Abstract
In designing multimedia applications over a multi-service network, we face the problem of supporting applications that have QoS requirements. Thanks to the fruitful research efforts in high-speed networking and multimedia applications, there has been, however, significant progress in understanding of how to deliver a data throughput (i.e. packets) above a certain rate and within delay bounds. It is now common agreement that for real-time traffic, the delivery of the data packets in a correct order over a logical association between users is likely to follow the connectionoriented principle. For such a connection establishment, the wavelength-routing circuits are the natural candidates. In this context, given a set of constraints for an end-to-end connection, the question arises: what subset of constraints regarding the “end-to-end” QoS requirements will be taken into account for wavelength-routed connection accommodation, if any? The best QoS agreement is certainly end-to-end. However, this requires co-ordination across many network devices, which is a big network design challenge, expensive to build and difficult to manage (Figure 3-1). We will see later on that instead of this co-ordination across the multi-layer stacks, the QoS parameters are translated into the client network requirements for links, paths or signal quality constraints in the wavelength domain.
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Notes
Note that here the term virtual circuit might be suitable. However, since a virtual circuit can also be established over the default paths in the IP layer (e.g. by using MPLS), in order to distinguish between virtual circuits in the IP layer and the wavelength circuits in the OCh layer, we need a distinctive term. For example, the term OCh-trail can be used.
Yet, in the case where link or node disjoint paths must be provided, topology and capacity must be separately considered.
Obviously, there is also a third option: unpredictable (a priori unknown) connectivity changing, between two arbitrary chosen routers, where the link and network connectivity is changing in a adaptive, self-organising, and autonomous way [Lin97]. However, this topic is far out of the scope of this work and needs a separate study.
Rather than “transparent”, the term “service-flattened” WDM networks is used. While this distinction might appear superfluous, there is a significant difference between these two types of networks. In transparent networks, all wavelength connections are treated in the same way, and no particular requirements for a certain service-type are taken into account (e.g. only busy and idle states are considered as a constraint when accommodating a connection request). In a service-flattened network, on the other hand, like in a transparent network, any network element can be allocated for any type of service on any wavelength, but the requirements on transmission spans, manageability or restorability, for example, might differ. Finally, in a service-reliant network, all wavelengths and paths are considered in a service-specific way.
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© 2001 Springer-Verlag Wien
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Jukan, A. (2001). Service-Differentiated Connection Set-Up. In: QoS-based Wavelength Routing in Multi-Service WDM Networks. Progress in Communication Networks, vol 1. Springer, Vienna. https://doi.org/10.1007/978-3-7091-6247-7_3
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DOI: https://doi.org/10.1007/978-3-7091-6247-7_3
Publisher Name: Springer, Vienna
Print ISBN: 978-3-7091-7268-1
Online ISBN: 978-3-7091-6247-7
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