Lightweight RRQ for H.323 Gatekeeper Recovery
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Solution Overview
Problem
Existing methods for re-establishing a call signaling channel in packet data networks, such as those using the H.323 protocol, are inefficient and generate excessive network traffic, especially when attempting to connect with alternate gatekeepers, and are problematic in environments with firewalls.
Innovation Solution
A lightweight registration request (RRQ) message is sent to alternate gatekeepers to confirm registration and establish a call signaling channel, allowing for immediate re-establishment if a registration confirmation (RCF) is received, or restarting the registration process if a rejection is received with a 'discovery required' reason code.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TCP connection is attempted with each gatekeeper in the alternate list one at a time, then a successful connection can be established, but the process becomes extremely time consuming
Solution Approach 1:
The endpoint sends lightweight RRQ messages to multiple alternate gatekeepers simultaneously before establishing full TCP connections, performing preliminary registration checks in parallel to identify available gatekeepers early in the recovery process
Solution Approach 2:
The patent transitions from sequential one-at-a-time gatekeeper selection to parallel simultaneous attempts across multiple gatekeepers, adding a temporal dimension to the recovery process and enabling concurrent registration requests
2Speed
If TCP connect messages are sent to multiple gatekeepers simultaneously, then gatekeeper location speed increases, but excessive network traffic is generated
Solution Approach 1:
The patent extracts the essential registration check function from the full TCP connection establishment process, using lightweight RRQ messages that contain only the necessary registration parameters without initiating complete connection protocols
Solution Approach 2:
The lightweight RRQ messages serve as disposable, low-overhead probes that can be sent to multiple gatekeepers simultaneously without the cost of full TCP connections, and are discarded after serving their registration check purpose
3Reliability
If multiple TCP connections are established to find an available gatekeeper, then available gatekeeper identification improves, but needless overhead is generated when connections must be torn down
Solution Approach 1:
The patent extracts the gatekeeper availability detection function from the full TCP connection lifecycle, using lightweight RRQ/RCF message exchanges that can be initiated and terminated without establishing complete TCP connections, eliminating the need to tear down multiple connections
Solution Approach 2:
The lightweight RRQ mechanism allows the endpoint to independently determine gatekeeper availability through registration requests and confirmations without requiring full connection establishment and management, making the endpoint self-sufficient in gatekeeper selection
4Ease of operation
If ping messages are used to determine if a gatekeeper is up, then gatekeeper availability checking simplifies, but firewalls filter out ping messages
Solution Approach 1:
The patent changes the message type parameter from ICMP ping to H.323 lightweight RRQ registration request, transforming the probing mechanism into a standardized signaling protocol message that firewalls are less likely to filter
Solution Approach 2:
The lightweight RRQ message acts as an intermediary that bridges the endpoint and gatekeeper through standard H.323 signaling infrastructure, avoiding direct ICMP ping that gets blocked while still achieving availability detection
Data Source
AI summary
The present invention is directed to the recovery of a call signaling channel in connection with a realtime communication established using a packet data network. Specifically, in the event of the failure of an endpoint's current gatekeeper, this invention provides a fast mechanism for searching for an alternate gatekeeper with which the endpoint can re-establish its call signaling channel and hence can regain call service, including call features on existing calls. In accordance with an embodiment of the present invention, a lightweight registration request message is sent on the RAS channel to an alternate gatekeeper in response to the loss of an established call signaling channel, even though a keep alive signal is not then due. The lightweight RRQ message may be sent to individual gatekeepers on an alternate gatekeeper list, until a registration confirmation message is received. Alternatively, a lightweight RRQ message may be sent to all or a number of the gatekeepers on the alternate gatekeeper list simultaneously. A call signaling channel is then established between the first alternate gatekeeper to respond with a registration confirmation message, or to a selected gatekeeper where a number of gatekeepers provide an RCF message.