Abstract
Optical flow switching (OFS) has been recently introduced
as a potential “green” architecture addressing the power issue
of store-and-forward packet switching in future MAN-WAN Terabit networks.
One key architectural component of OFS differentiating it from other “green”
WAN architectures such as optical circuit switching (OCS), optical packet
switching (OPS) and optical burst switching (OBS), is its centralized flow
scheduling. Comparing the theoretical network capacity regions of OFS, OCS,
OPS and OBS has revealed that the dominating theoretical capacity depends
on the hardware as well as on the port configuration. The dominating actual
capacity (throughput) that can be achieved also depends on the flow schedulers
supported by each architecture. Since centralized scheduling incorporated
in OFS is the least restricting between all scheduling methods, OFS is a promising “green”
architecture option for future MAN-WAN Terabit networks. For better understanding
the actual potential throughput of OFS, we study its scheduling problem in
a realistic traffic model where lightpath requests arrive as a time-dependent
Poisson process with Pareto distributed lightpath service times. Lightpath
schedules are taken at fixed time intervals (larger than 100 ms) in a central
node and flows that have already been scheduled cannot be interrupted before
their completion. The scheduling problem is represented as a discrete-time
Markov decision process where the objective function is given by the flow
blocking probability over a finite time horizon. We derive three lower bounds
to the objective function and propose several schedulers, with and without
fairness requirements. The performance of our OFS schedulers are evaluated
under both static and limited dynamic routing, by emulating the algorithms
on random network topologies for two hours. The main result is that our proposed
max-min fair scheduler with limited dynamic routing significantly outperforms
all other schedulers with static routing. Furthermore, its blocking probability
is close to the lower bound for static routing.
© 2011 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription