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diff --git a/doc/02-Background_and_Terminologies.rst b/doc/02-Background_and_Terminologies.rst new file mode 100644 index 0000000..afb392f --- /dev/null +++ b/doc/02-Background_and_Terminologies.rst @@ -0,0 +1,458 @@ +General Requirements Background and Terminology
+-----------------------------------------------
+
+Terminologies and definitions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+NFVI
+ The term is an abbreviation for Network Function Virtualization
+ Infrastructure; sometimes it is also referred as data plane in this
+ document.
+
+VIM
+ The term is an abbreviation for Virtual Infrastructure Management;
+ sometimes it is also referred as control plane in this document.
+
+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 and the
+ the Management & Orchestration functions to the VNFs. 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 that upgrades each node or
+ a subset of nodes in a wave style rolling through the data centre. It
+ is a popular upgrade strategy to maintain service availability.
+
+Parallel Universe
+ The term refers to an upgrade strategy that 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 hardware pieces of the NFV infrastructure, which may
+ also include the firmware which enables the 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,
+ they are the resources on which VNF entities are deployed, e.g.
+ the VMs, virtual switches, virtual routers, virtual disks etc.
+
+.. <MT> I don't think the VNF is the virtual resource. Virtual
+ resources are the VMs, virtual switches, virtual routers, virtual
+ disks etc. The VNF uses them, but I don't think they are equal. The
+ VIM doesn't manage the VNF, but it does manage virtual resources.
+
+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 Plan (or 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 Objects
+~~~~~~~~~~~~~~~
+
+Physical Resource
+^^^^^^^^^^^^^^^^^
+
+Most of cloud infrastructures support dynamic addition/removal of
+hardware. A hardware upgrade could be done by adding the new
+hardware node and removing the old one. From the persepctive of smooth
+upgrade the orchestration/scheduling of this actions is the primary concern.
+Upgrading a physical resource,
+like upgrading its firmware and/or modify its configuration data, may
+also be considered in the future.
+
+
+Virtual Resources
+^^^^^^^^^^^^^^^^^
+
+Virtual resource upgrade mainly done by users. OPNFV may facilitate
+the activity, but suggest to have it in long term roadmap instead of
+initiate release.
+
+.. <MT> same comment here: I don't think the VNF is the virtual
+ resource. Virtual resources are the VMs, virtual switches, virtual
+ routers, virtual disks etc. The VNF uses them, but I don't think they
+ are equal. For example if by some reason the hypervisor is changed and
+ the current VMs cannot be migrated to the new hypervisor, they are
+ incompatible, then the VMs need to be upgraded too. This is not
+ something the NFVI user (i.e. VNFs ) would even know about.
+
+
+Virtualization Facility Resources
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Based on the functionality they provide, virtualization facility
+resources could be divided into computing node, networking node,
+storage node and management node.
+
+The possible upgrade objects in these nodes are addressed below:
+(Note: hardware based virtualization may be considered as virtualization
+facility resource, but from escalator perspective, it is better to
+consider it as part of the hardware upgrade. )
+
+**Computing node**
+
+1. OS Kernel
+
+2. Hypvervisor and virtual switch
+
+3. Other kernel modules, like driver
+
+4. User space software packages, like nova-compute agents and other
+ control plane programs.
+
+Updating 1 and 2 will cause the loss of virtualzation functionality of
+the compute node, which may lead to data plane services interruption
+if the virtual resource is not redudant.
+
+Updating 3 might result the same.
+
+Updating 4 might lead to control plane services interruption if not an
+HA deployment.
+
+**Networking node**
+
+1. OS kernel, optional, not all switches/routers allow the upgrade their
+ OS since it is more like a firmware than a generic OS.
+
+2. User space software package, like neutron agents and other control
+ plane programs
+
+Updating 1 if allowed will cause a node reboot and therefore leads to
+data plane service interruption if the virtual resource is not
+redundant.
+
+Updating 2 might lead to control plane services interruption if not an
+HA deployment.
+
+**Storage node**
+
+1. OS kernel, optional, not all storage nodes allow the upgrade their OS
+ since it is more like a firmware than a generic OS.
+
+2. Kernel modules
+
+3. User space software packages, control plane programs
+
+Updating 1 if allowed will cause a node reboot and therefore leads to
+data plane services interruption if the virtual resource is not
+redundant.
+
+Update 2 might result in the same.
+
+Updating 3 might lead to control plane services interruption if not an
+HA deployment.
+
+**Management node**
+
+1. OS Kernel
+
+2. Kernel modules, like driver
+
+3. User space software packages, like database, message queue and
+ control plane programs.
+
+Updating 1 will cause a node reboot and therefore leads to control
+plane services interruption if not an HA deployment. Updating 2 might
+result in the same.
+
+Updating 3 might lead to control plane services interruption if not an
+HA deployment.
+
+Upgrade Span
+~~~~~~~~~~~~
+
+**Major Upgrade**
+
+Upgrades between major releases may introducing significant changes in
+function, configuration and data, such as the upgrade of OPNFV from
+Arno to Brahmaputra.
