Bursts of correlated messages can be sent through the SS7 network if access is available to user signalling bearer capabilities as specified in the CCITT Q.931 standard. These user-to-user correlated messages would cause an increase in the delay of background telephone traffic consisting of ISUP and TCAP which has been primarily transferred through the SS7 network. A leaky bucket (LB) controller is introduced to prevent the correlated messages from degrading the link delay performance of background telephone traffic (BTT). The main purpose of the LB controller is to give appropriate time separation between the correlated messages during which BTT messages can be sent. The authors model the system as a Markov chain and analyse the effect of time separation on the delay performance of BTT at the link transmit queue.