Security issues in all-optical networks

All-optical networks are emerging as a promising technology for terabit per second class communications. However, they are intrinsically different from electro-optical networks, particularly because they do not regenerate signals in the network. The characteristics of all-optical network components and architectures manifest new and still unstudied security vulnerabilities but also offer a new array of possible countermeasures. We focus on two types of attacks on the physical security of the network: service disruption, which prevents communication or degrades quality of service (QoS), and tapping, which compromises privacy by providing unauthorized users access to data which may be used for eavesdropping or traffic analysis     

Security issues of wireless sensor networks in healthcare applications

The emergence of wireless sensor networks (WSNs) in healthcare applications is gaining momentum through the increasing array of wearable vital sign sensors and location tags which can track both healthcare personnel and patient status/ location continuously in real-time mode. Despite the increased range of potential application frameworks — ranging from pre-hospital, in-hospital, ambulatory and home monitoring, to long-term database collection for longitudinal trend analysis — the security gap between existing WSN designs and the requirements of medical applications remains unresolved. Generally, WSN devices are extremely limited in terms of power, computation, and communication. They are often deployed in accessible areas, thus increasing security vulnerabilities. The dynamic ad hoc topology, multicast transmission, location awareness, critical data prioritisation, and co-ordination of diverse sensors of healthcare applications further exacerbate the security challenges. This paper presents an analysis of various WSN security mechanisms from the demanding perspective of healthcare applications, and considers the importance of security to the successful deployment of pervasive computing solutions in the healthcare industry.     

Critical issues of onboard switching in DVB-S/RCS broadband satellite networks

The next generation of broadband satellite networks is challenged to accommodate multimedia services while concurrently integrating with terrestrial IP networks. With IP applications dominating the Internet, carrying IP traffic over the satellite has been under intensive study. Originally developed to bring digital television home through satellites, the DVB-S and DVB-RCS standards empower interactive satellite communications with economical standardized satellite terminals. Furthermore, onboard switching technology is increasingly gaining attention, due to optimized bandwidth usage, fully meshed network topology through one satellite hop, and quality of service guarantee. This article investigates the onboard switching technologies in DVB-S/DVB-RCS broadband satellite networks. Aside from the network system infrastructure and switch hardware architecture, the QoS mechanisms supported by the switch onboard the satellite are discussed in depth.     

Innovative hybrid optical/digital ultra-fast packet-switched processor for meshed satellite networks

This paper describes the architectural study of an innovative ultra-fast packet-switched transparent processor dealing efficiently with unicast and multicast applications. The proposed architecture aims at outperforming current packet processor architectures in terms of total throughput and efficiency. In order to cope with the limitations of today's on board processors, three new concepts are introduced: transparent burst switching, channel multiplexing, and bandwidth asymmetry . Some of these concepts are already well known in the field of optical terrestrial networks but need further improvements and adaptations to cope with the requirements of satellite processors and systems. Transparent burst switching is used to enhance the transparency of the processor: the packet payload is processed transparently and only the header is demodulated onboard. The channel multiplexing and bandwidth asymmetry techniques are used to consolidate bufferless switch architectures, which appear to be very attractive for increasing the overall throughput of switches. Finally, the paper introduces an innovative efficient and scalable hybrid optical/digital implementation of this processor. The focus here is on a satellite-switched code/time-division multiple-access type of system but the results and concepts provided in this paper can apply to other satellite-switched systems.     

Optical satellite networks

Several nongeosynchronous satellite constellation networks providing broad-band access to end-users are currently under development. The use of multigigabit laser intersatellite links (ISLs) is the enabling factor for routing traffic through the spare segment and creating a global space-based optical backbone network. Optical networking techniques based on wavelength division multiplexing (WDM) ISLs and wavelength routing can allow by-pass of the transit traffic significantly simplifying routing decisions and minimizing processing delays. The paper examines the characteristics of these networks and investigates the applicability of various optical networking schemes based on single hop and multihop approaches. Single hop can be adopted in medium earth orbit (MEO) systems consisting of 10 to 15 satellites whereas double-hop schemes based on the matrix lightpath allocation approach are suited for constellations up to 100 satellites, covering the requirements of most of the proposed low earth orbit (LEO) systems. Multihop will be required for some of the very large in number of satellites constellations. Statistical multiplexing of the transported traffic over the ISLs appears to be a necessary condition to achieve an efficient utilization of the satellite resources. Traffic routing has to take into account the impact of the varying range of the interorbit ISLs on the propagation delays. Although maximum leverage of the technologies developed for fiber optic WDM networks should be made, the technologies to be employed on board the satellites have to be space-qualified that may limit the applicability of some otherwise high-efficiency components     

