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References and Other Sources

Rather than list a number of references in this section, the authors have decided to provide in Appendix C a listing of reference materials, RFCs (requests for comments), and books to augment the development of network design skills. However, even the material placed in Appendix C will quickly become dated. Therefore, it is recommended that readers use the appendix as a preliminary reference point and then continue on with research at the local library or bookstore or on the Internet.

Readers will find the following types of information in Appendix C.

•  Development group Web sites
•  Employment search Web sites
•  Vendor Web sites
•  Relevant RFC numbers

Summary

This chapter presented a great deal of material regarding the theories and models used in network design. This information will serve as the foundation for later chapters, which will introduce more technical material. While later chapters will focus less attention on the business relationships, always keep the importance of these nontechnical factors in mind when considering technical solutions.

Having completed this chapter, readers should:

•  Understand that technology is only one portion of the network design process.
•  Be able to describe the benefits of the three-tier model.
•  Know the definitions of scalability and adaptability.
•  Realize that costs in network design have different meanings and impacts on the business.
•  Understand that most good network designs are a collaborative effort.
•  Know the primary network design issues:
•  What is the problem?
•  What future needs are anticipated?
•  What is the network’s projected lifespan?
•  Be familiar with the considerations of a network design, including those listed below:
•  Excessive broadcasts
•  Media contention
•  Security
•  Addressing
•  Bandwidth
•  New payloads
•  Configuration simplification
•  Protocol scalability
•  Business relationships
•  Know the network design methodology.
•  Be able to define the role of each layer of the three-tier model.
•  Understand the limitations of the three-tier model.

Review Questions

1.  A small, four-location network might use which of the following network designs?
A.  A star topology
B.  A ring topology
C.  A full-mesh topology
D.  A star/mesh topology
E.  A mesh/ring topology
2.  Which of the following are considerations of a good network design?
A.  Security
B.  Control of broadcasts
C.  Bandwidth
D.  Media contention
E.  All of the above
3.  Place the following in chronological order:
A.  Develop an internetwork structure
B.  Analyze the network requirements
C.  Add new features
D.  Implement, monitor, and maintain the network
E.  Configure standards
4.  Why do network designers use the three-tier model?
A.  It lends itself to scalable network designs.
B.  It costs less to implement three-tier networks.
C.  Without three tiers, networks cannot be secured.
D.  Business considerations are impossible to integrate without three tiers.
5.  Which of the following are types of costs?
A.  Recurring
B.  Episodic
C.  Initial
D.  Dollar-cost-averaged
6.  The network core is designed to:
A.  Provide a single point of failure.
B.  Provide a central, reliable, and secure area for the transfer of packets from one region to another.
C.  Use Layer 2 technology only.
D.  Use Layer 3 technology only.
7.  Access lists should not be included in:
A.  The core.
B.  The distribution layer.
C.  The access layer.
D.  All of the above.
8.  When designing DNS domains, which layer lends itself to being the root?
A.  The core
B.  The distribution layer
C.  The access layer
D.  DNS domains do not map to network layers.
9.  Which of the following pieces of information would be important to a network designer at the beginning of the project?
A.  The number of users who will use the network
B.  The amount of data to be transferred and the types of applications that will be involved
C.  The budget for the project
D.  The expected lifespan of the network
E.  All of the above
10.  To implement a full-mesh Frame Relay network for seven locations, the designer would need how many PVCs?
A.  7
B.  6
C.  49
D.  21
11.  A designer is specifically addressing a high percentage of broadcasts as a problem in the network. Which of the following would serve as a solution to this problem?
A.  Switching
B.  Bridging
C.  Routing
D.  Removal of EIGRP
12.  An audit of the network indicates that bandwidth utilization is high on a number of segments. The designer might use which of the following to resolve the problem?
A.  Switching
B.  Increase in bandwidth
C.  Reduction in the number of workstations per segment
D.  All of the above
13.  Access lists might be found at which of the following three-tier model layers?
A.  The core layer
B.  The distribution layer
C.  The access layer
D.  The extranet layer
14.  The 80/20 rule states which of the following?
A.  That 80 percent of the traffic should leave the local subnet.
B.  That 20 percent of the traffic should be in the form of broadcasts.
C.  That 20 percent of the traffic should remain local.
D.  That 20 percent of the traffic should leave the local subnet.
15.  Which of the following would not be included as a good network design criteria?
A.  Low cost
B.  Adaptiveness
C.  VLSM
D.  Scalablility
16.  The network design strives to simplify the move-add-change (MAC) process. Thus, the designer should consider which of the following?
A.  DHCP
B.  Dynamic VLANs
C.  EIGRP
D.  OSPF
17.  Which of the following is the most common trade-off in network design?
A.  Size versus features
B.  Features versus redundancy
C.  Cost versus availability
D.  Future capabilities versus scalability
18.  Please rate the following designs based on their inherent redundancy.
A.  Full mesh
B.  Partial mesh
C.  Hierarchical
D.  Star
19.  Hierarchical networks do NOT include which of the following?
A.  Three tiers divided with Layer 3 devices
B.  Enhanced scalability
C.  Easier troubleshooting
D.  Fewest hops between end points
20.  Based on the model and network characteristics specified in each answer, which would use the greatest number of circuits?
A.  Using the mesh model, the network is fully meshed and contains seven sites and a total of seven routers.
B.  Using the hierarchical model, there are two access layers per distribution layer with two distribution layer routers and one core and a total of seven routers.
C.  Using a ring topology, the network contains seven sites and a total of seven routers.
D.  Using a star (hub-and-spoke) topology, the network contains seven sites and a total of seven routers.

Answers to Review Questions

1.  A, B, C.
2.  E.
3.  B, A, E, C, D.
4.  A.
5.  A, C.
While expenses may appear suddenly, a good design and budget should plan for these as recurring costs.
6.  B.
7.  A.
The core should be used only for the rapid transfer of data.
8.  A.
This question requires a bit of thought, and it is unlikely that it would appear on the exam. The context is that upper layers often can relate to lower layers. While the entire DNS domain could be in all points in the three-tier model, it is likely that the design would break these into subdomains at the distribution tier.
9.  E.
10.  D.
11.  C.
Designers should also consider server and workstation tuning as possible solutions. Recall that Layer 2 does not divide the broadcast domain.
12.  D.
13.  C.
14.  D.
15.  C.
VLSM is typically part of a good network design, but it is not a criteria for a design.
16.  A, B.
17.  C.
Cost is always a limiting factor for the network designer.
18.  A, B, C, D.
19.  D.
A simple hierarchical design would incorporate at least four hops between access layers. A full mesh might keep this number down to one.
20.  A.
The math works as follows: A=21, B=6, C=7, and D=6.


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