face-registration.rst - NDN-TLV - Gitiles

 .. _Face Registration:

 Face Management and Registration Protocol
 -----------------------------------------

 Face Management Protocol
 ^^^^^^^^^^^^^^^^^^^^^^^^

 The Face Management Protocol provides a method for an entity such as ndndc to control
 the faces maintained by ndnd, which are subsequently used in the Registration Protocol.

 The FMP supports ``newface``, ``destroyface``, and ``queryface`` operations.

 A request operation is represented as a NDN Interest with
 a NDN Data in NDN-TLV encoding, while the majority of the request parameters embedded
 as a component of the Interest name.
 A response is represented as a Data for which the name matches the Interest,
 and the content encodes any necessary response data.

 For the Face Management Protocol, the content of the Data packet is FaceInstance object
 as defined below.

 For example, the following steps necessary to create a new face:

 - Create NDN-TLV encoded FaceInstance object, containing action ``newface`` and other
   necessary fields to set up the face (e.g., ``IPProto``, ``Host``, ``Port``).

 - Create NDN-TLV encoded Data packet (``<NFBLOB>``), whose content is the encoded
   FaceInstance object

 - Express an Interest ``/ndnx/<NDNDID>/newface/<NFBLOB>``, where

   * ``<NDNDID>`` is the SHA256 of the public key of the forwarding daemon.

   * ``<NFBLOB>`` is encoded Data packet with encoded FaceInstance object as content.

 The verb, ``newface`` occurs redundantly in both the Interest prefix and in the ``NFBLOB``.
 Its presence in the prefix is for dispatching the request.
 It is also in the ``NFBLOB``, so that it is signed.

 The forwarding daemon creates the new face and answers with a FaceInstance containing
 at least the ``FaceID``.

 .. note::
     When face registration succeeds, the returning Data packet's content is encoded ``FaceInstance`` with
     parameters of the created/destroyed/queried face.

     When registration fails, the Interest either times out or there will be a returned Data packet
     with encoded :ref:`StatusResponse`.


 FaceInstance
 ^^^^^^^^^^^^

 ::

     FaceInstance ::= FACE-INSTANCE-TYPE TLV-LENGTH
                        Action?
                        FaceID?
                        IPProto?
                        Host?
                        Port?
                        MulticastInterface?
                        MulticastTTL?
                        FreshnessPeriod?

     Action             ::= ACTION-TYPE TLV-LENGTH
                             ("newface" | "destroyface" | "queryface")

     FaceID             ::= FACEID-TYPE TLV-LENGTH
                              nonNegativeInteger

     IPProto            ::= FACEID-TYPE TLV-LENGTH
                              nonNegativeInteger
                        (*IANA protocol number; 6=TCP, 17=UDP*)

     Host               ::= HOST-TYPE TLV-LENGTH
                              <textual representation of numeric IPv4 or IPv6 address>

     Port               ::= PORT-TYPE TLV-LENGTH
                              nonNegativeInteger
                        (* from the range [1..65535] *)

     MulticastInterface ::= MULTICAST-INTERFACE-TYPE TLV-LENGTH
                              <textual representation of numeric IPv4 or IPv6 address>

     MulticastTTL       ::= MULTICAST-TTL-TYPE TLV-LENGTH
                              nonNegativeInteger
                        (* from the range [1..255] *)

 See :ref:`Data packet's meta info description <MetaInfo>` for definition of ``FreshnessPeriod``.

 Action
 ++++++

 When FaceInstance is used as a request, the Action must be specified.
 It will not be present in a response.

 +-----------------+----------------------------------------------------------------------+
 | Action          | Description                                                          |
 +=================+======================================================================+
 | ``newface``     | If a face matching the parameters does not already exist, an attempt |
 |                 | is made to create it.                                                |
 |                 |                                                                      |
 |                 | Then if the face exists (whether new or old) the full description is |
 |                 | returned as a FaceInstance.                                          |
 +-----------------+----------------------------------------------------------------------+
 | ``destroyface`` | At least the FaceID must be present.                                 |
 |                 | If permitted, the face is destroyed.                                 |
 +-----------------+----------------------------------------------------------------------+
 | ``queryface``   | TBD                                                                  |
 +-----------------+----------------------------------------------------------------------+

 FaceID
 ++++++

 FaceID is not present in a `newface` request, but must be specified in
 a `destroyface` or `queryface` request.
 FaceID is always present in a response.

