AIMD with Decreasing Increases

• AIMD

• x = x + (x), for every constant interval (e.g., RTT)
• x = (1 - ) x, when there is a packet loss event
• where x is the packet sending rate.

• TCP

• (x)  1, and the increase interval is RTT.
•  = 0.5

• AIMD with Decreasing Increase

• (x) is non-increasing, and limx->+ (x) = 0.

Notes:

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)