Per-Port Switch Variables: Nominal Capacity of the Port: C0 Advertised Rate for the ith interval: ri Port State: Port Initialized Measured Port Capacity for ith Measurement Interval: Ci Bits received in the last measurement interval: bits received Bits transmitted in the last measurement interval: bits sent Bits in Queue at the beginning of current measurement interval: qlen Total Busy (transmit) time during last measurement interval: time busy Limited rate increase: r Algorithm Parameters: Initial Rate Divider: N0 Measurement Interval in Switches: T T is also used for -timer (probe interval) in the sources Queue Control Parameters: a, b, c Exponential moving average: Operational Parameters: Queue equilibrium: Qeq Queue Length under severe congestion: Qsc Default Values: N0 = 200, T = 1 ms, Qeq = 192, 000 bits, a = 1.1, b = 1.002, c = 0.1, = 0.5 Variable Initialization: Ci = C0, r = ri−1 = ri−2 = C0 N0 , 1 Port Initialized = FALSE. Switch Event Routines: procedure EVENT T Timer Expired Routine() 1: while T timer expires do 2: if Port Initialized then 3: Estimate Capacity() 4: if bits received > 0 then 5: Rate Allocation(qlen, bits received, ri−1, ri−2,Ci) 6: else 7: ri = C0 N0 8: end if 9: else 10: if bits received > 0 then 11: Port Initialized = TRUE 12: Rate Allocation(qlen, bits received, ri−1, ri−2,Ci) 13: end if 14: end if 15: Reset T timer 16: end while procedure EVENT Transmit Packet() 1: if packet is tagged then 2: if Rate in Tag ri OR Rate in Tag == −1 then 3: Rate in Tag = ri 4: end if 5: end if 6: Forward the packet Subroutines: procedure Rate Allocation(qlen, bits received, ri−1, ri−2,Ci) 1: Queue Control(fq, qlen,Qeq) 2: = bits received TCfq 3: if == 0 then 4: if qlen < 1 then 5: ri = Ci 6: else 7: ri = ri−1 8: end if 9: else 2 10: ri = min{Ci, ri−1 } 11: end if 12: Exponential Averaging(ri, ri−1, ri−2) 13: Limit Rate Increase(ri, ri−1, qlen,Qeq,r) 14: Variable Capapcity Adjustment(Ci,Ci−1, ri, ri−1, ri−2) 15: bits received = 0 procedure Queue Control(fq, qlen,Qeq) 1: if qlen Qeq then 2: fq = bQeq (b−1)qlen+Qeq 3: else 4: fq = max n c, aQeq (a−1)qlen+Qeq o 5: end if Note: Queue control function can be implemented as a precomputed table procedure Exponential Averaging(ri, ri−2) 1: ri = ri + (1 − )ri−2 procedure Limit Rate Increase(ri, ri−1, qlen,Qeq,r) 1: if qlen < Qeq then 2: r = 1.414r 3: else if qlen > Qsc then 4: r = 0.707r 5: end if 6: if ri − ri−1 > r then 7: ri = ri−1 + r 8: end if procedure Variable Capacity Adjustment(Ci,Ci−1, ri, ri−1, ri−2) 1: if Ci < Ci−1 then 2: ri = Ci Ci−1 ri 3: ri−1 = Ci Ci−1 ri−1 4: end if 5: ri−2 = ri−1 6: ri−1 = ri 3 procedure Estimate Capacity(Ci, bits sent, time busy) 1: Ci = bits sent time busy 2: bits sent = 0 3: time busy = 0 Source Variables: Current Rate: R Source Parameters: = T Feedback Valid Interval: 2T Initial Rate: R0 = C0 N0 Source Initialization: Set timer to expired Tagging a sampled packet every sec Set Feedback Valid Timer to expired Source Event Routines: procedure EVENT Send packet() 1: if timer expired then 2: if Feedback Valid timer expired then 3: R = R0 4: end if 5: Tag an outgoing packet and the rate field in Tag is set as -1; 6: Send following packets at current rate R 7: Reset timer 8: else 9: Send following packet without tag at rate R 10: end if procedure EVENT FECN Received() 1: Set R to rate received 2: Reset Feedback Valid Timer to 2T