Overview

According to the IEEE 802.3ah standard, the size and periodicity of the discovery windows are left to implementation. A simple implementation may settle on periodic discovery windows of fixed size, as was the case with examples considered in Chap. 12. But more sophisticated schemes can also be considered. For example, since the normal traffic is suspended during the discovery, one may desire to minimize the impact on the traffic. Such a scheme would require each individual discovery window to be as small as possible, probably at the expense of having a large number of collisions and repeating attempts. Alternatively, the goal of optimization may be to reduce the overall channel unavailability time due to the discovery process. Such a scheme would try to minimize the combined size of all discovery windows, while not being particularly concerned with the size of each individual window.

Below we consider a method to adjust the discovery slot size in order to minimize the overall channel unavailability. The basic premise of this method is the assumption that the OLT can always estimate the maximum number of ONUs still requiring registration. Indeed, it is typically known to a network operator how many ONUs are provisioned on each PON. Also, at any time, it is known how many ONUs are registered. The difference between the two is the number of ONUs that may attempt initialization at the next discovery opportunity. (We say may because, some ONUs may be turned off or disconnected.) The OLT may...