The deployment of
higher-speed transmission channels, higher-wavelength-count WDM systems or higherspeed
ports on packet-processing devices does not change the fundamental process. As
opposed to bandwidth management approaches that are focused on wavelengths, the
big pipe architecture allows all of the independent technologies to be developed and
deployed separately. Therefore, carriers are not forced to change several aspects of their
network to capitalize on developments in any particular area.
Protection mechanisms for the big pipe solution are also fundamentally different from
those considered by proponents of wavelength-switching solutions. In a wavelength-based
TDM: Circuit Bonding 281
solution, the only issue to consider in the event of failure is the restoration of the lost
wavelength. Solutions ranging from path-level protection to mesh-based span protection
have been proposed.
With the big pipe concept, the capacity of several transmission channels is combined
to form a single large payload. In this scenario, many options exist for implementing
protection. If a single transmission channel fails, for example, the failure may not affect
the transmission of data if extra capacity exists in the big pipe.
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