This is an important metric for the perception of the reliability of a server and the site it serves. Throughput is the measure of the maximum amount of data the server can send through all open connections during a given amount of time the total number of bytes transferred per unit time. The user's experience of a site whose server's bandwidth is less than the demand will be diminished as the per-client throughput lessens to a trickle. When the throughput a server can handle approaches the bandwidth of the network, then the network is saturated and will have to be upgraded for any additional performance to be achieved. Bandwidth is limited by the bottleneck of the carrying capacity of the least capacious link or node of the data pipe.
Response time is a measure of how long it takes the server to service a client request.
A round-trip time of more than a second or two will feel sluggish to the user. Here, too, network conditions can reduce the perceived performance of a Web server. Significant delays occur because the HTTP protocol requires many small-packet round trips, particularly when the network path is congested. Error rate Errors per second is the measure of how many HTTP requests were lost or not handled by a server. The perception of reliability depends on a low error rate.