IPv4 Experts in Germany

• Technical leadership across hardware, firmware, and software teams; scope: hardware/firmware team (4 people) and leadership group (5 people)
• Consolidated and documented a product family that had grown over more than 15 years and aligned it with CRA compliance — from the bare-metal I/O module to the cloud interface.
• Provided the most important customer product with the essential requirements and architecture documentation within two months — for a firmware landscape that had grown over more than 15 years. It now supports the customer’s modernization strategy.
• Established a monthly reporting line to the supervisory board and executive board within three months: nine meetings since 12/2025. The report itself is versioned and built from the CI pipeline; it is based on automatically collected activity and release data instead of assessments.
• Built a container-based CI/CD infrastructure from scratch: cross-compilation, host tests, and documentation builds in one continuous pipeline.
• Introduced declarative QA gates for DevOps and development artifacts — from the start using lefthook instead of pre-commit, executed in a dedicated container image.

Technologies used: arc42, req42, tpo42, docToolchain, PlantUML, ArchiMate, C4 model, ADR, C, C++ (GTest), CMake, Bare Metal (ARM Cortex-M3/M7), OCI containers, Jenkins, lefthook, Prometheus, Grafana, SBOM, CRA, OPC, SCADA, PLC integration, IPv6 migration, Zero Trust, Sociocracy 3.0, Cynefin

• Elevator emergency call reorganization project: Project to evaluate and define a new technical solution for connecting elevator emergency calls for all facilities of DB InfraGO passenger stations.

• Objectives: Secure, redundant connection of all locations across Germany. Definition of the technical solution, documentation, subject-matter support and management of specialist and line organizations.

• Identification and commissioning of technical solutions.

• Management of documentation and approval of the technical solution in DB regulations.

• Definition and tracking of the roadmap for describing the solution.

• Preparation of a rollout plan to avoid shutdowns.

• Coordination and implementation of decision proposals for steering committees.

• Communication of the solution to all committees and regional areas.

• Analysis of the existing CAN communication between microcontrollers
• Analysis of the sensors used and the measured values collected
• Planning the CAN messages for transmitting the measured values
• Iterative adjustment of the microcontroller code to the new CAN messages
• Cross-compilation from x64 to arm64

• Modernization of a large-scale Java enterprise application*

The project is modernizing a complex enterprise application that has grown over many years. The existing Spring-based legacy system runs on Java 8, OSGi, and Eclipse RCP and is being gradually migrated to a modern, maintainable architecture with Java 25 and Quarkus.

Marcus works on analysis, architecture, refactoring, and implementation. One focus is on untangling historically grown structures and dependencies and on building a clean, sustainable Java and Quarkus technology stack.

Tools & technologies: Java 8, Java 25, Quarkus, Hibernate ORM with Panache, EclipseLink, OSGi, Eclipse RCP, Maven, JUnit, Mockito, REST, JSON, Git, Eclipse IDE, IntelliJ IDEA Ultimate, Jira, Confluence

Temporary employment

• System black-box integration tests (BBIT, IVVQ): Execution of regression, release, acceptance, and compliance tests for safety-critical brake control units in the rail industry
• Software test application & integration: Runtime configuration of software components and libraries, validation of interfaces, configuration dependencies, and component interactions
• Test automation (FEAT framework): Co-development and further development of an automated test framework for test execution, reporting, and result analysis
• Functional safety (SiL4, FuSi): Ensuring compliance with safety requirements, traceability and coverage, as well as standards compliance according to EN50126/28/29
• Test automation for communication components: Configuration and validation of fieldbus (CAN) and Ethernet-based TCMS data communication interfaces (TRDP and CIP)
• Requirements analysis & shift-left (PTC Windchill ALM): Analysis of software and system artifacts to identify gaps, ambiguities, and redundancies early in the SDLC
• Test design & test case development: Derivation of test conditions, coverage strategies, and implementation of data-driven test cases (DDT), including reusable test data fixtures
• CI/CD & automation (Python, PowerShell, Jenkins, SVN): Automation of build, test, and HIL deployment processes as well as integration into CI/CD pipelines
• Test data & configuration management (XML): Maintenance and adaptation of XML test vectors and system configurations with automated integration into test environments
• Non-functional testing: Execution of performance and load tests to assess stability and system behavior
• Agile development & defect management (JIRA, Confluence): Participation in Scrum teams, test coordination, review of test artifacts, as well as defect tracking and root-cause analysis
• Error analysis & debugging (CANoe, CANalyzer): Analysis of errors and message flows across multiple system layers (application to bus)
• Model-based analysis (UML, Enterprise Architect): Specification of SUT/SOW and support for systematic test control
• Process & test documentation: Creation of integration and test documentation according to internal quality and certification requirements

