Class Guided Random Early Discarding (CGRED)

a novel scheme to provide services differentiation in today's Internet

is proposed.It can precisely maintain the assigned priority and pre-allocated bandwidth for each service class.As a single queue management mechanism

CGRED possesses all advantages of the simplicity

robustness and scalability of schemes like RIO and WRED.And it has the capability to maintain the pre-allocated bandwidth for each class of service precisely just as CBQ.The key enforcement of CGRED to standard RED is to discard packets of different service classes adaptively with different probabilities according to the bandwidth actually occupied by different classes and the pre-allocated bandwidth.To accomplish this

a couple of class-specific guidelines

the 'adjustment direction'and 'guiding probability'

are introduced to conduct the adaptive determination of class-differential discarding probabilities for each class of service.The guidelines for each class of service are updated periodically based on online measured bandwidth utilization.When discarding packets

CGRED sets the class-specific guidelines as the boundary of the packet dropping probability of standard RED.In this way

the unbalance of bandwidth consumption among different service classes is successfully transferred to differential operations in the buffer management among different service classes.Extensive simulation work has been conducted to verify the performance of CGRED and robustness of parameters in its algorithm.The simulation results show that CGRED is an effective scheme to provide Differential Services in networks with pre-allocated bandwidth and pre-assigned priority hierarchy among service classes.