AIMD has many good properties including global stability and its behavior is well understood. The AIMD algorithm can be modeled by an increase function of alpha(x) and a decrease factor of beta.
For example, in TCP, alpha(x) always equal to 1 and beta is 0.5.
UDT uses a special case of AIMD algorithm, in which the increase function alpha(x) is non-increasing, and approaches to zero as x increases.
(x UNIT: packets/sec)