------------+
Table 3: Standard Numeric Types
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8.2.2. Derived Types
The AMP supports types for unsigned bytes, 32/64-bit signed and
unsigned integers, 32/64-bit floating point values, and strings, as
outlined in Table 4.
+---------+--------------+-------------+----------------------------+
| AMP | CBOR Major | CBOR | Comments |
| Type | Type | Additional | |
| | | Value | |
+---------+--------------+-------------+----------------------------+
| TS | 7 | 0-23 or 24 | BYTEs are simple values in |
| | (Primitive) | | CBOR. |
+---------+--------------+-------------+----------------------------+
Table 4: Standard Numeric Types
8.2.3. Type-Name-Value (TNV)
TNV values are encoded as a CBOR array that comprises four distinct
pieces of information: a set of flags, a type, an optional name, and
an optional value. In the E(TNV) the flag and type information are
compressed into a single value. The CBOR array MUST have length 2,
3, or 4 depending on the number of optional fields appearing in the
encoding. The E(TNV) format is illustrated in Figure 2.
+---------+
| TNV |
| [ARRAY] |
+----++---+
||
||
_______________________/ \_______________________
/ \
+--------------+------------+-----------+----------+
| Array Header | Flags/Type | Name | Value |
| [UINT] | [UINT] | [TXT STR] | [Varies] |
| | | (opt) | (opt) |
+--------------+------------+-----------+----------+
Figure 2: E(TNV) Format
The E(TNV) fields are defined as follows.
Flags/Type
The first byte of the E(TNV) describes the type associated
with the TNV and which optional components are present. The
layout of this byte is illustrated in Figure 3.
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E(TNV) Flag/Type Byte Format
+------+-------+-------------+
| Name | Value | Struct |
| Flag | Flag | Type |
+------+-------+-------------+
| 7 | 6 | 5 4 3 2 1 0 |
+------+-------+-------------+
MSB LSB
Figure 3
Name Flag
This flag indicates that the TNV contains a name
field. When set to 1 the Name field MUST be present
in the E(TNV). When set to 0 the Name field MUST NOT
be present in the E(TNV).
Value Flag
This flag indicates that the TNV contains a value
field. When set to 1 the Value field MUST be present
in the E(TNV). When set to 0 the Value field MUST
NOT be present in the E(TNV).
Struct Type
This field lists the type associated with this TNV
and MUST contain one of the types defined in
[I-D.birrane-dtn-adm] with the exception that the
type of a TNV MUST NOT be a TNV.
Name
This optional field captures the human-readable name for the
TNV encoded as a CBOR text string (major type 3).
Value
This optional field captures the encoded value associated
with this TNV. The value is encoded in accordance with AMP
rules for encoding of items of the type of this TNV.
8.2.4. ADM Identifier (AId)
The AId, as defined in [I-D.birrane-dtn-adm], identifies an ADM
object. There are two kinds of ADM objects that can be identified in
this scheme: literal objects (of ADM type LITERAL) and all other ADM
objects.
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8.2.4.1. Encoding ADM Objects of Type LITERAL
A literal identifier is one that is literally defined by its value,
such as the numbers (0, 3.14) and strings ("example"). AIds of type
LITERAL do not have issuers or nicknames or parameters. They are
simply typed basic values.
The E(AId) of an ADM of type LITERAL is encoded as a CBOR Byte String
and consists of a mandatory flag BYTE and the value of the LITERAL.
The E(AId) structure for LITERALS is illustrated in Figure 4.
E(AId) Literal Format
+--------+----------+
| Flags | Value |
| [BYTE] | [VARIES] |
| | |
+--------+----------+
Figure 4
These fields are defined as follows.
Flags
The Flags byte identifies the ADM object as being of type
LITERAL and also captures the primitive type of the following
value. The layout of this byte is illustrated in Figure 5.
E(AId) Literal Flag Byte Format
+------------+-------------+
| VALUE TYPE | STRUCT TYPE |
+------------+---------+----
| 7 6 5 4 | 3 2 1 0 |
+------------+-------------+
MSB LSB
Figure 5
Value Type
The high nibble of the flag byte describes the type
of the value of the AId being encoded. This type
MUST be one of the ADM structure types defined in
[I-D.birrane-dtn-adm]. as a "Primitive Type".
