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FaceMgmt » History » Version 107

Eric Newberry, 03/01/2020 11:05 PM

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# Face Management
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{{>toc}}
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**Face Management** is a module of [[Management|NFD Management protocol]].
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It provides:
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* commands to create, modify, and destroy faces
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* a dataset containing the description of all active faces and their counters
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* a dataset containing the description of all active channels
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* a notification stream for face events
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Face Management commands, datasets, and notifications are available under namespace `ndn:/localhost/nfd/faces`.
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## FaceUri
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A FaceUri represents the underlying protocol and address used by a Face.  
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Every Face has two FaceUris: one for local endpoint, and the other for remote endpoint.
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### UDP
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`udp[4|6]://<IP-or-host>[:<port>]`  
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Examples:
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* `udp4://192.0.2.1:6363` (canonical form)
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* `udp6://[2001:db8::1]:6363` (canonical form)
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* `udp6://[fe80::1068:dddb:fe26:fe3f%en0]:6363` (canonical form for link-local IPv6 addresses)
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* `udp6://[fe80::1068:dddb:fe26:fe3f%25en0]:6363` (equivalent, but not canonical, version of the above FaceUri)
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* `udp://192.0.2.1` (remote-port defaults to 6363)
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* `udp://example.net:6363`
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* `udp4://example.net:6363` (resolve hostname to IPv4 address only)
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* `udp6://example.net:6363` (resolve hostname to IPv6 address only)
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* `udp4://224.0.23.170:56363` (multicast, canonical form)
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LocalUri of a netdev-bound UDP face has the form:
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`udp[4|6]+dev://<interface-name>:<port>`
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This is only used in face dataset.
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Examples:
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* `udp4+dev://eth1:6363`
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* `udp6+dev://en0:6363`
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### TCP
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`tcp[4|6]://<IP-or-host>[:<port>]`
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Examples:
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* `tcp4://192.0.2.1:6363` (canonical form)
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* `tcp6://[2001:db8::1]:6363` (canonical form)
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* `tcp6://[fe80::1068:dddb:fe26:fe3f%en0]:6363` (canonical form for link-local IPv6 addresses)
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* `tcp6://[fe80::1068:dddb:fe26:fe3f%25en0]:6363` (equivalent, but not canonical, version of the above FaceUri)
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* `tcp://192.0.2.1` (remote-port defaults to 6363)
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* `tcp://example.net:6363`
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* `tcp4://example.net:6363` (resolve hostname to IPv4 address only)
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* `tcp6://example.net:6363` (resolve hostname to IPv6 address only)
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### UNIX stream
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`unix://<path>`
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Examples:
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* `unix:///var/run/nfd.sock` (note that there are three forward-slashes after 'unix:')
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### File descriptor
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`fd://<file-descriptor>`
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Examples:
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* `fd://6`
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### Ethernet
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`ether://[<MAC>]`
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Examples:
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* `ether://[08:00:27:01:01:01]`
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* `ether://[33:33:01:01:01:01]` (multicast)
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### Network device
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`dev://<interface-name>`
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Examples:
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* `dev://eth0`
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### Underlying protocol and FaceUri schemes
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Underlying protocol     | Remote FaceUri scheme            | Local FaceUri scheme
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----------------------- | -------------------------------- | --------------------------
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IPv4 UDP unicast        | udp4                             | udp4
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IPv6 UDP unicast        | udp6                             | udp6
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IPv4 UDP multicast      | udp4 (multicast group)           | udp4
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IPv6 UDP multicast      | udp6 (multicast group)           | udp6
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IPv4 UDP netdev-bound   | udp4                             | udp4+dev
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IPv6 UDP netdev-bound   | udp6                             | udp6+dev
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IPv4 TCP                | tcp4                             | tcp4
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IPv6 TCP                | tcp6                             | tcp6
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UNIX stream             | fd (file descriptor on NFD side) | unix (socket path)
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Ethernet unicast        | ether                            | dev
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Ethernet multicast      | ether                            | dev
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WebSocket               | wsclient                         | ws
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## Static Face Attributes
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**FaceScope** indicates whether the face is local for [[ScopeControl|scope control]] purposes.
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* non-local(=0)
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* local(=1)
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**FacePersistency** indicates whether the face is persistent.
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* on-demand(=1), face closes if it remains idle for some time
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* persistent(=0), face remains open until it's explicitly destroyed or there's a transport failure
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* permanent(=2), face remains open until it's explicitly destroyed; transport failures will be recovered internally
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**LinkType** indicates the type of communication link.
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* point-to-point(=0), communication with one peer
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* multi-access(=1), communication with a multicast group
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* ad-hoc(=2), communication over a wireless ad hoc network
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**LocalFieldsEnabled** indicates whether the face allows [[NDNLPv2]] NextHopFaceId, CachePolicy, IncomingFaceId fields.
