Internet DRAFT - draft-birrane-dtn-amp

draft-birrane-dtn-amp







Delay-Tolerant Networking                                     E. Birrane
Internet-Draft                  Johns Hopkins Applied Physics Laboratory
Intended status: Standards Track                            July 7, 2019
Expires: January 8, 2020


                    Asynchronous Management Protocol
                        draft-birrane-dtn-amp-07

Abstract

   This document describes a binary encoding of the Asynchronous
   Management Model (AMM) and a protocol for the exchange of these
   encoded items over a network.  This Asynchronous Management Protocol
   (AMP) does not require transport-layer sessions, operates over
   unidirectional links, and seeks to reduce the energy and compute
   power necessary for performing network management on resource
   constrained devices.

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
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   This Internet-Draft will expire on January 8, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   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 Compression  . . . . . . . . . . . . .   6
       7.1.2.  ADM Enumeration . . . . . . . . . . . . . . . . . . .   7
       7.1.3.  ADM Object Type 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 Type Encodings  . . . . . . . . . . . . . . . . . . .  10
       8.2.1.  Primitive Types . . . . . . . . . . . . . . . . . . .  10
       8.2.2.  Derived Types . . . . . . . . . . . . . . . . . . . .  11
       8.2.3.  Collections . . . . . . . . . . . . . . . . . . . . .  14
     8.3.  AMM Resource Identifier (ARI) . . . . . . . . . . . . . .  19
       8.3.1.  Encoding ARIs of Type LITERAL . . . . . . . . . . . .  19
       8.3.2.  Encoding Non-Literal ARIs . . . . . . . . . . . . . .  20
     8.4.  ADM Object Encodings  . . . . . . . . . . . . . . . . . .  23
       8.4.1.  Externally Defined Data (EDD) . . . . . . . . . . . .  23
       8.4.2.  Constants (CONST) . . . . . . . . . . . . . . . . . .  24
       8.4.3.  Controls (CTRL) . . . . . . . . . . . . . . . . . . .  24
       8.4.4.  Macros (MAC)  . . . . . . . . . . . . . . . . . . . .  25
       8.4.5.  Operators (OPER)  . . . . . . . . . . . . . . . . . .  26
       8.4.6.  Report Templates (RPTT) . . . . . . . . . . . . . . .  26
       8.4.7.  Report (RPT)  . . . . . . . . . . . . . . . . . . . .  27
       8.4.8.  State-Based Rules (SBR) . . . . . . . . . . . . . . .  28
       8.4.9.  Table Templates (TBLT)  . . . . . . . . . . . . . . .  30
       8.4.10. Tables (TBL)  . . . . . . . . . . . . . . . . . . . .  30
       8.4.11. Time-Based Rules (TBR)  . . . . . . . . . . . . . . .  31
       8.4.12. Variables (VAR) . . . . . . . . . . . . . . . . . . .  33
   9.  Functional Specification  . . . . . . . . . . . . . . . . . .  33
     9.1.  AMP Message Summary . . . . . . . . . . . . . . . . . . .  33
     9.2.  Message Group Format  . . . . . . . . . . . . . . . . . .  34
     9.3.  Message Format  . . . . . . . . . . . . . . . . . . . . .  35
     9.4.  Register Agent  . . . . . . . . . . . . . . . . . . . . .  37
     9.5.  Report Set  . . . . . . . . . . . . . . . . . . . . . . .  37



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     9.6.  Perform Control . . . . . . . . . . . . . . . . . . . . .  38
     9.7.  Table Set . . . . . . . . . . . . . . . . . . . . . . . .  38
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  39
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  39
   12. Implementation Notes  . . . . . . . . . . . . . . . . . . . .  39
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  39
     13.1.  Informative References . . . . . . . . . . . . . . . . .  40
     13.2.  Normative References . . . . . . . . . . . . . . . . . .  40
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  40
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  40

1.  Introduction

   Network management in challenged and resource constrained networks
   must be accomplished 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 binary encoding of AMM 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
   management of network layer protocols, it also uses these protocol
   stacks to encapsulate and communicate its own messages.





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   It is assumed that the protocols used to carry AMP messages provide
   addressing, confidentiality, integrity, security, fragmentation/
   reassembly, and other network 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 and 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 and is covered in [I-D.birrane-dtn-adm].

   This document does not address specific 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", "Table", "Constant",
   "Operator", "Time-Based Rule" and "State-Based Rule" are used without
   modification from the definitions provided in [I-D.birrane-dtn-ama].

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 unidirectional.  AMP Agents
      "push" data to Managers rather than Managers "pulling" data from
      Agents.

   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 en
      route in the network.  AMP minimizes message size wherever
      practical, to include binary data representations and predefined
      data definitions and templates.

   o  Absolute and Custom Data Identification - All data in the system
      must be uniquely addressable, to include operator-specified
      information.  AMP provides a compact encoding for identifiers.



