Delay-Tolerant Networking E. Birrane
Internet-Draft Johns Hopkins Applied Physics Laboratory
Intended status: Experimental J. Mayer
Expires: December 28, 2016 INSYEN AG
June 26, 2016
Asynchronous Management Protocol
draft-birrane-dtn-amp-03
Abstract
This document describes an Asynchronous Management Protocol (AMP) in
conformance with the Asynchronous Management Architecture (AMA). The
AMP provides monitoring and configuration services between managing
devices (Managers) and managed devices (Agents), some of which may
operate on the far side of high-delay or high-disruption links. The
AMP reduces the number of transmitted bytes, operates without
sessions or (concurrent) two-way links, and functions autonomously
when there is no timely contact with a network operator. The AMP
accomplishes this without requiring mobile code.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 28, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Technical Notes . . . . . . . . . . . . . . . . . . . . . 4
1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1. Protocol Scope . . . . . . . . . . . . . . . . . . . 5
1.3.2. Specification Scope . . . . . . . . . . . . . . . . . 5
1.4. Requirements Language . . . . . . . . . . . . . . . . . . 6
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Primitive Types . . . . . . . . . . . . . . . . . . . . . 6
3.1.1. Standard Numeric Types . . . . . . . . . . . . . . . 7
3.1.2. Self-Delimiting Numeric Value (SDNV) . . . . . . . . 7
3.1.3. Timestamp (TS) . . . . . . . . . . . . . . . . . . . 8
3.2. Compound Types . . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Binary Large Object (BLOB) . . . . . . . . . . . . . 8
3.2.2. Data Collection (DC) . . . . . . . . . . . . . . . . 9
3.2.3. Typed Data Collection (TDC) . . . . . . . . . . . . . 9
3.2.4. Table (TBL) . . . . . . . . . . . . . . . . . . . . . 11
3.3. Managed Identifiers (MIDs) . . . . . . . . . . . . . . . 12
3.4. Nicknames . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5. Parameters . . . . . . . . . . . . . . . . . . . . . . . 17
3.5.1. Optional Parameters . . . . . . . . . . . . . . . . . 17
3.5.2. Parameter Evaluation . . . . . . . . . . . . . . . . 17
3.6. Special Types . . . . . . . . . . . . . . . . . . . . . . 19
3.6.1. MID Collections (MC) . . . . . . . . . . . . . . . . 19
3.6.2. Expressions (EXPR) . . . . . . . . . . . . . . . . . 19
3.6.3. Predicate (PRED) . . . . . . . . . . . . . . . . . . 19
4. AMP Structures . . . . . . . . . . . . . . . . . . . . . . . 20
4.1. AMA Overview . . . . . . . . . . . . . . . . . . . . . . 20
4.2. Externally Defined Data (EDD) . . . . . . . . . . . . . . 21
4.3. Variables (VAR) . . . . . . . . . . . . . . . . . . . . . 22
4.4. Report Template (RPTT), Report Entry (RPTE) . . . . . . . 23
4.5. Control . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.6. Time-Based Rule (TRL) . . . . . . . . . . . . . . . . . . 27
4.7. State-Based Rule (SRL) . . . . . . . . . . . . . . . . . 28
4.8. Macro . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.9. Literal . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.10. Operator . . . . . . . . . . . . . . . . . . . . . . . . 32
5. Data Type IDs and Enumerations . . . . . . . . . . . . . . . 33
5.1. Numeric Promotions . . . . . . . . . . . . . . . . . . . 35
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5.2. Numeric Conversions . . . . . . . . . . . . . . . . . . . 36
6. Application Data Model Template . . . . . . . . . . . . . . . 36
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2. Template . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2.1. ADM Metadata . . . . . . . . . . . . . . . . . . . . 36
6.2.2. ADM Information Capture . . . . . . . . . . . . . . . 37
6.3. The Agent ADM . . . . . . . . . . . . . . . . . . . . . . 38
7. Functional Specification . . . . . . . . . . . . . . . . . . 38
7.1. Message Group Format . . . . . . . . . . . . . . . . . . 39
7.2. Message Format . . . . . . . . . . . . . . . . . . . . . 39
7.3. Register Agent (0x00) . . . . . . . . . . . . . . . . . . 41
7.4. Data Report (0x12) . . . . . . . . . . . . . . . . . . . 41
7.5. Perform Control (0x1A) . . . . . . . . . . . . . . . . . 42
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
9. Security Considerations . . . . . . . . . . . . . . . . . . . 42
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
10.1. Informative References . . . . . . . . . . . . . . . . . 43
10.2. Normative References . . . . . . . . . . . . . . . . . . 43
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction
This document specifies an Asynchronous Management Protocol (AMP)
that provides application-layer network management service conformant
to the Asynchronous Management Architecture [AMA].
1.1. Overview
Network management protocols define the messages that implement
management functions amongst managed and managing devices in a
network. These functions include the definition, production, and
reporting of performance data, the application of administrative
policy, and the configuration of behavior based on time and state
measurements.
Networks whose communication links are frequently challenged by
physical or administrative effects cannot guarantee the low-latency,
duplex data communications necessary to support sessions and other
synchronous communication. For such networks, a new protocol is
required which provides familiar network management services in the
absence of sessions and operator-in-the-loop control.
AMP accomplishes the network management function using open-loop,
intelligent-push, asynchronous mechanisms that better scale as link
challenges scale. The protocol is designed to support several
desirable properties outlined in [AMA] and briefly listed below.
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o Intelligent Push of Information - The intelligent push of
information eliminates the need for round-trip data exchange.
This is a necessary consequence of operating in an open-loop
system. AMP is designed to operate even in networks of solely
unidirectional links.
o Small Message Sizes - Smaller messages require smaller periods of
viable transmission for communication, incur less retransmission
cost, and consume fewer resources when persistently stored enroute
in the network. AMP minimizes the size of a message whenever
practical, to include packing and unpacking binary data, variable-
length fields, and pre-configured data definitions.
o Absolute and Custom Data Identification - Fine-grained
identification allows data in the system to be explicitly
addressed while flexible data identification allows users to
define their own customized, addressed data collections. In both
cases, the ability to define precisely the data required removes
the need to query and transmit large data sets only to filter/
downselect desired data at a receiving device.
o Autonomous, Stateless Operation - AMP does not rely on session
establishment or round-trip data exchange to perform network
management functions. Wherever possible, the AMP is designed to
be stateless. Where state is required, the AMP provides
mechanisms to support transactions and graceful degradation when
nodes in the network fail to synchronize on common definitions.
o Compatibility with Low-Latency Network Management Protocols - AMP
adopts an identifier approach compatible with the Managed
Information Base (MIB) format used by Internet management
protocols such as the Simple Network Management Protocol (SNMP),
thus enabling management interfaces between challenged networks
and unchallenged networks (such as the Internet).
1.2. Technical Notes
o 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 data types defined by the AMP are self-terminating. This
means that, given an indefinite-length octet stream, each data
type can be unambiguously decoded from the stream without
requiring additional information such as a length field separate
from the data type definition.
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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 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)". 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
1.3. Scope
1.3.1. 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.
It is assumed that the protocols used to carry AMP messages provide
addressing, confidentiality, integrity, security, fragmentation
support and other network/session layer functions. Therefore, these
items are outside of the scope of this protocol.
1.3.2. Specification Scope
This document describes the format of the AMP messages exchanged
amongst managing and managed devices in a challenged network. This
document further describes the rationale behind key design decisions
to the extent that such a description informs the operational
deployment and configuration of an AMP implementation. This document
does not address specific data configurations of AMP-enabled devices,
nor does it discuss the interface between AMP and other management
protocols, such as SNMP.
