What is the purpose of TCP fast retransmission

The purpose of TCP fast retransmission is to improve the reliability and performance of data transmission over a network. When a TCP sender detects the loss of a packet, it will typically wait for a certain period of time before retransmitting the packet. With fast retransmission, however, the sender can quickly detect that a packet has been lost by receiving duplicate acknowledgments from the receiver. When the sender receives three duplicate acknowledgments for the same packet, it assumes that the packet has been lost and immediately retransmits it. This helps to reduce the overall delay and improve the throughput of the network by avoiding unnecessary timeouts and retransmissions.

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TCP retransmission

TCP retransmission refers to the process of resending packets that were not acknowledged by the receiver or were lost in transit. When a sender sends a packet to a receiver over a TCP connection, it waits for an acknowledgment message from the receiver indicating that the packet was received successfully. If the sender does not receive an acknowledgment within a certain timeout period, it assumes that the packet was lost and sends it again. This is known as retransmission.

TCP retransmission is important for ensuring reliable data transfer over the internet. Without retransmission, data packets lost in transit would result in missing data at the receiver end. Retransmission helps to ensure that all packets are received successfully and in the correct order.

However, excessive retransmissions can also be a sign of network congestion or other issues that can affect the performance of the connection. Therefore, it is important to monitor and analyze retransmissions to identify and address any underlying issues that may be causing packet loss.

TCP Out_of_Order和 TCP Retransmission

TCP Out_of_Order和TCP Retransmission都是TCP协议中的重要概念。

TCP Out_of_Order指的是TCP数据包到达接收端的顺序与发送端发送的顺序不一致，这可能是由于网络拥塞、路由器故障等原因导致的。当出现TCP Out_of_Order时，接收端会重新排序数据包，以确保数据包按正确的顺序组装起来，从而避免数据包丢失或者乱序。

TCP Retransmission指的是TCP数据包在传输过程中由于丢失或者超时而被重新发送的现象。当发送端发送一个TCP数据包时，它会等待接收端的确认消息，如果在一定时间内未收到确认消息，发送端会认为数据包丢失，然后重新发送数据包。TCP Retransmission可以保证数据包的可靠性，但是会增加网络的延迟。

总之，TCP Out_of_Order和TCP Retransmission都是TCP协议中保证数据传输可靠性的重要机制。