A Master Course on Network Softwarization: Lectures and Practical Assignment

Hauser, Frederik

Menth, Michael

Schmidt, Mark

Publikationsserver der Universität Tübingen

A Master Course on Network Softwarization:Lectures and Practical AssignmentsFrederik Hauser, Mark Schmidt, Michael MenthChair of Communication Networks, University of Tuebingen, Tuebingen, GermanyEmail: {frederik.hauser,mark-thomas.schmidt,menth}@uni-tuebingen.de,I. MOTIVATIONThe bwNET100G+ research project focuses on innovatingcampus and scientific wide area networks using software-defined networking (SDN) and network function virtualization(NFV), two concepts that are also referred to as network soft-warization. In that context, Master students at the Universityof Tuebingen have the opportunity to work on prototypicalimplementations within thesis projects. Examples are [1]–[3].As such projects are demanding, students need a solidunderstanding of network softwarization and ideally havesome practical experience in that area. In the past, they wereinstructed to read scientific papers from the ONF reading list[4] and to program applications for SDN controllers usingtutorials such as [5] or [6]. However, this was rather inefficientas the process was difficult for the students and still requiredlots of individual supervision. Therefore, we established alecture course including practical assignments at Master levelas preparation for a thesis project on network softwarization.The course prerequisites basic knowledge in communicationnetworks. It provides an overview of legacy communicationnetwork management and introduces network softwarizationas novel and relevant development. It teaches both theoreticalfundamentals and implementation approaches, and discussesnew challenges in that field. Moreover, students get firstpractical experiences with virtualized SDN using Mininet andprogram SDN applications for the Ryu SDN controller. Whiletime-intense courses on network softwarization already exist[7], [8] at other institutions, our new course is tailored toa workload of only 3 ECTS including 90 hours of weeklylectures over 10 weeks during the summer term plus work onpractical assignments and exam preparation.II. CONCEPTThe concept of the course includes three parts: lectures,programming assignments, and a final exam.A. LecturesThe first part of the course focuses on theoretical educationin form of a lecture’s presentation that is based on slides. Thecontents are split up in seven chapters as following.1) Introduction to Network Softwarization: The first chap-ter covers the transition from legacy to softwarized networks.Legacy management concepts, e.g., SNMP and NETCONF,more active network concepts, e.g., ForCES and 4D, and morerecent concepts, e.g., OpenFlow SDN and P4, are discussed.2) OpenFlow: The second chapter focuses on coveringboth, the architecture and protocol of OpenFlow. The lectureintroduces OpenFlow in version 1.0 and 1.5.1. and shows thetransition from the first to the latest feature set while describingthe respective novelties such as flow table pipelines or meters.3) SDN Controller: The third chapter describes the SDNapplication and control layer. It covers the architecture, designprinciples, and control plane functions of SDN controllers andtheir interfaces along concrete implementations, e.g., REST fornorthbound interfaces. The chapter closes with an overview ofpupular SDN controllers, e.g., Ryu, OpenDaylight, and ONOS.4) SDN Switches: The fourth chapter revises the hardwarearchitecture of legacy routers and switches in the beginning.SDN software switches, Whitebox switches, OpenFlow-onlyswitches, and SDN hybrid switches and their respective de-ployment scenarios are described in detail afterwards. Thechapter closes with an in-depth view on the status quo.5) SDN Use Cases: The fifth chapter introduces datacenter,enterprise, campus and wide area networks as predestinedenvironments for the application of network softwarization.Especially benefits, but also limitation in comparison to legacytechnologies are discussed in detail. The chapter closes withan in-depth description of particular concepts from our currentand past research activities.6) Virtualization Techniques: The sixth chapter focuseson the strongly related concept of computer virtualization.Hypervisor-based and OS-level virtualization technologiesalong with concrete implementations are presented. Conceptsfor the orchestration of virtualized infrastructures and particu-lar concepts from our current and past research form the end.7) Network Function Virtualization: The seventh chapterintroduces the specifics of telecommunication provider net-works as motivation for the emergence of NFV. The mainpart of the lecture covers the ETSI NFV architecture with allrelevant details and discusses use cases. OPNFV is introducedas exemplary implementation of a NFV environment.B. Practical AssignmentsThe second part of the course focuses on practical experi-ences. Students are required to meet a total score of 60% intwo assignments to get an admission for the final exam. Scoresabove 60% are transformed