LOOP CONDITION PREVENTION AT INTERNETWORK INTERFACE BOUNDARY

摘要

The present invention provides a solution to maximize the chance of completion for an ISUP to SIP direction call by enabling a bigger factor for converting ISUP hop counter to SIP Max-Forwards value than the reverse direction thus enabling more hops in the SIP network. Enabling a bigger factor for ISUP to SIP direction can cause loops without special considerations. This invention provides an algorithm that prevents a “loop condition” that can arise at the interface boundary of two telephone networks, known by their standard names 1SUP and SIP networks. The present invention solves the “loop condition” problem by adjusting the Hop Counter and Max-Forward parameter values in a predetermined manner such that the adjusted parameter values break the cycle of providing the same parameter values between networks at the network boundary for an uncompleted connection, or break an endless “loop condition”.

主权项

1. A method for preventing a loop condition on a network boundary interface between a plurality of telephone networks, comprising the steps of:
receiving at a first network server on a first network a first call parameter value associated with a first telephone call, said first call parameter value being a predetermined number of remaining transmissions of the first telephone call to one or more nodes that will be permitted before the first telephone call is cleared from the system as an unconnectable telephone call;
generating a second call parameter value associated with the first telephone call using the first call parameter value, said second call parameter value is a parameter that will be used on a second network to determine the remaining transmissions of the first telephone call to one or more nodes that will be permitted before the first telephone call is cleared from the system as an unconnectable telephone call; andreceiving at the first network server on the first network a third call parameter value associated with the first telephone call as calculated using the second call parameter value,said third call parameter value being less than the first call parameter value and said third call parameter value being a predetermined number of remaining transmissions of the first telephone call to one or more nodes that will be permitted before the first telephone call is cleared from the system as an unconnectable telephone call;said second call parameter value being calculated by artificially decrementing the parameter values after applying a conversion factor to make sure the second parameter value is not too small.