Abstract

Siemens Skyport proves that careful design plus strict QoS let a single IP fabric carry both voice and data without compromise.

When the company moved its U.S. headquarters to a new San Jose campus in 2001, it built a fully-redundant Gigabit-Ethernet backbone of Enterasys X-Pedition core routers and Matrix E7 edge switches, segmented voice and data with VLANs, and connected about 1,000 Siemens HiPath IP phones/soft-phones and legacy analog devices through gateways and PoE hubs. The goal was to showcase a real-world blueprint for converged networking and Tolly’s 2002 evaluation confirmed the architecture’s readiness for production traffic  .

Call-quality measurements met or exceeded toll-quality standards even under everyday load.

Laboratory PESQ tests logged a 3.9 score for IP-phone-to-IP-phone calls (threshold ≥ 3.8) and 3.46 for soft-phone calls, while PSQM scores of 1.62 (IP phones) and 1.58 (soft phones) sat well inside the “business-quality” 0-3 band  .

Stress-tests showed why strict priority queuing is mandatory.

With QoS disabled, oversubscribing an egress link to 100 %–120 % of capacity dragged PESQ down to 2.79 and 2.62, well below acceptable voice quality, but enabling the switch’s four-queue, strict-priority scheduler kept scores flat at a near-perfect 3.93 regardless of load  . Voice itself consumes little bandwidth (≈10 Mbit/s for 100 G.711 calls), so prioritizing it lets data bear the brunt of congestion without audible impact .

Overall, Skyport demonstrates that a thoughtfully engineered IP campus featuring redundant links, VLAN segregation, and ASIC-based strict-priority QoS can deliver consistent, toll-quality VoIP while safeguarding mission-critical data, providing a practical template for enterprises embarking on convergence projects.