Overview

In access network, an ONU may serve one or more subscribers and can have one or more queues assigned to each subscriber. Different queues belonging to one subscriber can be used, for example, to serve different classes of traffic (i.e., voice, video, and data) with different quality-of-service (QoS) guarantees. To satisfy the network requirements, a remote scheduler should meet the following objectives:

Scalability. The algorithm should support a large number of queues (several hundreds to several thousands). The algorithm should be efficient and scalable with the number of queues; i.e., overhead should not grow significantly with the number of queues served.

Guarantees. Unlike enterprise LANs, access networks serve noncooperative users; users pay for service and expect to receive their service regardless of the network state or the concurrent activities of other users. Therefore, the network operator must be able to guarantee a minimum bandwidth to each queue i, assuming, of course, that the queue has enough data to send. Different services (queues) require different parameters. For example, voice service requires a delay bound of 1.5 ms [G.114], but needs only fixed and small bandwidth. Video traffic requires variable bandwidth, but can tolerate larger delay.

Fairness. To achieve multiplexing gain in EPON, excess bandwidth left by idle queues is redistributed among backlogged queues. The excess bandwidth B ^ex should be allocated to backlogged queues in a fair and predictable manner, for example, in proportion to weights

? assigned to each queue .