Optical Virtual Private Networks Research Articles

Flexible PON systems enabling optical virtual private network and upstream channel upgrade

With the rapid growth of peer-to-peer (P2P) traffic in the access network, the capability to implement inter-optical network unit (ONU) communication (IOC) has become a fundamental requirement for the underlying passive optical network (PON). The conventional IOC is realized electronically on layer 2 or layer 3 and relies on the transfer operations in the optical line terminal (OLT), thus resulting in high transmission latency and excessive bandwidth consumption. To achieve an efficient IOC, the optical virtual private network (OVPN) is proposed to establish direct optical layer links among ONUs by adding some auxiliary optical components to the existing PON system. However, in previously reported OVPN schemes, the added devices are only used for IOC and cannot fulfill other network functions, which leads to poor flexibility. To improve the reconfigurability of the whole PON system, we present two simple modifications that can not only achieve a high-bandwidth OVPN but also increase the upstream channel capacity. The proposed schemes introduce a new wavelength as the OVPN channel to refrain from changing the physical configuration of the normal upstream and downstream. One scheme retrofits the optical line terminal (OLT) with a fiber Bragg grating (FBG) based reflection module, while the other employs an additional short-length distribution fiber for each ONU to redirect IOC traffic. In both schemes, optical switches (OSWs) are used to control the added OVPN wavelength and the original upstream wavelength so that the two wavelengths can transmit IOC traffic and upstream traffic flexibly. According to the states of OSWs, PON systems will form multiple working modes adapted to different network conditions. To evaluate the improvement in flexibility of wavelength usage, the throughput performances of proposed schemes were analyzed theoretically under varying offered loads and IOC traffic proportions. In addition, the feasibility of both schemes was verified through physical layer simulations, where the optical spectra and bit error rates (BERs) of signals on different wavelengths were investigated.

A Capacity Allocation Algorithm for Optical Virtual Private Networks

As the development of optical communication technologies such as Wavelength-Division Multiplexing (WDM), it is important to support virtual private networks (VPN) over WDM networks. In order to overcome the limits of WDM network capacity and achieving more revenue new VPNs, an optimal model supporting both optical VPN and IP VPN on WDM networks is proposed to admit the maximum number of new VPNs without influencing the QoS guarantee for the existing VPNs. Furthermore, three heuristic algorithms are designed to simplify the computation process of getting optimal solution. The simulation results over MESH WDM networks show the algorithm can takes advantage of the reliable transmission capability of WDM networks and provides diverse QoS for different traffic streams by different quality of optical transmission.

Hybrid crosstalk aware Q-Factor analysis for selection of optical virtual private network connection

The presence of physical layer impairments (PLIs) in high-speed optical virtual private network (OVPN) over wavelength-division multiplexing/ dense-wavelength division multiplexing network degrades the connection quality (CQ). The quality can be numerically expressed as the quality factor (Q-Factor) of the connection. The CQ can be further affected by the increasing demand of connections and data speed. It is important to have an efficient OVPN control manager (OVPNCM) to maintain the CQ. OVPNCM can ensure better quality of transmission to the OVPN clients. Traditional routing and wavelength assignment (RWA) algorithms have less regards to the PLIs and cannot provide guaranteed OVPN connection (OVPNC) quality. In order to achieve a guaranteed CQ, we proposed a wavelength assignment (WA) scheme and a hybrid crosstalk model based on linear in-band and nonlinear four-wave mixing crosstalk. The performance of the proposed WA scheme with the hybrid crosstalk model is demonstrated. The results show that the proposed hybrid crosstalk model with WA scheme not only provides a guaranteed OVPNC, but also improves the OVPN performance in terms of blocking probability.

Enabled scalable and privacy wavelength division multiplexing-radio over fiber system based on optical virtual private networks

Abstract. A new wavelength division multiplexing (WDM)-based radio over fiber (RoF) system is proposed for optical virtual private network (OVPN) communication between inter-base stations (inter-BSs) or intra-BSs, using four-wave mixing (FWM) in a semiconductor optical amplifier as well as wavelength reflection of fiber Bragg gratings. By establishing inter-BSs and intra-BSs OVPN link of a 60-GHz WDM-RoF system, the private channels for the communication of end users under different BSs of sub-RoFs can be provided. In our scheme, 58 and 60-GHz millimeter waves are used to carry OVPN data and downstream data, respectively. Furthermore, the scalability of the proposed system is improved by the integration of an RoF system, WDM, and FWM. The simulation results successfully verify the feasibility of our proposed scheme.

