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+============================================
+High level architecture and general features
+============================================
+
+Architecture Overview
+=====================
+
+.. figure:: images/figure1.png
+   :name: figure1
+   :width: 90%
+
+   Resource Reservation Architecture
+
+:numref:`figure1` shows the high level architecture for the resource reservation
+use cases. Reserved resources are guaranteed for a given user/client for the
+period expressed by start and end time. User/client represents the requestor
+and the consequent consumer of the reserved resources and correspond to the
+NFVO or VNFM in ETSI NFV terminology.
+
+Note: in this document only reservation requests from NFVO are considered.
+
+General Features
+================
+
+This section provides a list of features that need to be developed in the
+Promise project.
+
+* Resource capacity management
+
+  * Discovery of available resource capacity in resource providers
+  * Monitoring of available resource capacity in resource providers
+  * Update available resource capacity as a result of new or expired
+    reservations, addition/removal of resources. Note: this is a VIM internal
+    function, not an operation in the VIM northbound interface.
+
+* Resource reservation
+
+  * Set start time and end time for allocation
+  * Increase/decrease reserved resource's capacity
+  * Update resource reservations, e.g. add/remove reserved resources
+  * Terminate an allocated resource due to the end time of a reservation
+
+* VIM northbound interfaces
+
+  * Receive/Reply resource reservation requests
+  * Receive/Reply resource capacity management requests
+  * Receive/Reply resource allocation requests for reserved resources when
+    start time arrives
+  * Subscribe/Notify resource reservation event
+
+    * Notify reservation error or process completion prior to reservation
+      start
+    * Notify remaining time until termination of a resource due to the end
+      time of a reservation
+    * Notify termination of a resource due to the end time of a reservation
+
+  * Receive/Reply queries on available resource capacity
+  * Subscribe/Notify changes in available resource capacity
+
+High level northbound interface specification
+=============================================
+
+Resource Capacity Management
+----------------------------
+
+.. figure:: images/figure2.png
+   :name: figure2
+   :width: 90%
+
+   Resource capacity management message flow: notification of capacity change
+
+:numref:`figure2` shows a high level flow for a use case of resource capacity
+management. In this example, the VIM notifies the NFVO of capacity change after
+having received an event regarding a change in capacity (e.g. a fault
+notification) from the NFVI. The NFVO can also retrieve detailed capacity
+information using the Query Capacity Request interface operation.
+
+.. figure:: images/figure3.png
+   :name: figure3
+   :width: 90%
+
+   Resource capacity management message flow: query of capacity density
+
+:numref:`figure3` shows a high level flow for another use case of resource
+capacity management. In this example, the NFVO queries the VIM about the actual
+capacity to instantiate a certain resource according to a certain template, for
+example a VM according to a certain flavor. In this case the VIM responds with
+the number of VMs that could be instantiated according to that flavor with the
+currently available capacity.
+
+Resource Reservation
+--------------------
+
+.. figure:: images/figure4.png
+   :name: figure4
+   :width: 90%
+
+   Resource reservation flow
+
+:numref:`figure4` shows a high level flow for a use case of resource
+reservation. The main steps are:
+
+* The NFVO sends a resource reservation request to the VIM using the Create
+  Resource Reservation Request interface operation.
