A Network of Interest
To help those of you following my articles, I’ll use a slightly modified version of the network diagram from my chain of responsibility article (see "Additional Reading" at the end of this article). The concepts are (I hope) familiar now, but here’s a quick recap anyway! Figure 1illustrates a network that will later help to describe the concept of the command pattern.
Figure 1 A service provider network linking two enterprise sites
Figure 1 shows a geographically dispersed enterprise with sites linked together via an intermediate service provider network. The Network Management System (NMS) at the bottom of Figure 1 is employed to make configuration changes in the network.
In the code section, I’ll simulate the creation and subsequent deletion of an LSP (such as LSP123 in Figure 1) from within the NMS. As a quick reminder, an LSP is a preconfigured forwarding path for network traffic. Individual traffic streams (such as the real-time Internet telephony traffic in Figure 1) can be preferentially pushed into the LSP, whereas the data traffic is forwarded along the conventional shortest path R2-R6-R5.
Being able to direct traffic in this fashion is an important network management procedure called traffic engineering.