 Host
 ++++

 Identifies the IPv4 or IPv6 numeric address of the remote ndnd for this
 FaceInstance.

 Port
 ++++

 Port identifies the port on the remote ndnd, or the port for the multicast group.

 MulticastInterface
 ++++++++++++++++++

 If the Host is a multicast address, and there are multiple
 interfaces present, MulticastInterface will identify the unicast
 numeric address of the interface to which the multicast address will be
 attached.

 MulticastTTL
 ++++++++++++

 Specifies the TTL to be used for multicast operations.  The default value is 1.

 FreshnessPeriod
 ++++++++++++++++

 FreshnessPeriod is optional in a request, but is treated as a hint by the forwarding daemon.
 In a response, FreshnessPeriod specifies the remaining lifetime in milliseconds of the
 face.

 Prefix Registration Protocol
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 The prefix registration protocol uses the ForwardingEntry element type
 to represent both requests and responses.

 ::

     ForwardingEntry ::= FORWARDING-ENTRY TLV-LENGTH
                           Action?
                           Name?
                           FaceID?
                           ForwardingFlags?
                           FreshnessPeriod?

     Action          ::= ACTION-TYPE TLV-LENGTH
                           ("prefixreg" | "selfreg" | "unreg")

     FaceID          ::= FACEID-TYPE TLV-LENGTH
                           nonNegativeInteger

     ForwardingFlags ::= FORWARDING-FLAGS TLV-LENGTH
                           nonNegativeInteger

 See :ref:`Name section <Name>` for definition of ``Name`` and
 :ref:`Data packet's meta info description <MetaInfo>` for definition of ``FreshnessPeriod``.

 .. note::
     When prefix registration succeeds, the returning Data packet's content is encoded ``ForwardingEntry`` with
     parameters of the prefix.

     When registration fails, the Interest either times out or there will be a returned Data packet
     with encoded :ref:`StatusResponse`.


 Action
 ++++++

 When ForwardingEntry is used as a request, the Action must be specified.
 It will not be present in a response.

 - `prefixreg` - Register (or re-register) the prefix on the specified face.
 - `selfreg` - Register (or re-register) the prefix on the current face; the
   FaceID need not be present in the request, but if present it must match
   the current face.
 - `unreg` - Remove the prefix registration for the specified face.

 FaceID
 ++++++

 FaceID is required in `prefixreg` and `unreg` requests.
 FaceID is always present in a response.

 Name
 ++++

 This is the name prefix to be acted on.

 ForwardingFlags
 +++++++++++++++

 This integer holds the inclusive OR of the following bit fields:

