Impact of protection schemes and network component’s availability on operational expenditures Carmen Mas Machuca, 1, * Oyvind Moe, 1 and Monika Jäger 2 1 Munich University of Technology (TUM), Arcistrasse 21, 80333 Munich, Germany 2 T-Systems Enterprise Services GmbH, Goslarer Ufer 35, 10589 Berlin, Germany * Corresponding author: cmas@tum.de Received November 2, 2007; revised December 7, 2007; accepted December 10, 2007; published January 15, 2008 Doc. ID 89268 The high capacity of communication networks nowadays has encouraged the study of the high impact that failures have on the data transmission and the service quality. This impact is usually evaluated as the quantity of affected data as well as the duration of the failure. However, the impact also has eco- nomic consequences such as the cost of the personnel required to repair the failures, the cost of the personnel to restore the services, penalties through possible service level agreement violations, etc. We evaluate the impact of the protection schemes and the network component’s availability on the opera- tional cost. © 2008 Optical Society of America OCIS codes: 000.1200, 060.0060. 1. Introduction Network reliability of optical networks has been a major issue for network operators due to the huge quantity of data that may be lost when a single failure occurs. How- ever, the impact that a failure has on the operational cost has been mostly disre- garded. Nowadays, the continuous and rapid network evolution combined with the existence of new operators making the market more agressive and competitive have forced network manufacturers and operators to keep a close eye on the costs. The objective is to minimize the total cost of ownership (TCO) so that the manufacturers can better sell their new products and network operators have larger margins to offer services with more competitive prices. The TCO has two main factors: capital expenditures (CAPEX) and operational expenditures (OPEX). Although the processes that are included in each factor have not been standardized, the most accepted definition is that CAPEX copes with the expenses related to the network infrastructure (fiber, nodes, interfaces, required floor space, etc.), while OPEX includes the cost factors of the network operation such as power, personnel involved in the network operation, and the maintenance of running services, testing equipment to detect failures, etc. The first technoeconomic studies focused on CAPEX, which are easier to evaluate. However, it has been shown recently that OPEX is a very important factor of TCO, even up to 85% [1,2], which indicates that OPEX should not be disregarded. OPEX can be divided in two groups of costs [3]: (i) network related costs and (ii) ser- vice related costs. The former includes the costs related to the operation of the net- work such as the reparation of failures, maintenance of the equipment, etc., while the latter comprises the costs associated with the operation of the services such as the establishment and the release of services, the surveillance of the service quality, etc. The impact the network reliability has on OPEX is mostly related to two processes: the failure reparation process, which is a network related cost, and the service resto- ration process, which is a service related cost. In other words, when a failure occurs and at least one service is disrupted, two processes are triggered: the service restora- tion process aiming at restoring the service depending on the protection scheme agreed at the service level agreement (SLA) (called as many times as services are dis- rupted) and the failure reparation process aiming at locating and repairing the failed network component. This paper aspires to evaluate the impact that different protec- tion schemes and the network component availability have on the operation costs. Vol. 7, No. 2 / February 2008 / JOURNAL OF OPTICAL NETWORKING 142 1536-5379/08/020142-9/$15.00 © 2008 Optical Society of America