11-07-2012, 11:29 AM
Optical Buffering for Next-Generation Routers
[attachment=27416]
Introduction
Optical buffering is a major obstacle facing optical
packet switching for future optical communication
networking. Optical packet switching is a highly desirable
approach; however it necessitates the implementation of
contention and congestion resolution within core routers.
Alternatives to buffering such as deflection routing and
wavelength conversion can be used to supplement optical
buffers, but severely limit network performance if used as
the sole solution.
Buffering Approaches
Before comparing transparent optical buffers, it is
necessary to consider the challenges in the electrical
domain. Although speed appears to limit the scalability of
electrical RAM, recent research shows that silicon-based
CMOS RAM can be used as a storage medium for optical
packets at data rates up to 40 Gb/s by using a combination
of optical and electrical components [2]. Such a design
offers long storage times, large capacity, and random
access at arbitrary times. However, loss and component
complexity limits the design to packets less than 10 bytes,
thereby limiting the maximum load of the network.
Conclusion
Five general types of optical buffering are compared
for practical implementation in an optical packet switched
router. Combination electrical-optical buffers using
CMOS RAM as well as EIT slow light buffers both
degrade network performance by limiting packet length
and therefore network load. CRS slow light buffers suffer
from losses and thereby a low bandwidth-delay product,
resulting in impractical bit rates and capacities.
Feed-forward buffers have shown good results and do not
place any limit on packet lengths, but may be impractical
for implementation due to high component counts.
[attachment=27416]
Introduction
Optical buffering is a major obstacle facing optical
packet switching for future optical communication
networking. Optical packet switching is a highly desirable
approach; however it necessitates the implementation of
contention and congestion resolution within core routers.
Alternatives to buffering such as deflection routing and
wavelength conversion can be used to supplement optical
buffers, but severely limit network performance if used as
the sole solution.
Buffering Approaches
Before comparing transparent optical buffers, it is
necessary to consider the challenges in the electrical
domain. Although speed appears to limit the scalability of
electrical RAM, recent research shows that silicon-based
CMOS RAM can be used as a storage medium for optical
packets at data rates up to 40 Gb/s by using a combination
of optical and electrical components [2]. Such a design
offers long storage times, large capacity, and random
access at arbitrary times. However, loss and component
complexity limits the design to packets less than 10 bytes,
thereby limiting the maximum load of the network.
Conclusion
Five general types of optical buffering are compared
for practical implementation in an optical packet switched
router. Combination electrical-optical buffers using
CMOS RAM as well as EIT slow light buffers both
degrade network performance by limiting packet length
and therefore network load. CRS slow light buffers suffer
from losses and thereby a low bandwidth-delay product,
resulting in impractical bit rates and capacities.
Feed-forward buffers have shown good results and do not
place any limit on packet lengths, but may be impractical
for implementation due to high component counts.