Method and apparatus for transmission link error rate monitoring

A system for monitoring the error rate on a transmission link, said link being arranged to transport messages from a transmitter to a receiver, said transmitter including a buffer for storing messages including messages requiring retransmission to said receiver due to transmission errors on said link, said system comprising

• means for formulating an estimate of the total length of the messages in said buffer due to said transmission errors, wherein said formulating means includes
• means for monitoring the link for successive time intervals, and
• means for adding an increment to the estimate if one or more errors occurred in the interval, and for subtracting a decrement from the estimate if no errors occur in the interval,
• means for monitoring the estimate to ascertain when the length of the messages stored in said buffer exceeds a threshold, and
• means for taking the link out of service if the threshold is exceeded.

A method for monitoring the error rate in messages transmitted over a transmission link so that the link can be taken out of service if excessive errors occur, said transmission link arranged to buffer messages such that messages not successfully transmitted on said link are available for subsequent retransmission on said link, said method comprising the steps of

• counting the number of errors occurring on the link during successive time intervals of .tau. seconds, where .tau. is the round trip time required to transmit a message on said transmission link and then notify said buffer to initiate a retransmission,
• responsive to said counting step, formulating an estimate of the amount of data requiring retransmission on said link due to errors, said estimate being a joint function of (a) said round trip time .tau., (b) the maximum allowable error rate .lambda..sub.0 on said link, and (c) the speed "c" of said link,
• comparing said estimate to a threshold value determined as a joint function of (a) .OMEGA., the maximum allowed amount of data requiring retransmission, (b) .lambda..sub.0, and (c) .tau., and
• taking said transmission link out of service when said estimate exceeds said threshold.

A method for monitoring the error rate on a transmission link, said link being arranged to transport messages from a transmitter to a receiver, said transmitter including a buffer for storing messages including messages requiring retransmission to said receiver due to transmission errors on said link, said system comprising the steps of

• formulating an estimate of the total length of the messages in said buffer due to said transmission errors, wherein said formulating step includes
• monitoring the link for successive time intervals,
• adding an increment to the estimate if one or more errors occurred in the interval, and
• subtracting a decrement from the estimate if no errors occurred in the interval,
• monitoring the estimate to ascertain when the length of the messages stored in said buffer exceeds a threshold, and
• taking the link out of service if the threshold is exceeded.