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Quantum key distribution (QKD) is an essential branch of quantum communications that facilitates future-proof security. In the near future, large-scale quantum networks will inevitably encounter diverse QKD protocols, ultimately resulting in a multi-protocol quantum network. Motivated by the evolution of advanced QKD protocols, this article introduces a pivotal enabler for multi-protocol quantum networks: software-defined heterogeneous QKD chaining (HQKDC). In contrast to the conventional QKD chain using a single protocol and a single connectivity pattern, a heterogeneous QKD chain is established relying on multiple protocols and diverse connectivity patterns. We elaborate the HQKDC framework by describing the structures of various QKD chains and proposing an architecture of software-defined HQKDC over optical networks. The software defined networking paradigm and optical networks can facilitate the orchestration and deployment of heterogeneous QKD chains, respectively. Furthermore, we present and evaluate the strategies for heterogeneous QKD chain deployment, as well as devise and demonstrate the workflow for heterogeneous QKD chain orchestration. Finally, we discuss open issues toward the practical QKD network and quantum Internet. [ABSTRACT FROM AUTHOR]

In the Internet Age, optical networks are vulnerable to numerous cyberattacks, and conventional key distribution methods suffer from the increased computational power. QKD can distribute information-theoretically secure secret keys between two parties based on the principles of quantum mechanics. Integrating QKD into optical networks can leverage existing fiber infrastructures with wavelength division multiplexing for the practical deployment of secret keys, and accordingly employ the secret keys for optical-layer security enhancement. Then, how to efficiently deploy and employ secret keys over QKD-integrated optical networks are emerging as two challenges. This article proposes a framework of key as a service (KaaS, i.e., providing secret keys as a service in a timely and accurate manner to satisfy the security requirements) to jointly overcome these two challenges. To enable the typical functions (i.e., secret-key deployment and employment) in KaaS, two secret-key virtualization steps, that is, key pool (KP) assembly and virtual key pool (VKP) assembly, are introduced. Also, we illustrate a new QKD-integrated optical network architecture from a holistic view, where the control layer is implemented by software defined networking for efficient network management. A time-shared KP assembly strategy and an on-demand VKP assembly strategy are presented for KaaS implementation. The success probabilities of KP assembly and VKP assembly are defined to evaluate the benefits of KaaS for efficiently deploying and employing secret keys as well as for security enhancement over QKD-integrated optical networks. [ABSTRACT FROM AUTHOR]

Optical network security is attracting increasing research attention, as loss of confidentiality of data transferred through an optical network could impact a huge number of users and services. Data encryption is an effective way to enhance optical network security. In particular, QKD is being investigated as a secure mechanism to provide keys for data encryption at the endpoints of an optical network. In a QKD-enabled optical network, apart from TDChs, two additional channels, called QSChs and PIChs, are required to support secure key synchronization. How to allocate network resources to QSChs, PIChs, and TDChs is emerging as a novel problem for the design of a security-guaranteed optical network. This article addresses the resource allocation problem in optical networks secured by QKD. We first discuss a possible architecture for a QKD-enabled optical network, where an SDN controller is in charge of allocating the three types of channels (TDCh, QSCh, and PICh) over different wavelengths exploiting WDM. To save wavelength resources, we propose to adopt OTDM to allocate multiple QSChs and PIChs over the same wavelength. An RWTA algorithm is designed to allocate wavelength and time slot resources for the three types of channels. Different security levels are included in the RWTA algorithm by considering different key updating periods (i.e., the period after which the secure key between two endpoints has to be updated). Illustrative simulation results show the effects of different security-level configuration schemes on resource allocation. [ABSTRACT FROM AUTHOR]