Structure Type
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The lower nibble of the flag byte identifies the type
of ADM Object being identified by the AId. In this
instance, this value MUST be LITERAL, as defined in
[I-D.birrane-dtn-adm].
Value
This field captures the CBOR encoding of the value. Values
are encoded according to their Value Type as specified in the
flag byte in accordance with the encoding rules provided in
Section 8.2.1.
8.2.4.2. Encoding Non-Literal ADM Objects
All other AIds are defined in the context of ADM structures,
templates, issuing organizations and may contain parameters and other
meta-data. The AMP, as a binary encoding of this information meant
to exchange ADM models in a machine-to-machine context removes human-
readable information such as Name and Description. Additionally,
this encoding adds other information to improve the efficiency of the
AId encoding, such as the concept of Nicknames as defined in
Section 7.1.
The E(AId) is encoded as a CBOR Byte String and consists of a
mandatory flag BYTE, a mandatory ADM Resource Identifier (ARI), and
optional annotations to assist with filtering, access control, and
parameterization. The E(AId) structure is illustrated in Figure 6.
E(AId) General Format
+--------+---------+---------+---------+---------+------------+
| Flags | NN | ARI | Parms | Issuer | Tag |
| [BYTE] | [UVAST] | [UVAST] | [ARRAY] | [UVAST] | [BYTE STR] |
| | (opt) | | (opt) | (opt) | (opt) |
+--------+---------+---------+---------+---------+------------+
Figure 6
These fields are defined as follows.
Flags
Flags describe the type of structure and which optional
fields are present in the encoding. The layout of the flag
byte is illustrated in Figure 7.
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E(AId) General Flag Byte Format
+----+------+-----+-----+-------------+
| NN | PARM | ISS | TAG | STRUCT TYPE |
+----+------+-----+-----+-------------+
| 7 | 6 | 5 | 4 | 3 2 1 0 |
+----+------+-----+-----+-------------+
MSB LSB
Figure 7
Nickname (NN)
This flag indicates that ARI compression is used for
this E(Aid). When set to 1 the Nickname field MUST
be present in the E(AId). When set to 0 the Nickname
field MUST NOT be present in the E(AId). When an AId
is user-defined, there are no semantics for Nicknames
and, therefore, this field MUST be 0 when the Issuer
flag is set to 1. Implementations SHOULD use
Nicknames whenever possible to reduce the size of the
E(AId).
Parameters Present (PARM)
This flag indicates that this AId can be
parameterized and that parameter information is
included in the E(AId). When set to 1 the Parms
field MUST be present in the E(AId). When set to 0
the Parms field MUST NOT be present in the E(AId).
Issuer Present (ISS)
This flag indicates that this AId is defined in the
context of a specific issuing entity. When set to 1
the Issuer field MUST be present in the E(AId). When
set to 0 the Issuer field MUST NOT be present in the
E(AId).
Tag Present (TAG)
This flag indicates that the AId is defined in the
context of a specific issuing entity and that issuing
entity adds additional information in the form of a
tag. When set to 1 the Tag field MUST be present in
the E(AId). When set to 0 the Tag field MUST NOT be
present in the E(AId). This flag MUST be set to 0 if
the Issuer Present flag is set to 0.
Structure Type (STRUCT TYPE)
The lower nibble of the E(AId) flag byte identifies
the kind of data structure being identified. This
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field MUST contain one of the ADM structure types
defined in [I-D.birrane-dtn-adm].
Nickname (NN)
This optional field contains the Nickname as calculated
according to Section 8.2.4.
ADM Resource Identifier (ARI)
This mandatory field contains the enumeration of the ADM
object. For elements defined in an ADM Template (e.g., where
the Issuer Flag is set to 0) this is the 0-based index into
the ADM Template array holding this element. For all user-
defined ADM objects, (e.g., where the Issuer Flag is set to
1) this value is as defined by the Issuing organization.
Parameters
The parameters field is represented as a Types Then Value
Collection (TTVC) as defined in Section 8.3.2. The overall
number of items in the collection represents the number of
parameters. The types of the TTVC represent the types of
each parameter, with the first listed type associated with
the first parameter, and so on. The values, if present,
represent the values of the parameters, with the first listed
value being the value of the first parameter, and so on.
