Week 15 Lesson Plan Addendum


WAN Design

Very few technicians at the early part of their career will be involved in the design of a new network from the ground up. In most cases, the technician will join a company that already has at least a rudimentary network and probably will find one that has not been optimized for connectivity, throughput, redundancy, or security. Because of this fact, this lesson begins with some considerations that a technician may find useful in that scenario described above.

This is a typical network configuration that a technician may have to deal with on occasion. This lesson is about network design. In order to design a network, many things have to be considered in that design. One thing that needs to be considered is the redundancy of the proposal. To illustrate redundancy, the below diagram is submitted to illustrate how to make changes to increase or create redundancy.

In this example, you should be able to discern that there are several components, which if they fail, would create the loss of the network for many other components. The object then would be to redesign this network to remove or minimize that possibility.

The best way to start in this example is to determine the data path of the packets. (Of course, you should have noticed how easy it is to observe the network components on a map instead of staring at a closet full of cables). Notice the position of the servers and what would happen to the entire network if router 10.10.10.x failed. No one else could access any components on those servers – such as email, applications, files, etc. Are there any other choke points (where data may be confined by limited bandwidth or other factors)?

A good way to begin would be to move the servers to the 20.20.20.x LAN.

Next we would need to create redundant paths through the routers. The resultant redesign should look something like this.

Notice how every device has multiple paths to the servers and to other requirements.

Gathering Requirements

A typical situation for a technician would be to be tasked to design a new network for their employer or client. The first item to be considered when designing a network is to determine the customer requirements. One must find out which applications are required (email, games, applications, chat sessions, net meeting, whatever). These requirements may be determined by various methods but usually the best is observation. Knowledge of the present usage of applications (how the company does business) and what it would like to do is fundamental. Once this is determined, the best method of fulfilling these requirements becomes one of choosing which package (server software) or OS (Novell or TCPIP or APPLE).  This would also include the functionality of certain groups such as finance, engineering, bosses or whatever.

Network Map

Once all the requirements have been gathered, the next step is to draw it out using network mapping software. Here we use VISIO but there are other packages available. A preliminary site map may be prepared but it is usually a very good idea to perform what is called a site survey prior to beginning the map. If you, the technician are unfamiliar with the site, then a site visit is definitely a great idea. You should take along some preliminary ideas and a method of sketching your ideas while there. At the site survey, you will determine cable lengths, closet locations, ducting if required, temperature and climate considerations, physical placement of any racks or cubicles or desk items, lighting requirements, etc.

The result of the site survey will allow you to design a floor plan, determine materials list (amount of cables, lengths of cables, number of connectors, etc), create cabling lists and the resultant labeling scheme, and many other items.

Networking model

Hopefully by now you will have determined the network model you will use. There really isn’t much Novell out there anymore but you may wish to choose between Linux or Mac or Windows servers. The choice will depend on your needs and requirements.

Design the network

The next step is to actually design the network. If the situation presents itself, you may wish to consider different approaches for presentation. If you have to present to higher ups, it is definitely best to offer multiple choices to your bosses. It makes them part of the game. However, you should present them in such a way that will make the bosses choice your preference and make them think it was their idea.

When you begin the design you will have three areas to define. You will need to define the different layers of your network. You will have the core area, the distribution area and the access areas to consider.

The core area defines the interconnectivity between sites (WAN considerations). Is the Internet to be included, etc. are the types of considerations in this area.

The distribution layer will define how to get from this building or floor to that building or floor. This would include such things as wiring closet locations, the physical plant cabling, location of servers, climate control, cable routing, the hard core meat of the presentation, if you will. Data flow is considered at this point, as well as choke points, redundancy and all the other factors affecting how the work is to be accomplished.

The access layer more or less is the security area. Who has access to what and how you are going to separate these groups is the main concern and focus of this definition. Which users connect where and what access they can have, or be restricted from, are all considerations in this area.

This is where the case study comes into play. Using the case study of the Washington school district, we will plan the network according to the requirements of that scenario. I will change that scenario to eliminate some old technology such as token ring but essentially it is the same plan.

To summarize the steps:

Start with requirements list

Create preliminary network map while gathering the necessary site information

Create final network map utilizing all known information

Create budget

Obtain concurrences and then alter network design if necessary

Obtain materials on the list

Build the network

Fine tune the network