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   o  Autonomous, Stateless Operation - There is no reliable concept of
      session establishment or round-trip data exchange in asynchronous
      networks.  AMP is designed to be stateless.  Where helpful, AMP
      provides mechanisms for transactional ordering of commands within
      a single AMP protocol data unit, but otherwise degrades gracefully
      when nodes in the network diver in their configuration.

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 AMP encodings 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  This specification uses the term OCTETS to refer to a sequence of
      one or more BYTE values.  There is no implied structure associated
      with OCTETS, meaning they do not encode a length value or utilize
      a terminator character.  While OCTETS may contain CBOR-encoded
      values, the OCTETS sequence itself is not encoded as a CBOR
      structure.

   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)".

   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



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      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 objects comprising the
   AMM.  As such, AMP defines very few structures of its own.  This
   section identifies those data structures that are unique to the AMP
   and required for it to perform appropriate and efficient encodings of
   AMM objects.

7.1.  Nicknames (NN)

   In the AMP, a "Nickname" (NN) is used to reduce the overall size of
   the encoding of ARIs that are defined in the context of an ADM.  A NN
   is calculated as a function of an ADM Moderated Namespace and the
   type of object being identified.

7.1.1.  Motivation for Compression

   As identifiers, ARIs are used heavily in AMM object definitions,
   particularly in those that define collections of objects.  This makes
   encoding ARIs an important consideration when trying to optimize the
   size of AMP message.

   Additionally, the majority of ARIs are defined in the context of an
   ADM.  Certain AMM objects types (EDDs, OPs, CTRLs, TBLTs) can only be
   defined in the context of an ADM.  Other object types (VARs, CONSTs,
   RPTTs) may have common, useful objects defined in an ADM as well.
   The structure of an ADM, to include its use of a Moderated Namespace



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   and collections by object type, provide a regular structure that can
   be exploited for creating a compact representation.

   In particular, as specified in [I-D.birrane-dtn-adm], ARIs can be
   grouped by (1) their namespace and (2) the type of AMM object being
   identified.  For example, consider the following ARIs of type EDD
   defined in ADM1 with a Moderated Namespace of "/DTN/ADM1/".

   ari:/DTN/ADM1/Edd.item_1 ari:/DTN/ADM1/Edd.item_2 ...  ari:/DTN/ADM1/
   Edd.item_1974

   In this case, the namespace (/DTN/ADM1/) and the object type (Edd)
   are good candidates for enumeration because their string encoding is
   very verbose and their information follows a regular structure shared
   across multiple ARIs.  Separately, the string representation of
   object names (item_1, item_2, etc...) may be very verbose and they
   are also candidates for enumeration as they occupy a particular ADM
   object type in a particular order as published in the ADM.

7.1.2.  ADM Enumeration

   Any ARI defined in an ADM exists in the context of a Moderated
   Namespace.  These namespaces provide a unique string name for the
   ADM.  However, ADMs can also be assigned a unique enumeration by the
   same moderating entities that ensure namespace uniqueness.

   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 and are assigned the special enumeration "0".  ARIs that
   are not defined in formal ADMs rely on other context information to
   help with their encoding (see Section 8.3).

7.1.3.  ADM Object Type Enumeration

   An ADM Object Type 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.




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                     +-----------------+-------------+
                     | AMM Object Type | Enumeration |
                     +-----------------+-------------+
                     |      CONST      |      0      |
                     |                 |             |
                     |       CTRL      |      1      |
                     |                 |             |
                     |       EDD       |      2      |
                     |                 |             |
                     |       MAC       |      3      |
                     |                 |             |
                     |       OPER      |      4      |
                     |                 |             |
                     |       RPTT      |      5      |
                     |                 |             |
                     |       SBR       |      6      |
                     |                 |             |
                     |       TBLT      |      7      |
                     |                 |             |
                     |       TBR       |      8      |
                     |                 |             |
                     |       VAR       |      9      |
                     |                 |             |
                     |     metadata    |      10     |
                     |                 |             |
                     |     reserved    |    11-19    |
                     +-----------------+-------------+

                      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 Object Type Enumeration)

   Considering the example set of ARIs from Section 7.1.1, assuming that
   ADM1 has ADM enumeration 9 and given that objects in the example were
   of type EDD, the NN for each of the 1974 items would be: (9 * 20) + 2
   = 182.  In this particular example, the ARI "/DTN/ADM1/Edd.item_1974"
   can be encoded in 5 bytes: two bytes to CBOR encode the nickname
   (182) and 3 bytes to CBOR encode the item's offset in the Edd
   collection (1974).






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7.1.5.  ADM Enumeration Considerations

   The assignment 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) defined in
   [RFC7049].

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  Because AMA objects are self-delineating they can be serialized
      into, or deserialized from, OCTETS.  CBOR containers such as
      BYTESTR and TXTSTR that encode length fields are only useful for
      data that is not self-delineating, such as name fields.  Encoding
      self-delineating objects into CBOR containers reduced efficiency
      as length fields would then be added to data that does not reqire
      a length field for processing.

   o  Encodings MUST result in smallest data representations.  There are
      several cases where the AMM defines types with less granularity
      than CBOR.  For example, AMM 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 AMM 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 Type Encodings

8.2.1.  Primitive Types

   The AMP encodes AMM primitive types as outlined in Table 3.


























