Optical Packet Switching Networks Research Articles

Performance of Fixed-Length, Variable-Capacity Packets in Optical Packet-Switching Networks

We present the performance of fixed-length, variable-capacity (FL-VC) packets in optical packet-switching (OPS) networks. We show how FL-VC achieves an effective balance between implementation feasibility and performance of the applications using the network. Focusing on metropolitan area networks and real-world file distributions, we also show that an adequate selection of packet duration leads to nearly optimal application throughput with respect to conventional variable-length, fixed-bit-rate packets (VL-FBR), and that this optimal packet duration is robust against changes in the workload. Finally, we show that a single fiber delay line per OPS switch managed by a first-fit scheduler can increase throughput to levels similar to those obtained by random access buffers.

Dispersion of double-slot microring resonators in optical buffer

In the optical packet switching network, optical buffer is an important device. Microring resonator optical buffers provide good delay performance and flexibility in design. By cascading multiple microring resonators, higher delay-bandwidth product is obtained, but the requirements of high integration and low dispersion are hard to satisfy simultaneously. Double-slot waveguide was proposed to construct highly integrated racetrack microring resonators in this study. Based on dispersion analysis of the thickness of each layer of a waveguide, the structure of waveguide was optimized to reach flat and low dispersion. Average dispersions of straight and 3 μm bend waveguides were 5.1 ps/(nm∙km) and 4.4 ps/(nm∙km), respectively. Besides, the additional loss from coupling was greatly reduced when applying proper relative displacement between straight and bend waveguides. Theoretical and design basis provided in this paper will help to develop multi-microring optical buffers in the future.

Torus-Topology Data Center Network Based on Optical Packet/Agile Circuit Switching with Intelligent Flow Management

We review our work on an intra-data center (DC) network based on co-deployment of optical packet switching (OPS) and optical circuit switching (OCS), conducted within the framework of a five-year-long national R&D program in Japan (∼March 2016). For the starter, preceding works relevant to optical switching technologies in intra-DC networks are briefly reviewed. Next, we present the architecture of our torus-topology OPS and agile OCS intra-DC network, together with a new flow management concept, where instantaneous optical path on-demand, so-called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Express Path</i> is established. Then, our hybrid optoelectronic packet router (HOPR), which handles 100 Gbps (25 Gbps × 4-wavelength) optical packets and its enabling device and sub-system technologies are presented. The HOPR aims at a high energy-efficiency of 0.09 [W/Gbps] and low-latency of 100 ns regime. Next, we provide the contention resolution strategies in the OPS and agile OCS network and present the performance analysis with the simulation results. It is followed by the discussions on the power consumption of intra-DC networks. We compare the power consumption and the throughput of a conventional fat-tree topology with the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -dimensional torus topology. Finally, for further power saving, we propose a new scheme, which shuts off HOPR buffers according to the server operation status.

Dynamic Openflow-Controlled Optical Packet Switching Network

This paper presents and experimentally demonstrates the generalized architecture of Openflow-controlled optical packet switching (OPS) network. Openflow control is enabled by introducing the Openflow/OPS agent into the OPS network, which realizes the Openflow protocol translation and message exchange between the Openflow control plane and the underlying OPS nodes. With software-defined networking (SDN) and Openflow technique, the complex control functions of the conventional OPS network can be offloaded into a centralized and flexible control plane, while promoted control and operations can be provided due to centralized coordination of network resources. Furthermore, a contention-aware routing/rerouting strategy as well as a fast network adjustment mechanism is proposed and demonstrated for the first time as advanced Openflow control to route traffic and handle the network dynamics. With centralized SDN/Openflow control, the OPS network has the potential to have better resource utilization and enhanced network resilience at lower cost and less node complexity. Our work will accelerate the development of both OPS and SDN evolution.

