Content Distribution in Elastic Optical Networks with Dedicated Path Protection Krzysztof Walkowiak, Róża Goścień, Wojciech Kmiecik Department of Systems and Computer Networks Wroclaw University of Technology, Poland Krzysztof.walkowiak@pwr.wroc.pl Mirosław Klinkowski National Institute of Telecommunications Warsaw, Poland M.Klinkowski@itl.waw.pl Abstract— Recently, the Content Oriented Networking (CON) has become a recognized approach that is gaining extensive acceptance and deployment. At the same time, Elastic Optical Networks (EONs) are considered as a very promising approach for effective bandwidth allocation in optical networks. In this paper, we consider various approaches to content distribution in EON protected by the Dedicated Path Protection (DPP) scheme. We evaluate impact of these approaches on the performance of survivable EON with respect to CAPEX cost, power consumption and spectrum usage. We run numerical experiments on two representative network topologies with traffic patterns based on the Cisco predictions. The results show that the additional overhead of using the DPP protection in the EON for the analyzed performance metrics is from 2.1 to 3.5, depending on the metric and considered content delivery scenario. Moreover, the obtained results prove that the content delivery scenario has a large impact on the performance of the EON used in the physical layer and its suitable choice can bring up to 50% savings in all considered metrics. Keywords— elastic optical network, dedicated path protection, content delivery network, optimization I. INTRODUCTION Recently, we observe unprecedented increase of a popularity of wide range of services and applications based on a widespread content requested by many users, such as video on demand or high definition TV. According to “Cisco Visual Networking Index (VNI)”, Content Delivery Networks (CDNs) will carry about 40% of the global IP traffic and half of the Internet traffic in 2017. Moreover, they suppose that the CDN traffic will grow at a compound annual growth rate (CAGR) of 34% from 2012 to 2017. Therefore, the idea of the Content-Oriented Networking gains more focus in last few years [1], [2]. The growing popularity of various types of multimedia content in the Internet, triggers the need to provide an effective and scalable optical technology that can answer the growing traffic volumes. Nowadays, the majority of backbone networks rely on the optical networks that implement Wavelength Division Multiplexing (WDM). However, this technology is not efficient enough for future networks and increasing traffic requirements. It is suspected, that the future of optical backbone networks is the idea of Elastic Optical Networks (EONs) [3]. Moreover, nowadays most of customers expect reliable and uninterrupted network services. Since optical backbone networks carry traffic with bitrates reaching hundreds of Gb/s, a network failure – even a short one – can cause many severe consequences. Thus, the survivability aspects are very important when designing or optimizing backbone network topology and infrastructure. The main contribution of this work is the evaluation of various approaches to content distribution in survivable elastic optical networks with respect to different network performance metrics: CAPEX cost, power consumption, and spectrum usage. The survivability requirements are fulfilled by the dedicated path protection (DPP) scheme, that protects against a single link failure. What is more, the considered protection scheme (DPP) is evaluated with respect to two different channel assignment policies – same channel and different channel approach. The remainder of the paper is organized as follows. The next Section is a brief description of elastic optical networks and protection methods dedicated for this technology. Section III describes content distribution with special focus on the considered content distribution approaches. Section IV presents our simulation setup, wherein the Section V reports numerical results. The last section VI concludes the whole work. II. SURVIVABILITY OF ELASTIC OPTICAL NETWORKS A. Elastic Optical Networks Elastic Optical Networks (EONs) are considered as a very promising approach for future optical networks, as a successor of currently used Wavelength Switched Optical Networks (WSONs). The main novelty of EONs compared to WSONs is provisioning of sub-wavelength granularity for low-rate transmission and super-channel connectivity for accommodating ultra-high capacity client signals within a common network. The architectures of EON are based on three basic elements: flexible frequency grids, bandwidth-variable transponders (BV-T), and bandwidth variable wavelength cross-connects (BV-WXCs). The first required element is flexible frequency grids. The ITU-T has recently included the definition of a flexible WDM grid in the recommendation [4]. The second element (BV-T) adapts the client data signal to be