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   +--------+-------------+--------------------------------------------+
   |  AMM   |  CBOR Major |                  Comments                  |
   |  Type  |     Type    |                                            |
   +--------+-------------+--------------------------------------------+
   |  BYTE  |   unsigned  | BYTEs are individually encoded as unsigned |
   |        | int or byte | integers unless the are defined as part of |
   |        |    string   |   a byte string, in which case they are    |
   |        |             |    encoded as a single byte in the byte    |
   |        |             |                  string.                   |
   |        |             |                                            |
   |  INT   |   unsigned  |  INTs are encoded as positive or negative  |
   |        |  integer or | integers from (u)int8_t up to (u)int32_t.  |
   |        |   negative  |                                            |
   |        |   integer   |                                            |
   |        |             |                                            |
   |  UINT  |   unsigned  |  UINTs are unsigned integers from uint8_t  |
   |        |   integer   |              up to uint32_t.               |
   |        |             |                                            |
   |  VAST  |   unsigned  | VASTs are encoding as positive or negative |
   |        |  integer or |         integers up to (u)int64_t.         |
   |        |   negative  |                                            |
   |        |   integer   |                                            |
   |        |             |                                            |
   | UVAST  |   unsigned  |     VASTs are unsigned integers up to      |
   |        |   integer   |                 uint64_t.                  |
   |        |             |                                            |
   | REAL32 |   floating  | Up to an IEEE-754 Single Precision Float.  |
   |        |    point    |                                            |
   |        |             |                                            |
   | REAL64 |   floating  | Up to an IEEE-754 Double Precision Float.  |
   |        |    point    |                                            |
   |        |             |                                            |
   | STRING | text string |       Uses CBOR encoding unmodified.       |
   |        |             |                                            |
   |  BOOL  |    Simple   |   0 is considered FALSE. 1 is considered   |
   |        |    Value    |                   TRUE.                    |
   +--------+-------------+--------------------------------------------+

                      Table 3: Standard Numeric Types

8.2.2.  Derived Types

   This section provides the CBOR encodings for AMM derived types.








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8.2.2.1.  Byte String Encoding

   The AMM derived type Byte String (BYTESTR) is encoded as a CBOR byte
   string.

8.2.2.2.  Time Values (TV) and Timestamps (TS)

   An TV is encoded as a UVAST.  Similarly, a TS is also encoded as a
   UVAST since a TS is simply an absolute TV.

   Rather than define two separate encodings for TVs (one for absolute
   TVs and one for relative TVs) a single, unambiguous encoding can be
   generated by defining a Relative Time Epoch (RTE) and interpreting
   the type of TV in relation to that epoch.  Time values less than the
   RTE MUST be interpreted as relative times.  Time values greater than
   or equal to the RTE MUST be interpreted as absolute time values.

   A relative TV is encoded as the number of seconds after an initiating
   event.  An absolute TV (and TS) is encoded as the number of seconds
   that have elapsed since 1 Jan 2000 00:00:00 (Unix Time 946684800).

   The RTE is defined as the timestamp value for September 9th, 2017
   (Unix time 1504915200).  Since TS values are the number of seconds
   since 1 Jan 2000 00:00:00, the RTE as a TS value is 1504915200 -
   946684800 = 558230400.

   The potential values of TV, and how they should be interpreted as
   relative or absolute is illustrated below.

                               Potential Time values
                 ________________________/\________________________
                /                                                  \
                      Relative Times            Absolute Times
                <------------------------><------------------------>
                     0 - 558,230,400          558,230,401 - 2^64

                |------------------------|-------------------------|
                |                        |
       00:00:00 1 Jan 2000      00:00:00 9 Sep 2017
       Unix Time 946684800      Unix Time 1504915200

   For example, a time value of "10" is a relative time representing 10
   seconds after an initiating event.  A time value of "600,000,000"
   refers to Saturday, 5 Jan, 2019 10:40:00.

   NOTE: Absolute and relative times are interchangeable.  An absolute
   time can be converted into a relative time by subtracting the current
   time from the absolute time.  A relative time can be converted into



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   an absolute time by adding to the relative time the timestamp of its
   relative event.  A pseudo-code example of converting a relative time
   to an absolute time is as follows, assuming that current-time is
   expressed in Unix Epoch time.

   IF (time_value <= 558230400) THEN
     absolute_time = (event_time - 946684800) + time_value
   ELSE
     absolute_time = time_value

8.2.2.3.  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 1,
   2, or 3 depending on the number of optional fields appearing in the
   encoding.  The E(TNV) format is illustrated in Figure 2.

                               +---------+
                               |   TNV   |
                               | [ARRAY] |
                               +----++---+
                                    ||
                                    ||
                    _______________/  \________________
                   /                                   \
                   +------------+-----------+----------+
                   | Flags/Type |    Name   |   Value  |
                   |   [BYTE]   | [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 |    Struct     |
                        | 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).