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1.4. 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].
2. Terminology
Note: The terms "Actor", "Agent", "Application Data Model", "Atomic
Data", "Computed Data", "Control", "Literal", "Macro", "Manager",
"Report Template", "Report Entry", and "Rule" are used without
modification from the definitions provided in [AMA].
Additional terms critical to understanding the proper operation of
the AMP are as follows.
o Managed Item Definition (MID) - A parameterized structure used to
uniquely identify all data and control definitions within the AMP.
MIDs are a super-set of Object Identifiers (OIDs) and the
mechanism by which the AMP maintains data compatibility with other
management protocols. MIDs are defined in Section 3.3.
o Report (RPT) - An ordered collection of report entries gathered by
an Agent and provided to one or more Managers. Reports represent
the fundamental unit of data exchange from an Agent to a Manager
within the AMP. Report messages are defined in Section 7.4.
o State-Based Rule (SRL) - A rule in the AMP whose action is
performed if a defined predicate evaluates to true. SRLs are
defined in Section 4.7.
o Time-Based Rule (TRL) - A rule in the AMP whose action is
performed at regular intervals. SRLs are defined in Section 4.6.
3. Data Model
This section identifies the data types used to capture information
within the AMP.
3.1. Primitive Types
Primitive types are those that are not comprised of any other set of
types known to the AMP.
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3.1.1. Standard Numeric Types
The AMP supports types for unsigned bytes, 32/64-bit signed and
unsigned integers, 32/64-bit floating point values, and strings, as
outlined in Table 1.
+------------+------------+-----------------------------------------+
| AMP Type | Bit Width | Description |
+------------+------------+-----------------------------------------+
| BYTE | 8 | unsigned byte value |
| | | |
| INT | 32 | Signed integer in 2's complement |
| | | |
| UINT | 32 | Unsigned integer in 2's complement |
| | | |
| VAST | 64 | Signed integer in 2's complement |
| | | |
| UVAST | 64 | Unsigned integer in 2's complement |
| | | |
| REAL32 | 32 | Single-precision, 32-bit floating point |
| | | value in IEEE-754 format. |
| | | |
| REAL64 | 64 | Double-precision, 64-bit floating point |
| | | value in IEEE-754 format. |
| | | |
| STR | Varies | NULL-terminated series of characters in |
| | | UTF-8 format. |
+------------+------------+-----------------------------------------+
Table 1: Standard Numeric Types
3.1.2. Self-Delimiting Numeric Value (SDNV)
The data type "SDNV" refers to a Self-Delimiting Numerical Value
(SDNV) described in [RFC6256]. SDNVs are used in the AMP to capture
any data items that are expected to be 8 bytes or less in total
length. AMP Actors MAY reject any value encoded in an SDNV that is
greater than 8 bytes in length.
One popular use of SDNVs in the AMP is to compress the representation
of 32/64-bit integer values. This simplifies the AMP by not having
to additionally support 8/16-bit versions of integers without
incurring significant transmission waste when encoding small numbers
into 32/64-bit representations.
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3.1.3. Timestamp (TS)
A timestamp value can represent either a relative or absolute time
within the AMP. An AMP relative time is defined as the number of
seconds between two AMP events (such as the receipt of a control by
an agent and the execution of that control). An AMP absolute time is
defined as UTC time using the Unix/POSIX Epoch.
Since timestamps are a common component in AMP messages and controls,
they should be made as small as possible. Therefore, timestamps in
AMP do not add a special flag to determine whether the given time is
an absolute or relative time. Instead, AMP defines a simple formula
to unambiguously determine the type of time represented without
increasing the overall size of a timestamp.
AMP uses September 9th, 2012 as the timestamp epoch (UTC time
1347148800). Times less than this value MUST be considered a
relative time. Values greater than or equal to this epoch MUST be
considered as absolute times. In all cases, the AMP timestamp is
encoded as an SDNV to avoid the 32-bit 2038 UTC rollover problem.
The absolute time associated with a timestamp can be calculated
unambiguously with the following pseudocode.
IF (timestamp < 1347148800) THEN
absolute_time = current_time + timestamp
ELSE
absolute_time = timestamp
3.2. Compound Types
Compound types are data types defined as an aggregation of other data
types.
3.2.1. Binary Large Object (BLOB)
A Binary Large Object (BLOB) is an ordered collection of bytes
prefaced by the number of bytes making up the BLOB. The format of a
BLOB is illustrated in Figure 2. BLOBs are used in the AMP to
capture variable data sets that are too large to efficiently store in
an SDNV.
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Binary Large Object Format
+---------+--------+--------+ +--------+
| # Bytes | BYTE 1 | BYTE 2 | ... | BYTE N |
| [SDNV] | [BYTE] | [BYTE] | | [BYTE] |
+---------+--------+--------+ +--------+
Figure 2: Binary Large Object Format
3.2.2. Data Collection (DC)
A Data Collection (DC) is an ordered set of BLOBs, prefaced by the
number of BLOBs making up the collection. The format of a DC is
illustrated in Figure 3.
Data Collection
+---------+--------+--------+ +--------+
| # BLOBs | BLOB 1 | BLOB 2 | ... | BLOB N |
| [SDNV] | [BLOB] | [BLOB] | | [BLOB] |
+---------+--------+--------+ +--------+
Figure 3: Data Collection Format
3.2.3. Typed Data Collection (TDC)
The Typed Data Collection (TDC) is a special kind of DC which encodes
type information as the first BLOB in the collection. The TDC data
type is used to capture typical "TLV" (type, length, value)
information in the AMP.
The TDC format is illustrated in Figure 4
Typed Data Collection
+---------+-----------+-------------+ +-------------+
| # BLOBs | Type BLOB | Data BLOB 1 | ... | Data BLOB N |
| [SDNV] | [BLOB] | [BLOB] | | [BLOB] |
+---------+-----------+-------------+ +-------------+
Figure 4: Typed Data Collection Format
The TDC fields are defined as follows.
# BLOBs
This represents the number of BLOBS that comprise the TDC.
Since the TDC has one BLOB for each data item in the
collection, plus one additional BLOB for type information,
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the # BLOBs value MUST be equal to one more than the number
of data items in the collection.
Type BLOB
Each BYTE in the Type BLOB represents a type enumeration of a
corresponding Data BLOB. For example, the 3rd BYTE in the
Type BLOB holds the type enumeration of the 3rd Data BLOB in
the TDC. Since there is exactly 1 byte per data item in the
Type BLOB, the overall size of this BLOB MUST be the total
number of data items in the TDC.
Data BLOB
The Nth Data BLOB holds the Nth data value in the collection.
For example, consider the following set of data values: {(UINT) 3,
(REAL32) 3.14, (STR) "pi"}. The corresponding TDC would have 4 BLOBs.
BLOB 1 would have length 3 and contain the enumerations for UINT,
REAL32, and STR - encoded in one BYTE each. BLOBs 2, 3, and 4 would
hold the original data. This example is illustrated in Figure 5.
Typed Data Collection Example
Data Set TDC
+---------------+ +---------------------------------+
| # Items = 3 | | # BLOBs = {4} |
+---------------+ +---------------------------------+
| (UINT) 3 |--------+ | TYPE BLOB = {UINT, REAL32, STR} |
+---------------+ | +---------------------------------+
| (REAL32) 3.14 |-----+ +->| DATA BLOB 1 = {3} |
+---------------+ | +---------------------------------+
| (STR) "pi" |--+ +---->| DATA BLOB 2 = {3.14} |
+---------------+ | +---------------------------------+
+------->| DATA BLOB 3 = {"pi"} |
+---------------------------------+
Figure 5: Typed Data Collection Example
The rationale for extracting data type information into a Type BLOB
and placing that BLOB at the beginning of the TDC is to enable faster
performance for type validators. With the Type BLOB, a validator can
inspect one BLOB to ensure that the elements within the TDC match the
expected type specifications. Without a Type BLOB, type information
would need to be interspersed with data values throughout the TDC.
