Methods to synchronize the IN SCP’s overload protection mechanism

The Intelligent Network’s (IN) architecture is based on Service Switching Points (SSP’s) that switch telephone calls, and the Service Control Points (SCP’s) that make part of the decisions about the routing and the charging of calls that are switched by the SSP’s. To communicate, SSP and SCP use the IN Application Part (INAP) protocol. IN has a distributed mechanism for protecting the SCP from overload that uses a traffic filtering method called “call gapping”. The synchronization of the load protection in IN is a problem because there is no reliable syn­chronization scheme in the INAP protocol. In the text I examine several solutions to the pro­blem. Though formulated in terms of IN, the synchronization methods apply to any similar network, i.e. a network with a star topology, traffic throttles in the peripheral nodes, and a bottleneck in the central node.