3KB = 3 kilobytes per second.
1 kilobyte = 8 kilobits (with communications overhead, add another 2 kilobits).
Since it's impossible to actually connect at 56K with a 56K modem (depends on line condition, but 52,000bps is about the best you can do), the best you'll get is about 5KB/s (depending also on what type of data you're transferring).
So, 3KB/s is a little slow, but still reasonable for dialup.
Finally, keep in mind, you might have the fastest connection in the world, but if the source is only transmitting to yo at 3KB/s, that's all you'll ever get.
[Link]