 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | Flag mnemonic              | Bit (decimal) | Description                                                                 |
 +============================+===============+=============================================================================+
 | ``NDN_FORW_ACTIVE``        | 1             | Indicates that the entry is active;                                         |
 |                            |               | interests will not be sent for inactive entries (but see note below).       |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_CHILD_INHERIT`` | 2             | Denotes that this entry may be used even if there is a longer match         |
 |                            |               | available.  In the absence of this bit, the presence of a longer matching   |
 |                            |               | prefix that has an active entry will prevent this entry from being used.    |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_ADVERTISE``     | 4             | Indicates that the prefix may be advertised to other nodes.                 |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_LAST``          | 8             | Indicates that this entry should be used last, if nothing else worked.      |
 |                            |               | This is intended to be used by ndndc and similar programs to monitor        |
 |                            |               | unanswered interests.                                                       |
 |                            |               |                                                                             |
 |                            |               | The presence of this flag on any entry causes the associated face to be     |
 |                            |               | considered non-local, as far as interest forwarding is concerned.           |
 |                            |               | Thus it will not receive interests with Scope=1, nor will it receive        |
 |                            |               | interests in namespaces that are marked local.  However, the ability of     |
 |                            |               | the face to change prefix registrations is not affected.                    |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_CAPTURE``       | 16            | Says that no shorter prefix may be used, overriding child-inherit bits that |
 |                            |               | would otherwise make the shorter entries usable.                            |
 |                            |               |                                                                             |
 |                            |               | For a child-inherit bit to be overridden, the ``NDN_FORW_CAPTURE_OK`` must  |
 |                            |               | be set in the same forwarding entry that has ``NDN_FORW_CHILD_INHERIT``     |
 |                            |               | set.  Note that this means that using ``NDN_FORW_CAPTURE`` will have no     |
 |                            |               | effect if the ``NDN_FORW_CAPTURE_OK`` flag is not used.                     |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_LOCAL``         | 32            | Restricts the namespace to use by applications on the local machine.        |
 |                            |               |                                                                             |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_TAP``           | 64            | Causes the entry to be used right away.  This is intended for debugging     |
 |                            |               | and monitoring purposes.  It is likely that there will be no response as    |
 |                            |               | a result, so no intentional delay is added before any further forwarding    |
 |                            |               | of this interest.                                                           |
 +----------------------------+---------------+-----------------------------------------------------------------------------+
 | ``NDN_FORW_CAPTURE_OK``    | 128           | used in conjunction with ``NDN_FORW_CHILD_INHERIT`` allows a                |
 |                            |               | ``NDN_FORW_CAPTURE`` flag on a longer prefix to override the effect of      |
 |                            |               | the child-inherit bit.                                                      |
 +----------------------------+---------------+-----------------------------------------------------------------------------+

 The flags ``NDN_FORW_ADVERTISE``, ``NDN_FORW_CAPTURE`` and ``NDN_FORW_LOCAL`` affect
 the prefix as a whole, rather than the individual registrations.
 Their effects take place whether or not the ``NDN_FORW_ACTIVE`` bit is set.

 FreshnessPeriod
 +++++++++++++++

 FreshnessPeriod is optional in a request, but is treated as a hint by the forwarding daemon.
 In a response, FreshnessPeriod specifies the remaining lifetime in milliseconds of the registration.

 .. _StatusResponse:

 StatusResponse
 ^^^^^^^^^^^^^^

 The StatusResponse is used to indicate an exceptional condition or
 additional information in response to a request.
 Protocol descriptions should indicate the circumstances under which a
 StatusResponse may be returned instead of a normal response.

 ::

     StatusResponse ::= STATUS-RESPONSE-TYPE TLV-LENGTH
                          StatusCode
                          StatusText?

     StatusCode         ::= STATUS-CODE-TYPE TLV-LENGTH
                              nonNegativeInteger

     StatusText         ::= STATUS-TEXT TLV-LENGTH
                              <status text>

 StatusCode
 ++++++++++

 This is a three-digit decimal number, in the style of numeric codes
 used in various internet protocols such as HTTP, FTP, and SMTP.

 StatusText
 ++++++++++

 A short textual description of the status.
 Programs should rely on the StatusCode, not the StatusText, for making decisions about haw to proceed.

 Status Code Values
 ++++++++++++++++++

 This table is informational, summarizing status codes that are currently is use.

 +--------+--------------------------------------------------------+
 |  Code  |  Description                                           |
 +========+========================================================+
 |   404  | Not found                                              |
 +--------+--------------------------------------------------------+
 |   430  | Not authorized                                         |
 +--------+--------------------------------------------------------+
 |   450  | Temporarily unable to complete operation               |
 +--------+--------------------------------------------------------+
 |   453  | Could not setup multicast                              |
 +--------+--------------------------------------------------------+
 |   501  | Syntax error in address                                |
 +--------+--------------------------------------------------------+
 |   504  | Parameter error                                        |
 +--------+--------------------------------------------------------+
 |   531  | Missing or incorrect ccndid                            |
 +--------+--------------------------------------------------------+


 Type code assignment
 ^^^^^^^^^^^^^^^^^^^^

 Face management and registration protocol uses the following type codes, which are assigned
 from the :ref:`application range (128-252) <type reservations>`.

