Power-aware virtual optical network provisioning in flexible bandwidth optical networks [Invited]

Considering the virtual network infrastructure as a service, optical network virtualization can facilitate the physical infrastructure sharing among different clients and applications that require optical network resources. Obviously, mapping multiple virtual network infrastructures onto the same physical network infrastructure is one of the greatest challenges related to optical network virtualization in flexible bandwidth optical networks. In order to efficiently address the virtual optical network (VON) provisioning problem, we can first obtain the virtual links’ order and the virtual nodes’ order based on their characteristics, such as the bandwidth requirement on virtual links and computing resources on virtual nodes. We then preconfigure the primary and backup paths for all node-pairs in the physical optical network, and the auxiliary graph is constructed by preconfiguring primary and backup paths. Two VON mapping approaches that include the power-aware virtual-links mapping (PVLM) approach and the power-aware virtual-nodes mapping (PVNM) approach are developed to reduce power consumption for a given set of VONs in flexible bandwidth optical networks with the distributed data centers. Simulation results show that our proposed PVLM approach can greatly reduce power consumption and save spectrum resources compared to the PVNM approach for the single-line rate and the mixed-line rate in flexible bandwidth optical networks with the distributed data centers.     

Spectral resource defragmentation based on PCE in flexible bandwidth optical networks

The granularity of the flexible bandwidth optical network is the spectral slots,which is much smaller than that of the wavelength switch optical network.For the dynamic clients’ connections setup and tear down processes,it will give rise to fragmentation of spectral resources.It is the decline in the probability of finding sufficient contiguous spectrum for new connections that result in the fragmentation of spectral resource.To be more specific,these spectra may be unavailable and waste.In this case,the severe waste of the spectrum will lead to low efficiency in spectral utilization and will not adapt to large capacity requirements of transmission in the future.Because path computation element(PCE) framework has the characteristics of the central disposal and deployment of the spectrum resource,we construct the spectral resource allocation scenario based on PCE framework in the flexible bandwidth optical network to use spectrum resource effectively.Based on the principle of the generation of the fragmentation,we put forward a spectrum resource defragmentation algorithm to consolidate the available spectrum for clients’ connections.The simulation results indicate that this algorithm is able to reduce fragmentation of network,improve the continuity of spectral resource,reduce the blocking rate of services in the network and improve the spectral efficiency significantly.     

Survivable wireless networking — Autonomic bandwidth sharing in mesh networks

Mesh networking has recently received considerable attention, largely as a mechanism for providing enhanced connectivity without the need to install additional expensive infrastructure. It relies on the fact that underutilised local area connectivity can be used to connect constrained devices to those that possess wide-area uplink capabilities. However, at present, proposals for uplink bandwidth sharing are limited by the use of a traditional view of routing in which multiple end-user devices are associated with each individual uplink in such a way that all their off-network traffic is routed through that particular gateway. While this has the merit of simplicity, it is possible for a subset of gateways to be overloaded while others remain underutilised. We propose a new type of local mesh network, called the Coalition Peering Domain, the goal of which is to maximise Internet connectivity dynamically, smoothing out the usage of uplink capacity, albeit at the cost of slightly more complex control and management. Within this paper, we describe three main routing and addressing issues and then propose novel mechanisms that partially address those issues.     

Survivable integrated grooming in multi-granularity optical networks

Survivability is an important issue to ensure the service continuity in optical network. At the same time, with the granularity of traffic demands ranging from sub-wavelength-level to wavelength-level, traffic demands need to be aggregated and carried over the network in order to utilize resources effectively. Therefore, multi-granularity grooming is proposed to save the cost and reduce the number of switching ports in Optical-Cross Connects (OXCs). However, current works mostly addressed the survivable wavelength or waveband grooming. Therefore, in this paper, we propose three heuristic algorithms called Multi-granularity Dedicated Protection Grooming (MDPG), Multi-granularity Shared Protection Grooming (MSPG) and Multi-granularity Mixed Protection Grooming (MMPG), respectively. All of them are performed based on the Survivable Multi-granularity Integrated Auxiliary Graph (SMIAG) that includes one Wavelength Integrated Auxiliary Graph (WIAG) for wavelength protection and one waveBand Integrated Auxiliary Graph (BIAG) for waveband protection. Numerical results show that MMPG has the lowest average port-cost, the best resource utilization ratio and the lowest blocking probability among these three algorithms. Compared with MDPG, MSPG has lower average port-cost, better resource utilization ratio and lower blocking probability.     

