Steinar Bjornstad

A packet-switched hybrid optical network with service guarantees

We show that our proposed optical packet switched (OPS) hybrid network model supports both high throughput efficiency and guaranteed service transport (GST) with no packet loss and constant delay. The network comprises a wavelength routed optical network (WRON) enabling GST, and a statistically multiplexed (SM) network enabling high throughput. In the WRON, packets follow a fixed wavelength path and forwarding is based on the packets wavelength, while in the SM network, packets are switched according to header information. High reliability of GST packet forwarding is possible, because the forwarding does not depend on the operation of the packet switch. A novel node design supporting three Quality of Service (QoS) classes is proposed and described in detail. It facilitates full sharing of the link bandwidth by segregating GST packets and SM packets using polarization time division multiplexing (PTDM). SM packets are differentiated into two specified sub-QoS classes employing a novel buffer reservation technique and asynchronous buffer scheduling algorithm AIP3Q. We present a detailed analysis of the node throughput performance, demonstrating that buffering resource requirements are reduced in the optical packet switch, because processing and buffering of GST packets is avoided. The SM packet QoS differentiation permits a further reduction of buffer resources

Quality of service in optical packet switched DWDM transport networks

For support of multimedia applications in Internet, at least four service classes are normally outlined. We expect optical packet switching to be of special interest in terabit capacity networks with a high number of wavelengths. Our analysis shows that when the wavelength dimension is used for contention resolution, and number of wavelengths is 32 or higher, node-delay is negligible. However buffering in optical packet switches is a scarce resource which use should be minimized. Based on the requirement of the future network, and on our packet switch performance analysis, we suggest reducing the number of service classes to two: A normal class (NCT) with medium low packet loss and a low need for buffering, and a high class (HCT) with a minimum of packet loss. Performance of a buffer reservation scheme is analyzed by simulation. Assuming the network of today with 10 % HCT traffic, assigning four buffer inputs to the HCT traffic, a difference in optical packet loss ratio of three orders of magnitude can be obtained. The same difference in optical packet loss ratio can be obtained if 50 % HCT traffic is assumed (network of tomorrow), by assigning a higher number of buffer inputs.

Research in optical burst switching within the e-Photon/ONe network of excellence

This paper presents a summary of Optical Burst Switching (OBS) research within the VI framework program e-Photon/ONe network of excellence. The paper includes network aspects such as routing techniques, resilience and contention resolution, together with burst switch architectures. On the other hand, we also discuss traffic analysis issues, Quality of Service (QoS) schemes, TCP/IP over OBS and physical layer aspects for OBS.

Scalability analysis of SDN-controlled optical ring MAN with hybrid traffic

The development of software defined networking (SDN) has instigated a growing number of experimental studies which demonstrate the flexibility in network control and management introduced by this technique. Optical networks add new challenges for network designers and operators to successfully dimension and deploy an SDN-based in the optical domain. At present, few performance evaluations and scalability studies that consider the high-bandwidth of the optical domain and the flow characterization from current Internet statistics have been developed. In this paper these parameters are taken as key inputs to study SDN scalability in the optical domain. As a relevant example an optical ring Metropolitan Area Network (MAN) is analyzed with circuit and packet traffic integrated at the wavelength level. The numerical results characterize the limitations in network dimensioning when considering an SDN controller implementation in the presence of different flow mixes. Employing flow aggregation and/or parallel distributed controllers is outlined as potential solution to achieve SDN network scalability.

Optical burst and packet switching: node and network design, contention resolution and quality of service

Future network should be able to efficiently serve packet-based networks, such as the Internet. In this paper, based on results from COST 266, we explore characteristics of optical burst switching (OBS) and optical packet switching (OPS). Both node design and metropolitan area network (MAN) are discussed. A unique joint comparative performance evaluation of contention resolution in OBS and OPS are presented, as well as methods of quality of service (QoS) differentiation in OBS/OPS networks, and their performance.

Reservation techniques in an OpMiGua node

An OpMiGua node integrates a packet switch for low priority traffic and a circuit switch for high priority traffic. Both traffic classes share the same input and output ports using time division multiplexing, but absolute priority is given to circuit switched packets. The circuit switched packets do not experience contention at output ports and are not subject to delay jitter; hence a guaranteed service class is created. Previous studies of OpMiGua nodes have used one of two reservation techniques to assure priority; either a time-window approach or a preemptive approach. This article introduces two new reservation techniques and investigates advantages and drawbacks associated with the four techniques. It is shown that each reservation technique is associated with specific loss mechanisms and methods to reduce their influence are proposed. Simulation results demonstrate that the choice of reservation technique is highly influenced by the relative share and length of high priority packets.

OpMiGua Hybrid Circuit- and Packet-Switched Test-Bed Demonstration and Performance

Hybrid optical network architectures that combine beneficial properties of circuit- and packet-switching are attractive for multimedia networks. We have already proposed and reported the experimental demonstration of elements of a hybrid optical network architecture, the OpMiGua network. We now report experimental characterization of a three-node OpMiGua network test-bed with ingress, core, and egress nodes. The experiment confirms zero packet loss and jitter of the circuit-switched guaranteed service transport class of service (CoS) and shows how adding a packet-switched statistical multiplexed CoS increases lightpath utilization

Quality of service differentiation in optical packet/burst switching: a performance and reliability perspective

This article addresses the broad definition of quality of service (QoS) in optical packet/burst switched (OPS/OBS) networks. First we identify the QoS concept, we then provide an overview of existing service differentiation techniques available for OPS/OBS. We include both performance and dependability, and discuss how OBS/OPS networks can be implemented taking both parameters into consideration. Specific reliability issues in OPS/OBS networks are identified, and the function of performance differentiation techniques is evaluated in light of reliability and differentiation of reliability.

Time interleaved polarization multiplexing for polarization labelling

We investigate the use of polarization for labelling in optical networks and demonstrate experimentally that an interleaved polarization multiplexing technique is significantly more robust than traditional polarization multiplexing in the presence of random polarization variations. This time interleaved polarization multiplexing scheme does not suffer from the coherent crosstalk inherent to traditional polarization multiplexing. Channel identification and automatic polarization control is achieved using a pilot tone technique.

A Cross Layer Study of Packet Loss in All-Optical Networks

A crucial issue in all-optical networks is packet loss. In this paper we evaluate sources of packet loss, comparing impact of effects at the physical layer and at the network layer. The study is compiled for optical packet, burst and circuit switched networks. We provide an analytical model that evaluates packet loss due to bit errors using bit-error rate, packet length distribution and network size as parameters. Bit errors at the physical layer set a lower limit to the aggregate packet loss and for some scenarios it overshadows packet loss at the network layer. For applications applied in the Internet today, bit error requirements may be considerably alleviated as compared to those of synchronous digital hierarchy (SDH) systems without degrading the perceived quality of service for the end-user. By considering recommended packet loss rates for future Internet services we evaluate the usefulness of different techniques for reduced packet loss.