SIP Server Exception List for Call Setup Optimization
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Solution Overview
Problem
In IMS networks, when a terminating SIP server becomes unavailable, the originating SIP server waits for a timeout period before attempting to contact an alternate server, leading to resource wastage and delayed call establishment due to repeated attempts to contact the failed server.
Innovation Solution
Implementing a method where the originating SIP server maintains a server exception list to store unavailable SIP servers, allowing it to immediately determine server availability and route messages to available servers without waiting for timeouts, thereby reducing connection establishment time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the originating SIP server waits for a timeout period before attempting to contact an alternate server, then the server can detect server unavailability, but call establishment time increases and resources are wasted
Solution Approach 1:
The patent applies preliminary action by maintaining a pre-populated exception list of unavailable servers at the originating SIP server. When a server becomes unavailable, it is added to this list, allowing subsequent requests to immediately detect and avoid the unavailable server without waiting for timeout periods. This pre-prepared information structure resolves the contradiction by enabling both reliable detection and immediate response.
2Ease of operation
If the originating SIP server repeatedly attempts to contact a failed terminating SIP server, then the server follows standard SIP protocol procedures, but resources are wasted and call establishment is delayed
Solution Approach 1:
The patent implements feedback by monitoring server responses and maintaining an exception list that records unavailable servers. When a server fails to respond or indicates unavailability, this information is fed back into the exception list, which then guides future routing decisions. This feedback mechanism allows the system to comply with SIP protocols while avoiding repeated attempts to failed servers, thereby improving call setup efficiency.
3Device complexity
If the originating SIP server does not store state information for terminating SIP servers, then the server maintains simple operation, but it cannot detect server unavailability and must wait for timeouts
Solution Approach 1:
The patent applies segmentation by dividing server information into two categories: actively contacted servers and exception servers stored in an exception list. This segmentation allows the system to maintain simple operation for normal servers while separately tracking unavailable servers with minimal additional complexity. The exception list structure enables reliable unavailability detection without requiring complex state management for all servers.
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Methods, systems, and computer program products for inhibiting message traffic to an unavailable terminating SIP server are disclosed. According to one method, at least one list of SIP servers accessible by a call session control function (CSCF) is maintained at an originating CSCF. The list includes at least one of availability and unavailability status information for the terminating SIP servers. A request is received to contact a destination via a one of the terminating SIP servers. The list is indexed and a first terminating SIP server is identified. If the first terminating SIP server is determined to be unavailable based on information in the list, a second terminating SIP server is identified using the list.