An implementation goal of compression code was to arrive at something simple enough to run at ISDN speeds (64Kbps) on a typical 1989 workstation. 64Kbps is a byte every 122us so 120us was (arbitrarily) picked as the target compression/decompression time./45/
|Machine|| Average per-packet |
processing time (us)
| Sparcstation-1 |
As part of the compression code development, a trace-driven exerciser was developed. This was initially used to compare different compression protocol choices then later to test the code on different computer architectures and do regression tests after performance `improvements'. A small modification of this test program resulted in a useful measurement tool./46/ Table 3 shows the result of timing the compression code on all the machines available to the author (times were measured using a mixed telnet/ftp traffic trace). With the exception of the Vax architectures, which suffer from (a) having bytes in the wrong order and (b) a lousy compiler (Unix pcc), all machines essentially met the 120us goal.