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6 Performance measurements Connected: An Internet Encyclopedia
6 Performance measurements

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6 Performance measurements

6 Performance measurements

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)
CompressDecompress
Sparcstation-1
Sun 4/260
Sun 3/60
Sun 3/50
HP9000/370
HP9000/360
DEC 3100
Vax 780
Vax 750
CCI Tahoe
24
46
90
130
42
68
27
430
800
110
18
20
90
150
33
70
25
300
500
140

Table 3: Compression code timings

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.


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Connected: An Internet Encyclopedia
6 Performance measurements

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