Principle and verification of novel optical virtual private networks over multiprotocol label switching/optical packet switching networks

A novel realization method of the optical virtual private networks (OVPN) over multiprotocol label switching/optical packet switching (MPLS/OPS) networks is proposed. In this scheme, the introduction of MPLS control plane makes OVPN over OPS networks more reliable and easier; OVPN makes use of the concept of high reconfiguration of light-paths offered by MPLS, to set up secure tunnels of high bandwidth across intelligent OPS networks. Through resource management, the signal mechanism, connection control, and the architecture of the creation and maintenance of OVPN are efficiently realized. We also present an OVPN architecture with two traffic priorities, which is used to analyze the capacity, throughput, delay time of the proposed networks, and the packet loss rate performance of the OVPN over MPLS/OPS networks based on full mesh topology. The results validate the applicability of such reliable connectivity to high quality services in the OVPN over MPLS/OPS networks. Along with the results, the feasibility of the approach as the basis for the next generation networks is demonstrated and discussed.

Optical Power Aware Quality Analysis for the Selection of Optimal OVPN Connection over WDM Network

Traditional optical networks such as synchronous optical network/synchronous digital hierarchy (SONET/SDH) have been perceived as high transmission rate networks without providing any QoS to different connection request. Recently, some attention has been given to coarse-grain QoS using differentiated optical services. Some designs for static VPN have been proposed in literature. However, little research work has been considered to provide dynamic VPN on optical networks. By applying the virtual private network concept to WDM, which is called as Optical Virtual Private Network (OVPN), we explore how to compute a fine-grained QoS for dynamic OVPN connection request based on system components such as connectors, splices, etc. An important problem in WDM network design is to construct an algorithm to determine the optimal OVPN Connection from a set of possible connections in a network topology, which can maximize the quality of service to the OVPN clients. By keeping that in mind, we proposed a method of optimal OVPN selection mechanism based on the traditional power budget analysis.

Reconfigurable and Scalable All-Optical VPN in WDM PON

In this letter, we propose and experimentally demonstrate an all-optical virtual private network (VPN) structure in a wavelength-division-multiplexed (WDM) passive optical network (PON). The scheme utilizes a semiconductor optical amplifier (SOA) in optical line terminal (OLT) to transfer optical VPN data among different optical network units (ONUs) based on the cross-gain-modulation (XGM) effect. By dynamically copying the optical VPN signal onto different wavelengths, the optical VPN can be reconfigured.

Performance Analysis of OVPN Over OBS/MPLS Architecture with Different Priorities Traffic

The implementing of optical virtual private networks (OVPNs) over an optical burst-switching (OBS) network based on MPLS is discussed. The network architecture, the core and access nodes faculty are described. We also propose a new model with three traffic priorities, which used to analysis the delay and blocking performance of OVPN over OBS/MPLS network based on queuing theory.

A Novel Method of Optical VPN over OBS Network Based On MPLS

A Novel Method of Optical VPN over OBS Network Based On MPLS

Priority-based minimum interference path multicast: routing algorithm in optical virtual private network

While the “Virtual Private Network (VPN) over Internet” is cost-effective and flexible, it suffers from the difficulty of providing adequate transmission capacity for high bandwidth services. Hence a Dense Wavelength Division Multiplexing (DWDM) based “Optical VPN (OVPN)” technology has been regarded as a good alternative for realizing the future VPN services. To improve the transparency and data rate of OVPN, it is critical to consider the problem of Routing and Wavelength Assignment (RWA) for transmission capacity utilization. This paper proposes a Priority-based Minimum Interference Path Multicast Routing (PMIPMR) algorithm, a new routing algorithm which finds alternative routes based on node priorities and Virtual Source (VS) nodes that has both splitting and wavelength conversion, and then chooses a path that does not interfere with potential future multicast session requests when congestions occur in the network. The PMIPMR algorithm reduces blocking rate significantly and increases the wavelength utilization by avoiding congestion in future multicast session requests. We measured the performance of the proposed algorithm in terms of blocking rate and the resource utilization. The simulation results demonstrate that the PMIPMR algorithm is superior to the previous multicast routing algorithms using the Capability-based-Connection algorithm based on Capability-based-Priority and Spawn-from-VS methods.

