Load balancing can be useful when dealing with redundant communications links. For example, a company may have multiple Internet connections ensuring network access even if one of the connections should fail.
A failover arrangement would mean that one link is designated for normal use, while the second link is used only if the first one fails.
With load balancing, both links can be in use all the time. A device or program decides which of the available links to send packets along, being careful not to send packets along any link if it has failed. The ability to use multiple links simultaneously increases the available bandwidth.
Major telecommunications companies have multiple routes through their networks or to external networks. They use more sophisticated load balancing to shift traffic from one path to another to avoid network congestion on any particular link, and sometimes to minimize the cost of transit across external networks or improve network reliability.
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