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diff --git a/docs/development/requirements/01-intro.rst b/docs/development/requirements/01-intro.rst
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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Introduction
+============
+
+The goal of this project is to build an NFVI fault management and maintenance
+framework supporting high availability of the Network Services on top of the
+virtualized infrastructure. The key feature is immediate notification of
+unavailability of virtualized resources from VIM, to support failure recovery,
+or failure avoidance of VNFs running on them. Requirement survey and development
+of missing features in NFVI and VIM are in scope of this project in order to
+fulfil requirements for fault management and maintenance in NFV.
+
+The purpose of this requirement project is to clarify the necessary features of
+NFVI fault management, and maintenance, identify missing features in the current
+OpenSource implementations, provide a potential implementation architecture and
+plan, provide implementation guidelines in relevant upstream projects to realize
+those missing features, and define the VIM northbound interfaces necessary to
+perform the task of NFVI fault management, and maintenance in alignment with
+ETSI NFV [ENFV]_.
+
+Problem description
+-------------------
+
+A Virtualized Infrastructure Manager (VIM), e.g. OpenStack [OPSK]_, cannot
+detect certain Network Functions Virtualization Infrastructure (NFVI) faults.
+This feature is necessary to detect the faults and notify the Consumer in order
+to ensure the proper functioning of EPC VNFs like MME and S/P-GW.
+
+* EPC VNFs are often in active standby (ACT-STBY) configuration and need to
+ switch from STBY mode to ACT mode as soon as relevant faults are detected in
+ the active (ACT) VNF.
+
+* NFVI encompasses all elements building up the environment in which VNFs are
+ deployed, e.g., Physical Machines, Hypervisors, Storage, and Network elements.
+
+In addition, VIM, e.g. OpenStack, needs to receive maintenance instructions from
+the Consumer, i.e. the operator/administrator of the VNF.
+
+* Change the state of certain Physical Machines (PMs), e.g. empty the PM, so
+ that maintenance work can be performed at these machines.
+
+Note: Although fault management and maintenance are different operations in NFV,
+both are considered as part of this project as -- except for the trigger -- they
+share a very similar work and message flow. Hence, from implementation
+perspective, these two are kept together in the Doctor project because of this
+high degree of similarity.
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/02-use_cases.rst b/docs/development/requirements/02-use_cases.rst
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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Use cases and scenarios
+=======================
+
+Telecom services often have very high requirements on service performance. As a
+consequence they often utilize redundancy and high availability (HA) mechanisms
+for both the service and the platform. The HA support may be built-in or
+provided by the platform. In any case, the HA support typically has a very fast
+detection and reaction time to minimize service impact. The main changes
+proposed in this document are about making a clear distinction between fault
+management and recovery a) within the VIM/NFVI and b) High Availability support
+for VNFs on the other, claiming that HA support within a VNF or as a service
+from the platform is outside the scope of Doctor and is discussed in the High
+Availability for OPNFV project. Doctor should focus on detecting and remediating
+faults in the NFVI. This will ensure that applications come back to a fully
+redundant configuration faster than before.
+
+As an example, Telecom services can come with an Active-Standby (ACT-STBY)
+configuration which is a (1+1) redundancy scheme. ACT and STBY nodes (aka
+Physical Network Function (PNF) in ETSI NFV terminology) are in a hot standby
+configuration. If an ACT node is unable to function properly due to fault or any
+other reason, the STBY node is instantly made ACT, and affected services can be
+provided without any service interruption.
+
+The ACT-STBY configuration needs to be maintained. This means, when a STBY node
+is made ACT, either the previously ACT node, after recovery, shall be made STBY,
+or, a new STBY node needs to be configured. The actual operations to
+instantiate/configure a new STBY are similar to instantiating a new VNF and
+therefore are outside the scope of this project.
+
+The NFVI fault management and maintenance requirements aim at providing fast
+failure detection of physical and virtualized resources and remediation of the
+virtualized resources provided to Consumers according to their predefined
+request to enable applications to recover to a fully redundant mode of
+operation.
+
+1. Fault management/recovery using ACT-STBY configuration (Triggered by critical
+ error)
+2. Preventive actions based on fault prediction (Preventing service stop by
+ handling warnings)
+3. VM Retirement (Managing service during NFVI maintenance, i.e. H/W,
+ Hypervisor, Host OS, maintenance)
+
+Faults
+------
+
+.. _uc-fault1:
+
+Fault management using ACT-STBY configuration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In :numref:`figure1`, a system-wide view of relevant functional blocks is
+presented. OpenStack is considered as the VIM implementation (aka Controller)
+which has interfaces with the NFVI and the Consumers. The VNF implementation is
+represented as different virtual resources marked by different colors. Consumers
+(VNFM or NFVO in ETSI NFV terminology) own/manage the respective virtual
+resources (VMs in this example) shown with the same colors.
+
+The first requirement in this use case is that the Controller needs to detect
+faults in the NFVI ("1. Fault Notification" in :numref:`figure1`) affecting
+the proper functioning of the virtual resources (labelled as VM-x) running on
+top of it. It should be possible to configure which relevant fault items should
+be detected. The VIM (e.g. OpenStack) itself could be extended to detect such
+faults. Alternatively, a third party fault monitoring tool could be used which
+then informs the VIM about such faults; this third party fault monitoring
+element can be considered as a component of VIM from an architectural point of
+view.
+
+Once such fault is detected, the VIM shall find out which virtual resources are
+affected by this fault. In the example in :numref:`figure1`, VM-4 is
+affected by a fault in the Hardware Server-3. Such mapping shall be maintained
+in the VIM, depicted as the "Server-VM info" table inside the VIM.
+
+Once the VIM has identified which virtual resources are affected by the fault,
+it needs to find out who is the Consumer (i.e. the owner/manager) of the
+affected virtual resources (Step 2). In the example shown in :numref:`figure1`,
+the VIM knows that for the red VM-4, the manager is the red Consumer
+through an Ownership info table. The VIM then notifies (Step 3 "Fault
+Notification") the red Consumer about this fault, preferably with sufficient
+abstraction rather than detailed physical fault information.
+
+.. figure:: images/figure1.png
+ :name: figure1
+ :width: 100%
+
+ Fault management/recovery use case
+
+The Consumer then switches to STBY configuration by switching the STBY node to
+ACT state (Step 4). It further initiates a process to instantiate/configure a
+new STBY. However, switching to STBY mode and creating a new STBY machine is a
+VNFM/NFVO level operation and therefore outside the scope of this project.
+Doctor project does not create interfaces for such VNFM level configuration
+operations. Yet, since the total failover time of a consumer service depends on
+both the delay of such processes as well as the reaction time of Doctor
+components, minimizing Doctor's reaction time is a necessary basic ingredient to
+fast failover times in general.
+
+Once the Consumer has switched to STBY configuration, it notifies (Step 5
+"Instruction" in :numref:`figure1`) the VIM. The VIM can then take
+necessary (e.g. pre-determined by the involved network operator) actions on how
+to clean up the fault affected VMs (Step 6 "Execute Instruction").
+
+The key issue in this use case is that a VIM (OpenStack in this context) shall
+not take a standalone fault recovery action (e.g. migration of the affected VMs)
+before the ACT-STBY switching is complete, as that might violate the ACT-STBY
+configuration and render the node out of service.
+
+As an extension of the 1+1 ACT-STBY resilience pattern, a STBY instance can act as
+backup to N ACT nodes (N+1). In this case, the basic information flow remains
+the same, i.e., the consumer is informed of a failure in order to activate the
+STBY node. However, in this case it might be useful for the failure notification
+to cover a number of failed instances due to the same fault (e.g., more than one
+instance might be affected by a switch failure). The reaction of the consumer
+might depend on whether only one active instance has failed (similar to the
+ACT-STBY case), or if more active instances are needed as well.
+
+Preventive actions based on fault prediction
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The fault management scenario explained in :ref:`uc-fault1` can also be
+performed based on fault prediction. In such cases, in VIM, there is an
+intelligent fault prediction module which, based on its NFVI monitoring
+information, can predict an imminent fault in the elements of NFVI.
+A simple example is raising temperature of a Hardware Server which might
+trigger a pre-emptive recovery action. The requirements of such fault
+prediction in the VIM are investigated in the OPNFV project "Data Collection
+for Failure Prediction" [PRED]_.
+
+This use case is very similar to :ref:`uc-fault1`. Instead of a fault
+detection (Step 1 "Fault Notification in" :numref:`figure1`), the trigger
+comes from a fault prediction module in the VIM, or from a third party module
+which notifies the VIM about an imminent fault. From Step 2~5, the work flow is
+the same as in the "Fault management using ACT-STBY configuration" use case,
+except in this case, the Consumer of a VM/VNF switches to STBY configuration
+based on a predicted fault, rather than an occurred fault.
+
+NFVI Maintenance
+----------------
+
+VM Retirement
+^^^^^^^^^^^^^
+
+All network operators perform maintenance of their network infrastructure, both
+regularly and irregularly. Besides the hardware, virtualization is expected to
+increase the number of elements subject to such maintenance as NFVI holds new
+elements like the hypervisor and host OS. Maintenance of a particular resource
+element e.g. hardware, hypervisor etc. may render a particular server hardware
+unusable until the maintenance procedure is complete.
+
+However, the Consumer of VMs needs to know that such resources will be
+unavailable because of NFVI maintenance. The following use case is again to
+ensure that the ACT-STBY configuration is not violated. A stand-alone action
+(e.g. live migration) from VIM/OpenStack to empty a physical machine so that
+consequent maintenance procedure could be performed may not only violate the
+ACT-STBY configuration, but also have impact on real-time processing scenarios
+where dedicated resources to virtual resources (e.g. VMs) are necessary and a
+pause in operation (e.g. vCPU) is not allowed. The Consumer is in a position to
+safely perform the switch between ACT and STBY nodes, or switch to an
+alternative VNF forwarding graph so the hardware servers hosting the ACT nodes
+can be emptied for the upcoming maintenance operation. Once the target hardware
+servers are emptied (i.e. no virtual resources are running on top), the VIM can
+mark them with an appropriate flag (i.e. "maintenance" state) such that these
+servers are not considered for hosting of virtual machines until the maintenance
+flag is cleared (i.e. nodes are back in "normal" status).
+
+A high-level view of the maintenance procedure is presented in :numref:`figure2`.
+VIM/OpenStack, through its northbound interface, receives a maintenance notification
+(Step 1 "Maintenance Request") from the Administrator (e.g. a network operator)
+including information about which hardware is subject to maintenance.
+Maintenance operations include replacement/upgrade of hardware,
+update/upgrade of the hypervisor/host OS, etc.
+
+The consequent steps to enable the Consumer to perform ACT-STBY switching are
+very similar to the fault management scenario. From VIM/OpenStack's internal
+database, it finds out which virtual resources (VM-x) are running on those
+particular Hardware Servers and who are the managers of those virtual resources
+(Step 2). The VIM then informs the respective Consumer (VNFMs or NFVO) in Step 3
+"Maintenance Notification". Based on this, the Consumer takes necessary actions
+(Step 4, e.g. switch to STBY configuration or switch VNF forwarding graphs) and
+then notifies (Step 5 "Instruction") the VIM. Upon receiving such notification,
+the VIM takes necessary actions (Step 6 "Execute Instruction" to empty the
+Hardware Servers so that consequent maintenance operations could be performed.
+Due to the similarity for Steps 2~6, the maintenance procedure and the fault
+management procedure are investigated in the same project.