 Some codes (e.g., `Name`, `FreshnessPeriod`), re-use code assignment from the NDN-TLV specification.

 +---------------------------------------------+-------------------+----------------+
 | Type                                        | Assigned value    | Assigned value |
 |                                             | (decimal)         | (hexadecimal)  |
 +=============================================+===================+================+
 | **Application-specific definitions**                                             |
 +---------------------------------------------+-------------------+----------------+
 | FaceInstance                                | 128               | 0x80           |
 +---------------------------------------------+-------------------+----------------+
 | ForwardingEntry                             | 129               | 0x81           |
 +---------------------------------------------+-------------------+----------------+
 | StatusResponse                              | 130               | 0x82           |
 +---------------------------------------------+-------------------+----------------+
 | Action                                      | 131               | 0x83           |
 +---------------------------------------------+-------------------+----------------+
 | FaceID                                      | 132               | 0x84           |
 +---------------------------------------------+-------------------+----------------+
 | IPProto                                     | 133               | 0x85           |
 +---------------------------------------------+-------------------+----------------+
 | Host                                        | 134               | 0x86           |
 +---------------------------------------------+-------------------+----------------+
 | Port                                        | 135               | 0x87           |
 +---------------------------------------------+-------------------+----------------+
 | MulticastInterface                          | 136               | 0x88           |
 +---------------------------------------------+-------------------+----------------+
 | MulticastTTL                                | 137               | 0x89           |
 +---------------------------------------------+-------------------+----------------+
 | ForwardingFlags                             | 138               | 0x8a           |
 +---------------------------------------------+-------------------+----------------+
 | StatusCode                                  | 139               | 0x8b           |
 +---------------------------------------------+-------------------+----------------+
 | StatusText                                  | 140               | 0x8c           |
 +---------------------------------------------+-------------------+----------------+
 | **Re-used definitions**                                                          |
 +---------------------------------------------+-------------------+----------------+
 | FreshnessPeriod                             | 20                | 0x14           |
 +---------------------------------------------+-------------------+----------------+
 | Name                                        | 2                 | 0x02           |
 +---------------------------------------------+-------------------+----------------+
	.. _Face Registration:

	Face Management and Registration Protocol
	-----------------------------------------

	Face Management Protocol
	^^^^^^^^^^^^^^^^^^^^^^^^

	The Face Management Protocol provides a method for an entity such as ndndc to control
	the faces maintained by ndnd, which are subsequently used in the Registration Protocol.

	The FMP supports ``newface``, ``destroyface``, and ``queryface`` operations.

	A request operation is represented as a NDN Interest with
	a NDN Data in NDN-TLV encoding, while the majority of the request parameters embedded
	as a component of the Interest name.
	A response is represented as a Data for which the name matches the Interest,
	and the content encodes any necessary response data.

	For the Face Management Protocol, the content of the Data packet is FaceInstance object
	as defined below.

	For example, the following steps necessary to create a new face:

	- Create NDN-TLV encoded FaceInstance object, containing action ``newface`` and other
	necessary fields to set up the face (e.g., ``IPProto``, ``Host``, ``Port``).

	- Create NDN-TLV encoded Data packet (``<NFBLOB>``), whose content is the encoded
	FaceInstance object

	- Express an Interest ``/ndnx/<NDNDID>/newface/<NFBLOB>``, where

	* ``<NDNDID>`` is the SHA256 of the public key of the forwarding daemon.

	* ``<NFBLOB>`` is encoded Data packet with encoded FaceInstance object as content.

	The verb, ``newface`` occurs redundantly in both the Interest prefix and in the ``NFBLOB``.
	Its presence in the prefix is for dispatching the request.
	It is also in the ``NFBLOB``, so that it is signed.

	The forwarding daemon creates the new face and answers with a FaceInstance containing
	at least the ``FaceID``.

	.. note::
	When face registration succeeds, the returning Data packet's content is encoded ``FaceInstance`` with
	parameters of the created/destroyed/queried face.

