The service or subscriber or multiservice site scheduler to port scheduler association model allows for multiple services or subscribers or multiservice sites to have independent scheduler policy definitions while the independent schedulers receive bandwidth from the scheduler at the port level. By using two-scheduler policies, available egress port bandwidth can be allocated fairly or unfairly depending on the needed behavior. Figure: Two-scheduler policy model for access ports shows this model.
When a two-scheduler policy model is defined, the bandwidth distribution hierarchy allocates the available port bandwidth to the port schedulers based on priority, weights, and rate limits. The service or subscriber or multiservice site level schedulers and the policers and queues they service become an extension of this hierarchy.
Because of the nature of the two-scheduler policy, bandwidth is allocated on a per-service or per-subscriber or multiservice site basis as opposed to a per-class basis. A common use of the two-policy model is for a carrier-of-carriers mode of business. with the goal of a carrier to provide segments of bandwidth to providers who purchase that bandwidth as services. While the carrier does not care about the interior services of the provider, it does care how congestion affects the bandwidth allocation to each provider’s service. As an added benefit, the two-policy approach provides the carrier with the ability to preferentially allocate bandwidth within a service or subscriber or multiservice site context through the service or subscriber or multiservice site level policy, without affecting the overall bandwidth allocation to each service or subscriber or multiservice site. Figure: Schedulers on SAP or multiservice site receive bandwidth from port priority levels shows a per-service bandwidth allocation using the two-scheduler policy model. While the figure shows services grouped by scheduling priority, it is expected that many service models place the services in a common port priority and use weights to provide a weighted distribution between the service instances. Higher weights provide for relatively higher amounts of bandwidth.