Issuer
This is a binary identifier representing a predetermined
issuer name. The AMP protocol does not parse or validate
this identifier, using it only as a distinguishing bit
pattern to ensure uniqueness. This value, for example, may
come from a global registry of organizations, an issuing node
address, or some other network-unique marking. The issuer
field MUST NOT be present for any AId defined as part of an
ADM.
Tag
A value used to disambiguate multiple AIds with the same
Issuer. The definition of the tag is left to the discretion
of the Issuer. The Tag field MUST be present if the Tag Flag
is set in the flag byte and MUST NOT be present otherwise.
8.3. Collections
8.3.1. TNV Collection
A TNV Collection (TNVC) is a series of multiple TNV values. This is
simply encoded as a CBOR array with each element in the array
represented by the encoding of a TNV in accordance with Section 8.2.3
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8.3.2. Types Then Value Collection (TTVC)
A Types-Then-Value Collection (TTVC) provides a mechanism for
communicating a typed set of values by separating the types from the
values themselves. This construction is useful both for rapidly
performing type verification and for efficiently omitted type
information where appropriate.
Extracting type information to the "front" of the collection
optimizes the performance of type validators. A validator can
inspect the first array to ensure that element values match type
expectations. If type information were distributed throughout the
collection, as in the case with the TNVC, a type validator would need
to scan through the entire set of data to validate each type in the
collection. A TTVC SHOULD be used in lieu of a TNVC whenever type
validation must be performed.
In certain circumstances, a set of values can be communicated without
any type information when type information can be inferred from
context. In these circumstances, separating types from values allows
for an efficient way to omit type information when necessary.
The TTVC is encoded as a CBOR array with either one or two elements.
If the array has 1 element, then it MUST be a CBOR array of values.
If the TTVC array has 2 elements, then it MUST contain a CBOR byte
string of type information followed by a CBOR array of values. In
cases where both types and values are present, the number of types
MUST be the same as the number of elements as the array of values.
The order of types MUST correspond to the order of values in the
second array.
The E(TTVC) format is illustrated in Figure 8
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E(TTVC) Format
+---------+
| TTVC |
| [ARRAY] |
+----++---+
||
||
________/ \_________
/ \
+-----------+---------+
| Types | Values |
| [BYTESTR] | [ARRAY] |
| (opt) | |
+-----------+---------+
Figure 8
These fields are defined as follows.
Types
The Types field is encoded as a CBOR byte string with each
element of the array encoded as a byte. Each byte represents
a type and MUST match a type enumeration as defined in
[I-D.birrane-dtn-adm].
Values
The Values array is encoded as a CBOR array with each element
of the array encoded as a CBOR byte string containing the
CBOR encoding of the value, based on its type as required by
this specification.
8.3.3. AId Collections (AC)
An AId collection is an ordered collection of AId values. It is
encoded as a CBOR array with each element being an encoded AId, as
illustrated in Figure 9.
E(AC) Format
+--------------+-------+ +-------+
| Array Header | AID 1 | ... | AID N |
| [BYTES] | [AID] | | [AID] |
+--------------+-------+ +-------+
Figure 9
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8.3.4. Expressions (EXPR)
The Expression object encapsulates a typed postfix expression in
which each operator MUST be of type OP and each operand MUST be the
typed result of an operator or one of EDD, VAR, LIT, or CONST.
The Expression object is encoded as a CBOR byte array whose format is
illustrated in Figure 10.
E(AC) Format
+--------+------------+
| Type | Expression |
| [BYTE] | [AC] |
+--------+------------+
Figure 10
Type
The enumeration representing the type of the result of the
evaluated expression. This type MUST be defined in
[I-D.birrane-dtn-adm]. as a "Primitive Type".
Expression
An expression is represented in the AMP as an AId collection,
where each AId in the ordered collection represents either an
operand or operator in postfix form.
8.3.5. Predicate (PRED)
Predicates are Expressions whose values are interpreted as a Boolean.
The value of zero MUST be considered "false" and all other values
MUST be considered "true". Otherwise, Predicates are encoded and
treated the same as expressions.
8.4. ADM Object Definition Encodings
The autonomy model codified in [I-D.birrane-dtn-adm] comprises
multiple individual objects. This section describes the CBOR
encoding of these objects.
