An experimental study on the effects of outdated control information in GMPLS-controlled WSON for Shared Path Protection

In Shared Path Protection, backup resources can be shared by multiple backup lightpaths as long as their respective working lightpaths are not affected by the same (single) failure event. This property is known as backup sharing among existing backup paths. The goal of this work is to experimentally evaluate the impact of the traffic dynamics when the control information on resource sharing is either flooded by OSPF-TE or collected by RSVP-TE. In this paper we consider three information dissemination strategies by the OSPF-TE routing protocol, comparing them when collecting shareable resource information by means of the standard or extended RSVP-TE signalling protocol. The three OSPF-TE dissemination approaches differ on the granularity of the disseminated TE link information. We study the trade-offs between the blocking probability, the resource overbuild, the RSVP-TE and OSPF-TE bandwidth, the mean connection setup delay and the routing convergence time as key indicator for measuring outdated information. From the experimental evaluation, it can be observed that RSVP-TE resource information collection strategies are less sensitive to the concurrence of multiple connection requests, since it collects the wavelength availability and sharing information hop-by-hop, much faster than OSPF-TE resource information dissemination strategies. Therefore, the best SPP recovery strategy for the considered traffic dynamics, in terms of blocking probability and resource overbuild, is to compute, at the source node, an spatial path using as input information the availability and shareability of the network resources on a per-wavelength channel basis gathered in the node's TED repository by the extended OSPF-TE routing protocol, and to perform the wavelength assignment at the destination node taking advantage of the collection of the shareable resource information attained by the extended RSVP-TE signalling protocol. However, a clear tradeoff is stated between network performance and the generated control bandwidth.