灵活栅格光网络中业务公平性的研究

针对灵活栅格光网络中的业务公平性问题,提出业务分割-粗略分段(SS-RP)策略的频谱分配方案,其基本思想是将链路的频谱资源分为两部分,分别传输低速和高速业务,同时将高速业务分割成低速业务传输,以提高高速业务被服务的概率.     

Survivable virtual concatenation for data over SONET/SDH in optical transport networks

Next-generation SONET/SDH technologies-namely, generic framing procedure, virtual concatenation, and link-capacity-adjustment scheme-enable network operators to provide integrated data and voice services over their legacy SONET/SDH infrastructure to generate new revenue. An important open research problem on data over SONET/SDH (DoS) is survivability: SONET automatic protection switching is too resource inefficient for data services, and the protection mechanisms of data networks are too slow for mission-critical applications. We propose two approaches for provisioning survivable DoS connections. Our approaches exploit the tradeoff between resource overbuild and fault-recovery time while utilizing the inverse-multiplexing capability of virtual concatenation to increase backup sharing. Our results show that one approach achieves low resource overbuild and much faster fault recovery than that of data networks, and the other approach achieves fast fault recovery comparable to SONET 50-ms protection (for typical U.S. backbone networks) while still achieving modest backup sharing. We further investigate the tradeoff between network blocking performance and network control and management complexity resulting from the number of paths M a connection can be inversely multiplexed onto: larger M leads to more freedom in routing and better network performance but increases network control and management complexity. Our results indicate that the network blocking performance for small values of M (e.g., M=2 for some representative backbone network topologies) is almost as good as the case in which M is infinity.     

A novel shared-path protection algorithm with correlated risk against multiple failures in flexible bandwidth optical networks

In this paper, to decrease the traffic loss caused by multiple link failures, we consider the correlated risk among different connection requests when both the primary and backup paths are routed and assigned spectrum. Therefore, a novel shared-path protection algorithm is developed, named shared-path protection algorithm with correlated risk (SPP_CR), in flexible bandwidth optical networks. Based on the correlated risk, the routing can be diverse and the sharing in backup spectral resource will be restricted by SPP_CR algorithm, then the dropped traffic caused by simultaneous multiple failures between primary and backup path can be efficiently decreased. Simulation results show that, SPP_CR algorithm (i) achieves the higher successful service ratio (SSR) than traditional shared-path protection (SPP), shared-path protection with dynamic load balancing (SPP_DLB) and dedicated path protection (DPP); (ii) makes a better tradeoff in blocking probability, protection ratio (PR), average frequency slots consumed (AFSC) and redundancy ratio (RR) than SPP, SPP_DLB and DPP algorithms.     

ACO-based routing and spectrum allocation in flexible bandwidth networks

Optical networks with flexible bandwidth provisioning are a very promising networking architecture. It enables efficient resource utilization and supports heterogeneous bandwidth demands. In this paper, we focus on the dynamic routing and spectrum allocation (RSA) problem which emerges in such networks and propose a novel dynamic RSA algorithm by means of ant colony optimization (ACO). In our proposed algorithm, ants are launched to modify the routing table according to the length and the spectrum fragmentation information along the path. A simulation study is performed considering five algorithms in terms of blocking probability: WDM-based RWA approach, KSP-based RSA approach, Slot-based RSA algorithm, and our proposed ACO-based RSA approach. We then compare the deterioration degree of blocking probability by adding more types of line rate. Simulation results indicate that our proposed ACO-based RSA approach achieves lower blocking probability, complexity, and higher adaptability to more line rates mixture.     

Shareability in optical networks: beyond bandwidth optimization

We extend the famous path protection sharing scheme and introduce the generalized sharing concept. In this concept, we allow for additional sharing of important node devices in order to reduce network cost. These node devices (e.g., optical-electronic-optical regenerators and pure all-optical converters) constitute the dominant cost factor in an optical backbone network, and reduction of their number is of paramount importance. For demonstration purposes, we extend the concept of 1:N shared path protection to allow for the sharing of electronic regenerators needed to cope with optical transmission impairments. Considerable cost reductions in electronic budget are demonstrated through numerical examples.     

Intra-ONU bandwidth scheduling in Ethernet passive optical networks

Quality-of-service (QoS) support in Ethernet passive optical networks (EPON) is a crucial concern. However, most studies have only focused on optical line terminal (OLT) capacity allocation amongst multiple optical network units (ONU), and the further issue of intra-ONU allocation remains open. In this work a novel decentralized intra-ONU solution is presented using virtual-time schedulers. Results confirm good performance for a wide range of input traffic classes and loads.     

