2.4 Network - Loosely Coupled

2.4 Network – Loosely Coupled

Each computer in a network has its own operating system, its own memory, and its own I/O subsystem. If there needs to be some communication between software running on one node in a network and software running on another node in the network, there has to be an agreement to accept the coordination and complete the communication. By the way, this notion of ‘accepting the coordination’ is not totally foreign. In the previous section, the kernel mode code had to have been built with requests for simple locks and the raising of an SPL inherent within the code. In effect, this was the kernel code's agreement to accept the coordination. Network coordination and synchronization can be particularly dicey because the operating systems and hardware platforms can vary forming a heterogeneous environment.

Fortunately, most modern operating systems contain TCP/IP software (or other related network software such as Remote Procedure Calls (RPCs)). TCP/IP provides the necessary synchronization (when requested) between processes running on multiple nodes. The cluster software will be intimately involved with the network software and hardware in order to present a single target on the network, or to prepare for network interface failure, or to communicate using Remote Procedure Calls (RPCs).

Figure 2-6 shows a close-up of one system in a network connected with several other systems (each of which consist of similar components).

Figure 2-6: Loosely-Coupled Computers