Refact Terminology chapter

The change mainly re-list all terminologies in alphabetical order.

Change-Id: I10f93d140b2cea48dd09f5cdcddea3c71a947543

1 files changed, 83 insertions, 68 deletions

diff --git a/docs/requirements/102-Terminologies.rst b/docs/requirements/102-Terminologies.rst
index 221196b..ccddcb1 100644
--- a/docs/requirements/102-Terminologies.rst
+++ b/docs/requirements/102-Terminologies.rst
@@ -5,30 +5,59 @@ Terminology
 Terminologies
 =============
 
-Operator
-  The term refers to network service providers and Virtual Network
-  Function (VNF) providers.
+Backup
+  The term refers to making a copy of the system persistent data to a storage,
+  so that it can be used to restore the system or a given part of it to the same
+  state as it was when the backup was created. Restoring from backup will lose
+  volatile states like CPU and memory content. Changes made to the system from
+  the moment the backup was created to the moment it is used to restore the
+  (sub)system are also lost in the restoration process. 
+
+Carrier Grade
+  The refers to a system, or a hardware or software component that is extremely
+  reliable, well tested and proven in its capabilities. Carrier grade systems are
+  tested and engineered to meet or exceed "five nines" high availability standards,
+  and provide very fast fault recovery through redundancy (normally less than 50 
+  milliseconds). Sometimes, Carrier grade is also referred as Carrier Class.
+
+Downgrade
+  The term refers to an upgrade operation in which an earlier version of the
+  software is restored through the upgrade procedure. Compared to rollback,
+  Downgrade is normally initiated with Operator, and it is allowed to select any
+  earlier version, providing the compatibility of the versions is met or upgrade
+  strategies are allowed (whether service outage or data lost can be tolerant.)
 
 End-User
   The term refers to a subscriber of the Operator's services.
 
-Network Service
-  The term refers to a service provided by an Operator to its
-  end-users using a set of (virtualized) Network Functions
+High Availability(HA)
+  High Availability refers to a system or component that is continuously
+  operational for a desirably long length of time even a part of it is out of
+  service. Carrier Grade Availability is a typical HA example. HA system is popular
+  in Operator's data center for critical tasks. Non-HA system is normally deployed
+  for experimental or in-critical tasks in favor of its simplicity.
 
 Infrastructure Services
   The term refers to services provided by the NFV Infrastructure to the VNFs
   as required by the Management & Orchestration functions and especially the VIM.
   I.e. these are the virtual resources as perceived by the VNFs.
 
-Smooth Upgrade
-  The term refers to an upgrade that results in no service outage
-  for the end-users.
+Infrastructure Resource Model
+  The term refers to the representation of infrastructure resources,
+  namely: the physical resources, the virtualization
+  facility resources and the virtual resources.
 
-Rolling Upgrade
-  The term refers to an upgrade strategy, which upgrades a node or a subset
-  of nodes at a time in a wave style rolling through the data centre. It
-  is a popular upgrade strategy to maintain service availability.
+Network Service
+  The term refers to a service provided by an Operator to its
+  end-users using a set of (virtualized) Network Functions
+
+Operator
+  The term refers to network service providers and Virtual Network
+  Function (VNF) providers.
+
+Outage
+  The terms refers to the period of time when a given service is not available
+  to End-Users.
 
 Parallel Universe Upgrade
   The term refers to an upgrade strategy, which creates and deploys
@@ -36,25 +65,42 @@ Parallel Universe Upgrade
   system continues running. The state of the old system is transferred
   to the new system after sufficient testing of the new system.
 
-Infrastructure Resource Model
-  The term refers to the representation of infrastructure resources,
-  namely: the physical resources, the virtualization
-  facility resources and the virtual resources.
-
 Physical Resource
   The term refers to a piece of hardware in the NFV infrastructure that may
   also include firmware enabling this piece of hardware.
 
-Virtual Resource
-  The term refers to a resource, which is provided as services built on top
-  of the physical resources via the virtualization facilities; in particular,
-  virtual resources are the resources on which VNFs are deployed. Examples of
-  virtual resources are: VMs, virtual switches, virtual routers, virtual disks.
+Restore
+  The term refers to a failure handling strategy that reverts the changes
+  done, for example, by an upgrade by restoring the system from some backup
+  data. This results in the loss of any change and data persisted after the
+  backup was been taken. To recover those additional measures need to be taken
+  if necessary (e.g. Rollforward).
 