• As-is assessment of the current network infrastructure and its documentation, including on-site inspections
• Independent planning of new distribution and main distribution rooms in the individual district offices (components used, rack layout, connectivity), considering the BSI IT-Grundschutz and InfoSic requirements
• Planning of new copper and fiber optic cabling, including patch panels
• Coordination with building services engineering (TGA) to ensure compliance with relevant on-site requirements
• Development of detailed execution plans and high-level concepts for the rollout of the new infrastructure
• Additional support after the components go live (hypercare phase)
• Regular communication with project management and client stakeholders

• PRISMA project
• Ansible automation
• Windows third-level support for Windows NT, Windows 2000, Windows 2013, Windows 2016, Windows 2019

Participation in various projects related to the development and introduction of new telecommunications products in the mobile communications and fixed-line sectors, with a focus on 5G, wholesale and IPv6 technologies.

• Planning, coordination and execution of product development projects, particularly in the 5G and fixed-line environments
• Support for the rollout of new offerings, including test management and quality assurance
• Participation in the development of wholesale products and eSIM solutions
• Close coordination with internal departments (technology, marketing, operations) and external partners
• Use of agile tools and methods for project management and collaboration

Tools: JIRA, MS Office, MS Project

Technologies: 5G, 5G Campus Networks, Fixed Network (FixNet), IPv6, eSIM, Wholesale product development

CS-APN 5G NSA – IPv6 / Dual-Stack for B2B Customers

Ensuring the use of CS-APNs in dual-stack mode (IPv4/IPv6) in combination with MPLS VPN and IPSEC VPN.

• Project management including test planning, test coordination and go-live management
• Technical coordination for activating IPv6 functionality for B2B connections

eSIM Manager – Product Development for B2B Customers

Development of a tool for the fast and scalable provision of eSIM profiles for business customers.

• Product design and process definition for activating eSIMs on different device types (smartphones, IoT, laptops)
• Collaboration with partners to integrate the solution into existing infrastructures

eSIM Handling B2B – Blanco eSIM Process Integration

Optimization of the eSIM provisioning process through the introduction of dynamic Blanco eSIM processes.

• Definition of new processes for issuing non-activated eSIMs (Blanco) via the frontend and partner community
• Design of the integration into service and IT systems

All-IP 5G NSA – Mobile Access for B2B Internet/Voice Services

Expansion of the All-IP portfolio with mobile 5G access offering higher bandwidth for business customers. (5G Indoor Coverage).

• Project management including test management and go-live preparation
• Interface coordination for introducing Local-SIM-based solutions

5G PN – Campus Roaming / Private Networks

Development and introduction of 5G Private Network (PN) solutions with a focus on industrial applications (IIoT).

• Design and definition of business use cases
• Development of SIM/eSIM processes for 5GPN, including roaming between private and public networks

IPv6 for B2B – Introduction in Mobile and Fixed-Line Products

Introduction of IPv6 support for All-IP products and M2M services in the B2B environment.

