HTTP: The Definitive Guide

TCP Performance Considerations

Because HTTP is layered directly on TCP, the performance of HTTP transactions depends critically on the performance of the underlying TCP plumbing. This section highlights some significant performance considerations of these TCP connections. By understanding some of the basic performance characteristics of TCP, you’ll better appreciate HTTP’s connection optimization features, and you’ll be able to design and implement higher-performance HTTP applications.

This section requires some understanding of the internal details of the TCP protocol. If you are not interested in (or are comfortable with) the details of TCP performance considerations, feel free to skip ahead to Section 4.3. Because TCP is a complex topic, we can provide only a brief overview of TCP performance here. Refer to Section 4.8 at the end of this chapter for a list of excellent TCP references.

HTTP Transaction Delays

Let’s start our TCP performance tour by reviewing what networking delays occur in the course of an HTTP request. Figure 4-7 depicts the major connect, transfer, and processing delays for an HTTP transaction.

Figure 4-7. Timeline of a serial HTTP transaction

Notice that the transaction processing time can be quite small compared to the time required to set up TCP connections and transfer the request and response messages. Unless the client or server is overloaded or executing ...