Robert J. McMahon

Principal Networking, Wireless & Systems Software Engineer

Saratoga, CA | (408) 438-3756 | rjmcmahon@rjmcmahon.com | rjmcmahon.com

PROFESSIONAL SUMMARY

Principal-level engineer and technical founder focused on Wi-Fi, network performance, low-latency systems, and measurement infrastructure. Maintainer of iperf2 since 2014, with multi-million lifetime downloads and industry-wide use for throughput, latency, responsiveness, ECN/L4S, packet loss, jitter, TCP/UDP behavior, and Wi-Fi performance analysis. Deep experience across 802.11 MAC/PHY behavior, transport protocols, multicast, embedded systems, Linux tooling, RF test environments, and statistically valid automation.

CORE STRENGTHS

Wireless / 802.11: MAC/PHY test, EDCA, TXOP, aggregation, retries, MCS, TSF/clock sync, 6 GHz/Wi-Fi 6E, dense MDU and enterprise performance

Network performance: iperf2, latency, jitter, loss, RTT, CWND, retries, CE/ECN/L4S, one-way delay, pacing, responsiveness metrics

Systems software: C, C++, Python, Tcl/SNIT, Bash, Linux, GNU automake, cross-platform builds, event-driven tooling, x86/MIPS assembly

Routing / switching: IPv4/IPv6, TCP/IP, PIM, SSM, multicast, VLANs, spanning tree, ATM LANE, Ethernet, FDDI, Token Ring, Fibre Channel

Automation / lab: RF test rigs, programmable attenuation/phase, nightly regression, statistical process control, scikit-learn, defect triage, Wireshark, git

SELECTED IMPACT

• Maintained and substantially expanded iperf2 since 2014 while preserving compatibility, performance, and cross-platform build behavior.
• Built Broadcom Wi-Fi measurement, latency, and clock-synchronization tooling adopted across multiple business units.
• Presented technical demonstrations to the FCC on 6 GHz low-latency Wi-Fi performance and Wi-Fi/DSRC coexistence using EDCA adaptation.
• Developed multivariate statistical process-control methods for stochastic Wi-Fi performance metrics and regression detection.
• Contributed to Cisco Catalyst 5000 Route Switch Module software, part of a product line associated with approximately $350M in annual revenue.
• Designed FDDI software, protocol decode tooling, and compliance test infrastructure for Space Station Freedom network-interface work delivered to NASA.

PROFESSIONAL EXPERIENCE

Umber Networks - Founder & CTO | Saratoga, CA | 2025 - Present

• Founded and architected Fi-Wi, a centralized wireless architecture using fiber-connected remote radio heads and concentrator-based scheduling to improve indoor Wi-Fi determinism, latency, and observability.
• Defined UAX concentrator/RRH architecture, PCIe-over-fiber fronthaul model, centralized MAC/scheduling boundary, deterministic airtime control, and L4S/ECN-aware queue behavior.
• Built technical and investor materials for semiconductor, concentrator, cable-operator, and standards-oriented partners; received Comcast Innovation Fund support for prototype work.
• Developed a measurement strategy centered on falsifiable 802.11 MAC/PHY metrics: TXOP service time, retry airtime, MCS transitions, aggregation behavior, queueing, airtime debt, and one-way delay.
• Extended iperf2/L4S thinking into wireless telemetry and application-facing measurement, including CE/loss/RTT plus 802.11 state feedback for deterministic control loops.

Broadcom - Senior Principal Software Engineer, Wi-Fi | San Jose / Sunnyvale, CA | 2009 - 2025

• Built low-latency Wi-Fi tooling and clock-sync instrumentation used across business units to measure capacity, delay, jitter, responsiveness, and system behavior under load.
• Developed iperf2 enhancements and Python flow-generation/analysis tools used internally and externally to characterize throughput, latency, jitter, packet loss, TCP behavior, and wireless responsiveness.
• Developed multivariate statistical process control and automated analysis using Python and scikit-learn to detect regressions and validate stochastic Wi-Fi metrics.
• Designed programmable RF environments controlling amplitude and phase for complex Wi-Fi system testing.
• Developed event-driven stream automation in Tcl/SNIT for wireless test engineers, supporting nightly regression and feature validation over many years.
• Collaborated with industry partners on Wi-Fi latency, 6 GHz, coexistence, and performance-measurement problems.

Cisco Systems - QA Engineer, Catalyst 6500 | San Jose, CA | Dec 2004 - Sep 2009

• Performed SQA for IPv4/IPv6 multicast features on Cisco IOS for Catalyst 6500 hardware.
• Tested PIM Sparse Mode, Source Specific Multicast, IPv4/IPv6 multicast, and Multicast NetFlow Accounting.
• Wrote approximately 20K lines of Tcl automation for semi-automated feature and regression testing.
• Created, prioritized, and tracked defects; presented status in weekly cross-functional bug-scrub meetings.

Intoto Incorporated - Application Engineer | Santa Clara, CA | Jun 2004 - Nov 2004

• Supported intrusion-prevention, parental-control, and web-filtering products in technical marketing and field-facing roles.
• Built customer demonstrations, evaluated competitor products, and represented the company at industry trade shows.

Capacitive Networks - Founder | Cupertino, CA | Feb 2000 - Jun 2003

• Founded a broadband startup, recruited an advisory board, and defined early hardware/software product concepts.
• Built an early Linux-based prototype using a server, MPEG-2 decoders, and RF modulators.

Cisco Systems - Software Engineer | San Jose, CA | Mar 1994 - Feb 2000

• Developed embedded/system software for the Cisco Catalyst 5000 Route Switch Module, including data movement between shared memory and the switching bus.
• Contributed to a widely deployed switching/routing product line associated with approximately $350M in annual revenue.
• Developed test scripts for ATM LAN emulation and switching features.

IBM - Software Engineer | Houston, TX | Jan 1990 - Mar 1994

• Designed and developed software for an FDDI Network Interface Adapter for Space Station Freedom.
• Developed FDDI device driver code, SMT protocol decode software, a user interface for an internal FDDI test tool, and automated standards-compliance procedures.
• Evaluated message latency, CPU utilization, and throughput; delivered documented test procedures and results to NASA.

OPEN SOURCE / PUBLIC TECHNICAL WORK

iperf2 Maintainer | 2014 - Present

• Maintains industry-used network performance software in C/C++/Python with GNU automake, cross-platform builds, and performance-sensitive design.
• Added features for enhanced reporting, TCP/UDP performance, responsiveness, one-way delay, histograms, pacing, CE/ECN analysis, UDP load generation, and Wi-Fi-oriented measurement.
• Focuses on statistically valid network measurement rather than single-run benchmark claims.

EDUCATION

Washington University, St. Louis, MO - BS Electrical Engineering, Dec 1989

Austin College, Sherman, TX - BA Mathematics, Jul 1987

COMMUNITY LEADERSHIP

Adult leader, Scouting America/BSA troop: 15 years of volunteer service helping develop independence, community service, and servant leadership; supported 41 Eagle Scouts and 300+ First Class Scouts.