           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.  If there are 3 elements
           in the TNV array OR there are 2 elements in the array and the
           Name Flag is set, then this field MUST be present.
           Otherwise, this field MUST NOT be present.

   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.  If
           there are 3 elements in the TNV array OR there are 2 elements
           in the array and the Name Flag is not set, then this field
           MUST be present.  Otherwise, this field MUST NOT be present.

8.2.3.  Collections

8.2.3.1.  Type-Name-Value Collection (TNVC)

   A TNV Collection (TNVC) is an ordered set of TNVs with special
   semantics for more efficiently encoding sets of TNVs with identical
   attributes.





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   A TNV, defined in Section 8.2.2.3, consists of three distinct
   components: a type, a name, and a value.  When all of the TNVs in the
   TNVC have the same format (such as they all include type information)
   then the encoding of the TNVC can use this information to save
   encoding space and make processing more efficient.  In cases when all
   TNVs have the same format, the types (if present), names (if
   present), and values (if present) are separated into their own arrays
   for individual processing with type information (if present) always
   appearing first.

   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 TNVC is encoded as a sequence of at least 1 octet, where the single
   required octet includes the flag BYTE representing the optional
   portions of the collection that are present.  If the flag BYTE
   indicates an empty collection there will be no following octets.The
   format of a TNVC is illustrated in Figure 4.

                             +----------+
                             |   TNVC   |
                             | [OCTETS] |
                             +----++----+
                                  ||
                                  ||
      ____________________________/  \_____________________________
     /                                                             \
     +--------+---------+----------+----------+----------+----------+
     | Flags  | # Items |  Types   |  Names   |  Values  |  Mixed   |
     | [BYTE] |  [UINT] | [OCTETS] | [OCTETS] | [OCTETS] | [OCTETS] |
     |        |  (Opt)  |  (Opt)   |  (Opt)   |  (Opt)   |  (Opt)   |
     +--------+---------+----------+----------+----------+----------+

                         Figure 4: E(TNVC) Format

   The E(TNVC) fields are defined as follows.

   Flags
           The first byte of the E(TNVC) describes which optional
           portions of a TNV will be present for each TNV in the
           collection.





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           If all non-reserved flags have the value 0 then the TNVC
           represents an empty collection, in which case no other
           information is provided for the E(TNVC).
           The layout of this byte is illustrated in Figure 5.

                          E(TNV) Flag Byte Format

                 +----------+------+------+------+------+
                 | Reserved | Mix  | Type | Name | Val  |
                 |  Flags   | Flag | Flag | Flag | Flag |
                 +----------+------+------+------+------+
                 |    7-4   |   3  |   2  |   1  |   0  |
                 +----------+------+------+------+------+
                 MSB                              LSB

                                 Figure 5

           Mixed Flag
                   This flag indicates that the set of TNVs in the
                   collection do not all share the same properties and,
                   therefore, the collection is a mix of different types
                   of TNV.  When set to 1 the E(TNVC) MUST contain the
                   Mixed Values field and all other flags in this byte
                   MUST be set to 0.  When set to 0 the E(TNVC) MUST NOT
                   contain the Mixed Values field.

           Type Flag
                   This flag indicates whether each TNV in the
                   collection has type information associated with it.
                   When set to 1 the E(TNVC) MUST contain type
                   information for each TNV.  When set to 0, type
                   information MUST NOT be present.

           Name Flag
                   This flag indicates whether each TNV in the
                   collection has name information associated with it.
                   When set to 1 the E(TNVC) MUST contain name
                   information for each TNV.  When set to 0, name
                   information MUST NOT be present.

           Value Flag
                   This flag indicates whether each TNV in the
                   collection has value information associated with it.
                   When set to 1 the E(TNVC) MUST contain value
                   information for each TNV.  When set to 0, value
                   information MUST NOT be present.

   # Items



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           The number of items field lists the number of items that are
           contained in the TNVC.  Each of the types, names, and values
           sequences (if present) MUST have exactly this number of
           entries in them.  This field MUST be present in the E(TNVC)
           when any one of the non-reserved bits of the Flag Byte are
           set to 1.

   Types
           The types field is encoded as an OCTETS sequence where the
           Nth byte in the sequence represents the type for the Nth TNV
           in the collection.  This field MUST be present in the E(TNVC)
           when the Type Flag is set to 1 and MUST NOT be present
           otherwise.  If present, this field MUST contain exactly the
           same number of types as number of items in the TNVX.

   Names
           The names field is encoded as an OCTETS sequence containing
           the names of the TNVs in the collection.  Each name is
           encoded as a CBOR string, with the Nth CBOR string
           representing the name of the Nth TNV in the collection.  This
           field MUST be present in the E(TNVC) when the Names Flag is
           set to 1 and MUST NOT be present otherwise.  If present, this
           field MUST contain exactly the same number of CBOR strings as
           number of items in the TNVC.