Note: The encoding of an object refers to the way in which the
complete object can be encoded such that the object as it exists on a
Manager may be re-created on an Agent, and vice-versa. In cases
where both a Manager and an Agent already have the definition of an
object, then only the encoded AId of the object needs to be
communicated. This is the case for all objects defined in a
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published ADM and any user-defined object that has been synchronized
between an Agent and Manager.
8.4.1. Externally Defined Data (EDD)
Externally defined data (EDD) are solely defined in the ADMs for
various applications and protocols. EDDs represent values that are
calculated external to an AMA Agent, such as values measured by
firmware.
The representation of these data is simply their identifying AIds.
The representation of an EDD is illustrated in Figure 11.
E(EDD) Format
+-------+
| ID |
| [AId] |
+-------+
Figure 11
ID
This is the AId identifying the EDD. Since EDDs are always
defined solely in the context of an ADM, this AId MUST NOT
have an ISSUER field and MUST NOT have a TAG field. This AId
MAY be defined with parameters.
8.4.2. Constants (CONST)
Unlike Literals, a Constant is an immutable, typed, named value.
Examples of constants include PI to some number of digits or the UNIX
Epoch.
Since ADM definitions are preconfigured on Agents and Managers in an
AMA, the type information for a given Constant is known by all actors
in the system and the encoding of the Constant needs to only be the
name of the constant as the Manager and Agent can derive the type and
value from the unique Constant name.
The format of a Constant is illustrated in Figure 12.
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E(CONST) Format
+-------+
| ID |
| [AId] |
+-------+
Figure 12
ID
This is the AId identifying the Constant. Since Constant
definitions are always provided in an ADM, this AId MUST NOT
have an ISSUER field and MUST NOT have a TAG field. The AId
MUST NOT have parameters.
8.4.3. Controls (CTRL)
A Control represents a pre-defined and optionally parameterized
opcode that can be run on an Agent. Controls in the AMP are always
defined in the context of an AMA; there is no concept of an operator-
defined Control. Since Controls are pre-configured in Agents and
Managers as part of ADM support, their representation is simply the
AId that identifies them, similar to EDDs.
The format of a Control is illustrated in Figure 13.
E(CTRL) Format
+-------+
| ID |
| [AId] |
+-------+
Figure 13
ID
This is the AId identifying the Control. This AId MUST NOT
have an ISSUER field and MUST NOT have a TAG field. This AId
MAY have parameters.
8.4.4. Macros (MAC)
Macros in the AMP are ordered collections of AId (an AC) that contain
Controls or other Macros. When run by an Agent, each AId in the AC
MUST be run in order.
Any AMP implementation MUST allow at least 4 levels of Macro nesting.
Implementations MUST prevent recursive nesting of Macros.
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The AId associated with a Macro MAY contain parameters. Each
parameter present in a Macro AId MUST contain type, name, and value
information. Any Control or Macro encapsulated within a
parameterized Macro MAY also contain parameters. If an encapsulated
object parameter contains only name information, then the parameter
value MUST be taken from the named parameter provided by the
encapsulating Macro. Otherwise, the value provided to the object
MUST be used instead.
The format of a Macro is illustrated in Figure 14.
E(MACRO) Format
+-------+------------+
| ID | Definition |
| [AId] | [AC] |
+-------+------------+
Figure 14
ID
This is the AId identifying the Macro. When a Macro is
defined in an ADM this AId MUST NOT have an ISSUER field and
MUST NOT have a TAG field. When the Macro is defined outside
of an ADM, the AId MUST have an ISSUER field and MAY have a
TAG field.
Definition
This is the ordered collection of AIds that identify the
Controls and other Macros that should be run as part of
running this Macro.
8.4.5. Operators (OP)
Operators are always defined in the context of an ADM. There is no
concept of a user-defined operator, as operators represent
mathematical functions implemented by the firmware on an Agent.
Since Operators are pre-configured in Agents and Managers as part of
ADM support, their representation is simply the AId that identifies
them.
The ADM definition of an Operator MUST specify how many parameters
are expected and the expected type of each parameter. For example,
the unary NOT Operator ("!") would accept one parameter. The binary
PLUS Operator ("+") would accept two parameters. A custom function
to calculate the average of the last 10 samples of a data item should
accept 10 parameters.