	When registration fails, the Interest either times out or there will be a returned Data packet
	with encoded :ref:`StatusResponse`.


	FaceInstance
	^^^^^^^^^^^^

	::

	FaceInstance ::= FACE-INSTANCE-TYPE TLV-LENGTH
	Action?
	FaceID?
	IPProto?
	Host?
	Port?
	MulticastInterface?
	MulticastTTL?
	FreshnessPeriod?

	Action ::= ACTION-TYPE TLV-LENGTH
	("newface" \| "destroyface" \| "queryface")

	FaceID ::= FACEID-TYPE TLV-LENGTH
	nonNegativeInteger

	IPProto ::= FACEID-TYPE TLV-LENGTH
	nonNegativeInteger
	(IANA protocol number; 6=TCP, 17=UDP)

	Host ::= HOST-TYPE TLV-LENGTH
	<textual representation of numeric IPv4 or IPv6 address>

	Port ::= PORT-TYPE TLV-LENGTH
	nonNegativeInteger
	(* from the range [1..65535] *)

	MulticastInterface ::= MULTICAST-INTERFACE-TYPE TLV-LENGTH
	<textual representation of numeric IPv4 or IPv6 address>

	MulticastTTL ::= MULTICAST-TTL-TYPE TLV-LENGTH
	nonNegativeInteger
	(* from the range [1..255] *)

	See :ref:`Data packet's meta info description <MetaInfo>` for definition of ``FreshnessPeriod``.

	Action
	++++++

	When FaceInstance is used as a request, the Action must be specified.
	It will not be present in a response.

	+-----------------+----------------------------------------------------------------------+
	\| Action \| Description \|
	+=================+======================================================================+
	\| ``newface`` \| If a face matching the parameters does not already exist, an attempt \|
	\| \| is made to create it. \|
	\| \| \|
	\| \| Then if the face exists (whether new or old) the full description is \|
	\| \| returned as a FaceInstance. \|
	+-----------------+----------------------------------------------------------------------+
	\| ``destroyface`` \| At least the FaceID must be present. \|
	\| \| If permitted, the face is destroyed. \|
	+-----------------+----------------------------------------------------------------------+
	\| ``queryface`` \| TBD \|
	+-----------------+----------------------------------------------------------------------+

	FaceID
	++++++

	FaceID is not present in a `newface` request, but must be specified in
	a `destroyface` or `queryface` request.
	FaceID is always present in a response.

	Host
	++++

	Identifies the IPv4 or IPv6 numeric address of the remote ndnd for this
	FaceInstance.

	Port
	++++

	Port identifies the port on the remote ndnd, or the port for the multicast group.

	MulticastInterface
	++++++++++++++++++

	If the Host is a multicast address, and there are multiple
	interfaces present, MulticastInterface will identify the unicast
	numeric address of the interface to which the multicast address will be
	attached.

	MulticastTTL
	++++++++++++

	Specifies the TTL to be used for multicast operations. The default value is 1.

	FreshnessPeriod
	++++++++++++++++

	FreshnessPeriod is optional in a request, but is treated as a hint by the forwarding daemon.
	In a response, FreshnessPeriod specifies the remaining lifetime in milliseconds of the
	face.

	Prefix Registration Protocol
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	The prefix registration protocol uses the ForwardingEntry element type
	to represent both requests and responses.

	::

	ForwardingEntry ::= FORWARDING-ENTRY TLV-LENGTH
	Action?
	Name?
	FaceID?
	ForwardingFlags?
	FreshnessPeriod?

	Action ::= ACTION-TYPE TLV-LENGTH
	("prefixreg" \| "selfreg" \| "unreg")

	FaceID ::= FACEID-TYPE TLV-LENGTH
	nonNegativeInteger

	ForwardingFlags ::= FORWARDING-FLAGS TLV-LENGTH
	nonNegativeInteger

	See :ref:`Name section <Name>` for definition of ``Name`` and
	:ref:`Data packet's meta info description <MetaInfo>` for definition of ``FreshnessPeriod``.

	.. note::
	When prefix registration succeeds, the returning Data packet's content is encoded ``ForwardingEntry`` with
	parameters of the prefix.

