Router EF-on-EF Jitter Monitoring via Queue Depth Counters
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Solution Overview
Problem
Measuring per-hop EF-on-EF jitter in data streams passing through network routers or switches is challenging due to the difficulty in tracking queue depths for multiple streams, which affects the ability to monitor and manage jitter within acceptable limits, especially in priority queues where multiple EF packet streams interact.
Innovation Solution
The method involves setting a maximum bound on EF-on-EF jitter and using the queue depth at enqueue times to determine packets that could have jitter greater than a set value, with counters to track packets enqueued at depths exceeding a threshold, allowing for the calculation of jitter fractions and enabling corrective actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple EF packet streams share a single output queue, then network resource utilization is improved, but jitter measurement precision deteriorates because it becomes impossible to track queue depths for all streams individually
Solution Approach 1:
The patent segments the monitoring function by creating separate counters for each EF stream (C1, C2, C3) that independently track packets enqueued at different queue depth thresholds. This allows jitter monitoring for multiple streams sharing a single queue without requiring individual queue depth tracking for each stream, thus maintaining measurement precision while preserving resource utilization benefits.
Solution Approach 2:
The patent introduces intermediary counters as mediators between the shared EF queue and the monitoring function. These counters indirectly measure jitter by counting packets enqueued at specific depth thresholds, serving as an intermediary mechanism that enables jitter measurement without direct queue depth tracking for each stream.
2Reliability
If endpoint buffering is increased to accommodate jitter, then jitter tolerance is improved, but latency increases which violates endpoint buffering limits
Solution Approach 1:
The patent implements feedback by monitoring jitter at intermediate network nodes and providing information to service providers about jitter conditions. This feedback mechanism enables proactive jitter management and corrective actions before endpoint buffering limits are exceeded, allowing minimal endpoint buffering while maintaining jitter tolerance through network-side monitoring and control.
3Measurement precision
If queue depth tracking is implemented for all EF streams, then jitter measurement accuracy is improved, but device complexity increases significantly
Solution Approach 1:
The patent extracts the essential monitoring information (packets enqueued at specific depth thresholds) from the complex queue management system. By using simple counters that only increment when packets are enqueued at or below certain depth thresholds, it extracts the necessary jitter measurement data without implementing full queue depth tracking for all streams, thus maintaining measurement accuracy while reducing device complexity.
Data Source
AI summary
A system for monitoring EF-on-EF jitter in a network node having an EP output queue into which EF packets are entered comprises a first counter that counts the packets entering the queue and also a second counter that counts the packets entering the queue when the queue depth is greater than an operator-determined maximum depth, whereby the operator can compare the two counts to determine the proportion of packets that might be subject to jitter corresponding to the maximum depth. Preferably, the system also includes a third counter that counts the number of packets entering the queue when the queue depth exceeds an alarm depth greater than the maximum depth.