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PRIORITY-AWARE HIERARCHICAL SCHEDULING FOR DETERMINISTIC ETHERNET

IP.com Disclosure Number: IPCOM000244657D
Publication Date: 2016-Jan-05
Document File: 5 page(s) / 46K

Publishing Venue

The IP.com Prior Art Database

Related People

Domenico Ficara: AUTHOR [+5]

Abstract

Techniques are presented herein by which Deterministic Ethernet traffic is prioritized in terms of jitter. This enables scheduling highly jitter-sensitive existing and new traffic in Deterministic Ethernet scenarios. In other words, these techniques enable prioritization of traffic flows in terms of the experienced jitter that they will experience. This techniques also enable the prioritization of flows that will come from newly attached devices to the network, without the need of re-computing the scheduling cycle.

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PRIORITY-AWARE HIERARCHICAL SCHEDULING FOR DETERMINISTIC ETHERNET

AUTHORS:

Domenico Ficara Salvatore Valenza

Roberto Muccifora Leo Caldarola

Davide Cuda

CISCO SYSTEMS, INC.

ABSTRACT

    Techniques are presented herein by which Deterministic Ethernet traffic is prioritized in terms of jitter. This enables scheduling highly jitter-sensitive existing and new traffic in Deterministic Ethernet scenarios. In other words, these techniques enable prioritization of traffic flows in terms of the experienced jitter that they will experience. This techniques also enable the prioritization of flows that will come from newly attached devices to the network, without the need of re-computing the scheduling cycle.

DETAILED DESCRIPTION

    In the context of industrial automation, Deterministic Ethernet has gained attention as a way to adopt widely used technology, such as Ethernet, for time critical and sensitive tasks such those that take place in factory plants and vehicles. Deterministic Ethernet promises no packet loss and deterministic reduced jitter for time sensitive traffic. This is accomplished through careful ad-hoc scheduling of streams that is mostly done off-line and often enforces some constraints to streams. Because of the time sensitivity and zero packet loss constraints, each node in a Deterministic Ethernet has to be synchronized with a main clock and bridges have to follow a specific scheduling.

    Usually an entity called PCE (Path Computation Element) that knows the topology, the constraints of the networks and the requirements of streams, is in charge of defining the path and the scheduling algorithm for each node of the network. Among all these constraints that make the scheduling a tougher job, there is also a simplification that relaxes the problem: in Deterministic Ethernet applications, streams are periodic, hence

Copyright 2016 Cisco Systems, Inc.
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stream scheduling can be solved within a time period and be repeated afterwards in a looped manner.

    Jitter control is paramount in these applications and can make or break a possible scheduling. This is not only due to the usual reason that the less jitter, the less buffering/memory is needed, hence less resources are needed in the platform. In Deterministic Ethernet application, delay sensitive flows can only be scheduled if a very well controlled jitter is possible.

Moreover, different applications (and hence traffic flows) in a Deterministic Ethernet network, can require different jitter limits.

    FIG. 1 below illustrates a technique by which flows going out on the same link are sorted according to their rate and grouped together in a Huffman tree structure. Data streams are assigned to time slots based on their data rates. First, a set of data streams is received and their corresponding data rates are used to generate a Huffman tree. For example, assume that data streams are used to generate the illustrative Huffman tree 700. In general, a Huffman tree is a frequency sor...