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A DIY DPDK Software Router for Networking Education

Sebastian Gallenmüller, Stefan Lachnit, Manuel Simon

arXiv:2610.29625v1cs.NI

TL;DR

Networking curricula offer limited exposure to the performance considerations and low-level choices of production packet processing. This paper describes a semester-long DPDK software-router project and its course infrastructure, reporting student feedback and releasing materials for reuse.

  • Problem

    Educational tools based on emulation or Raspberry Pi hardware do not reflect multicore scalability and low-level optimizations relevant to real-world networking performance.

    Source: §I · p. 1

  • Method

    The course project has master’s students implement and evaluate a DPDK software router, using multithreaded design and a virtualized development environment.

    Source: §I · p. 1, B. Problem 2: Design and Implementation · p. 3, §IX · p. 6

  • Results

    11 out of 35 participating students in the 2023 and 2024 winter semesters re-entered the project, and the survey reported no complaints about using C or C++.

    Source: E. Pedagogical Design Considerations · p. 6

  • Takeaways & Limitations

    The project materials and scripts are released to support replication and further refinement by the community.

    Source: §IX · p. 6

    LLMs can solve the exercises with consistently high grades, and there is currently no practical way to reliably detect or prevent their use.

    Source: §VII · p. 6

Abstract

from arXiv · show

High-performance packet processing frameworks, such as the Data Plane Development Kit (DPDK), are widely used in modern network systems, yet they are rarely integrated into networking curricula. As a result, students often lack exposure to the performance considerations and low-level design choices that shape real-world packet processing systems. We describe a semester-long course project in which students implement a do-it-yourself (DIY) software router using DPDK in a master-level computer networking course. The project guides students through the design and implementation of a multithreaded router, the development of a routing table data structure, and the evaluation of forwarding performance using standard benchmarking tools. We present the project structure and the virtualized infrastructure used to support classes of realistic size. Based on several iterations of the course and survey feedback from participating students, we discuss the observed workload, learning outcomes, and challenges of teaching high-performance packet processing. We release the project material and scripts to recreate the infrastructure, enabling reuse and further refinement by the community.

I. INTRODUCTION

The project brings production-grade DPDK packet processing into a semester-long master’s course through implementation and performance evaluation of a software router. It addresses the gap between educational tools and real-world performance concerns, while providing infrastructure and materials for course-scale use.

I. INTRODUCTION

  • Existing educational tools based on emulation or Raspberry Pi hardware do not reflect multicore scalability and low-level optimizations needed for real-world performance.This leaves a gap between networking classes and real-world contexts.Source: §I · p. 1
  • Students implement a DPDK software router in a semester-long master’s project, applying multithreaded design, low-level protocol work, and performance-critical routing structures.The project complements the Advanced Computer Networking lecture with practical implementation and evaluation for students with prior networking knowledge.Source: §I · p. 1
  • The project targets students who have selected networking as a focus area and aims to expose them to production-grade packet processing and performance-critical design choices.The stated goals include implementing a complete router in one semester and working with multithreading, memory management, or multiqueue NICs.Source: §I · p. 1
  • The authors provide per-student repositories, detailed instructions, and Vagrant scripts to deploy a four-node topology, alongside workstation access for less-experienced users.The workstation and scripts support deployment of the project environment.Source: §I · p. 3

IV. PROJECT AND ASSIGNMENT DESIGN

The project divides seven learning goals across four problems, progressing from tools and setup to router implementation, high-performance routing tables, and benchmarking.

IV. PROJECT AND ASSIGNMENT DESIGN

  • The four problems progress from tools and setup (P1) to basic router operations (P2), high-performance routing tables (P3), and router benchmarking (P4).Together, the problems cover seven learning goals.Source: §IV · p. 3
  • The practical assignments target higher levels of Bloom’s Taxonomy, while the lecture covers remembering and understanding.The project separates learning goals into tasks aligned with the taxonomy.Source: §IV · p. 3
  • P1 familiarizes students with the tools and setup, and P2 has them implement basic router operations.These precede the routing-table and benchmarking problems.Source: §IV · p. 3

A. Problem 1: Fundamental Tools and Setup

Problem 1 prepares students to work in a realistic Linux VM environment and configure, test, and observe the experiment network.

