Centralized Congestion Avoidance in Passive Optical Networks
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Solution Overview
Problem
Existing communication networks in passive optical networks face challenges in dynamically avoiding congestion, leading to network delays and quality of service degradation due to oversubscription, where standalone congestion handling methods are costly and ineffective.
Innovation Solution
A centralized congestion avoidance method is implemented in an Optical Line Terminator (OLT) using a dynamic bandwidth allocation mechanism and feedback mechanism to periodically adjust bandwidth allocation and packet-drop commands based on queue fill levels and upstream traffic analysis, providing dynamic congestion avoidance for multiple optical network termination devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standalone congestion handling methods are used in passive optical networks, then congestion avoidance is provided, but device complexity and cost increase
Solution Approach 1:
The patent merges the congestion avoidance function with the existing Dynamic Bandwidth Allocation (DBA) mechanism in the OLT. The DBA grant structure is extended to include congestion control parameters, combining bandwidth allocation and congestion management into a single centralized function, thereby avoiding additional device complexity at customer premises
Solution Approach 2:
The OLT's DBA mechanism is enhanced to perform multiple functions: bandwidth allocation, queue management, and congestion avoidance. By making the DBA grant universal for these purposes and using the existing ONT feedback mechanisms, the system avoids deploying specialized standalone congestion handling devices
2Reliability
If static bandwidth allocation is used, then network capacity is guaranteed, but network adaptability to congestion conditions deteriorates
Solution Approach 1:
The patent implements dynamic bandwidth adjustment within each DBA grant period. The OLT calculates adjusted bandwidth allocations based on real-time queue fill level feedback from ONTs, allowing the system to adapt bandwidth distribution to current network conditions while maintaining the structured allocation framework
Solution Approach 2:
The system dynamically changes bandwidth allocation parameters based on congestion conditions. When queue fill levels indicate approaching congestion thresholds, the OLT adjusts bandwidth parameters to prevent congestion, and when conditions improve, restores higher bandwidth allocations, making the network adaptive to varying load conditions
3Ease of operation
If centralized congestion control is implemented, then network management is simplified, but response time to congestion conditions increases
Solution Approach 1:
The system uses periodic feedback mechanisms where ONTs report queue fill levels at the end of each DBA grant period. This periodic operation simplifies centralized control by using regular intervals rather than continuous monitoring, while the rapid periodic cycles maintain effective response time
Solution Approach 2:
The OLT proactively adjusts bandwidth allocations based on predicted congestion conditions rather than reacting after congestion occurs. By using queue fill level information and applying congestion avoidance algorithms in advance during the DBA calculation phase, the system prevents congestion before it impacts performance
Data Source
AI summary
In one aspect, a method for congestion avoidance in a passive optical network having an optical line terminal communicatively connected to a plurality of optical network termination devices is provided. A dynamic bandwidth allocation information is periodically requested from the optical network termination device and the optical line terminator receives the response to the request. An adjusted bandwidth allocation for the optical network termination device is determined by the optical line terminator. The optical line terminator determines a packet-drop command to be taken at the optical network termination device. The adjusted bandwidth allocation and the packet-drop command are sent to the optical network termination device.