0 Abdelouahab, Abbou, Tat, & Ta b
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In the literature, various OBS switching protocols with different tradeoffs can be found. The
OBS switching protocols differ in the choice of the offset time that can be zero or more, and
the bandwidth reservation and release techniques (bandwidth holding time).
Three main OBS implementations can be identified, based on the offset time which is defined
as the interval of time between the transmission of the first bit of the BCP and the transmission
of the first bit of the data burst. The offset time can be nil, round-trip dependent, or
source-routing dependent.
???. Nil.offset.time: This OBS implementation is the closest to optical packet switching,
and it is similar to ATM Block Transfer and Immediate Transmission (ABT-IT). The
DBs and their corresponding BCPs are transmitted on different wavelengths and separated
by a zero or a negligible offset time. The BCPs reserve the network resources
(wavelength and buffer) upon arrival to the core nodes. The DBs are buffered until
the BCPs are processed and the switching fabrics are configured.
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