   Values
           The values field is encoded as an OCTETS sequence containing
           the values of TNVs in the collection.
           If the Type Flag is set to 1 then each entry will be encoded
           in accordance with the corresponding index in the type field.
           For example, the 1st value will be encoded using the encoding
           rules for the first byte in the type OCTETS sequence.
           If the Type Flag is set to 0 then the values will be encoded
           as native CBOR types.  CBOR types do not have a one-to-one
           mapping with AMP types and it is the responsibility of the
           transmitting AMP actor and the receiving AMP actor to
           determine how to map these to AMP types.  This field MUST be
           present in the E(TNVC) when the Value Flag is set to 1 and
           MUST NOT be present otherwise.  If present, this field MUST
           contain exactly the same number of values as number of items
           in the TNVC.

   Mixed
           The mixed field is encoded as an OCTETS sequence containing a
           series of E(TNV) objects.  This field MUST be present when
           the Mixed Flag is set to 1 and MUST NOT be present otherwise.
           If present, this field MUST contain exactly the same number
           of E(TNV) objects as numnber of items in the TNVC.



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8.2.3.2.  ARI Collections (AC)

   An ARI collection is an ordered collection of ARI values.  It is
   encoded as a CBOR array with each element being an encoded ARI, as
   illustrated in Figure 6.

                               E(AC) Format

                               +---------+
                               |    AC   |
                               | [ARRAY] |
                               +----++---+
                                    ||
                                    ||
                           ________/  \_________
                          /                     \
                          +-------+     +-------+
                          | ARI 1 | ... | ARI N |
                          | [ARI] |     | [ARI] |
                          +-------+     +-------+

                                 Figure 6

8.2.3.3.  Expressions (EXPR)

   The Expression object encapsulates a typed postfix expression in
   which each operator MUST be of type OPER 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 an OCTETS sequence whose format
   is illustrated in Figure 7.

                              E(EXPR) Format

                              +----------+
                              |   EXPR   |
                              | [OCTETS] |
                              +-----++---+
                                    ||
                                    ||
                          _________/  \_________
                         /                      \
                         +---------+------------+
                         |   Type  | Expression |
                         |  [BYTE] |    [AC]    |
                         +---------+------------+

                                 Figure 7



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   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 ARI collection,
           where each ARI in the ordered collection represents either an
           operand or operator in postfix form.

8.3.  AMM Resource Identifier (ARI)

   The ARI, as defined in [I-D.birrane-dtn-adm], identifies an AMM
   object.  There are two kinds of objects that can be identified in
   this scheme: literal objects (of type LIT) and all other objects.

8.3.1.  Encoding ARIs of Type LITERAL

   A literal identifier is one that is literally defined by its value,
   such as numbers (0, 3.14) and strings ("example").  ARIs of type
   LITERAL do not have issuers or nicknames or parameters.  They are
   simply typed basic values.

   The E(ARI) of a LIT object is encoded as an OCTETS sequence and
   consists of a mandatory flag BYTE and the value of the LIT.

   The E(ARI) structure for LIT types is illustrated in Figure 8.

                           E(ARI) Literal Format

                           +--------+----------+
                           | Flags  |  Value   |
                           | [BYTE] | [VARIES] |
                           +--------+----------+

                                 Figure 8

   These fields are defined as follows.

   Flags
           The Flags byte identifies the object as being of type LIT and
           also captures the primitive type of the following value.  The
           layout of this byte is illustrated in Figure 9.








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                      E(ARI) Literal Flag Byte Format

                    +-------------------+-------------+
                    | VALUE TYPE OFFSET | STRUCT TYPE |
                    +-------------------+-------------|
                    |   7   6   5   4   | 3  2  1  0  |
                    +-------------------+-------------+
                     MSB                           LSB

                                 Figure 9

           Value Type Offset
                   The high nibble of the flag byte contains the offset
                   into the Primitive Types enumeration defined in
                   [I-D.birrane-dtn-adm].  An offset of 0 represents the
                   first defined Primitive Type.  An offset of 1
                   represents the second defined Primitive Type, and so
                   on.  An offset into the data types field is used to
                   ensure that they type value fits into a nibble.

           Structure Type
                   The lower nibble of the flag byte identifies the type
                   of AMM Object being identified by the ARI.  In this
                   instance, this value MUST be LIT, 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.

8.3.2.  Encoding Non-Literal ARIs

   All other ARIs are defined in the context of AMM objects and may
   contain parameters and other meta-data.  The AMP, as a machine-to-
   machine binary encoding of this information removes human-readable
   information such as Name and Description from the E(ARI).
   Additionally, this encoding adds other information to improve the
   efficiency of the encoding, such as the concept of Nicknames, defined
   in Section 7.1.

   The E(ARI) is encoded as an OCTETS sequence and consists of a
   mandatory flag byte, an encoded object name, and optional annotations
   to assist with filtering, access control, and parameterization.  The
   E(ARI) structure is illustrated in Figure 10.





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                           E(ARI) General Format

     +--------+---------+-----------+---------+---------+-----------+
     | Flags  |   NN    |   Name    |  Parms  |  Issuer |    Tag    |
     | [BYTE] | [UVAST] | [BYTESTR] | [TNVC]  | [UVAST] | [BYTESTR] |
     |        |  (opt)  |           |  (opt)  |  (opt)  |    opt)   |
     +--------+---------+-----------+---------+---------+-----------+

                                 Figure 10

   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 11.

