Semester 4
Chapter 3, WAN Design
Study Guide
3.1 WAN Communication
3.1.1 WAN Design Requirements
1. All technologies and features used in WANs are developed to meet the following
design requirements:
 Optimize WAN
 Minimize
 Maximize the effective
to the end users
2. Recently, traditional shared-media networks are being overtaxed because of the
following new network requirements:
 Network usage has
as enterprises utilize client/server,
multimedia, and other applications to enhance productivity.
 The rate of change in application requirements has
and will
continue to do so.
 Applications increasingly require distinct
qualities of service
due to services they provide end users.
 An unprecedented number of
are being established
among offices of all sizes, remote users, mobile users, international sites,
customers/suppliers, and the Internet.
 The explosive growth of corporate intranets and extranets has created a greater
demand for
 The increased use of
servers continues to grow to serve
the business needs of organizations.
3. A
traffic increase is expected in the next five years.
3.1.2 LAN/WAN Integration Issues
4. If a company has relied on its corporate network for business-traffic and wants to
integrate an video-training application, the network must be able to provide guaranteed
QoS (quality of service). This QoS must deliver the multimedia traffic, but does not allow
it to interfere with the
3.2 The First Steps in WAN Design
3.2.1 WAN Design Goals
5. Two primary goals drive WAN design and implementation:


6. In general, WAN design needs to take into account three general factors:



3.2.2 The Gathering Requirements Phase of WAN Design
7. When designing a WAN, you need to start by
business structure and processes.
8. The final network design should reflect the user
about the
.
3.2.3 Analyzing Requirements
9. The following requirements need to be analyzed when designing a network:





3.2.4 WAN Sensitivity Testing
10. From a practical point of view, sensitivity testing involves breaking
and observing what happens.
links
3.3 How to Identify and Select Networking Capabilities
3.3.1 The Use of the OSI Model in WAN Design
11. Hierarchical models for network design allow you to design networks in
12. Hierarchical models for network design also use layers to simplify the tasks required
for
.
13. Modularity in network design allows you to create design elements that can be
as the network grows.
3.3.2 A Hierarchical WAN Design Model
14. Benefits to using a hierarchical model include:






3.3.3 Three Hierarchical WAN Design Layers
15. A hierarchical network design includes the following three layers:



3.3.4 Describe the three-layer Design Model Components
16. The
geographically remote sites.
layer provides fast wide-area connections between
17. The
layer is where the WAN backbone network is found.
18. The
services.
layer provides users with frontline access to network
19. The
layer is where almost all hosts are attached to the network,
including servers of all kinds and user workstations.
20. A three-layer model can meet the needs of most
21. The
networks.
layer is usually a LAN or a group of LANs.
3.3.5 Core-layer Functions
22. The WAN needs
paths so that the network can withstand
individual circuit outages and continue to function. The Core-layer is responsible for
providing these paths.
3.3.6 Distribution-layer Functions
23. The distribution layer provides
connectivity.
3.3.7 Access-layer Functions
24. The access layer allows logical segmentation of the network and grouping of users
based on their
.
25. The main function of the access layer is to isolate
individual workgroup or LAN.
traffic to the
3.3.8 One-layer Network Designs
26. A one-layer design is typically implemented if there are only a few remote locations
in the company, and access to applications is mainly done via the local LAN to the site
file server. Each site is its own
domain.
3.3.9 Two-layer Network Designs
27. In a two-layer design, a WAN link is used to interconnect separate. Inside the site,
multiple LANs may be implemented, with each LAN segment being its own
domain.
3.3.10 The Benefits of Hierarchical WAN Designs
28. Because routers have the ability to determine paths from the source host to
destination hosts based on Layer 3
, data traffic flows up the
hierarchy only as far as it needs to find the destination host.
3.3.11 Server Placement in WANs
29. The placement of servers as it relates to who will be accessing them affects
in the WAN.
3.3.12 Alernatives to Dedicated WAN Links
30. It is not uncommon for remote sites to access the WAN core layer by using WAN
technologies other than dedicated links. Frame Relay and
are two such
alternatives.