Store-and-Forward Buffer Latency Jitter Reduction
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Solution Overview
Problem
Existing network systems face significant delays in transmitting high-priority packets due to the use of single store and forward buffers handling mixed-priority traffic, where high priority packets are delayed as they wait for low priority packets to be drained, leading to increased latency and latency jitter, especially when the receiving environment has different timing requirements.
Innovation Solution
Implementing a system that controls the number of packets stored in a store and forward buffer by sending backpressure only when the buffer is full or exceeds a threshold, allowing for efficient forwarding of high priority packets by limiting the buffer to store a single large packet or multiple small packets, thereby minimizing average delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single store and forward buffer is used to handle mixed-priority traffic, then buffer utilization is maximized and device complexity is reduced, but high priority packets experience increased latency and latency jitter due to having to wait for low priority packets to be drained
Solution Approach 1:
The patent segments the single buffer into multiple virtual queues based on packet priority levels. Each queue maintains separate FIFO ordering, allowing high priority packets to be serviced before low priority packets without requiring physically separate buffers. This logical segmentation reduces latency jitter for high priority traffic while maintaining overall buffer utilization.
Solution Approach 2:
The patent applies different service policies to different regions of the buffer corresponding to different priority levels. High priority packets receive preferential treatment through dedicated queue management and early transmission opportunities, while low priority packets are serviced when buffer resources are available. This local quality differentiation resolves the latency contradiction without increasing overall device complexity.
2Loss of time
If backpressure is sent frequently to control buffer fullness, then latency jitter is reduced, but network throughput decreases due to increased backpressure overhead and transmission interruptions
Solution Approach 1:
The patent applies backpressure selectively rather than continuously. Backpressure is generated only when specific buffer thresholds are exceeded or when latency jitter thresholds are violated, rather than at every buffer full condition. This partial application of backpressure maintains latency control while minimizing throughput impact.
Solution Approach 2:
The patent dynamically adjusts backpressure thresholds based on buffer occupancy levels, traffic patterns, and latency requirements. By changing the parameters at which backpressure is applied, the system optimizes the balance between latency jitter control and network throughput, applying backpressure only when necessary to maintain performance.
Data Source
AI summary
Methods and apparatus for reducing the average delay associated with sending a packet from one environment to another via a store and forward buffer are disclosed. According to one aspect of the present invention, a method for processing transmission units received over a first network connection includes receiving a first transmission unit on the first network connection, storing the first transmission unit in a buffer, and determining when contents of the buffer meet a plurality of criteria. The method also includes sending a backpressure over the first network connection when it is determined that the contents of the buffer meet the plurality of criteria. In one embodiment, determining when the contents of the buffer meet a plurality of criteria includes determining when the contents of the buffer are of an amount that exceeds a threshold and determining when the contents of the buffer include at least one full packet.