H.R. van As

Efficient QoS support in a slotted multihop WDM metro ring

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.

Service-specific resource allocation in WDM networks with quality constraints

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.

QoS support and fairness control in a slotted packet-switched WDM metro ring network

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.

Handover management in low Earth orbit satellite IP networks

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.

Service-specific wavelength allocation in QoS-routed optical networks

In this paper, quality-of-service (QoS) routing and service-specific functions in optical networks are proposed. We first present two QoS-routing algorithms, which differ in the way of handling quality attributes like transmission performance, blocking probability and cost. We furthermore propose a new wavelength allocation scheme, called least quality allocation. Particular functions like service-specific wavelength shifting, variable link costs or limited path length per service are studied in more detail. This is studied by numerical examples of optical networks in meshed topologies with different services and traffic conditions. The benefit of this approach is that many corporate optical networks with different QoS-requirements can be simultaneously accommodated.

QoS-restorability in optical networks

We introduce quality of service (QoS) restorability in optical networks as a performance measure for service-specific restoration methods applied to wavelength connections. Various scenarios of QoS-degradations, affecting one or more wavelength paths, are numerically investigated for a multi-service network example.

An approach to QoS-based routing for LEO satellite networks

We propose a routing methodology for multi-hop LEO satellite networks aiming at minimising the number of link handovers per connection, while at the same time satisfying the QoS requirements. For the representation of the network topology, a graph-theoretical approach is used, where a new metric for inter-satellite links, called lifetime t/sub L/, is introduced. This metric is then considered for the minimisation of connection re-routing attempts due to the connectivity changes, for which a network graph transformation approach is proposed. In addition to this, we propose a distributed QoS routing strategy for LEO satellite networks, where the accommodation of different QoS requirements such as bandwidth or delay presume the maximisation of the lifetime of inter-satellite links (ISL), building a feasible path.

Time for a change in electronic and photonic switching

To take part of next generation networks it seems that it is blindly taken for granted that per default all data must be packetized, and thus even traditional voice connections are handled as emulated circuit-switched connections, with all the control difficulties and delay degradation characteristics. This is a serious step back in performance quality. It has generally been recognized that communication delay is the most difficult parameter to keep under control. The main reasons for all-packetized networks originally were communication flexibility and improved resource utilization for bursty traffic flows. However, with increasing peer-to-peer multimedia communications the target of pursuing pure all-packetized switching networks, starts to show major drawbacks. For example, each small packet of a long-living video stream must individually be inspected, scheduled, and forwarded. In fact, this causes a large amount of processing and consumes much power for processing and cooling. It is time to change that. This paper introduces FTM (Flow transfer mode), which is a universal switching method. It is a highly dynamic layer-1 switching technology with layer-2 or layer-3 control for scheduling long-living continuous or periodic interleaved streaming data flows as well as short flows consisting of a single packet or a burst of aggregated packets to the same network destination. Each flow is triggered by a preceding control unit that is transmitted in due time in advance. Thus, it can be regarded as a generalization of optical burst switching.

Performance analysis of distributed location management for wireless networks

Location management is an essential process in future mobile communication networks. An important issue is that of efficient management of the location database. The next generation mobile communication network is proposed to integrate with a TINA-compliant architecture enabling one to handle that kind of mobile-specific processes. This paper discusses the design and modeling of a distributed location management based on a TINA-compliant architecture for wireless mobile communication networks. We consider a distributed location database architecture for location management, performing two strategies: HLD (home location database) and HLD-CLD (HLD with a cache location database). The local cache CLD is used to reduce signaling traffic in the network and to accelerate database searching and updating. This paper also presents a simple methodology for evaluating some basic location management algorithms for a distributed location database based on a TINA-compliant architecture for wireless communication networks.

Resource allocation strategies with QoS-routing in optical networks

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.