of.OBS.Networks
Besides the traditional definition presented at the beginning of this chapter, the following
implementations of OBS can be found in literature; each implementation has its advantages
and disadvantages.
??? OBS with fixed data burst length: In this implementation of OBS, all data bursts have
the same length. Its major advantage is the simplification of the switching technique.
However, its disadvantage is the long queuing time of the upper layer packets if there
is no adequate traffic load. An ineffectual solution to this disadvantage is data padding.
This concept is closely related to the cell-switching paradigm where the transport unit
is fixed in size.
??? OBS.with.two-way.setup: In this implementation of OBS, a burst will be transmitted
only after having received a positive acknowledgement of its resource reservation
request. Its advantage is the burst-blocking avoidance in the network??™s core nodes.
However, the additional waiting time may cause buffers to overflow at the network
ingress.
??? Mandatory.FDL/Wavelength.Converters.in.all.nodes: With the disadvantage of
increasing dramatically the cost of the network, OBS could be implemented with
core nodes that are capable to buffer the data bursts and/or convert them to any other
wavelength.
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