	When registration fails, the Interest either times out or there will be a returned Data packet
	with encoded :ref:`StatusResponse`.


	Action
	++++++

	When ForwardingEntry is used as a request, the Action must be specified.
	It will not be present in a response.

	- `prefixreg` - Register (or re-register) the prefix on the specified face.
	- `selfreg` - Register (or re-register) the prefix on the current face; the
	FaceID need not be present in the request, but if present it must match
	the current face.
	- `unreg` - Remove the prefix registration for the specified face.

	FaceID
	++++++

	FaceID is required in `prefixreg` and `unreg` requests.
	FaceID is always present in a response.

	Name
	++++

	This is the name prefix to be acted on.

	ForwardingFlags
	+++++++++++++++

	This integer holds the inclusive OR of the following bit fields:

	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| Flag mnemonic \| Bit (decimal) \| Description \|
	+============================+===============+=============================================================================+
	\| ``NDN_FORW_ACTIVE`` \| 1 \| Indicates that the entry is active; \|
	\| \| \| interests will not be sent for inactive entries (but see note below). \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_CHILD_INHERIT`` \| 2 \| Denotes that this entry may be used even if there is a longer match \|
	\| \| \| available. In the absence of this bit, the presence of a longer matching \|
	\| \| \| prefix that has an active entry will prevent this entry from being used. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_ADVERTISE`` \| 4 \| Indicates that the prefix may be advertised to other nodes. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_LAST`` \| 8 \| Indicates that this entry should be used last, if nothing else worked. \|
	\| \| \| This is intended to be used by ndndc and similar programs to monitor \|
	\| \| \| unanswered interests. \|
	\| \| \| \|
	\| \| \| The presence of this flag on any entry causes the associated face to be \|
	\| \| \| considered non-local, as far as interest forwarding is concerned. \|
	\| \| \| Thus it will not receive interests with Scope=1, nor will it receive \|
	\| \| \| interests in namespaces that are marked local. However, the ability of \|
	\| \| \| the face to change prefix registrations is not affected. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_CAPTURE`` \| 16 \| Says that no shorter prefix may be used, overriding child-inherit bits that \|
	\| \| \| would otherwise make the shorter entries usable. \|
	\| \| \| \|
	\| \| \| For a child-inherit bit to be overridden, the ``NDN_FORW_CAPTURE_OK`` must \|
	\| \| \| be set in the same forwarding entry that has ``NDN_FORW_CHILD_INHERIT`` \|
	\| \| \| set. Note that this means that using ``NDN_FORW_CAPTURE`` will have no \|
	\| \| \| effect if the ``NDN_FORW_CAPTURE_OK`` flag is not used. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_LOCAL`` \| 32 \| Restricts the namespace to use by applications on the local machine. \|
	\| \| \| \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_TAP`` \| 64 \| Causes the entry to be used right away. This is intended for debugging \|
	\| \| \| and monitoring purposes. It is likely that there will be no response as \|
	\| \| \| a result, so no intentional delay is added before any further forwarding \|
	\| \| \| of this interest. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+
	\| ``NDN_FORW_CAPTURE_OK`` \| 128 \| used in conjunction with ``NDN_FORW_CHILD_INHERIT`` allows a \|
	\| \| \| ``NDN_FORW_CAPTURE`` flag on a longer prefix to override the effect of \|
	\| \| \| the child-inherit bit. \|
	+----------------------------+---------------+-----------------------------------------------------------------------------+

	The flags ``NDN_FORW_ADVERTISE``, ``NDN_FORW_CAPTURE`` and ``NDN_FORW_LOCAL`` affect
	the prefix as a whole, rather than the individual registrations.
	Their effects take place whether or not the ``NDN_FORW_ACTIVE`` bit is set.

	FreshnessPeriod
	+++++++++++++++

	FreshnessPeriod is optional in a request, but is treated as a hint by the forwarding daemon.
	In a response, FreshnessPeriod specifies the remaining lifetime in milliseconds of the registration.

