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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..b6e9552 --- /dev/null +++ b/doc/02-Background_and_Terminologies.rst @@ -0,0 +1,362 @@ +General Requirements Background and Terminology +----------------------------------------------- + +Terminologies and definitions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +- **NFVI** is abbreviation for Network Function Virtualization + Infrastructure; sometimes it is also referred as data plane in this + document. +- **VIM** is abbreviation for Virtual Infrastructure Management; + sometimes it is also referred as control plane in this document. +- **Operators** are network service providers and Virtual Network + Function (VNF) providers. +- **End-Users** are subscribers of Operator's services. +- **Network Service** is a service provided by an Operator to its + End-users using a set of (virtualized) Network Functions +- **Infrastructure Services** are those provided by the NFV + Infrastructure and the Management & Orchestration functions to the + VNFs. I.e. these are the virtual resources as perceived by the VNFs. +- **Smooth Upgrade** means that the upgrade results in no service + outage for the end-users. +- **Rolling Upgrade** is an upgrade strategy that upgrades each node or + a subset of nodes in a wave rolling style through the data centre. It + is a popular upgrade strategy to maintains service availability. +- **Parallel Universe** is 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 later. +- **Infrastructure Resource Model** ==(suggested by MT)== is identified + as: physical resources, virtualization facility resources and virtual + resources. +- **Physical Resources** are the hardware of the infrastructure, may + also includes the firmware that enable the hardware. +- **Virtual Resources** are resources provided as services built on top + of the physical resources via the virtualization facilities; in our + case, they are the components that VNF entities are built on, 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 Facilities** are resources that enable the creation + of virtual environments on top of the physical resources, e.g. + hypervisor, OpenStack, etc. + +Upgrade Objects +~~~~~~~~~~~~~~~ + +Physical Resource +^^^^^^^^^^^^^^^^^ + +| Most of the cloud infrastructures support dynamic addition/removal of + hardware. A hardware upgrade could be done by removing the old + hardware node and adding the new one. Upgrade a physical resource, + like upgrade the firmware and modify the configuration data, may + 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 considered as virtualization + facility resource, but from escalator perspective, it is better + considered it as part of 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 switch/router allow you to upgrade its + 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 services interruption if the virtual resource is not + redudant. +| Updating 2 might lead to control plane services interruption if not an + HA deployment. + +**Storage node** + +1. OS kernel, optional, not all storage node allow you to upgrade its 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 + redudant. +| 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 + +- different software packages +- different funtions - 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 +- 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. + +- different versions of the same software package +- major version changes - they may introduce incompatibilities. Even + when there are backward compatibility requirements changes may cause + issues at graceful rollback +- minor version changes - they must not introduce incompatibility + between versions, these should be primarily bug fixes, so live + patches should be possible + +- different installations of the same software package +- 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 +- using the same installation options - they often reflect that the are + used by redundant entities across space + +- different distribution possibilities in space - same or different + availability zones, multi-site, geo-redundancy + +- different entities running from the same installation of a software + package +- using different startup options - they may reflect different users so + redundancy may not be an issues between them +- using same startup options - they often reflect redundant + entities==== + +Upgrade duration +~~~~~~~~~~~~~~~~ + +As the OPNFV end-users are primarily Telco 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 OpenStack 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 fulfill ceratin requirements. Since +this is only possible on the long run we target first upgrades from +version to version for the different VIM services. + +**Questions:** + +#. | 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.== + +#. | 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.== + +#. | 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. + +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.== +| **Two possible types of failures can happen during an upgrade** + +#. 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. +#. 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 + ent-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: +| SAL1: 5-6 seconds +| SAL2: 10-15 seconds +| 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 + switchover 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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