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diff --git a/Scenario_1/scenario_analysis_VNF_external_interface.rst b/Scenario_1/scenario_analysis_VNF_external_interface.rst deleted file mode 100644 index c634c20..0000000 --- a/Scenario_1/scenario_analysis_VNF_external_interface.rst +++ /dev/null @@ -1,99 +0,0 @@ -3. Communication Interfaces for VNF HA schemes -=========================================================== - -This section will discuss some general issues about communication interfaces -in the VNF HA schemes. In sections 2, the usecases of both stateful and -stateless VNFs are discussed. While in this section, we would like to discuss -some specific issues which are quite general for all the usecases proposed -in the previous sections. - -3.1. VNF External Interfacece - -Regardless whether the VNF is stateful or stateless, all the VNFCs should act as -a union from the perspective of the outside world. That means all the VNFCs should -share a common interface where the outside modules (e.g., the other VNFs) can -access the service from. There could be multiple solutions for this share of IP -interface. However, all of this sharing and switching of IP address should be -ignorant to the outside modules. - -There are several approaches for the VNFs to share the interfaces. A few of them -are listed as follows and will be discussed in detail. - -1) IP address of VMs for active/stand-by VM. - -2) Load balancers for active/active use cases - -Note that combinition of these two approaches is also feasible. - -For active/standby VNFCs, there is a common IP address shared by the VMs hosting -the active and standby VNFCs, so that they look as one instance from outside. -The HA manager will manage the assignment of the IP address to the VMs. -(The HA manager may not be aware of this, I.e. the address may be configured -and the active/standby state management is linked to the possession of the IP -address, i.e. the active VNFC claims it as part of becoming active.) Only the -active one possesses the IP address. And when failover happens, the standby -is set to be active and can take possession of the IP address to continue traffic -process. - -..[MT] In general I would rather say that the IP address is managed by the HA -manager and not provided. But as a concrete use case "provide" works fine. -So it depends how you want to use this text. -..[fq] Agree, Thank you! - -For active/active VNFCs, a LB(Load Balancer) could be used. In such scenario, there -could be two cases for the deployment and usage of LB. - -Case 1: LB used in front of a cluster of VNFCs to distribute the traffic flow. - -In such case, the LB is deployed in front of a cluster of multiple VNFCs. Such -cluster can be managed by a seperate cluster manager, or can be managed just -by the LB, which uses heartbeat to monitor each VNFC. When one of VNFCs fails, -the cluster manager should recover the failed one, and should also exclude the -failed VNFC from the cluster so that the LB will re-route the traffic to -to the other VNFCs. In the case when the LB is acting as the cluster manager, it is -the LB's responsibility to inform the VNFM to recover the failed VNFC if possible. - - -Case 2: LB used in front of a cluster of VMs to distribute traffic flow. - -In this case, there exists a cluster manager(e.g. Pacemaker) to monitor and manage -the VMs in the cluster. The LB sits in front of the VM cluster so as to distribute -the traffic. When one of the VM fails, the cluster manager will detect that and will -be in charge of the recovery. The cluster manager will also exclude the failed VM -out of the cluster, so that the LB won't route traffic to the failed one. - -In both two cases, the HA of the LB should also be considered. - -..[MT] I think this use case needs to show also how the LB learns about the new VNFC. -Also we should distinguish VNFC and VM failures as VNFC failure wouldn't be detected -in the NFVI e.g. LB, so we need a resolution, an applicability comment at least. -..[fq] I think I have made a mistake here by saying the VNFC. Actually if the failure -only happens in VNFC, the VNFC should reboot itself rather than have a new VNFC taking -its place. So in this case, I think I should modify VNFC into VMs. And as you mentioned, -the NFVI level can hardly detect VNFC level failure. - -..[MT] There could also be a combined case for the N+M redundancy, when there are N -actives but also M standbys at the VNF level. -..[fq] It could be. But I actually haven't see such a deployed case. So I am not sure -if I can discribe the schemes correctly:) - -3.2. Intra-VNF Communication - -For stateful VNFs, data synchronization is necessary between the active and standby VMs. -The HA manager is responsible for handling VNFC failover, and do the assignment of the -active/standby states between the VNFCs of the VNF. Data synchronization can be handled -either by the HA manager or by the VNFC itself. - -The state synchronization can happen as - -- direct communication between the active and the standby VNFCs - -- based on the information received from the HA manager on channel or messages using a common queue, - -..[MT] I don't understand the yellow inserted text -..[fq] Neither do I, actually. I think it is added by some one else and I can't make -out what it means as well:) - -- it could be through a shared storage assigned to the whole VNF - -- through in-memory database (checkpointing), when the database (checkpoint service) takes care of the data replication. |