+
+**Minor Upgrade**
+
+Upgrades inside one major releases which would not leads to changing
+the structure of the platform and may not infect the schema of the
+system data.
+
+Upgrade Granularity
+~~~~~~~~~~~~~~~~~~~
+
+Physical/Hardware Dimension
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Support full / partial upgrade for data centre, cluster, zone. Because
+of the upgrade of a data centre or a zone, it may be divided into
+several batches. The upgrade of a cloud environment (cluster) may also
+be partial. For example, in one cloud environment running a number of
+VNFs, we may just try one of them to check the stability and
+performance, before we upgrade all of them.
+
+Software Dimension
+^^^^^^^^^^^^^^^^^^
+
+- The upgrade of host OS or kernel may need a 'hot migration'
+- The upgrade of OpenStack’s components
+
+ i.the one-shot upgrade of all components
+
+ ii.the partial upgrade (or bugfix patch) which only affects some
+ components (e.g., computing, storage, network, database, message
+ queue, etc.)
+
+.. <MT> this section seems to overlap with 2.1.
+ I can see the following dimensions for the software.
+
+.. <MT> different software packages
+
+.. <MT> different functions - Considering that the target versions of all
+ software are compatible the upgrade needs to ensure that any
+ dependencies between SW and therefore packages are taken into account
+ in the upgrade plan, i.e. no version mismatch occurs during the
+ upgrade therefore dependencies are not broken
+
+.. <MT> same function - This is an upgrade specific question if different
+ versions can coexist in the system when a SW is being upgraded from
+ one version to another. This is particularly important for stateful
+ functions e.g. storage, networking, control services. The upgrade
+ method must consider the compatibility of the redundant entities.
+
+.. <MT> different versions of the same software package
+
+.. <MT> major version changes - they may introduce incompatibilities. Even
+ when there are backward compatibility requirements changes may cause
+ issues at graceful roll-back
+
+.. <MT> minor version changes - they must not introduce incompatibility
+ between versions, these should be primarily bug fixes, so live
+ patches should be possible
+
+.. <MT> different installations of the same software package
+
+.. <MT> using different installation options - they may reflect different
+ users with different needs so redundancy issues are less likely
+ between installations of different options; but they could be the
+ reflection of the heterogeneous system in which case they may provide
+ redundancy for higher availability, i.e. deeper inspection is needed
+
+.. <MT> using the same installation options - they often reflect that the are
+ used by redundant entities across space
+
+.. <MT> different distribution possibilities in space - same or different
+ availability zones, multi-site, geo-redundancy
+
+.. <MT> different entities running from the same installation of a software
+ package
+
+.. <MT> using different start-up options - they may reflect different users so
+ redundancy may not be an issues between them
+
+.. <MT> using same start-up options - they often reflect redundant
+ entities
+
+Upgrade duration
+~~~~~~~~~~~~~~~~
+
+As the OPNFV end-users are primarily Telecom operators, the network
+services provided by the VNFs deployed on the NFVI should meet the
+requirement of 'Carrier Grade'.::
+
+ In telecommunication, a "carrier grade" or"carrier class" 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). [from wikipedia.org]
+
+"five nines" means working all the time in ONE YEAR except 5'15".
+
+::
+
+ We have learnt that a well prepared upgrade of OpenStack needs 10
+ minutes. The major time slot in the outage time is used spent on
+ synchronizing the database. [from ' Ten minutes OpenStack Upgrade? Done!
+ ' by Symantec]
+
+This 10 minutes of downtime of the OpenStack services however did not impact the
+users, i.e. the VMs running on the compute nodes. This was the outage of
+the control plane only. On the other hand with respect to the
+preparations this was a manually tailored upgrade specific to the
+particular deployment and the versions of each OpenStack service.
+
+The project targets to achieve a more generic methodology, which however
+requires that the upgrade objects fulfil certain requirements. Since
+this is only possible on the long run we target first the upgrade
+of the different VIM services from version to version.
+
+**Questions:**
+
+1. Can we manage to upgrade OPNFV in only 5 minutes?
+
+.. <MT> The first question is whether we have the same carrier grade
+ requirement on the control plane as on the user plane. I.e. how
+ much control plane outage we can/willing to tolerate?
+ In the above case probably if the database is only half of the size
+ we can do the upgrade in 5 minutes, but is that good? It also means
+ that if the database is twice as much then the outage is 20
+ minutes.
+ For the user plane we should go for less as with two release yearly
+ that means 10 minutes outage per year.
+
+.. <Malla> 10 minutes outage per year to the users? Plus, if we take
+ control plane into the consideration, then total outage will be
+ more than 10 minute in whole network, right?
+
+.. <MT> The control plane outage does not have to cause outage to
+ the users, but it may of course depending on the size of the system
+ as it's more likely that there's a failure that needs to be handled
+ by the control plane.
+
+2. Is it acceptable for end users ? Such as a planed service
+ interruption will lasting more than ten minutes for software
+ upgrade.
