A high-performance message prioritization and scheduling protocol for WDM star networks

Abstract

A high-performance Efficient Message Prioritization and Scheduling (EMPS) protocol, for intelligent message scheduling in Wavelength-Division Multiplexing (WDM) star networks is introduced. The performance of the well-known EATS and MSL schemes is noticeably degraded in practical networks with non-uniform destinations and non-negligible transceiver tuning latencies. Under these realistic conditions, it is common that two or more messages with the same destination have to be scheduled consecutively or at close times. In most cases, this brings about some performance penalty, owing to the delayed availability of the destination's receiver for the second (and beyond) of the consecutive messages. As the frequency of such occurrences increases, the performance degradation of the existing schemes becomes more prominent. EMPS is proposed to deal with this problem. It simultaneously considers multiple messages from different transmitting nodes and gives priority to messages intended for the least used destinations each time. By balancing the offered load in this way, EMPS minimizes the probability of having to schedule two or more messages with the same destination consecutively or at close times. Additionally, by incorporating the Minimum Scheduling Latency algorithm for channel selection, the protocol also minimizes the actual performance penalty incurred, when scheduling of consecutive messages with the same destination cannot be avoided. Extensive simulations are carried out in order to study the performance of EMPS and compare it to other efficient schemes under various conditions. The simulation results show that the proposed protocol always brings about a significant performance improvement.

An Intelligent Global Message Prioritization Algorithm for High-Performance Scheduling in WDM Star Networks

“…In fact, just like EMPS, the proposed MinPSL scheme has the extra flexibility to allow its scheduling algorithm to be invoked generally after every F ≥ (N × T cp ) slots, where F is the time interval between the transmission of successive control frames on λ 0 and T cp is the length of one control packet. The value of F is left as a system design parameter and is discussed in [11].…”

“…Since both the control information and the data structures are the same each time the distributed scheduling algorithm is executed, all nodes always produce identical schedules. One principal novelty of MinPSL is that it incorporates more global prioritization of messages than most other schemes with similar network model (such as [5,11]), by allowing each control packet contain information for more than just one message. Specifically, let us denote the number of messages for which each control packet contains information by Q d .…”

“…It has been observed that two highly regarded distributed scheduling schemes, EATS [4] and MSL [2], do not perform very well under these realistic conditions. In our recent study [11] we showed that the EMPS protocol improves the performance of EATS and MSL, by prioritizing messages in the heads of the queues maintained by source nodes on the basis of destination availability. The prioritization made by EMPS, however, is not insightful enough to prevent the incurrence of considerable performance penalties, especially when the offered loads are medium to high and the transceivers of nodes are rather slowly tunable.…”

“…These are extensively described in [11], as they also apply for EMPS; thus, they are not repeated here.…”

Designs of high-performance multicast scheduling mechanisms in WDM networks

“…To satisfy the huge bandwidth requirements for such application, the wavelength division multiplexing (WDM) optical fiber technique offers a feasible solution. Thus, the passive star coupler (PSC)-based WDM optical network architecture, due to its simplicity, has attracted great attentions [1][2][3][4][5][6][7] in local area network environments. In such a network, each network node is equipped with one or more fixed-tuned or tunable transmitters/receivers to transmit/receive packets on wavelength channels, using the intrinsic broadcast-and-select feature of the star network.…”