A Service Oriented Architecture-based Approach for Interdomain Optical Network Services

This work presents a service-oriented architecture for interdomain service provisioning in optical networks. The architecture introduces a service layer that concentrates all the interactions among domains necessary for service provisioning. A service layer is an alternative to the GMPLS (Generalized Multiprotocol Label Switching) architecture, but without a rigid control plane as found in GMPLS. We start by defining a set of basic services to provide single end-to-end (e2e) interdomain connections. Then, more sophisticated services are created through the composition of these basic services. The interdomain Optical VPN (Virtual Private Network) service is considered in order to illustrate the composition of services. A prototype of the architecture was designed and implemented using Web services as the main technology. The architecture was evaluated in terms of speed, scalability, and bandwidth consumption necessary to establish e2e interdomain connections and Optical VPNs.

Virtual source-based minimum interference path multicast routing in optical virtual private networks

Virtual Private Network (VPN) services over the Internet are gaining increased acceptance due to the economic benefits and flexibility. However, with difficulties of providing sufficient transmission capacity for value-added and mission-critical services, the Optical VPN (OVPN) deploying Dense Wavelength-Division Multiplexing (DWDM) technology has been seen as a favorable approach for realizing the future VPN services. In an OVPN, the Routing and Wavelength Assignment problem plays a key role for capacity utilization and therefore the Multicast Routing and Wavelength Assignment problem has been the dominant issue in a DWDM-based OVPN. In this paper, using Virtual Source (VS) nodes that have splitting and wavelength conversion capabilities, we propose a new Multicast Routing and Wavelength Assignment method for multicast sessions. The algorithm combines the VS-based tree generation approach with Multi-Wavelength Minimum Interference Path Routing (MW-MIPR) that chooses a path that does not interfere too much with potential future multicast session requests.

Virtual source-based minimum interference path multicast routing in optical virtual private networks

A major concern in optical burst-switched (OBS) networks is contention, which occurs when more than one bursts contend for the same data channel at the same time. Due to the bufferless nature of OBS networks, these contentions randomly occur at any degree of congestion in the network. When contention occurs at any core node, the core node drops bursts according to its dropping policy. Burst loss in OBS networks significantly degrades the throughput of TCP sources in the local access networks because current TCP congestion control mechanisms perform a slow start phase mainly due to contention rather than heavy congestion. However, there has not been much study about the impact of burst loss on the performance of TCP over OBS networks. To improve TCP throughput over OBS networks, we first introduce a dropping policy with burst retransmission that retransmits the bursts dropped due to contention, at the ingress node. Then, we extend the dropping policy with burst retransmission to drop a burst that has experienced fewer retransmissions in the event of contention at a core node in order to reduce the number of events that a TCP source enters the slow start phase due to contention. In addition, we propose to limit the number of retransmissions of each burst to prevent severe congestion. For the performance evaluation of the proposed schemes, we provide an analytic throughput model of TCP over OBS networks. Through simulations as well as analytic modeling, it is shown that the proposed dropping policy with burst retransmission can improve TCP throughput over OBS networks compared with an existing dropping policy without burst retransmission.

Multi-tiered service survivability in next-generation SONET/SDH networks

The Optical Virtual Private Networks (OVPNs) are going to be the next step of the present Internet Protocol or Multi-Protocol Label Switching-based VPNs. Since reliability and continuity of service are the major requirements in the design of OVPN, researchers are now paying more attention to its survivability issue. In this paper, we propose a highly simple approach for spreading out the lightpaths over the core optical network using shortest pair algorithm that mitigates the impact of multiple link failures in an OVPN. The special feature of the proposed Distributed Lightpath Routing algorithm lies in its simplicity and less computation for the working path as well as for the backup path.

Optimal placement of multicast and wavelength converting nodes in multicast optical virtual private network

This paper addresses multicast-nodes (MC-nodes) and wavelength converting-nodes (WC-nodes) placement problem in multicast optical virtual private network (M-OVPN). This problem is motivated by the high cost incurred in the usage of optical splitters and converters in the VPN due to complexity and power considerations. An analytical model for computing the approximate blocking probability in M-OVPN with wavelength conversion has been developed. The placement of both MC-nodes and WC-nodes is determined using our proposed innovative Removal algorithm together with the blocking performance computed. We perform simulation studies of our algorithms using NSFNET as the network topology. The results show that the Removal heuristic is able to locate the optimal placement location within a much shorter time and with higher efficiency compared to existing heuristic. In addition, we also show the flexibility of the heuristics by introducing the hybrid (Combined Removal) and dual (Concurrent Removal) removal mode.

Distributed wavelength router for optical virtual private networking in metropolitan areas

A modular wavelength router suitable for flexibly configuring optical virtual private networks over a star-star cable plant with no more than three hops is proposed and its feasibility is experimentally demonstrated.

