An Efficient TCP Flow Control and Fast Recovery Scheme For the Lossy Networks

• Main Authors: Han-Yang Liao, 廖漢洋
• Other Authors: Yaw-Chung Chen
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/26334022473774949363

碩士 === 國立交通大學 === 資訊工程系 === 88 === With the quick development of Internet, many popular applications such as Telnet, FTP, and SMTP use TCP, which has become one of the Ad hoc transport layer protocol. TCP performs both flow control and congestion avoidance mechanisms to the network so that more reliable and more efficient data transport can be achieved. The current flow control and congestion avoidance mechanisms for TCP were initially proposed by Van Jacobson. This version is called Tahoe, which includes the slow-start algorithm. The later version Reno includes both fast-retransmit and fast-recovery algorithms. The above two versions of TCP are based on increasing the congestion window, provoking packet losses, and then reducing the congestion window repeatedly. Other current research under extensive study is TCP Vegas. It attempts to eliminate the periodically self-induced segment losses. TCP Vegas measures the Round-Trip-Time to compute the throughput of the current end-to-end path to determine the size of congestion window. Besides , other improvements have been proposed , these include TCP New Reno、TCP SACK and TCP FACK. TCP New Reno proposed smooth-start and dynamic recovery algorithms. TCP SACK accommodates the multiple segment losses without incurring timeout, it can retransmit loss segment quickly. TCP FACK provides an accurate view of outstanding data segments and quickly recovery loss segments. According to the current congestion control mechanism, a segment loss is considered as owing to network congestion, thus it reduces the congestion window. However, a packet loss may be caused by some other reason such as a transmission error, this situation is usually encountered in the wireless links. Due to these reasons, we design a mechanism that decomposes the congestion control mechanism into the packet loss indications and its recovery algorithm. The packet loss caused by the transmission error will not be treated as network congestion. For the fast recovery phase, we proposed a modified scoreboard algorithm in TCP FACK to quickly recover the packet loss and prevent the retransmitted packet from being lost again. Through the system simulation, it shows that we can achieve significantly higher throughput than earlier versions of TCP, and the proposed work more suitable for the lossy network.