It then sends the following message to the other side, and includes the local channel number and initial window size in the message. The channel type is a name as described in the SSH architecture document, with similar extension mechanisms. The client MAY show the additional information to the user. The window size specifies how many bytes the other party can send before it must wait for the window to be adjusted. Both parties use the following message to adjust the window.
Data transfer is done with messages of the following type.
The maximum amount of data allowed is the current window size. The window size is decremented by the amount of data sent. Both parties MAY ignore all extra data sent after the allowed window is empty. Additionally, some channels can transfer several types of data. An example of this is stderr data from interactive sessions.