Abstract

Bay Networks (formerly Wellfleet Communications) commissioned The Tolly Group to evaluate the Backbone Concentrator Node version 7.71, with the main focus on measuring maximum multi-segment FDDI throughput for both transparent bridging and IP routing. The project was designed to quantify aggregate frames-per-second performance across multiple concurrent traffic streams and to show how effectively the BCN could scale in high-speed backbone environments using many simultaneous FDDI LAN segments.  

The December 1994 report describes the BCN as a high-capacity platform combining a 1Gbit/s backplane with distributed router processing through multiple Fast Router Engine modules. In the tested configuration shown on page 3, the platform supported as many as 13 FDDI interfaces and additional options for Token Ring, Ethernet, HSSI, Multichannel T1/E1, synchronous serial, and other protocols. The protocol list included IP, OSI, DECnet Phase IV, Novell IPX, Banyan VINES, AppleTalk Phase 2, Xerox XNS, Native Mode LAN, Data Link Switching, transparent bridging, source-route bridging, ATM, Frame Relay, SMDS, X.25, SNMP, and PPP.  

Tolly’s throughput test bed consisted of 12 FDDI LANs, divided into six source LANs and six destination LANs, with six Wandel & Goltermann DA-30 analyzers generating similar traffic streams simultaneously. Each LAN used a DA-30 DAS FDDI module attached to a BCN FDDI DAS interface module through multimode fiber. Engineers recorded the highest throughput both without packet loss and, when higher, with packet loss. In transparent bridging mode, the report states that the BCN could bridge more than 750,000 frames per second. The aggregate-throughput chart on page 1 shows 764,117fps with 55-byte frames, 761,408fps with 64-byte frames, and 539,568fps with 128-byte frames. The utilization chart on page 2 shows 66.2%, 75.1%, and 99.3% FDDI utilization respectively, with 128-byte bridging effectively reaching wire speed.  

In IP-routing mode, Tolly reports that the BCN could route more than 500,000 IP frames per second. The chart on page 2 shows 510,476fps with 54-byte frames, 509,830fps with 63-byte frames, 492,991fps with 127-byte frames, and 280,785fps with 255-byte frames. The corresponding FDDI utilization levels reached 43.6%, 49.6%, 90.1%, and 99.2%, with 255-byte routed traffic also operating essentially at wire speed. Overall, the report presents the Bay Networks Backbone Concentrator Node as an exceptionally high-throughput FDDI switching and routing platform that, at the time of testing, delivered the highest aggregate single-router throughput Tolly had recorded for either transparent bridging or IP routing.