their significance will be understood when they are described in detail below a full service mac fsmac has two parts a fsmac cm 192 and a fsmac cmts 124 which are located in the fscm 106 and fscmts 102 respectively the fsmacs role is to co ordinate the dispatch of downstream ip packets and fsmac management messages another role is to co ordinate the efficient and orderly transmission of upstream bursts using the two upstream burst transmitters 194 and 196 one of the transmitters 194 is used for transmitting fsmac management packets such as calibration and bandwidth requests the other transmitter 196 is for transmitting payload of ip packets 199 received from a cpe interface 197 more specifically the transmitter 194 is used to transmit bursts to ucc 1 174 ucc 2 176 or ucc 3 178 using burst profiles communicated to fsmac cm 192 by fsmac cmts 124 by sending down the mdcd 1000 similarly the transmitter 196 is used to transmit bursts to upc 1 182 or upc 2 184 using other burst profiles the fscm 106 learns the characteristics of burst profiles by listening to the mdcd message 1000 and uses the burst profile and time to transmit by decoding the mmap message 900 at the fscmts 102 corresponding to these transmitters in the fscm 106 there are matching frequency agile programmable burst receivers 172 and 180 that will tune demodulate and recover the packets received these packets.