+
+.. figure:: images/figure2.png
+ :name: figure2
+ :width: 100%
+
+ Maintenance use case
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/03-architecture.rst b/docs/development/requirements/03-architecture.rst
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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+High level architecture and general features
+============================================
+
+Functional overview
+-------------------
+
+The Doctor project circles around two distinct use cases: 1) management of
+failures of virtualized resources and 2) planned maintenance, e.g. migration, of
+virtualized resources. Both of them may affect a VNF/application and the network
+service it provides, but there is a difference in frequency and how they can be
+handled.
+
+Failures are spontaneous events that may or may not have an impact on the
+virtual resources. The Consumer should as soon as possible react to the failure,
+e.g., by switching to the STBY node. The Consumer will then instruct the VIM on
+how to clean up or repair the lost virtual resources, i.e. restore the VM, VLAN
+or virtualized storage. How much the applications are affected varies.
+Applications with built-in HA support might experience a short decrease in
+retainability (e.g. an ongoing session might be lost) while keeping availability
+(establishment or re-establishment of sessions are not affected), whereas the
+impact on applications without built-in HA may be more serious. How much the
+network service is impacted depends on how the service is implemented. With
+sufficient network redundancy the service may be unaffected even when a specific
+resource fails.
+
+On the other hand, planned maintenance impacting virtualized resources are events
+that are known in advance. This group includes e.g. migration due to software
+upgrades of OS and hypervisor on a compute host. Some of these might have been
+requested by the application or its management solution, but there is also a
+need for coordination on the actual operations on the virtual resources. There
+may be an impact on the applications and the service, but since they are not
+spontaneous events there is room for planning and coordination between the
+application management organization and the infrastructure management
+organization, including performing whatever actions that would be required to
+minimize the problems.
+
+Failure prediction is the process of pro-actively identifying situations that
+may lead to a failure in the future unless acted on by means of maintenance
+activities. From applications' point of view, failure prediction may impact them
+in two ways: either the warning time is so short that the application or its
+management solution does not have time to react, in which case it is equal to
+the failure scenario, or there is sufficient time to avoid the consequences by
+means of maintenance activities, in which case it is similar to planned
+maintenance.
+
+Architecture Overview
+---------------------
+
+NFV and the Cloud platform provide virtual resources and related control
+functionality to users and administrators. :numref:`figure3` shows the high
+level architecture of NFV focusing on the NFVI, i.e., the virtualized
+infrastructure. The NFVI provides virtual resources, such as virtual machines
+(VM) and virtual networks. Those virtual resources are used to run applications,
+i.e. VNFs, which could be components of a network service which is managed by
+the consumer of the NFVI. The VIM provides functionalities of controlling and
+viewing virtual resources on hardware (physical) resources to the consumers,
+i.e., users and administrators. OpenStack is a prominent candidate for this VIM.
+The administrator may also directly control the NFVI without using the VIM.
+
+Although OpenStack is the target upstream project where the new functional
+elements (Controller, Notifier, Monitor, and Inspector) are expected to be
+implemented, a particular implementation method is not assumed. Some of these
+elements may sit outside of OpenStack and offer a northbound interface to
+OpenStack.
+
+General Features and Requirements
+---------------------------------
+
+The following features are required for the VIM to achieve high availability of
+applications (e.g., MME, S/P-GW) and the Network Services:
+
+1. Monitoring: Monitor physical and virtual resources.
+2. Detection: Detect unavailability of physical resources.
+3. Correlation and Cognition: Correlate faults and identify affected virtual
+ resources.
+4. Notification: Notify unavailable virtual resources to their Consumer(s).
+5. Fencing: Shut down or isolate a faulty resource.
+6. Recovery action: Execute actions to process fault recovery and maintenance.
+
+The time interval between the instant that an event is detected by the
+monitoring system and the Consumer notification of unavailable resources shall
+be < 1 second (e.g., Step 1 to Step 4 in :numref:`figure4`).
+
+.. figure:: images/figure3.png
+ :name: figure3
+ :width: 100%
+
+ High level architecture
+
+Monitoring
+^^^^^^^^^^
+
+The VIM shall monitor physical and virtual resources for unavailability and
+suspicious behavior.
+
+Detection
+^^^^^^^^^
+
+The VIM shall detect unavailability and failures of physical resources that
+might cause errors/faults in virtual resources running on top of them.
+Unavailability of physical resource is detected by various monitoring and
+managing tools for hardware and software components. This may include also
+predicting upcoming faults. Note, fault prediction is out of scope of this
+project and is investigated in the OPNFV "Data Collection for Failure
+Prediction" project [PRED]_.
+
+The fault items/events to be detected shall be configurable.
+
+The configuration shall enable Failure Selection and Aggregation. Failure
+aggregation means the VIM determines unavailability of physical resource from
+more than two non-critical failures related to the same resource.
+
+There are two types of unavailability - immediate and future:
+
+* Immediate unavailability can be detected by setting traps of raw failures on
+ hardware monitoring tools.
+* Future unavailability can be found by receiving maintenance instructions
+ issued by the administrator of the NFVI or by failure prediction mechanisms.
+
+Correlation and Cognition
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The VIM shall correlate each fault to the impacted virtual resource, i.e., the
+VIM shall identify unavailability of virtualized resources that are or will be
+affected by failures on the physical resources under them. Unavailability of a
+virtualized resource is determined by referring to the mapping of physical and
+virtualized resources.
+
+VIM shall allow configuration of fault correlation between physical and
+virtual resources. VIM shall support correlating faults:
+
+* between a physical resource and another physical resource
+* between a physical resource and a virtual resource
+* between a virtual resource and another virtual resource
+
+Failure aggregation is also required in this feature, e.g., a user may request
+to be only notified if failures on more than two standby VMs in an (N+M)
+deployment model occurred.
+
+Notification
+^^^^^^^^^^^^
+
+The VIM shall notify the alarm, i.e., unavailability of virtual resource(s), to
+the Consumer owning it over the northbound interface, such that the Consumers
+impacted by the failure can take appropriate actions to recover from the
+failure.
+
+The VIM shall also notify the unavailability of physical resources to its
+Administrator.
+
+All notifications shall be transferred immediately in order to minimize the
+stalling time of the network service and to avoid over assignment caused by
+delay of capability updates.
+
+There may be multiple consumers, so the VIM has to find out the owner of a
+faulty resource. Moreover, there may be a large number of virtual and physical
+resources in a real deployment, so polling the state of all resources to the VIM
+would lead to heavy signaling traffic. Thus, a publication/subscription
+messaging model is better suited for these notifications, as notifications are
+only sent to subscribed consumers.
+
+Notifications will be send out along with the configuration by the consumer.
+The configuration includes endpoint(s) in which the consumers can specify
+multiple targets for the notification subscription, so that various and
+multiple receiver functions can consume the notification message.
+Also, the conditions for notifications shall be configurable, such that
+the consumer can set according policies, e.g. whether it wants to receive
+fault notifications or not.
+
+Note: the VIM should only accept notification subscriptions for each resource
+by its owner or administrator.
+Notifications to the Consumer about the unavailability of virtualized
+resources will include a description of the fault, preferably with sufficient
+abstraction rather than detailed physical fault information.
+
+.. _fencing:
+
+Fencing
+^^^^^^^
+Recovery actions, e.g. safe VM evacuation, have to be preceded by fencing the
+failed host. Fencing hereby means to isolate or shut down a faulty resource.
+Without fencing -- when the perceived disconnection is due to some transient
+or partial failure -- the evacuation might lead into two identical instances
+running together and having a dangerous conflict.
+
+There is a cross-project definition in OpenStack of how to implement
+fencing, but there has not been any progress. The general description is
+available here:
+https://wiki.openstack.org/wiki/Fencing_Instances_of_an_Unreachable_Host
+
+OpenStack provides some mechanisms that allow fencing of faulty resources. Some
+are automatically invoked by the platform itself (e.g. Nova disables the
+compute service when libvirtd stops running, preventing new VMs to be scheduled
+to that node), while other mechanisms are consumer trigger-based actions (e.g.
+Neutron port admin-state-up). For other fencing actions not supported by
+OpenStack, the Doctor project may suggest ways to address the gap (e.g. through
+means of resourcing to external tools and orchestration methods), or
+documenting or implementing them upstream.
+
+The Doctor Inspector component will be responsible of marking resources down in
+the OpenStack and back up if necessary.
+
+Recovery Action
+^^^^^^^^^^^^^^^
+
+In the basic :ref:`uc-fault1` use case, no automatic actions will be taken by
+the VIM, but all recovery actions executed by the VIM and the NFVI will be
+instructed and coordinated by the Consumer.
+
+In a more advanced use case, the VIM may be able to recover the failed virtual
+resources according to a pre-defined behavior for that resource. In principle
+this means that the owner of the resource (i.e., its consumer or administrator)
+can define which recovery actions shall be taken by the VIM. Examples are a
+restart of the VM or migration/evacuation of the VM.
+
+
+
+High level northbound interface specification
+---------------------------------------------
+
+Fault Management
+^^^^^^^^^^^^^^^^
+
+This interface allows the Consumer to subscribe to fault notification from the
+VIM. Using a filter, the Consumer can narrow down which faults should be
+notified. A fault notification may trigger the Consumer to switch from ACT to
+STBY configuration and initiate fault recovery actions. A fault query
+request/response message exchange allows the Consumer to find out about active
+alarms at the VIM. A filter can be used to narrow down the alarms returned in
+the response message.
+
+.. figure:: images/figure4.png
+ :name: figure4
+ :width: 100%
+
+ High-level message flow for fault management
+
+The high level message flow for the fault management use case is shown in
+:numref:`figure4`.
+It consists of the following steps:
+
+1. The VIM monitors the physical and virtual resources and the fault management
+ workflow is triggered by a monitored fault event.
+2. Event correlation, fault detection and aggregation in VIM. Note: this may
+ also happen after Step 3.
+3. Database lookup to find the virtual resources affected by the detected fault.
+4. Fault notification to Consumer.
+5. The Consumer switches to standby configuration (STBY).
+6. Instructions to VIM requesting certain actions to be performed on the
+ affected resources, for example migrate/update/terminate specific
+ resource(s). After reception of such instructions, the VIM is executing the
+ requested action, e.g., it will migrate or terminate a virtual resource.
+
+NFVI Maintenance
+^^^^^^^^^^^^^^^^
+
+The NFVI maintenance interface allows the Administrator to notify the VIM about
+a planned maintenance operation on the NFVI. A maintenance operation may for
+example be an update of the server firmware or the hypervisor. The
+MaintenanceRequest message contains instructions to change the state of the
+physical resource from 'enabled' to 'going-to-maintenance' and a timeout [#timeout]_.
+After receiving the MaintenanceRequest,the VIM decides on the actions to be taken
+based on maintenance policies predefined by the affected Consumer(s).
+
+.. [#timeout] Timeout is set by the Administrator and corresponds to the maximum time
+ to empty the physical resources.
+
+.. figure:: images/figure5a.png
+ :name: figure5a
+ :width: 100%
+
+ High-level message flow for maintenance policy enforcement
+
+The high level message flow for the NFVI maintenance policy enforcement is shown
+in :numref:`figure5a`. It consists of the following steps:
+
+1. Maintenance trigger received from Administrator.
+2. VIM switches the affected physical resources to "going-to-maintenance" state e.g. so that no new
+ VM will be scheduled on the physical servers.
+3. Database lookup to find the Consumer(s) and virtual resources affected by the maintenance
+ operation.
+4. Maintenance policies are enforced in the VIM, e.g. affected VM(s) are shut down
+ on the physical server(s), or affected Consumer(s) are notified about the planned
+ maintenance operation (steps 4a/4b).