In that case, a type validator would need to scan through the entire
set of bytes comprising the TDC looking for type information. This
would significantly alter the speed of type checking in the AMP.
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The rationale for placing data values directly in a Data BLOB is to
enable rapid navigation. As mentioned in Section 1.2, every data
type defined in the AMP is deterministic in length. However, this
determination may require deep inspection of the data in cases of
variable-length headers and optional fields. By placing the data
value in a Data BLOB, the length of the value may be asserted to
allow a data parser to rapidly calculate the position of data item N
in the TDC. The redundancy of storing a pre-calculated length for
each data value when the data value length can be calculated from the
data itself is a processing tradeoff made by AMP given the relative
frequency with which the TDC is used to communicate Report and
Control parameters.
3.2.4. Table (TBL)
A TBL is a names, typed, collection of tabular data with each row
represented as a DC and each column defined by both a column name and
a column type. Each row in the TBL MUST have the same length and the
ith BLOB of each row DC MUST correspond to the ith column in the
table.
The TBL format is illustrated in Figure 6
Table
+-----------+-----------+--------+-------+ +-------+
| Col Names | Col Types | # Rows | Row 1 | | Row N |
| [DC] | [BLOB] | [SDNV] | [DC] | ... | [DC] |
+-----------+-----------+--------+-------+ +-------+
Figure 6: Table Format
The TBL fields are defined as follows.
Col Names
Column names are captured as a DC with the ith entry in the
DC representing the name of the ith column. This DC MUST
have a number of entries equal to the number of columns in
the table. Each entry in the DC is considered to be of type
STR.
NOTE: It is being considered to make this field a TDC instead
of a DC to allow individual Col Names to be of different data
types, instead of making them always be strings.
Col Types
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Similar to the Type BLOB of the TDC, the Col Types BLOB
contains one BYTE for each column in the TBL and this BYTE
holds the type enumeration for the column. Therefore, the
Col Types BLOB MUST have a length equal to the number of
columns in the table and each BYTE in the BLOB MUST contain a
correct enumeration of an AMP type. This field MUST contain
one of the AMP data structure enumerations identified in
Section 5.
# Rows
This field captures the number of rows in the TBL. If the
number of rows in the TBL is set to 0, that indicates there
is no additional data after this field.
Row 1 .. Row N
Each row in the TBL is represented by a DC, with the ith BLOB
in the DC representing the data in the ith column of the TBL.
Each row DC MUST have a number of BLOBs equal to the number
of columns.
The Figure below illustrates a table of data relating to months of
the year on the left and the corresponding populated TBL structure
for this table on the right.
+--------------------------------------+
+-----+------+------+ +----->| Col Names DC = {"Month","Ord","Days"}|
|Month| Ord | Days |-----+ +--------------------------------------+
|(STR)|(UINT)|(UINT)|----------->| Col Types BLOB = {STR, UINT, UINT} |
+-----+------+------+ +--------------------------------------+
|Jan | 1 | 31 |--------+ | Num Rows = 3 |
+-----+------+------+ | +--------------------------------------+
|Oct | 10 | 31 |-----+ +-->| Row 1 DC = {"Jan", 1, 31} |
+-----+------+------+ | +--------------------------------------+
|June | 6 | 30 |--+ +----->| Row 2 DC = {"Oct", 10, 31} |
+-----+------+------+ | +--------------------------------------+
+-------->| Row 3 DC = {"June", 6, 30} |
+--------------------------------------+
Figure 7: Table Example
3.3. Managed Identifiers (MIDs)
Structures defined and exchanged within the AMP must be uniquely
identifiable both within a network and (when AMP is used in an
overlay) across networks. This section describes the "Managed
Identifier" (MID) used to provide unique naming for the AMP
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structures defined in Section 4. The MID is a variable-length
structure with optional fields.
The unique identifier at the core of a MID is based on the Object
Identifier (OID) and its Basic Encoding Rules (BER) as identified in
the ITU-T X.690 standard. The use of OIDs in the MID structure
allows Agents and Managers to interface with other management schemes
(such as SNMP) at management boundaries between challenged and
unchallenged networks.
The MID consists of a mandatory flag BYTE, a mandatory OID, and
optional annotations to assist with filtering, access control, and
parameterization. The MID structure is illustrated in Figure 8.
MID format
+--------+--------+--------+--------+
| Flags | Issuer | OID | Tag |
| [BYTE] | [SDNV] |[VARIED]| [SDNV] |
| | (opt) | | (opt) |
+--------+--------+--------+--------+
Figure 8: Managed Identifier Format
The MID fields are defined as follows.
Flags
Flags are used to describe the type of structure identified
by the MID, identify which optional fields in the MID are
present, and the encoding used to capture the component's
OID. The layout of the flag byte is illustrated in Figure 9.
MID Flag Format
+-----+---+---+------------+
| OID |TAG|ISS| STRUCT ID |
+-----+---+---+------------+
| 7 6 | 5 | 4 | 3 2 1 0 |
+-----+---+---+------------+
MSB LSB
Figure 9
STRUCT ID
The lower nibble of the MID flag identifies the kind
of data structure being identified by this
identifier. This field MUST contain one of the AMP
data structure enumerations identified in Section 5.
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Issuer Present (ISS)
Whether the issuer field is present (1) or not (0)
for this MID. If this flag has a value of 1 then the
issuer field MUST be present in the MID. Otherwise,
the issuer field MUST NOT be present in the MID.
Tag Present (TAG)
Whether the tag field is present (1) or not (0) for
this MID. If this flag has a value of 1 then the tag
field MUST be present in the MID. Otherwise, the tag
field MUST NOT be present.
OID Type (OID)
Whether the contained OID field represents a full OID
(0), a parameterized OID (1), a compressed full OID
(2), or a compressed, parameterized OID (3).
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 MID uniqueness. This value, for example,
may come from a global registry of organizations, an issuing
node address, or some other network-unique marking. The
issuer field MUST NOT be present for any MID defined as part
of an ADM.
OID
The core of a MID is its encapsulated OID. Aside from the
flag byte, this is the only other mandatory element within a
MID. The AMP defines four types of OID references: Full
OIDs, Parameterized OIDs, Compressed Full OIDs, and
Compressed Parameterized OIDs, which are defined as follows.
Full OID
This is a binary representation of the full OID
associated with the named value. The OID is encoded
using a modified form of the ASN.1 Basic Encoding
Rules (BER) for Object Identifiers (type value of
0x06). In the standard ASN.1 encoding, four octet
sets are defined: identifier octets, length octets,
contents octets, and end-of-contents octets. An AMP
Full OID does not use the identifier, length, or end-
of-contents octets. Instead, an AMP Full OID is
comprised of two fields: the length in bytes of the
encoded OID followed by the OID contents octets. It
should be noted that this matches, exactly, the
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definition of the BLOB type. The Full OID format is
illustrated in Figure 10.
