Analysis of Dampers in Time-Sensitive Networks with Non-ideal Clocks

TL;DR

This paper provides a comprehensive taxonomy and analysis of dampers in time-sensitive networks, accounting for non-ideal clocks, and offers formulas for residual jitter bounds to improve network timing performance.

Contribution

It introduces a general framework for analyzing all types of dampers with non-ideal clocks, including formulas for residual jitter bounds and insights into their effects on packet reordering.

Findings

Non-FIFO dampers can cause packet reordering due to clock non-idealities.

FIFO dampers combined with non-FIFO network elements can significantly degrade performance.

The analysis applies to various network configurations and is demonstrated through an industrial case study.

Abstract

Dampers are devices that reduce delay jitter in the context of time-sensitive networks, by delaying packets for the amount written in packet headers. Jitter reduction is required by some real-time applications; beyond this, dampers have the potential to solve the burstiness cascade problem of deterministic networks in a scalable way, as they can be stateless. Dampers exist in several variants: some apply only to earliest-deadline-first schedulers, whereas others can be associated with any packet schedulers; some enforce FIFO ordering whereas some others do not. Existing analyses of dampers are specific to some implementations and some network configurations; also, they assume ideal, non-realistic clocks. In this paper, we provide a taxonomy of all existing dampers in general network settings and analyze their timing properties in presence of non-ideal clocks. In particular, we give formulas for computing residual jitter bounds of networks with dampers of any kind. We show that non-FIFO dampers may cause reordering due to clock non-idealities and that the combination of FIFO dampers with non-FIFO network elements may very negatively affect the performance bounds. Our results can be used to analyze timing properties and burstiness increase in any time-sensitive network, as we illustrate on an industrial case-study.