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Operators are always evaluated in the context of an Expression. The
encoding of an Operator is illustrated in Figure 15.
E(OP) Format
+-------+
| ID |
| [AId] |
+-------+
Figure 15
ID
This is the AId identifying the Operator. Since Operators
are always defined solely in the context of an ADM, this AId
MUST NOT have an ISSUER field and MUST NOT have a TAG field.
8.4.6. Report Templates (RPTT)
A Report Template is an ordered collection of identifiers that
describe the order and format of data in any Report Entry built in
compliance with the template. A template is a schema for a class of
reports. They contain no actual values and may be defined in a
formal ADM or configured by users in the context of a network
deployment.
A Report Template is modeled as an AC, as each data definition in the
template is identified by an AId.
E(RPTT) Format
+-----------------+
| Report Contents |
| [AC] |
+-----------------+
Figure 16
8.4.7. Report (RPT)
A Report is a set of data values populated using a given Report
Template. While Reports do not contain name information, they MAY
contain type information in cases where recipients wish to perform
type validation prior to interpreting the Report contents in the
context of a Report Template. Reports are "anonymous" in the sense
that any individual Report does not contain a unique identifier.
Reports can be differentiated by examining the combination of (1) the
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Report Template being populated, (2) the time at which the Report was
populated, and (3) the Agent producing the report.
A Report object is comprised of the identifier of the template used
to populate the report, an optional timestamp, and the contents of
the report. A Report is encoded as a CBOR array with either 2 or 3
elements. If the array has 2 elements then the optional Timestamp
MUST NOT be in the Report encoding. If the array has 3 elements then
the optional timestamp MUST be included in the Report encoding. The
Report encoding is illustrated in Figure 17.
E(RPT) Format
+----------+-----------+---------+
| Template | Timestamp | Entries |
| [AID] | [TS] | [TTVC] |
| | (opt) | |
+----------+-----------+---------+
Figure 17
Template
This is the AId identifying the template used to interpret
the data in this report.
This AId may be parameterized and, if so, the parameters MUST
include a name field and have been passed-by-name to the
template contents when constructing the report.
Timestamp
The timestamp marks the time at which the report was created.
This timestamp may be omitted in cases where the time of the
report generation can be inferred from other information.
For example, if a report is included in a message group such
that the timestamp of the message group is equivalent to the
timestamp of the report, the report timestamp may be omitted
and the timestamp of the included message group used instead.
Values
This is the collection of data values that comprise the
report contents in accordance with the associated Report
Template.
8.4.8. State-Based Rules (SRL)
A State-Based Rule (SRL) specifies that a particular action should be
taken by an Agent based on some evaluation of the internal state of
the Agent. A SRL specifies that starting at a particular START time
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an ACTION should be run by the Agent if some CONDITION evaluates to
true, until the ACTION has been run COUNT times. When the SRL is no
longer valid it may be discarded by the agent.
Examples of SRLs include:
Starting 2 hours from receipt, whenever V1 > 10, produce a Report
Entry for Report Template R1 no more than 20 times.
Starting at some future absolute time, whenever V2 != V4, run
Macro M1 no more than 36 times.
An SRL object is encoded as a CBOR array with 5 elements as
illustrated in Figure 18.
E(SRL) Format
+---------+
| SRL |
| [ARRAY] |
+---++----+
||
||
___________________/ \___________________
/ \
+-------+-------+--------+--------+--------+
| ID | START | COND | COUNT | ACTION |
| [AID] | [TS] | [PRED] | [UINT] | [AC] |
| | | | | |
+-------+-------+--------+--------+--------+
Figure 18
ID
This is the AId identifying the SRL. If this AId contains
parameters they MUST include a name in support of pass-by-
name to each element of the Action AC.
START
The time at which the SRL condition should start to be
evaluated. This will mark the first evaluation of the
condition associated with the SRL.
CONDITION
The Predicate which, if true, results in the SRL running the
associated action.
COUNT
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The number of times the SRL action can be run. The special
value of 0 indicates there is no limit on how many times the
action can be run.
