By creating a single pool of bandwidth, the boundaries normally
encountered in each channel are replaced by a single boundary equal to the total
bandwidth of all of the channels. As long as a payload can fit into this concatenated
channel, it can be transported and protected. This capability is particularly beneficial
when transporting signals that have bit rates greater than any individual line channel,
transporting signals with formats that are not accepted neatly into the transmission
channels, or mixing different types of signals in the same system.
Access Network Issues
The access infrastructure is the final frontier in broadband networking. The single
most limiting factor in the current access network is the availability of fiber to any
given building. Only by bonding or concatenating multiple channels can true broadband
speed be achieved on wireline networks where there is no fiber connectivity.
While the standards bodies have recognized this bonding need with the development
of virtual concatenation (VCAT) and link concatenation adjustment scheme (LCAS) for
SONET, IMA for ATM, MLPPP for IP, and so on, each of these approaches is unique
to the protocol or network supported.
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