+----------+
| Full OID |
| [BLOB] |
+----++----+
||
||
_____________________/ \_________________________
/ \
+------------+---------+---------+ +---------+
| OID Length | Octet 1 | Octet 2 | ... | Octet N |
| [SDNV] | [BYTE] | [BYTE] | | [BYTE] |
+------------+---------+---------+ +---------+
Figure 10: Full OID Format
Parameterized OID
The parameterized OID is represented as a Full OID
followed by one or more parameters. Parameterized
OIDs are used to templatize the specification of data
items and otherwise provide parameters to Controls
without requiring potentially unmanageable growth of
a Full OID namespace. The format of a parameterized
OID is given in Figure 11.
+----------+------------+
| FULL OID | Parameters |
| [BLOB] | [TDC] |
+----------+-----++-----+
||
||
__________________/ \____________________________________
/ \
+----------+------------+--------+--------+ +--------+
| # Params | Parm Types | Parm 1 | Parm 2 | | Parm N |
| [SDNV] | [BLOB] | [BLOB] | [BLOB] | ... | [BLOB] |
+----------+------------+--------+--------+ +--------+
Figure 11: Parameterized OID Format
Compressed OID
Since many related OIDs share a common and lengthy
hierarchy there is opportunity for significant
message size savings by defining a shorthand for
commonly-used portions of the OID tree. A partial
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OID is a tuple consisting of a nickname for a pre-
defined portion of the OID tree, followed by a
relative OID. Nicknames are defined in Section 3.4.
The format of a compressed OID is given in Figure 12.
+----------+--------------+
| Nickname | Relative OID |
| [SDNV] | [BLOB] |
+----------+--------------+
Figure 12: Compressed OID Format
Compressed Parameterized OID
A compressed, parameterized OID is similar to a
compressed OID. In this instance, the tuple
contained in this field is the nickname for the pre-
defined portion of the OID tree (as an SDNV) followed
by a parameterized OID whose hierarchy begins at the
place identified by the nickname. The format of a
compressed OID is given in Figure 13.
Compressed Parameterized OID Format
+----------+--------------+------------+
| Nickname | Relative OID | Parameters |
| [SDNV] | [BLOB] | [TDC] |
+----------+--------------+------------+
Figure 13: Compressed Parameterized OID Format
Tag
A value used to disambiguate multiple MIDs with the same OID/
Issuer combination. The definition of the tag is left to the
discretion of the MID issuer. Options for tag values include
an issuer-known version number or a hashing of the data
associated with the MID. The tag field MUST NOT be present
for any MID defined as part of an ADM.
3.4. Nicknames
There are several strategies for reducing the overall size of an OID
in an operational system. The AMP method for OID size reduction is
to publish global enumerations that represent strategic nodes in an
OID tree. This published, global enumeration is called a Nickname.
As mentioned in the discussion of compressed OIDs above, a nickname
is used in lieu of a portion of the OID tree. ADMs may define their
own nicknames so long as their definitions do not conflict with the
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definitions of nicknames in other ADMs. AMP does not provide the
ability to assign nicknames dynamically.
Like other numeric types, nicknames are encoded as SDNVs allowing
them to be of arbitrary length. For example, 3 bytes of SDNV can
encode over 2 million nicknames. Assuming ADMs are allotted 10
nicknames each, this approach can accommodate over 200,000 ADMs
before requiring a 4th byte for nickname information.
Additionally, since nicknames are globally unique, neither an AMP
Agent or Manager is ever required to expand a compressed OID to
assert uniqueness or perform other identification. It is recommended
that compressed OIDs be used whenever possible.
3.5. Parameters
Parameterized OIDs provide a powerful mechanism for customizing
behavior for certain AMP structures. Parameterized values in AMP are
formally defined in ADMs with a well-known, static typing. When an
ADM specifies that an identified AMP structure may be parameterized,
the specification MUST list the number of expected parameters and the
type associated with each parameter. When a particular instance of a
parameterized AMP structure is generated by an Agent or a Manager,
the MID identifying that instance MUST contain a parameterized OID
and the parameters associated with the OID MUST match in number and
type the specification.
3.5.1. Optional Parameters
When parameterizing an AMP structure, some parameters may be optional
with default values defined if parameters are omitted. The use of
optional parameters helps keep MID values small when using default
values for parameters is a common case, rather than forcing all
parameters to be provided all the time.
Since each individual parameter in a TDC is represented as a BLOB, a
parameter can be omitted by specifying a length of 0 BYTES for the
Data BLOB holding the parameter. If a parameter is omitted and is
not considered optional by the parameterized AMP structure, this MUST
be considered an error.
3.5.2. Parameter Evaluation
The type value associated with the TDC in a parameter list is only
used to provide type-checking safety to ensure that the given
parameters match expected parameter types. It is important to
understand that the types in the parameter TDC DO NOT define the
parameterized interface - only the ADM defines the typed interface.
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Parameters within the TDC may be represented in one of two ways: the
parameter itself (parameter by value), or an expression used to
determine the parameter (parameter by evaluation).
3.5.2.1. Parameter By Value
When specifying a parameter using a value, the BYTE representing the
parameter type MUST be set to the expected parameter type and the
BLOB representing the parameter contents MUST be the parameter value.
For example, consider a parameterized OID that takes 1 parameter,
which it expects to be an unsigned integer (UINT). When populating
this parameter by value, the type of the populated parameter field
MUST be UINT and the parameter value MUST be the unsigned integer.
3.5.2.2. Parameter By Evaluation
When the value of a parameter is likely to change, an Expression
(EXPR) may be substituted for the parameter value. When it comes
time to interpret the parameter value, the current value of the
Expression is calculated and used as the parameter value.
A parameter defined by evaluation MUST be of type EXPR, and the type
of the EXPR must be equal to the expected type of the parameter.
Expressions and Expression types are discussed in Section 3.6.2.
NOTE: If the expected type of the parameter is already EXPR, and a
parameter of type EXPR is provided, then the system MUST treat the
situation as if it were a parameter by value. AMP DOES NOT support
an EXPR which references another EXPR as doing so leads to
significant confusion in implementations and the possibility of
circular reference.
3.5.2.3. Identifying Parameter Approach
The determination of whether a parameter has been provided by value
or by evaluation is made by comparing the given type of the parameter
to the expected type of the parameter.
If the parameter type and the expected type match, then the parameter
MUST be considered by value. If the parameter type is an EXPR and
the EXPR type matches the expected type, then the parameter MUST be
considered by evaluation of the EXPR. In any other case, the
parameter MUST be considered invalid as being from a type mismatch.
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3.6. Special Types
In addition to the data types already mentioned, the following
special data types are also defined.
3.6.1. MID Collections (MC)
A MID collection is comprised of a value identifying the number of
MIDs in the collection, followed by each MID, as illustrated in
Figure 14.
+--------+-------+ +-------+
| # MIDs | MID 1 | ... | MID N |
| [UINT] | [MID] | | [MID] |
+--------+-------+ +-------+
Figure 14: MID Collection
3.6.2. Expressions (EXPR)
Expressions apply mathematical operations to values to generate new
values on an Agent. The EXPR type in AMP is a collection of MIDs
that represent a postfix notation stack of data, Literal, and
Operator types. For example, the infix expression A * (B * C) is
represented as the sequence A B C * *. The format of an expression is
illustrated in Figure 15.
+--------+------------+
| Type | Expression |
| [BYTE] | [MC] |
+--------+------------+
Figure 15
Type
The enumeration representing the type of the result of the
evaluated expression.
Expression
An expression is represented in the AMP as a MID collection,
where each MID in the ordered collection represents the data,
Literals, and/or Operations that comprise the Expression.
3.6.3. Predicate (PRED)
Predicates are Expressions whose values are interpreted as a Boolean.
