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Revision 48 (Ju Pan, 06/03/2019 01:53 PM) → Revision 49/53 (Ju Pan, 06/05/2019 01:23 PM)
# Control Command
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**Control Command** is a mechanism of [[Management|NFD Management protocol]]. This mechanism is useful for altering the state of the forwarder.
This document defines the request and response format of such commands, and how they should be signed and authenticated.
## Request format
Control commands are [[ndn-cxx:CommandInterest|Command Interests]] under a NFD management prefix.
The Name for a request Interest has the following form:
/<prefix>/<management-module>/<command-verb>/<control-parameters>/<command-interest-components>
* *prefix* is a NFD management prefix.
Unless otherwise noted, all commands use `/localhost/nfd` prefix.
Each individual command MAY specify additional prefixes under which that command could be accepted.
* *management-module* is the name of management module to which the command needs to be dispatched.
* *command-verb* is the command to be executed.
* *control-parameters* is a ControlParameters TLV element wrapped in a NameComponent.
* *command-interest-components* are four additional components defined by [[ndn-cxx:CommandInterest|Command Interest]] spec.
### ControlParameters
ControlParameters element contains arguments to the command.
ControlParameters ::= CONTROL-PARAMETERS-TYPE TLV-LENGTH
Name?
FaceId?
Uri?
LocalUri?
Origin?
Cost?
Capacity?
Count?
BaseCongestionMarkingInterval?
DefaultCongestionThreshold?
Mtu?
Flags?
Mask?
Strategy?
ExpirationPeriod?
FacePersistency?
EndpointId?
; Name is defined in NDN packet format specification
FaceId ::= FACE-ID-TYPE TLV-LENGTH
nonNegativeInteger
Uri ::= URI-TYPE TLV-LENGTH
RFC3986 URI in UTF-8 encoding
LocalUri ::= LOCAL-URI-TYPE TLV-LENGTH
RFC3986 URI in UTF-8 encoding
Origin ::= ORIGIN-TYPE TLV-LENGTH
nonNegativeInteger
Cost ::= COST-TYPE TLV-LENGTH
nonNegativeInteger
Capacity ::= CAPACITY-TYPE TLV-LENGTH
nonNegativeInteger
Count ::= COUNT-TYPE TLV-LENGTH
nonNegativeInteger
BaseCongestionMarkingInterval ::= BASE-CONGESTION-MARKING-INTERVAL-TYPE TLV-LENGTH
nonNegativeInteger
DefaultCongestionThreshold ::= DEFAULT-CONGESTION-THRESHOLD-TYPE TLV-LENGTH
nonNegativeInteger
Mtu ::= MTU-TYPE TLV-LENGTH
nonNegativeInteger
Flags ::= FLAGS-TYPE TLV-LENGTH
nonNegativeInteger
Mask ::= MASK-TYPE TLV-LENGTH
nonNegativeInteger
Strategy ::= STRATEGY-TYPE TLV-LENGTH
Name
ExpirationPeriod ::= EXPIRATION-PERIOD-TYPE TLV-LENGTH
nonNegativeInteger
; FacePersistency is defined in FaceMgmt section
EndpointId ::= ENDPOINTID-TYPE TLV-LENGTH
nonNegativeInteger
This definition exhausts all possible fields used in existing commands.
Each individual command MUST specify:
* a list of required fields: those fields MUST be present
* a list of optional fields: those fields MAY be present
* the semantics of each required and optional field
A field that is neither required nor optional for a command MUST NOT be present in a ControlParameter given to that command.
Each individual command MAY impose additional constraints on certain fields.
### Flags and Mask
Various commands collect multiple boolean attributes into the **Flags** field as an inclusive OR.
Each individual command that uses the Flags field MUST define the meaning of each bit. In the definition, "bit 0" refers to the least significant bit.
The **Mask** field, if accepted by a command, indicates which attributes are being updated.
In such cases, Flags field and Mask field must be both present or both omitted in the request.
Bits in the Mask field are arranged in the same order as the Flags field.
For example, if a command defines two flags at bit 0 and bit 1 and also accepts a Mask field, a request containing "Flags=0x02 Mask=0x02" specifies bit 1 as "true" and specifies bit 0 as "don't care, leave at default, or keep unchanged"; this request is equivalent to a request containing "Flags=0x03 Mask=0x02".
If a command does not accept the **Mask** field, it SHOULD interpret every bit in Flags, and there is no "don't care" bits.
## Response format
A response from the command interface is a Data that matches the request Interest.
The payload of this Data is a ControlResponse element.
ControlResponse ::= CONTROL-RESPONSE-TYPE TLV-LENGTH
StatusCode
StatusText
<body>
StatusCode ::= STATUS-CODE-TYPE TLV-LENGTH
nonNegativeInteger
StatusText ::= STATUS-TEXT-TYPE TLV-LENGTH
string in UTF-8
<body> ::= zero or more arbitrary TLV elements
### StatusCode
StatusCode loosely follows the HTTP semantics described in [RFC 7231](https://tools.ietf.org/html/rfc7231#section-6).
* Codes between 100 and 399 represent a success.
* Codes between 400 and 499 represent a client error.
* Codes between 500 and 599 represent a server error.
Common codes include:
StatusCode | Description
-----------|------------------------
200 | OK
400 | ControlParameters is incorrect
403 | Command Interest is not authorized
404 | Resource (e.g., face, prefix, ...) not found
501 | Module or verb is not supported
503 | Service not available
Each individual command MAY define additional codes.
### \<body>
Additional elements are allowed at the end of ControlResponse.
Each individual command MAY define the type and meaning of \<body>.
Unless otherwise defined by an individual command,
\<body> is the ControlParameters passed into this command for all successful responses,
and \<body> is empty for all failure responses.
## TLV-TYPE assignments
Type | Assigned value | Assigned value (hex)
------------------------------------------- | ----------------- | --------------------
ControlParameters | 104 | 0x68
FaceId | 105 | 0x69
Uri | 114 | 0x72
LocalUri | 129 | 0x81
Origin | 111 | 0x6f
Cost | 106 | 0x6a
Capacity | 131 | 0x83
Count | 132 | 0x84
BaseCongestionMarkingInterval | 135 | 0x87
DefaultCongestionThreshold | 136 | 0x88
Mtu | 137 | 0x89
Flags | 108 | 0x6c
Mask | 112 | 0x70
Strategy | 107 | 0x6b
ExpirationPeriod | 109 | 0x6d
ControlResponse | 101 | 0x65
StatusCode | 102 | 0x66
StatusText | 103 | 0x67
EndpointId | 113 | 0x71
(reserved, formerly LocalControlFeature) | 110 | 0x6e