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:
receiving, at a network server on a first network, a first call parameter value associated with a telephone call, the first call parameter value being a predetermined number of remaining transmissions of the telephone call to one or more nodes of the first network that will be permitted before the telephone call is cleared as an unconnectable telephone call; generating a second call parameter value associated with the telephone call using the first call parameter value, the second call parameter value being a parameter that will be used on a second network to determine the remaining transmissions of the telephone call to one or more nodes of the second network that will be permitted before the telephone call is cleared as an unconnectable telephone call; and receiving, at the network server, a third call parameter value associated with the telephone call as calculated using the second call parameter value, wherein the third call parameter value is less than the first call parameter value, the third call parameter value being a predetermined number of remaining transmissions of the telephone call to the one or more nodes of the first network that will be permitted before the first telephone call is cleared as an unconnectable telephone call, and wherein the second call parameter value is calculated by artificially decrementing the parameter values after applying a conversion factor to make sure the second parameter value is not too small to prevent the telephone call from reaching a terminating destination.