-Visualization Facility
-  The term refers to a resource that enables the creation
-  of virtual environments on top of the physical resources, e.g.
-  hypervisor, OpenStack, etc.
+Rollback
+  The term refers to a failure handling strategy that reverts the changes
+  done by a potentially failed upgrade execution one by one in a reverse order.
+  I.e. it is like undoing the changes done by the upgrade.
+
+Rollforward
+  The term refers to a failure handling strategy applied after a restore
+  (from a backup) operation to recover any loss of data persisted between
+  the time the backup has been taken and the moment it is restored. Rollforward
+  requires that data that needs to survive the restore operation is logged at
+  a location not impacted by the restore so that it can be re-applied to the
+  system after its restoration from the backup.
+
+Rolling Upgrade
+  The term refers to an upgrade strategy, which upgrades a node or a subset
+  of nodes at a time in a wave style rolling through the data centre. It
+  is a popular upgrade strategy to maintain service availability.
+
+Smooth Upgrade
+  The term refers to an upgrade that results in no service outage
+  for the end-users.
+
+Snapshot
+  The term refer to the state of a system at a particular point in time, or
+  the action of capturing such a state.
 
 Upgrade Campaign
   The term refers to a choreography that describes how the upgrade should
@@ -69,48 +115,18 @@ Upgrade Duration
   upgrade campaign has started until it has been committed. Depending on
   the upgrade strategy, the state of the configuration and the upgrade target
   some parts of the system may be in a more vulnerable state with respect to
-  service availbility.
-
-Outage
-  The period of time during which a given service is not provided is referred
-  as the outage of that given service. If a subsystem or the entire system
-  does not provide any service, it is the outage of the given subsystem or the
-  system. Smooth upgrade means upgrade with no outage for the user plane, i.e.
-  no VNF should experience service outage.
-
-Rollback
-  The term refers to a failure handling strategy that reverts the changes
-  done by a potentially failed upgrade execution one by one in a reverse order.
-  I.e. it is like undoing the changes done by the upgrade.
+  service availability.
 
-Backup
-  The term refers to data persisted to a storage, so that it can be used to
-  restore the system or a given part of it in the same state as it was when the
-  backup was created assuming a cold restart. Changes made to the system from
-  the moment the backup was created till the moment it is used to restore the
-  (sub)system are lost in the restoration process.
-
-Restore
-  The term refers to a failure handling strategy that reverts the changes
-  done, for example, by an upgrade by restoring the system from some backup
-  data. This results in the loss of any change and data persisted after the
-  backup was been taken. To recover those additional measures need to be taken
-  if necessary (e.g. rollforward).
-
-Rollforward
-  The term refers to a failure handling strategy applied after a restore
-  (from a backup) opertaion to recover any loss of data persisted between
-  the time the backup has been taken and the moment it is restored. Rollforward
-  requires that data that needs to survive the restore operation is logged at
-  a location not impacted by the restore so that it can be re-applied to the
-  system after its restoration from the backup.
+Virtualization Facility
+  The term refers to a resource that enables the creation
+  of virtual environments on top of the physical resources, e.g.
+  hypervisor, OpenStack, etc.
 
-Downgrade
-  The term refers to an upgrade in which an earlier version of the software
-  is restored through the upgrade procedure. A system can be downgraded to any
-  earlier version and the compatibility of the versions will determine the
-  applicable upgrade strategies and whether service outage can be avoided.
-  In particular any data conversion needs special attention.
+Virtual Resource
+  The term refers to a resource, which is provided as services built on top
+  of the physical resources via the virtualization facilities; in particular,
+  virtual resources are the resources on which VNFs are deployed. Examples of
+  virtual resources are: VMs, virtual switches, virtual routers, virtual disks.
 
 Abbreviations
 =============
@@ -126,4 +142,3 @@ VIM
   sometimes it is also referred as control plane in this document.
   The VIM controls and manages the NFVI compute, network and storage
   resources to provide the required virtual resources to the VNFs.
-