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Control Command

Control Command is a mechanism of 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 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 block wrapped in a NameComponent.
  • command-interest-components are four additional components defined by Command Interest spec.

ControlParameters

ControlParameters block contains arguments to the command.

ControlParameters   ::= CONTROL-PARAMETERS-TYPE TLV-LENGTH
                          Name?
                          FaceId?
                          Uri?
                          LocalUri?
                          Origin?
                          Cost?
                          Flags?
                          Mask?
                          Strategy?
                          ExpirationPeriod?
                          FacePersistency?

; 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

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

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.

Response format

A response from the command interface is a Data that matches the request Interest.
The payload of this Data is a ControlResponse block.

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 blocks

StatusCode

StatusCode loosely follows the HTTP semantics described in RFC 7231.

  • 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
Flags 108 0x6c
Mask 112 0x70
Strategy 107 0x6b
ExpirationPeriod 109 0x6d
ControlResponse 101 0x65
StatusCode 102 0x66
StatusText 103 0x67
(reserved, formerly LocalControlFeature) 110 0x6e