Publication announcement:

Reconfigurable wavelength-switched optical networks for the Internet
core

Tim Granger

Technical report UCAM-CL-TR-575, University of Cambridge,
Computer Laboratory, November 2003, 184 pages.

This document is now available at

http://www.cl.cam.ac.uk/TechReports/UCAM-CL-TR-575.pdf

Abstract:

With the quantity of data traffic carried on the Internet doubling each
year, there is no let up in the demand for ever increasing network
capacity. Optical fibres have a theoretical capacity of many tens of
terabits per second. Currently six terabits per second has been achieved
using Dense Wavelength Division Multiplexing: multiple signals at
different wavelengths carried on the same fibre.

This large available bandwidth moves the performance bottlenecks to the
processing required at each network node to receive, buffer, route, and
transmit each individual packet. For the last 10 years the speed of the
electronic routers has been, in relative terms, increasing slower than
optical capacity. The space required and power consumed by these routers
is also becoming a significant limitation.

One solution examined in this dissertation is to create a virtual
topology in the optical layer by using all-optical switches to create
lightpaths across the network. In this way nodes that are not directly
connected can appear to be a single virtual hop away, and no per-packet
processing is required at the intermediate nodes. With advances in
optical switches it is now possible for the network to reconfigure
lightpaths dynamically. This allows the network to share the resources
available between the different traffic streams flowing across the
network, and track changes in traffic volumes by allocating bandwidth on
demand.

This solution is inherently a circuit-switched approach, but taken into
account are characteristics of optical switching, in particular waveband
switching (where we switch a contiguous range of wavelengths as a single
unit) and latency required to achieve non disruptive switching.

This dissertation quantifies the potential gain from such a system and
how that gain is related to the frequency of reconfiguration. It
outlines possible network architectures which allow reconfiguration and,
through simulation, measures the performance of these architectures. It
then discusses the possible interactions between a reconfiguring optical
layer and higher-level network layers.

This dissertation argues that the optical layer should be distinct from
higher network layers, maintaining stable full-mesh connectivity, and
dynamically reconfiguring the sizes and physical routes of the virtual
paths to take advantage of changing traffic levels.

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University of Cambridge, Computer Laboratory,
Technical Reports (ISSN 1476-2986)
http://www.cl.cam.ac.uk/TechReports/