Characterizing the existing internetwork
The third step that that is used when following the Top-Down approach is the characterization of the existing internetwork. The information gathered from this step can greatly affect how a design is put together. For example, is the current equipment deployed in the network able to be used in the proposed design or does the proposed design require a complete network device change?
Different pieces of information to be gathered include:
- Existing topology map
- Existing addressing and naming
- Existing wiring
The existing topology map (if it exists) is a nice thing to have when designing an addition to an existing network. From this map, the designer can visualize the changes (if any) that are required to the existing network in order to have it integrate with the new proposed design. Sometimes this means that the existing network is well designed and requires few network changes, and other times it means that the existing network must be bypassed in order to replace it with a better designed network.
The existing addressing and naming of a network can greatly affect how a new proposed design is implemented. It is often required that the existing network address and naming structure be altered in order to improve scalability and modularity.
The advantage of a good existing wiring base is that it can potentially be re-tasked to run newer networking standards. For example, an investment two years ago in a Category 6 UTP wiring infrastructure could greatly reduce the cost of a network upgrade today.
Another issue that has become more important with the deployment of wireless networks is to find out any architectural or environmental constraints that exist within the buildings housing the network. For example, is there an abnormal amount of interference that could affect the way a wireless network can be deployed?
The health of the existing network is also a vital piece of information that is nice to have when designing a network. If the currently used network has certain health issues, these should be found so that they can be addressed as part of the new design. A good way to figure this out is through comparison of existing network baselines and/or performance metrics performed on the existing network. Network metrics should include current availability, bandwidth use, and delay, to name a few.