+
+
+Once the affected Consumer(s) have been notified, they take specific actions (e.g. switch to standby
+(STBY) configuration, request to terminate the virtual resource(s)) to allow the maintenance
+action to be executed. After the physical resources have been emptied, the VIM puts the physical
+resources in "in-maintenance" state and sends a MaintenanceResponse back to the Administrator.
+
+.. figure:: images/figure5b.png
+ :name: figure5b
+ :width: 100%
+
+ Successful NFVI maintenance
+
+The high level message flow for a successful NFVI maintenance is show in :numref:`figure5b`.
+It consists of the following steps:
+
+5. The Consumer C3 switches to standby configuration (STBY).
+6. Instructions from Consumers C2/C3 are shared to VIM requesting certain actions to be performed
+ (steps 6a, 6b). After receiving such instructions, the VIM executes the requested
+ action in order to empty the physical resources (step 6c) and informs the
+ Consumer about the result of the actions (steps 6d, 6e).
+7. The VIM switches the physical resources to "in-maintenance" state
+8. Maintenance response is sent from VIM to inform the Administrator that the physical
+ servers have been emptied.
+9. The Administrator is coordinating and executing the maintenance
+ operation/work on the NFVI. Note: this step is out of scope of Doctor project.
+
+The requested actions to empty the physical resources may not be successful (e.g. migration fails
+or takes too long) and in such a case, the VIM puts the physical resources back to 'enabled' and
+informs the Administrator about the problem.
+
+.. figure:: images/figure5c.png
+ :name: figure5c
+ :width: 100%
+
+ Example of failed NFVI maintenance
+
+An example of a high level message flow to cover the failed NFVI maintenance case is
+shown in :numref:`figure5c`.
+It consists of the following steps:
+
+5. The Consumer C3 switches to standby configuration (STBY).
+6. Instructions from Consumers C2/C3 are shared to VIM requesting certain actions to be performed
+ (steps 6a, 6b). The VIM executes the requested actions and sends back a NACK to consumer C2
+ (step 6d) as the migration of the virtual resource(s) is not completed by the given timeout.
+7. The VIM switches the physical resources to "enabled" state.
+8. MaintenanceNotification is sent from VIM to inform the Administrator that the maintenance action
+ cannot start.
+
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
+
diff --git a/docs/development/requirements/04-gaps.rst b/docs/development/requirements/04-gaps.rst
new file mode 100644
index 00000000..b8ff7f2e
--- /dev/null
+++ b/docs/development/requirements/04-gaps.rst
@@ -0,0 +1,389 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Gap analysis in upstream projects
+=================================
+
+This section presents the findings of gaps on existing VIM platforms. The focus
+was to identify gaps based on the features and requirements specified in Section
+3.3. The analysis work determined gaps that are presented here.
+
+VIM Northbound Interface
+------------------------
+
+Immediate Notification
+^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'deficiency in performance'
+* Description
+
+ + To-be
+
+ - VIM has to notify unavailability of virtual resource (fault) to VIM user
+ immediately.
+ - Notification should be passed in '1 second' after fault detected/notified
+ by VIM.
+ - Also, the following conditions/requirement have to be met:
+
+ - Only the owning user can receive notification of fault related to owned
+ virtual resource(s).
+
+ + As-is
+
+ - OpenStack Metering 'Ceilometer' can notify unavailability of virtual
+ resource (fault) to the owner of virtual resource based on alarm
+ configuration by the user.
+
+ - Ceilometer Alarm API:
+ http://docs.openstack.org/developer/ceilometer/webapi/v2.html#alarms
+
+ - Alarm notifications are triggered by alarm evaluator instead of
+ notification agents that might receive faults
+
+ - Ceilometer Architecture:
+ http://docs.openstack.org/developer/ceilometer/architecture.html#id1
+
+ - Evaluation interval should be equal to or larger than configured pipeline
+ interval for collection of underlying metrics.
+
+ - https://github.com/openstack/ceilometer/blob/stable/juno/ceilometer/alarm/service.py#L38-42
+
+ - The interval for collection has to be set large enough which depends on
+ the size of the deployment and the number of metrics to be collected.
+ - The interval may not be less than one second in even small deployments.
+ The default value is 60 seconds.
+ - Alternative: OpenStack has a message bus to publish system events.
+ The operator can allow the user to connect this, but there are no
+ functions to filter out other events that should not be passed to the user
+ or which were not requested by the user.
+
+ + Gap
+
+ - Fault notifications cannot be received immediately by Ceilometer.
+
+* Solved by
+
+ + Event Alarm Evaluator:
+ https://specs.openstack.org/openstack/ceilometer-specs/specs/liberty/event-alarm-evaluator.html
+ + New OpenStack alarms and notifications project AODH:
+ http://docs.openstack.org/developer/aodh/
+
+Maintenance Notification
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'missing'
+* Description
+
+ + To-be
+
+ - VIM has to notify unavailability of virtual resource triggered by NFVI
+ maintenance to VIM user.
+ - Also, the following conditions/requirements have to be met:
+
+ - VIM should accept maintenance message from administrator and mark target
+ physical resource "in maintenance".
+ - Only the owner of virtual resource hosted by target physical resource
+ can receive the notification that can trigger some process for
+ applications which are running on the virtual resource (e.g. cut off
+ VM).
+
+ + As-is
+
+ - OpenStack: None
+ - AWS (just for study)
+
+ - AWS provides API and CLI to view status of resource (VM) and to create
+ instance status and system status alarms to notify you when an instance
+ has a failed status check.
+ http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-instances-status-check_sched.html
+ - AWS provides API and CLI to view scheduled events, such as a reboot or
+ retirement, for your instances. Also, those events will be notified
+ via e-mail.
+ http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html
+
+ + Gap
+
+ - VIM user cannot receive maintenance notifications.
+
+* Solved by
+
+ + https://blueprints.launchpad.net/nova/+spec/service-status-notification
+
+VIM Southbound interface
+------------------------
+
+Normalization of data collection models
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* Type: 'missing'
+* Description
+
+ + To-be
+
+ - A normalized data format needs to be created to cope with the many data
+ models from different monitoring solutions.
+
+ + As-is
+
+ - Data can be collected from many places (e.g. Zabbix, Nagios, Cacti,
+ Zenoss). Although each solution establishes its own data models, no common
+ data abstraction models exist in OpenStack.
+
+ + Gap
+
+ - Normalized data format does not exist.
+
+* Solved by
+
+ + Specification in Section :ref:`southbound`.
+
+OpenStack
+---------
+
+Ceilometer
+^^^^^^^^^^
+
+OpenStack offers a telemetry service, Ceilometer, for collecting measurements of
+the utilization of physical and virtual resources [CEIL]_. Ceilometer can
+collect a number of metrics across multiple OpenStack components and watch for
+variations and trigger alarms based upon the collected data.
+
+Scalability of fault aggregation
+________________________________
+
+* Type: 'scalability issue'
+* Description
+
+ + To-be
+
+ - Be able to scale to a large deployment, where thousands of monitoring
+ events per second need to be analyzed.
+
+ + As-is
+
+ - Performance issue when scaling to medium-sized deployments.
+
+ + Gap
+
+ - Ceilometer seems to be unsuitable for monitoring medium and large scale
+ NFVI deployments.
+
+* Solved by
+
+ + Usage of Zabbix for fault aggregation [ZABB]_. Zabbix can support a much
+ higher number of fault events (up to 15 thousand events per second, but
+ obviously also has some upper bound:
+ http://blog.zabbix.com/scalable-zabbix-lessons-on-hitting-9400-nvps/2615/
+
+ + Decentralized/hierarchical deployment with multiple instances, where one
+ instance is only responsible for a small NFVI.
+
+Monitoring of hardware and software
+___________________________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+ + To-be
+
+ - OpenStack (as VIM) should monitor various hardware and software in NFVI to
+ handle faults on them by Ceilometer.
+ - OpenStack may have monitoring functionality in itself and can be
+ integrated with third party monitoring tools.
+ - OpenStack need to be able to detect the faults listed in the Annex.
+
+ + As-is
+
+ - For each deployment of OpenStack, an operator has responsibility to
+ configure monitoring tools with relevant scripts or plugins in order to
+ monitor hardware and software.
+ - OpenStack Ceilometer does not monitor hardware and software to capture
+ faults.
+
+ + Gap
+
+ - Ceilometer is not able to detect and handle all faults listed in the Annex.
+
+* Solved by
+
+ + Use of dedicated monitoring tools like Zabbix or Monasca.
+ See :ref:`nfvi_faults`.
+
+Nova
+^^^^
+
+OpenStack Nova [NOVA]_ is a mature and widely known and used component in
+OpenStack cloud deployments. It is the main part of an
+"infrastructure-as-a-service" system providing a cloud computing fabric
+controller, supporting a wide diversity of virtualization and container
+technologies.
+
+Nova has proven throughout these past years to be highly available and
+fault-tolerant. Featuring its own API, it also provides a compatibility API with
+Amazon EC2 APIs.
+
+Correct states when compute host is down
+________________________________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+ + To-be
+
+ - The API shall support to change VM power state in case host has failed.
+ - The API shall support to change nova-compute state.
+ - There could be single API to change different VM states for all VMs
+ belonging to a specific host.
+ - Support external systems that are monitoring the infrastructure and resources
+ that are able to call the API fast and reliable.
+ - Resource states are reliable such that correlation actions can be fast and automated.
+ - User shall be able to read states from OpenStack and trust they are correct.
+
+ + As-is
+
+ - When a VM goes down due to a host HW, host OS or hypervisor failure,
+ nothing happens in OpenStack. The VMs of a crashed host/hypervisor are
+ reported to be live and OK through the OpenStack API.
+ - nova-compute state might change too slowly or the state is not reliable
+ if expecting also VMs to be down. This leads to ability to schedule VMs
+ to a failed host and slowness blocks evacuation.
+
+ + Gap
+
+ - OpenStack does not change its states fast and reliably enough.
+ - The API does not support to have an external system to change states and to
+ trust the states are reliable (external system has fenced failed host).
+ - User cannot read all the states from OpenStack nor trust they are right.
+
+* Solved by
+
+ + https://blueprints.launchpad.net/nova/+spec/mark-host-down
+ + https://blueprints.launchpad.net/python-novaclient/+spec/support-force-down-service
+
+Evacuate VMs in Maintenance mode
+________________________________
+
+* Type: 'missing'
+* Description
+
+ + To-be
+
+ - When maintenance mode for a compute host is set, trigger VM evacuation to
+ available compute nodes before bringing the host down for maintenance.
+
+ + As-is
+
+ - If setting a compute node to a maintenance mode, OpenStack only schedules
+ evacuation of all VMs to available compute nodes if in-maintenance compute
+ node runs the XenAPI and VMware ESX hypervisors. Other hypervisors (e.g.
+ KVM) are not supported and, hence, guest VMs will likely stop running due
+ to maintenance actions administrator may perform (e.g. hardware upgrades,
+ OS updates).
+
+ + Gap
+
+ - Nova libvirt hypervisor driver does not implement automatic guest VMs
+ evacuation when compute nodes are set to maintenance mode (``$ nova
+ host-update --maintenance enable <hostname>``).
+
+Monasca
+^^^^^^^
+
+Monasca is an open-source monitoring-as-a-service (MONaaS) solution that
+integrates with OpenStack. Even though it is still in its early days, it is the
+interest of the community that the platform be multi-tenant, highly scalable,
+performant and fault-tolerant. It provides a streaming alarm engine, a
+notification engine, and a northbound REST API users can use to interact with
+Monasca. Hundreds of thousands of metrics per second can be processed
+[MONA]_.
+
+Anomaly detection
+_________________
+
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+ + To-be
+
+ - Detect the failure and perform a root cause analysis to filter out other
+ alarms that may be triggered due to their cascading relation.
