Metro Network Architecture Research Articles

ARMONIA: A Unified Access and Metro Network Architecture

We present a self-configured and unified access and metro network architecture, named ARMONIA. The ARMONIA network monitors its status, and dynamically (re-)optimizes its configuration. ARMONIA leverages software defined networking (SDN) and network functions virtualization (NFV) technologies. These technologies enable the access and metro convergence and the joint and efficient control of the optical and the IP equipment used in these different network segments. Network monitoring information is collected and analyzed utilizing machine learning and big data analytics methods. Dynamic algorithms then decide how to adapt and dynamically optimize the unified network. The ARMONIA network enables unprecedented resource efficiency and provides advanced virtualization services, reducing the capital expenditures (CAPEX) and operating expenses (OPEX) and lowering the barriers for the introduction of new services. We demonstrate the benefits of the ARMONIA network in the context of dynamic resource provisioning of network slices. We observe significant spectrum and equipment savings when compared to static overprovisioning.

Low-cost hybrid ROADM architectures for scalable C/DWDM metro networks

CWDM networks have proven to be a promising first-step metro and access network architecture, offering a significant cost advantage over DWDM due to the lower cost of lasers and the filters used in CWDM modules. If demand grows beyond the capacity covered by CWDM channels, DWDM network elements can be introduced to merge CWDM and DWDM traffic at the optical layer. This ensures two advantages: reduced initial investment and scalability for deploying DWDM channels in the future. This article presents various ROADM architectures, and explores the novel optical node architecture of hybrid C/DWDM networks, consisting of CWDM, hybrid C/DWDM, and junction nodes connecting two rings. Evaluation has shown that the hybrid ROADM architecture is superior to other conventional ROADM architectures in terms of scalability and the initial cost of optical nodes and networks.

Full Featured and Lightweight Control for Optical Packet Metro Networks [Invited

Metro networks support increasing traffic volumes and evolving traffic profiles. Revisiting metro network architecture, optical packet rings with packet optical add and drop multiplexing (POADM) features are proposed in order to support both optical transparency and subwavelength granularity. A medium access control (MAC) structure for multiring POADM networks is proposed, which can support multiprotocol encapsulation and provides the support of differentiated quality of service (QoS) and differentiated protection on a per-flow basis. Unicast and multicast flows are efficiently transported between stations, with a lightweight control within each station. An opportunistic insertion process associated with an appropriate scheduling process is shown to ensure transport network QoS levels. Simple models are provided to assess the transfer performance on the POADM ring. Per-flow protection mechanisms are proposed, and their efficiency is assessed. Dimensioning costs are derived, which take into account the number of used wavelengths and the number of fixed receivers required to support a given traffic matrix. Finally, it is shown that POADM rings can be used to directly support metro Ethernet services and thus allow collapsing the stack of transport network layers.

The Designs of Interconnected Optical Ring Networks

Optical ring networks have been widely implemented as the major metro network architectures. However, as the network coverage expands, the system performance of the single ring structure degrades significantly. In this paper, we propose an interconnected ring topology to enhance the network throughput and efficiency. The carried out simulation results have revealed the superiority of employing such an interconnected architecture. We also discuss the increased complexities and fairness issues induced by such design.

A Multilayer Cost Model for Metro/Core Networks

A capital expenditure model is a key requirement to evaluate multilayer (ML) metro and core network architectures. Based on the Internet protocol/multiprotocol label switching (IP/MPLS), MPLS-transport profile, optical transport network and WDM technology, a detailed capital expenditure model developed by researchers from system vendors and network operators is introduced. Besides current equipment and corresponding prices for the different layers, it also contains predictions for technology evolution and pricing until 2018. We show how to determine the price of an ML node by constructing it from components specified in the cost model. We use the model in a case study where we benchmark the price of an integrated IP/MPLS/WDM solution.