BHP flooding vulnerability and countermeasure

Optical burst switching (OBS) is a switching technology that can efficiently operate in the optical core network using WDM technology and can also develop the future optical internet. The OBS switching technology presents a trade-off between the two switching technologies: optical circuit switching (OCS) and optical packet switching (OPS). This switching approach increases resource utilization compared with OCS technology and avoids the technological barriers of OPS networks. In OBS networks, many packets are assembled into one data burst at the edge node and a burst header packet (BHP) is sent before the burst transmission by an offset time in order to reserve the required resources in core nodes. This can cause security issues in the network and more specifically denial of service attacks that can occur if a source node is compromised. In this paper, we study a specific denial of service attack which we refer to as "BHP flooding attack", which prevents legitimate traffics from reserving the required resources at intermediate core nodes. We also propose the design of a reconfigurable BHP flooding countermeasure module that allows to counter against this type of attacks in an OBS network.

Dynamic Multi-Domain Virtual Optical Network Deployment With Heterogeneous Control Domains [Invited

We propose a multi-domain resource broker to dynamically provision multi-domain virtual optical networks across heterogeneous control domains (i.e., GMPLS and OpenFlow) and transport (i.e., optical packet switching and elastic optical networks) technologies. We have designed, implemented, and experimentally evaluated the multi-domain resource broker in an international testbed across Spain, the UK, and Japan.

SDN-Based Network Orchestration of Variable-Capacity Optical Packet Switching Network Over Programmable Flexi-Grid Elastic Optical Path Network

A multidomain and multitechnology optical network orchestration is demonstrated in an international testbed located in Japan, the U.K., and Spain. The application-based network operations architecture is proposed as a carrier software-defined network solution for provisioning end-to-end optical transport services through a multidomain multitechnology network scenario, consisting of a 46-108 Gb/s variable-capacity OpenFlow-capable optical packet switching network and a programmable, flexi-grid elastic optical path network.

Pilot-Tone-Aided Transmission of High-Order QAM for Optical Packet Switched Networks

We investigate novel pilot-aided transmission of high-order quadrature amplitude modulation (QAM) modulation formats for optical packet-switched networks. The proposed modulation scheme employs a pilot tone operating at the baud rate for noncoherent reception that is highly immune to laser phase noise. The results show that the system performance equivalent to static operation is achieved 5&#xA0;ns after wavelength switching of a sampled grating distributed Bragg reflector (SG-DBR) tunable laser.

Tunable optical code converter using XPM and linear-slope pulse streams generated by FBGs

We propose for the first time (to the best of our knowledge) and demonstrate a tunable multiple optical code (OC) converter for flexible networks that allows dynamic code (bandwidth) allocation in a way similar to a tunable laser. With respect to other OC converters, this scheme can convert both specific and multiple OCs by changing only the amplifier gain. The proposed scheme uses cross-phase modulation (XPM) and two linear-slope control pulse streams generated by fiber Bragg gratings (FBGs) in the C-band. The OC converter can be used to avoid collisions in optical packet switching networks, and we analyze the corresponding packet loss probability performance.

Linear random code-based label encoding scheme for label swapping free optical packet switching networks

Optical Label Switching (OLS) has been considered to be a promising approach to realize optical packet switching (OPS) networks. In an OLS router, the header processing module retrieves the routing information carried in the optical header and then replaces the old header with a new one through optical label swapping. The cost-effectiveness and the speed of performing label swapping are two major concerns. Due to lack of optical random access memory, optical label swapping has become a big challenging issue in implementing OLS switches. To overcome these difficulties, in this paper, we propose two Linear Random Code (LRC)-based label encoding schemes to achieve label swapping free OPS networks. Using the proposed schemes, a small sized label is needed. Only simple modulo-2 multiplication and modulo-2 addition operations are required to decode an optical label and there is no optical label swapping during packets traverse along the entire routing path. In our system, each source–destination pair is assigned multiple paths so the network is with traffic engineering and fault tolerance capabilities. We have carried out extensive simulations to evaluate the performance of the proposed scheme. Compared with the well-known KIS encoding scheme, the proposed LRC-based scheme can reduce the label size significantly. An 8-byte LRC label is long enough to support all node pair with five paths in a 300-node network.