The value of zero MUST be considered "false" and all other values
MUST be considered "true".
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4. AMP Structures
This section identifies the AMP structures that implement the AMA
logical data model.
4.1. AMA Overview
The AMA defines a series of logical components that should be
included as part of an AMP. These components are summarized from the
AMA in the following table.
+-----------+--------------------------------------+----------------+
| AMA | Summary Description | AMP Structure |
| Component | | |
+-----------+--------------------------------------+----------------+
| Atomic | A typed, measured value whose | Externally |
| Data | definition and value determination | Defined Data |
| | occurs externally to the AMP. | |
| | | |
| Computed | A typed, computed value whose | Variable |
| Data | definition and value determination | |
| | occurs within the AMP. | |
| | | |
| Report | Collection of Atomic and/or Computed | Report Entry |
| Entry | data and/or other Reports. | |
| | | |
| Control | Parameterized opcode for any action | Control |
| | that can be taken by an Agent. | |
| | | |
| Rule | A pre-configured response to a pre- | State-Based |
| | defined time or state on an Agent. | Rule, Time- |
| | | Based Rule |
| | | |
| Macro | An ordered collection of Controls. | Macro |
| | | |
| Literal | A constant used when evaluating | Literal |
| | Rules or determining the value of | |
| | Computed Data. | |
| | | |
| Operator | An opcode representing a | Operator |
| | mathematical function known to an | |
| | Agent. | |
+-----------+--------------------------------------+----------------+
AMP Logical Components
The AMP implements these logical components in largely a one-to-one
fashion with a few exceptions. This section describes the format of
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these structures in the context of the aforementioned AMP data types.
NOTE: The expression of these structures is only to describe how they
appear in messages exchanged between and amongst Agents and Managers.
Individual software applications may choose their own internal
representation of these structures.
4.2. Externally Defined Data (EDD)
Externally defined data (EDD) are defined as part of ADMs for various
applications and protocols. These represent values that are
calculated outside of the context of Agents and Managers, such as
those values measured by firmware. As such, their value is defined
external to the AMP system.
4.2.1. Definition
The representation of these data is simply their identifying MIDs.
The representation of an EDD is illustrated in Figure 16.
+-------+
| ID |
| [MID] |
+-------+
Figure 16: Externally Defined Data Format
ID
This is the MID identifying the EDD. Since EDDs are always
defined solely in the context of an ADM, this MID MUST NOT
have an ISSUER field and MUST NOT have a TAG field.
4.2.2. Processing
Managers
o Store the MID for each known EDD definition.
o Associate a data type to each known EDD definition.
o Encode EDD MIDs in Controls to Agents, as appropriate.
Agents
o Store the MID for each known EDD definition.
o Associate a data type to each known EDD definition.
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o Calculate the value of an EDD definition when required, such as
when generating a Report Entry or evaluating an Expression.
4.3. Variables (VAR)
Variables (VAR) are either statically defined in an ADM or
dynamically defined by a particular network. They differ from EDDs
in that they are completely described by other known data in the
system (either other Variables, or other EDDs). For example, letting
E# be a EDD item and V# be a VAR item, the following are examples of
VAR definitions.
V1 = E1 * E2
V2 = V1 + E3
4.3.1. Definition
VARs are defined by the triplet (ID, TYPE, EXPR) as illustrated in
Figure 17.
+------------+
| Variable |
| [VAR] |
+-----++-----+
||
||
______________/ \_____________
/ \
+-------+--------+-------------+
| ID | Type | Initializer |
| [MID] | [BYTE] | [EXPR] |
+-------+--------+-------------+
Figure 17: Variable Format
ID
This is the MID identifying the VAR. When defined in an ADM
this MID MUST NOT have an ISSUER field and MUST NOT have a
TAG field. When defined outside of an ADM, the MID MUST have
an ISSUER field and MAY have a TAG field. This ID MUST NOT
encapsulate a parameterized OID.
Type
This is the type of the VAR, and acts as a static cast for
the result of the initializing Expression. Note, it is
possible to specify a type different than the resultant type
of the initializing Expression. For example, if an
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Expression adds two single-precision floating point numbers,
the VAR MAY have an integer type associated with it. This
BYTE is populated with the enumeration of the associated type
and MUST be defined as one of the numeric data types outlined
in Section 5.
Initializer
The initial value of the VAR is given by an initializing
Expression. In the case where the type of the VAR is an
EXPR, then the initializer is simply copied as the value of
the VAR. In the case where the type of the VAR is anything
other than EXPR, then the initializer Expression is evaluated
and the resultant value is copied into the VAR as its value.
Once the initializer Expression has been used to calculate an
initial value for the VAR it may be discarded.
4.3.2. Processing
Managers
o Store the MID for each ADM-defined VAR definition.
o Send requests to Agents to add, list, describe, and remove VAR
definitions.
o Remember custom VAR definitions.
o Encode VAR MIDs in Controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined VAR definition.
o Calculate the value of VARs when required, such as during Rule
evaluation, calculating other VAR values, and generating Reports.
o Add, remove, list, and describe custom VAR definitions.
4.4. Report Template (RPTT), Report Entry (RPTE)
A Report is an AMP message whose format is described in Section 7.4.
This message is populated with Report Entries that contain data
formatted in accordance with Report Templates.
A Report Template is the ordered set of data descriptions that
describe how values will be represented in a corresponding Report
Entry. Templates can be viewed as a schema that describes how to
interpret a Report Entry, since these entries do not embed schema or
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name information in them. Templates contain no values and are either
defined in an ADM or configured between Managers and Agents.
A Report Entry is a set of data values populated using a given Report
Template. A Report Entry contains only data values and no template
definitions. By removing definition information from a Report Entry,
the volume of information sent from the Agent to the Manager is
greatly reduced. When a Report Entry is generated as capturing the
result of a Control, the Report Template for the Control is assumed
to be known to both the generating Agent and all receiving Managers.
4.4.1. Definition
A Report Template is modeled as a MC, as each data definition in the
template is identified by a MID.
A Report Entry is a TDC identified by a MID and generated to capture
the return value of a Control. Generated Report Entries MUST be
collected by an Agent periodically, placed in an AMP Report message,
and sent to one or more Managers.
When a Report Entry is generated in accordance with a named Report
Template, the entry identifier MUST be the same as the template
defining the data in the entry. When a Report Entry is generated
absent a defined Report Template, then the entry identifier MUST be
the MID of the Control generating the report.
The definition of a Report Entry is illustrated in Figure 18.
+-------+--------+
| ID | Values |
| [MID] | [TDC] |
+-------+---++---+
||
||
___________________________/ \__________________________________
/ \
+----------+-------------+---------+---------+ +---------+
| # Values | Value Types | Value 1 | Value 2 | | Value N |
| [SDNV] | [BLOB] | [BLOB] | [BLOB] | ... | [BLOB] |
+----------+-------------+---------+---------+ +---------+
Figure 18: Report Entry Format
ID
This is the MID identifying the source used to build the
entry. If this field identifies a template, and the Report
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Template is defined in an ADM, this MID MUST NOT have an
ISSUER field and MUST NOT have a TAG field. If the Report
Template is not defined in an ADM then this MID MUST have an
ISSUER field and MAY have a TAG field. If this field
identifies a Control then the MID MUST NOT have an ISSUER
field and MUST NOT have a TAG field.
A Report Template MID MAY be parameterized. If the Report
Template MID is parameterized, the parameters MUST be used
(in the same number and order) to customize any parameterized
data in the report when generating values for the Report
Entry.
Values
This is the TDC containing all of the data values that
comprise the Report Entry. It is important to note that data
values may be other Report Entries.