A. Problem 1: Fundamental Tools and Setup

  • Students use ssh, git, ping, and tcpdump in GUI-free Linux VMs to configure the environment, submit scripts, and test network setup.The authors selected familiar tools but retained a realistic Linux environment rather than a simplified exercise setting.Source: A. Problem 1: Fundamental Tools and… · p. 3
  • Students configure client NICs with ip and router NICs with DPDK tools, then submit scripts that reproduce the setup on a fresh VM.The exercise framework includes additional router implementation files and an unmodified DPDK v24.11 LTS.Source: A. Problem 1: Fundamental Tools and… · p. 3
  • Students test their scripts by pinging between the clients while a DPDK forwarder runs on the router, then observe the network with tcpdump.They submit their observations.Source: A. Problem 1: Fundamental Tools and… · p. 3

B. Problem 2: Design and Implementation

Problem 2 has students implement IPv4 forwarding with DPDK, including protocol handling and a multithreaded architecture. The design leaves substantial implementation freedom while fixing selected interfaces and requirements.

B. Problem 2: Design and Implementation

  • Students implement IPv4 forwarding and Layer 2 and 3 protocols from scratch using DPDK, extracting protocol information from an RFC.The router’s core functionality handles IPv4 packets.Source: B. Problem 2: Design and Implementation · p. 3
  • The proposed router uses three threads, one per interface, with each thread managing one receive queue and three transmit queues to avoid synchronized NIC access.The exercise presents multithreading and synchronization avoidance as general high-performance packet-processing concepts, not DPDK-only ideas.Source: B. Problem 2: Design and Implementation · p. 3
  • Students implement RFC 1812 IPv4-header checks, while ICMP implementation is not required to keep complexity manageable.The routing table is initially represented by hard-coded forwarding decisions.Source: B. Problem 2: Design and Implementation · p. 3
  • Beyond the routing-table interface and command-line arguments, students have considerable freedom, requiring them to test their implementations in a setting with few fixed constraints.The project frames this as practice with realistic systems, where behavior is often loosely defined, including correct memory handling.Source: B. Problem 2: Design and Implementation · p. 3

C. Problem 3: Routing Table

Problem 3 has students implement the DIR-24-8 routing-table algorithm introduced in the lecture, then test their implementation with intentionally limited provided tests. The exercise emphasizes low-level data structures and designing tests for edge cases.

C. Problem 3: Routing Table

  • Students implement the DIR-24-8 routing-table algorithm, applying lecture concepts to a low-level data structure.The lecture provides the background needed for implementation.Source: C. Problem 3: Routing Table · p. 3
  • The framework supplies a routing-table interface and rudimentary tests, but intentionally limits test cases and encourages students to add their own.This is intended to prevent a test-dominated workflow from displacing reflection on implementation changes.Source: C. Problem 3: Routing Table · p. 3
  • Testing edge cases helps detect low-level hardware-optimized programming errors such as out-of-bound accesses.The exercise teaches students to design effective tests for a specific implementation, broadening skills often neglected in courses focused on high-level concepts or software engineering.Source: C. Problem 3: Routing Table · p. 4

D. Problem 4: Benchmarking Software Routers

Problem 4 has students measure and evaluate the forwarding throughput of the software router built in Problems 2 and 3. The benchmark uses iperf3 and asks students to examine measurements across packet rates and sizes.

D. Problem 4: Benchmarking Software Routers

  • Students benchmark the router built in Problems 2 and 3, learning to perform and evaluate scientific measurements with standard tools.The benchmark is inspired by RFC 2544 for evaluating network interconnect throughput.Source: D. Problem 4: Benchmarking Software… · p. 4
  • iperf3 on Clients 1 and 2 measures router forwarding at specified packet rates and packet sizes.Students plot measured ingress and egress packet rates using a provided Jupyter notebook and matplotlib.Source: D. Problem 4: Benchmarking Software… · p. 4
  • Students describe their observations and discuss whether packet rate or packet size is more important.This discussion follows their performance measurements.Source: D. Problem 4: Benchmarking Software… · p. 4

E. Pedagogical Design Considerations

The project balances a challenging, production-oriented router exercise with structures intended to fit a semester and support continued participation. Students use C or C++ with DPDK, while the course limits router functionality and provides grading, re-entry, and VM recovery measures.