Survivable elastic optical networks: survey and perspective (invited)

Elastic optical networks (EONs) have been receiving extensive attention because of their inherent flexibility and the efficiency with which they allocate fiber-bandwidth. For an EON, survivability is of crucial importance because of the very high bandwidth that it carries on each optical channel. In this article, we review the current state of the art of survivable EONs which reviews the literature to summarize the following aspects: (a) spectrum resource sharing among backup lightpaths, (b) sharing of high-speed optical transponders, (c) effect of spectrum conversion, (d) bandwidth squeezed restoration (BSR), (e) joint restoration by multiple sub-band optical channels, (f) multi-layer survivability, and (g) energy efficiency. Apart from a summary on the current research status, we also discuss open research issues which are important to survivable EONs from the perspectives of (a) impact of spectrum conversion, (b) impact of elastic optical transponder configuration, (c) impact of physical layer impairments and limitations, (d) protection-path-based spectrum defragmentation, and (e) network availability.     

Automatic configuration in future semi-transparent distributed optical networks

The recent commercial development of photonic switches has created many new semi-transparent optical architectures with core nodes made up of an all-optical switch controlled by an IP router. The fact that the nodes are transparent to the switched data complicates the implementation of operations such as interface and link configuration. In this article we present first an algorithm that allows these semi-transparent nodes to be self-configured. The algorithm optimizes the total configuration time by exploiting the capability of optical switches to execute many connections at the same time. Then we present a solution for the link configuration issue that does not require a pre-established control channel between the nodes. The two solutions represent a first step towards the complete automation of future semi-transparent optical networks. The benefits brought by our methods are demonstrated by both simulation and testbed results.     

All-optical signal processing technologies in flexible optical networks

Photonic Network Communications - All-optical signal processing has always been critical assistance for the flexible optical networks (FONs) development which realizes various signal processing...     

A distributed LSP scheme to reduce spare bandwidth demand in MPLS networks

A preplanned path-protection scheme with sufficient spare bandwidth is appropriate for real-time fault restoration in multiprotocol label switching (MPLS) networks. In this case, however, it is important to reduce the amount of spare bandwidth to prevent degradation of network efficiency. A distributed label switched path (D-LSP) scheme is proposed to reduce the amount of spare bandwidth required for protecting against network faults in MPLS networks. The main idea of the proposed D-LSP scheme is to partition traffic into multiple LSPs, each of which is established on a distinct link-disjoint route between each pair of end nodes. The D-LSP scheme is evaluated in terms of the reduction ratio of total network cost in comparison with the conventional LSP scheme. Traffic partitioning in the D-LSP scheme can decrease the statistical multiplexing gain (SMG) obtained by aggregating IP packet flows into an LSP. The tradeoff between spare bandwidth reduction and degradation of SMG due to traffic partitioning is also investigated. The numerical results show that the proposed D-LSP scheme yields the network cost-reduction ratio (NCRR) of at least 29%, 27%, and 15% for the networks where average node degrees are 4.6, 4.4, and 3.2, respectively. The D-LSP scheme shows the similar performance of NCRR in both Markovian traffic and self-similar traffic environments.     

Towards efficiently migrating virtual networks in cloud-based data centers

With the expansion of cloud computing, virtual network (VN) migration becomes the very perspective technology for saving energy, ensuring Service Level Agreements or improving the survivability of virtual networks in cloud networks. At present, the majority of research on the VN migration, however, are for saving energy or improving resource utilizations, and few of them for the entire virtual network migration for guaranteeing QoS or improving the survivability of virtual networks. Since the regional failure, network maintenance or QoS violation, the service provider generally needs to migrate the VN for guaranteeing the QoS or improving the survivability of virtual networks. In the paper, we research the live migration problem of the virtual network to optimize the virtual network migration performance. To efficient migrate virtual network, we present an effective VN migration method, VNM. To control the cost of migration or migration traffic, based on the VNM algorithm, we present an effective VN migration method with migration traffic control, VNM-MTC. We use two networks as substrate networks to simulate the performances of our presented algorithms. From the experiment, we can see that the total VN reconfiguration cost, total VN redeployment cost, total VN migration cost and blocking ratio of our presented algorithms are better than that of the contrast algorithm.     

