Network Diagram Overview

A network diagram is, well, worth a thousand words!

A network diagram is essentially a topological map that depicts the network elements and the connections between them. Within the diagram, network elements are illustrated by icons while connections are illustrated as links. Every networking professional should use network diagrams. An up-to-date copy of the network diagram is one of the best troubleshooting weapons in a Netadmin's war chest.

Before creating a network diagram or deciding which software to use to create the diagram, the Netadmin must answer the following questions:

• Topology Will the diagram depict the physical topology or the logical topology of the network?

• File format In what file format does the Netadmin want the diagram to be?

• Features What features of the diagramming software are important to the Netadmin?

Topology

Topology means the study of places. In computer network parlance, topology refers to a network diagram that shows the interconnection of various elements. Based on the network's contents, a network diagram is classified as follows:

• Physical topology As the name suggests, the physical topology shows the physical connections, including the cabling layout. Physical topology often includes chassis details, such as port number, slots, and modules. Because physical topology indicates the cabling layout, logical information about communication links is not shown. For example, the physical topology of both Token Ring and Ethernet networks is a star topology. Rack layouts fall under the category of a physical topology.

• Logical topology Logical topology projects the network layout in accordance with the flow of data within the network. Logical topology also includes virtual LANs (VLAN) and other Layer 2 information, such as Ethernet or Token Ring. Flow charts fall under the category of a logical topology.

File Formats

The file formats for network diagrams depend on the graphic design tools used. Most of the tools, including commercial, shareware, and freeware, use proprietary file formats. Thus, certain tools cannot edit a diagram created by another tool. However, most graphic design tools can export the diagram into common picture formats such as .bmp, .jpeg, .gif, and even .pdf file formats. The JPEG and GIF formats are highly portable and can be viewed in any web browser. On the other hand, editing JPEGs and GIFs is cumbersome at best. A common practice is to maintain the network diagram in a native format and publish JPEGs or PDFs on demand. Another common practice is to save the diagrams as web pages to an intranet web portal.

Features

Any graphic design tool with the capability to draw basic geometric shapes and sizes can be used to create network diagrams. However, certain unique features can help in simplifying the process of creating and editing network diagrams. This section discusses some of these unique requirements.

A good graphic design tool must be able to create network diagrams in a commonly supported format such as JPEG or GIF. As noted in the previous section, even if the original format is different from that of the current software, the program should at least be able to export the final diagram in a common format, such as JPEG, GIF, or PDF. Next, the design tool should be able to add or import various stencils or templates that contain new device icons. The ability to import new icons is essential for incorporating the latest genre of network devices into the diagrams.

Another desired feature is a dynamic connection for joining network icons. Generally, you can connect two icons by a line to depict a network connection. However, when one of the icons is moved, the connecting line must be adjusted accordingly. Dynamic connections overcome this limitation of static connection lines. The dynamic connection points facilitate moving the icons within the diagram by automatically adjusting the connection links. In addition to the dynamic connections, the graphic tool should also be able to resize the diagram according to the paper on which it is printed or the video monitor. This aids in viewing or printing the diagrams.

Finally, the graphic design tool must also be able to add and edit text labels. The text labels provide details such as IP addresses, circuit IDs, serial numbers, model numbers, and so on.

The subsequent sections cover several noncommercial tools that are available for creating network diagrams. Note that creating network diagrams is both an engineering skill and an art. This chapter merely introduces you to some of the tools and discusses how to use them.