Abstract
In translucent (or managed reach) WDM optical networks, regenerators are
employed at specific nodes. Some of the connections in such networks are
routed transparently, while others have to go through a sequence of 3R
regenerators that serve as “refueling stations” to
restore their quality of transmission (QoT). We extend an online multicost
algorithm for transparent networks presented in our previous study , to obtain an IA-RWA algorithm that works in translucent
networks and makes use, when required, of the regenerators present at
certain locations of the network. To characterize a path, the algorithm uses
a multicost formulation with several cost parameters, including the set of
available wavelengths, the length of the path, the number of regenerators
used, and noise variance parameters that account for the physical layer
impairments. Given a new connection request and the current utilization
state of the network, the algorithm calculates a set of non dominated
candidate paths, meaning that any path in this set is not inferior with
respect to all cost parameters than any other path. This set consists of all
the cost-effective (in terms of the domination relation) and feasible (in
terms of QoT) lightpaths for the given source-destination pair, including
all the possible combinations for the utilization of available regenerators
of the network. An optimization function or policy is then applied to this
set in order to select the optimal lightpath. Different optimization
policies correspond to different IA-RWA algorithms. We propose and evaluate
several optimization policies, such as the most used wavelength, the best
quality of transmission, the least regeneration usage, or a combination of
these rules. Our results indicate that in a translucent network the employed
IA-RWA algorithm has to consider all problem parameters, namely, the QoT of
the lightpaths, the utilization of wavelengths and the availability of
regenerators, to efficiently serve the online traffic.
© 2010 IEEE
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