Internet Core Protocols: The Definitive Guide

Bulk Data Transfer and Error Recovery

Figure 7.40 shows a more-complex TCP session between Greywolf (the Chargen client) and Arachnid (a Chargen server). Greywolf connects to Arachnid and receives several segments of data. Due to a variety of events, this session gets fairly complicated. As such, the discussion is continued in Figure 7.41, Figure 7.42, and Figure 7.43.

Figure 7.40. A Chargen client exchanging data with a Chargen server

Chargen is a simple application that generates streams of character data as soon as a connection is established. Chargen sends the data as a continuous stream, with the stream being broken into segments according to the segment-sizing calculations performed during circuit setup (as described in Section 7.1.5). As such, Chargen is a good example of how TCP handles applications that send large quantities of data.

Figure 7.41. Chargen data exchange, continued

The order of events are as follows:

1. [Segments 0-2] The Chargen client on Greywolf allocates a TCP client port (1048), and establishes a TCP connection with the Chargen server’s well-known port (TCP port 19) on Arachnid.

2. [3-4] Once the circuit is established, the Chargen server on Arachnid immediately starts sending data to the Chargen client on Greywolf. Notice that Arachnid sends two segments, and then ...