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* yes(=1), allows these fields; this is valid only if FaceScope=local
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* no(=0), disallows these fields
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**LpReliabilityEnabled** indicates whether the face has the [[NDNLPv2]] reliability feature enabled.
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* yes(=1), enables this feature
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* no(=0), disables this feature
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**CongestionMarkingEnabled** indicates whether the face has congestion marking based upon send queue length enabled.
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* yes(=1), enables this feature
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* no(=0), disables this feature
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**BaseCongestionMarkingInterval** indicates the base marking interval for congestion marking.
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* The value of this attribute is the base marking interval in nanoseconds, which is used to compute the interval at which congested packets will be marked.
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**DefaultCongestionThreshold** indicates the default congestion threshold if the face does not support retrieving the send queue capacity.
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* The value of this attribute is the default congestion threshold in bytes.
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**Mtu** contains a user-specified MTU to override the automatic MTU of the transport.
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* The value of this attribute is the override MTU of the transport in bytes. The face will use the lesser of this value and the automatic MTU of the transport.
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### Flags and Mask
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Some attributes are collected as inclusive OR into a **Flags** field in commands and datasets.
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These attributes are: (bit 0 is the least significant bit)
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* bit 0: LocalFieldsEnabled
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* bit 1: LpReliabilityEnabled
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* bit 2: CongestionMarkingEnabled
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## Control Commands
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[[ControlCommand]] **management-module**: `faces`
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### Create a face
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**command-verb**: `create`
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ControlParameters fields:
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* **Uri** (required): canonical remote FaceUri of the face to create.
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* **LocalUri** (optional): canonical local FaceUri of the face to create; e.g., FaceUri of the local interface for an Ethernet unicast face.
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* **FacePersistency** (optional): either *persistent* or *permanent*; creating *on-demand* faces is not permitted. The default is *persistent*. See "static face attributes" for more information.
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* **BaseCongestionMarkingInterval** (optional): see "static face attributes".
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* **DefaultCongestionThreshold** (optional): see "static face attributes".
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* **Mtu** (optional): see "static face attributes".
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* **Flags** (optional): see "static face attributes".
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* **Mask** (optional): MUST be specified if *Flags* is present, and omitted if *Flags* is omitted.
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This command allows the creation of UDP unicast, Ethernet unicast, and TCP faces only.  
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If the command succeeds, the \<body> of the ControlResponse block contains the ControlParameters describing the current properties of the created face:
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* **FaceId**
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* **Uri**
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* **LocalUri**
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* **FacePersistency**
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* **BaseCongestionMarkingInterval** (optional)
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* **DefaultCongestionThreshold** (optional)
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* **Mtu** (optional)
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* **Flags**: contains effective values for the *LocalFieldsEnabled*, *LpReliabilityEnabled*, and *CongestionMarkingEnabled* bits.
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If this creation would conflict with an existing face (e.g., same underlying protocol and remote endpoint), the command fails with StatusCode 409, and the \<body> of the ControlResponse block contains the ControlParameters describing the existing face, with the same fields as above.
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If the request attempts to create a face other than UDP unicast, Ethernet unicast, or TCP, or if a static property specified in the request is not acceptable, the command fails with StatusCode 406.
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If face creation fails due to a socket error (e.g. TCP connection timeout), the command fails with StatusCode 504.
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If *BaseCongestionMarkingInterval* or *DefaultCongestionThreshold* are omitted from the ControlParameters sent with the creation command, the omitted static properties are left at their implementation-defined default values.
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If *Mtu* is omitted from the ControlParameters sent with the creation command, no override MTU is specified and the automatic MTU of the transport will be used. A forwarder MAY impose an implementation-defined minimum to the override MTU specified during face creation. The current minimum in NFD is 64 bytes. In the response, the *Mtu* field in ControlParameters contains the effective MTU of the face (in bytes), capped at a maximum of `MAX_NDN_PACKET_SIZE` (8800 bytes), even if the MTU of the underlying transport is infinite. If *Mtu* is omitted from the response, the face and/or forwarder does not support MTU reporting.
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### Update the static properties of a face
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**command-verb**: `update`
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ControlParameters fields:
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* **FaceId** (optional)
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* **FacePersistency** (optional): one of *on-demand*, *persistent*, or *permanent*. See "static face attributes" for more information.
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* **BaseCongestionMarkingInterval** (optional): see "static face attributes".
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* **DefaultCongestionThreshold** (optional): see "static face attributes".
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* **Mtu** (optional): see "static face attributes".
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* **Flags** (optional): allows *LocalFieldsEnabled*, *LpReliabilityEnabled*, and *CongestionMarkingEnabled* only. See "static face attributes" for more information.
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* **Mask** (optional): MUST be specified if *Flags* is present, and omitted if *Flags* is omitted.
