Performance analysis of a UNIX system based OSI X.25 implementation

The packet-level performance of a Unix-based X.25 network interface for an AT&T computer is described. The interface is compatible with CCITT and ISO 1980/84 link and packet level protocols. The X.25 link and packet level protocols are provided on the intelligent serial controller (ISC) board. Using specific software tools, basic performance data were collected and analyzed, so that a spectrum of performance characteristics would be available for the interface. Throughput, latency, and CPU utilization data were derived. These performance characteristics can be used by network administrators to specify packet size and line speed for specific applications. The results indicate that the AT&T X.25 network interface provides higher throughput at 19.2 kb/s than at 9.6 kb/s, and this higher throughput is sustained over a larger number of virtual circuits. Further, increasing packet size from 128 to 512 bytes provides throughput performance approaching 85% of the line capacity