• Product and process development for integrating IPv6 (in accordance with RIPE-554)
• Implementation for large customers such as retail chains with several thousand branches in Germany and abroad

• Requirements analysis and replacement of local SharePoint as CMDB with open source NetBox to prepare for deploying Cisco ACI (SD-WAN) with Microsoft Azure
• Coordination with systems like Checkmk and Grasp
• Introduction and coordination of cmdbsyncer as CMDB data hub; further development of the syncer with Kuhn & Ruess GmbH
• Implementation of SNMPv3 on AIX LPAR/VIO, Linux, Windows, SAN/storage, network components (Cisco switches, F5 load balancers, Palo Alto and CheckPoint firewalls, iLO boards)
• Deployment and further development of the network scanner JDisc in cooperation with the vendor (Utimaco HSMs, Linux detection)
• Integration of NetBox, JDisc, and cmdbsyncer into the infrastructure using Docker containers
• End-user training: preparation, creation of materials, and delivery
• Creation of data flow and network diagrams
• Population and planning of IPv4/IPv6 with NetBox including VLAN import
• Dual-stack setup of servers and clients with IPv4 and IPv6
• Connection of REST interfaces for Checkmk, JDisc, vSphere, HMC, i-doit, NetBox Software: Confluence, Jira, MS Office 365, Teams, i-doit, NetBox, JDisc, cmdbsyncer, DB Visualizer, vSphere, HMC

• Analysis of requirements and the current situation
• Migration of an old domain structure and Tobit to Exchange 2019 with connection to MS365
• Review of implementation options and planning for the protection of sensitive data
• Planning with regard to BSI Grundschutz, BDSG, and DSGVO
• IT governance and IT security backtests
• Support with ERP setup and securing mail transfer
• Hyper-V 2016/2022, Microsoft Terminal Services Cluster, Microsoft Exchange 2019
• Office 365, Microsoft 365, Azure AD, Teams, Salesforce
• Cisco, Zyxel, and HP switches, Sophos firewalls/UTMs, SecurePoint
• Microsoft IIS 2022, IPv4/IPv6, Veeam, Wortmann Online Backup, NextCloud
• Services: DNS, DHCP, TCP/IP, subnetting, firewalling, routing, VoIP, group policies (GPO), SIEM, remote work, home office, high availability, failover, VLAN, PRTG

• Analysis and optimization of business processes in financial accounting
• Customizing in SAP FI (e.g. company codes, chart of accounts, payments)
• Integration with other modules such as CO, MM, SD
• Consulting on legal requirements (e.g. GoBD, UStG)
• Support with month-end and year-end closing
• Creation of test plans (system test, integration test, UAT)
• Definition of test cases (e.g. postings, payment runs, dunning runs)
• Selection of suitable test data and scenarios
• Manual testing of posting processes (e.g. customer invoice, payment run)
• Validation of automatic postings (e.g. for MM credit memo)
• Checking interfaces (e.g. to subsystems or non-SAP solutions)
• Documentation of defects in the test tool (e.g. Jira, ALM)
• Analysis and feedback to developers or the customizing team
• Retest after bug fixes
• E2E tests with SAP Solution Manager (SOLMAN)
• Use of tools such as SAP CBTA or Micro Focus UFT

• Responsible for the configuration, maintenance, monitoring, troubleshooting, and optimization of the IT infrastructure, including Extreme Networks, SD-WAN, and Fortinet security solutions, at all international company locations in Europe and North America
• Development of a comprehensive strategic roadmap to optimize the network architecture, including VLANS, NAC, QoS, firewall configurations, VPNs, DPI, NGFW, threat intelligence, and SSL/TLS inspection
• Implementation of the OneIT strategy through the introduction of new technologies such as Cisco DNA Center, ExtremeCloud IQ, FortiOS, FortiManager, and FortiAnalyzer, which increased employee skills and the efficiency of the IT systems
• Integration of IT and OT systems to optimize the network and security architecture and improve operational efficiency