+
+ + As-is
+
+ - A mechanism to detect root causes of failures is not available.
+
+ + Gap
+
+ - Certain failures can trigger many alarms due to their dependency on the
+ underlying root cause of failure. Knowing the root cause can help filter
+ out unnecessary and overwhelming alarms.
+
+* Status
+
+ + Monasca as of now lacks this feature, although the community is aware and
+ working toward supporting it.
+
+Sensor monitoring
+_________________
+
+* Type: 'missing (lack of functionality)'
+* Description
+
+ + To-be
+
+ - It should support monitoring sensor data retrieval, for instance, from
+ IPMI.
+
+ + As-is
+
+ - Monasca does not monitor sensor data
+
+ + Gap
+
+ - Sensor monitoring is very important. It provides operators status
+ on the state of the physical infrastructure (e.g. temperature, fans).
+
+* Addressed by
+
+ + Monasca can be configured to use third-party monitoring solutions (e.g.
+ Nagios, Cacti) for retrieving additional data.
+
+Hardware monitoring tools
+-------------------------
+
+Zabbix
+^^^^^^
+
+Zabbix is an open-source solution for monitoring availability and performance of
+infrastructure components (i.e. servers and network devices), as well as
+applications [ZABB]_. It can be customized for use with OpenStack. It is a
+mature tool and has been proven to be able to scale to large systems with
+100,000s of devices.
+
+Delay in execution of actions
+_____________________________
+
+
+* Type: 'deficiency in performance'
+* Description
+
+ + To-be
+
+ - After detecting a fault, the monitoring tool should immediately execute
+ the appropriate action, e.g. inform the manager through the NB I/F
+
+ + As-is
+
+ - A delay of around 10 seconds was measured in two independent testbed
+ deployments
+
+ + Gap
+
+ - Cause of the delay is a periodic evaluation and notification. Periodicity is configured
+ as 30s default value and can be reduced to 5s but not below.
+ https://github.com/zabbix/zabbix/blob/trunk/conf/zabbix_server.conf#L329
+
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/05-implementation.rst b/docs/development/requirements/05-implementation.rst
new file mode 100644
index 00000000..84979772
--- /dev/null
+++ b/docs/development/requirements/05-implementation.rst
@@ -0,0 +1,1050 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Detailed architecture and interface specification
+=================================================
+
+This section describes a detailed implementation plan, which is based on the
+high level architecture introduced in Section 3. Section 5.1 describes the
+functional blocks of the Doctor architecture, which is followed by a high level
+message flow in Section 5.2. Section 5.3 provides a mapping of selected existing
+open source components to the building blocks of the Doctor architecture.
+Thereby, the selection of components is based on their maturity and the gap
+analysis executed in Section 4. Sections 5.4 and 5.5 detail the specification of
+the related northbound interface and the related information elements. Finally,
+Section 5.6 provides a first set of blueprints to address selected gaps required
+for the realization functionalities of the Doctor project.
+
+.. _impl_fb:
+
+Functional Blocks
+-----------------
+
+This section introduces the functional blocks to form the VIM. OpenStack was
+selected as the candidate for implementation. Inside the VIM, 4 different
+building blocks are defined (see :numref:`figure6`).
+
+.. figure:: images/figure6.png
+ :name: figure6
+ :width: 100%
+
+ Functional blocks
+
+Monitor
+^^^^^^^
+
+The Monitor module has the responsibility for monitoring the virtualized
+infrastructure. There are already many existing tools and services (e.g. Zabbix)
+to monitor different aspects of hardware and software resources which can be
+used for this purpose.
+
+Inspector
+^^^^^^^^^
+
+The Inspector module has the ability a) to receive various failure notifications
+regarding physical resource(s) from Monitor module(s), b) to find the affected
+virtual resource(s) by querying the resource map in the Controller, and c) to
+update the state of the virtual resource (and physical resource).
+
+The Inspector has drivers for different types of events and resources to
+integrate any type of Monitor and Controller modules. It also uses a failure
+policy database to decide on the failure selection and aggregation from raw
+events. This failure policy database is configured by the Administrator.
+
+The reason for separation of the Inspector and Controller modules is to make the
+Controller focus on simple operations by avoiding a tight integration of various
+health check mechanisms into the Controller.
+
+Controller
+^^^^^^^^^^
+
+The Controller is responsible for maintaining the resource map (i.e. the mapping
+from physical resources to virtual resources), accepting update requests for the
+resource state(s) (exposing as provider API), and sending all failure events
+regarding virtual resources to the Notifier. Optionally, the Controller has the
+ability to force the state of a given physical resource to down in the resource
+mapping when it receives failure notifications from the Inspector for that
+given physical resource.
+The Controller also re-calculates the capacity of the NVFI when receiving a
+failure notification for a physical resource.
+
+In a real-world deployment, the VIM may have several controllers, one for each
+resource type, such as Nova, Neutron and Cinder in OpenStack. Each controller
+maintains a database of virtual and physical resources which shall be the master
+source for resource information inside the VIM.
+
+Notifier
+^^^^^^^^
+
+The focus of the Notifier is on selecting and aggregating failure events
+received from the controller based on policies mandated by the Consumer.
+Therefore, it allows the Consumer to subscribe for alarms regarding virtual
+resources using a method such as API endpoint. After receiving a fault
+event from a Controller, it will notify the fault to the Consumer by referring
+to the alarm configuration which was defined by the Consumer earlier on.
+
+To reduce complexity of the Controller, it is a good approach for the
+Controllers to emit all notifications without any filtering mechanism and have
+another service (i.e. Notifier) handle those notifications properly. This is the
+general philosophy of notifications in OpenStack. Note that a fault message
+consumed by the Notifier is different from the fault message received by the
+Inspector; the former message is related to virtual resources which are visible
+to users with relevant ownership, whereas the latter is related to raw devices
+or small entities which should be handled with an administrator privilege.
+
+The northbound interface between the Notifier and the Consumer/Administrator is
+specified in :ref:`impl_nbi`.
+
+Sequence
+--------
+
+Fault Management
+^^^^^^^^^^^^^^^^
+
+The detailed work flow for fault management is as follows (see also :numref:`figure7`):
+
+1. Request to subscribe to monitor specific virtual resources. A query filter
+ can be used to narrow down the alarms the Consumer wants to be informed
+ about.
+2. Each subscription request is acknowledged with a subscribe response message.
+ The response message contains information about the subscribed virtual
+ resources, in particular if a subscribed virtual resource is in "alarm"
+ state.
+3. The NFVI sends monitoring events for resources the VIM has been subscribed
+ to. Note: this subscription message exchange between the VIM and NFVI is not
+ shown in this message flow.
+4. Event correlation, fault detection and aggregation in VIM.
+5. Database lookup to find the virtual resources affected by the detected fault.
+6. Fault notification to Consumer.
+7. The Consumer switches to standby configuration (STBY)
+8. Instructions to VIM requesting certain actions to be performed on the
+ affected resources, for example migrate/update/terminate specific
+ resource(s). After reception of such instructions, the VIM is executing the
+ requested action, e.g. it will migrate or terminate a virtual resource.
+a. Query request from Consumer to VIM to get information about the current
+ status of a resource.
+b. Response to the query request with information about the current status of
+ the queried resource. In case the resource is in "fault" state, information
+ about the related fault(s) is returned.
+
+In order to allow for quick reaction to failures, the time interval between
+fault detection in step 3 and the corresponding recovery actions in step 7 and 8
+shall be less than 1 second.
+
+.. figure:: images/figure7.png
+ :name: figure7
+ :width: 100%
+
+ Fault management work flow
+
+.. figure:: images/figure8.png
+ :name: figure8
+ :width: 100%
+
+ Fault management scenario
+
+:numref:`figure8` shows a more detailed message flow (Steps 4 to 6) between
+the 4 building blocks introduced in :ref:`impl_fb`.
+
+4. The Monitor observed a fault in the NFVI and reports the raw fault to the
+ Inspector.
+ The Inspector filters and aggregates the faults using pre-configured
+ failure policies.
+
+5.
+ a) The Inspector queries the Resource Map to find the virtual resources
+ affected by the raw fault in the NFVI.
+ b) The Inspector updates the state of the affected virtual resources in the
+ Resource Map.
+ c) The Controller observes a change of the virtual resource state and informs
+ the Notifier about the state change and the related alarm(s).
+ Alternatively, the Inspector may directly inform the Notifier about it.
+
+6. The Notifier is performing another filtering and aggregation of the changes
+ and alarms based on the pre-configured alarm configuration. Finally, a fault
+ notification is sent to northbound to the Consumer.
+
+NFVI Maintenance
+^^^^^^^^^^^^^^^^
+.. figure:: images/figure9.png
+ :name: figure9
+ :width: 100%
+
+ NFVI maintenance work flow
+
+The detailed work flow for NFVI maintenance is shown in :numref:`figure9`
+and has the following steps. Note that steps 1, 2, and 5 to 8a in the NFVI
+maintenance work flow are very similar to the steps in the fault management work
+flow and share a similar implementation plan in Release 1.
+
+1. Subscribe to fault/maintenance notifications.
+2. Response to subscribe request.
+3. Maintenance trigger received from administrator.
+4. VIM switches NFVI resources to "maintenance" state. This, e.g., means they
+ should not be used for further allocation/migration requests
+5. Database lookup to find the virtual resources affected by the detected
+ maintenance operation.
+6. Maintenance notification to Consumer.
+7. The Consumer switches to standby configuration (STBY)
+8. Instructions from Consumer to VIM requesting certain recovery actions to be
+ performed (step 8a). After reception of such instructions, the VIM is
+ executing the requested action in order to empty the physical resources (step
+ 8b).
+9. Maintenance response from VIM to inform the Administrator that the physical
+ machines have been emptied (or the operation resulted in an error state).
+10. Administrator is coordinating and executing the maintenance operation/work
+ on the NFVI.
+a) Query request from Administrator to VIM to get information about the
+ current state of a resource.
+b) Response to the query request with information about the current state of
+ the queried resource(s). In case the resource is in "maintenance" state,
+ information about the related maintenance operation is returned.
+
+.. figure:: images/figure10.png
+ :name: figure10
+ :width: 100%
+
+ NFVI Maintenance implementation plan
+
+:numref:`figure10` shows a more detailed message flow (Steps 3 to 6 and 9)
+between the 4 building blocks introduced in Section 5.1..
+
+3. The Administrator is sending a StateChange request to the Controller residing
+ in the VIM.
+4. The Controller queries the Resource Map to find the virtual resources
+ affected by the planned maintenance operation.
+5.
+
+ a) The Controller updates the state of the affected virtual resources in the
+ Resource Map database.
+
+ b) The Controller informs the Notifier about the virtual resources that will
+ be affected by the maintenance operation.
+
+6. A maintenance notification is sent to northbound to the Consumer.
+
+...
+
+9. The Controller informs the Administrator after the physical resources have
+ been freed.
+
+
+
+Implementation plan for OPNFV Release 1
+---------------------------------------
+
+Fault management
+^^^^^^^^^^^^^^^^
+
+:numref:`figure11` shows the implementation plan based on OpenStack and
+related components as planned for Release 1. Hereby, the Monitor can be realized
+by Zabbix. The Controller is realized by OpenStack Nova [NOVA]_, Neutron
+[NEUT]_, and Cinder [CIND]_ for compute, network, and storage,
+respectively. The Inspector can be realized by Monasca [MONA]_ or a simple
+script querying Nova in order to map between physical and virtual resources. The
+Notifier will be realized by Ceilometer [CEIL]_ receiving failure events
+on its notification bus.
