Chapter 4

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0
Identifying Application
Impacts on Network
Design
Designing and Supporting Computer Networks – Chapter 4

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
Objectives
 Explain how applications and traffic flow can affect the
design of the network
 Identify application impacts on network design
 Explain how Quality of Service is implemented on the
LAN/WAN
 Explain the options for supporting voice and video
traffic on the network
 Document the network requirements of specific
categories of applications and diagram the application
traffic flows through the network

Explain How Applications and Traffic
Flow Can Affect the Network Design
 Application performance depends on availability and
responsiveness
 Measurement: user satisfaction, throughput, technical
metrics

Four main types of application communication:
 Client-to-client
 Client-to-distributed server
 Client-to-server farm
 Client-to-enterprise edge

Characterize applications by gathering information:
 Organizational output
 Network audit
 Traffic analysis

 Internal traffic: identify areas where high bandwidth is
needed, and possible bottlenecks
 External traffic: determine placement of firewalls and
DMZ networks

 Installed hardware affects application performance
 Choose hardware after analyzing technical
requirements

Identifying Application Impacts on
Network Design
Transaction-processing
applications:
 Additional operations
required
 Immediate response to
user requests
 Redundancy and security
required

Network Design
Real-time streaming applications:
 Minimize latency and jitter
 Infrastructure may need to be upgraded

Network Design
File transfer and email applications:
 Unpredictable bandwidth usage
 Large packet size
 Centralization of file and mail servers in a secure
location
 Redundancy to ensure reliable service

Network Design
HTTP and web traffic:
 Network media
 Redundancy
 Security

Network Design
Microsoft Domain Services:
 Active Directory Services
 Broadcast generation
 Tight integration between ADS, DNS, and DHCP

Explain how Quality of Service is
Implemented on the LAN/WAN
 Capability of a network to provide preferential service to
selected network traffic
 Dedicated bandwidth, controlled jitter and latency, and
reduced packet loss

Implementing traffic queues:
 Identify traffic requirements
 Define traffic classes
 Define QoS policies

Set priorities to manage
traffic:
 Queue type
 Traffic assignment
 Size
 Filter traffic into high,
medium, normal and
low priorities

Where QoS can be implemented to affect traffic flow:
 Layer 2 devices
 Layer 3 devices

Explain the Options for Supporting Voice
and Video Traffic on the Network
Network design implications of converged networking:
 Strong performance
 Security features
 Mandatory use of QoS mechanisms

Network design implications of IP telephony:
 Power and capacity planning
 Identifying contending traffic flows
 Selecting components for the IP telephony solution

Live video:
• Streaming media files
• User sees content before all
packets have arrived
• No need to store large media
files before playing them
• Uses multicast packets to
many users at the same time
Video on Demand:
 Either stream or download
before viewing
 Users can store content and
view later
 Unicast packets to a specific
user requesting the service

Supporting remote workers with voice and video:
 Assess bandwidth requirements for WAN connection
 Permanent link or on-demand

Document the Network Requirements of
Specific Categories of Applications
 Estimate the volume of application traffic during the
initial design phase.
 Document projected applications and associated
hardware in a network diagram.

 Diagram the flow of traffic to and from hosts and
servers within the LAN

 Diagram the flow of traffic to and from remote sites,
including VPN traffic

 Diagram outgoing traffic flows destined for the Internet
gateway and incoming traffic from the Internet to
locally-provided services

 Diagram extranet traffic flows to and from selected
trusted partners, customers, and vendors

Summary
 End users evaluate network performance based on the
availability and responsiveness of their applications.
 The choice of hardware installed on a network can
affect the performance of the applications.
 When adding a new application, the designer must
consider the impact on the performance of existing
applications.
 Voice and video applications present unique
requirements, as they cannot tolerate delays.
 Security and reliability are primary concerns in a
network supporting high volumes of web traffic.
 The primary goal of QoS is to provide priority,
dedicated bandwidth, controlled jitter and latency, and
reduced packet loss.

Chapter 4

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