Operating Systems: Concurrent and Distributed Software Design

3.9. Communications handling within and above an operating system

Figure 3.21 gives an example of how the ISO layers might be provided in a typical operating system.

There are a large number of different protocol hierarchies. Taking a local example, the UNIX systems at the University of Cambridge Computer Laboratory are configured with over 20. It is therefore important for operating systems to allow their clients to select the protocol hierarchy they require. Figure 3.22 shows a commonly used protocol hierarchy in relation to the ISO layers in an Ethernet-based UNIX system. Section 16.4 shows how network communications are set up and used in this system.

Figure 3.22. The ARPA protocols in an Ethernet-based UNIX system.

We have seen the need ...