A second way to improve the web performance is to reduce the time required to retrieve web objects. While the first web servers returned an HTML documents with possibly a few images, today's rich web servers return one HTML document with associated style sheets, javascript code, images, fonts, ... Some of these web objects come from the original server while others are hosted on different servers. Today, a typical web page contains almost 2 MBytes of data on average. The size of the web pages continues to grow according to statistics collected by `httparchive.org`. Web pages targeted to mobile devices are slightly smaller.
To understand the benefits of pipelining, let us consider a simple but illustrative example. A client needs to retrieve 5 web objects that are each 100 bytes. The underlying transport connection has a 1 Gbps bandwidth but a one-way delay of 100 msec. A normal HTTP/1.x client would send the first request, wait 200 msec to receive the answer, then send another request... It would need one entire second to retrieve the five web objects. This is illustrated in the figure below.
