MetaRing Fairness Control Schemes in All-Optical WDM Rings

W D M rings are receiving significant attention in the field of all-optical networks because their implementation appears to be feasible with state-of-the-art components. Several MAC protocols were recently proposed in order to resolve contentions among nodes sharing the available wavelengths an W D M rings. These MAC protocols achieve high e&ciency but unsatisfactory fairness, due to the asymmetric position of sources with respect t o destinations. Thus, i n order to improve fairness, it is necessary to adopt a fairness control scheme. In this paper we discuss the adaptation of the MetaRing fairness control scheme to the context of WDM multi-channel rings. Several alternatives are considered and compared via simulation. 1 Introduction We consider all-optical multi-channel networks with ring topology, the channel multiplicity being achieved by using WDM (wavelength division multiplexing) [l]. Space diversity can be further exploited to reduce the number of wavelengths that must be accommodated in one single fiber, but we do not consider this issue here. Each channel (Le., each wavelength) is used to transfer packets to a subset of network destinations; different transmissions are time-multiplexed via a slotted MAC (medium access control protocol. Since WDM channels are used as group destination addresses, nodes fixed receiver. We focus on networks with ring topology since they are considered an attractive solution for all-optical networks mainly thanks to the recent availability of optical amplifiers to compensate for insertion losses at intermediate nodes. An important feature of rings is to allow for an easier synchronization, thus permitting the adoption of slotted MAC protocols even at extremely high data rates. The main advantage of slotted MAC protocols is that they allow collision-free access to the available wavelengths with limited complexity ; their main drawback is in the possible unfair sharing of the resources among users. This paper considers fairness control techniques to be integrated within a slotted MAC protocol for all-optical WDM rings named SRR (Synchronous Round Robin), which was proposed and studied by the au-are equipped wit (h i one tunable transmitter and one Toniolo was supported by a grant from CSELT. thors in previous papers [2, 31. The proposed fairness control approaches are derived from those originally designed for the MetaRing MAN [4]. 2 WDM Rings We consider all-optical WDM rin s with M nodes and W wavelengths (with W 5 M j. Each node is equipped with one tunable transmitter and one fixed receiver; when a …