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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Transport Layer Protocols            9  Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)                 9  TCP/IP Transmission Control Protocol (TCP)                      9  TCP Fundamentals and General Operation

TCP Data Handling and Processing: Streams, Segments and Sequence Numbers 1 2 3 4 5 6 7 8 9 TCP Ports, Connections and Connection Identification

Changes to TCP Categories and Window Sizes After Sending Bytes In the Usable Window

Now, let's suppose that in our example above, there is nothing stopping the sender from immediately transmitting the 6 bytes in the Category #3 (the usable window). When it does so, the 6 bytes will shift from Category #3 to Category #2. The byte ranges will now be as follows (Figure 208):

1. Bytes Sent And Acknowledged: Bytes 1 to 31.
   
   
2. Bytes Sent But Not Yet Acknowledged: Bytes 32 to 51.
   
   
3. Bytes Not Yet Sent For Which Recipient Is Ready: None.
   
   
4. Bytes Not Yet Sent For Which Recipient Is Not Ready: Bytes 52 to 95.
   

   Figure 208: TCP Stream Categories and Window After Sending Usable Window Bytes

   This diagram shows the result of the device sending all the bytes it is allowed to transmit in its usable window. It is the same as Figure 207, except that all the bytes in category #3 have moved to category #2. The usable window is now zero, and will remain so until an acknowledgment is received for bytes in category #2.

   
   

TCP Data Handling and Processing: Streams, Segments and Sequence Numbers 1 2 3 4 5 6 7 8 9 TCP Ports, Connections and Connection Identification