Spare Capacity Dimensioning for different ReRouting Strategies in Transport Networks Bandwidth variable transponders (BVTs) have the capability to adjust the linerates of lightpaths in optical transport networks. This feature is relevant for the restoration of IP over optical networks where the capacity of the IP links is provisioned by lightpaths. When a fibre cut occurs, the affected IP links are restored by rerouting the disrupted lightpaths over usually longer protection paths. In most cases, to adapt to the physical limitations of these paths, the BVTs that implement the affected lightpaths have to reduce their linerates. This results in IP links with reduced capacities which may cause congestion in the IP layer. Today, due to the lack of information exchange between the IP and the optical control planes, the IP layer is not aware of the capacity reduction and cannot trigger automatic traffic rerouting so as to avoid congestion. Therefore, the policy applied today is to shutoff all IP links affected by a linerate reduction. In this paper we study alternatives to this policy by investigating rerouting strategies in the IP layer that avoid shuttingoff all IP links affected. The assumption is made that in future a software defined network (SDN) control plane enables coordination between the IP and optical layers. The efficiency of the strategies is assessed by calculating their spare capacity requirements, i.e. the extra capacity required in the optical layer to carry the IP traffic in case of single link fibre cuts. In our case study we consider a network scenario from Deutsche Telekom. The results show that the rerouting strategies lead to significant capacity savings compared to the traditional shutoff approach.

Reduction of Delay Overfulfillment in IPoverDWDM Transport Networks The traffic in todayxe2x80x99s transport networks is increasing dramatically due to more demanding applications like video on demand and improving access technologies like 5G. Additionally, the quality of service requirements are becoming more stringent while network operators are seeking new ways for revenue creation. We propose a multilayer network reconfiguration approach that reduces the overfulfillment of service delay requirements. In that way it provides an incentive to customers with lowdelay services to acquire a more expensive service class for their traffic. Additionally, it relieves highly utilized links for services with very strict delay requirements. We provide an ILP formulation that solves this multilayer network problem by performing a crosslayer optimization. Further, we evaluate our approach for two nationwide backbone networks. We show that a reduction of service delay overfulfillment is possible and how that affects other network metrics.