+
+:numref:`figure12` shows the inner-workings of Ceilometer. After receiving
+an "event" on its notification bus, first a notification agent will grab the
+event and send a "notification" to the Collector. The collector writes the
+notifications received to the Ceilometer databases.
+
+In the existing Ceilometer implementation, an alarm evaluator is periodically
+polling those databases through the APIs provided. If it finds new alarms, it
+will evaluate them based on the pre-defined alarm configuration, and depending
+on the configuration, it will hand a message to the Alarm Notifier, which in
+turn will send the alarm message northbound to the Consumer. :numref:`figure12`
+also shows an optimized work flow for Ceilometer with the goal to
+reduce the delay for fault notifications to the Consumer. The approach is to
+implement a new notification agent (called "publisher" in Ceilometer
+terminology) which is directly sending the alarm through the "Notification Bus"
+to a new "Notification-driven Alarm Evaluator (NAE)" (see Sections 5.6.2 and
+5.6.3), thereby bypassing the Collector and avoiding the additional delay of the
+existing polling-based alarm evaluator. The NAE is similar to the OpenStack
+"Alarm Evaluator", but is triggered by incoming notifications instead of
+periodically polling the OpenStack "Alarms" database for new alarms. The
+Ceilometer "Alarms" database can hold three states: "normal", "insufficient
+data", and "fired". It is representing a persistent alarm database. In order to
+realize the Doctor requirements, we need to define new "meters" in the database
+(see Section 5.6.1).
+
+.. figure:: images/figure11.png
+ :name: figure11
+ :width: 100%
+
+ Implementation plan in OpenStack (OPNFV Release 1 ”Arno”)
+
+
+.. figure:: images/figure12.png
+ :name: figure12
+ :width: 100%
+
+ Implementation plan in Ceilometer architecture
+
+
+NFVI Maintenance
+^^^^^^^^^^^^^^^^
+
+For NFVI Maintenance, a quite similar implementation plan exists. Instead of a
+raw fault being observed by the Monitor, the Administrator is sending a
+Maintenance Request through the northbound interface towards the Controller
+residing in the VIM. Similar to the Fault Management use case, the Controller
+(in our case OpenStack Nova) will send a maintenance event to the Notifier (i.e.
+Ceilometer in our implementation). Within Ceilometer, the same workflow as
+described in the previous section applies. In addition, the Controller(s) will
+take appropriate actions to evacuate the physical machines in order to prepare
+them for the planned maintenance operation. After the physical machines are
+emptied, the Controller will inform the Administrator that it can initiate the
+maintenance. Alternatively the VMs can just be shut down and boot up on the
+same host after maintenance is over. There needs to be policy for administrator
+to know the plan for VMs in maintenance.
+
+Information elements
+--------------------
+
+This section introduces all attributes and information elements used in the
+messages exchange on the northbound interfaces between the VIM and the VNFO and
+VNFM.
+
+Note: The information elements will be aligned with current work in ETSI NFV IFA
+working group.
+
+
+Simple information elements:
+
+* SubscriptionID (Identifier): identifies a subscription to receive fault or maintenance
+ notifications.
+* NotificationID (Identifier): identifies a fault or maintenance notification.
+* VirtualResourceID (Identifier): identifies a virtual resource affected by a
+ fault or a maintenance action of the underlying physical resource.
+* PhysicalResourceID (Identifier): identifies a physical resource affected by a
+ fault or maintenance action.
+* VirtualResourceState (String): state of a virtual resource, e.g. "normal",
+ "maintenance", "down", "error".
+* PhysicalResourceState (String): state of a physical resource, e.g. "normal",
+ "maintenance", "down", "error".
+* VirtualResourceType (String): type of the virtual resource, e.g. "virtual
+ machine", "virtual memory", "virtual storage", "virtual CPU", or "virtual
+ NIC".
+* FaultID (Identifier): identifies the related fault in the underlying physical
+ resource. This can be used to correlate different fault notifications caused
+ by the same fault in the physical resource.
+* FaultType (String): Type of the fault. The allowed values for this parameter
+ depend on the type of the related physical resource. For example, a resource
+ of type "compute hardware" may have faults of type "CPU failure", "memory
+ failure", "network card failure", etc.
+* Severity (Integer): value expressing the severity of the fault. The higher the
+ value, the more severe the fault.
+* MinSeverity (Integer): value used in filter information elements. Only faults
+ with a severity higher than the MinSeverity value will be notified to the
+ Consumer.
+* EventTime (Datetime): Time when the fault was observed.
+* EventStartTime and EventEndTime (Datetime): Datetime range that can be used in
+ a FaultQueryFilter to narrow down the faults to be queried.
+* ProbableCause (String): information about the probable cause of the fault.
+* CorrelatedFaultID (Integer): list of other faults correlated to this fault.
+* isRootCause (Boolean): Parameter indicating if this fault is the root for
+ other correlated faults. If TRUE, then the faults listed in the parameter
+ CorrelatedFaultID are caused by this fault.
+* FaultDetails (Key-value pair): provides additional information about the
+ fault, e.g. information about the threshold, monitored attributes, indication
+ of the trend of the monitored parameter.
+* FirmwareVersion (String): current version of the firmware of a physical
+ resource.
+* HypervisorVersion (String): current version of a hypervisor.
+* ZoneID (Identifier): Identifier of the resource zone. A resource zone is the
+ logical separation of physical and software resources in an NFVI deployment
+ for physical isolation, redundancy, or administrative designation.
+* Metadata (Key-value pair): provides additional information of a physical
+ resource in maintenance/error state.
+
+Complex information elements (see also UML diagrams in :numref:`figure13`
+and :numref:`figure14`):
+
+* VirtualResourceInfoClass:
+
+ + VirtualResourceID [1] (Identifier)
+ + VirtualResourceState [1] (String)
+ + Faults [0..*] (FaultClass): For each resource, all faults
+ including detailed information about the faults are provided.
+
+* FaultClass: The parameters of the FaultClass are partially based on ETSI TS
+ 132 111-2 (V12.1.0) [*]_, which is specifying fault management in 3GPP, in
+ particular describing the information elements used for alarm notifications.
+
+ - FaultID [1] (Identifier)
+ - FaultType [1] (String)
+ - Severity [1] (Integer)
+ - EventTime [1] (Datetime)
+ - ProbableCause [1] (String)
+ - CorrelatedFaultID [0..*] (Identifier)
+ - FaultDetails [0..*] (Key-value pair)
+
+.. [*] http://www.etsi.org/deliver/etsi_ts/132100_132199/13211102/12.01.00_60/ts_13211102v120100p.pdf
+
+* SubscribeFilterClass
+
+ - VirtualResourceType [0..*] (String)
+ - VirtualResourceID [0..*] (Identifier)
+ - FaultType [0..*] (String)
+ - MinSeverity [0..1] (Integer)
+
+* FaultQueryFilterClass: narrows down the FaultQueryRequest, for example it
+ limits the query to certain physical resources, a certain zone, a given fault
+ type/severity/cause, or a specific FaultID.
+
+ - VirtualResourceType [0..*] (String)
+ - VirtualResourceID [0..*] (Identifier)
+ - FaultType [0..*] (String)
+ - MinSeverity [0..1] (Integer)
+ - EventStartTime [0..1] (Datetime)
+ - EventEndTime [0..1] (Datetime)
+
+* PhysicalResourceStateClass:
+
+ - PhysicalResourceID [1] (Identifier)
+ - PhysicalResourceState [1] (String): mandates the new state of the physical
+ resource.
+ - Metadata [0..*] (Key-value pair)
+
+* PhysicalResourceInfoClass:
+
+ - PhysicalResourceID [1] (Identifier)
+ - PhysicalResourceState [1] (String)
+ - FirmwareVersion [0..1] (String)
+ - HypervisorVersion [0..1] (String)
+ - ZoneID [0..1] (Identifier)
+ - Metadata [0..*] (Key-value pair)
+
+* StateQueryFilterClass: narrows down a StateQueryRequest, for example it limits
+ the query to certain physical resources, a certain zone, or a given resource
+ state (e.g., only resources in "maintenance" state).
+
+ - PhysicalResourceID [1] (Identifier)
+ - PhysicalResourceState [1] (String)
+ - ZoneID [0..1] (Identifier)
+
+.. _impl_nbi:
+
+Detailed northbound interface specification
+-------------------------------------------
+
+This section is specifying the northbound interfaces for fault management and
+NFVI maintenance between the VIM on the one end and the Consumer and the
+Administrator on the other ends. For each interface all messages and related
+information elements are provided.
+
+Note: The interface definition will be aligned with current work in ETSI NFV IFA
+working group .
+
+All of the interfaces described below are produced by the VIM and consumed by
+the Consumer or Administrator.
+
+Fault management interface
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This interface allows the VIM to notify the Consumer about a virtual resource
+that is affected by a fault, either within the virtual resource itself or by the
+underlying virtualization infrastructure. The messages on this interface are
+shown in :numref:`figure13` and explained in detail in the following
+subsections.
+
+Note: The information elements used in this section are described in detail in
+Section 5.4.
+
+.. figure:: images/figure13.png
+ :name: figure13
+ :width: 100%
+
+ Fault management NB I/F messages
+
+
+SubscribeRequest (Consumer -> VIM)
+__________________________________
+
+Subscription from Consumer to VIM to be notified about faults of specific
+resources. The faults to be notified about can be narrowed down using a
+subscribe filter.
+
+Parameters:
+
+- SubscribeFilter [1] (SubscribeFilterClass): Optional information to narrow
+ down the faults that shall be notified to the Consumer, for example limit to
+ specific VirtualResourceID(s), severity, or cause of the alarm.
+
+SubscribeResponse (VIM -> Consumer)
+___________________________________
+
+Response to a subscribe request message including information about the
+subscribed resources, in particular if they are in "fault/error" state.
+
+Parameters:
+
+* SubscriptionID [1] (Identifier): Unique identifier for the subscription. It
+ can be used to delete or update the subscription.
+* VirtualResourceInfo [0..*] (VirtualResourceInfoClass): Provides additional
+ information about the subscribed resources, i.e., a list of the related
+ resources, the current state of the resources, etc.
+
+FaultNotification (VIM -> Consumer)
+___________________________________
+
+Notification about a virtual resource that is affected by a fault, either within
+the virtual resource itself or by the underlying virtualization infrastructure.
+After reception of this request, the Consumer will decide on the optimal
+action to resolve the fault. This includes actions like switching to a hot
+standby virtual resource, migration of the fault virtual resource to another
+physical machine, termination of the faulty virtual resource and instantiation
+of a new virtual resource in order to provide a new hot standby resource. In
+some use cases the Consumer can leave virtual resources on failed host to be
+booted up again after fault is recovered. Existing resource management
+interfaces and messages between the Consumer and the VIM can be used for those
+actions, and there is no need to define additional actions on the Fault
+Management Interface.
+
+Parameters:
+
+* NotificationID [1] (Identifier): Unique identifier for the notification.
+* VirtualResourceInfo [1..*] (VirtualResourceInfoClass): List of faulty
+ resources with detailed information about the faults.
+
+FaultQueryRequest (Consumer -> VIM)
+___________________________________
+
+Request to find out about active alarms at the VIM. A FaultQueryFilter can be
+used to narrow down the alarms returned in the response message.
+
+Parameters:
+
+* FaultQueryFilter [1] (FaultQueryFilterClass): narrows down the
+ FaultQueryRequest, for example it limits the query to certain physical
+ resources, a certain zone, a given fault type/severity/cause, or a specific
+ FaultID.
+
+FaultQueryResponse (VIM -> Consumer)
+____________________________________
+
+List of active alarms at the VIM matching the FaultQueryFilter specified in the
+FaultQueryRequest.