Optical networks with hybrid routing

All-optical switching or wavelength routing has the benefit of optical bypass that can eliminate expensive high-speed electronic processing at intermediate nodes and reduce significantly the cost of high-bandwidth transport. But all-optical switching has the limitations of coarse granularity, lack of multiplexing gain, and scarcity of wavelength resources, which do not mesh well with Internet traffic that has many small and diverse flows and emphasizes the importance of resource sharing. In particular, wavelength routed light paths have difficulty to seamlessly converge with multiprotocol label switching label-switched paths that have arbitrary bandwidth granularity and relatively abundant labels. In this paper, we propose a hybrid wavelength and subwavelength routing scheme that can preserve the benefits of optical bypass for large traffic flows at the same time provide multiplexing gain for small traffic flows. We first study the hybrid routing scheme using static optimization that produces an optimal path set and a partition between wavelength and subwavelength routing. We then present a dynamic heuristic that tracks the static optimization closely. During the process, we proposed a traffic arrival process called incremental arrival with sporadic random termination to more accurately model practical optical network traffic generation process.     

Digital satellite networks in Europe

Developments of digital satellite networks are progressing in Europe at international as well as national levels. EUTELSAT and its signatories are actively setting up two regional networks based on the ECS satellites built by ESA. One will carry large bundles of telephone circuits between national gateways; the other will provide special services to corporate organizations and businesses. On the other hand, several countries are implementing or planning their own national networks, all for small-station services. These are France with Telecom 1, Sweden with TELE-X, Norway with NORSAT II, Italy with ITALSAT, the Federal Republic of Germany with DFS/Copernicus, and the United Kingdom with UNISAT. These projects are described here and their characteristics compared. The paper brings out the great diversity in the approaches, as illustrated by Telecom 1 where the accent is on the development of an ISDN, TELE-X where it is on the low cost of user stations, and ITALSAT on the flexibility of the network.     

Modeling and analysis of TCP-like multicast congestion control in hybrid terrestrial/satellite IP networks

Given their broadcast nature, satellite communications are one natural engineering choice for multicast service deployment. In this paper, the throughput performance of transmission control protocol (TCP)-like multicast congestion control is analyzed in hybrid terrestrial/satellite networks. With this objective, an analytical framework based on Markov chains is introduced. The major advantage of the proposed analytical model is its scalability in that the number of states of the Markov chain modeling the system is independent of the number of receivers in the multicast session. This is a very important feature as simulation is unfeasible for large numbers of receivers. The framework is used to evaluate the impact of the long propagation delays, high bit-error rates, and channel asymmetry characterizing hybrid terrestrial/satellite communications. The performance results show that in certain cases, it is more convenient to divide the receivers in an appropriate number of groups and establish a different multicast session toward each of the above groups. Also, the convenience of an acknowledgment (ACK) flow reconstructor is shown.     

MPLS-based satellite constellation networks

Nongeostationary satellite constellations with intersatellite links are a challenge for networking due to their continuously changing topology. In order to make maximal use of the network's capacities, special attention has to be paid to routing and traffic engineering. Multiprotocol label switching (MPLS) as underlying protocol is an interesting candidate for this task since it offers many possibilities to exert influence on traffic flows and supports today's dominating Internet protocol traffic very well. This paper describes a general MPLS-based networking concept for satellite networks and discusses different scenarios considering the particularities and constraints of the dynamic topology. Functional elements of MPLS like ingress, egress, or core routers have to be mapped onto the physical entities of the network and prerequisites for traffic engineering are discussed. Routing and rerouting of paths is of key interest since this affects route computation effort and routing performance. Thus, an analytical estimation of routing effort is deduced and numerical and simulation results are presented.     

