Elastic traffic effects on WDM dynamic grooming algorithms

Dynamic grooming in IP over WDM networks: a study with realistic traffic based on GANCLES simulation package

“…As a general rule IP does not implement CAC functions and the congestion control is done reactively by TCP. As we discussed in [13] the elastic nature of present-day data applications cannot be disregarded if dynamic grooming is considered, because the feedback introduced by the closed-loop nature of TCP (and traffic aggregation does not destroy the feedback) has an enormous impact on the overall performance. We introduce two different models of elastic traffic.…”

“…Note that in all these cases if the source-destination pair is disconnected on the logical topology and no new lightpath can be installed between them, the incoming connection request must be refused even if it is elastic. This phenomenon is particularly evident at low/medium loads with grooming algorithms using aggressively the optical resources, as it was shown in [13]. Such unacceptable situations could be avoided by including a pre-defined spanning tree or any other basic logical topology to ensure the connectivity in the data-layer, a feature GANCLES is provided with, defining different pre-defined logical topologies (see [16]).…”

“…6. We concentrate on the impact of IP flow requests granularity and the threshold C 3 on the grooming algorithms performance, referring the reader to [13] for additional results on this topology. We first investigate the performance of VirtFirst and OptFirst as a function of the data-layer requests granularity.…”

“…More traditional studies such as [5], [10], [11], [12] are based on the simplifying assumption that the traffic is static and "circuit-like." In a previous contribution [13] we discussed in detail the impact of realistic traffic models on dynamic grooming, showing the inherent interaction between the IP and the optical layer and its effect on the overall performance of the network. Traffic flows in this models share the resources on a virtual topology path following the max-min fairness criterion [14], thus mimicking the ideal behavior of a bundle of TCP connections.…”