+
+Parameters:
+
+* VirtualResourceInfo [0..*] (VirtualResourceInfoClass): List of faulty
+ resources. For each resource all faults including detailed information about
+ the faults are provided.
+
+NFVI maintenance
+^^^^^^^^^^^^^^^^
+
+The NFVI maintenance interfaces Consumer-VIM allows the Consumer to subscribe to
+maintenance notifications provided by the VIM. The related maintenance interface
+Administrator-VIM allows the Administrator to issue maintenance requests to the
+VIM, i.e. requesting the VIM to take appropriate actions to empty physical
+machine(s) in order to execute maintenance operations on them. The interface
+also allows the Administrator to query the state of physical machines, e.g., in
+order to get details in the current status of the maintenance operation like a
+firmware update.
+
+The messages defined in these northbound interfaces are shown in :numref:`figure14`
+and described in detail in the following subsections.
+
+.. figure:: images/figure14.png
+ :name: figure14
+ :width: 100%
+
+ NFVI maintenance NB I/F messages
+
+SubscribeRequest (Consumer -> VIM)
+__________________________________
+
+Subscription from Consumer to VIM to be notified about maintenance operations
+for specific virtual resources. The resources to be informed about can be
+narrowed down using a subscribe filter.
+
+Parameters:
+
+* SubscribeFilter [1] (SubscribeFilterClass): Information to narrow down the
+ faults that shall be notified to the Consumer, for example limit to specific
+ virtual resource type(s).
+
+SubscribeResponse (VIM -> Consumer)
+___________________________________
+
+Response to a subscribe request message, including information about the
+subscribed virtual resources, in particular if they are in "maintenance" state.
+
+Parameters:
+
+* SubscriptionID [1] (Identifier): Unique identifier for the subscription. It
+ can be used to delete or update the subscription.
+* VirtualResourceInfo [0..*] (VirtalResourceInfoClass): Provides additional
+ information about the subscribed virtual resource(s), e.g., the ID, type and
+ current state of the resource(s).
+
+MaintenanceNotification (VIM -> Consumer)
+_________________________________________
+
+Notification about a physical resource switched to "maintenance" state. After
+reception of this request, the Consumer will decide on the optimal action to
+address this request, e.g., to switch to the standby (STBY) configuration.
+
+Parameters:
+
+* VirtualResourceInfo [1..*] (VirtualResourceInfoClass): List of virtual
+ resources where the state has been changed to maintenance.
+
+StateChangeRequest (Administrator -> VIM)
+_________________________________________
+
+Request to change the state of a list of physical resources, e.g. to
+"maintenance" state, in order to prepare them for a planned maintenance
+operation.
+
+Parameters:
+
+* PhysicalResourceState [1..*] (PhysicalResourceStateClass)
+
+StateChangeResponse (VIM -> Administrator)
+__________________________________________
+
+Response message to inform the Administrator that the requested resources are
+now in maintenance state (or the operation resulted in an error) and the
+maintenance operation(s) can be executed.
+
+Parameters:
+
+* PhysicalResourceInfo [1..*] (PhysicalResourceInfoClass)
+
+StateQueryRequest (Administrator -> VIM)
+________________________________________
+
+In this procedure, the Administrator would like to get the information about
+physical machine(s), e.g. their state ("normal", "maintenance"), firmware
+version, hypervisor version, update status of firmware and hypervisor, etc. It
+can be used to check the progress during firmware update and the confirmation
+after update. A filter can be used to narrow down the resources returned in the
+response message.
+
+Parameters:
+
+* StateQueryFilter [1] (StateQueryFilterClass): narrows down the
+ StateQueryRequest, for example it limits the query to certain physical
+ resources, a certain zone, or a given resource state.
+
+StateQueryResponse (VIM -> Administrator)
+_________________________________________
+
+List of physical resources matching the filter specified in the
+StateQueryRequest.
+
+Parameters:
+
+* PhysicalResourceInfo [0..*] (PhysicalResourceInfoClass): List of physical
+ resources. For each resource, information about the current state, the
+ firmware version, etc. is provided.
+
+NFV IFA, OPNFV Doctor and AODH alarms
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This section compares the alarm interfaces of ETSI NFV IFA with the specifications
+of this document and the alarm class of AODH.
+
+ETSI NFV specifies an interface for alarms from virtualised resources in ETSI GS
+NFV-IFA 005 [ENFV]_. The interface specifies an Alarm class and two notifications plus
+operations to query alarm instances and to subscribe to the alarm notifications.
+
+The specification in this document has a structure that is very similar to the
+ETSI NFV specifications. The notifications differ in that an alarm notification
+in the NFV interface defines a single fault for a single resource while the
+notification specified in this document can contain multiple faults for
+multiple resources. The Doctor specification is lacking the detailed time stamps
+of the NFV specification essential for synchronizaion of the alarm list
+using the query operation. The detailed time stamps are also of value in the event
+and alarm history DBs.
+
+AODH defines a base class for alarms, not the notifications. This means that
+some of the dynamic attributes of the ETSI NFV alarm type, like alarmRaisedTime,
+are not applicable to the AODH alarm class but are attributes of in the actual
+notifications. (Description of these attributes will be added later.) The AODH alarm
+class is lacking some attributes present in the NFV specification, fault details
+and correlated alarms. Instead the AODH alarm class has attributes for actions,
+rules and user and project id.
+
+
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| ETSI NFV Alarm Type | OPNFV Doctor | AODH Event Alarm | Description / Comment | Recommendations |
+| | Requirement Specs | Notification | | |
++========================+========================+=====================+=============================================+=======================================+
+| alarmId | FaultId | alarm_id | Identifier of an alarm. | \- |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| \- | \- | alarm_name | Human readable alarm name. | May be added in ETSI NFV Stage 3. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| managedObjectId | VirtualResourceId | (reason) | Identifier of the affected virtual resource | \- |
+| | | | is part of the AODH reason parameter. | |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| \- | \- | user_id, project_id | User and project identifiers. | May be added in ETSI NFV Stage 3. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| alarmRaisedTime | \- | \- | Timestamp when alarm was raised. | To be added to Doctor and AODH. May |
+| | | | | be derived (e.g. in a shimlayer) from |
+| | | | | the AODH alarm history. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| alarmChangedTime | \- | \- | Timestamp when alarm was changed/updated. | see above |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| alarmClearedTime | \- | \- | Timestamp when alarm was cleared. | see above |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| eventTime | \- | \- | Timestamp when alarm was first observed by | see above |
+| | | | the Monitor. | |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| \- | EventTime | generated | Timestamp of the Notification. | Update parameter name in Doctor spec. |
+| | | | | May be added in ETSI NFV Stage 3. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| state: | VirtualResourceState: | current: ok, alarm, | ETSI NFV IFA 005/006 lists example alarm | Maintenance state is missing in AODH. |
+| E.g. Fired, Updated | E.g. normal, down | insufficient_data | states. | List of alarm states will be |
+| Cleared | maintenance, error | | | specified in ETSI NFV Stage 3. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| perceivedSeverity: | Severity (Integer) | Severity: | ETSI NFV IFA 005/006 lists example | List of alarm states will be |
+| E.g. Critical, Major, | | low (default), | perceived severity values. | specified in ETSI NFV Stage 3. |
+| Minor, Warning, | | moderate, critical | | |
+| Indeterminate, Cleared | | | | **OPNFV: Severity (Integer)**: |
+| | | | | * update OPNFV Doctor specification |
+| | | | | to *Enum* |
+| | | | | |
+| | | | | **perceivedSeverity=Indetermined**: |
+| | | | | * remove value *Indetermined* in |
+| | | | | IFA and map undefined values to |
+| | | | | “minor” severity, or |
+| | | | | * add value *indetermined* in AODH |
+| | | | | and make it the default value. |
+| | | | | |
+| | | | | **perceivedSeverity=Cleared**: |
+| | | | | * remove value *Cleared* in IFA as |
+| | | | | the information about a cleared |
+| | | | | alarm alarm can be derived from |
+| | | | | the alarm state parameter, or |
+| | | | | * add value *cleared* in AODH and |
+| | | | | set a rule that the severity is |
+| | | | | “cleared” when the state is *ok*. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| faultType | FaultType | event_type in | Type of the fault, e.g. “CPU failure” of a | OpenStack Alarming (Aodh) can use a |
+| | | reason_data | compute resource, in machine interpretable | fuzzy matching with wildcard string, |
+| | | | format. | "compute.cpu.failure". |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| N/A | N/A | type = "event" | Type of the notification. For fault | \- |
+| | | | notifications the type in AODH is “event”. | |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| probableCause | ProbableCause | \- | Probable cause of the alarm. | May be provided (e.g. in a shimlayer) |
+| | | | | based on Vitrage topology awareness / |
+| | | | | root-cause-analysis. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| isRootCause | IsRootCause | \- | Boolean indicating whether the fault is the | see above |
+| | | | root cause of other faults. | |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| correlatedAlarmId | CorrelatedFaultId | \- | List of IDs of correlated faults. | see above |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| faultDetails | FaultDetails | \- | Additional details about the fault/alarm. | FaultDetails information element will |
+| | | | | be specified in ETSI NFV Stage 3. |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+| \- | \- | action, previous | Additional AODH alarm related parameters. | \- |
++------------------------+------------------------+---------------------+---------------------------------------------+---------------------------------------+
+
+Table: Comparison of alarm attributes
+
+The primary area of improvement should be alignment of the perceived severity. This
+is important for a quick and accurate evaluation of the alarm. AODH thus should
+support also the X.733 values Critical, Major, Minor, Warning and Indeterminate.
+
+The detailed time stamps (raised, changed, cleared) which are essential for
+synchronizing the alarm list using a query operation should be added to the
+Doctor specification.
+
+Other areas that need alignment is the so called alarm state in NFV. Here we must
+however consider what can be attributes of the notification vs. what should be a
+property of the alarm instance. This will be analyzed later.
+
+.. _southbound:
+
+Detailed southbound interface specification
+-------------------------------------------
+
+This section is specifying the southbound interfaces for fault management
+between the Monitors and the Inspector.
+Although southbound interfaces should be flexible to handle various events from
+different types of Monitors, we define unified event API in order to improve
+interoperability between the Monitors and the Inspector.
+This is not limiting implementation of Monitor and Inspector as these could be
+extended in order to support failures from intelligent inspection like prediction.
+
+Note: The interface definition will be aligned with current work in ETSI NFV IFA
+working group.
+
+Fault event interface
+^^^^^^^^^^^^^^^^^^^^^
+
+This interface allows the Monitors to notify the Inspector about an event which
+was captured by the Monitor and may effect resources managed in the VIM.
+
+EventNotification
+_________________
+
+
+Event notification including fault description.
+The entity of this notification is event, and not fault or error specifically.
+This allows us to use generic event format or framework build out of Doctor project.
+The parameters below shall be mandatory, but keys in 'Details' can be optional.
+
+Parameters:
+
+* Time [1]: Datetime when the fault was observed in the Monitor.
+* Type [1]: Type of event that will be used to process correlation in Inspector.
+* Details [0..1]: Details containing additional information with Key-value pair style.
+ Keys shall be defined depending on the Type of the event.
+
+E.g.:
+
+.. code-block:: bash
+
+ {
+ 'event': {
+ 'time': '2016-04-12T08:00:00',
+ 'type': 'compute.host.down',
+ 'details': {
+ 'hostname': 'compute-1',
+ 'source': 'sample_monitor',
+ 'cause': 'link-down',
+ 'severity': 'critical',
+ 'status': 'down',
+ 'monitor_id': 'monitor-1',
+ 'monitor_event_id': '123',
+ }
+ }
+ }
+
+Optional parameters in 'Details':
+
+* Hostname: the hostname on which the event occurred.
