This read-write value sets the Maximum Burst Size, in cells, that this channel is allowed to send at the Peak Cell Rate before the SCR policer considers it non-conforming, applicable to VBR and ABR connections with a default of 1000 cells. It defines how large a traffic burst the connection can produce without being penalized, working together with PCR and SCR to shape the traffic contract. A connection expected to send large occasional bursts, such as file transfers, would need a higher bbChanUpcMBS than a smoothly-flowing streaming connection.