Abstract: TCP carries over 70% Internet traffic.And TCP congestion control mechanisms can improve congestion problem in the Internet effectively.The paper analyzes several congestion control mechanisms which are slow-start，congestion avoidance，fast retransmit，fast retransmit and so on，and researches on several common TCP congestion control algorithms，including Tahoe，Reno，NewReno，SACK and Vegas TCP.After that，the pepar analyzes the performance of them quantitatively with the help of NS2（a network simulator），and come to an conclusion at the end which is that SACK and NewReno TCP performed better than Reno and Tahoe TCP，especially when multiple packets are dropped from a window of data.

摘要： TCP协议承载着因特网超过70%的传输流量，其拥塞控制机制可以有效地改善网络拥塞现象。剖析了慢启动、拥塞避免、快速重传、快速恢复等拥塞控制机制，研究了Tahoe、Reno、NewReno和SACK等几种常见的TCP拥塞控制算法。借助于网络模拟器NS2对这几种算法的性能进行了定量分析。结果证明：相对于Tahoe、Reno拥塞控制算法而言，NewReno和SACK TCP可以更快、更平滑地摆脱网络拥塞恢复到正常工作状态。