Analysis of cell clumping caused by ATM network GFC protocols

Two GFC (Generic Flow Control) protocols are currently under study within the CCITT, namely the BT/NTT proposal and the Australian proposal. In this paper, their basic operating principles are recalled. Then, since it has been recognized in earlier studies that Cell Delay Variation, or more precisely cell clumping, has a major impact on peak cell rate control performed in the Usage Parameter Control, a method for quantifying the magnitude of cell clumping in a cell stream is proposed. This method is subsequently applied for evaluating the magnitude of cell clumping introduced by the above GFC protocols. Although they provide for three priority levels, the analysis is carried out for one priority level only. Under the assumption that each tra c source transmits at its peak cell rate and that a cell spacing device is implemented in each Terminal Equipment, simulation results show that both GFC mechanisms are similar in terms of cell clumping.