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Ubiquitous data center optical interconnection is a promising scenario to meet the high burstiness and high-bandwidth requirements of services in terms of the user-access-oriented interconnection between user and data center, inter-data- center, and intra-data-center interconnection. However, in the current mode of operation, the control of the data center and optical network is separately deployed. Enabling even limited interworking among these separated control systems does not provide a mechanism to exchange resource information and enhance the high-level performance requirement of applications. Our previous work implemented cross-stratum optimization of optical network and application strata resources inter-data-center, which allows the accommodation of data center services. In view of this, this study extends to the ubiquitous data center optical interconnection scenario. This article presents a novel SUDOI architecture aimed at extensive user access from the perspective of heterogeneous cross-stratum and multi-layer networking modes. SUDOI can enable cross-stratum optimization of application and optical network stratum resources, and enhance multiple- layer resource integration in the ubiquitous data center optical interconnection. The functional modules of SUDOI architecture, including the core elements of various controllers, are described in detail. The cooperation procedure in user-access-oriented interconnection, multiple- layer resource integration inter-data-center, and intra-data-center service modes is investigated. The feasibility and efficiency of the proposed architecture are also experimentally demonstrated on our OaaS testbed with OpenFlow-enabled optical nodes, and compared to the CSO scheme in terms of blocking probability and resource occupation rate. Numerical results are given and analyzed based on the testbed. Some future discussion and exploration issues are presented in the conclusion. [ABSTRACT FROM PUBLISHER]

The evolution toward 5G mobile networks is characterized by supporting higher data rate, excellent end-to-end performance and ubiquitous user-coverage with lower latency, power consumption, and cost. To support this, the RANs are evolving in two important aspects. One aspect is ?cloudification,? which is to pool baseband units to be centralized for statistical multiplexing gain. The other aspect is to use advanced optical technologies for digital and analog signal transmission in a cloud-based RAN. In this article, we focus on BBU cloud interconnection with optical layer technologies. Flexible grid optical networks with the enabling technologies are introduced to provide elastic, transparent, and virtualized optical paths between the BBU pools. To improve the elasticity and intelligence of C-RAN, we propose a software defined centralized control plane to coordinate heterogeneous resources from three domains: the BBU domain, radio domain, and optical domain. We report an experimental demonstration of elastic lightpath provision for cloud radio-over-flexible grid optical networks in a software-defined-networking-based testbed. [ABSTRACT FROM PUBLISHER]

Data center interconnection with elastic optical networks is a promising scenario to meet the high burstiness and high-bandwidth requirements of services. Many data center services require lower delay and higher availability with end-to-end guaranteed QoS, which involves both application and transport network resources. However, in the current mode of operation, the control of elastic optical networks and data centers is separately deployed. Enabling even limited interworking among these separated control systems requires the adoption of complex and inelastic interfaces among the various networks, and this solution is not efficient enough to provide the required QoS. In this article, we present a novel cross stratum optimization (CSO) architecture in elastic data center optical interconnection. The proposed architecture can allow global optimization and control across elastic optical transport network and data center application stratum heterogeneous resources to meet the QoS requirement with the objective of optical as a service (OaaS). The functional modules of CSO architecture, including the core elements of application and transport controllers, are described in detail. The cooperation procedure in CSO-based service provisioning and cross stratum service resilience modes is investigated. The overall feasibility and efficiency of the proposed architecture is also experimentally demonstrated on our OaaS testbed with four OpenFlow-enabled elastic optical nodes, and compared to MFA, ALB, and CSO-DGLB service provisioning schemes in terms of path setup/release/adjustment latency, blocking probability, and resource occupation rate. Numerical results are given and analyzed based on the testbed. Some future discussion and exploration issues are presented in the conclusion. [ABSTRACT FROM PUBLISHER]

Optical WDM backbone networks based on fixed spectrum grid have limitations such as low spectrum utilization and rigidity in provisioning for heterogeneous rates. Flexible-grid technologies can alleviate these limitations for on-demand provisioning. These technologies represent promising candidates for future optical networks supporting beyond-100-Gb/s signals. However, a one-time green-field deployment of flexible-grid technologies may not be practical, as the already-made investment in existing fixed-grid WDM networks needs to be preserved, and interruptions to ongoing services need to be minimized. Therefore, we envision that fixed-and flexible-grid technologies will coexist, which will bring the challenge of interoperating fixed-and flexible-grid equipment. It is also important to design the optimum migration strategy to maximize cost effectiveness and minimize service interruption. In this article, we discuss the key aspects of network architectures supporting coexistence of fixed and flexible grid technologies, and outline the challenges of network operations. We also propose and evaluate different migration strategies from fixed grid to flexible grid under different network scenarios. [ABSTRACT FROM PUBLISHER]

