deploying and managing ip over wdm networks - Index of

264 Deploying and Managing IP over WDM Networks
also translated the requirement of these different types of optical networks into
the requirements of the specific network devices or subsystems. Specifically,
transmitters, receivers, fibers, regenerators, and switches have been covered.
Among the challenges of the control and management of IP over WDM
networks, we mention dynamic routing and wavelength conversion in the optical
domain. The dynamic routing of optical paths can be carried out by extensions
of a link state routing protocol such as OSPF or IS-IS. However, in
contrast to traffic-independent routing as in the IP layer, wavelength routing
must be performed while taking into account the network traffic load. On the
other hand, wavelength conversion capability is also necessary because it can
reduce the optical path blocking probability. Nevertheless, this technology is as
yet immature and expensive.
Fault localization is one of the most difficult issues in IP over a WDM
reconfigurable optical core. This is because the mapping between the observed
parameters at the optical layer, as for instance the signal-to-noise ratio, to IPlevel
observable properties, as the packet loss rate, is not straightforward. Additionally,
the management of thresholds is very complex because threshold values
tuned to specific bit rates might be not valid for other rates and because the
threshold values may also have to be updated across the network due to restoration
or reconfiguration processes. Fault localization schemes are also very complicated
due to the intrinsic uncertainty of the correlation between monitored
parameters at the IP and at the WDM layer. With respect to fault recovery, new
models need to be implemented to overcome the skipping of the SDH layer that
has traditionally supported this functionality.
From the service provider perspective, a shift towards automatically
switched optical network services are dependent on the possibility of integrating
the optical CP with legacy management systems. Optical CP integration can follow
two steps. The first one represents a management-based solution with
carrier-specific CPs directly coupled with the network management plane
through the necessary adaptations. However, this approach does not scale well.
At the second step, a thin layer above multiple vendor control domains would
be provided as mediation between the management plane and vendor-specific
domains. This layer would represent the carrier common CP communicating
with the management plane through a control-management interface.
References
[1] Rajagopalan, B., et al., “IP over Optical Networks: Architectural Aspects,” IEEE Commun.
Mag, September 2000, pp. 94–102.
[2] Wei, J. Y., “Advances in the Management and Control of Optical Internet,” IEEE J. on
Select. Areas Commun., Vol. 20, No. 4, 2002, pp. 768–785.