ACTION
The collection of Controls and/or Macros to run as part of
the action. This is encoded as an AId Collection in
accordance with Section 8.3.3 with the stipulation that every
AId in this collection MUST represent either a Control or a
Macro.
8.4.9. Table Templates (TBLT)
A Table Template (TBLT) describes the types, and optionally names, of
the columns that define a Table.
The TBLT Object is encoded as a CBOR array that MUST contain either 2
or 3 elements. If the array is of size 2, then the column names
array MUST NOT be present in the encoding. If the array is of size 3
then the column names array MUST be present in the encoding. The
format of the TBLT Object Array is illustrated in Figure 19.
E(TBLT) Format
+---------+
| TBLT |
| [ARRAY] |
+---++----+
||
||
_____________/ \_____________
/ \
+-------+------------+---------+
| ID | Types | Names |
| [AID] | [BYTE STR] | [ARRAY] |
| | | (opt) |
+-------+------------+---------+
Figure 19
The elements of the TBLT array are defined as follows.
ID
This is the AId of the table template encoded in accordance
with Section 8.2.4.
Types
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The types field captures the data types of each column
comprising the table template. Each type is represented by
its enumeration as defined in [I-D.birrane-dtn-adm]. This
field is encoded as a CBOR byte string with the length of the
string equal to the number of columns in the template and
each column type enumeration encoded as a byte. The Nth byte
in the byte string represents the type of the Nth column.
Names
When present, column names are encoded as a CBOR array. This
array MUST have the same number of elements as bytes in the
Types byte string. Each element in the Names array is
encoded as a CBOR text string and represents the string
representation of the column name. The Nth text string in
the array represents the name of the Nth column.
8.4.10. Tables (TBL)
A Table object describes the series of values associated with a
Table Template.
A Table object is encoded as a CBOR array, with the first element of
the array identifying the Table Template and each subsequent element
identifying a row in the table. The format of the TBL Object Array
is illustrated in Figure 20.
E(TBL) Format
+---------+
| TBL |
| [ARRAY] |
+---++----+
||
||
______________/ \_______________
/ \
+---------+--------+ +--------+
| TBLT ID | Row 1 | | Row N |
| [AID] | [TTVC] | ... | [TTVC] |
+---------+--------+ +--------+
Figure 20
The TBL fields are defined as follows.
Template ID (TBLT ID)
This is the AId of the table template describing the format
of the table and is encoded in accordance with Section 8.2.4.
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Row
Each row of the table is represented as a series of values
with optional type information to aid in type checking table
contents to column types. Each row is encoded as a TTVC and
MAY include type information. AMP implementations should
consider the impact of including type information for every
row on the overall size of the encoded table.
Each TTVC representing a row MUST contain the same number of
elements as there are columns in the referenced
Table Template.
8.4.11. Time-Based Rules (TRL)
A Time-Based Rule (TRL) specifies that a particular action should be
taken by an Agent based on some time interval. A TRL specifies that
starting at a particular START time, and for every PERIOD seconds
thereafter, an ACTION should be run by the Agent until the ACTION has
been run for COUNT times. When the TRL is no longer valid it MAY BE
discarded by the Agent.
Examples of TRLs include:
Starting 2 hours from receipt, produce a Report Entry for Report
Template R1 every 10 hours ending after 20 times.
Starting at the given absolute time, run Macro M1 every 24 hours
ending after 365 times.
The TRL object is encoded as a CBOR array with 5 elements as
illustrated in Figure 21.
E(TRL) Format
+---------+
| TRL |
| [ARRAY] |
+---++----+
||
||
___________________/ \___________________
/ \
+-------+-------+--------+--------+--------+
| ID | START | PERIOD | COUNT | ACTION |
| [AID] | [TS] | [UINT] | [UINT] | [AC] |
+-------+-------+--------+--------+--------+
Figure 21
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ID
This is the AId identifying the TRL and is encoded in
accordance with Section 8.2.4. If this AId contains
parameters they MUST include a name in support of pass-by-
name to each element of the Action AC.
START
The time at which the TRL condition should start to be
evaluated.
PERIOD
The number of seconds to wait between running the action
associated with the TRL.
COUNT
The number of times the TRL action can be run. The special
value of 0 indicates there is no limit on how many times the
action can be run.