                      E(ARI) General Flag Byte Format

                  +----+------+-----+-----+-------------+
                  | NN | PARM | ISS | TAG | STRUCT TYPE |
                  +----+------+-----+-----+-------------+
                  | 7  |  6   |  5  |  4  | 3  2  1  0  |
                  +----+------+-----+-----+-------------+
                  MSB                               LSB

                                 Figure 11

           Nickname (NN)
                   This flag indicates that ADM compression is used for
                   this E(ARI).  When set to 1 the Nickname field MUST
                   be present in the E(ARI).  When set to 0 the Nickname
                   field MUST NOT be present in the E(ARI).  When an ARI
                   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(ARI).

           Parameters Present (PARM)
                   This flag indicates that this ARI can be
                   parameterized and that parameter information is
                   included in the E(ARI).  When set to 1 the Parms
                   field MUST be present in the E(ARI).  When set to 0
                   the Parms field MUST NOT be present in the E(ARI).

           Issuer Present (ISS)




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                   This flag indicates that this ARI is defined in the
                   context of a specific issuing entity.  When set to 1
                   the Issuer field MUST be present in the E(ARI).  When
                   set to 0 the Issuer field MUST NOT be present in the
                   E(ARI).

           Tag Present (TAG)
                   This flag indicates that the ARI 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(ARI).  When set to 0 the Tag field MUST NOT be
                   present in the E(ARI).  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(ARI) flag byte identifies
                   the kind of structure being identified.  This field
                   MUST contain one of the AMM object types defined in
                   [I-D.birrane-dtn-adm].

   Nickname (NN)
           This optional field contains the Nickname as calculated
           according to Section 7.1.

   Object Name
           This mandatory field contains an encoding 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 collection 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 Type Name Value
           Collection (TNVC) as defined in Section 8.2.3.1.  The overall
           number of items in the collection represents the number of
           parameters.  The types of the TNVC 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



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           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 ARI defined in an ADM.

   Tag
           A value used to disambiguate multiple ARIs 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.

8.4.  ADM Object 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 ARI 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.

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 ARIs.
   The representation of an EDD is illustrated in Figure 12.

                               E(EDD) Format

                                 +-------+
                                 |  ID   |
                                 | [ARI] |
                                 +-------+

                                 Figure 12

   ID
           This is the ARI identifying the EDD.  Since EDDs are always
           defined solely in the context of an ADM, this ARI MUST NOT




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           have an ISSUER field and MUST NOT have a TAG field.  This ARI
           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 13.

                              E(CONST) Format

                                 +-------+
                                 |  ID   |
                                 | [ARI] |
                                 +-------+

                                 Figure 13

   ID
           This is the ARI identifying the Constant.  Since Constant
           definitions are always provided in an ADM, this ARI MUST NOT
           have an ISSUER field and MUST NOT have a TAG field.  The ARI
           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 the ARI that
   identifies them, similar to EDDs.

   The format of a Control is illustrated in Figure 14.









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                              E(CTRL) Format

                                 +-------+
                                 |  ID   |
                                 | [ARI] |
                                 +-------+

                                 Figure 14

   ID
           This is the ARI identifying the Control.  This ARI MUST NOT
           have an ISSUER field and MUST NOT have a TAG field.  This ARI
           may have parameters.

8.4.4.  Macros (MAC)

   Macros in the AMP are ordered collections of ARIs (an AC) that
   contain Controls or other Macros.  When run by an Agent, each ARI 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 ARI associated with a Macro MAY contain parameters.  Each
   parameter present in a Macro ARI 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 15.

                               E(MAC) Format

                          +-------+------------+
                          |  ID   | Definition |
                          | [ARI] |    [AC]    |
                          +-------+------------+

                                 Figure 15

   ID
           This is the ARI identifying the Macro.  When a Macro is
           defined in an ADM this ARI MUST NOT have an ISSUER field and
           MUST NOT have a TAG field.  When the Macro is defined outside




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           of an ADM, the ARI MUST have an ISSUER field and MAY have a
           TAG field.

   Definition
           This is the ordered collection of ARIs that identify the
           Controls and other Macros that should be run as part of
           running this Macro.

8.4.5.  Operators (OPER)

   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 preconfigured in Agents and Managers as part of
   ADM support, their representation is simply the ARI 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 16.

                               E(OP) Format

                                 +-------+
                                 |  ID   |
                                 | [ARI] |
                                 +-------+

                                 Figure 16

   ID
           This is the ARI identifying the Operator.  Since Operators
           are always defined solely in the context of an ADM, this ARI
           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 built in
   compliance with the template.  A template is a schema for a class of
   reports.  It contains no actual values and may be defined in a formal
   ADM or configured by users in the context of a network deployment.



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   The encoding of a RPTT is illustrated in Figure 17.