	.. _StatusResponse:

	StatusResponse
	^^^^^^^^^^^^^^

	The StatusResponse is used to indicate an exceptional condition or
	additional information in response to a request.
	Protocol descriptions should indicate the circumstances under which a
	StatusResponse may be returned instead of a normal response.

	::

	StatusResponse ::= STATUS-RESPONSE-TYPE TLV-LENGTH
	StatusCode
	StatusText?

	StatusCode ::= STATUS-CODE-TYPE TLV-LENGTH
	nonNegativeInteger

	StatusText ::= STATUS-TEXT TLV-LENGTH
	<status text>

	StatusCode
	++++++++++

	This is a three-digit decimal number, in the style of numeric codes
	used in various internet protocols such as HTTP, FTP, and SMTP.

	StatusText
	++++++++++

	A short textual description of the status.
	Programs should rely on the StatusCode, not the StatusText, for making decisions about haw to proceed.

	Status Code Values
	++++++++++++++++++

	This table is informational, summarizing status codes that are currently is use.

	+--------+--------------------------------------------------------+
	\| Code \| Description \|
	+========+========================================================+
	\| 404 \| Not found \|
	+--------+--------------------------------------------------------+
	\| 430 \| Not authorized \|
	+--------+--------------------------------------------------------+
	\| 450 \| Temporarily unable to complete operation \|
	+--------+--------------------------------------------------------+
	\| 453 \| Could not setup multicast \|
	+--------+--------------------------------------------------------+
	\| 501 \| Syntax error in address \|
	+--------+--------------------------------------------------------+
	\| 504 \| Parameter error \|
	+--------+--------------------------------------------------------+
	\| 531 \| Missing or incorrect ccndid \|
	+--------+--------------------------------------------------------+


	Type code assignment
	^^^^^^^^^^^^^^^^^^^^

	Face management and registration protocol uses the following type codes, which are assigned
	from the :ref:`application range (128-252) <type reservations>`.

	Some codes (e.g., `Name`, `FreshnessPeriod`), re-use code assignment from the NDN-TLV specification.

	+---------------------------------------------+-------------------+----------------+
	\| Type \| Assigned value \| Assigned value \|
	\| \| (decimal) \| (hexadecimal) \|
	+=============================================+===================+================+
	\| Application-specific definitions \|
	+---------------------------------------------+-------------------+----------------+
	\| FaceInstance \| 128 \| 0x80 \|
	+---------------------------------------------+-------------------+----------------+
	\| ForwardingEntry \| 129 \| 0x81 \|
	+---------------------------------------------+-------------------+----------------+
	\| StatusResponse \| 130 \| 0x82 \|
	+---------------------------------------------+-------------------+----------------+
	\| Action \| 131 \| 0x83 \|
	+---------------------------------------------+-------------------+----------------+
	\| FaceID \| 132 \| 0x84 \|
	+---------------------------------------------+-------------------+----------------+
	\| IPProto \| 133 \| 0x85 \|
	+---------------------------------------------+-------------------+----------------+
	\| Host \| 134 \| 0x86 \|
	+---------------------------------------------+-------------------+----------------+
	\| Port \| 135 \| 0x87 \|
	+---------------------------------------------+-------------------+----------------+
	\| MulticastInterface \| 136 \| 0x88 \|
	+---------------------------------------------+-------------------+----------------+
	\| MulticastTTL \| 137 \| 0x89 \|
	+---------------------------------------------+-------------------+----------------+
	\| ForwardingFlags \| 138 \| 0x8a \|
	+---------------------------------------------+-------------------+----------------+
	\| StatusCode \| 139 \| 0x8b \|
	+---------------------------------------------+-------------------+----------------+
	\| StatusText \| 140 \| 0x8c \|
	+---------------------------------------------+-------------------+----------------+
	\| Re-used definitions \|
	+---------------------------------------------+-------------------+----------------+
	\| FreshnessPeriod \| 20 \| 0x14 \|
	+---------------------------------------------+-------------------+----------------+
	\| Name \| 2 \| 0x02 \|
	+---------------------------------------------+-------------------+----------------+