CST: A new contention reduction scheme in all-optical packet switched star-based metro networks

We consider a metro network architecture that consists of a buffer-less all-optical core switch, where a number of edge switches are connected to the core switch. Slotted all-optical packet switching (OPS) is considered for this network in order to efficiently use network bandwidth. A major problem for slotted OPS is contention. However, basic contention resolution schemes such as optical buffers and wavelength converters are expensive. On the other hand, contention reduction techniques can provide a cheap but effective performance in a slotted OPS network. We propose a new slot transmission mechanism as a contention reduction scheme, called Coordinated Slot Transmission (CST), and provide loss rate performance analysis for CST under symmetric and asymmetric traffic arrivals. Under CST, ingress switches (transmitting edge switches) are loosely coordinated to send their traffic and the system is still lossy. We study and analyze the efficiency of the CST scheme when it is used in an OPS network based on star topology with multi-fiber architecture, with additional wavelength channels, and under the combined approach of multi-fiber architecture and additional wavelength channels.

Agile bandwidth management techniques in slotted all-optical packet switched networks

The next generation metro network is most likely to be based on high-capacity agile all-optical networks. We consider a metro network architecture that consists of a number of buffer-less all-optical core switches, where a number of edge switches are connected to each core switch in an overlaid star topology. We would like to design potential candidates of resource-sharing schemes in such a network and evaluate their performances, where they guarantee to deliver optical packets to their destinations. The first scheme is reservation-based, in which decisions are made at each core switch so that collisions (and therefore loss) can be avoided through reservations. For this scheme, we have re-designed the BvN (Birkhoff von Neumann) scheduling algorithm to accommodate the asymmetric multi-fiber/multi-wavelength feature in star OPS. In the second scheme, distributed and independent decisions are made at edge switches, but we need to retransmit the traffic dropped at core switches in the optical domain. We also implement a hybrid case as the third scheme which combines the good attributes of both previous schemes. We have characterized and evaluated the performance of these resource-sharing schemes by various QoS measures such as delay and loss probabilities in edge switches.

Value proposition for amplets as banded amplification solutions in evolving WDM metro network architectures

The benefits of amplets as banded amplification solutions in metro networks are quantified. In current networks that employ WDM as point-to-point fiber relief among pairs of super-hubs in synchronous optical network (SONET) rings, banded solutions based on erbium-doped waveguide amplifiers (EDWAs) provide a strong techno-economic value proposition. As WDM penetrates into the metro core with the introduction of WDM ring/mesh connectivity and eventually into the edge, this specific value proposition weakens. We present a physical transport performance model as well as simplified economic analysis on specific network simulation scenarios that represent the above actual metro network architecture evolution to support the value proposition.

Multiclass Scheduling Algorithms for the DAVID Metro Network

The data and voice integration over dense wavelength-division-multiplexing (DAVID) project proposes a metro network architecture based on several wavelength-division-multiplexing (WDM) rings interconnected via a bufferless optical switch called Hub. The Hub provides a programmable interconnection among rings on the basis of the outcome of a scheduling algorithm. Nodes connected to rings groom traffic from Internet protocol routers and Ethernet switches and share ring resources. In this paper, we address the problem of designing efficient centralized scheduling algorithms for supporting multiclass traffic services in the DAVID metro network. Two traffic classes are considered: a best-effort class, and a high-priority class with bandwidth guarantees. We define the multiclass scheduling problem at the Hub considering two different node architectures: a simpler one that relies on a complete separation between transmission and reception resources (i.e., WDM channels) and a more complex one in which nodes fully share transmission and reception channels using an erasure stage to drop received packets, thereby allowing wavelength reuse. We propose both optimum and heuristic solutions, and evaluate their performance by simulation, showing that heuristic solutions exhibit a behavior very close to the optimum solution.

Performance engineering and topological design of metro WDM optical networks using computer simulation

This paper demonstrates the use of computer simulation for topological design and performance engineering of transparent wavelength-division multiplexing metropolitan-area networks. Engineering of these networks involves the study of various transport-layer impairments such as amplifier noise, component ripple, chirp/dispersion, optical crosstalk, waveform distortion due to filter concatenation, fiber nonlinearities, and polarization effects. A computer simulation methodology composed of three main simulation steps is derived and implemented. This methodology obtains performance estimations by applying efficient wavelength-domain simulations on the entire network topology, followed by time-/frequency-domain simulations on selected paths of the network and finally Q-budgeting on an identified worst case path. The above technique provides an efficient tool for topological design and network performance engineering. Accurate simulation models are presented for each of the performance impairments, and the computer simulation methodology is used for the design and engineering of a number of actual metro network architectures.