ISUP-SIP Interface Loop Prevention via Asymmetric Parameter Mapping
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Solution Overview
Problem
A loop condition occurs at the interface boundary of ISUP and SIP networks, where a telephone call is repeatedly routed between the two domains with a non-decrementing hop counter, leading to continuous processing of uncompleted connections and resource consumption.
Innovation Solution
Adjusting the Hop Counter and Max-Forward parameter values using predetermined mapping equations to break the cycle of providing the same parameter values between networks, ensuring that the Hop Counter or Max-Forward value decreases with each transition, thereby preventing infinite loops and conserving system resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Hop Counter and Max-Forward parameters are mapped using standard equations between ISUP and SIP networks, then call routing between networks is enabled, but loop conditions occur causing infinite routing cycles and resource consumption
Solution Approach 1:
The patent applies preliminary anti-action by proactively adjusting the Hop Counter and Max-Forward parameter values before routing calls across network boundaries. Instead of waiting for loops to form, the system preemptively modifies these parameters at the ISUP-SIP interface to ensure they will decrement appropriately, preventing loop conditions before they can occur. This is achieved by detecting potential loop scenarios and adjusting parameters in advance to break the symmetry that causes infinite routing cycles.
Solution Approach 2:
The core solution involves changing the parameter values of Hop Counter and Max-Forward at the network interface boundary. The patent modifies these parameters asymmetrically when calls transition between ISUP and SIP domains, ensuring that the parameter values decrease with each crossing. This parameter adjustment breaks the symmetry in standard mapping equations that would otherwise allow loops, while still maintaining sufficient values to permit legitimate multi-hop routing scenarios.
2Reliability
If parameter values are adjusted to prevent loops, then infinite routing cycles are broken, but call routing flexibility may be reduced
Solution Approach 1:
The patent applies local quality by implementing asymmetric parameter adjustment only at the specific ISUP-SIP network interface boundaries where loops occur, rather than uniformly across the entire network. The Hop Counter and Max-Forward values are modified locally at the interface points, allowing standard routing flexibility to be maintained within each network domain while preventing loops only at the critical boundary transitions. This localized approach preserves routing adaptability in the core networks while addressing the loop problem only where needed.
Solution Approach 2:
The system applies partial action by adjusting parameter values only when calls cross the ISUP-SIP boundary, rather than modifying all Hop Counter and Max-Forward values throughout the entire call path. The patent selectively intervenes at the interface points where the asymmetry causes loops, allowing full parameter flexibility to be maintained within each network domain. This partial adjustment is sufficient to prevent loops while preserving routing flexibility for legitimate multi-hop scenarios that do not involve boundary crossings.
3Adaptability or versatility
If the Hop Counter and Max-Forward parameters maintain symmetric mapping between networks, then protocol compatibility is maintained, but loop conditions arise due to non-decrementing values
Solution Approach 1:
The patent directly addresses the symmetry problem by introducing asymmetric parameter adjustment at the ISUP-SIP interface. Instead of maintaining symmetric mapping where the same equations apply in both directions, the system applies different adjustments depending on the direction of call flow. When calls transition from ISUP to SIP or vice versa, the Hop Counter and Max-Forward values are adjusted asymmetrically to ensure they will decrement on the return trip, breaking the symmetry that causes loops while maintaining protocol compatibility through standardized parameter names and basic mapping relationships.
Data Source
AI summary
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”.