A COMPARISON OF CCS TANDEM OVERLOAD CONTROLS

In this paper we analyse issues associated with overloads in tandem sw itching systems in Common Channel Signalling (CCS) networks. In partic ular, we examine the need for, and effectiveness of, Automatic Congest ion Control (ACC), a CCS mechanism which allows a congested switching system to inform adjacent CCS nodes of its level of overload, and subs equently controls the rate at which traffic is sent to the congested n ode. We demonstrate the critical need for end-offices and tandem switc hing systems to implement some form of ACC if network performance is t o be maintained during congestion, especially in tandem exchanges. In addition, we find that the presently defined ACC should be expanded to allow more levels of congestion to be reported to adjacent nodes, so that a more effective, finer grained control is produced.