It loads JavaScript in the web browser and then selects the best server based upon ping and outputs the result. What do we do about this? Go to websites like and begin the test. Additionally, the bwctld processes share the results from their respective sides of the test with each other.We always need to check the speed of the Internet connection at home and office. The results are returned to the client from both sides of the test. Then, the bwctld processes run the test and return the results. Once bwctl is able to get a matching reservation from both bwctld processes (one for each host involved in the test), it confirms the reservation. bwctld either responds with a tentative reservation or a test denied message. Furthermore, it requests when the test should be executed. The bwctl client is used to request the type of throughput test wanted. If the local system is intended to be one of the endpoints of the test, bwctl will detect whether a local bwctld is running and will handle the required server functionality if needed. The client can arrange a test between two servers on two different systems. BWCTL will work as a 3-party application. The bwctl client application works by contacting a bwctld process on the two test endpoint systems. These tests can measure maximum TCP bandwidth, with various tuning options available, or, by doing a UDP test, the delay, jitter, and datagram loss of a network. Reference: Bandwidth Test Controller (BWCTL)īWCTL is a command line client application and a scheduling and policy daemon. Now multiply the bytes rcvd by 8 to get total bits, then divide by the time: Result in this example is 70Mb/s It can be obtained from Source Forge, or it may already be available in your distribution.Īgain we will use one of the machines as a server that receives the data and the other as a client that sends the information. Netcat is described as being a “feature-rich network debugging and exploration tool”. To eliminate the disks from having any part of the transfer, we will use netcat transferring the output of command yes. So using Iperf (with appropriate flags) on both our machines we can simply measure the bandwidth between them. TCP window size: 85.3 KByte (default ) -Ĭlient connecting to 10.1.1.1, TCP port 5001 TCP window size: 8.00 KByte (default ) - local 10.1.1.1 port 1646 connected with 10.6.2.5 port 5001 Interval Transfer Bandwidth TCP window size: 8.00 KByte (default ) - local 10.1.1.1 port 5001 connected with 10.6.2.5 port 54355 Interval Transfer Bandwidth With Iperf you have a server machine where iperf put itself in listening and the other that is the client that send the informations. Iperf uses the different capacities of TCP and UDP to provide statistics about network links. To be clear, the difference between TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) is that TCP use processes to check that the packets are correctly sent to the receiver whereas with UDP the packets are sent without any checks but with the advantage of being quicker than TCP. The bandwidth is measured through TCP tests. – Datagram loss: can be measured with an Iperf UDP test. – Jitter (latency variation): can be measured with an Iperf UDP test. – Latency (response time or RTT): can be measured with the Ping command. The quality of a link can be tested as follows: Iperf reports bandwidth, delay jitter, datagram loss. Iperf allows the tuning of various parameters and UDP characteristics. Iperf was developed by NLANR/DAST as a modern alternative for measuring maximum TCP and UDP bandwidth performance. In this article I will show you 3 way to measure the bandwidth from the command line, without using the disks. Someone use ftp, scp or other file transfer protocols, these can give some indication, but probably you’ll measure the limit of your disks or CPU. But how do you accurately measure the speed between two servers? One element that is often not know, or that should be measured after a problem statement or after a change in the infrastructure is the network.