4.4.2. Processing
Managers
o Store the MID for each ADM-defined Report Templates.
o Send requests to Agents to add, list, describe, and remove custom
Report Templates.
o Remember custom Report Templates when processing Report Entries
received by Agents.
o Encode Report Template MIDs in Controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined Report Template.
o Populate Report Entries for transmission to Managers when required
by a Control.
o Add, remove, list, and describe custom Report Templates.
o Agents SHOULD collect multiple Report Entries into a single Report
AMP message for transmission to a Manager rather than sending
multiple, individual Report messages to a Manager with one Report
Entry per Report message.
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4.5. Control
A Control represents a pre-defined (possibly parameterized) opcode
that can be run on an Agent. Controls in the AMP are always defined
in the context of an ADM. 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 MID that
identifies them, similar to EDDs.
4.5.1. Definition
The format of a Control is illustrated in Figure 19.
+-------+
| ID |
| [MID] |
+-------+
Figure 19: Control Format
ID
This is the MID identifying the Control. Since Controls are
always defined solely in the context of an ADM, this MID MUST
NOT have an ISSUER field and MUST NOT have a TAG field.
4.5.2. Processing
Managers
o Store the MID for each ADM-defined Control definition.
o Store the number of parameters and each parameter type for
parameterized Controls.
o Encode Control MIDs in other Controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined Control definition.
o Implement Controls in firmware and run Controls with appropriate
parameters when necessary in the context of Manager direction and
Rule execution.
o Communicate "return" values from Controls back to Managers as
Report Entries where appropriate.
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4.6. Time-Based Rule (TRL)
A Time-Based Rule (TRL) specifies that a particular action should be
taken by an Agent based on some time interval. A TRL specifies that
starting at a particular START time, and for every PERIOD seconds
thereafter, an ACTION should be run by the Agent until the ACTION has
been run for COUNT times. When the TRL is no longer valid it MAY BE
discarded by the Agent.
Examples of TRLs include:
Starting 2 hours from receipt, produce a Report Entry for Report
Template R1 every 10 hours ending after 20 times.
Starting at the given absolute time, run Macro M1 every 24 hours
ending after 365 times.
4.6.1. Definition
The format of a TRL is illustrated in Figure 20.
+-------+-------+--------+--------+--------+
| ID | START | PERIOD | COUNT | ACTION |
| [MID] | [TS] | [UINT] | [UINT] | [MC] |
+-------+-------+--------+--------+--------+
Figure 20: Time-Based Rule Format
ID
This is the MID identifying the TRL. When a TRL is defined
in an ADM this MID MUST NOT have an ISSUER field and MUST NOT
have a TAG field. When the TRL is defined outside of an ADM,
the MID MUST have an ISSUER field and MAY have a TAG field.
This ID MUST NOT encapsulate a parameterized OID.
START
The time at which the TRL should start to be evaluated. This
will mark the first running of the action associated with the
TRL.
PERIOD
The number of seconds to wait between running the action
associated with the TRL.
COUNT
The number of times the TRL action may be run. The special
value of 0 indicates the TRL should continue running the
action indefinitely.
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ACTION
The collection of Controls and/or Macros to run by the TRL.
This is captured as a MC with the constraint that every MID
within the MC represent a Control or Macro.
4.6.2. Processing
Managers
o Send requests to Agents to add, list, describe, and remove custom
TRL definitions.
o Remember custom TRL definitions when processing Reports received
by Agents.
o Send requests to Agents to suspend/resume the evaluation of TRLs.
o Encode TRL MIDs in Controls to Agents, as appropriate.
Agents
o Run the actions associated with TRLs in accordance with their
start time and period.
o Add, remove, list, and describe custom TRL definitions.
o Suspend and resume the evaluation of a TRL when directed by a
Manager or another Rule.
o Report on the status of TRLs.
4.7. State-Based Rule (SRL)
A State-Based Rule (SRL) specifies that a particular action should be
taken by an Agent based on some evaluation of the internal state of
the Agent. A SRL specifies that starting at a particular START time
an ACTION should be run by the agent if some CONDITION evaluates to
true, until the ACTION has been run COUNT times. When the SRL is no
longer valid it MAY be discarded by the agent.
Examples of SRLs include:
Starting 2 hours from receipt, whenever V1 > 10, produce a Report
Entry for Report Template R1 no more than 20 times.
Starting at some future absolute time, whenever V2 != V4, run
Macro M1 no more than 36 times.
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4.7.1. Definition
The format of a SRL is illustrated in Figure 21.
+-------+-------+--------+--------+--------+
| ID | START | COND | COUNT | ACTION |
| [MID] | [TS] | [PRED] | [UINT] | [MC] |
| | | | | |
+-------+-------+--------+--------+--------+
Figure 21: State-Based Rule Format
ID
This is the MID identifying the SRL. When a report is
defined in an ADM this MID MUST NOT have an ISSUER field and
MUST NOT have a TAG field. When the SRL is defined outside
of an ADM, the MID MUST have an ISSUER field and MAY have a
TAG field. This ID MUST NOT encapsulate a parameterized OID.
START
The time at which the SRL condition should start to be
evaluated. This will mark the first evaluation of the
condition associated with the SRL.
CONDITION
The Predicate which, if true, results in the SRL running the
associated action.
COUNT
The number of times the SRL action can be run. The special
value of 0 indicates there is no limit on how many times the
action can be run.
ACTION
The collection of Controls and/or Macros to run as part of
the action. This is captured as a MC data type with the
constraint that every MID within the MC represent a Control
or Macro.
4.7.2. Processing
Managers
o Send requests to Agents to add, list, describe, suspend, resume,
and remove custom SRL definitions.
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o Remember custom SRL definitions when processing Report Entries
received by Agents.
o Encode SRL MIDs in Controls to Agents, as appropriate.
Agents
o Run the actions associated with SRLs in accordance with their
start time and evaluation of their predicate.
o Add, remove, list, and describe custom SRL definitions.
o Suspend and resume SRL evaluation when commanded by a Manager or
another Rule.
4.8. Macro
Macros in the AMP are ordered collections of MIDs (an MC) that
contain Controls or other Macros. When run by an Agent, each MID in
the MC is run in order.
Any AMP implementation MUST allow at least 4 levels of Macro nesting.
Implementations MUST provide some mechanism to prevent recursive
nesting of Macros.
While the MIDs representing any given Control may be parameterized,
the MID associated with a Macro MAY NOT be parameterized.
4.8.1. Definition
The format of a Macro is illustrated in Figure 22.
+-------+------------+
| ID | Definition |
| [MID] | [MC] |
+-------+------------+
Figure 22: Macro Format
ID
This is the MID identifying the Macro. When a Macro is
defined in an ADM this MID MUST NOT have an ISSUER field and
MUST NOT have a TAG field. When the Macro is defined outside
of an ADM, the MID MUST have an ISSUER field and MAY have a
TAG field. This ID MUST NOT encapsulate a parameterized OID.
Definition
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This is the ordered collection of MIDs that identify the
Controls and other Macros that should be run as part of
running this Macro.
4.8.2. Processing
Managers
o Store the MID for each ADM-defined Macro definition.
o Send requests to Agents to add, list, describe, and remove custom
Macro definitions.
o Encode macro MIDs in Controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined Macro definition.
o Remember custom Macro definitions and run Macros when appropriate,
such as when responding to a run-Macro Control or when executing
the action of a TRL or SRL.
o Add, remove, list, and describe custom Macro definitions.