An Overview of Virtual Private Network (VPN): IP VPN and Optical VPN

Recently, there has been rapid development and deployment of virtual private network (VPN) services. There are wide varieties of IP-based VPNs and optical VPNs (OVPNs) proposed in the literature and readers could easily get confused with so many different types of VPNs. The purpose of this paper is to present a comprehensive overview of the VPN and discuss the main issues associated with the design of IP VPN and OVPN. We first present a classification of the VPNs including CE-based, network based, customers provisioned, provider provisioned, connection oriented, connectionless oriented, port based, connection based, layer 1 VPN, layer 2 VPN, and layer 3 VPN, and describe different VPN protocols such as IPSec, GRE and MPLS. We then review the recent work on OVPN by different standard bodies, and outline the key requirements for OVPN service providers and customers. Finally, we describe several OVPN architectures appeared in the literature, highlight the future work in OVPN.

Optical Virtual Private Networks: Applications, Functionality and Implementation

Today's economic environment presents special challenges for telecommunication carriers—finding new ways to drive down network costs i, without limiting future growth opportunities. Minimizing operating expenses and capital expenditures is not sufficient to ensure future prosperity. New, value-added services can help carriers increase their revenues and profits—today. Virtual private networks (VPNs), both data (IP & MPLS) and optical, fit the description of value-added services. VPN services have received ample attention over the last few years as they are viewed by carriers as an attractive value added service and by customers as a cost effective replacement of leased private lines. VPNs can also help carriers reduce their costs—both capital and operational—by supporting multiple customers, each allowed with varying levels of network control and management over the same (shared) infrastructure. Optical virtual private networks (O-VPNs) represent the next step in the evolution of VPNs and provide similar underlying benefits as other VPN technologies to carriers. Although both carriers and vendors have been talking about O-VPNs for years, the first commercially viable solutions started becoming available in early 2002 [1]. O-VPNs provide carriers with new revenue opportunities as well as the potential to reduce their operating and capital costs. Additionally, O-VPNs offer carrier-customers several benefits, including lower networking costs, increased network flexibility and control, and improved network operational efficiency.

Configuring Traffic Grooming VP Ns

A VPλN is an optical virtual private network (oVPN) built of wavelength paths within a multihop wavelength routing (WR) dense wavelength division multiplexing (DWDM) network. An efficient and general graph-theoretic model (the wavelength-graph (WG)) has been proposed along with an integer linear programming (ILP) formulation of setting up VPλNs with given traffic requirements over a given WR-DWDM network with two protection scenarios. Here, we have exploited the advantages of traffic grooming, i.e., numerous traffic streams of a VPN can share a wavelength path. We have also generalized the model for setting up VPNs over a WR-DWDM system where multiple VPNs can share a single wavelength path. The objective of the optimization is in all cases to reduce resource usage at upper (electrical) layers (i.e., to reduce the load of the virtual routers), subject to constrained amount of capacity of each wavelength channel and limited number of wavelengths. Here, we propose and compare three basic methods for configuring oVPNs and investigate various parameter settings.

Virtual Topology Design and Reconfiguration of Virtual Private Networks (VPNs) over All-Optical WDM Networks

This paper studies the virtual topology design and reconfiguration problem of virtual private networks (VPNs) over all-optical WDM networks. To support VPN service, a set of lightpaths must be established over the underlying WDM network to meet the VPN traffic demands and this set of lightpaths must also be dynamically reconfigurable in response to changing VPN traffic. To achieve good network performance and meet the service requirements of optical virtual private networks (oVPNs), we formulate the problem as an integer programming problem with multi-objectives and present a general formulation of the problem. In the formulation, we take into account the average propagation delay over a lightpath, the maximum link load, and the reconfiguration cost with objectives to minimize the three metrics simultaneously. The formulated problem is NP-hard and is therefore not practical to have exact solutions. For this reason, we use heuristics to obtain approximate optimal solutions and propose a balanced alternate routing algorithm (BARA) based on a genetic algorithm. To make the problem computationally tractable, we approximately divide BARA into two independent stages: route computing and path routing. At the route computing stage, a set of alternate routes is computed for each pair of source and destination nodes in the physical topology. At the path routing stage, an optimal route is decided from a set of alternative routes for each of the lightpaths between a pair of source and destination nodes. A decision is subject to the constraints and objectives in the formulation. To improve the computational efficiency, we use a genetic algorithm in BARA. Through simulation experiments, we show the effectiveness of BARA and the evolution process of the best solution in a population of solutions produced by the genetic algorithm. We also investigate the impact of the number of alternative routes between each pair of source and destination nodes on the optimized solutions.