Masterthesis: In-network Packet Priority Adaptation for Networked Control Systems

Stephan Zinkler - 2016

Introduction

This repository contains all relavant implementations developed as a part of the masterthesis for "In-network Packet Priority Adaptation for Networked Control Systems" at the Distributed Systems Department, Insititue for Parallel and Distributed Systems (IPVS) at the university of Stuttgart.

Abstract

Sharing the network between Networked Control System (NCS) having strict demands with respect to latency and jitter and applications only requiring best-effort service leads to multiple problems. An important task to consider is how to prioritize individual types of traffic in such a way that the necessary guarantees for an NCS to be stable can still be given. While there are ways to prioritize the more important control traffic of an NCS over best-effort traffic sharing the same network, a more sophisticated approach has to be found in order to handle multiple NCS sharing the highest priority. In this thesis, in-network priority scheduling applications with a global view on the network are developed in order to schedule and prioritize individual NCS such that their stability can be guaranteed while sharing the network between multiple NCS.

This thesis deals with in-network packet priority scheduling for Networked Control Systems. Using Data Plane Development Kit (DPDK) to achieve a Network Function Virtualization (NFV) based approach, a priority scheduling application is implemented in a middlebox to handle continuous priorities. This application could be instantiated and migrated within the network while simultaneously using Software Defined Networking (SDN) to route the traffic to the respective nodes. Additionally, this approach is extended using SDN and OpenFlow to adapt priorities in-network. Using the eight internal per- port queues of a switch, discrete priorities are used to schedule, and additionally adapt, the priorities on the switch. This approach could give the opportunity for priority-based routing by using the SDN-controller for routing decisions and configuring the switches.

The evaluation of this thesis is done by simulating NCSs and emulating the network containing the middlebox. For this, a simulation of an inverted pendulum is implemented for which the use of DPDK is compared to standard sockets. It can be shown that DPDK is able to perform better due to less delay and jitter. The scheduling application is evaluated by comparing it to a round-robin scheduling approach. The result suggests that the application is able to keep multiple NCS more stable than it’s round-robin counterpart. Furthermore, it is able to stabilize a more unstable system faster and more effectively. While the maximum sampling time for a system with a pendulum having an initial angle of 35° was found to be 50ms for the round-robin scheme, the middlebox is able to keep the system stable until 120ms. The application using OpenFlow is evaluated with respect to the time it takes to configure the switch as well as the overhead imposed by the configuration compared to the number of NCS within the network

Folder Structure

• Adaptation: Contains the In-network Packet Priority Adaptation OpenFlow library
• NCS_Simulation: Contains both the DPDK sender/receiver application and the Networked Control System simulation library
• Priority_Scheduling: Contains the priority scheduling dpdk application as well as the round robin counterpart.

Required Packages

• Python Packages
• Ryu
• DPDK
• Armadillo (C++)