On the fly all-optical packet switching based on hybrid WDM/OCDMA labeling scheme

We introduce a novel design of an all-optical packet routing node that allows for the selection and forwarding of optical packets based on the routing information contained in hybrid wavelength division multiplexing/optical code division multiple access (WDM/OCDMA) labels. A stripping paradigm of optical code-label is adopted. The router is built around an optical-code gate that consists in an optical flip–flop controlled by two fiber Bragg grating correlators and is combined with a Mach–Zehnder interferometer (MZI)-based forwarding gate. We experimentally verify the proof-of-principle operation of the proposed self-routing node under NRZ and OCDMA packet traffic conditions. The successful switching of elastic NRZ payload at 40Gb/s controlled by DS-OCDMA coded labels and the forwarding operation of encoded data using EQC codes are presented. Proper auto-correlation functions are obtained with higher than 8.1dB contrast ratio, suitable to efficiently trigger the latching device with a contrast ratio of 11.6dB and switching times below 3.8ns. Error-free operation is achieved with 1.5dB penalty for 40Gb/s NRZ data and with 2.1dB penalty for DS-OCDMA packets. The scheme can further be applied to large-scale optical packet switching networks by exploiting efficient optical coders allocated at different WDM channels.

Toward Wireless Backhaul Using Circuit Emulation Over Optical Packet-Switched Metro WDM Ring Network

Optical WDM metro-ring networks have been considered to be promising solutions for wireless backhaul. In this paper, we propose an integrated traffic control scheme (ITCS), which facilitates circuit emulation service (CES) for wireless backhaul over a previously proposed experimental optical packet-switched WDM metro-ring network, HOPSMAN. The ITCS seamlessly integrates variable-bit-rate (VBR) CES wireless with connection-less best-effort data, satisfying stringent QoS requirements and retaining maximal network throughput. The ITCS ensures efficient setup of CES connections by employing a simple mean-rate-based distributed admission control followed by a novel slot-marking reservation. The total connection setup delay is comprised of the setup queueing delay and slot-marking delay. While the slot-marking delay is nearly a ring time, the mean setup queueing delay is formally computed through an accurate approximation based on an M/G/m queueing analysis. We show simulation results to demonstrate that the ITCS accommodates remarkably high CES traffic loads while satisfying a wide range of delay requirements for wireless backhaul. Taking the background best-effort traffic into account, ITCS achieves exceedingly low delay, jitter, and delay bound for CES under various traffic loads and burstiness.

Novel FWM-Based Spectral Amplitude Code Label Recognition for Optical Packet-Switched Networks

We propose and demonstrate a novel architecture for four-wave mixing (FWM)-based recognition of spectral amplitude code (SAC) labels in optical packet-switched networks. With a proper code design, a unique FWM idler for each SAC label, referred to as a label identifier (LI), is generated in a nonlinear medium. A serial array of fiber Bragg gratings is then used to reflect the LI wavelengths. Each LI is associated with a unique amount of delay between two optical signals received at two photodiodes (PDs). Label recognition is then achieved by measuring this unique time delay (referred to as the characteristic delay). The main advantages of the proposed method include the following: no serial-to-parallel conversion is required, simple label extraction is achieved, variable-length packets are supported, and the number of PDs used in the label recognition module is reduced. Moreover, the LI wavelengths do not need to exhibit any periodicity or match a particular wavelength grid; this results in a less challenging code design with smaller spectral occupancy for label generation. An experiment is conducted, where two variable-length data packets are transmitted over a 50-km dispersion-compensated span and switched at a forwarding node. The SAC labels are successfully recognized, and we obtain error-free transmission for the switched packets with less than 0.3-dB penalty.

High-performance implementation of in-network traffic pacing for small-buffer networks

Demands on data communication networks continue to drive the need for increasingly faster link speeds. Optical packet switching networks promise to provide data rates that are sufficiently high to satisfy the needs of the future Internet core network. However, a key technological problem with optical packet switching is the very small size of packet buffers that can be implemented in the optical domain. Existing protocols, for example the widely used Transmission Control Protocol (TCP), do not perform well in such small-buffer networks. To address this problem, we have proposed techniques for actively pacing traffic at edge networks to ensure that traffic bursts are reduced or eliminated and thus do not cause packet losses in routers with small buffers. We have also shown that this traffic pacing can improve the performance of conventional networks that use small buffers (e.g., to reduce the cost of buffer memory on routers). A key challenge in this context is to develop systems that can perform such packet pacing efficiently and at high data rates. In this paper, we present the design and prototype of a hardware implementation of our packet pacing technique. We discuss and evaluate design trade-offs and present performance results from an prototype implementation based on a NetFPGA fieldprogrammable gate array system. Our results show that traffic pacing can be implemented with few hardware resources and without reducing system throughput. Therefore, we believe that traffic pacing can be deployed widely to improve the operation of current and future networks.