E. Pedagogical Design Considerations

  • Students have about four weeks per problem and earn up to 10 credits, with P2 and P3 accounting for 75% of available credits.P4 is shorter because students have less time during the end-of-semester exam period.Source: E. Pedagogical Design Considerations · p. 4
  • A final-exam grade bonus rewards project participation, with the maximum bonus available at 75% or more of project credits.The project is intentionally challenging, and the bonus threshold is designed to encourage participation.Source: E. Pedagogical Design Considerations · p. 4
  • The router supports only a minimum subset of ARP/IPv4 and no ICMP, while retaining high-speed parallel architecture, header parsing, and longest-prefix matching.The functionality is limited to reduce complexity within a one-semester timeframe without limiting the learning objectives.Source: E. Pedagogical Design Considerations · p. 4
  • C and C++ were chosen over a scripting-language abstraction because scripting would diverge from real-world systems and complicate bit-level routing-table operations.The authors note that dynamic typing can require extra casting or functions for these operations.Source: E. Pedagogical Design Considerations · p. 4
  • The project combines production-grade DPDK and real-world infrastructure with the development of practical system skills.Source: E. Pedagogical Design Considerations · p. 6
  • The authors report being surprised that the survey contained no complaints about requiring C or C++, despite students’ limited bachelor-level exposure.Source: E. Pedagogical Design Considerations · p. 6
  • In the 2023 and 2024 winter semesters, 11 of 35 participants used the option to re-enter the project.The authors recommend allowing re-entry; students can resume later problems without necessarily completing earlier ones first.Source: E. Pedagogical Design Considerations · pp. 4, 6
  • Student-controlled setup scripts were introduced after VM lockouts delayed students who needed teaching-assistant help to regain access.The scripts let students delete and recreate VMs; the authors recommend reset and restore capabilities to reduce teaching-assistant load.Source: E. Pedagogical Design Considerations · p. 6

VII. USE OF AI

The project predates the rise of LLMs, which can now solve its exercises with consistently high grades and cannot currently be reliably detected or prevented. The course uses a closed-book final exam to assess students’ own understanding while allowing responsible LLM use for coding.

VII. USE OF AI

  • LLMs can now solve all described exercises with consistently high grades, and there is currently no practical way to reliably detect or prevent their use.Source: §VII · p. 6
  • A closed-book final exam without books, lecture materials, or LLM access determines whether students earn the project bonus.The bonus applies only if students pass the exam without it.Source: §VII · p. 6
  • The controlled final assessment is intended to let students use LLMs responsibly for tasks such as coding without passing without understanding the central concepts.Source: §VII · p. 6

VIII. REPRODUCIBILITY

The project releases materials for others to offer the software-router course, while withholding grading materials to preserve fairness for future participants.

VIII. REPRODUCIBILITY

  • The released materials support offering the software-router project as part of another lecture.They include a detailed project description, infrastructure setup code, and the DPDK framework.Source: §VIII · p. 6
  • The release includes code to set up the infrastructure and the DPDK framework.These accompany the detailed project description.Source: §VIII · p. 6
  • Grading materials are withheld to preserve a fair opportunity for future participants.The authors plan to continue offering the project in upcoming semesters.Source: §VIII · p. 6

IX. CONCLUSION

The paper presents a semester-long master’s course project in which students build a software router using DPDK in a production-grade virtualized environment. It emphasizes performance optimization and releases artifacts to support reuse and further development.

IX. CONCLUSION

  • Students gain hands-on experience designing and developing a software router during a one-semester master’s networking course.The project uses a production-grade, virtualized environment and real-world frameworks and tools.Source: §IX · p. 6
  • The project centers performance optimization, unlike teaching projects that prioritize simplicity and accessibility.It uses DPDK and describes infrastructure for a virtualized development environment serving an approximately 30-student master’s course.Source: §IX · p. 6
  • The authors release all artifacts to support replication, reuse, and further development of the course project.They hope the community will draw inspiration from the project and continue its development.Source: §IX · p. 6
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