A Survey on OFDM-Based Elastic Core Optical Networking <s> 5) Optical Network Virtualization <s> A virtualized optical network is proposed as a key to implementing increased agility and flexibility into a cloud computing environment by providing any-to-any connectivity with the appropriate optical bandwidth at the appropriate time. <s> BIB001 </s> A Survey on OFDM-Based Elastic Core Optical Networking <s> 5) Optical Network Virtualization <s> Motivated by the design goals of Global Environment for Network Innovation (GENI), we consider how to support the slicing of link bandwidth resources as well as the virtualization of optical access networks and optical backbone mesh networks. Specifically, in this paper, we study a novel programmable mechanism called optical orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) for link virtualization. Unlike conventional time division multiplexing (TDM)/time division multiple access (TDMA) and wavelength division multiplexing (WDM)/wavelength division multiple access (WDMA) methods, optical OFDM/OFDMA utilizes advanced digital signal processing (DSP), parallel signal detection (PSD), and flexible resource management schemes for subwavelength level multiplexing and grooming. Simulations as well as experiments are conducted to demonstrate performance improvements and system benefits including cost-reduction and service transparency. <s> BIB002 </s> A Survey on OFDM-Based Elastic Core Optical Networking <s> 5) Optical Network Virtualization <s> A new programmable router interface with adaptive packet over optical OFDMA transmission is proposed, providing a perfect mechanism of bandwidth partition for link virtualization. A comparison study is presented to demonstrate its advantages. <s> BIB003 </s> A Survey on OFDM-Based Elastic Core Optical Networking <s> 5) Optical Network Virtualization <s> A new networking approach based on IP/optical OFDM technologies is proposed, providing an adaptive mechanism of bandwidth provisioning and pipe resizing for dynamic traffic flows. A comparison study is presented to demonstrate its advantages. <s> BIB004
For typical applications of network virtualization such as cloud computing and data center interconnections, it is expected that the underlying network provides dynamic and bandwidth-variable connections between geographicallydistributed locations BIB001 . Moreover, for IP-over-optical network configurations, traffic loads may change frequently over time, making it desirable to adapt the virtual topology and virtual link capacity provided by the optical network accordingly BIB004 . Although current optical networks provide transparency and dynamic wavelength switching, they cannot meet the needs of network virtualization because of their rigid and large bandwidth granularity. OFDM-based elastic optical architecture has great potential to realize optical network virtualization through dynamic bandwidth provisioning with its flexible granularity and bandwidth-tunable capability. A high-level architecture of a virtualized optical network (VON) was proposed in BIB001 . The concept of VON is to provide more agility and flexibility to cloud computing environments by adopting the elastic optical path based on O-OFDM technologies and automatically providing any-to-any connectivity with the appropriate optical bandwidth. A programmable and adaptive IP/optical OFDM network architecture was proposed in BIB002 BIB004 . In this architecture, virtual links are established between router pairs, and are isolated from each other by using different OFDM subcarriers on each physical link. A router interface design using OFDMbased link virtualization techniques is presented in BIB003 , where each router interface contains multiple virtual interfaces that correspond to virtual OFDM links (e.g., M subsets of subcarriers), and the virtual interfaces maintain separate FIFO buffers for each virtual link to store packets. The bandwidth of these virtual links can be changed adaptively by adjusting the modulation format or the number of subcarriers, according to traffic-flow variations. Adjustment decisions are based on periodic traffic measurements of the virtual links by backbone routers. Subcarrier resource assignment for such an IP/optical OFDM network was proposed in BIB002 BIB004 . Performance comparisons show that a saving of up to 30% of receivers can be achieved by the adaptive IP/optical OFDM network in comparison to an IP-over-TDM/WDM network BIB002 .