[CentOS] ssh freezes

All too often, my ssh session will freeze.
I'm fairly certain the problem is at my end.
None of the tilde commands work.
In particular, ~# and ~. are nonfunctional.
I can write to ssh's terminal window from another terminal window.
If I kill the ssh process, I can ssh in again.
The next time it happens,
I will try another ssh session without killing the first one.
dmesg did not show me anything interesting.

Any suggestions on how to diagnose?

-- 
Michael   hennebry at web.cs.ndsu.NoDak.edu
"Sorry but your password must contain an uppercase letter, a number,
a haiku, a gang sign, a heiroglyph, and the blood of a virgin."
                                                              --  someeecards