                              E(RPTT) Format

                           +-------+----------+
                           |  ID   | Contents |
                           | [ARI] |   [AC]   |
                           +-------+----------+

                                 Figure 17

   ID
           This is the ARI identifying the report template.

   Contents
           This is the ordered collection of ARIs that define the
           template.

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
   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 18.














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                               E(RPT) Format

                                +---------+
                                |   RPT   |
                                | [ARRAY] |
                                +---++----+
                                    ||
                                    ||
                      _____________/  \_____________
                     /                              \
                    +----------+-----------+---------+
                    | Template | Timestamp | Entries |
                    |   [ARI]  |   [TS]    | [TNVC]  |
                    |          |   (opt)   |         |
                    +----------+-----------+---------+

                                 Figure 18

   Template
           This is the ARI identifying the template used to interpret
           the data in this report.

           This ARI 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.

   Entries
           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 (SBR)

   A State-Based Rule (SBR) specifies that a particular action should be
   taken by an Agent based on some evaluation of the internal state of
   the Agent.  A SBR 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 SBR is no
   longer valid it may be discarded by the agent.



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   Examples of SBRs include:

      Starting 2 hours from receipt, whenever V1 > 10, produce a Report
      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 SBR object is encoded as an OCTETS sequence as illustrated in
   Figure 19.

                               E(SBR) Format

                              +----------+
                              |    SBR   |
                              | [OCTETS] |
                              +----++----+
                                   ||
                                   ||
           _______________________/  \_______________________
           /                                                  \
           +-------+-------+--------+--------+--------+--------+
           |  ID   | START |  COND  | EVALS  | FIRES  | ACTION |
           | [ARI] | [TV]  | [EXPR] | [UINT] | [UINT] |  [AC]  |
           +-------+-------+--------+--------+--------+--------+

                                 Figure 19

   ID
           This is the ARI identifying the SBR.  If this ARI 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 SBR condition should start to be
           evaluated.  This will mark the first evaluation of the
           condition associated with the SBR.

   CONDITION
           The Expression which, if true, results in the SBR running the
           associated action.  An EXPR is considered true if it
           evaluates to a non-zero value.

   EVALS
           The number of times the SBR condition can be evaluated.  The
           special value of 0 indicates there is no limit on how many
           times the condition can be evaluated.




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   FIRES
           The number of times the SBR 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 AC in accordance with
           Section 8.2.3.2 with the stipulation that every ARI in this
           collection MUST be of type CTRL or MAC.

8.4.9.  Table Templates (TBLT)

   A Table Template (TBLT) describes the types, and optionally names, of
   the columns that define a Table.

   Because TBLTs are only defined in the context of an ADM, their
   definition cannot change operationally.  Therefore, a TBLT is encoded
   simply as the ARI for the template.  The format of the TBLT Object
   Array is illustrated in Figure 20.

                              E(TBLT) Format

                                 +-------+
                                 |  ID   |
                                 | [ARI] |
                                 +-------+


                                 Figure 20

   The elements of the TBLT array are defined as follows.

   ID
           This is the ARI of the table template encoded in accordance
           with Section 8.3.

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 21.





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                               E(TBL) Format

                                +---------+
                                |   TBL   |
                                | [ARRAY] |
                                +---++----+
                                    ||
                                    ||
                    ______________/  \_______________
                    /                                 \
                    +---------+--------+     +--------+
                    | TBLT ID |  Row 1 |     |  Row N |
                    |  [ARI]  | [TNVC] | ... | [TNVC] |
                    +---------+--------+     +--------+

                                 Figure 21

   The TBL fields are defined as follows.

   Template ID (TBLT ID)
           This is the ARI of the table template describing the format
           of the table and is encoded in accordance with Section 8.3.

   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 TNVC 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 TNVC 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 (TBR)

   A Time-Based Rule (TBR) specifies that a particular action should be
   taken by an Agent based on some time interval.  A TBR 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 TBR is no longer valid it MAY BE
   discarded by the Agent.

   Examples of TBRs include:

      Starting 2 hours from receipt, produce a Report for Report
      Template R1 every 10 hours ending after 20 times.




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      Starting at the given absolute time, run Macro M1 every 24 hours
      ending after 365 times.

   The TBR object is encoded as an OCTETS sequence as illustrated in
   Figure 22.

                               E(TBR) Format

                               +----------+
                               |    TBR   |
                               | [OCTETS] |
                               +----++----+
                                    ||
                                    ||
                ___________________/  \___________________
               /                                          \
               +-------+-------+--------+--------+--------+
               |  ID   | START | PERIOD | COUNT  | ACTION |
               | [ARI] | [TV]  | [UINT] | [UINT] |  [AC]  |
               +-------+-------+--------+--------+--------+

                                 Figure 22

   ID
           This is the ARI identifying the TBR and is encoded in
           accordance with Section 8.3.  If this ARI 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 TBR condition should start to be
           evaluated.

   PERIOD
           The number of seconds to wait between running the action
           associated with the TBR.

