Abstract

Integrating SNA into IP internetworks, an important challenge for many large corporations, is not without peril. Most router vendors now offer Data Link Switching (DLSw), the de facto standard for transporting SNA over IP. Not only must the routers transport SNA reliably across the IP internetwork, they must maintain reliability and adequate throughput under heavy load.

Earlier tests conducted by The Tolly Group and Layland Consulting showed the viability of DLSw in limited tests of both LLC and SDLC traffic (see page 7, “The DLSw Industry Benchmarks”). In the current Industry Benchmark, headquarters site routers from 3Com Corp., Cisco Systems, and IBM Corp. were barraged with live session traffic from over 250 SNA controllers simultaneously running a total of 504 Logical Units (LUs). This test is the most comprehensive multi-vendor test of DLSw ever conducted (see Test Bed, figure 5).

The Results

The products tested performed well under all load conditions. SNA traffic from each controller was forwarded without session loss or router failure. The Tolly Group conducted tests measuring the session performance of 48 to 252 simultaneous SNA Physical Units (PUs) from three branch office routers to a single headquarters site router over WAN links at 56 Kbit/s then T1 speeds, evaluating router lookup table management and congestion response. Close to 1,000 data points were collected, providing total session throughput and response times. When all of the results were tallied and a composite score calculated (see Test Methodology, page 6, for calculation method), the Cisco Systems 4700 ended up on top with a score of 9.51 (see figure 1). The 3Com NETBuilder II turned in a 7.02 and IBM’s 2210 and 6611 followed with a 6.14 and 5.95 respectively.