With the development of large-scale multilayer and multidomain optical networks, the path computation process becomes increasingly complicated in consideration of various policies and constraints. In particular, to meet the rigid requirements of multiple layers and multiple domains, dynamic routing has become one of the key issues in GMPLS/ASON networks. In this article, a novel dual routing engine architecture in multilayer and multidomain scalable and constraint-aware policy-enabled optical networks, DREAM, is proposed. This new architecture exploits the advantages of both the GMPLS control plane and path computation element PCE. The cooperation of a group engine and a unit engine effectively optimizes the path computation process, especially under the multiple constraints. In this article, the functional compositions of dual routing engines, core elements of DREAM, are described in detail. Six cooperation modes between group and unit engines are investigated. Two different routing schemes (DRE-FPC and HDRE-BRPC) are proposed and evaluated on a DREAM-based testbed, which is able to support over 1000 nodes divided into 20 or more domains. Numerical results are given and analyzed based on the testbed. Some future discussion and exploration issues are presented in the conclusion. [ABSTRACT FROM PUBLISHER]

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Presents the table of contents for this issue of the publication. [ABSTRACT FROM PUBLISHER]

The traffic carried by core optical networks as well as the per-channel interface rates required by IP routers are growing at a remarkable pace year after year. This trend is due to the widespread deployment of fixed and wireless broadband access networks, the huge growth of video-based services supported by the Internet, and social media applications, as well as a substantially growing amount of machine-to-machine traffic supporting a variety of data-centric applications. Optical transmission and networking advancements have been able to satisfy this huge traffic growth so far by providing the necessary network infrastructure in a cost- and energy-efficient manner, utilizing to the maximum extent the capabilities of optoelectronic and photonic devices across the available bandwidth of deployed optical fibers. However, as we are rapidly approaching fundamental spectral efficiency limits of single-mode fibers, the scientific and industrial telecommunications community foresees that the growth capabilities of conventional WDM networks operating on a fixed frequency grid in conventional wavelength bands are quite limited. [ABSTRACT FROM PUBLISHER]

The table of contents for the February 2015 issue of "IEEE Communications Magazine" is presented.

Presents the table of contents for this issue of the publication. [ABSTRACT FROM AUTHOR]

Presents the table of contents for this issue of the publication. [ABSTRACT FROM AUTHOR]

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The advanced fifth generation (5G) infrastructure is expected to become the ?nervous system? of the digital society, digital economy, and silver economy. New service paradigms such as ?immersive experience? and ?anything as a service? (XaaS) everywhere are envisioned as among the primary drivers for global adoption and market uptake of new 5G technology components. Above all, 5G networks will support mission-critical machine communications and massive machine type of traffic. As a result, the key performance metrics that 5G is expected to improve are in terms of, but not limited to, latency, reliability, capacity, and spectrum and network agility. This calls for a complete rethinking of all functional domains, including access stratum (AS), non-access stratum (NAS), and transport network layer (TNL), in terms of protocols and procedures. New emerging technologies, such as software defined networking (SDN), network functions virtualization (NFV), mobile edge computing (MEC), and high-performance computing (HPC), provide momentum for new design principles toward software (service) defined 5G networks, targeting a software defined air interface (SDAI) for available bands (spectrum); sliced "networks on demand" for multiple industries, especially for vertical markets (new architecture); and flexibility and spectral efficiency for mobile broadband and machine type communications (new air interface). [ABSTRACT FROM PUBLISHER]

In the first quarter of this year, the optical communications industry?s major event, OFCNFOEC ?13, was held in Anaheim, California, with global participation (in excess of 12,000 attendees) in the conference?s technical program and exhibit (more than 550 exhibiting companies). More than 800 technical presentations covered a broad range of optical communications technologies from advances in high-speed optical transport, software-defined networking (SDN), silicon photonics to optical interconnects in future computing systems, as well as progress in optical test and measurement. As we have witnessed in the past years, a vibrant global optical communications industry was in display at this year?s OFCNFOEC. [ABSTRACT FROM PUBLISHER]