+* Source: the display name of reporter of this event. This is not limited to monitor, other entity can be specified such as 'KVM'.
+* Cause: description of the cause of this event which could be different from the type of this event.
+* Severity: the severity of this event set by the monitor.
+* Status: the status of target object in which error occurred.
+* MonitorID: the ID of the monitor sending this event.
+* MonitorEventID: the ID of the event in the monitor. This can be used by operator while tracking the monitor log.
+* RelatedTo: the array of IDs which related to this event.
+
+Also, we can have bulk API to receive multiple events in a single HTTP POST
+message by using the 'events' wrapper as follows:
+
+.. code-block:: bash
+
+ {
+ 'events': [
+ 'event': {
+ 'time': '2016-04-12T08:00:00',
+ 'type': 'compute.host.down',
+ 'details': {},
+ },
+ 'event': {
+ 'time': '2016-04-12T08:00:00',
+ 'type': 'compute.host.nic.error',
+ 'details': {},
+ }
+ ]
+ }
+
+
+
+
+Blueprints
+----------
+
+This section is listing a first set of blueprints that have been proposed by the
+Doctor project to the open source community. Further blueprints addressing other
+gaps identified in Section 4 will be submitted at a later stage of the OPNFV. In
+this section the following definitions are used:
+
+* "Event" is a message emitted by other OpenStack services such as Nova and
+ Neutron and is consumed by the "Notification Agents" in Ceilometer.
+* "Notification" is a message generated by a "Notification Agent" in Ceilometer
+ based on an "event" and is delivered to the "Collectors" in Ceilometer that
+ store those notifications (as "sample") to the Ceilometer "Databases".
+
+Instance State Notification (Ceilometer) [*]_
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The Doctor project is planning to handle "events" and "notifications" regarding
+Resource Status; Instance State, Port State, Host State, etc. Currently,
+Ceilometer already receives "events" to identify the state of those resources,
+but it does not handle and store them yet. This is why we also need a new event
+definition to capture those resource states from "events" created by other
+services.
+
+This BP proposes to add a new compute notification state to handle events from
+an instance (server) from nova. It also creates a new meter "instance.state" in
+OpenStack.
+
+.. [*] https://etherpad.opnfv.org/p/doctor_bps
+
+Event Publisher for Alarm (Ceilometer) [*]_
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Problem statement:**
+
+ The existing "Alarm Evaluator" in OpenStack Ceilometer is periodically
+ querying/polling the databases in order to check all alarms independently from
+ other processes. This is adding additional delay to the fault notification
+ send to the Consumer, whereas one requirement of Doctor is to react on faults
+ as fast as possible.
+
+ The existing message flow is shown in :numref:`figure12`: after receiving
+ an "event", a "notification agent" (i.e. "event publisher") will send a
+ "notification" to a "Collector". The "collector" is collecting the
+ notifications and is updating the Ceilometer "Meter" database that is storing
+ information about the "sample" which is capured from original "event". The
+ "Alarm Evaluator" is periodically polling this databases then querying "Meter"
+ database based on each alarm configuration.
+
+ In the current Ceilometer implementation, there is no possibility to directly
+ trigger the "Alarm Evaluator" when a new "event" was received, but the "Alarm
+ Evaluator" will only find out that requires firing new notification to the
+ Consumer when polling the database.
+
+**Change/feature request:**
+
+ This BP proposes to add a new "event publisher for alarm", which is bypassing
+ several steps in Ceilometer in order to avoid the polling-based approach of
+ the existing Alarm Evaluator that makes notification slow to users.
+
+ After receiving an "(alarm) event" by listening on the Ceilometer message
+ queue ("notification bus"), the new "event publisher for alarm" immediately
+ hands a "notification" about this event to a new Ceilometer component
+ "Notification-driven alarm evaluator" proposed in the other BP (see Section
+ 5.6.3).
+
+ Note, the term "publisher" refers to an entity in the Ceilometer architecture
+ (it is a "notification agent"). It offers the capability to provide
+ notifications to other services outside of Ceilometer, but it is also used to
+ deliver notifications to other Ceilometer components (e.g. the "Collectors")
+ via the Ceilometer "notification bus".
+
+**Implementation detail**
+
+ * "Event publisher for alarm" is part of Ceilometer
+ * The standard AMQP message queue is used with a new topic string.
+ * No new interfaces have to be added to Ceilometer.
+ * "Event publisher for Alarm" can be configured by the Administrator of
+ Ceilometer to be used as "Notification Agent" in addition to the existing
+ "Notifier"
+ * Existing alarm mechanisms of Ceilometer can be used allowing users to
+ configure how to distribute the "notifications" transformed from "events",
+ e.g. there is an option whether an ongoing alarm is re-issued or not
+ ("repeat_actions").
+
+.. [*] https://etherpad.opnfv.org/p/doctor_bps
+
+Notification-driven alarm evaluator (Ceilometer) [*]_
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Problem statement:**
+
+The existing "Alarm Evaluator" in OpenStack Ceilometer is periodically
+querying/polling the databases in order to check all alarms independently from
+other processes. This is adding additional delay to the fault notification send
+to the Consumer, whereas one requirement of Doctor is to react on faults as fast
+as possible.
+
+**Change/feature request:**
+
+This BP is proposing to add an alternative "Notification-driven Alarm Evaluator"
+for Ceilometer that is receiving "notifications" sent by the "Event Publisher
+for Alarm" described in the other BP. Once this new "Notification-driven Alarm
+Evaluator" received "notification", it finds the "alarm" configurations which
+may relate to the "notification" by querying the "alarm" database with some keys
+i.e. resource ID, then it will evaluate each alarm with the information in that
+"notification".
+
+After the alarm evaluation, it will perform the same way as the existing "alarm
+evaluator" does for firing alarm notification to the Consumer. Similar to the
+existing Alarm Evaluator, this new "Notification-driven Alarm Evaluator" is
+aggregating and correlating different alarms which are then provided northbound
+to the Consumer via the OpenStack "Alarm Notifier". The user/administrator can
+register the alarm configuration via existing Ceilometer API [*]_. Thereby, he
+can configure whether to set an alarm or not and where to send the alarms to.
+
+**Implementation detail**
+
+* The new "Notification-driven Alarm Evaluator" is part of Ceilometer.
+* Most of the existing source code of the "Alarm Evaluator" can be re-used to
+ implement this BP
+* No additional application logic is needed
+* It will access the Ceilometer Databases just like the existing "Alarm
+ evaluator"
+* Only the polling-based approach will be replaced by a listener for
+ "notifications" provided by the "Event Publisher for Alarm" on the Ceilometer
+ "notification bus".
+* No new interfaces have to be added to Ceilometer.
+
+
+.. [*] https://etherpad.opnfv.org/p/doctor_bps
+.. [*] https://wiki.openstack.org/wiki/Ceilometer/Alerting
+
+Report host fault to update server state immediately (Nova) [*]_
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+**Problem statement:**
+
+* Nova state change for failed or unreachable host is slow and does not reliably
+ state host is down or not. This might cause same server instance to run twice
+ if action taken to evacuate instance to another host.
+* Nova state for server(s) on failed host will not change, but remains active
+ and running. This gives the user false information about server state.
+* VIM northbound interface notification of host faults towards VNFM and NFVO
+ should be in line with OpenStack state. This fault notification is a Telco
+ requirement defined in ETSI and will be implemented by OPNFV Doctor project.
+* Openstack user cannot make HA actions fast and reliably by trusting server
+ state and host state.
+
+**Proposed change:**
+
+There needs to be a new API for Admin to state host is down. This API is used to
+mark services running in host down to reflect the real situation.
+
+Example on compute node is:
+
+* When compute node is up and running:::
+
+ vm_state: activeand power_state: running
+ nova-compute state: up status: enabled
+
+* When compute node goes down and new API is called to state host is down:::
+
+ vm_state: stopped power_state: shutdown
+ nova-compute state: down status: enabled
+
+**Alternatives:**
+
+There is no attractive alternative to detect all different host faults than to
+have an external tool to detect different host faults. For this kind of tool to
+exist there needs to be new API in Nova to report fault. Currently there must be
+some kind of workarounds implemented as cannot trust or get the states from
+OpenStack fast enough.
+
+.. [*] https://blueprints.launchpad.net/nova/+spec/update-server-state-immediately
+
+Other related BPs
+^^^^^^^^^^^^^^^^^
+
+This section lists some BPs related to Doctor, but proposed by drafters outside
+the OPNFV community.
+
+pacemaker-servicegroup-driver [*]_
+__________________________________
+
+This BP will detect and report host down quite fast to OpenStack. This however
+might not work properly for example when management network has some problem and
+host reported faulty while VM still running there. This might lead to launching
+same VM instance twice causing problems. Also NB IF message needs fault reason
+and for that the source needs to be a tool that detects different kind of faults
+as Doctor will be doing. Also this BP might need enhancement to change server
+and service states correctly.
+
+.. [*] https://blueprints.launchpad.net/nova/+spec/pacemaker-servicegroup-driver
diff --git a/docs/development/requirements/06-summary.rst b/docs/development/requirements/06-summary.rst
new file mode 100644
index 00000000..61bf3f47
--- /dev/null
+++ b/docs/development/requirements/06-summary.rst
@@ -0,0 +1,24 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+Summary and conclusion
+======================
+
+The Doctor project aimed at detailing NFVI fault management and NFVI maintenance
+requirements. These are indispensable operations for an Operator, and extremely
+necessary to realize telco-grade high availability. High availability is a large
+topic; the objective of Doctor is not to realize a complete high availability
+architecture and implementation. Instead, Doctor limited itself to addressing
+the fault events in NFVI, and proposes enhancements necessary in VIM, e.g.
+OpenStack, to ensure VNFs availability in such fault events, taking a Telco VNFs
+application level management system into account.
+
+The Doctor project performed a robust analysis of the requirements from NFVI
+fault management and NFVI maintenance operation, concretely found out gaps in
+between such requirements and the current implementation of OpenStack, and
+proposed potential development plans to fill out such gaps in OpenStack.
+Blueprints are already under investigation and the next step is to fill out
+those gaps in OpenStack by code development in the coming releases.
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/07-annex.rst b/docs/development/requirements/07-annex.rst
new file mode 100644
index 00000000..c3a7899d
--- /dev/null
+++ b/docs/development/requirements/07-annex.rst
@@ -0,0 +1,129 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+.. _nfvi_faults:
+
+Annex: NFVI Faults
+=================================================
+
+Faults in the listed elements need to be immediately notified to the Consumer in
+order to perform an immediate action like live migration or switch to a hot
+standby entity. In addition, the Administrator of the host should trigger a
+maintenance action to, e.g., reboot the server or replace a defective hardware
+element.
+
+Faults can be of different severity, i.e., critical, warning, or
+info. Critical faults require immediate action as a severe degradation of the
+system has happened or is expected. Warnings indicate that the system
+performance is going down: related actions include closer (e.g. more frequent)
+monitoring of that part of the system or preparation for a cold migration to a
+backup VM. Info messages do not require any action. We also consider a type
+"maintenance", which is no real fault, but may trigger maintenance actions
+like a re-boot of the server or replacement of a faulty, but redundant HW.
+
+Faults can be gathered by, e.g., enabling SNMP and installing some open source
+tools to catch and poll SNMP. When using for example Zabbix one can also put an
+agent running on the hosts to catch any other fault. In any case of failure, the
+Administrator should be notified. The following tables provide a list of high
+level faults that are considered within the scope of the Doctor project
+requiring immediate action by the Consumer.
