Always Running Timer for Networking Device Forwarding Delay
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Solution Overview
Problem
Networking devices using commercial off-the-shelf (COTS) hardware face challenges in accurately measuring forwarding delay due to clock skew between internal timers, leading to errors in network performance tuning.
Innovation Solution
Incorporating an always running timer (ART) to capture timestamps simultaneously with internal clocks, allowing for accurate determination of forwarding delay by compensating for clock skew and improving timing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If internal clocks of transceiver are used to generate timestamps, then device complexity is reduced, but measurement precision deteriorates due to clock skew between internal timers
Solution Approach 1:
An external Always Running Timer (ART) is introduced as an intermediary timekeeping device. The ART serves as a neutral mediator that both the ingress and egress timestamps reference against, eliminating the clock skew problem between internal transceiver clocks while maintaining relatively simple device architecture.
2Measurement precision
If Always Running Timer (ART) is incorporated to capture timestamps, then measurement precision is improved by compensating for clock skew, but device complexity increases
Solution Approach 1:
The ART acts as an external intermediary time reference that both ingress and egress operations reference. This single external timer eliminates the need for multiple synchronized internal clocks, improving measurement precision while adding only one external component rather than multiple internal clock systems.
Solution Approach 2:
The solution moves the timekeeping function from the internal transceiver dimension to an external dimension. By placing the ART outside the transceiver, the system achieves accurate timing without the complexity of internal clock synchronization mechanisms.
3Productivity
If accurate timing information is obtained, then network performance is improved through better congestion prediction, but loss of time increases due to additional timestamp capture operations
Solution Approach 1:
The Always Running Timer is continuously operating before, during, and after packet transmission. By having the timer already running and ready, the system eliminates startup delays and can immediately capture timestamps without additional initialization time, thus minimizing time loss while providing accurate timing for network performance optimization.
Data Source
AI summary
A device, system, and method determines a forwarding delay through a networking device. The method is performed at the networking device including a transceiver and an always running timer (ART). The method includes generating a first timestamp using a first clock of the transceiver when a packet to be forwarded has been received. The method includes capturing a first ART time corresponding to the first timestamp. The method includes generating a second timestamp using a second clock of the transceiver when the packet to be forwarded has been transmitted. The method includes capturing a second ART time corresponding to the second timestamp. The method includes determining a forwarding delay based on the first and second timestamps and the first and second ART times.