Bidirectional speed question

Tim Conway conway at
Mon May 24 17:01:14 GMT 2004

I agree with Paul.  It's almost certainly hour WAN link.  My own at home 
often gives sustained downloads in excess of 2Mbps,   This seems to be 
throttled by the cube of the difference between upload speed and 16kbps. 
When I get up to 10kbps up, it's still useable.  At 12, it's like a 21,400 
dialup, at 14, it's like amateur packet radio, and at 15-15.9kbps upload, 
all downloads cease... even name resolution fails.  Sprint Broadband 
Direct is an extreme example, but most home broadband has similar linkage 
between the pipes.  You are likely to actually improve your overall 
performance by throttling the rsync with the --bwlimit= option.  Turn the 
upstream one's speed down to about 70% of its maximum alone, and it should 
leave enough for the downstream to do well.

Tim Conway
Unix System Administration
Contractor - IBM Global Services
conway at

2. Line speed is around 100 kbps but halves when transferring files in 
both directions.

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