A hybrid cycle bandwidth allocation scheme with differentiated services support in Ethernet passive optical networks

The Ethernet passive optical network (EPON) has emerged as one of the most promising solutions for next generation broadband access networks. Designing an efficient upstream bandwidth allocation scheme with differentiated services (DiffServ) support is a crucial issue for the successful deployment of EPON, carrying heterogeneous traffic with diverse quality of service (QoS) requirements. In this article, we propose a new hybrid cycle scheme (HCS) for bandwidth allocation with DiffServ support. In this scheme, the high-priority traffic is transmitted in fixed timeslots at fixed positions in a cycle while the medium- and low-priority traffic are transmitted in variable timeslots in an adaptive dynamic cycle. A suitable local buffer management scheme is also proposed to facilitate QoS implementation. We develop a novel feature providing potentially multiple transmission opportunities (M-opportunities) per-cycle for high-priority traffic. This feature is significant in improving delay and delay-variation performance. The HCS provides guaranteed services in a short-cycle scale for delay and jitter sensitive traffic while offering guaranteed throughput in a moderately long-time scale for bandwidth sensitive traffic and at the same time maximizing throughput for non-QoS demanding best-effort traffic. We develop analytical performance analysis on the deterministic delay bound for high-priority traffic and minimum throughput guarantees for both high- and medium-priority traffic. On the other hand, we also conduct detailed simulation experiments. The results show a close agreement between analytical approach and simulation. In addition, the simulation results show that the HCS scheme is able to provide excellent performance in terms of average delay, delay-variation, and throughput as compared with previous approaches.

A novel distributed control protocol in dynamic wavelength-routed optical networks

Path selection has long been one of the most important issues in the network design and management, which is also referred to as routing and wavelength assignment in the optical network domain. In this article we investigate the RWA problem for dynamic wavelength-routed mesh networks in a fully distributed controlled environment. We present a novel routing and signaling protocol called Asynchronous Criticality Avoidance (ACA), which is devised to reduce the mutual interference between lightpaths launched by different source-destination pairs to improve network performance in terms of blocking probability. With the fixed alternate routing architecture, the ACA protocol dynamically marks a set of wavelength channels as critical if the occupancy of the channels causes a bottleneck between an S-D pair with a width equal to or narrower than a predefined threshold. To support a distributed control environment, a suite of signaling processes is devised to realize the criticality avoidance mechanism, with which a two-stage routing and wavelength assignment (or criticality avoidance routing) is performed. The ACA protocol has been shown by simulations to be capable of better performance than existing schemes.     

128 Gbit/s high speed optical interconnection networks in data centers by a 30 GHz Mach-Zehnder modulator

A decision feedback equalization (DFE) algorithm is proposed by simplifying Volterra structure. The simplification principle and process of the proposed Volterra-based equalization algorithm are presented. With the support of this algorithm, the signal damage for four-level pulse amplitude modulation signal (PAM-4) is compensated, which is caused by device bandwidth limitation and dispersion during transmission in C-band intensity modulation direct detection (IM-DD) fiber system. Experiments have been carried out to demonstrate that PAM-4 signals can transmit over 2 km in standard single-mode fiber (SSMF) based on a 30 GHz Mach-Zehnder modulator (MZM). The bit error rate (BER) can reach the threshold of hard decision-forward error correction (HD-FEC) (BER=3.8×10-3) and its sensitivity is reduced by 2 dBm compared with traditional feedforward equalization (FFE). Meanwhile, the algorithm complexity is greatly reduced by 55%, which provides an effective theoretical support for the commercial application of the algorithm.     

Partitioned optical passive star (POPS) multiprocessorinterconnection networks with distributed control

This paper presents a partitioned optical passive star (POPS) interconnection topology and a control methodology that, together, provide the high throughput and low latency required for tightly coupled multiprocessor interconnection applications. The POPS topology has constant and symmetric optical coupler fanout and only one coupler between any two nodes of the network. Distributed control is based on the state sequence routing paradigm which multiplexes the network between a small set of control states and defines control operations to be transformations of those states. These networks have highly scalable characteristics for optical power budget, resource count, and message latency. Optical power is uniformly distributed and the size of the system is not directly limited by the power budget. Resource complexity grows as O(n) for the couplers, O(n√n) for transceivers, and O[√nlog(n)] for control. We present analysis and simulation studies which demonstrate the ability of a POPS network to support large scale parallel processing (1024 nodes) using current device and coupler technology