+* The NFVO gets a reservation identifier reservation associated with this
+  request in the reply message
+* Using the reservation identifier reservation, the NFVO can
+  query/update/terminate a resource reservation using the corresponding
+  interface operations
+* The NFVO is notified that the resource reservation is terminated due to the
+  end time of the reservation
+
+
+Information elements
+====================
+
+Resource Capacity Management
+----------------------------
+
+Notify Capacity Change Event
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The notification change message shall include the following information elements:
+
+============================ ========== =====================================
+Name                         Type       Description
+============================ ========== =====================================
+Notification                 Identifier Identifier issued by the VIM for the
+                                        capacity change event notification
+Zone                         Identifier Identifier of the zone where capacity
+                                        has changed
+Used/Reserved/Total Capacity List       Used, reserved and total capacity
+                                        information regarding the resource
+                                        items subscribed for notification for
+                                        which capacity change event occurred
+============================ ========== =====================================
+
+Query Resource Capacity Request
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The capacity management query request message shall include the following
+information elements:
+
+========== ========== ======================================================
+Name       Type       Description
+========== ========== ======================================================
+Zone       Identifier Identifier of the zone where capacity is requested
+Attributes List       Attributes of resource items to be notified regarding
+                      capacity change events
+Resources  List       Identifiers of existing resource items to be queried
+                      regarding capacity info (such as images, flavors,
+                      virtual containers, networks, physical machines, etc.)
+========== ========== ======================================================
+
+The capacity management query request message may also include the following
+information element:
+
+====== ========== ==========================================================
+Name   Type       Description
+====== ========== ==========================================================
+Flavor Identifier Identifier that is passed in the request to obtain
+                  information of the number of virtual resources that can be
+                  instantiated according to this flavor with the available
+                  capacity
+====== ========== ==========================================================
+
+Query Resource Capacity Reply
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The capacity management query reply message shall include the following
+information elements:
+
+============================ ========== =====================================
+Name                         Type       Description
+============================ ========== =====================================
+Zone                         Identifier Identifier of the zone where capacity
+                                        is requested
+Used/Reserved/Total Capacity List       Used, reserved and total capacity
+                                        information regarding each of the
+                                        resource items requested to check for
+                                        capacity
+============================ ========== =====================================
+
+The detailed specification of the northbound interface for Capacity Management
+in provided in section 5.1.1.
+
+Resource Reservation
+--------------------
+
+Create Resource Reservation Request
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The create resource reservation request message shall include the following
+information elements:
+
+========== ========== =========================================================
+Name       Type       Description
+========== ========== =========================================================
+Start      Timestamp  Start time for consumption of the reserved resources
+End        Timestamp  End time for consumption of the reserved resources
+Expiry     Timestamp  If not all reserved resources are allocated between start
+                      time and expiry, the VIM shall release the corresponding
+                      resources [#expiry]_
+Amount     Number     Amount of the resources per resource item type (i.e.
+                      compute/network/storage) that need to be reserved
+Zone       Identifier The zone  where the resources need(s) to be reserved
+Attributes List       Attributes of the resources to be reserved such as DPDK
+                      support, hypervisor, network link bandwidth, affinity
+                      rules, etc.
+Resources  List       Identifiers of existing resource items to be reserved
+                      (such as images, flavors, virtual containers, networks,
+                      physical machines, etc.)
+========== ========== =========================================================
+
+.. [#expiry] Expiry is a period around start time within which, the allocation
+             process must take place. If allocation process does not start
+             within the expiry period, the reservation becomes invalid and VIM
+             should release the resources
+
+Create Resource Reservation Reply
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The create resource reservation reply message shall include the following
+information elements:
+
+=========== ========== =======================================================
+Name        Type       Description
+=========== ========== =======================================================
+Reservation Identifier Identification of the reservation instance. It can be
+                       used by a consumer to modify the reservation later, and
+                       to request the allocation of the reserved resources.
+Message     Text       Output message that provides additional information
+                       about the create resource reservation request (e.g. may
+                       be a simple ACK if the request is being background
+                       processed by the VIM)
+=========== ========== =======================================================
+
+Notify Reservation Event
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+The notification reservation event message shall include the following
+information elements:
+
+============ ========== =====================================================
+Name         Type       Description
+============ ========== =====================================================
+Reservation  Identifier Identification of the reservation instance triggering
+                        the event
+Notification Identifier Identification of the resource event notification
+                        issued by the VIM
+Message      Text       Message describing the event
+============ ========== =====================================================
+
+The detailed specification of the northbound interface for Resource Reservation
+is provided in section 5.1.2.