Optical Interconnection Bidirectional Data Vortex Network: Architecture and Performance Analysis

Data Vortex architecture is a unidirectional, highly scalable, all optical multistage interconnection packet switching network. In the present paper we propose Data Vortex architecture with bidirectional links in which the packets are routed both in the forward as well as in the reverse directions. The feasibility of data flow in both the directions is simulated in C environment. The performance analysis of bidirectional network is carried out and presented in terms of injection rate, latency and latency distribution. Finally, the comparison of the proposed bidirectional architecture with two Data Vortex networks connected in parallel for bidirectional operation is also presented.

Optical Physical-Layer Network Coding

The application of physical-layer network coding (PNC) in optical communications is explored. We propose and demonstrate a practical optical PNC prototype for multicast protection in optical flow, burst, and packet switching networks. Different from conventional theoretical PNC studies, our proposed optical PNC system does not require bit synchronization and can be easily implemented.

A Path Tracing Scheme for All-Optical Packet-Switched Networks

A novel optical scheme is proposed to perform path tracing in an all-optical packet-switched network. Prime-number-encoded tag is employed as the distinct network node or network link identifier. As the optical data packet traverses every network node, the path trace is recorded and updated optically, through prime number multiplication via an optical delay circuit encoder. Hence, all traversed network nodes along the path of a received optical data packet can be retrieved and identified at the destination node, via simple prime number factorization. Possible looping of optical data packets in the network can also be detected. The scheme can facilitate the connection management in an optical packet-switched network.

PTES: A New Packet Transmission Technique in Bufferless Slotted OPS Networks

Optical packet contention is the major problem in optical packet switching (OPS) networks. In this paper, a software-based contention reduction scheme is proposed for all-optical multi-fiber slotted OPS networks, called packet transmission based on the scheduling of empty time-slots (PTES), suitable for overlaid star topology used in a metropolitan area with heterogeneous distances. In the scheduling procedure (performed in a distributed manner by each edge node of a star network) within a frame interval, some time-slots are scheduled as empty time-slots and the remaining time-slots are scheduled as non-empty. Then, an edge node must avoid sending its traffic in empty time-slots. Instead, non-empty time-slots can be used for traffic transmission. With respect to this scheduling, the variance of the number of non-empty time-slots that carry traffic from all edge nodes is minimized in the core node at each time-slot, thus reducing the traffic loss. Mathematical formulas are also provided to compute the traffic loss and delay under PTES. Performance evaluation results illustrate that PTES can reduce the number of collision events and traffic loss, especially at light and moderate traffic loads.

Analysis of optical packet loss rate under asymmetric traffic distribution in multi-fiber synchronous OPS switches

In this article, optical packet loss rate (PLR) is analyzed for an all-optical buffer-less OPS (optical packet switched) switch located in a multi-fiber OPS network, where the multifiber OPS (MOPS) switch uses only shared-per-link wavelength converters for contention resolution purposes. The analysis is provided to compute PLR under asymmetric traffic.

All‐optical multi‐wavelength header recognition using superimposed Bragg gratings based correlators

SUMMARYWe have demonstrated that an optical correlator, based on superimposed Bragg gratings, can be used as all‐optical multi‐wavelength header recognition in optical packet switching networks. The proposed correlator is composed of two superimposed gratings in conjunction with variable delay lines. These superimposed Bragg gratings are used to demultiplex and multiplex the wavelength components of multi‐wavelength header bit patterns. The variable delay lines create a wavelength profile that can be matched with any arbitrary bit patterns. Simulation results for all optical recognition of four‐bit patterns at 10 Gbps are reported. The results show that when the header bit pattern matches the wavelength profile of the correlator, the generated auto‐correlation function will include a high amplitude peak; otherwise, a cross‐correlation function with low amplitude peaks will be generated in the output of the correlator. Considering this idea, multi‐wavelength header is recognized by using all‐optical processing method. Copyright © 2012 John Wiley &amp; Sons, Ltd.