4.9. Literal
Literals in the AMP represent constants defined in an ADM. Examples
of constants that could be defined in an ADM include common
mathematical values such as PI or well-known Epochs such as the UNIX
Epoch.
The ADM definition of a Literal MUST include the type of the Literal
value. Since ADM definitions are preconfigured on Agents and
Managers in an AMA the type information for a given Literal is
therefore known by all actors in the system.
If the MID identifying the Literal encapsulates a non-parameterized
OID, then the value is given in the ADM and Agents and Managers can
lookup this value in their set of pre-configured data.
If the MID identifying the Literal encapsulates a parameterized OID,
then the parameters to the OID define the value of the Literal.
Users wishing to create a new Literal will create a MID with whatever
parameters are necessary to create the value. The documentation of
the ADM defining the Literal MUST describe how parameters result in
the calculation of the Literal value.
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4.9.1. Definition
The format of a Literal is illustrated in Figure 23.
+-------+
| ID |
| [MID] |
+-------+
Figure 23: Control Format
ID
This is the MID identifying the Literal. Since Literal
definitions are always provided in an ADM, this MID MUST NOT
have an ISSUER field and MUST NOT have a TAG field.
4.9.2. Processing
Managers
o Store the MID for each ADM-defined Literal definition.
o Encode Literal MIDs in controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined Literal definition.
o Calculate the value of Literals where appropriate, such as when
generating a Report Entry or when evaluating an Expression.
4.10. Operator
Operators in the AMP 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 MID 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 would
accept 10 parameters.
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4.10.1. Definition
Operators are always evaluated in the context of an Expression. The
format of an Operator is illustrated in Figure 24.
+-------+
| ID |
| [MID] |
+-------+
Figure 24: Operator Format
ID
This is the MID identifying the Operator. Since Operators
are always defined solely in the context of an ADM, this MID
MUST NOT have an ISSUER field and MUST NOT have a TAG field.
4.10.2. Processing
Managers
o Store the MID for each ADM-defined Operator definition.
o Encode Operator MIDs in Controls to Agents, as appropriate.
Agents
o Store the MID for each ADM-defined Operator definition.
o Store the number of parameters expected for each Operator.
o Calculate the value of applying an Operator to a given set of
parameters, such as when evaluating an Expression.
5. Data Type IDs and Enumerations
This section lists the IDs and enumerations for data types outlined
in this section. IDs are the text abbreviations used in this
specification and in ADMs to identify data types. Enumerations
associate data types with a numeric value. These enumerations MUST
be used whenever a data type is represented as a numerical
representation.
NOTE: Type enumerations are always represented as a BYTE in the AMP.
IDs and enumerations are grouped by the kind of data they represent,
as follows. AMP structure identifiers occupy enumerations 0 - 8 and
represent AMP data structures that are formally identified by a MID.
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Basic data types occupy enumerations 9-18 and represent primitive
data types in the AMP specification. Compound and special types
occupy enumerations 19-25 and represent other data types known to the
AMP specification.
AMP Structure ID Enumeration Numeric
------------------------------- -------------- ----------- ----------
Externally Defined Data EDD 0 No
Variable VAR 1 No
Report RPT 2 No
Control CTRL 3 No
State-Based Rule SRL 4 No
Time-Based Rule TRL 5 No
Macro MACRO 6 No
Literal LIT 7 No
Operator OP 8 No
Basic Data Type ID Enumeration Numeric
------------------------------- -------------- ----------- ----------
BYTE BYTE 9 No
Signed 32-bit Integer INT 10 Yes
Unsigned 32-bit Integer UINT 11 Yes
Signed 64-bit Integer VAST 12 Yes
Unsigned 64-bit Integer UVAST 13 Yes
Single-Precision Floating Point REAL32 14 Yes
Double-Precision Floating Point REAL64 15 Yes
Self-Delineating Numerical SDNV 16 No
Value
Timestamp TS 17 No
Character String STR 18 No
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Compound/Special Data Type ID Enumeration Numeric
------------------------------- -------------- ----------- ----------
Binary Large Object BLOB 19 No
Managed Identifier MID 20 No
MID Collection MC 21 No
Expression EXPR 22 No
Data Collection DC 23 No
Typed Data Collection TDC 24 No
Table TBL 25 No
5.1. Numeric Promotions
When attempting to evaluate operators of different types, wherever
possible, an Agent MAY need to promote operands until they are of the
correct type. For example, if an Operator is given both an INT and a
REAL32, the INT SHOULD be promoted to a REAL32 before the Operator is
applied.
The listing of legal promotions in the AMP are listed in Figure 25.
In this Figure, operands are listed across the top row and down the
first column. The resultant type of the promotion is listed in the
table at their intersection.
INT UINT VAST UVAST REAL32 REAL64
+--------+--------+--------+--------+--------+--------+
INT | INT | INT | VAST | UNK | REAL32 | REAL64 |
UINT | INT | UINT | VAST | UVAST | REAL32 | REAL64 |
VAST | VAST | VAST | VAST | VAST | REAL32 | REAL64 |
UVAST | UNK | UVAST | VAST | UVAST | REAL32 | REAL64 |
REAL32 | REAL32 | REAL32 | REAL32 | REAL32 | REAL32 | REAL64 |
REAL64 | REAL64 | REAL64 | REAL64 | REAL64 | REAL64 | REAL64 |
+--------+--------+--------+--------+--------+--------+
Figure 25: AMP Numeric Promotions
AMP does not permit promotions between non-numeric types, and numeric
promotions not listed in this section are not allowed in the AMP.
Any attempt to perform an illegal promotion in the AMP SHOULD result
in an error.
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5.2. Numeric Conversions
Variables, Expressions, and Predicates in the AMP are typed values.
When attempting to assign a value of a different type, a numeric
conversion must be performed. Any numeric type may be converted to
any other numeric type in accordance with the C rules for arithmetic
type conversions.
6. Application Data Model Template
6.1. Overview
An application data model (ADM) specifies the set of AMP components
associated with a particular application or protocol. The purpose of
the ADM is to provide a guaranteed interface for the management of an
application or protocol over AMP that is independent of the nuances
of its software implementation. In this respect, the ADM is
conceptually similar to the Managed Information Base (MIB) used by
SNMP, but contains additional information relating to command opcodes
and more expressive syntax for automated behavior.
Any implementation claiming compliance with a given ADM must collect
all identified EDDs, compute all identified Variables, perform
identified Controls and Macros, generate Report Entries to defined
Report Templates, and understand identified Literals and Operators.
6.2. Template
Each ADM specifies the globally unique identifiers and descriptions
for all EDDs, Variables, Controls, Literals, Macros, Report
Templates, and Operators associated with the application or protocol
managed by the ADM.
6.2.1. ADM Metadata
ADM metadata consist of the items necessary to uniquely identify the
ADM itself. The required metadata items include the following.
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+-------------+--------+-------------------------------------+------+
| Item | Type | Description | Req. |
+-------------+--------+-------------------------------------+------+
| Name | STR | The human-readable name of the ADM. | Y |
| | | | |
| Version | STR | Version of the ADM encoded as a | Y |
| | | string. | |
| | | | |
| OID | OID | ADMs provide an ordered list of | N |
| Nickname N | | nicknames that can be used by other | |
| | | MIDs in the ADM definition to | |
| | | defined compressed OIDs. There can | |
| | | an arbitrary number of nicknames | |
| | | defined for an ADM. | |
+-------------+--------+-------------------------------------+------+
Table 2: ADM Terminology
6.2.2. ADM Information Capture
The ADM Data Section consist of all components in the "data" category
associated with the managed application or protocol. The information
that must be provided for each of these items is as follows.
