一种改进的卫星宽带网络拥塞控制算法

An Improved Congestion Control Algorithm for Satellite Broadband Networks

以卫星宽带网络为应用背景,从卫星宽带网络的特点出发,设计并实现了一种新的TCP拥塞控制算法——TCPCA。针对卫星网络高误码率的特点,在接收端采用了Casablanca分类器区分链路丢包和拥塞丢包。为了克服由大时延带来的重传时间间隔过大的缺点,采用了批量重传来及时重传丢失的报文段;同时针对大时延致使网络恢复时间延长的缺点,在发送端采用智能窗口调整策略,避免由于链路错误而减小发送窗口导致的吞吐量下降。利用仿真软件NS2,通过和传统的TCP拥塞控制机制相比较,TCPCA算法能够提高吞吐量,并且保证了公平性和友好性。

In satellite broadband networks, congestion controls have lower throughput performance mainly due to long propa- gation delays and high link error rates. Considering these characteristics, a new congestion control seheme called TCPCA is proposed. The Casablanca discriminator is adopted in the receiver to distinguish wireless losses from congestion losses to solve the problem of high link error rates. In order to alleviate the long retransmission intervals brought by long propagation delays, bulk retransmissions are introduced to retransmit the lost packets in time. Since long propagation delays make the networks need more time to recover, an intelligent congestion window adjustment strategy is adopted to avoid the unnecessary decrease of congestion window due to wireless losses. NS2 simulations show that TCPCA outperforms other conventional TCP schemes in terms of throughput. It also ensures a fair share of network resources with retaining friendliness to other TCP variants.