ACTION
The collection of Controls and/or Macros to run as part of
the action. This is encoded as an AId Collection in
accordance with Section 8.3.3 with the stipulation that every
AId in this collection MUST represent either a Control or a
Macro.
8.4.12. Variables (VAR)
Variable objects are transmitted in the AMP without the human-
readable description.
Variable objects are encoded as a CBOR byte string whose format is
illustrated in Figure 22.
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E(VAR) Format
+------------+
| Variable |
| [BYTE STR] |
+-----++-----+
||
||
______________/ \_____________
/ \
+-------+--------+-------------+
| ID | Type | Initializer |
| [AID] | [BYTE] | [EXPR] |
+-------+--------+-------------+
Figure 22
ID
This is the AId identifying the VAR and is encoded in
accordance with Section 8.2.4. This AId MUST NOT include
parameters.
Type
This field captures the data type of the Variable encoded as
a BYTE. This data type MUST be one of the data types defined
in [I-D.birrane-dtn-adm].
It is possible to specify a type different than the resultant
type of the initializing Expression. For example, if an
Expression adds two single-precision floating point numbers,
the VAR MAY have an integer type associated with it. In
cases where this is the case, numeric conversions MUST be
handled in accordance with [I-D.birrane-dtn-adm].
Initializer
The initial value of the Variable is calculated by an
Expression encoded in accordance with Section 8.3.4.
9. Functional Specification
This section describes the format of the messages that comprise the
AMP protocol.
9.1. AMP Message Summary
The AMP message specification is limited to three basic
communications:
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+------------+-------------+----------------------------------------+
| Message | Enumeration | Description |
+------------+-------------+----------------------------------------+
| Register | 0 | Add Agents to the list of managed |
| Agent | | devices known to a Manager. |
| | | |
| Report Set | 1 | Receiving a Report of one or more |
| | | Report Entries from an Agent. |
| | | |
| Perform | 2 | Sending a Macro of one or more |
| Control | | Controls to an Agent. |
+------------+-------------+----------------------------------------+
Table 5: ADM Message Type Enumerations
The entire management of a network can be performed using these three
messages and the configurations from associated ADMs.
9.2. Message Group Format
Individual messages within the AMP are combined into a single group
for communication with another AMP Actor. Messages within a group
MUST be received and applied as an atomic unit. The format of a
message group is illustrated in Figure 23. These message groups are
assumed communicated amongst Agents and Managers as the payloads of
encapsulating protocols which should provide additional security and
data integrity features as needed.
A message group is encoded as a CBOR array with at least 2 elements,
the first being the time the group was created followed by 1 or more
messages that comprise the group. The format of the message group is
illustrated in Figure 23.
AMP Message Group Format
+---------------+
| Message Group |
| [ARRAY] |
+------++-------+
||
____________________||_____________________
/ \
+-----------+------------+ +------------+
| Timestamp | Message 1 | ... | Message N |
| [TS] | [BYTE STR] | | [BYTE STR] |
+-----------+------------+ +------------+
Figure 23
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Timestamp
The creation time for this messaging group. This timestamp
MUST be an absolute time. Individual messages may have their
own creation timestamps based on their type, but the group
timestamp also serves as the default creation timestamp for
every message in the group. This is encoded in accordance
with Table 3.
Message N
The Nth message in the group.
9.3. Message Format
Each message identified in the AMP specification adheres to a common
message format, illustrated in Figure 24, consisting of a message
header, a message body, and an optional trailer.
Each message in the AMP is encode as a CBOR byte string formatted in
accordance with Figure 24.
AMP Message Format
+--------+----------+----------+
| Header | Body | Trailer |
| [BYTE] | [VARIES] | [VARIES] |
| | | (opt.) |
+--------+----------+----------+
Figure 24
Header
The message header BYTE is shown in Figure 25. The header
identifies a message context and opcode as well as flags that
control whether a Report Entry should be generated on message
success (Ack) and whether a Report Entry should be generated
on message failure (Nack).
AMP Common Message Header
+----------+-----+------+-----+----------+
| Reserved | ACL | Nack | Ack | Opcode |
+----------+-----+------+-----+----------+
| 7 6 | 5 | 4 | 3 | 2 1 0 |
+----------+-----+------+-----+----------+
MSB LSB
Figure 25
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Opcode
The opcode field identifies which AMP message is
being represented.
