How to measure internet connection speed?

Question

linux

Here's an interesting question for you to discuss.
There is a physical server, on the Linux server. It is connected to the Internet. Connected for a reason, but 40GE in a bond (LAGe, bundle, whatever you want to call it) with four 10GE ports. How to check what is the real speed provided by the operator?
If someone writes about iperf , then I will immediately ask you to indicate how much you squeezed the speed on it and with what keys?
According to the condition of the problem, there are no special devices.

Answer 1

Slide "Single flow 40G Results" on page 37.
meetings.internet2.edu/media/medialibrary/2014/04/...

Answer 2

=D if you are alone in the evening switching pictures of girls on the Internet seeing only your eyes ... you have a dial -up
if you have Internet through a telephone .. then you live in a plague, a regular client of Rostelecom and you have adsl
if you have a 10 megabit network .. then you live in an old building area and you have no chance that your provider will change something
100 megabits, alas, and oh, a rarity. but you are a very nervous type. because you do not like at such speeds when you are thrown out of the raid or your crooked right-handed right-hander makes you happy with the absence of the Internet at the weekend.
well, gigabit. optics). you are a Google subscriber and regularly get billed for pirated content