• Plan & Prepare (Site Design & Readiness): Inventory & Design: Dell PowerEdge R-Series, Aruba Switches (L2/L3), Notebooks/Peripherals; Serial Numbers/Asset Tags, IPv4/IPv6 Addressing, VLAN/DHCP/DNS Plan

• Runbooks/MOPs: Site Rollout Runbook, Backout Strategy (<15–30 min), Risk Register, Communication Matrix; Approvals via CAB/Change

• Images/Packages: Golden Image (Win10/11), Driver Packs, BIOS/UEFI Baseline; O365/Teams/OneDrive-KFM; BitLocker Policies; MECM/SCCM, Intune/Autopilot, MDT/WinPE

• Logistics: Shipping/Customs Clearance, RMA/DOA, On-Site Spares; Tools (Barcode Scanners, Label Printers), "Go-Bag" (Cables, SFPs, Console Cables)

• Deliver (On-Site Implementation): Endpoints: Swap & Migration (USMT/OneDrive KFM), Peripherals (ATB/BT Printers, Scanners, Boarding Gate HW); Domain Join, Compliance Checks, O365 Activation, Printers/Queues, Network Drives

• Acceptance: Functional Tests for DCS/CUTE/CUPPS/CUSS Stations, Ticketing/Check-in Workflows, Boarding Gates

• Servers (R-Series): Rack & Stack, Cabling (PDU Redundancy, Fiber/Copper), Labeling/Nomenclature; Firmware/RAID (PERC), Lifecycle Controller, iDRAC Network; Windows Server 2022/2025 + CIS/BSI Hardening; Agents (Backup/AV/EDR/Monitoring), Time Service/NTP Auth, Syslog/SNMPv3

• Network (Aruba): VLANs, LACP Trunks, MSTP Root; Portfast + BPDU-Guard at Edge; QoS (EF/AF); Dual-Stack (v4/v6), DHCP Relay. NAC/802.1X with ClearPass/Radius/TACACS+, Roles + MAB Fallback; Guest Isolation, ACLs (Guest→Mgmt deny). Telemetry: sFlow, SNMPv3, Syslog→SIEM; LLDP→Inventory/CMDB

• Airport-Specific: CUTE/CUPPS/CUSS Terminals; DCS/Amadeus/SITA Connectivity; FIDS (read-only); Bag Tag/Boarding Pass Printing; Changes During Off-Peak/Night Windows

• Stabilize (Hypercare): First-Day Support, KPI Tracking (Login Times, Ticket Volume, Error Classes), QoS Fine-Tuning

• Troubleshooting: Wireshark/iperf, Event Logs, Switch Counters, sFlow Flows; Fast Incident Handling as SPOC

• Knowledge Transfer: Short Training Sessions for Station Teams, Mini-Runbooks (Incident/Recovery)

• Close (Documentation & Handover): Documentation & CMDB: Final Configs (Switch/Server), Topology/Patch Plans, IP Tables, Serial Number/Asset Lists, Before/After Photos

• Acceptance & Sign-off: UAT Protocols, Functional Evidence (Use Cases), Return/Reuse of Old Hardware

• Lessons Learned: Risks, Standard Packages, Driver Freeze, "Known Issues"

• Interfaces/Communication: Station IT, Airport IT, SOC/NOC, Ground Ops/Ramp/Check-in, Providers (SITA/Amadeus). ITSM: ServiceNow (Inc/Req/Change/KB), Handover to BAU

• Creation of test concepts
• Requirements management
• Release planning and support
• DDS management
• Reporting (test report, AFO TestMatrix)
• UAT/BAT coordination
• Onboarding of new team members
• Team planning / capacity planning
• Support with documentation
• Methods/tools/technologies: black box, white box, exploratory testing, E2E testing, regression testing, L&P testing, acceptance testing and interface testing, integration and system testing, networking, JIRA with Zephyrscale plug-in, Confluence, RISE Portal, Ethernet, IPv4, IPv6, Linux, VM, Postman, SQL, SQL-Developer, Bruno, Wireshark, cloud, Burp Suite, Notepad++