ACK Flag
The ACK flag describes whether successful application
of the message must generate an acknowledgement back
to the message sender. If this flag is set (1) then
the receiving actor MUST generate a Report Entry
communicating this status. Otherwise, the actor MAY
generate such a Report Entry based on other criteria.
NACK Flag
The NACK flag describes whether a failure applying
the message must generate an error notice back to the
message sender. If this flag is set (1) then the
receiving Actor MUST generate a Report Entry
communicating this status. Otherwise, the Actor MAY
generate such a Report Entry based on other criteria.
ACL Used Flag
The ACL used flag indicates whether the message has a
trailer associated with it that specifies the list of
AMP actors that may participate in the Actions or
definitions associated with the message. This area
is still under development.
Body
The message body contains the information associated with the
given message.
Trailer
An OPTIONAL access control list (ACL) may be appended as a
trailer to a message. When present, the ACL for a message
identifiers the agents and managers that can be affected by
the definitions and actions contained within the message.
The explicit impact of an ACL is described in the context of
each message below. When an ACL trailer is not present, the
message results may be visible to any AMP Actor in the
network, pursuant to other security protocol implementations.
9.4. Register Agent
The Register Agent message is used to inform an AMP Manager of the
presence of another Agent in the network.
The body of this message is the name of the new agent, encoded as
illustrated in Figure 26.
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Register Agent Message Body
+------------+
| Agent ID |
| [BYTE STR] |
+------------+
Figure 26
Agent ID
The Agent ID MUST represent the unique address of the Agent
in whatever protocol is used to communicate with the Agent.
9.5. Report Set
The Report Set message contains a set of 1 or more Reports produced
by an AMP Agent and sent to an AMP Manager.
The body of this message contains information on the recipient of the
reports followed by one or more Reports. The body is encoded as
illustrated in Figure 27.
Report Set Message Body
+----------+---------+ +---------+
| RX Names | ENTRY 1 | | ENTRY N |
| [ARRAY] | [RPT] | ... | [RPT] |
+----------+---------+ +---------+
Figure 27
RX Names
This field captures the set of Managers that have been sent
this report set. This is encoded as a CBOR array that MUST
have at least one entry. Each entry in this array is
encdoded as a CBOR text string.
ENTRY N
The Nth Report encoded in accordance with Section 8.4.7.
9.6. Perform Control
The perform control message causes the receiving AMP Actor to run one
or more pre-configured Controls provided in the message.
The body of this message is the start time for the controls followed
by the controls themselves, as illustrated in Figure 28.
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Perform Control Message Body
+-------+-----------+
| Start | Controls |
| [TS] | [AC] |
+-------+-----------+
Figure 28
Start
The time at which the Controls/Macros should be run.
Controls
The collection of AIds that represent the Controls and/or
Macros to be run by the AMP Actor. Every AId in this
collection MUST be either a Control or a Macro.
10. IANA Considerations
A Nickname registry needs to be established.
11. Security Considerations
Security within the AMP exists in two layers: transport layer
security and access control.
Transport-layer security addresses the questions of authentication,
integrity, and confidentiality associated with the transport of
messages between and amongst Managers and Agents. This security is
applied before any particular Actor in the system receives data and,
therefore, is outside of the scope of this document.
Finer grain application security is done via ACLs provided in the AMP
message headers.
12. References
12.1. Informative References
[I-D.birrane-dtn-ama]
Birrane, E., "Asynchronous Management Architecture",
draft-birrane-dtn-ama-06 (work in progress), October 2017.
12.2. Normative References
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[I-D.birrane-dtn-adm]
Birrane, E., DiPietro, E., and D. Linko, "AMA Application
Data Model", draft-birrane-dtn-adm-01 (work in progress),
March 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Appendix A. Acknowledgements
The following participants contributed technical material, use cases,
and useful thoughts on the overall approach to this protocol
specification: Jeremy Pierce-Mayer of INSYEN AG contributed the
concept of the typed data collection and early type checking in the
protocol.
Author's Address
Edward J. Birrane
Johns Hopkins Applied Physics Laboratory
Email: Edward.Birrane@jhuapl.edu
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