   COUNT
           The number of times the TBR 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 ARI Collection in
           accordance with Section 8.2.3.2 with the stipulation that
           every ARI in this collection MUST represent either a Control
           or a Macro.



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8.4.12.  Variables (VAR)

   Variable objects are transmitted in the AMP without the human-
   readable description.

   Variable objects are encoded as an OCTETS sequence whose format is
   illustrated in Figure 23.

                               E(VAR) Format

                               +-----------+
                               |  Variable |
                               |  [OCTETS] |
                               +-----++----+
                                     ||
                                     ||
                              ______/  \_____
                             /               \
                             +-------+-------+
                             |  ID   | Value |
                             | [ARI] | [TNV] |
                             +-------+-------+

                                 Figure 23

   ID
           This is the ARI identifying the VAR and is encoded in
           accordance with Section 8.3.  This ARI MUST NOT include
           parameters.

   Value
           This field captures the value (and optionally the type and
           name) of the variable, encoded as a TNV.

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 Set  | 3           | Receiving one or more tables from an   |
   |            |             | Agent.                                 |
   +------------+-------------+----------------------------------------+

                  Table 4: 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 24.  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 24.
















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                         AMP Message Group Format

                              +---------------+
                              | Message Group |
                              |    [ARRAY]    |
                              +------++-------+
                                     ||
                 ____________________||___________________
                /                                         \
                +-----------+-----------+     +-----------+
                | Timestamp | Message 1 | ... | Message N |
                |    [TS]   |  [OCTETS] |     |  [OCTETS] |
                +-----------+-----------+     +-----------+

                                 Figure 24

   Timestamp
           The creation time for this messaging group.  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 25, consisting of a message
   header, a message body, and an optional trailer.

   Each message in the AMP is encode as an OCTETS sequence formatted in
   accordance with Figure 25.

                            AMP Message Format

                     +--------+----------+----------+
                     | Header |   Body   | Trailer  |
                     | [BYTE] | [VARIES] | [VARIES] |
                     |        |          |  (opt.)  |
                     +--------+----------+----------+

                                 Figure 25

   Header
           The message header BYTE is shown in Figure 26.  The header
           identifies a message context and opcode as well as flags that



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           control whether a Report should be generated on message
           success (Ack) and whether a Report 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 26

           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 acknowledgment back
                   to the message sender.  If this flag is set (1) then
                   the receiving actor MUST generate a Report
                   communicating this status.  Otherwise, the actor MAY
                   generate such a Report 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 communicating
                   this status.  Otherwise, the Actor MAY generate such
                   a Report 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




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           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 27.

                        Register Agent Message Body

                               +-----------+
                               |  Agent ID |
                               | [BYTESTR] |
                               +-----------+

                                 Figure 27

   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 28.

                          Report Set Message Body

                   +----------+--------+     +--------+
                   | RX Names |  RPT 1 |     |  RPT N |
                   |  [ARRAY] |  [RPT] | ... |  [RPT] |
                   +----------+--------+     +--------+

                                 Figure 28




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   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.

   RPT 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 preconfigured 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 29.

                       Perform Control Message Body

                           +-------+-----------+
                           | Start |  Controls |
                           |  [TV] |    [AC]   |
                           +-------+-----------+

                                 Figure 29

   Start
           The time at which the Controls/Macros should be run.

   Controls
           The collection of ARIs that represent the Controls and/or
           Macros to be run by the AMP Actor.  Every ARI in this
           collection MUST be either a Control or a Macro.

9.7.  Table Set

   The Table Set message contains a set of 1 or more TBLs produced by an
   AMP Agent and sent to an AMP Manager.

   The body of this message contains information on the recipient of the
   tables followed by one or more TBLs.  The body is encoded as
   illustrated in Figure 30.









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                          Table Set Message Body

                   +----------+--------+     +--------+
                   | RX Names |  TBL 1 |     |  TBL N |
                   |  [ARRAY] |  [TBL] | ... |  [TBL] |
                   +----------+--------+     +--------+

                                 Figure 30

   RX Names
           This field captures the set of Managers that have been sent
           this table 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.

   TBL N
           The Nth Table encoded in accordance with Section 8.4.10.

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.  Implementation Notes

   A reference implementation of this version of the AMP specification
   is available in the 3.6.2 release of the ION open source code base
   available from sourceforge at https://sourceforge.net/projects/ion-
   dtn/.

13.  References







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13.1.  Informative References

   [I-D.birrane-dtn-ama]
              Birrane, E., "Asynchronous Management Architecture",
              draft-birrane-dtn-ama-07 (work in progress), June 2018.

13.2.  Normative References

   [I-D.birrane-dtn-adm]
              Birrane, E., DiPietro, E., and D. Linko, "AMA Application
              Data Model", draft-birrane-dtn-adm-02 (work in progress),
              June 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>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

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.  David Linko and Evana DiPietro of the Johns Hopkins
   University Applied Physics Laboratory contributed appreciated review
   and type checking of various elements of this specification.

Author's Address

   Edward J. Birrane
   Johns Hopkins Applied Physics Laboratory

   Email: Edward.Birrane@jhuapl.edu













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