Clock Wander Compensation Using Pause Frames in Network Ports
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Solution Overview
Problem
Network devices with different local oscillators may have slightly different clock frequencies, leading to clock wander, which causes variations in transmission rates and can result in packet accumulation or loss, affecting network performance.
Innovation Solution
A network device with a clock wander compensation module that includes a global counter and port counters to detect and compensate for clock wander by transmitting pause frames based on counter differences, pausing data transmission when necessary to synchronize transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If network devices use local oscillators for data transmission, then each device can operate independently with its own clock frequency, but clock wander occurs causing different transmission rates and packet loss
Solution Approach 1:
The patent implements a feedback mechanism where the receiving device monitors the clock frequency difference between itself and the transmitting device using counters. When clock wander exceeds a threshold, the receiving device sends pause frames back to the transmitting device, which then adjusts its transmission rate. This closed-loop feedback system resolves the contradiction by maintaining independent operation while ensuring reliable data transmission through continuous clock synchronization.
2Ease of operation
If network devices transmit data at different transmission rates due to clock wander, then devices can operate with their own local oscillators, but packet accumulation or loss occurs
Solution Approach 1:
The patent applies preliminary action by having the receiving device detect clock wander and send pause frames before packet loss occurs. The pause frames proactively signal the transmitting device to slow down transmission, preventing buffer overflow and packet loss. This preemptive approach maintains operational simplicity while avoiding information loss.
Solution Approach 2:
The patent introduces pause frames as an intermediary control mechanism between the transmitting and receiving devices. These pause frames mediate the transmission rate adjustment, allowing devices to operate independently with their own oscillators while coordinating transmission rates to prevent packet loss. The pause frames act as a communication channel for clock synchronization without requiring direct oscillator coupling.
3Device complexity
If no clock wander compensation is implemented, then device complexity remains low, but transmission rate synchronization is poor leading to network performance degradation
Solution Approach 1:
The patent changes the transmission rate parameter dynamically based on detected clock wander. Instead of using a fixed transmission rate, the system adjusts the rate in response to clock frequency differences detected by counters. This parameter adaptation resolves the contradiction by maintaining low device complexity while improving network productivity through responsive transmission rate adjustment.
Data Source
AI summary
Aspects of the disclosure provide a network device. The network device includes a first port coupled to a first device to communicate with the first device, and a clock wander compensation module. The first port recovers a first clock based on first signals received from the first device. The clock wander compensation module includes a global counter configured to count system clock cycles based on a system clock of the network device, and a first port counter configured to count first clock cycles based on the recovered first clock. Further, the first port transmits a first pause frame to the first device based on the global counter and the first port counter.