It is anticipated that future core networks may evolve to Optical Cross-Connect (OXC) based architectures where switching is carried out at the granularity of wavelength-based circuits. While the switch fabric is an important component of an OXC, the number of ports is typically a more significant contributor to its cost. Reducing the number of ports (or number of wavelengths per link) will also result in lower transmission-systems costs. We investigate the effect of incorporating some packet switching functionality in the OXC and try to quantify the bandwidth savings that can be gained by doing so, under certain assumptions about the network and the traffic characteristcs. Results show that taffic grooming and statistical multiplexing gain, which are introduced by the packet handling functionality, lead to better channel utilization. This can result in lowering the number of channels and ports and in reducing the OXC size and cost.
The effect of traffic variability on statistical multiplexing gain is analyzed in a bufferless continuous fluid-flow traffic model. Two different methods are used to account for traffic loss, namely a method based on overflow probability and another one based on traffic loss ratio. It is shown that for both methods, bandwidth savings due to statistical multiplexing gain (SMG) can be significant and increases with increasing traffic variability. It is also shown that SMG and channel utilization increase as the number of composite traffic streams increases and as traffic loss probability/ratio is lowered.
In Optical Burst Switching (OBS), data packets at the edge of the network are aggregated into larger units identified as
Data Bursts (DBs). When switching is performed synchronously in OBS core nodes (slotted switching), each DB has to
be segmented at the switch input into fixed size units. Each unit is switched to a designated output in an "optical" time
slot (a parameter of the "optical" switch). The purpose of our study is to give recommendations concerning the optimum
size of these optical slots so as to minimize the overhead arising from the segmentation process. In order to estimate the
total overhead due to this process we take into account the statistical distribution of the burst size, the possible padding
of the last burst segment (to completely fill an optical slot) and the overhead due to the optical-slot preamble.