Q.933 recommends a procedure for negotiating the sliding-window flow control window, which may take on a value from 1 to 127.The negotiation makes use of a variable k that is calculated from the following parameters:

 

 

The procedure is described as follows:

 

The window size should be negotiated as follows. The originating user should calculate k using the above formula substituting maximum end-to-end transit delay and outgoing maximum frame size for T_td and  L_d respectively. The SETUP message shall include the link layer protocol parameters, the link layer core parameters, and the end-to-end transit delay information elements. The destination user should calculate its own k using the above formula substituting cumulative end-to-end transit delay and its own outgoing maximum frame size for T_td and  L_d respectively. The CONNECT message shall include the link layer core parameters and the end-to-end transit delay information element so that the originating user can adjust its k based on the information conveyed in these information elements. The originating user should calculate k using the above formula, substituting cumulative end-to-end transit delay and incoming maximum frame size for T_td and  L_d respectively.

 

SETUP and CONNECT are messages exchanged on a control channel during the setup of a frame relay connection. Suggest a formula for calculating k from the other variables and justify the formula.