Next-generation mobile satellite networks

Due to the increasing demands of multimedia services supporting high bit rates and mobility, ATM, TCP/IP, and satellite technology are going to be associated to form the internetwork infrastructure of future global systems. In this scenario, distinctions between terrestrial and satellite communications systems, as well as between fixed networks and 3G mobile networks, will cease to exist in a global coverage wireless system. The European Action COST252 actively participated in developing the satellite component of UMTS     

Interworking of a satellite system for mobile multimediaapplications with the terrestrial networks

This paper deals with the interworking of a satellite system for mobile multimedia applications with the terrestrial environment. The concept of an “overlying network” is introduced with the aim of giving a common approach for the interworking of the considered satellite system with the various terrestrial networks (B-ISDN, N-ISDN, TCP/IP). The paper particularizes the introduced concept to the case in which the considered satellite system is interfaced with the broadband ISDN (B-ISDN)     

Security in data networks

The explosive growth of data networks and their commercial application is driving the need for improved security. This paper aims to raise awareness of the features of secure data networks and the role that encryption plays in this context. An overview of data network security is provided by examining a number of currently available technologies, and how they may be combined to provide a secure network. This is illustrated by a review of existing and proposed encryption services offered by BT/Concert. Taking a glimpse into the future, the ATM Forum's proposals for security in ATM networks are summarised.     

ATM-based routing in LEO/MEO satellite networks with intersatellitelinks

An asynchronous transfer mode (ATM)-based concept for the routing of information in a low Earth orbit/medium Earth orbit (LEO/MEO) satellite system including intersatellite links (ISLs) is proposed. Specific emphasis is laid on the design of an ATM-based routing scheme for the ISL part of the system. The approach is to prepare a virtual topology by means of virtual path connections (VPCs) connecting all pairs of end nodes in the ISL subnetwork for a complete period in advance, similar to implementing a set of (time dependent) routing tables. The search for available end-to-end routes within the ISL network is based on a modified Dijkstra (1959) shortest path algorithm (M-DSPA) capable of coping with the time-variant topology. With respect to the deterministic time variance of the considered ISL topologies, an analysis of optimization aspects for the selection of a path at call setup time is presented. The performance of the path search in combination with a specific optimization procedure is-by means of extensive simulations-evaluated for example LEO and MEO ISL topologies, respectively     

General purpose packet satellite networks

The use of satellite communication techniques to provide integrated data network and point-to-point and conference speech services is discussed. The concept of a General Purpose Packet Satellite Network (GPSN) is introduced in terms of its requirements, and consideration is given to techniques that satisfy these requirements. The class of Priority Oriented Demand Assignment (PODA) algorithms is defined and compared with other packet-oriented demand assignment algorithms. PODA is shown to be well suited to the GPSN application. Networking and access protocol issues are considered in the context of a GPSN. The Atlantic Packet Satellite Experiment, an ongoing experimental program which is developing packet satellite technology, is described in some detail.     

Hybrid satellite and terrestrial networks

The role of satellite communications in networks that provide new services, such as frame relay and multimedia, is investigated. Both passive and active (on-board switching/processing) satellite systems are considered. Novel techniques are developed for each system to demonstrate, via detailed analysis and simulation, how the communications bandwidth agility of multipoint/broadcast satellite channels, and the on-board switching/processing, makes it feasible to provide these new services via hybrid satellite and terrestrial networks in a resource-efficient manner.     

Capacity of two-layered satellite networks

Wireless Networks - Satellite networks have great potential in providing global ubiquitous broadband communication. In this paper, we explore the capacity of both single-layered and two-layered...     

Technical issues regarding satellite packet switching

Many concepts for advanced communication satellite networks have recently been proposed. Critical technical issues relating to satellite packet switching for meshed very small aperture terminal networks and broadband networks are addressed. Hardware considerations, networking and testing issues are discussed.