Enforcing bandwidth allocation and traffic conformance in Passive Optical Networks

Broadband Passive Optical Network (PON) technology is a promising approach to establish a cost-effective access network. It is intended to provide a simple, low cost, scalable solution capable of delivering broadband access to end users, by passively sharing a single optical fibre transmission system between several customers. While downstream traffic is broadcasted to all customers, the access of upstream traffic to the fibre has to be arbitrated in order to avoid collisions. This arbitration mechanism and more generally, bandwidth distribution and QoS Provisioning, have been left to the implementer. An ideal Dynamic Bandwidth Allocation (DBA) should support both Committed Bandwidth and Best Effort services, with good control of the usual QoS characteristics (delay, jitter, loss) while utilizing the available bandwidth with good efficiency. It should also provide some isolation between end-users in order to offer a fair access to resources to all users. In this paper, we assume that each user negotiates classical traffic profiles for its upstream Committed Bandwidth traffic. We show that a DBA that does not take into account traffic conformance cannot isolate compliant users from non-compliant users, leading to QoS degradations of the upstream traffic for compliant users. We then propose a framework for taking into account the traffic conformance within the DBA used to arbitrate between users' demands. This study is illustrated on a priority based DBA designed for Ethernet Optical Networks (EPONs)