Capacity-cost based load balancing allows a cost to be assigned to diverted AA subscribers (by the app-profile). Load Balancing uses the total allocated costs on a per-ISA basis to assign the subscriber to the lowest sum cost ISA resource. Each ISA supports a threshold as the summed cost value that notifies the operator if or when capacity planning has been exceeded.
The load balancing decision is made based on the AA capacity cost of an AA subscriber. The capacity cost is configured against the app-profile. When assigning a new diverted AA subscriber to an ISA, the ISA with the lowest summed cost (that also has sufficient resources) is chosen. Examples of different load-balancing approaches that may be implemented using this flexible model include:
AA subscriber count balancing
Configure the capacity cost for each app-profile to the same number (for example, 1).
AA subscriber stats resource balancing
Configure the capacity cost to the number of stats collected for AA subscribers using the app-profile. This may be used if different partitions have significantly different stats requirements.
bandwidth balancing
Configure the capacity cost to the total bandwidth in both directions (in kb/s) expected for those AA subscribers. This may be used if different AA subscribers have highly varying bandwidth needs.
Load balancing operates across ISAs with in an AA group, and does not balance across groups. The system ensures that app-profiles assigned to AA subscribers (ESM subscribers, SAPs and spoke SDPs) that are within a single VPLS/Epipe/IES/VPRN service are all part of the same AA group (partitions within an AA group are not checked or relevant).
Users can replace the app-profile assigned to an AA subscriber with another app-profile (from the same group/partition) that has a different capacity cost.
Regardless of the preferred choice of ISA, the system takes into account the following:
Resource counts have per-ISA limits. If exceeded on the ISA of choice, that ISA cannot be used and the next best is chosen.
Divert IOM service queuing resources may limit load-balancing. If queuing resources are exhausted, the system attempts to assign the AA subscriber to the ISA where the first AA subscriber within that service (VPLS/Epipe) or service type (IES/VPRN) was allocated.
For prefix transit AA subscriber deployments using the remote-site command, traffic for the remote transit subs are processed a second time. The ISA used by the parent AA subscriber is used by all transits within the parent. In remote-site cases there may be a need to increase capacity cost of parent because the transits stay on same ISA as the parent.
Prefix transit AA subscribers are all diverted to the same Group and partition as the parent SAP.