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TCP Windowing TCP窗口

TCP also supports a concept called windowing. If you have ever copied a file from a network share drive on the Windows operating system, you have seen windowing. Have you ever noticed when you copy a file over the network, it may start out saying there are “2 minutes remaining” until completion, then it jumps up to “3 hours remaining,” then back down to “30 minutes remaining”? This is TCP windowing in action.

TCP還支持稱為窗口化的概念。如果您曾經從Windows操作系統上的網絡共享驅動器中復製過文件，則會看到窗口。您是否曾經註意到通過網絡複製文件時，它可能會說“剩餘2分鐘”直到完成，然後跳到“剩餘3小時”，然後又跳回到“剩餘30分鐘”？這是TCP窗口在起作用。

Essentially, when a communication session is established with TCP, it first performs the three-way handshake. Next, it starts with a small window size, like windows size 1 in the image below, where a single segment is sent over the network and acknowledged. If this is successful, it increases the window size to 2, sending two segments at a time. It continues to do this, increasing the number of segments each time, transmitting more data in each window until an error occurs and retransmissions must be done. If errors occur, TCP understands that it must have been transmitting too fast, so it shrinks the window to slow down communication. As transmissions occur successfully, it again increases the window to push more data in each window. This window size is continually adjusted to get the most segments per window with the least errors in communication.

本質上，當使用TCP建立通信會話時，它首先執行三向握手。接下來，它以較小的窗口大小開始，如下面的圖片中的窗口大小1所示，其中單個段通過網絡發送並確認。如果成功，它將窗口大小增加到2，一次發送兩個段。它會繼續這樣做，每次增加段數，在每個窗口中傳輸更多數據，直到發生錯誤並必須重新傳輸為止。如果發生錯誤，TCP知道它一定傳輸速度太快，因此它縮小了窗口以減慢通信速度。隨著傳輸成功進行，它將再次增加窗口以在每個窗口中推送更多數據。不斷調整此窗口大小，以使每個窗口獲得最多的段，並且通信錯誤最少。

Put the steps of a TCP communication session in the correct order.

以正確的順序放置TCP通信會話的步驟。

Segments two and three are sent over the network.
Segments two and three are acknowledged.
Three-way handshake.
Segment one is acknowledged.
Window size 2 is established.
Window size 1 is established.
A single segment (segment 1) is sent over the network.

True or False: In TCP windowing, if an error occurs, TCP understands that it must have been transmitting too fast, so it shrinks the window to slow down communication.

是非題：在TCP窗口中，如果發生錯誤，則TCP知道傳輸速度太快，因此會縮小窗口以減慢通信速度

TrueFalse

Reset this Activity

checkpoint

Take a minute to stop and reflect on your progress for this learning objective.

花一點時間停下來，為這個學習目標反思自己的進步。

TCP Vs. UDP << Previous Next >> Networking Transfer Protocols 網絡傳輸協議