Distributed Dijkstra sparse placement routing algorithm for translucent optical networks

Abstract

In this paper we study translucent optical networks as an alternative to fully transparent and fully opaque optical networks. In the former networks, a technique called sparse placement is used to overcome the lightpath blocking caused by the signal quality degradation, using much less regenerators, which must strategically be placed, in contrast to a fully opaque network. In this paper we propose a sparse placement algorithm based on two requirements. The first one is signal regeneration necessary to re-amplify, reshape, and retime the optical signals after some predefined transparent distance in order to successfully receive the signals at the destination node. The other is load balance of the traffic in the network aimed at efficient usage of the network capacity resources. We apply a distributed Dijkstra routing algorithm which dynamically changes weights of links during the process of locating regeneration capable nodes. We compare the performance of the proposed algorithm with commonly used sparse placement algorithms through simulation experiments. The benefits are such that load balancing of the network traffic is fully utilized, and with technological development it will be sufficient to equip up to 30% of nodes in the network with electronic regenerations in order to have the same performance as in an opaque network.

Multihop Routing and Wavelength Assignment Algorithm for Optical WDM Networks

“…Th is results from the search for alternate paths, and if there are no free resources in that case, the sessions are mult iplexed. The proposed algorith m has much greater results in regard with the quality of service compared with the algorith m in [16] because none of the requested sessions are not blocked. But on the other side some of the sessions must have reduced bit rate due to the mu ltip lexed traffic.…”

“…The selection of nodes which will be capable of performing O/E/ O conversion is made based on the following two criteria: destination signal quality and uniform traffic distribution across the network. The obtained result is a translucent optical network [16].…”

“…The RWA algorith ms and simulation processes are applied in this paper on the following two broadly used topologies of the optical networks [4,5,16] Each network node consists of an optical core (optical crossconnect -OXC) and an access station. An OXC consists of mult iplexers, optical switches, input/output amp lifiers, taps and demultip lexers.…”

“…As we have previously emphasized, the longer an optical signal travels over a transparent path (path without opaque nodes) and the more switching nodes the signal passes through, the higher the signal quality degradation is. Therefore, in the paper [6,16] it is proposed to use two parameters described as follows: Lhop is the acceptable maximu m t ransparent path length (there are no opaque or regeneration nodes on the route) measured in hops (the number of intermed iate nodes passed through) and Llen is the acceptable maximu m geographical transparent length of the optical signal in kilo meters. If the length of the route is larger than the length Llen or the service signal travels mo re hops than Lhop, the end receiver will not detect the service signal.…”

“…the transparent path should not be longer than Llen in kilo meters. Distributed Dijkstra algorith m provides an optical network with the necessary number of nodes capable of performing O/ E/ O conversion, with routes between any two nodes [16]. For the first pair in the sequence of priority nodes, the chosen route is observed and every link of the chosen route is searched for the same available wavelength.…”