|  |  | Summary

Now that you completed this chapter, you should have a firm understanding of the following: WAN design includes gathering and analyzing requirements such as traffic load and response time. The most scalable design for WAN implementation is a hierarchical model, with each layer performing a particular function. The hierarchical design model consists of core-layer functions, distribution-layer functions, and access-layer functions. Enterprise WANs can be made up of several different WAN technologies, such as Frame Relay and ISDN. Placement of servers is critical for controlling traffic patterns across the WAN.
| Threaded Case Study
Washington Project: WAN Design

In this chapter, you have learned about the WAN design process, so now you can focus on interconnecting all the individual Washington School District sites into a WAN topology that satisfies the users' requirements.

Complete the following tasks:

1. Create a WAN design that includes the following:

> - Create a WAN User Requirements Document focusing on interconnecting all of the individual school sites into a WAN topology that, meets the needs suggested in the TCS Overview, your research, and your Instructor's assignments
> - Document WAN link speeds and upgrade paths
> - Create a model of traffic flow between schools showing a two- or three-layer WAN hierarchy
> - Develop a list of additional equipment, such as CSUs/DSUs (channel service units/data service units) and router interfaces required to implement the district-wide WAN
> - Describe a list of what kind of redundancy is needed to ensure WAN uptime
> - Summarize the benefits of your WAN design

2. Each group should develop an overall WAN topology independent of each other and openly debate the merits of all of the designs. The outcome of this process will be a mutually agreed upon WAN design. Then apply this mutually agreed upon WAN design to your site (all sites).
3. Document all the router commands necessary for reconfiguration of local site access routers in order to implement the WAN design.
4. Document how a WAN implementation affects routing updates between routers.
5. Apply the CCNA Certification Exam Learning Objectives to your specific design. This will require a paragraph on how the learning objectives relate to your design. Learning objectives can be grouped together for the purpose of explanation. In this way, you will be studying for their CCNA Certification Exam as you work through the case study.

CCNA Certification Exam Learning Objectives
(*** are explicit CCNA Exam objectives; unmarked are knowledge assumed by the exam):

General

- Describe the three major characteristics of a Wide Area Network
- Describe what a Regional Bell Operation Company (RBOC) is and what is its function

OSI Model

- Describe which two layers of the OSI model WANs typically address
- Describe what a WAN data link protocol is and what is its functio
- Describe the purpose of DTE and DCE devices and what layer of the OSI model do they apply to
- List four common data link layer WAN protocols

WAN

- Describe what a Point of Presence (POP) and Central Office (CO) are and what is their function
- Describe how Time Division Multiplexing (TDM) works and what WAN technology uses it
- Describe what Customer Premise equipment is
- Describe the data encapsulation process across a WAN link
- Describe connection oriented and connection less services across a WAN
- Describe how WAN signaling standards effect the throughput of Wan services
- Describe what a dedicated leased line is and how it is used
- Describe what packet switched connections are and what WAN services use this technology
- Describe what a hierarchical WAN design model is and what are the major benefits
- Describe the functions of each layer in a three layer hierarchical WAN model
- Describe why server placement and associated traffic patterns are important to understand when designing a WAN

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