| 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
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.
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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.
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].
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 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.
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.
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].
The desirable properties of an asynchronous management protocol, as specified in the AMA, are summarized here to represent design constraints on the AMP specification.
+----------+----------+
| Field 1 | Field 2 |
| [TYPE 1] | [TYPE 2] |
| | (opt) |
+----------+----------+
Figure 1: Byte Field Formatting Example
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.
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.
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.
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.
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 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 |
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).
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 Size | Label | Comment |
|---|---|---|---|
| 0x1 - 0xCCC | 1-2 Bytes | Challenged Networks | Constraints imposed by physical layer and power. |
| 0xCCD - 0xCCCCCCC | 3-4 Bytes | Congested Networks | Constraints imposed by network traffic. |
| >=0xCCCCCCD | 5-8 Bytes | Resourced Networks | Generally unconstrained networks. |
This section describes the binary encoding of logical data constructs using the Concise Binary Object Representation (CBOR).
The following considerations act as guidance for CBOR encoders and decoders implementing the AMP.
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.
| AMP Type | CBOR Major Type | CBOR Additional Value | Comments |
|---|---|---|---|
| BYTE | 7 (Primitive) | 0-23 or 24 | BYTEs are simple values in CBOR. |
| INT | 0 (Positive), 1 (Negative) | 0-23,24,25,26 | INTs are encoded are positive or negative integers from (u)int8_t up to (u)int32_t. |
| UINT | 0 | 0-23, 24, 25, 26 | UINTs are positive integers from uint8_t up to uint32_t. |
| VAST | 0 (Positive), 1(Negative) | 27 | VASTs are encoding as (u)int64_t. |
| UVAST | 0 | 27 | VASTs are encoding as uint64_t. |
| REAL32 | 7 (Primitive) | 26 | Single-precision, 32-bit floating point value in IEEE-754 format. |
| REAL64 | 7 (Primitive) | 27 | Double-precision, 64-bit floating point value in IEEE-754 format. |
| STR | 3 (Text String) | Varies | Uses CBOR encoding unmodified. |
| BOOL | 7 (Primitive) | 0 or 1 | AV of 0 is considered FALSE. AV of 1 considered TRUE. |
| TS | 0 (Positive) | Varies | Timestamp in the smallest of uint8_t, uint16_t, uint32_t, or uint64_t. |
| BLOB | 2 (Byte String) | Varies | Uses CBOR encoding unmodifed |
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 Type | CBOR Major Type | CBOR Additional Value | Comments |
|---|---|---|---|
| TS | 7 (Primitive) | 0-23 or 24 | BYTEs are simple values in CBOR. |
+---------+
| TNV |
| [ARRAY] |
+----++---+
||
||
_______________________/ \_______________________
/ \
+--------------+------------+-----------+----------+
| Array Header | Flags/Type | Name | Value |
| [UINT] | [UINT] | [TXT STR] | [Varies] |
| | | (opt) | (opt) |
+--------------+------------+-----------+----------+
Figure 2: E(TNV) Format
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.
The E(TNV) fields are defined as follows.
E(TNV) Flag/Type Byte Format
+------+-------+-------------+
| Name | Value | Struct |
| Flag | Flag | Type |
+------+-------+-------------+
| 7 | 6 | 5 4 3 2 1 0 |
+------+-------+-------------+
MSB LSB
Figure 3
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.
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.
E(AId) Literal Flag Byte Format
+------------+-------------+
| VALUE TYPE | STRUCT TYPE |
+------------+---------+----
| 7 6 5 4 | 3 2 1 0 |
+------------+-------------+
MSB LSB
Figure 5
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.
E(AId) General Flag Byte Format
+----+------+-----+-----+-------------+
| NN | PARM | ISS | TAG | STRUCT TYPE |
+----+------+-----+-----+-------------+
| 7 | 6 | 5 | 4 | 3 2 1 0 |
+----+------+-----+-----+-------------+
MSB LSB
Figure 7
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
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
E(TTVC) Format
+---------+
| TTVC |
| [ARRAY] |
+----++---+
||
||
________/ \_________
/ \
+-----------+---------+
| Types | Values |
| [BYTESTR] | [ARRAY] |
| (opt) | |
+-----------+---------+
Figure 8
These fields are defined as follows.
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
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
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.
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 published ADM and any user-defined object that has been synchronized between an Agent and Manager.
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
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.
E(CONST) Format
+-------+
| ID |
| [AId] |
+-------+
Figure 12
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
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.
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
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.
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
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
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 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
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 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:
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
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.
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.
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:
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
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.
E(VAR) Format
+------------+
| Variable |
| [BYTE STR] |
+-----++-----+
||
||
______________/ \_____________
/ \
+-------+--------+-------------+
| ID | Type | Initializer |
| [AID] | [BYTE] | [EXPR] |
+-------+--------+-------------+
Figure 22
This section describes the format of the messages that comprise the AMP protocol.
The AMP message specification is limited to three basic communications:
| Message | Enumeration | Description |
|---|---|---|
| Register Agent | 0 | Add Agents to the list of managed devices known to a Manager. |
| Report Set | 1 | Receiving a Report of one or more Report Entries from an Agent. |
| Perform Control | 2 | Sending a Macro of one or more Controls to an Agent. |
The entire management of a network can be performed using these three messages and the configurations from associated ADMs.
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
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
AMP Common Message Header
+----------+-----+------+-----+----------+
| Reserved | ACL | Nack | Ack | Opcode |
+----------+-----+------+-----+----------+
| 7 6 | 5 | 4 | 3 | 2 1 0 |
+----------+-----+------+-----+----------+
MSB LSB
Figure 25
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.
Register Agent Message Body
+------------+
| Agent ID |
| [BYTE STR] |
+------------+
Figure 26
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
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.
Perform Control Message Body
+-------+-----------+
| Start | Controls |
| [TS] | [AC] |
+-------+-----------+
Figure 28
A Nickname registry needs to be established.
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.
| [I-D.birrane-dtn-ama] | Birrane, E., "Asynchronous Management Architecture", Internet-Draft draft-birrane-dtn-ama-06, October 2017. |
| [I-D.birrane-dtn-adm] | Birrane, E., DiPietro, E. and D. Linko, "AMA Application Data Model", Internet-Draft draft-birrane-dtn-adm-01, 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. |
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.