into at most 10% bonus for thefinal exam grading. Teamwork skills were encouraged whilethe grading effort is limited by the requirement to work ingroups of two. Sessions for the practical assignments were partof the weekly course schedule, i.e., two lecture slots within thesemester were reserved. We published one assignment sheet atthe beginning of the course, another in the middle that needsto be finished within a time period of four weeks. It containstwo parts, a short group test and programming tasks.1) Group Test: The assignment sheets include a catalogueof 15 to 20 questions that are either related to contents ofthe lecture or to aspects of the assignment. Each student isrequired to give answers to five questions of the catalogue aweek after the assignment sheet was handed out. The grouptest verifies that both group members dealt with the relatedtheoretical questions prior to programming task work.2) Programming Tasks: In contrast to other courses, welimited the programming tasks on SDN application imple-mentation for Ryu. Therefore, the students learn to implementknown networking concepts, e.g., L2 switching or IP routing,using the capabilities of Ryu and OpenFlow-based SDN.The first programming task focuses on familiarization withMininet and Ryu by extending a L2 switch sample appli-cation to support port-based segmentation. The second pro-gramming assignment extends the L2 switch implementationwith IPv4 routing. Four hosts residing in two different IPsubnets are attached to a SDN switch which routes packetsbetween the subnets. Figure 1 shows the topology for thethird programming task. Eight hosts are conntected to twoSDN switches that act as IPv4 edge routers. Two additionalSDN switches acting as core routers represent the Internetbetween both networks. The edge and core routers are relatedto two different SDN controllers. The fourth programming taskfurthermore extends the routing functionality by introducinglongest prefix matching in a more complex routing scenarioand routing of IPv6 packets. In the last programming task,students implement packet- and flow-based IP anycast.Controller 1OpenFlow Switch 1Host 1 Host 2 Host 3 Host 410.0.1.1 10.0.1.2 10.0.1.3 10.0.1.4Subnet10.0.1.25410.10.0.1Host 5 Host 6 Host 7 Host 8OpenFlow Switch 210.0.2.1 10.0.2.2 10.0.2.3 10.0.2.4Subnet10.0.2.254OpenFlow Switch 4OpenFlow Switch 310.10.0.210.11.0.110.11.0.210.12.0.210.12.0.1InternetOpenFlowProtocolController 2OpenFlowProtocolFig. 1: Network topology for an IPv4 routing scenario with 8 hosts, 4OpenFlow switches, and 2 SDN controllers.To simplify the work on the programming assignments,we provided the NetSoft-VM, a virtual machine image asuniform programming and execution environment. We choseVirtualBox as virtualization platform as it can be installedon Windows, macOS, and Linux. The NetSoft-VM is basedon Ubuntu 17.04 with XFCE and contains Mininet, MiniEditas GUI for Mininet, Python 3, the Ryu SDN controllerframework, and the Atom editor. Figure 2 shows the NetSoft-VM running in VirtualBox with MiniEdit as GUI for theMininet network simulator.Fig. 2: Netsoft VM in VirtualBox with MiniEdit as GUI for the Mininetnetwork simulation environment.Successfully passing the group test was set as requirementfor the grading of the programming tasks. The grading focusedon source code functionality and quality.C. Final ExamDue to a limited number of participating students, wedecided not to offer a written final exam. Instead, we chosethe format of an oral exam with 25 minutes per student.REFERENCES[1] M. Menth, M. Schmidt, D. Reutter, R. Finze, S. Neuner, and T. Kleefass,“Resilient Integration of Distributed High-Performance Zones into theBelWue Network Using OpenFlow,” IEEE Communications Magazine(Commag), vol. 55, no. 4, Apr. 2017.[2] F. Hauser, M. Schmidt, and M. Menth, “Establishing a Session Databasefor SDN Using 802.1X and Multiple Authentication Resources,” in IEEEInternational Conference on Communications (ICC), Paris, France, Jun.2017.[3] M. Schmidt, R. Finze, D. Reutter, and M. Menth, “Demo: ResilientIntegration of Distributed High-Performance Zones into the BelWueNetwork Using OpenFlow,” in International Teletraffic Congress (ITC),Wuerzburg, Germany, Sep. 2016.[4] “Open Networking Foundation: SDN Reading List,” https://www.opennetworking.org/sdn-resources/sdn-reading-list, accessed: 2017-08-06.[5] “Mininet Walkthrough,” http://mininet.org/walkthrough/, accessed: 2017-08-06.[6] “Ryu Documentation: Getting Started,” http://ryu.readthedocs.io/en/latest/getting_started.html, accessed: 2017-08-06.[7] “Coursera: Software Defined Networking,” https://www.coursera.org/learn/sdn, accessed: 2017-08-06.[8] “Princeton University: COS-597E, Fall 2013: Software Defined Network-ing,” http://www.cs.princeton.edu/courses/archive/fall13/cos597E/index.html, accessed: 2017-08-06.

A Master Course on Network Softwarization: Lectures and Practical Assignments

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A Master Course on Network Softwarization: Lectures and Practical Assignments

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