Rate-limiting for Supporting the Fairness of Downstream in Ethernet-PON

C.K. Cho, H.K. Park, K.H. Ahn, Y.-C. Kim, and Y.C. Kim (Korea)


Ethernet-PON, optical access networks, rate limit, downstream, flow control, fairness


Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines between OLT and ONUs. Earlier efforts on Ethernet-PON have been concentrated on an upstream MAC protocol to avoid collision. But it is needed to control downstream traffic in practical access network, where the network provider limits available bandwidth according to the number of users. In this paper, we propose the rate-limiting algorithm to control the downstream bandwidth. The objective of this algorithm is to guarantee the fairness of ONUs while maintaining good performance. In order to do this, we define the service probability that considers the past traffic information for downstream, the number of tokens and the relative size of negotiated bandwidth. We develop the simulation model for Ethernet-PON to evaluate the rate-limiting algorithm by using AWESIM. Some results are shown in terms of defined fairness factor, delay and dropping rate.

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