Permit delivery rates of an ATM cell based access network MAC protocol

RACE 2024, Broadband Access Facilities (BAF) project has developed a Medium Access Control (MAC) Protocol that explicitly manages the transmission of each individual ATM cell. This mechanism polls each Network Termination (NT) and depending on the NT´s queue length issues permits to send. Multiplexing several variable bit rate sources together causes cell clumping when issuing permits at the sum of the peak bandwidths to a NT. A reduction of the cell clumping can be gained by transmitting the permits at the mean bit rate of the NT. However, this has the effect of smoothing the customer´s traffic profile to a constant bit rate stream producing larger cell delay variation and slower reaction times across the passive optical network. This paper presents a compromise between transmitting permits at the sum of the peak rates and the mean. By reduction of permit transmission, traffic shaping can be performed which will smooth the burstiness of the traffic