Thursday, January 19 2006 @ 05:42 PM EST Contributed by: sde
The Sockets API lets you develop client and server applications that can communicate across a local network or across the world via the Internet. Like any API, you can use the Sockets API in ways that promote high performance -- or inhibit it. This article explores four ways to use the Sockets API to squeeze the greatest performance out your application and to tune the GNU/Linux® environment to achieve the best results.
When you communicate through a TCP socket, the data are chopped into blocks so that they fit within the TCP payload for the given connection. The size of TCP payload depends on several factors (such as the maximum packet size along the path), but these factors are known at connection initiation time. To achieve the best performance, the goal is to fill each packet as much as possible with the available data. When insufficient data exist to fill a payload (otherwise known as the maximum segment size, or MSS), TCP employs the Nagle algorithm to automatically concatenate small buffers into a single segment. Doing so increases the efficiency of the application and reduces overall network congestion by minimizing the number of small packets that are sent.
John Nagle's algorithm works well to minimize small packets by concatenating them into larger ones, but sometimes you simply want the ability to send small packets. A simple example is the telnet application, which allows a user to interact with a remote system, typically through a shell. If the user were required to fill a segment with typed characters before the packet was sent, the experience would be less than desirable.
Another example is the HTTP protocol. Commonly, a client browser makes a small request (an HTTP request message), resulting in a much larger response by the Web server (the Web page).