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If *FaceId* is omitted or is set to zero, it is implied to be that of the requesting face (self-update).
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If the face does not exist, the command fails with StatusCode 404.
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The static properties of the face are updated as indicated.
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If an optional property field is omitted or a bitfield is zero in *Mask*, that static property remains unchanged.
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If no static properties are changed, this command does nothing, but is still considered successful.
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If the command succeeds, \<body> in ControlResponse block contains ControlParameters describing the current properties of the face:
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* **FaceId**
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* **FacePersistency**
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* **BaseCongestionMarkingInterval** (optional)
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* **DefaultCongestionThreshold** (optional)
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* **Mtu** (optional)
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* **Flags**: contains effective values for *LocalFieldsEnabled*, *LpReliabilityEnabled*, and *CongestionMarkingEnabled* bits.
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If any of the requested changes is invalid, none of the changes should be performed, and this command fails with StatusCode 409.
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The \<body> in ControlResponse block contains ControlParameters that includes only invalid fields; if some of the bit fields chosen in *Flags*+*Mask* is invalid, the \<body> block should also contain a *Mask* field indicating which bits are invalid, and echo back the original *Flags* field.
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If the request had been sent without those fields (or bitfields in *Mask*), it would have been successful.
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### Destroy a face
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**command-verb:** `destroy`
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ControlParameters fields:
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* **FaceId** (required)
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If the specified face does not exist, this command does nothing, but is still considered successful.
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## Face Dataset
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Description and counters of all active faces are published as a [[StatusDataset|Status Dataset]] at `ndn:/localhost/nfd/faces/list`.
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Each face is represented by a **FaceStatus** block:
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    FaceStatus      ::= FACE-STATUS-TYPE TLV-LENGTH
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                          FaceId
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                          Uri
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                          LocalUri
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                          ExpirationPeriod?
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                          FaceScope
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                          FacePersistency
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                          LinkType
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                          BaseCongestionMarkingInterval?
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                          DefaultCongestionThreshold?
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                          Mtu?
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                          NInInterests
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                          NInData
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                          NInNacks
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                          NOutInterests
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                          NOutData
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                          NOutNacks
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                          NInBytes
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                          NOutBytes
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                          Flags
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    Uri             ::= URI-TYPE TLV-LENGTH
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                          FaceUri in UTF-8 encoding
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    LocalUri        ::= LOCAL-URI-TYPE TLV-LENGTH
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                          FaceUri in UTF-8 encoding
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    ; other TLVs have nonNegativeInteger as value
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* **Uri** is a FaceUri representing remote endpoint.
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* **LocalUri** is a FaceUri representing local endpoint.
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* **ExpirationPeriod** is the remaining lifetime of this face.
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  If this field is omitted, the face has infinite lifetime.
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  Currently, this is applicable to on-demand datagram faces only.
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* **FaceScope** indicates whether the face is local for [[ScopeControl|scope control]] purposes.
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  See "static face attributes" for more information.
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* **FacePersistency** indicates whether the face is persistent.
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  See "static face attributes" for more information.
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* **LinkType** indicates the type of communication link
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  See "static face attributes" for more information.
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* **BaseCongestionMarkingInterval** indicates the base interval used to compute the interval at which congested packets will be marked (in nanoseconds).
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  See "static face attributes" for more information.
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* **DefaultCongestionThreshold** indicates the default threshold for congestion if the face does not support retrieving the send queue capacity (in bytes).
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  See "static face attributes" for more information.
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* **Mtu** contains the effective MTU of the face (in bytes), capped at `MAX_NDN_PACKET_SIZE` (8800 bytes), even if the MTU of the underlying transport is infinite. If this field is omitted, the forwarder and/or face does not support MTU reporting.
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  See "static face attributes" for more information.
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* **NInInterests**: number of incoming Interest packets since the face is established.
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* **NInData** counts the number of incoming Data packets since the face is established.
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* **NInNacks** counts the number of incoming Nack packets since the face is established.
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* **NOutInterests** counts the number of outgoing Interest packets since the face is established.
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* **NOutData** counts the number of outgoing Data packets since the face is established.
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* **NOutNacks** counts the number of outgoing Nack packets since the face is established.
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* **NInBytes** counts the number of bytes of link layer packets received via this face.
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  This counter is initialized to zero when the face is established, and can wrap around after overflowing unsigned 64-bit integer range.
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* **NOutBytes** counts the number of bytes of link layer packets sent via this face.
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  This counter is initialized to zero when the face is established, and can wrap around after overflowing unsigned 64-bit integer range.
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* **Flags** contains these bitfields: *LocalFieldsEnabled*, *LpReliabilityEnabled*, *CongestionMarkingEnabled*.
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  See "static face attributes" for more information.
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### Query operation
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The query operation allows one to retrieve a subset of face dataset that contains faces satisfying a filter.
