Previous Table of Contents Next

Note that Figure 1.13 is by no means comprehensive. For example, the role of facilities in obtaining power, cooling, and space has not been presented, nor has the process of locating vendors—and the roles that contracts and requests for proposals (RFPs) play in that process—been introduced. Also note that the ordering process has not been included. (This step could easily enter into the flow at any point following the requirements analysis; however, some installations may find that some components must be ordered well in advance.) This flow chart concentrates solely on the technical aspects. Keeping that in mind, let’s examine each step in more detail.

1.  Analyze the network requirements. The requirements analysis process should include a review of the technical (both technology and administrative) components, along with the business needs assessment.
2.  Develop an internetwork structure. Composing a network structure will depend on a number of criteria. The designer will need to first determine if the installation is new or incorporates pre-existing features. It is always easier to build a new system than to add to an existing one. This chapter includes a number of models for designing networks, but for our purposes a simple three-tier model, as shown in Figure 1.14, will suffice.

FIGURE 1.14  The three-tier (hierarchal) network

3.  Configure standards. Once the topology of the network is drafted, an addressing and naming convention will need to be added. This is the phase where consideration must be given to route summarization, subnetting, security, and usability. Figure 1.15 illustrates a simple addressing and naming standard for the three-tier network structure.

FIGURE 1.15  The three-tier network with IP addressing and DNS names

4.  Configure components. This phase presumes that hardware and software have already been selected. For the project to move forward, an order would need to be placed at this phase. The selection and configuration of components should include cabling, backbone, vertical and horizontal wiring, routers, switches, DSU/CSUs (data service units/ channel service units), remote-access services, ISP/Internet providers, and private WAN telecommunication vendors.
5.  Add new features. The flow chart classifies this fifth step as adding new features. This is a bit misleading, as it could include the addition of an entirely new network or of a single protocol. Additional services, including access lists and advanced features, could also be included.
6.  Implement, monitor, and maintain the network. The final step is really a recurrent phase of the network design process. Whether the network is completely new or simply modified, a required step in the project is a review of the initial design requirements, a review of the health of the network, and general administration. Only by reviewing the project (including the nontechnical portions) can a team gain valuable information that will eventually simplify the next effort and identify future needs for the current project.

Designing with a Client

Let’s walk through a simple network design process. Do not be concerned if you are unfamiliar with the specific technologies noted in this scenario—the actual details are unimportant. However, a good designer should always have a list of technologies to research and learn, and you may wish to add the unfamiliar components to your list.

The Sales department has requested a DSL-based solution for their team. One of the senior sales executives has read articles touting the benefits of DSL, which has led to this request. Users will want access to corporate data and the Internet at high speeds. In addition, users may be at home, at a client’s site, or in a hotel. The budget for the project is undefined; however, you are told that there will be funding for whatever it takes.

Stop for a moment and consider the different factors and issues associated with this request. List some of the questions that should be answered.

Here is a short list of preliminary questions:

  How much data will actually be transferred?
  Does the data require security/encryption?
  How often will the user be at home? At a client’s site? At a hotel?
  What protocols are to be used?
  How many users will there be?

Note that some of these questions will not have an answer, or the answer will be vague.

The designer will have to make some interesting decisions at this point. The requirement for high-speed access from client sites and hotels is one issue. DSL requires a pre-installed connection. It is not widely available, unlike POTS (plain old telephone service), and is either configured as private (similar to Frame Relay in which companies share switches and other components, while PVCs keep traffic isolated) or public, which usually connects to an ISP and the Internet. An immediate red flag would be the lack of DSL availability in remote locations. Note that the request specified DSL. Why? Is it because the technology is needed or because it is perceived as newer, better, and faster?

Depending on the answers, it may still make sense to use DSL for the home. However, the design will still fail to address the hotel and customer sites. Perhaps a VPN (Virtual Private Network) solution with POTS, ISDN, and DSL technologies would work. This solution may include outsourcing or partnering with an ISP (Internet Service Provider) in order to implement the design. Note that at no point in the process have routing protocols, hardware components, support, or actual costs been discussed. These factors should be considered once the objectives for the project have been defined.

Network Design in the Real World: Nontechnical Solutions

Network designers should not be afraid to suggest nontechnical solutions in response to requests. For example, consider a request to install a Frame Relay T1 for a connection to another company. There will be a large data transfer every month of approximately 100Mb. The data is not time sensitive, and no additional data is anticipated (i.e., neither the frequency of the data nor the volume of data is expected to increase.)

This problem begs a nontechnical solution, especially since the costs for a technical solution, even for Frame Relay, would be very high. As a variation on SneakerNet, why not propose FedExNet? (SneakerNet was one of the most popular network technologies ever used—users simply walked floppies and files to recipients.) It is important to consider the alternatives—in this case the requirements did not mandate a technical solution, just a solution. A CD-ROM or tape would easily contain the data, and, at current tariffs, the cost would be less than 1/20th the technical solution. It may not appear as glamorous, but it is secure and reliable. Note these last two points when considering an Internet-based solution, which would also be cheaper than private Frame Relay.

This chapter has already touched upon cost as a significant factor in network design, and the majority of these costs are associated with the telecommunications tariff. The tariff is the billing agreement used, and, like home phone service, most providers charge a higher tariff for long-distance and international calls than they do for local ones. Designers should always consider the distance sensitivity and costs associated with their solutions— Frame Relay is typically cheaper than a leased line, for example.

Previous Table of Contents Next