Forward error correction in optical core and optical access networks

With different vendor equipments being deployed in the core and metro networks, automated end-to-end service provisioning across multi-vendor optical networks poses new challenges from an architectural and protocol standpoint. Traditionally, telecommunications networks have been managed in a proprietary fashion using centralized Network/Element Management Systems (NMS/EMS). The Telecommunications Management Forum (TMF) is standardizing NMS/EMS interaction with the aim of achieving multi-vendor equipment interoperability. This standardized management plane based end-to-end architecture appears to be the quickest path to short-term core and metro network interoperability (compared to a longer-term distributed control plane provisioning approach of GMPLS being developed at IETF). We consider the problem of routing end-to-end metro sub-rate circuits (STS-1/3/12) across the wavelength switched (STS-48/192) core under various NMS/EMS interaction and information exchange models. We propose an algorithm framework for efficient packing of sub-STS-48 paths onto STS-48/192 paths in the core network so as to improve capacity utilization and reduce blocking. At any given time, there will be a number of provisioned STS-48/192 paths in the core network that are partially used up and have available capacity. We call such paths "fragmented paths". The objective of efficient packing is to minimize the number of fragmented paths in the core network at any given time, while trying to minimize end-to-end path costs also. To achieve this, the portion of a sub-STS-48 circuit through the core network may be multiplexed within one or more provisioned STS-48/192 paths. The way these circuits are multiplexed depends on the grooming capability of the core and metro networks.

Content caching is an effective technique that reduces network power consumption by reducing the path between users and requested video content. This paper examines the benefit of caching in an IP over WDM core network with respect to current and future networks. It compares the power savings due to caching in current implementations of optical networks to potential power savings when future optical network features are realized. Future optical core networks are considered with three major power efficiency improvements over current networks. First, network devices are equipped with sleep-mode capabilities where inactive parts of storage devices are put in low-power mode. Second, optical bypass is employed where intermediate IP routers are not engaged in traffic routing. Third, the power consumption of router ports is significantly reduced, consequently reducing the power consumption of transport. The results show that content caching is effective in reducing power consumption under both current and future optical networks, making caching a successful option for video delivery in the future Internet.

Optical networks—the electro-optic reality

In this paper, we present a novel networking technique based on optical Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM). We highlight the interesting features of the solution with respect to existing ones (fully opaque optical networks and transparent networks) for optical metro and core networks. We show that under certain traffic condition MB-OFDM may offer useful flexibility in the context of increasing wavelength bit rates.

Statistical multiplexing at the optical layer has been considered a critical requirement in order to build the next generation of ultra-high capacity optical transport networks in a cost-efficient manner. However, even today, the state of the art of commercially available optical core networks is based on mature wavelength switching and routing technologies, which lack a transport and control plane architecture that can support statistical traffic multiplexing with guaranteed Quality of Service (QoS) across a wide range of QoS parameters even if they can support fast reconfiguration at msec time scales. For several years, most research efforts have focused on the concepts of Optical Burst Switching (OBS) and Optical Packet Switching (OPS), which are based on the hybrid use of electronic nodes and optical switches to exploit Time Division Multiplexing (TDM) in order to achieve statistical multiplexing and dynamic resource reservation over optical networks. While burst switching has been experimentally proven as a technically feasible technique, its performance suffers especially under strict requirements for QoS guarantees. In this paper we evaluate the performance gains that can be achieved exploiting statistical multiplexing over a large scale core optical network and we demonstrate the efficiency of the CANON architecture (Clustered Architecture for Nodes in an Optical Network) as a viable alternative to OBS, which can achieve both targets for statistical multiplexing gains and QoS guarantees at the same time.

The Internet generation infrastructure is growing and moving towards a consistency model of high-speed nodes interconnected by optical core networks. Therefore, the interaction between IP and optical network layers, specifically, the routing and signalling aspects, are maturing and they can lead to enhance the services and network performance. At the same time, a consensus has emerged in the industry on utilizing IP-based protocols for the optical control plane. This paper defines a new technique for IP over Optical networks (interacting between bottom layers), considering both the IP-based control plane for optical networks as well as IP-optical network interactions (together referred to as “IP over optical networks”). In this paper, a new technique is proposed that reduces recovery time by making an interoperation between the data link layer (layer 2) with the network layer (layer 3). The proposed technique enables layer 2 with layer 3 to make a hybrid mechanism that improves the recovery time in the network through two cases (1st-Detection and 2nd-Rerouting). The technique involves detecting failure in less time through layer 2 and rerouting traffic through an alternative path between source and destination by using a new algorithm in layer 3 to deliver data packets without the need to wait for the routing protocol to update the network topology and compute the routing table. In case of the network recovery, layer 2 has demonstrated its capability to detect failure extremely quickly shown through the immediate detection of the loss of signals for the link or node. The recovery mechanism, i.e., the rerouting mechanism, which leads the node, switches the data packets through an adjacent node to its destination via the life node. The latter is created by the proposed mechanism before the occurrence of the failure. The aim of this mechanism is to avoid loss of packets, improve QoS and improve recovery time as we have shown in the results shown below.