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To run a query, the consumer should express an Interest with Name: `ndn:/localhost/nfd/faces/query/<filter>`, where `<filter>` is a **FaceQueryFilter** block that specifies zero or more conditions.
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    FaceQueryFilter ::= FACE-QUERY-FILTER-TYPE TLV-LENGTH
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                          FaceId?
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                          UriScheme?
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                          Uri?
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                          LocalUri?
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                          FaceScope?
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                          FacePersistency?
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                          LinkType?
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    UriScheme       ::= URI-SCHEME-TYPE TLV-LENGTH
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                          string in UTF-8
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* **FaceId** permits a face if its FaceId equals the value
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* **UriScheme** permits a face if the scheme part of its local FaceUri or remote FaceUri equals the value
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* **Uri** permits a face if its remote FaceUri equals the value
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* **LocalUri** permits a face if its local FaceUri equals the value
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* **FaceScope** permits a face if its *FaceScope* attribute equals the value
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* **FacePersistency** permits a face if its *FacePersistency* attribute equals the value
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* **LinkType** permits a face if its *LinkType* attribute equals the value
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A face must satisfy ALL conditions to satisfy the filter.
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Faces that satisfy the filter are represented by **FaceStatus** blocks, and published as a [[StatusDataset]] under the Interest Name (a Data packet's Name would be `ndn:/localhost/nfd/faces/query/<filter>/<version>/<segment>`).
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Examples of filters:
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* a specific face: `FaceId=260`
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* a specific TCP tunnel: `Uri=tcp4://192.0.2.1:6363`  
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  (note: FaceUri must precisely match the canonical form: use either "tcp4" or "tcp6" instead of "tcp", use IP address instead of domain name, include port number)
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* all TCP tunnels: `UriScheme=tcp`  
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  (note: "tcp" permits both "tcp4" and "tcp6", "udp" permits both "udp4" and "udp6")
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* all UDP multi-access faces: `UriScheme=udp` && `LinkType=multi-access`
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* all Ethernet faces: `UriScheme=ether`  
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  (note: UriScheme matches against both local and remote FaceUri, "dev" also works)
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* all faces: no condition  
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  (note: this is equivalent to face dataset, and face dataset should be preferred for this purpose)
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## Channel Dataset
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Description of all active channels is published as a [[StatusDataset|Status Dataset]] at `ndn:/localhost/nfd/faces/channels`.
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Each channel is represented by a **ChannelStatus** block:
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    ChannelStatus    := CHANNEL-STATUS-TYPE TLV-LENGTH
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                          LocalUri
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* **LocalUri** is a FaceUri representing the channel's local endpoint.
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## Face Status Change Notification
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Face status change events are published as a [[Notification|Notification Stream]] at `ndn:/localhost/nfd/faces/events`.
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Notifications of all faces are sent into the same notification stream.
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The Content of each notification Data packet is a **FaceEventNotification** block:
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    FaceEventNotification ::= FACE-EVENT-NOTIFICATION-TYPE TLV-LENGTH
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                                FaceEventKind
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                                FaceId
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                                Uri
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                                LocalUri
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                                FaceScope
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                                FacePersistency
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                                LinkType
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                                Flags
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    FaceEventKind         ::= FACE-EVENT-KIND-TYPE TLV-LENGTH
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                                nonNegativeInteger
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**FaceEventKind** indicates the kind of event. Its possible values are:
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* 1 = face is created
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* 2 = face is destroyed
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* 3 = face goes UP (from DOWN state)
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* 4 = face goes DOWN (from UP state)
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## TLV-TYPE assignments
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Type                                        | Assigned value    | Assigned value (hex)
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------------------------------------------- | ----------------- | --------------------
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FaceStatus                                  | 128               | 0x80
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LocalUri                                    | 129               | 0x81
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ChannelStatus                               | 130               | 0x82
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UriScheme                                   | 131               | 0x83
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FaceScope                                   | 132               | 0x84
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FacePersistency                             | 133               | 0x85
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LinkType                                    | 134               | 0x86
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BaseCongestionMarkingInterval               | 135               | 0x87
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DefaultCongestionThreshold                  | 136               | 0x88
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Mtu                                         | 137               | 0x89
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NInInterests                                | 144               | 0x90
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NInData                                     | 145               | 0x91
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NInNacks                                    | 151               | 0x97
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NOutInterests                               | 146               | 0x92
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NOutData                                    | 147               | 0x93
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NOutNacks                                   | 152               | 0x98
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NInBytes                                    | 148               | 0x94
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NOutBytes                                   | 149               | 0x95
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FaceQueryFilter                             | 150               | 0x96
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FaceEventNotification                       | 192               | 0xc0
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FaceEventKind                               | 193               | 0xc1
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(reserved, formerly FaceFlags)              | 194               | 0xc2