Name
Every component in an ADM MUST be given a human-readable,
consistent name that uniquely identifies the component in the
context of the application or protocol. These names will be used
by human-computer interfaces for manipulating components.
MID
The managed identifier that describes this data item. MIDs in
components identified by an ADM MUST NOT contain an ISSUER field
and MUST NOT contain a TAG field. In cases where the OID is
parameterized, the parameter values are not included in the ADM
MID definition as parameters are provided at runtime.
OID
A human-readable version of the OID encapsulated in the MID for
the component (e.g., 1.2.3.4). When a nickname is used to
represent an compressed OID, the nickname enumeration is included
in this field enclosed by square brackets. For example, if OID
nickname 0 refers to the OID prefix 1.2.3.4.5, then the OID
1.2.3.4.5.6 may be listed more compactly as [0].6
Description
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Every component in an ADM MUST be given a human-readable,
consistent description that provides a potential user with a
compact, effective summary of the item.
Type
For components that evaluate to a data value, the data type for
that value must be represented.
# Parameters
For components with a parameterized OID, the ADM MUST provide the
expected number of parameters. A value of 0 indicates that the
OID has no parameters and MUST NOT be used for any MID which has a
parameterized OID. When omitted, the number of parameters is
considered 0.
Parameter N Name
Each parameter of a parameterized component must be given a name.
Parameter N Description
Each parameter of a parameterized component must be given a
summary that describes how the parameter will be used by the
application or protocol. This description MUST note if the
parameter is optional.
Parameter N Type
Each parameter of a parameterized component must be given a type
that describes the structure capturing the parameter value.
6.3. The Agent ADM
The full set of EDDs, Variables, Report Templates, Controls, Rules,
Macros, Literals, and Operators that can be understood by an AMP
Agent have been separated into an AMP Agent ADM. Just as the AMP
uses ADMs to manage applications and protocols, the ADM model is also
used to implement the functionality of the Agent.
7. Functional Specification
This section describes the format of the messages that comprise the
AMP protocol. The AMP message specification is limited to three
basic communications:
- Adding an Agent to the list of managed devices known to a
Manager.
- Sending a Macro of one or more Controls to an Agent.
- Receiving a Report of one or more Report Entries from an Agent.
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The entire management of a network can be performed using these three
messages and the configurations from associated ADMs.
7.1. 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 26. These message groups are
assumed communicated amongst Agents and Managers as the payloads of
encapsulating protocols which MAY provide additional security and
data integrity features.
+--------+-----------+-----------+ +-----------+
| # Msgs | Timestamp | Message 1 | ... | Message N |
| [SDNV] | [TS] | [VARIES] | | [VARIES] |
+--------+-----------+-----------+ +-----------+
Figure 26: AMP Message Group Format
# Msgs
The number of messages that are together in this message
group.
Timestamp
The creation time for this messaging group. This timestamp
MUST be an absolute time. Individual messages may have their
own creation timestamps based on their type, but the group
timestamp also serves as the default creation timestamp for
every message in the group.
Message N
The Nth message in the group.
7.2. Message Format
Each message identified in the AMP specification adheres to a common
message format, illustrated in Figure 27, consisting of a message
header, a message body, and an optional trailer.
+--------+----------+----------+
| Header | Body | Trailer |
| [BYTE] | [VARIES] | [VARIES] |
| | | (opt.) |
+--------+----------+----------+
Figure 27: AMP Message Format
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Header
The message header BYTE is shown in Figure 28. The header
identifies a message context and opcode as well as flags that
control whether a Report Entry should be generated on message
success (Ack) and whether a Report Entry should be generated
on message failure (Nack).
+--------+----+---+-----------+
|ACL Used|Nack|Ack| Opcode |
+--------+----+---+-----------+
| 7 | 6 | 5 | 4 3 2 1 0 |
+--------+----+---+-----------+
MSB LSB
Figure 28: AMP Common Message Header
Opcode
The opcode field identifies the opcode of the
message.
ACK Flag
The ACK flag describes whether successful application
of the message must generate an acknowledgement back
to the message sender. If this flag is set (1) then
the receiving actor MUST generate a Report Entry
communicating this status. Otherwise, the actor MAY
generate such a Report Entry based on other criteria.
NACK Flag
The NACK flag describes whether a failure applying
the message must generate an error notice back to the
message sender. If this flag is set (1) then the
receiving Actor MUST generate a Report Entry
communicating this status. Otherwise, the Actor MAY
generate such a Report Entry based on other criteria.
ACL Used Flag
The ACL used flag indicates whether the message has a
trailer associated with it that specifies the list of
AMP actors that may participate in the Actions or
definitions associated with the message. This area
is still under development.
Body
The message body contains the information associated with the
given message.
Trailer
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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.
7.3. Register Agent (0x00)
The Register Agent message is used to inform an AMP Manager of the
presence of another Agent in the network.
+----------+
| Agent ID |
| [BLOB] |
+----------+
Figure 29: Register Agent Message Body
Agent ID
The Agent ID MUST represent the unique address of the Agent
in whatever protocol is used to communicate with the Agent.
7.4. Data Report (0x12)
Reports capture information generated by Agents and transmitted to
Managers in the AMP. Since the AMP is an asynchronous protocol there
is no explicit association between the contents of a Report and a
generating action by either a Manager or an Agent.
Reports are an ordered collection of Report Entries collected from a
managed device.
+------+---------+-----------+---------+ +---------+
| Time | RX Name | # Entries | ENTRY 1 | | ENTRY N |
| [TS] | [BLOB] | [SDNV] | [RPTE] |...| [RPTE] |
+------+---------+-----------+---------+ +---------+
Figure 30: Data Report Message Body
Time
The time at which the Report was generated by the AMP Actor.
RX Name
The identifier of the Manager meant to receive this report.
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# Entries
The number of Report Entries in the Report.
ENTRY N
The Nth Report Entry.
7.5. Perform Control (0x1A)
The perform control message causes the receiving AMP Actor to run one
or more pre-configured Controls provided in the message.
+-------+-----------+
| Start | Controls |
| [TS] | [MC] |
+-------+-----------+
Figure 31: Perform Control Message Body
Start
The time at which the Controls/Macros should be run.
Controls
The collection of MIDs that represent the Controls and/or
Macros to be run by the AMP Actor.
8. IANA Considerations
At this time, this protocol has no fields registered by IANA.
However, such a registry MUST be established to capture certain data
elements provided in ADMs, such as nicknames and root OIDs.
9. 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.
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10. References
10.1. Informative References
[AMA] Birrane, E., "Asynchronous Management Architecture",
draft-birrane-dtn-ama-00 (work in progress), August 2015.
[I-D.irtf-dtnrg-dtnmp]
Birrane, E. and V. Ramachandran, "Delay Tolerant Network
Management Protocol", draft-irtf-dtnrg-dtnmp-01 (work in
progress), December 2014.
10.2. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6256] Eddy, W. and E. Davies, "Using Self-Delimiting Numeric
Values in Protocols", RFC 6256, DOI 10.17487/RFC6256, May
2011, <http://www.rfc-editor.org/info/rfc6256>.
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 and has agreed to document the access control list and error
reporting portion of the specification.
Authors' Addresses
Edward J. Birrane
Johns Hopkins Applied Physics Laboratory
Email: Edward.Birrane@jhuapl.edu
Jeremy Pierce-Mayer
INSYEN AG
Muenchner Str. 20
Oberpfaffenhofen, Bavaria DE
Germany
Phone: +49 08153 28 2774
Email: jeremy.mayer@insyen.com
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