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===========
Terminology
===========
Terminologies
=============
Operator
The term refers to network service providers and Virtual Network
Function (VNF) providers.
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
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.
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.
Parallel Universe Upgrade
The term refers to an upgrade strategy, which creates and deploys
a new universe - a system with the new configuration - while the old
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.
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.
Upgrade Campaign
The term refers to a choreography that describes how the upgrade should
be performed in terms of its targets (i.e. upgrade objects), the
steps/actions required of upgrading each, and the coordination of these
steps so that service availability can be maintained. It is an input to an
upgrade tool (Escalator) to carry out the upgrade.
Upgrade Duration
The duration of an upgrade characterized by the time elapsed between its
initiation and its completion. E.g. from the moment the execution of an
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.
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.
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.
Abbreviations
=============
NFVI
The term is an abbreviation for Network Function Virtualization
Infrastructure; sometimes it is also referred as data plane in this
document. The NFVI provides the virtual resources to the virtual
network functions under the control of the VIM.
VIM
The term is an abbreviation for Virtual Infrastructure Manager;
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.
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