The effective load balancing mechanims contribute to a better service provision.
The usual method to solve uneven load problem in large SDN can be divided into the following two categories.
A. Load Balancing Algorithm based on Centralized Decision
One way to solve uneven load problem among distributed
controllers is that deploying a super controller, which is
responsible for balancing the load of all controllers. This is a good
way to monitor the load change of all controllers from a global
view. However, this algorithm may own two limitations. (1)
The performance of a centralized node is limited by memory,
CPU power and bandwidth. Besides, a centralized node
collects load information periodically and it exchanges lots of
messages frequently with other controllers, which will lead to
performance reduction of the whole system.
B. Load Balancing Algorithm based on Distributed Decision
on distributed decision allows every SDN controller collect other controllers’ load, make its own decision locality. In other words, every
distributed controller acts as not only ordinary controller but
also super controller. By this way, we will get two advantages.
(1) This algorithm is totally based on distributed architecture,
which guarantees the scalability and availability of distributed
SDN controllers. (2) This algorithm just needs one network
transmission for gathering load and doesn’t need push
command to other controllers. As a result, the decision delay
will be reduced in this case.
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