In this paper, we examine the QoS issues in the intelligent optical network (ION), and specially focus on the QoS implementation scheme associated with the control plane. Referring to the QoS models in IP networks, we propose the optical IntServ QoS model using in metropolitan optical networks, and the optical DiffServ QoS model using in core optical networks. The networks to support optical IntServ QoS model must deal with each traffic request for QoS assurance, then compute routes and establish lightpaths. In the optical DiffServ QoS model, core networks only accept the limited classes of QoS requests. Therefore traffic flows with similar QoS requirements from the metropolitan networks must be aggregated, and then core networks provide tunnels for them. It increases the scalability of networks. In the end, this paper presents the generalized control plane architecture of the node in ION, which is based on extended GMPLS and able to guarantee subscriber’s QoS using two optical QoS models.

The growing energy consumption has posed new challenges for the future development of networks. Some earlier work has proposed solutions to improve energy consumption based on the existing control plane, for example, node/links sleeping. This study presents a new possibility to reduce network energy consumption by proposing a new integrated control plane structure utilising Software Defined Networking technologies. The integrated control plane increases the efficiencies of exchanging control information across different network domains, while introducing new possibilities to the routing methods and the control over quality of service (QoS). The structure is defined as an overlay generalised multi-protocol label switching (GMPLS) control model. With the defined structure, the integrated control plane is able to gather information from different domains (i.e. optical core network and the access networks), and enable energy efficiency networking over a wider area. In the case presented, the integrated control plane collects the network energy related information and the QoS requirements of different types of traffic. This information is used to define the specific group of traffic's (flow's) routing behaviours. With the flexibility of the routing structure, results show that the energy efficiency of the network can be improved without compromising the QoS for delay/blocking sensitive services.

It is widely believed that IPTV will be one of the major applications in future IP networks and that IP over optical networks will be a major component of the next generation Internet. However, it is not efficient to map a single multicast IPTV flow into one light tree because the required bandwidth of an IPTV flow is usually much less than the capacity of a light-tree. Furthermore, pay-per-view or secure flows should be sent only to authorized users. In this paper, we study the problem of multi-class multicast flow aggregation with the constraint that secure programs are sent to authorized nodes. We first describe the problem and prove it to be NP-complete. We then formulate an integer linear program (ILP) and give results for small scale problems. Heuristic algorithms are presented, and results show that our heuristics achieve good results in both small and large scale problems. Also simulations show that the ratio of secure programs over total programs has great impact on the final aggregation results.

Optical networks have developed rapidly over the last ten years and show every sign of continuing to grow and adapt to the new challenges of supporting more traffic, more reliably and flexibly, at lower cost. We briefly review the developments of the last ten years and then discuss current thinking on how core optical networks will develop into the future, exploring the similarities and differences with the previous generation of technologies. We have attempted to provide a ‘low-jargon’ paper with links to more detailed studies where appropriate.

PON versus AON: Which is the best solution to offload core network by peer-to-peer traffic localization

Optical access networks are envisioned to become increasingly complex as they support more and more diverse and immersive services, each with a different capacity, latency, and reliability need. While machine learning has been touted as a silver bullet that will intelligently manage network operations and resources to meet these demands, as it had been anticipated for core and metro networks, there exist various challenges that need to be addressed to progress machine learning models from research to production. In this tutorial, we first aim to motivate the continued push to advance optical access networks and rationalize the use of machine learning in these networks. We then highlight the challenges that are especially amplified due to the traffic dynamicity and heterogeneity, data scarcity, and computation-resource constraints of optical access networks. We discuss emerging machine learning approaches that are being explored to address these challenges. Finally, we consider a fast and self-adaptive machine learning enhanced dynamic bandwidth allocation scheme in an illustrative future use case of supporting immersive human-to-machine communications over the mobile fronthaul of next-generation mobile networks.

The Core Optical Networks (CORONET) program addresses the development of architectures, protocols, and network control and management to support the future advanced requirements of both commercial and government networks, with a focus on highly dynamic and highly resilient multi-terabit core networks. CORONET encompasses a global network supporting a combination of IP and wavelength services. Satisfying the aggressive requirements of the program required a comprehensive approach addressing connection setup, restoration, quality of service, network design, and nodal architecture. This paper addresses the major innovations developed in Phase 1 of the program by the team led by Telcordia and AT&T. The ultimate goal is to transfer the technology to commercial and government networks for deployment in the next few years.

Energy consumption has become a critical issue for system vendors and network operators. This paper studies the power consumption or colored line interfaces in converged packet optical core networks and their contribution to the overall power consumption of the network. The power consumption distribution among the different network components is also presented.

Optical performance monitoring (OPM) is an important approach to determine the quality of optical channels within an optical core network without passing data through optoelectronic regeneration at the monitor points. Using this approach, the quality or "health" of signals can be determined at arbitrary points in a network without knowledge of the transport history of the data or the details of the transmission path. We report experimental results on the use of subcarrier multiplexing (SCM) to perform a variety of monitoring functions including chromatic dispersion monitoring, wavelength registration, power monitoring, and signal-to-noise ratio (SNR) monitoring.