Priority Switching Scheduler
draft-finzi-priority-switching-scheduler-01

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Internet Engineering Task Force                                    Baker
Internet-Draft
Intended status: Informational                                     Finzi
Expires: September 6, 2018                                       Frances
                                                                  Lochin
                                                                Mifdaoui
                                                            ISAE-SUPAERO
                                                           March 5, 2018

                      Priority Switching Scheduler
              draft-finzi-priority-switching-scheduler-01

Abstract

   We detail the implementation of a network scheduler that switches the
   priority of one or several queues.  This scheduler aims at carrying
   and isolating time constrained and elastic traffic flows from best-
   effort traffic.  We claim that the usual implementations with rate
   schedulers (such as WRR, DRR,...) do not allow to efficiently
   quantify the reserved capacity of the different classes.  By using
   this credit based scheduler mechanism called Priority Switching
   Scheduler, we provide a more predictable available capacity.

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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents

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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Context and Motivation  . . . . . . . . . . . . . . . . .   2
     1.2.  Priority Switching Scheduler in a nutshell  . . . . . . .   2
   2.  Priority Switching Scheduler  . . . . . . . . . . . . . . . .   3
     2.1.  Specification . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Implementation  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Usecase: benefit of using PSS in a Diffserv core network  . .   6
     3.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  New service offered . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

1.1.  Context and Motivation

   To share the capacity offered by a link, many fair schedulers have
   been developed, such as Weighted Fair Queueing, Deficit Round Robin.
   However, with these solutions, the capacity available to a class is
   strongly impacted by the other classes.  With this new scheduler
   denoted Priority Switching Scheduler (PSS), we wish to reduce this
   impact on some classes and provide them with a more predictable
   output rate, reporting the impact on other classes.  Additionally,
   compared to well-known schemes, this solutions is simpler to
   implement as it does not require a virtual clock, and more flexible
   thanks to the many possibilities offered by the setting of different
   priorities.

1.2.  Priority Switching Scheduler in a nutshell

   The principle of PSS is the use of credit counters to change the
   priority of one or several queues.  For each switching queue q, its
   priority, denoted p[q], switches between two values, depending on its
   associated credit counter.  Then classic Priority Scheduler is used
   for the dequeuing process.

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   The main idea is that changing the priorities adds fairness to the
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