| 10.1 |  | TCP Operation |
| 10.1.4 |  | Windowing and window size |

| The amount of data that needs to be transmitted is often too large to be sent in a single data segment. In this case, the data must be broken into smaller pieces to allow for proper data transmission. TCP is responsible for breaking data into segments. This is similar to feeding a child. Since most small children cannot eat extremely large bites the person feeding a child will often cut their food into smaller pieces that the child's mouth can accommodate. Additionally, receiving machines may not be able to receive data as quickly as the source can send data, perhaps because the receiving device is busy with other tasks or perhaps the sender is simply a more robust device. Once the data is segmented, it must be transmitted to the destination device. One of the services provided by TCP is flow control, which regulates how much data is sent during a given transmission period. The process of flow control is known as windowing. Window size determines the amount of data that can be transmitted at one time before receiving an acknowledgment from the destination. After a host transmits the window-sized number of bytes, the host must receive an acknowledgment that the data has been received before it can send any more data. For example, with a window size of 1, each individual segment must be acknowledged before sending the next segment. TCP utilizes a sliding window when determining transmission size. A sliding window allows for devices to negotiate a window size to allow for more than one byte to be sent during a single transmission. This sliding window also allows the destination device to indicate to the source a need to decrease or increase the amount of data being sent because it is incapable at that time of dealing with that much data.
| Interactive Media Activity Matching: Windowing After completing this activity, the student will be able to understand windowing.
| Web Links Windowing Packets http://howto.lycos.com/l ycos/step/ 1,,5+30+34556+34645+34650,00.html