+
+**Compute/Storage**
+
++-------------------+----------+------------+-----------------+------------------+
+| Fault | Severity | How to | Comment | Immediate action |
+| | | detect? | | to recover |
++===================+==========+============+=================+==================+
+| Processor/CPU | Critical | Zabbix | | Switch to hot |
+| failure, CPU | | | | standby |
+| condition not ok | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Memory failure/ | Critical | Zabbix | | Switch to hot |
+| Memory condition | | (IPMI) | | standby |
+| not ok | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Network card | Critical | Zabbix/ | | Switch to hot |
+| failure, e.g. | | Ceilometer | | standby |
+| network adapter | | | | |
+| connectivity lost | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Disk crash | Info | RAID | Network storage | Inform OAM |
+| | | monitoring | is very | |
+| | | | redundant (e.g. | |
+| | | | RAID system) | |
+| | | | and can | |
+| | | | guarantee high | |
+| | | | availability | |
++-------------------+----------+------------+-----------------+------------------+
+| Storage | Critical | Zabbix | | Live migration |
+| controller | | (IPMI) | | if storage |
+| | | | | is still |
+| | | | | accessible; |
+| | | | | otherwise hot |
+| | | | | standby |
++-------------------+----------+------------+-----------------+------------------+
+| PDU/power | Critical | Zabbix/ | | Switch to hot |
+| failure, power | | Ceilometer | | standby |
+| off, server reset | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Power | Warning | SNMP | | Live migration |
+| degration, power | | | | |
+| redundancy lost, | | | | |
+| power threshold | | | | |
+| exceeded | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Chassis problem | Warning | SNMP | | Live migration |
+| (e.g. fan | | | | |
+| degraded/failed, | | | | |
+| chassis power | | | | |
+| degraded), CPU | | | | |
+| fan problem, | | | | |
+| temperature/ | | | | |
+| thermal condition | | | | |
+| not ok | | | | |
++-------------------+----------+------------+-----------------+------------------+
+| Mainboard failure | Critical | Zabbix | e.g. PCIe, SAS | Switch to hot |
+| | | (IPMI) | link failure | standby |
++-------------------+----------+------------+-----------------+------------------+
+| OS crash (e.g. | Critical | Zabbix | | Switch to hot |
+| kernel panic) | | | | standby |
++-------------------+----------+------------+-----------------+------------------+
+
+**Hypervisor**
+
++----------------+----------+------------+-------------+-------------------+
+| Fault | Severity | How to | Comment | Immediate action |
+| | | detect? | | to recover |
++================+==========+============+=============+===================+
+| System has | Critical | Zabbix | | Switch to hot |
+| restarted | | | | standby |
++----------------+----------+------------+-------------+-------------------+
+| Hypervisor | Warning/ | Zabbix/ | | Evacuation/switch |
+| failure | Critical | Ceilometer | | to hot standby |
++----------------+----------+------------+-------------+-------------------+
+| Hypervisor | Warning | Alarming | Zabbix/ | Rebuild VM |
+| status not | | service | Ceilometer | |
+| retrievable | | | unreachable | |
+| after certain | | | | |
+| period | | | | |
++----------------+----------+------------+-------------+-------------------+
+
+**Network**
+
++------------------+----------+---------+----------------+---------------------+
+| Fault | Severity | How to | Comment | Immediate action to |
+| | | detect? | | recover |
++==================+==========+=========+================+=====================+
+| SDN/OpenFlow | Critical | Ceilo- | | Switch to |
+| switch, | | meter | | hot standby |
+| controller | | | | or reconfigure |
+| degraded/failed | | | | virtual network |
+| | | | | topology |
++------------------+----------+---------+----------------+---------------------+
+| Hardware failure | Warning | SNMP | Redundancy of | Live migration if |
+| of physical | | | physical | possible otherwise |
+| switch/router | | | infrastructure | evacuation |
+| | | | is reduced or | |
+| | | | no longer | |
+| | | | available | |
++------------------+----------+---------+----------------+---------------------+
diff --git a/docs/development/requirements/99-references.rst b/docs/development/requirements/99-references.rst
new file mode 100644
index 00000000..0fd3a36a
--- /dev/null
+++ b/docs/development/requirements/99-references.rst
@@ -0,0 +1,32 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+References and bibliography
+===========================
+
+.. [DOCT] OPNFV, "Doctor" requirements project, [Online]. Available at
+ https://wiki.opnfv.org/doctor
+.. [PRED] OPNFV, "Data Collection for Failure Prediction" requirements project
+ [Online]. Available at https://wiki.opnfv.org/prediction
+.. [OPSK] OpenStack, [Online]. Available at https://www.openstack.org/
+.. [CEIL] OpenStack Telemetry (Ceilometer), [Online]. Available at
+ https://wiki.openstack.org/wiki/Ceilometer
+.. [NOVA] OpenStack Nova, [Online]. Available at
+ https://wiki.openstack.org/wiki/Nova
+.. [NEUT] OpenStack Neutron, [Online]. Available at
+ https://wiki.openstack.org/wiki/Neutron
+.. [CIND] OpenStack Cinder, [Online]. Available at
+ https://wiki.openstack.org/wiki/Cinder
+.. [MONA] OpenStack Monasca, [Online], Available at
+ https://wiki.openstack.org/wiki/Monasca
+.. [OSAG] OpenStack Cloud Administrator Guide, [Online]. Available at
+ http://docs.openstack.org/admin-guide-cloud/content/
+.. [ZABB] ZABBIX, the Enterprise-class Monitoring Solution for Everyone,
+ [Online]. Available at http://www.zabbix.com/
+.. [ENFV] ETSI NFV, [Online]. Available at
+ http://www.etsi.org/technologies-clusters/technologies/nfv
+
+
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/glossary.rst b/docs/development/requirements/glossary.rst
new file mode 100644
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+++ b/docs/development/requirements/glossary.rst
@@ -0,0 +1,89 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+**Definition of terms**
+
+Different SDOs and communities use different terminology related to
+NFV/Cloud/SDN. This list tries to define an OPNFV terminology,
+mapping/translating the OPNFV terms to terminology used in other contexts.
+
+
+.. glossary::
+
+ ACT-STBY configuration
+ Failover configuration common in Telco deployments. It enables the
+ operator to use a standby (STBY) instance to take over the functionality
+ of a failed active (ACT) instance.
+
+ Administrator
+ Administrator of the system, e.g. OAM in Telco context.
+
+ Consumer
+ User-side Manager; consumer of the interfaces produced by the VIM; VNFM,
+ NFVO, or Orchestrator in ETSI NFV [ENFV]_ terminology.
+
+ EPC
+ Evolved Packet Core, the main component of the core network architecture
+ of 3GPP's LTE communication standard.
+
+ MME
+ Mobility Management Entity, an entity in the EPC dedicated to mobility
+ management.
+
+ NFV
+ Network Function Virtualization
+
+ NFVI
+ Network Function Virtualization Infrastructure; totality of all hardware
+ and software components which build up the environment in which VNFs are
+ deployed.
+
+ S/P-GW
+ Serving/PDN-Gateway, two entities in the EPC dedicated to routing user
+ data packets and providing connectivity from the UE to external packet
+ data networks (PDN), respectively.
+
+ Physical resource
+ Actual resources in NFVI; not visible to Consumer.
+
+ VNFM
+ Virtualized Network Function Manager; functional block that is
+ responsible for the lifecycle management of VNF.
+
+ NFVO
+ Network Functions Virtualization Orchestrator; functional block that
+ manages the Network Service (NS) lifecycle and coordinates the
+ management of NS lifecycle, VNF lifecycle (supported by the VNFM) and
+ NFVI resources (supported by the VIM) to ensure an optimized allocation
+ of the necessary resources and connectivity.
+
+ VIM
+ Virtualized Infrastructure Manager; functional block that is responsible
+ for controlling and managing the NFVI compute, storage and network
+ resources, usually within one operator's Infrastructure Domain, e.g.
+ NFVI Point of Presence (NFVI-PoP).
+
+ Virtual Machine (VM)
+ Virtualized computation environment that behaves very much like a
+ physical computer/server.
+
+ Virtual network
+ Virtual network routes information among the network interfaces of VM
+ instances and physical network interfaces, providing the necessary
+ connectivity.
+
+ Virtual resource
+ A Virtual Machine (VM), a virtual network, or virtualized storage;
+ Offered resources to "Consumer" as result of infrastructure
+ virtualization; visible to Consumer.
+
+ Virtual Storage
+ Virtualized non-volatile storage allocated to a VM.
+
+ VNF
+ Virtualized Network Function. Implementation of a Network Function that
+ can be deployed on a Network Function Virtualization Infrastructure
+ (NFVI).
+
+..
+ vim: set tabstop=4 expandtab textwidth=80:
diff --git a/docs/development/requirements/images/LICENSE b/docs/development/requirements/images/LICENSE
new file mode 100644
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+++ b/docs/development/requirements/images/LICENSE
@@ -0,0 +1,14 @@
+Copyright 2017 Open Platform for NFV Project, Inc. and its contributors
+
+Open Platform for NFV Project Documentation License
+===================================================
+Any documentation developed by the "Open Platform for NFV Project"
+is licensed under a Creative Commons Attribution 4.0 International License.
+You should have received a copy of the license along with this. If not,
+see <http://creativecommons.org/licenses/by/4.0/>.
+
+Unless required by applicable law or agreed to in writing, documentation
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
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diff --git a/docs/development/requirements/index.rst b/docs/development/requirements/index.rst
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@@ -0,0 +1,62 @@
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+.. http://creativecommons.org/licenses/by/4.0
+
+****************************************
+Doctor: Fault Management and Maintenance
+****************************************
+
+:Project: Doctor, https://wiki.opnfv.org/doctor
+:Editors: Ashiq Khan (NTT DOCOMO), Gerald Kunzmann (NTT DOCOMO)
+:Authors: Ryota Mibu (NEC), Carlos Goncalves (NEC), Tomi Juvonen (Nokia),
+ Tommy Lindgren (Ericsson), Bertrand Souville (NTT DOCOMO),
+ Balazs Gibizer (Ericsson), Ildiko Vancsa (Ericsson) and others.
+
+:Abstract: Doctor is an OPNFV requirement project [DOCT]_. Its scope is NFVI
+ fault management, and maintenance and it aims at developing and
+ realizing the consequent implementation for the OPNFV reference
+ platform.
+
+ This deliverable is introducing the use cases and operational
+ scenarios for Fault Management considered in the Doctor project.
+ From the general features, a high level architecture describing
+ logical building blocks and interfaces is derived. Finally,
+ a detailed implementation is introduced, based on available open
+ source components, and a related gap analysis is done as part of
+ this project. The implementation plan finally discusses an initial
+ realization for a NFVI fault management and maintenance solution in
+ open source software.
+
+:History:
+
+ ========== =====================================================
+ Date Description
+ ========== =====================================================
+ 02.12.2014 Project creation
+ 14.04.2015 Initial version of the deliverable uploaded to Gerrit
+ 18.05.2015 Stable version of the Doctor deliverable
+ 25.02.2016 Updated version for the Brahmaputra release
+ 26.09.2016 Updated version for the Colorado release
+ xx.xx.2017 Updated version for the Danube release
+ ========== =====================================================
+
+.. raw:: latex
+
+ \newpage
+
+.. include::
+ glossary.rst
+
+.. toctree::
+ :maxdepth: 4
+ :numbered:
+
+ 01-intro.rst
+ 02-use_cases.rst
+ 03-architecture.rst
+ 04-gaps.rst
+ 05-implementation.rst
+ 06-summary.rst
+ 07-annex.rst
+
+.. include::
+ 99-references.rst