何谓拥塞(Congestion)
question : 随着λin和λ’in不断增加会怎样?
LastByteSent - LastByteAcked <= CongWin
question 1 : 如何感知网络拥塞?
question 2 : 如何合理地调整发送速率?
example:
MSS = 500 byte,
RTT = 200 msec
初始化速率 initial rate = 20k bps
initialize: Congwin = 1;
for (each segment ACKed)
Congwin++;
until (loss event ORCongWin > threshold);
question : 何时应该由指数性增长切换为线性增长(拥塞避免)?
answer : 当CongWin达到loss事件值的1/2时
举例:每个Segment 有1500 个byte, RTT 是100ms,希望获得 10Gbps的吞吐率