I thought a bandwidth is a number represent maximum amount of traffic. But it seems not.
Let me show the Network map in my company.
In this image. WAN has a 155Mbps bandwidth and there are a lot of PC and mobile devices. I tested network benchmark from 6 PCs at the same time.
The result of min download speed is 91.2 Mbps and min upload speed is 88.7 Mbps. For this reason I wonder how this is possible or it works even though WAN has 155 Mbps.
Addition
I used Mbps as mega bit not byte.
It seems I gave you confuse what I want to know. I'm not good at English so It was my best But let me try more to explain specific.
I did't mean why the speed less than 155 Mbps even though the bandwidth of WAN is 155 Mbps.
The thing is how 6 hosts can speed almost 100 Mbps at the same time. WAN is the Internet bandwidth which is ISP(Internet Service Provider) gave our company and that moment may be more than 100 hosts use the Internet when I tested. So How can 100 hosts have speed over than 90 Mbps at the same time even ISP gave us the 155 Mbps for the Internet?
Best Answer
There are many possibilities and substantial further testing is needed to narrow down which ones apply in your case.
One is that the speed test you are using only actually tests for a very short period, so although you think you are testing multiple machines at the same time you are not.
Another is that the speed test is downloading the test file from a cache in your network, not the internet.
Another is that the 155Mbps is not in fact a hard limit but a soft limit which is only enforced after it is exceeded for a sustained period.
Another is that your ISP only enforces the speed cap on traffic it considers "out of network" and there is a speed test server for the site you are using within your ISPs network.
Another is that your ISP simply forgot to set up the limit on your line. ISPs are run by humans who screw up from time to time.
Another is that your ISP is playing the "cheat at speedtests" game and this has resulted in speed test traffic bypassing the limiter.