In optical burst-switched (OBS) networks, packets are aggregated into bursts that are sent an offset time after the corresponding control packet. The process of aggregating high and low-priority traffic in the same burst is known as composite burst assembly, where high-priority and low-priority packets are placed at the head and the tail end of the burst, respectively. Such composite bursts are beneficial in order to resolve the contention by dropping low-priority packets when preemptive minimum overlap channel (P-MOC) scheduling algorithms are used. For non-preemptive minimum overlap channel with void-filling (NP-MOC-VF) scheduling algorithm, we propose that high-priority packets should be placed in the middle of a burst and low-priority packets at the head and tail ends of a burst. That allows dropping of low-priority packets from the head and the tail of a burst when it contends with two other bursts where the head of the burst contends with one burst and the tail contends with another. The simulation results show that high-priority traffic faces reduced loss at the cost of increased loss of low-priority traffic. In this paper, the effect of varying the proportion of high-priority packets in the middle of the burst has been studied.

The delivery of fast, reliable, and differentiated services with a guaranteed performance level for a constantly increasing number of customers is a great challenge of Internet service providers. This can be made by efficient management of network resources, for which service level agreements (SLAs) are used. This paper presents a framework for dynamic management of SLAs in MPLS networks. In our framework, it is the ingress router of the MPLS backbone, which performs admission control as well as the path selection procedure. For path computation, different advanced routing algorithms are used. The behavior and the performance of these routing algorithms affect the number of users that can be served simultaneously, while delivering a proper performance level, which is agreed in SLA. Therefore, SLA fulfillment is impacted by proper selection of the routing algorithm. In our research we have expatriated the performance and behavior of three routing algorithms for MPLS networks. In order to provide a reality-similar, heterogenous traffic situation, a model with three different traffic classes is used. By means of network simulations, we base our investigation on these SLA parameters: average end-to-end delay, average throughput, average packet dropping probability, average link load and number of utilized links.

In this paper we present a framework for dynamic management of service level agreements (SLAs) in MPLS networks. In our framework it is the ingress router of the MPLS backbone, which performs admission control and the path selection procedure. For path selection, different advanced routing algorithms affect the number of users that can be simultaneously served, while delivering a proper performance level, which is agreed in SLA. Therefore, SLA fulfillment is impacted by proper choice of the routing algorithm. In our research we have used three routing algorithms. By means of extensive simulations, we based our investigation of four SLA parameters: average end-to-end delay, average throughput, average link load, and average packet dropping probability.

A novel distributed access protocol for a slotted wavelength-division-multiplexing (WDM) metro ring employing all-optical packet switching and supporting quality-of-service (QoS) classes is presented and analyzed. Since we assume that there are more nodes than available wavelengths in the network, we obtain a scalable multihop WDM ring as underlying network architecture. By dividing each channel into several time slots and further applying destination release and slot reuse, data packets can be efficiently transmitted and received in a statistically multiplexed manner. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider so-called a posteriori access strategies, different packet selection schemes are proposed and compared. An analytical model based on the semi-Markov process methodology is developed to quantify the performance of one of these schemes. As a key element of the protocol, an efficient QoS support access mechanism is proposed and its performance is evaluated. The new QoS control scheme adopts a frame-based slot reservation strategy including connection setup and termination, which only slightly increases the signaling and node processing overhead. Thus, an efficient hybrid protocol combining connectionless and connection-oriented packet transmissions is proposed.

In this paper, a novel distributed medium access protocol for a time-slotted WDM metro ring employing all-optical packet switching and supporting QoS classes directly in the optical layer is presented and analyzed. Since we assume much more nodes than available wavelengths in the network, we obtain a scalable multi-hop WDM ring. In our architecture, each node is equipped with one tunable: transmitter and one fixed-tuned receiver. The new QoS control scheme adopts a frame-based slot reservation strategy including connection set-up and release, thus efficiently combining connection-less and connection-oriented services. Furthermore, a fairness control scheme, named M(ultiple)-ATMR, guaranteeing fairness for best-effort traffic through a credit-based mechanism is proposed.

In the paper, we investigate issues of Internet-based services provisioned via low earth orbit (LEO) satellite-IP networks, which are equipped with on-board IP routers. We propose a possible network-integrating architecture for global personal communication based on IP (Internet protocol) networks. We investigate particularly challenges of handover management in LEO satellite networks, arising due, to the movement of the satellites. Handover management schemes based on mobile IPv6 are proposed for handling inter-satellite handover. Performance evaluations of the proposed schemes are carried out by means of simulation.

This paper proposes a new medium access control (MAC) protocol named CONRAD (CONvergence of Real-time And Data services) for a passive-star based single-hop WDM local lightwave network which efficiently supports services with tight delay constraints, i.e. real-time traffic, and best-effort services, i.e. data traffic, directly in the optical layer. The integration of both service types in a packet-switched environment is primarily achieved by combining two different reservation schemes on the control channel, instead of applying conventional priority strategies or circuit-switched approaches. Thereby, a significant improvement of the access delay balance between real-time and data transmission may be obtained, while the system achieves high throughputs.

The need to establish wavelength-routed connections in a service-differentiated fashion is becoming increasingly important due to a variety of candidate client networks (e.g., IP, SDH, ATM) and the requirements for QoS-delivery within transport layers. The multiservice operation changes the way we deal with wavelength-routed paths, as they are now being characterized by manifold properties, such as transmission quality, restoration, network management, and policies. We propose a generic approach to service-differentiated connection accommodation in wavelength-routed networks where, for the network state representation, the supplementary network graphs are defined and referred to as service-specific wavelength-resource graphs. These graphs are used for the appropriate allocation of wavelengths on concatenated physical resources building a wavelength route, along which the necessary transmission quality is achieved and the required management and surveillance functions are provided. By considering twofold wavelength routing metrics, i.e., QoS metrics (service requirements) and resource metrics (quality constraints), these graphs can yield the solution to the QoS-routing problem, i.e., the provision of service-specific guarantees under quality constraints-a feature that is still missing from the existing architectures. The numerical analysis of dynamically reconfigurable multiservice WDM networks is presented for regular network operation as well as for optical network service restoration.

In this paper, resource allocation strategies in QoS-routed optical networks are proposed. We particularly focus on one QoS-routing approach, where various quality attributes, like transmission performance or blocking probability, directly influence the cost functions of the so-called transformed network graph. In this graph, the new nodes are derived from the network elements relevant to the decisions on quality for a certain user. The costs for the graph edges are compound functions of that quality and the particular resource allocation strategy, like least-quality resource allocation, wavelength shifting minimisation, or alternate routing for multi-wavelength network resources. Numerical results for multi-service optical networks have shown that the QoS-based resource allocation can simultaneously accommodate particular user requirements, blocking probability and traffic dynamics.

In applied queueing theory, it is often important to deal with transient system behavior. Performance evaluation of congestioncontrol mechanisms in a packet-switching network is an excellent example in which there is frequently a strong need to deal with the intrinsic dynamic character of congestion. In that case, the queueing models have to be analyzed for a transient environment. In this paper, we show that such problems can be treated in a uniform way, when the system of coupled differential equations describing the system-state or flow process is solved numerically. For this, the fourth-order RungeKutta procedure allows a good balance between memory requirements, computing time, and accuracy. To illustrate the explanatory power of this kind of transient queueing analysis, three models will be considered: the common-store queueing system showing the priority deadlock, the foreground-background congestion-control mechanism, and a two-level global congestion-control mechanism.