+
+.. <MT> For user plane, no it's not acceptable in case of
+ carrier-grade. The 5' 15" downtime should include unplanned and
+ planned downtimes.
+
+.. <Malla> I go agree with Maria, it is not acceptable.
+
+3. Will any VNFs still working well when VIM is down?
+
+.. <MT> In case of OpenStack it seems yes. .:)
+
+The maximum duration of an upgrade
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The duration of an upgrade is related to and proportional with the
+scale and the complexity of the OPNFV platform as well as the
+granularity (in function and in space) of the upgrade.
+
+.. <Malla> Also, if is a partial upgrade like module upgrade, it depends
+ also on the OPNFV modules and their tight connection entities as well.
+
+.. <MT> Since the maintenance window is shrinking and becoming non-existent
+ the duration of the upgrade is secondary to the requirement of smooth upgrade.
+ But probably we want to be able to put a time constraint on each upgrade
+ during which it must complete otherwise it is considered failed and the system
+ should be rolled back. I.e. in case of automatic execution it might not be clear
+ if an upgrade is long or just hanging. The time constraints may be a function
+ of the size of the system in terms of the upgrade object(s).
+
+The maximum duration of a roll back when an upgrade is failed
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The duration of a roll back is short than the corresponding upgrade. It
+depends on the duration of restore the software and configure data from
+pre-upgrade backup / snapshot.
+
+.. <MT> During the upgrade process two types of failure may happen:
+ In case we can recover from the failure by undoing the upgrade
+ actions it is possible to roll back the already executed part of the
+ upgrade in graceful manner introducing no more service outage than
+ what was introduced during the upgrade. Such a graceful roll back
+ requires typically the same amount of time as the executed portion of
+ the upgrade and impose minimal state/data loss.
+
+.. <MT> Requirement: It should be possible to roll back gracefully the
+ failed upgrade of stateful services of the control plane.
+ In case we cannot recover from the failure by just undoing the
+ upgrade actions, we have to restore the upgraded entities from their
+ backed up state. In other terms the system falls back to an earlier
+ state, which is typically a faster recovery procedure than graceful
+ roll back and depending on the statefulness of the entities involved it
+ may result in significant state/data loss.
+
+.. <MT> Two possible types of failures can happen during an upgrade
+
+.. <MT> We can recover from the failure that occurred in the upgrade process:
+ In this case, a graceful rolling back of the executed part of the
+ upgrade may be possible which would "undo" the executed part in a
+ similar fashion. Thus, such a roll back introduces no more service
+ outage during an upgrade than the executed part introduced. This
+ process typically requires the same amount of time as the executed
+ portion of the upgrade and impose minimal state/data loss.
+
+.. <MT> We cannot recover from the failure that occurred in the upgrade
+ process: In this case, the system needs to fall back to an earlier
+ consistent state by reloading this backed-up state. This is typically
+ a faster recovery procedure than the graceful roll back, but can cause
+ state/data loss. The state/data loss usually depends on the
+ statefulness of the entities whose state is restored from the backup.
+
+The maximum duration of a VNF interruption (Service outage)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Since not the entire process of a smooth upgrade will affect the VNFs,
+the duration of the VNF interruption may be shorter than the duration
+of the upgrade. In some cases, the VNF running without the control
+from of the VIM is acceptable.
+
+.. <MT> Should require explicitly that the NFVI should be able to
+ provide its services to the VNFs independent of the control plane?
+
+.. <MT> Requirement: The upgrade of the control plane must not cause
+ interruption of the NFVI services provided to the VNFs.
+
+.. <MT> With respect to carrier-grade the yearly service outage of the
+ VNF should not exceed 5' 15" regardless whether it is planned or
+ unplanned outage. Considering the HA requirements TL-9000 requires an
+ end-to-end service recovery time of 15 seconds based on which the ETSI
+ GS NFV-REL 001 V1.1.1 (2015-01) document defines three service
+ availability levels (SAL). The proposed example service recovery times
+ for these levels are:
+
+.. <MT> SAL1: 5-6 seconds
+
+.. <MT> SAL2: 10-15 seconds
+
+.. <MT> SAL3: 20-25 seconds
+
+.. <Pva> my comment was actually that the downtime metrics of the
+ underlying elements, components and services are small fraction of the
+ total E2E service availability time. No-one on the E2E service path
+ will get the whole downtime allocation (in this context it includes
+ upgrade process related outages for the services provided by VIM etc.
+ elements that are subject to upgrade process).
+
+.. <MT> So what you are saying is that the upgrade of any entity
+ (component, service) shouldn't cause even this much service
+ interruption. This was the reason I brought these figures here as well
+ that they are posing some kind of upper-upper boundary. Ideally the
+ interruption is in the millisecond range i.e. no more than a
+ switch-over or a live migration.
+
+.. <MT> Requirement: Any interruption caused to the VNF by the upgrade
+ of the NFVI should be in the sub-second range.
+
+.. <MT]> In the future we also need to consider the upgrade of the NFVI,
+ i.e. HW, firmware, hypervisors, host OS etc.
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