Another bandwidth question

[Pouncer]

Hi guys, I have another question relating bandwidth and transmission.

Say we have a host that has a 1MB file that is to be sent to another host. The file takes 1 sec of CPU time to compress to 50% of its original size, or 2 secs to compress to 40% of its original size.

How would I calculate the bandwidth at which each of the two compression option takes the same total time for compression and transmission

[Al42]

I can't give you an answer off the top of my head (although it's not all that complicated), but the "takes 1 sec of CPU time to compress" and "to 50% of its original size" parts of the situation are not something you're going to know until after the compression is completed, so you'd have to run various compression algorithms (zip has 8) to determine times and compression ratios, then determine which would be best at the available bandwidth.

Another problem is that bandwidth is always larger than thruput. You may have a 3 meg connection leaving your house, but the bandwidth to the other side of town to a different provider might only be 768k at the moment. (And it varies packet by packet.)

The easiest solution is that CPU bandwidth is always going to be larger than internet bandwidth, so compress as much as the other end can decompress. (As a Reductio ad Absurdum, transferring a single byte is VERY fast, regardless of bandwidth or the time it takes to compress and decomnpress.)