Virtual Topology

Authored by: Partha Pratim Sahu

Advances in Optical Networks and Components

Print publication date:  July  2020
Online publication date:  July  2020

Print ISBN: 9780367265656
eBook ISBN: 9780429293962
Adobe ISBN:


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Design of next generation optical Wide-Area Networks (WANs) based on Wavelength-Division Multiplexing (WDM) are done for nationwide and global coverage. Considering wavelength multiplexers and optical switches (cross-connects) in routing nodes, there is a need to design a virtual topology for a given physical fiber networks [1–50]. The virtual topology having a set of “light paths” is set up for transmitting packets of information in the optical domain using optical circuit switching, but packet forwarding from one light path to another light path is also carried out by optical switching [1]. Each light path in the virtual topology is established by using the Routing and Wavelength Assignment (RWA) techniques mentioned in Chapter 2. In this chapter, we will discuss the virtual topology having a constraint and additional relaxations. If no wavelength converter is used in the optical cross-connect (OXC) (discussed in the previous chapter), the wavelength of the light path obeys wavelength continuity constraint. This network architecture depends on a combination of well-known “single- hop” and “multi-hop” approaches, and here attempts are made to consider the characteristics of both. A “light path” in this architecture provides “single-hop” communication between any two nodes. Within a limited number of wavelengths, “light paths” between all source-destination pairs are obtained. As a result, multi-hopping between “light paths” is needed. In addition, when the existing traffic pattern changes, a different number of “light paths” making a different “multi-hop” virtual topology is required. A networking issue challenge is to make the necessary reconfiguration with minimal disruption of the network operations in network architecture where the use of wavelength multiplexers gives the advantage of much higher aggregate system capacity due to spatial reuse of wavelengths and supports a large number of users.

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