As NetWallah said, thanks for the speedtest-cli information.

I propose you another solution, even if not intended to measure the whole line speed but the speed of web access, and produces, if told, one line per access. At least you can compare results to further analyze your line degradation. You can find my WebTimeLoad0.23.pl here. You can use -v, -s and -c to bend it at your needs.

#    -c --count    how many times repeat the check. default is 1
#    -s --sleep    seconds between checks. default is 1.
#    -v --verbosity from 0 (one line output for each check) to 3. defa
+ult 1

webTimeLoad23.pl -u www.perlmonks.org -v 0 -c 1000 -s 60
Fri Dec 12 10:15:46 2014        http://www.perlmonks.org        200   
+  116076  2.335208        48.5419 Kb/s
Fri Dec 12 10:16:48 2014        http://www.perlmonks.org        200   
+  116076  1.913632        59.2358 Kb/s
Fri Dec 12 10:17:50 2014        http://www.perlmonks.org        200   
+  116076  1.798926        63.0129 Kb/s
Fri Dec 12 10:18:52 2014        http://www.perlmonks.org        200   
+  116316  1.816933        62.5174 Kb/s
[download]

As side note i found this article about speed tests.
HtH
L*