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4. Thoughts about performance.

Of course compression/encryption takes CPU time. It turned out that an old Pentium-133 is able to encrypt and compress about 1GB/hour -- that's quite a lot. If you compile SSH with the option "--with-none" you can tell SSH to use no encryption. That saves a little performance. Here is a comprise between several download methods (during the test, a noncompressed 6MB-file was transfered from a 133MHz-Pentium-1 to a 233MHz Pentium2 laptop over a 10MBit ethernet without other load).

+-------------------+--------+----------+-----------+----------------------+
|                   |  FTP   |encrypted |compressed |compressed & encrypted|
+-------------------+--------+----------+-----------+----------------------+
+-------------------+--------+----------+-----------+----------------------+
|   Elapsed Time    | |7.6s  |   26s    |    9s     |          23s         |
+-------------------+--------+----------+-----------+----------------------+
|    Throughput     | 790K/s |  232K/s  |  320K/s   |        264K/s        |
+-------------------+--------+----------+-----------+----------------------+
|Compression Factor |   1    |    1     |    3.8    |          3.8         |
+-------------------+--------+----------+-----------+----------------------+
 

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