An Analysis of One Direction of Window Mechanism

A queuing model is presented for the analysis of one direction of window mechanism as used in numerous data communication control procedures e.g., X.25, HDLC and SDLC. Two models of message length are considered viz. fixed length and exponential distribution. A novel approach is used to determine an effective service time to account for possible inserted idle time while waiting for the window to reopen. A set of delay characteristics is determined for different window sizes. A minor modification of the frame format is suggested to improve on the performance of the window mechanism.